texts: Simple capacitive proximity/touch sensor problem

texts:
I've found one simple schematics for capacitive sensor on electronics-project-design.com, and implemented it as follows:

The B? is 9v battery. Sorry for the odd-looking schematics: gschem usability is near zero. And the device is NE555, not LM. The plate is ~10x10 cm aluminium foil. Q1 hFE is over 300, if that matters.

At first, I checked with a 'scope at the Q1 collector and 8k resistor instead of led and smaller resistor. And, wow! the plate worked most of the time  as a proximity sensor.

Then I decide to try with a led (without the 'scope), and the proximity sensing was there no more. (Needless to say, the circuit is not connected to anything, works on battery, build on a breadboard) But then the thing worked even better as touch sensor... Except for I needed to touch the ground T0 to activate. To be honest, when the plate is connected to the ground, touching R1's open end has the same effect, which is reasonable as the body makes a capacitor with the plate.

Thus, the questions:

1) Does this design have any problems if the logic output will be connected to some other circuit? Should I use optocouplers for instance to prevent noise? update: one problem I found after writing this is that when I switch off the table top lamp, the sensor works no more... Is some kind of oscillator needed after all?

2) Is it possible to turn this into proximity sensor (1 cm distance is enough) or does it make sense to go with ICs like QT113 and the like? Will proximity work outside, where there is no low-freq electric lines noise?

I have not yet decided whether the sensor output will just plainly switch
something ON/OFF or whether MCU will be required for more advanced logic. Probably the latter. But for sure there will be two sensors used.

There are so many capacitive sensors design out there, so I chose what seemed simple.


texts: How to choose a replacement DC power connector

texts:
I am making a replacement logic board for my 3D printer, since the original board kersploded and the manufacturer won't replace it as the printer model is 3 years old (...).  The original power supply brick is fine, though, so I want to reuse it, but it has a slightly unusual connector for which I haven't been able to find a suitable female part.

The power supply is a Meanwell GS220A24-R7B, supplying up to 9.2A at 24V, and it has a DIN-style connector that looks like this:
Looking at the bottom-left view, the two left-hand pins are ground, and the two right-hand pins are +24VDC.  I'm not sure whether the sleeve is connected to ground.

This previous answer seems good, but it would be even better if I could just use a barrel connector from my local Radio Shack equivalent, and I'd prefer not to have to buy a new crimp tool.  More importantly, I don't know if there are any considerations in replacing the original four-pin connector with two pins.  Might the two circuits be connected to separate transformer windings or something?  Will it matter if I tie the two 24V lines together?

Basically I'm wary because there must be some reason the manufacturer chose this connector but I have no idea what it was.


texts: Nodal analysis on AC RCL Circuit (I'm confused)

texts:
I  have to calculate the voltage on nodes A,B,C using KCL nodal analysis method. (The two sources work at 60 Hz)

I set the next equations system:

on node A: $$\frac{100\angle 0}{4\angle0} +\frac{VA -VC}{4\angle90°}+\frac{VA - VB}{3.6\angle-33.7°} = 0$$
on node B: $$\frac{VB}{14\angle0}+\frac{VB-VA}{3.6\angle-33.7°}=0$$
on node C: $$\frac{VC}{2\angle90°}+\frac{VC-VA}{4\angle90°}=0$$

I suppose that voltage on Node C is the same of the source connected to it (220V), so the third equations results:
$$200\angle0(\frac{1}{2\angle90°}+\frac{1}{4\angle90°})=\frac{VA}{4\angle90°}$$
then: $$220\angle0°*0.75\angle-90°=\frac{VA}{4\angle90°}$$
hereby:
$$VA = 165\angle-90° * 4\angle90° = 660\angle0 V$$

I think this value is a bit too high. I simulated the circuit with an online page, and the branch of the 10.6mH inductor (wich produces a inductive reactance of j4 Ohm) should have a peak voltage of around 172 V. So I think Im doing something wrong, but I can not make it out.
Could you help me?


texts: What does "no clean" solder actually mean?

texts: I bought some solder that says it doesn't require cleaning. The description specifically says "Eliminates the need and expense of cleaning". But there's still a lot of some substance left on my board that I can't easily clean off. What is this substance? Is it a problem? Is there some way to clean it off besides soap and water?


texts: How can you make a light source brighter?

texts:
I am about to begin to work on an electronics project that involves the output of red light.
   After playing around with a bunch of LED’s, I realize that red and yellow are the weakest as far as “luminous” goes, no matter how much current you drive through the LED.
   How could I make red and yellow more radiant? Like, amplifying the output? I searched “light amplification” and articles about lasers came up, but I’m not sure if that’s what I’m really going for.


texts:
New to electronics and looking to deepen my understanding of things by going through the Art Of Electronics. I've hit figure 2.10B and it's amusing statement:

  "... only ~0.6mA of the 4.4mA collector current comes from R3 - make sure you understand why"

Here I am, asking for a clarification/guidance on whether or not I've understood why.

1) My first thought was. 0.6V is needed on the base of Q3 to turn it in, so if that voltage exists, a current must also exist but couldn't think how to reach 0.6mA from this. Could this thought lead to an answer or am I off course?

2) My second attempt to analyse it was prompted from reading this similar Q&A: PNP Circuit-The Art of Electronics

I decided to view it as a simpler circuit with two voltage sources, where the second is Vcc after deducting the 0.6 for Veb:

Which can be sperated into separate circuits and then the currents solved for each resistor:

This seemed to make sense, with the current over R2 becoming (0.015 - 0.014 = 0.0006 = 0.6mA). This meant that the absense of V2 had a short over R1 so there was no contribution from V1, but this didn't align with the text saying that 0.6mA is contributed by V1.

Am I along the right tracks - and/or have I been clear enough to get some guidance?

Many thanks in advance,


texts: 315 MHz Reciever/Transmitter Raspberry Pi

texts:
I bought a receiver and transmitter (I can't find the link, but it says FS1000A and LR1 315.00 on it).

I also have a set of remote controlled wall outlets that operate on 315MHz according to the FCC website.

I plugged the receiver into a Raspberry Pi, and verified that the receiver was getting power with a multimeter, and sure enough it was getting 5V.

How do I read from the transmitter using the Pi? All of the software I found gives an error after a while, and I have no idea where to start with getting this.

Then, once I have the necessary code for the wall outlets, how do I transmit the code from Python/php?


texts:
Does any one know what is the charger port is for Himo C20 Ebike battery?

I ordered mine it's on its way now I couldn't find the information online.
Also I was wondering if I can add this battery to my Himo C20.

Aliexpress - 36V 20Ah E-Bike Battery 18650 Lithium ion Frog Batteries For 36Volt Bafang 500W BBS02 250W BBS01 TSDZ2

They are both 36 volts but Himo C20 battery is 10ah and this one is 20ah is that gonna be a problem?

Also how do I do it? Should I just connect the second battery's discharge cable the main battery's charge port?


texts:
This video features a circuit that triggers a triac using a DC:
https://www.youtube.com/watch?v=ZXXup79B6Gc

I would like to make a little modification on it it. The video says that I have to connect the "Neutral" of mains to "Negative" of the DC battery, this is a bad restriction for me because I want to connect AC mains at any direction (position), no matter where the hot(live) line is. Any Ideas? Can optoTriac do it?


texts: Need help identifying a 3-pin "Molex" (ish) connector

texts:
I've been trying to figure out what type of connectors these are, so I can get a supply of them. They're 3-pin and fairly compact. I thought they were like the smaller computer fan 3-pin connectors, but those don't fit.

I purchased a digital caliper to take accurate measurements of the pitch etc, but I would prefer to avoid breaking my guitar strings to dig in there and do so at the moment.

I don't think they're real Molex brand connectors, but it's hard to be sure (these are from a guitar builder in Korea).

I've attached a few pictures that should hopefully help with identification. Thanks!

outside width: 8.58mm skinny part, 10.19mm thick

height: 3.84mm, 5.83mm

length: 20.99mm

pins 5mm total width

2.5mm between each pin

~.86mm pin?


texts: Is the resonance frequency actually at the center of the passband of a bandpass filter?

texts:
Assume we have the following circuit

It is a band-pass filter.
There is something I don't get.
We know the the resonance frequency is given by \$ f_{Resonance}=\frac{1}{2\pi\sqrt{LC}} \$ and we know that the lowpass and highpass cutoff frequencies given are given by
$$ f_{1}=\frac{RC+\sqrt{\left(RC\right)^{2}+4LC}}{4\pi LC},\thinspace\thinspace\thinspace\thinspace\thinspace f_{2}=\frac{-RC+\sqrt{\left(RC\right)^{2}+4LC}}{4\pi LC} $$
The bandwidth is given by \$ BW=\frac{1}{2\pi}\frac{R}{L} \$
Now we also know that the resonance frequency is in the middle of the bandwidth. So we are supposed to have:
$$ \begin{cases}
f_{1}=f_{Resonance}+\frac{BW}{2}\\
f_{2}=f_{Resonance}-\frac{BW}{2}
\end{cases} $$
I have built a circuit as described in the picture, up to a change in the value of the resistor. My RLC circuit is the same, but with $ R= 1491 \varOmega $.
But for my values:
$$ f_{Resonance}=\frac{1}{2\pi\sqrt{84\cdot10^{-3}\cdot8.3\cdot10^{-9}}}=6027.558Hz $$
$$ BW=\frac{1}{2\pi}\frac{1491}{84\cdot10^{-3}}=2825 $$
$$ f_{1}=\frac{\left(1491\cdot8.3\cdot10^{-9}\right)+\sqrt{\left(1491\cdot8.3\cdot10^{-9}\right)^{2}+4\cdot84\cdot10^{-3}\cdot8.3\cdot10^{-9}}}{4\pi\cdot84\cdot10^{-3}\cdot8.3\cdot10^{-9}}=7603.349Hz $$
$$ f_{2}=\frac{-\left(1491\cdot8.3\cdot10^{-9}\right)+\sqrt{\left(1491\cdot8.3\cdot10^{-9}\right)^{2}+4\cdot84\cdot10^{-3}\cdot8.3\cdot10^{-9}}}{4\pi\cdot84\cdot10^{-3}\cdot8.3\cdot10^{-9}}=4778.349 $$
$$ f_{Resonance}+\frac{2825}{2}=7440.058Hz\neq7603.349 $$
$$ f_{Resonance}-\frac{2825}{2}=4615.058\neq4778.349 $$
So I get that the resonance frequency is not centered in the bandwitch. What went wrong here?


texts: In an active noise cancellation system, to what form of energy is noise converted and how is the energy produced?


texts: Find error in mathematical proof of electromagnetic fields

texts: This is wrong but I can't figure out what is wrong, could someone help me find the errors.


texts: Role of diodes and capacitors in the voltage regulator

texts:
simulate this circuit – Schematic created using CircuitLab

I have this circuit which is is a Voltage Regulator(the boxes are MC 7812 and MC 7912 and they are voltage Regulators) I would like to ask what is the role of the diodes D1, D2 and the four capacitors (what they do).And one more question, in this circuit i  have as input a dc voltage. What should I add to this circuit so that I have as an input ac voltage 220V at 50 Hz;


texts: Generate PWM signal based on 555 for Meanwell LDD driver

texts:
I am using a Meanwell Led Driver LDD-1000H.
It has a single pin for PWM input for dimming.

I have seen many sketches using the 555 to dim a LED but in these cases the LED was part of the circuit.
How can I design a circuit based on the 555 to generate a PWM output on a single pin?
(Additional question, I don't get how a signal is passed on with a single pin..).

If I want to vary the frequency of the PWMoutput, can I just replace R2 with am adjustable resistor or do I need the two diods as drawn below?

Thanks in advance for your reply..

Thanks very much for your answer.
That would be essentially the following circuit:

Is there a way to get cheaper component as the current and voltage are much lower than those used when the motor is driven like here:

http://www.dprg.org/tutorials/2005-11a/index.html


texts: Confused about the gain effect over cutoff frequency

texts:
I am a bit confused regarding the gain effect over the cutoff of the active low pass filter. While I was checking the AC sweep of an active low pass filter with Gain = 5 and Gain = 10, I noticed that the cutoff is shifted:

I expected the gain to only change but can not figure out why the cutoff is changing as well. Also, should I go to another stage just for gain?


texts:
Im trying to measure temperature using PT100. Im using ADC Pi board for that. ADC Pi uses MCP3424(pdf datasheet) A/D converters, and in datasheet I found how to calculate voltage - it is pretty simple -

Input Voltage =  (Output Code) * LSB/PGA

So i made a simple app which would get the output code, calculate voltage, and from that voltage calculate resistance. But the result was not right. So I searched the sample codes and found out that the calculation is a little bit different -

voltage = float(
            (raw * (self.__lsb / self.__pga)) * 2.448579823702253)

I was not able to find out what the number 2.448579823702253 means... I assume it has something to do with other parts on the board, but i dont really understand electronics so good.

Can someone explain what exactly does it mean?


texts: Astable oscillator with voltage dividers as source voltage?

texts:
This is a part of a larger circuit, which will eventually become an SMPS. I can't even seem to get the oscillator to work. The output of the transformer is 12V

The idea here is to supply each individual component in the circuit. If I only supplied one voltage divider, every time a transistor turned on all the current would be sucked to ground.

Here's a diagram for a circuit I know works...

The only difference I can see here is the bottom resistors forming the voltage dividers. I have to keep the input at 12V to avoid using two transformers; this same transformer will later be split into two channels, one an unregulated linear power supply for some motors, and this SMPS for some sensitive control electronics which change load.


texts: 2N2222 experiment is indicating incorrect gains

texts:
Okay, so I put a 20kΩ resistor between a 5V supply and the base of a 2N2222 with the collector connected directly to the 5V rail and emitter to ground. What I'd expect is that, roughly, 220μA (i.e. (5V-0.6V)/20kΩ) goes into the base and less than 22mA (i.e. 220μA*100) comes out of the emitter. This isn't what happens at all. I tend to get over 45mA coming out of the emitter.

First, I thought it was my resistor precision. I checked and the actual resistor value is 20.2kΩ (0.1Ω resolution).

I thought it might be the specific transistor but I tried two other 2N2222's. The first was from Mouser and the second two from China. All give roughly the same result.

I then thought maybe it was because I'm using a noisy buck converter. I switched to a linear regulator that gives 4.999V stable for several volts over the +1.6V.

I checked the circuit in CircuitLab using the exact values of my configuration and it gives me what you'd expect: 215.0μA in to the base and 23.17mA out of the emitter.

What's going on? Is this happening because I have no load? Is it because I'm doing this on a breadbord? Do I need capacative decoupling/bypass? Or do I seriously have 3 broken/fake transistors where one of them came from Mouser? If so, why are they all giving the same output?

simulate this circuit – Schematic created using CircuitLab


texts: Can't get output from GP5 and GP3 in PIC12F629

texts:
I can't get output from GP5 and GP3 from a PIC12F629 I have. My code is the following:

#include <xc.h>
#define _XTAL_FREQ 20000000
#pragma config WDTE=OFF , BOREN=OFF , PWRTE=ON , MCLRE=OFF , FOSC=INTRCIO

void main(){
TRISIO = 0;
GPIO = 0;
    while(1){
        GPIO = 1b11111;
    }

}

When I connected the resistor and LED to other pins, every LED lights up, except those connected to pin 2 and 4. I verified both the LED and resistor and they are working ok. The MCU is brand new. I even tested this setup with another, used IC before.

What did I do wrong?

Can some one explain what 1b or 0b in GPIO value mean? I guess b could be binary.

Note: My IDE is MPLAB X, XC8.


texts: Why do isolation transformers provide a 0 V between their terminals and grounded instruments and why does a normal grounding not?

texts:
Isolation transformers provide a 0 V between their hot wire and ground. After not understanding why that is, I doubted how earth grounding make a potential difference with me in first place.
First I know that there must some sort of a loop (that's basic) for the current to flow and second the must be a potential difference between two points in that loop.
Well in case you touched a grounded instruments and the live wire of the outlet, ground wire is already shorted with the neutral wire in the main panel so that's a loop. My question now is I don't see any kind of a loop when you for example touch a live wire with barefoot. (I mean the grounding rod is connected outside the house it's unlikely that the resistive path between me and it all the way there is allowing any current to flow.)
To sumup my Question ( May be it's to be considered two questions Actually )

Why Do I get shock When standing on a barefoot while touching a live wire When There's no return path ( at least the way I see it )

And How does isolation transformers prevent shocks when I touch a grounded instruments or with barefoots on the ground


texts: What's the intuition for reading transistor/resistor circuits?

texts:
The below circuit supposedly provides constant current to an LED. I tested using everycircuit.com and that seems correct (used R = 70 ohm for example).
What's a step by step way of thinking about the flow of electrons in such a circuit? How can we tell it would provide constant current for instance?


texts: Why PMOS act like "close switch" when zero voltage

texts:
in PMOS that Vtp less than 0 , from what I understand if We give Vg less than Vtp it has current flow from source to drain ,on the other hand if we give Vg more than Vtp it cut-off.

but in digital Circuit it said "when the control voltage, VC on the gate is zero and is thus more negative with respect to either input terminal (source) or the output terminal (drain), the transistor is “ON” and in its saturation region acting as a closed switch. If the input voltage, VIN is positive and greater than VC current will flow from the source terminal to the drain terminal, that is ID flows out of the drain thus connecting VIN to VOUT."

so that mean we give Vg is zero right? . I confuse PMOS act like close switch when it has Vg is zero or lower than Vtp??


texts:
I've got a component (4 of them), from a Bruel & Kjaer 2803 Two Channel Microphone Power supply -- side note, anyone have a circuit diagram for it, would make life easier to trouble shoot.

The component comes from the 28V pre-amp power supply subsystem, and the four of them are kind of connected in a bridge-rectifier type configuration, but not quite.

It has the marking "ER 21" on it, and a symbol that looks similar to

I'm looking to replace the components, so I need to know what I could replace them with


texts: Stability analysis of cross-coupled amplifier in Cadence

texts:
I am trying to implement a cross coupled amplifier with OP-AMP feedback.
I am not able to get it stable for a square wave however.
The circuit looks as follows:

The OP AMP is ideal from Cadence, all parameters can be tuned. The circuit is unloaded.
The open loop gain, i.e without feedback, Vout/Vin looks as follows:

As it can be seen the gain is negative, which is correct.
Now the closed loop gain from AC analysis with the feedback opamp i.e Vout/Vin* looks as follows:

Looking at the closed loop gain there appears to be a zero at ~10 MHz. I have no idea why, because the open loop gain does not introduce any zeroes.
And the loop gain which is calculated using 'stb analysis' where the loop is broken at 'iprobe' and the loop gain is calculated between the terminals of iprobe.

The loop gain also shows that the phase has been shifted to negative, compared to the phase at DC. Hence the entire amplifier is not stable.
The time domain response looks as follows:
For a sinusoidal input:

For a square wave input:

Now my questions based on the observations above:

Where does the zero come from?
If the closed loop gain and loop gain shows unstable behavior at 10 MHz then the amplifier should oscillate unconditionally, because of negative phase margin. But it does not for a sinusoidal wave and does so for a square wave. Why?
I know some compensation caps need to be added, but where should I add them? Basically how do I go about to make the circuit stable?

Any help will be appreciated.


texts: Effect of an isolation transformer on leakage current

texts:
How do isolation transformers affect the leakage current through protective earth in a system?

Scenario 1: Mains is directly connected to circuit. Metal enclosure has a protective earth connection to building earth. Current passing through earth conductor = I1.

Scenario 2: Line and neutral from mains are isolated from circuitry via an isolation transformer. Earth connection from enclosure to building earth remains as earlier. Current through earth conductor = I2.

I2 < I1. Is this right? Why is this?
The explanation I was given was that its a simple matter of KCL. The current leaving the isolation transformer's secondary line has to return(node current equation) via the secondary neutral and hence the leakage current is lesser(in ideal cases 0).

On the other hand, if the system is powered directly by the mains, the current has the option of returning via the earth wire or the neutral wire as they have a galvanic connection at the mains end.

Firstly, is this right? If it is, then my problem with this explanation is this:

I understand that the leakage current arises because of the coupling between the circuitry and the earth connection, in this case the metal enclosure(which has a earth conductor to the building earth). Now this coupling should solely be decided by the dielectric properties of the material(s) that is separating the circuitry from the enclosure(earth). How will an isolation transformer affect this coupling(and hence the leakage current)? All the isolation transformer can do is to block out common mode noise on the primary to the secondary. So will I1 - I2 = common mode noise? Or am I oversimplifying this?

This is a conceptual question and I'm just trying to understand the basics here.


texts:
Will conductive paint applied to the inside of an ABS case prevent the case from getting electrically charged?
It was suggested to me to use a conductive plastic enclosure to prevent triboelectric charging, but they are not as easy to find in the form factor I want. So for aesthetic and practical reasons I want to paint the inside with conductive paint rather than the outside. Would this work?

Thanks!


texts: LTSpice -Resistor value controlled by on/off Switch

texts:
Is there a way to vary my resistor R4 in picture based on if the switch is on or off?
For example, if S1 is off, I want my R4 value to be 10 Ohms, and if it's on, I want my R4 to be 100 OhmS. And if S2 is on as well, another different R4 value.

Is there a way to do this if/else operation in LTSpice?

Thanks for helping!


texts: Bias analysis in a dual BJT circuit with feedback

texts:
I am building an Wooly Mammoth audio circuit, and I am really interested in finding how and why it works. You can check out and simulate the whole thing here.
I must say I haven't been able to get any valuable result from simulation.

It provides a fuzz distortion effect. In fact, it's based in the well-known Fuzz Face. You may notice Q1's collector and Q2's base common node, as well as the feedback net that connects Q1's base and Q2's emitter. In the article I link to, RG Keen makes an extensive analysis and calls that configuration voltage feedback biasing. Unfortunately, I haven't been able to trace any other data about this.

I have isolated the DC circuit for you:

When trying to solve it, I get stuck at proposing and checking hypothesis: I don't really know whether one or both transistors are in saturation region. I assume that, being this kind of effect, at least one of them is. But I find no way to prove it.

One of the Mammoth's addition to the Fuzz face circuit is the Pinch potentiometer. It seems to change the bias point, while users say it works as some sort of noise gate. I have not been able to see that by simulating.

So I would take a good piece of advice on how to solve the DC circuit (is there a possible analytical approach?) to understand the principles of that bias configuration. Also, I would appreciate some help regarding simulation, as I'm sure there must be something useful to get.

Thank you very much.


texts: Should I buy a diode with higher maximum ratings if it costs the same?

texts:
I need a diode that prevents surge currents from a DC motor flowing back into the power supply.
The motor draws a continuous of 10A at 12V.
Was checking a store for a rectifier diode and found out, that they cost about the same. So why should I not pick the one with the highest maximum ratings?
Also a side question: Can I really pass 10A continuously without cooling?


texts: SDR over DDR memory in FPGA based design

texts:
I am designing a new project which demands the usage of DRAM. I have never interfaced with one before, so my knowledge is rather limited. By analyzing the requirements, it would be sufficient to go with a 128 Mbit capacity running at 100 MHz with a 16 bit transfer per cycle.
By doing the research, I concluded that a SDR DRAM should be my choice for the following reasons:

The controller is simpler to implement (I am aware that there are controllers available and also vendors may provide their own, but I may implement my own for learning purposes)
It is good entry level for DRAM
It does not need dedicated FPGA pins, so more flexibility
The PCB layout is simpler due to the single ended, 50 Ohm impedance traces, versus the differential of the DDR
A 16-bit SDR bus has the same number of traces as the 8 bit DDR, so no saving on this
It uses 3.3V so I don't have to mess with different voltages on the banks (vs the SSTL of DDR)
A SDR is cheaper than DDR
Power consumption is lower in DDR, but the SDR consumption is not prohibitive or excessive

Now, based on the above, is there a major reason which I am not aware and have not considered that I should prefer going with DDR instead?


texts:
Lately, I've heard about a fascinating new technology called DNA Origami, where incredibly tiny machines are folded out of DNA. Using CAD software they are able to build all sorts of interesting things, not the least of which are floating robots small enough to deliver drugs to specific cells, upon receiving a radio signal.

There is a talk about these robots up on youtube.

That got me to wonder, what is the size limitation on building radio transmitters? What factors constrain their size? And could one be built that was the size of a cell? Would it be able to communicate outside the body?

I'd really like to learn more about this!


texts:
I need to monitor if a CPAP mask is leaking air, and where such leak is.

The monitoring will be the whole night receiving info from the sensor(s) and registering it into a raspberry pi.
Is there any sensor that can detect it?


texts: A good way of providing 9V/5V voltage with batteries when current draw is relatively high?

texts:
I have a project (doorlock) with MCU / LCD / Keypad and solenoid (lock) connected together. MCU, LCD and Keypad runs at 5V while solenoid runs at 9V.

I'd like to provide the power with a battery, so I was initially thinking about getting a 9V battery to provide power to the solenoid, and use a LM7805 regulator to provide 5V to MCU, LCD and Keypad. Problem is, on idle, the 5V components draw about 100-130mA of current and the solenoid will draw about 500mA on activation (for about 5 seconds), so that's 630mA of current being drawn. I imagine the battery will get either extremely hot or limit the current.

What's a good strategy of providing a consistent 9V/5V voltage with a high current while minimizing the battery size? Something like a car battery may work here but they are way too large to fit in the box.

Edit: The components are normally powered by AC/DC wall adapter. I'm trying to make a battery backup system pretty similar to shown here (http://www.electroschematics.com/6279/battery-backup-circuit/), so that the doorlock is kept in operation if the AC power dies out for whatever reason.


texts: Why is there an inductor in this power supply circuit for SAM3X MCU?

texts:
I am working on a senior design project and am trying to embed an ATSAM3X8E (Here is the Application Sheet PDF) micro-controller into a system my team is designing. What is the pourpose of incorperating an inductor into the VDDUTMI (USB 3-3.6V input) and the VDDANA (for ADC and DAC supplies) ? I konw as a senior I should probably know this, but a little help is welcome.

Also, for the number 2 red circle, is that a symbol for a polarized capacitor? I am not used to this representation.

EDIT: Also, why is there no value for the resistor?? What does 1R mean?

(This above schematic can be found on page 4 of the application note file.)


texts:
I have been reading about the working of transformers at "no load" condition, that is when no load is connected to secondary side of the transformer. I don't understand why the transformer still draws a little current called "no load current." I read about it on different websites and in books and found that it is to set up magnetic flux in the system.

Does drawing the current make the system stable or anything else, mustn't there be a requirement just like water has to go down a hill so that it can lower its potential energy?


texts:
Can anyone tell me which type of pins are on the picture
and ? I would like to use the same type o connector for my pcb project but with less pins. 10 in my case


texts: Is there different Motor Drivers available for Permanent Magnet DC Motor and Wound Rotor DC Motor .Specifically for Series and Parallel wound DC Motor .


texts: Circuits in audio amplifiers to protect speakers

texts:
I hear that there are at least two kinds of circuits in modern audio amplifiers solely for the purpose of protecting the speakers against excessive loads on powering on and off.

Particular function of these circuits is delaying the connecting of speakers so long that there is reasonable probability of the amplifier to have become stabilised on powering on; and disconnecting the speakers prior to powering the amp off.

The effect is that neither on powering on or on powering the amp off the speakers produce a loud pop or boom, as the simpler older amps used to do.

My question is how exactly are these circuits called and what is their typical setup.

Background: I have two Behringer EPQ304's, and one of them always pops on powering off, and my googling produced little insight so far. English is my second language, so perhaps I've missed the proper names. But I'm interested in the design as well.


texts: Advice for P-Channel Mosfet in Depletion Mode

texts: i want to be able turn off a led with a mosfet and a pushbutton. In order to do this i want the led to be in off state when voltage is applied to the gate of the mosfet. After researching for a while i found out that i probably need a p-channel mosfet in depletion mode for this task. When somebody could give an advice which Mosfet Model i could use for this purpose,  i would be very thankful.


texts: Replacing tantalum capacitor with ceramic capacitor for Op Amps

texts:
I am trying to build non-inverting amplifier with certain op amp; THS3491

The datasheet is linked below.

http://www.ti.com/lit/ds/symlink/ths3491.pdf

On page 25, there is non-inverting configuration diagram.

And on page 35, there is guideline for decoupling capacitors

It says "Use larger tantalum decoupling capacitors (with a value of 6.8uF or more) that are effective at lower freqeuncies..."

I had such bad experience with tantalum capacitors, so I wanted to avoid using these.

Is it okay to replace tantalum capacitors with ceramic ones?

Searching over the StackExchange, I found several pages with similar problem;

Tantalum capacitors vs. ceramic capacitors

MLCC vs Tantalum: For Decoupling, input to regulator and ripple reduction

The answer was that it is okay to use ceramic, but not so sure because I am dealing with Op Amps. I searched more;

http://www.dataweek.co.za/news.aspx?pklnewsid=27008

In above website, they recommend to use ceramic over tantalum, since ceramic capacitors have more advantages over tantalum.

But, is it okay to replace tantalum with ceramic capacitors?


texts: High-speed Network Link between two Processors without Cable

texts:
My goal is to set up a high-speed network link between two identical processors (Qualcomm SOMs) that will be present on the same PCB. Since I have severe restrictions on weight I cannot use the standard ethernet way with an RJ45 and a cable to set this up. The two possible interfaces on the processors for the network link are PCIe 3.0 or a USB 3.1 GEN2 interface.
My current idea is to use an ethernet bridge IC like the LAN7430 from microchip at the PCIe-port on both processors and add a single ethernet transformer (e.g. H5084NL from pulse electronics) in between. This would set up an ethernet link 1000BASE-T between the two processors. According to this and this question the magnetics are recommended to provide a stable connection. They also mention the problem with connections that are shorter than 1m, which I don't know yet how to solve.
Is this the best solution for this problem? Since I do not have access to a MAC-port I cannot implement the direct MAC to MAC connection as proposed by user dim in this question.
With this solution, using the PCIe port, I could achieve 1Gbit/s with the 1000BASE-T Ethernet. According to the USB specifications, the USB 3.1 GEN2 interface is capable of achieving up to 10 Gbit/s, which would be preferable for my application.
Is it possible to implement a reliable USB network onboard without cable? I was thinking about creating a USB-C to USB-C connection, without the actual USB-C plug and cable. I'm talking about USB-C because it can support dual-role, which is needed to set up a network connection as described here.
Finally, I could also add a USB to Ethernet Bridge IC like the LAN7800 but unfortunately I have only found ICs supporting up to 1Gbit/s, even though USB 3.1 GEN2 is capable of 10Gbit/s.
Is the USB-network solution feasible and reliable? And are there known implementations out there?
If I'm going with the ethernet route, are there any advantages using PCIe over USB, or vice-versa?


texts: Digital Potentiometer AD5263 (AD5263BRUZ20) Query

texts:
I am planning to use DigiPot AD5263BRUZ20  ( Digital Potentiometer  IC Quad 8-Bit I2C) in my H/W setup for gain setting. Earlier it has 4 potentiometer in design (not digital pot), now I want to replace it with Digipot. Each digipot (out of 4) will be having different resistance value and need to be there all time.

I never used DigiPot earlier, so has some basic queries as below:

1) Does AD5263BRUZ20 has independent pot settings?

2) Since digital lines for all pots are same, will all 4 pot's will be active same time with different resistance value?

Thanks in advance.


texts: How to calculate the gain of a BJT Differential Amplifier (Long Tailed Pair)

texts:
I'm currently reading Designing Audio Power Amplifiers by Bob Cordell. After seeing the "Basic 50W Amplifier" that he shows in the beginning of chapter 2, I now am trying to use the same building blocks to design an amp to specifications I've chosen to help me understand things.

I've chosen an output power of 5W through an 8ohm load (Which should at least be audible I hope), this means I am going to need a peak output voltage of about 9V. I'm assuming my input signal is coming from something like a phone, and I'm making an educated guess that its peak voltage is 1v. This means I'm going to need a total gain of about 9.

The building blocks of his circuit are as follows:

Stage 1 of 3 (Input Amplification Stage): Constant Current Driven Differential Long Tailed Pair

Rejects noise well, and negative feedback is easy to achieve from the final output of the amplifier with a simple voltage divider

Stage 2 of 3 (Voltage Amplification Stage): Constant Current Driven Common Emitter Amplifier

Easy to get a really high gain from what I understand

Stage 3 of 3 (Output Amplification Stage): Triple Emitter Follower

High input impedance, with a decent amount of output capability.

This is basically an op-amp I think, but with higher power capabilities. What I'm really struggling with is the input stage.

What I've been taught in my Electronics 1 class so far about BJTs is that for these amplifier configurations, the gain usually is a ratio of the resistors used (and maybe includes the base-emitter resistance). I have no idea where the gain is coming from in this schematic. I basically just fiddled with the resistor values until I got an output that looked alright-ish.

Is a source out there that goes through the design process of this type of configuration, or can anyone can help me out? Thanks!


texts:
I'm a hobbyist just discovering logic gates and would like to know, is there a logic gate that will only output a 1 when a is a 1 and b is a 0?

Truth Table

a | b | y
---------
0 | 0 | 0
0 | 1 | 0
1 | 0 | 1
1 | 1 | 0

Here is a schematic I made, that I think should work in theory, but would like it in one package.

Are chips like this readily available or is everything made up of individual gates?

OFF TOPIC EDIT:
IMGUR is currently not working with SE for me or for people in the comments so the way I got around that was to go imgur.com and uploaded the picture manually. Then right click the picture > Copy image address and then paste it here like so:

![logic](https://i.imgur.com/4OqbUN4l.png)


texts:
I'm wiring an MPU 9250 in an SPI bus, and according to datasheet, the same pin as I2C SDA is SPI SDI:

Which leads me to think that since this is Data Input in the slave (MPU9250), would be equivalent to MOSI.

Wiring diagram in the datasheet seems to confirm this:

However, I was reading the SPI page on wikipedia (Ok, not the greatest source) and it says:

  The MOSI/MISO convention requires that, on devices using the alternate names, SDI on the master be connected to SDI on the slave

Which confused me a bit. In the diagram, SDI is wired with SDO and naming is relative to the device the pin is in, which contradicts wikipedia (SDI naming is always relative to the master).

So, in essence, is the Wikipedia article wrong? Can I trust my assumption that SDI on the MPU = MOSI?


texts: Symbol with FB1&2 , meaning and where can I source it?

texts:
I came across this on a schematic and I'm not 100% sure what its function is.

On the BOM it has a resistor package, denoted like this
FB1, FB2 FB_0 RES 1206 (755-4709) RS CODE (I tried looking this up on RS and got nothing.)

Just from FB I would guess it's a ferrite bead.


texts: mobile battery charging using voltage regulator?

texts:
Circuit shown at http://www.instructables.com/id/9v-USB-charger/
will that satisfy all condition of mobile charging through usb ?
what is advantage of circuit shown at http://electronicsproject.org/mobile-cellphone-charger/ over above ckt


texts: (off-state output terminal voltage) in optocouplers ,Vce max of a BJT, Vds max of a MOS

texts:
--I am a hobbyist, not an engineer.

--I was looking in some datasheets about optocouplers and i cross over this part "off-state output terminal voltage”. I google it and i was redirected to this website and one of its questions about this subject. >> here is the thread: What does "off-state output terminal voltage" in optocouplers mean?

--I want to know more about what Damien said: "the maximum voltage you can have across the detector pin when it's turned off. It is equivalent to the Vce max of a BJT or Vds max of a MOS. "

--In my mind, I imagine it's about the voltage spike. When the voltage applied spikes to 600V, the component can not be damaged when is NOT active, NOT coupled, NOT working.
And what is happening when is turned on? (when the component IS working?)
What is the difference between turned off and turned on? I mean, that voltage, 600V should be allowed to cross when is turned ON. And not when the junction is turned OFF/innactive.
It's how i understand it. Please make some light for me. And thank you!


texts: I have 2 Arduino programs that work separately. How can I merge them?

texts:
Program 1
2 red LEDs & 1 green LED are high for 4 seconds then low for 4 seconds.  Red is then high for 4 seconds then low for 4 seconds then it repeats.
int  LedR = 10;
int  LedG = 11;

void setup() {
// put your setup code here, to run once:
pinMode (LedR, OUTPUT);
pinMode (LedG, OUTPUT);
}

void loop() {
// put your main code here, to run repeatedly:
digitalWrite (LedG, HIGH); //Light Greed Led
delay (4000); //delay 4s

digitalWrite(LedG, LOW);//Low Greed Led

delay (4000); //delay 4s

digitalWrite(LedR, HIGH);//Light Red Led

delay (4000); //delay 4s

digitalWrite (LedR, LOW); //Low Greed Led
delay (4000); //delay 4s`

}

Program 2
Servo rotates 20 degrees waits for 4 seconds the returns to 0 degrees waits for 4 seconds then repeats.
#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

int pos = 0;    // variable to store the servo position

void setup() {
myservo.attach(9);  // attaches the servo on pin 9 to the servo object

}

void loop() {

delay(4000);

for (pos = 0; pos <= 20; pos += 1) { // goes from 0 degrees to 180 degrees
// in steps of 1 degree
myservo.write(pos);              // tell servo to go to position in variable 'pos'
delay(15);                       // waits 15ms for the servo to reach the position
}delay(4000);

for (pos = 20; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
myservo.write(pos);              // tell servo to go to position in variable 'pos'
delay(15);                       // waits 15ms for the servo to reach the position

}
}

Both programs work independently but are impossible to integrate as the Arduino does not allow multiple loops.
I have tried to learn the millis function unsuccessfully.
Is there anyway to get the LEDs to light consecutively at the same time the servo rotates?
Please assist me. This is the code that does not work:
#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

int pos = 0;    // variable to store the servo position
int  LedR = 10;
  int  LedG = 11;

void setup() {
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  pinMode (LedR,OUTPUT);
pinMode (LedG,OUTPUT);

}

void loop() {

  digitalWrite (LedG, HIGH); //Light Greed Led
delay (4000); //delay 4s

digitalWrite(LedG, LOW);//Low Greed Led

delay (4000); //delay 4s

digitalWrite(LedR, HIGH);//Light Red Led

delay (4000); //delay 4s

digitalWrite (LedR, LOW); //Low Greed Led

delay (4000); //delay 4s

  delay(4000);


texts:
I am using the LTC6090 op-amp (links to datasheet) to generate a high voltage, low current voltage.

However I've never really done anything regarding DC voltages this high before, so I was wondering which of these power supply solutions were better to provide the ±70 .

My plan was to buy a 140V DC power
supply
and use a voltage divider with high voltage resistors of 500k and
tying the middle to ground.
The second option was to buy two 70V supplies and tying them together. Wiring the middle to ground.

My reason for chossing the first one was because I can't be certain the power supplies are even designed to be tied together like that. But I have never done this before so I thought I would ask this question to learn why doing it one way is better than the other, because in all honestly I'm not too sure.

I've done this before for batteries and low voltage supplies, does anything change when you go to ±70 or greater? Or is it you just need to make sure the voltage ratings of all your components are suitable and that's all you need to worry about?


texts: What is the difference between load testing and discharging a LiPo?

texts:
I would like to test max discharge rates for 1S (200 mAh) LiPo's. But I can see three ways of doing it:

Using a charger, discharge at highest rate and see how high the battery goes.
Using a resistor (0.25 Ohm) and measuring the voltage and amperage. (0.25 Ohm would generate 17.4 amps, which is a bit higher than the maximum expected amperage).
Using a motor and normal load, and measuring voltage and amperage.

What are the differences between these methods? Will they all expose the max discharge rate?

I would like to use method #1 since it is the simplest.

Any relevant links or references would be appreciated.

EDIT: From the comments I see that we need a distinction between burst and sustained discharge rates. For my use case, I am most interested in the burst rate.

Perhaps a good approach would be to connect it to a 0.25 Ohm resistor for 5 sec and measure the result...?


texts: Does a helicopter battery drain when it is "off" but attached to a battery hot bus?

texts:
I'm reading about the DC Power System for a civilian helicopter.
It shows the following diagram for when the battery is off:

However, it shows that the battery hot bus will still be energized.

I assume the battery hot bus is grounded completing the circuit.
Doesn't this mean the battery would be draining with the helicopter off?

What is the purpose of a battery hot bus, and how does it affect the battery?


texts: Random output when reading AVR UART transmission

texts:
I'm trying to learn how to use the USART interface on an Atmega328p.
For now, I just try to send a 'c' character bytes every 500 ms and read it on my computer using a PL2303 USB-serie TTL converter.

Data are transmitted, but I don't get the result I want on the receiving side.

Here is what I have programmed in my microcontroller:

#define BAUDRATE 9600
#define BAUD (((F_CPU / (BAUDRATE * 16UL))) - 1)

void uart_init()
{
  UBRR0 = BAUD;

  /* 8 data bites, no parity, one stop bit */
  UCSR0C |= _BV(UCSZ01) | _BV(UCSZ00);
  /* Enable UART input and output */
  UCSR0B |= _BV(RXEN0) | _BV(TXEN0);
}

int main()
{
  uart_init();

  for (;;)
  {
    while ((UCSR0A & _BV(UDRE0)) == 0);
    UDR0 = 'c';
    _delay_ms(500);
  }
}

I read the data in python using pyserial:

import serial

with serial.Serial(
        '/dev/ttyUSB0',
        baudrate=9600,
        bytesize=serial.EIGHTBITS,
        parity=serial.PARITY_NONE) as port:
    while True:
        print(port.read())

I somehow have the correct result. I have some correct bytes 'c', but about one of two is '\xe3':

b'\xe3'
b'c'
b'\xe3'
b'c'
b'\xe3'
b'\xe3'
b'\xe3'
b'c'
b'c'
b'c'
b'\xe3'

It seems that I have a random high order byte that appears from time to time.

I can't manage to find where is my problem. I check on the scope, and the data sent are always the same.
So I think I have something wrong on the receiving side. But can't find what it can be.
I have double checked F_CPU, which is at 1Mhz.


texts: Where to connect the VNA during matching network tuning

texts:
I'm trying to design the matching network between an antenna and its transmitter, running at 868MHz, as shown below. There's probably about 20mm between the transmitter output and the Pi network.

When connecting the VNA to the PCB in order to measure the impedance, where should the VNA be connected? At the transmitter end, or at the start of the Pi network?

My understanding was that in order for the VNA to "see" the load how the transmitter sees it, the VNA should ideally be connected close to the output of the transmitter (in my case, I have a blank PCB, so I've soldered a UFL connector directly on the transmitter output pad). However, after reading this article by Tektronix, it states the following:

  it’s important to keep in mind that the impedance to be matched must be measured at the point where the matching network will be placed.

I understood this to mean that I should solder the UFL connector close to C13 in the image above (and possible cut the trace between the transmitter and the UFL connector).


texts: Manufacturing a device from off-the-shelf components

texts:
I pursue an experimental project that comprises the development of a car GPS navigation unit and software for it.

We develop and test the software on a working laptop-based prototype which has a USB-GPS (mouse GPS) connected to it. So far this setup has been satisfactory for our development needs.

We planned to assemble a beta-prototype based on a small micro-PC with attached peripheral devices (touch-screen, USB-GPS, etc.) to achieve something like this

But recently I started to think about assembling the whole system into one body which is integrated with a touch-display, like it is done with a regular car GPS devices.

However, I do not know where to start. I do not need any custom PCBs, so the other answers on StackExchange are not quite relevant (they are relevant to custom-designed devices like Pebble or AlarmClock, or Oculus Rift)

Instead, I am only interested in putting a small PC-compatible computer and a GPS unit inside a simple touch-screen body. Is that actually possible?

are there any ready-made device bodies that can be purchased?
is it possible to avoid any custom-designed fabs and just assemble such a device from off-the-shelf components?


texts:
I have a data-logger project that needs to run from a 3-cell Lithium Polymer battery.  It has 5v and 3.3v regulators to provide regulated power to the system.

I want to build the battery into the device so that it is all self contained.  When the user plugs in the USB cable to download the data, I also want the battery to charge from the USB.

So I'm looking for a chip / circuit that can take the 5v USB as an input and boost it to the voltage (12.6?) necessary to charge the 3S lipo, and manage the charge.  The system still needs to operate while charging.  When USB is unplugged the system should run from the battery.


texts: Digitized Voice over piezoelectric speaker

texts:
My objective is too implement a security system that is triggered when someone breaks the IR beam. This IR beam has a digital output pin. Which goes high (5V) when the beam is broken. This signal then goes to an ATMEGA328 microcontroller.

My question is once the Atmega 328 receives the high input from the IR beam, I would like to know if there's a way in which I can make the piezoelectric speaker (powered from 5V) output a phrase instead of just making the normal buzzing sound. The phrase will be something like "intruder detected".

Can I digitize this phrase using the atmega328 and then output straight to the piezoelectric speaker?


texts: Voltage source connected to a MOSFET source

texts:
This circuit

simulate this circuit – Schematic created using CircuitLab

where M1 is an n-channel MOSFET, is said to be incorrect. If the voltage Vin should be imposed to the source terminal of the transistor, the circuit should be

simulate this circuit

1) Why the second configuration is the only one correct? That is, why is it necessary to impose both the current and the voltage at that node?

The presence of a Vin will change the Vgs of the MOSFET; the new drain current (if the MOSFET is still on) will flow across the Vin. Nothing seems wrong to me.

2) And (assuming that Vin is a small signal voltage source) why is the capacitor C inserted?


texts: What decides that an IC will be able to sink or source current?

texts:
Correct me if I am wrong but so far, I've learnt that some ICs can source current while some can only sink (open-collector) while others can do both. And it is decided by looking at the datasheet, Ioh and Iol readings, which should be in mA values to glow an LED. But I sense I'm wrong since an LED should not be the only factor to decide sink/source concept.
To add, Ioh and Iol can be of different values (like one in uA while other in mA), so it is not related to heat generated in the IC since heat generated is directly related to current in the IC.
So my question is, what actually decides whether an IC will be able to sink or source while Voltage outputs for low and high states are similar for all of them! So what exactly decides whether the current will be uA even when output is high or in mA even when output is low?

[edit]We say that the IC is an open-collector, so even when the output is HIGH voltage output, it wont be able to source since Ioh will be in uA (like in case of 7489 RAM). So, what exactly decided this uA current while current should be related to external load resistance attached to output which is in our control. What exactly limits this current to uA? It should not be heat since in case of LOW state, current is in mA, which should actually burn the IC if we go by logic of heat for uA current in high state.


texts: What would an Electrical Engineer do at a Copper Fab business?

texts:
I am going to interview soon at a Copper Fab business. They found my resume and called me for an interview later this week. He said that there might be some synergy between his business and electrical engineering. (About 80% of the copper components he produces are used in electrical components such as electrical motors.)

In what ways can an Electrical Engineer help at this copper fab company?


texts:
Recently, I am doing the flyback, when I design the control stage I have some questions:
This is the optocoupler(PC817) I used and this figure is Current Transfer Ratio vs. Forward Current. There are my questions:
1.) How to decide the CTR value, because the forward current will change when the circuit is in the closed-loop control.
2.)This curve has two slews positive slew and negative slew, which one is the best to decide.

3.) How to decide the RL value, the minimum current value is 2.5m, so I just let the current above 2.5m is OK? what else do I need to consider?


texts: Usefulness of constant current limiting in bench power supply

texts:
I'm building a bench power supply as my introductory project to electronics.

When it comes to adjustable voltage it's easy to see the usefulness of such feature but I can't figure out what is the usefulness of having adjustable contant current limiting on a power supply ?

Isn't ideal to have a power supply providing as much current as possible/needed for a circuit ?


texts: Why services that need to receive a signal, like Bluetooth or GPS, drain cell-phone battery?

texts:
The title is self-explanative. This is an emprically contrasted fact for cell phones, although I don't know why this happens.

As far as my understanding goes the signal receiver is a passive component. Then, why does it affect battery so drastically?


texts: Atmega328p PWM overheating and flickering

texts:
I'm trying to build a dimming control for a 24V RGBW-LED strip using potentiometers as analog inputs. It's pretty similar to the analogWrite() example on the arduino website (arduino.cc/en/Reference/AnalogWrite), but with four inputs and outputs instead of one.

I'm using the Arduino IDE with the optiboot bootloader (optiboot_atmega328_pro_8MHz.hex) to compile and I flash the chips using avrdude from a Raspberry Pi's GPIO pins. The fuses are set to:

efuse: 0x05
hfuse: 0xd6
lfuse: 0xe2

Setup

Code

int RGBW_LED[4] = {10, 9, 5, 6};
int RGBW_POT[4] = {A5, A4, A3, A2};
int RGBW_VAL[4] = {0, 0, 0, 0};

void setup()
{
  for (int i = 0; i < 4; ++i)
  {
    pinMode(RGBW_LED[i], OUTPUT);
    pinMode(RGBW_POT[i], INPUT);
  }
}

void loop()
{
  for (int i = 0; i < 4; ++i)
  {
    RGBW_VAL[i] = 0;
    analogRead(RGBW_POT[i]);     // read once and discard
    for (int j = 0; j < 5; ++j)  // then calculate mean to avoid flickering
    {
      RGBW_VAL[i] += analogRead(RGBW_POT[i]);
    }
    RGBW_VAL[i] /= 20;  // divide by 5 for mean, then by 4 to scale to output range [0, 255]
    analogWrite(RGBW_LED[i], RGBW_VAL[i]);
  }
}

Problems

Random flickering on (different) outputs when turning potentiometers
Controller randomly "crashes" and needs to be reset when simultaneously turning the pots for red/green and blue/white. This does not seem to happen in other combinations.
The controller heats up (I think it's on the side of the output pins) the more potentiometers I turn "on". This also leads to the microcontroller crashing and needing to be reset.

What I have done so far

The setup seems to work fine as long as I am only turning one potentiometer. I have also more or less "solved" problem 1 by calculating the mean in code and writing that to the outputs pins. It seems more like a workaround to me, but at least it's functional. If there is a proper solution, I'm all ears.

Problem 2 seems to be related to the same PWM clocks running on pins 5/6 and 9/10 since simultaneous dimming on different pin combinations seems to work. Since I need four PWM controls for RGBW and the Atmega328p only has three independent PWM clocks I can't "cheat" this one though.

I have no idea what's going on with problem 3. I have tried using a separate power source (VCC from the Raspberry Pi) for the controller (thus dropping the voltage regulator and separating the circuits), that didn't change anything. I have tried removing the 24V source and the LED strip - same result. The only thing that did stop the pins from getting hot was removing the transistors, but I'm pretty sure that they are wired up correctly and since it also happens without the 24V source I can't imagine the current being out of spec.

I have tried modifying the code by adding delays, regulating the maximum analogWrite() value, and switching the power to the potentiometers before and after reading by connecting them to a digital output instead of VCC - all to no avail.

I've also tried using a different Atmega328p chip (got a few lying around) just in case, and it's definitely not because of a faulty chip.

Any help would be appreciated! Thank you so much!

EDIT:

I have included the circuit diagram below. Note that I omitted the voltage regulator and used separate 5V and 24V power sources. I have tested the circuit with both configurations and there is no difference. As stated above, I can even unplug the 24V source and the LED strip (cut the hand-drawn line in the diagram) and heating still occurs.


texts: Use 555 for additional 40KHz PWM in Arduino

texts:
I need to transmit infra red signals using IR LED from my Arduino device. The IR signals consist of PWM 40 kHz periods and "silence" periods of various length (typical IR remote signals).

I know there is IR remote library that uses internal clock registers, but unfortunately, my device has all PWM pins already used.

I need to power the IR LED with a regular PIN. As far as I know it's not possible to achieve exact 40 kHz on digital output PIN with software only. So I would like to include 555 circuit between Arduino digital output PIN and the IR LED so that the high state of digital PIN caused blinking of the LED at 40 kHz.

I'm not sure how the wiring should look like.

I was thinking of using this schematic:

(Source)

And attaching +5V to Arduino output PIN, but I feel this solution is not perfect. Is there any better way to connect 555 to Arduino output pin?

Update:
I used solution described by akellyirl below and it works perfectly. I used R1=1000Ohm, 2000Ohm potentiometer as R2 and C1=C2=10nF. Pulses triggered by arduino pin connected to Reset pin of 555 of length between 400 and 1600 microseconds are properly interpreted by my Technics HiFi.


texts: Modifying Voltage Controled Amplifier to become attenuator

texts:
https://www.fairchildsemi.com/application-notes/AN/AN-6603.pdf
Page 3 top left of this also shown in this screenshot:
http://i.imgur.com/rp3lYsl.png

How would you modify Figure 11 to make a voltage controlled attenuator instead of a voltage controlled amplifier?

A previous stack exchange post talks about DC inputs and using a switch instead- I'm not asking about those in this post
Voltage Controlled Attenuator
My input for example could be audio and the purpose could be to decrease loud sounds


texts: Efficiently limit current to led without power loss

texts:
Let's assume I have 3 Leds which have forward voltage of 3.3v and current rating is 300mA. All the leds are in series and I have a power supply of 12v. when I series a resistor to limit current it draws much power.

Calculations:

Voltage through leds =\$3.3v*3=9.9v\$

voltage drop through resistor=\$12v-9.9v=2.1v\$

Resistor value for \$300mA =2.1v/0.3A=7\Omega\$

Power loss through resistor \$= 7*0.3=2.1W\$

I need to reduce this power loss.
Is there any way with MOSFET or BJT transistors?
I read this http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/ . But i don't understand how to calculate values. Here is the circuit diagram in above site.

I don't need exactly this. I need a proper way to do that.


texts: Ways to drive a capacitative load with discrete transistors

texts:
I'm looking for a way to drive an ultrasonic transmitter using just discrete transistors. AN1536 is a good application note on the general principles, but they're driving it directly from the MCU and I'd prefer to build an amplifier/buffer.

The equivalent circuit of the transmitter looks like this:

EDIT: I intend to drive it with a 40khz PWM signal from an MCU at 3~5V. It will only be on for a few hundred microseconds (~12 cycles) and ideally it would not ring for much longer.

What are some circuits for this purpose and what are some things I should look out for?


texts: How to send Sensor Output signlas to Long distnaces?

texts:
In want to interface Incremental encoder sensor output to Microcontroller which is 10 meters away from the sensor.

Specifications:

Sensor Output : Square wave 0V to 5V , 100KHz frequency.

Controller: F28M35H52C, Interface Module: EQEP (Enhanced Qudrature Encoder Pulses)

As per my understanding, the available options are:

Convert sensor output to differential ended signals using RS422/LVDS etc....
Convert sensor output to differential ended signals using OP Amps  etc....

Is my approach correct?
Can i use RS422/RS485 for interfaces other than UART?

Kindly suggest the best method(s).  Cost is not a big concern for me, time and reliability are in my interest.


texts: Transimpedance Amplifier for Photodiode with low Shunt-Resistance

texts:
I am designing a transimpedance amplifier to amplify the signal of a photodiode. I plan to use the IC ADA4350 (datasheet), it contains an Op-Amp and analog switches to select different feedback paths for different gains.

I plan to use 3 different photodiodes, one of them has a very large shunt resistance  of 38GOhm but two of them have a very low shunt resistance, one is 2MOhm and the other 100kOhm. (datasheet diode 1, datasheet diode 2)

I want to use 5 different selectable gains, from 1k to 10M in decade steps. I calculate the feedback compensation capacitor for a bandwidth of 25kHz.
I simulated the circuit in LTSpice, and using the diode with the large shunt resistance of 38GOhm the results are as expected. But when I simulate one of the other two diodes that have a low shunt resistance I encounter the following problem: If the feedback resistor Rf is smaller than the photodiode's shunt resistance, it works as expected. But if the feedback resistor is equal to or larger then the shunt resistor, the amplifier circuit doesn't work. The output goes into saturation.

Can somebody help me to understand what is the cause for this behaviour?
How can I modify the circuit to make it work?

Thanks in advance for your help!

Kind regards,

Marcel


texts:
I'm planning on building a board with a bunch of logic gates on to experiment with. I'm looking for a kind of cable that I've seen before but don't know the name of. It basically connects to a solid pin, and is stackable (see attached picture). What is the name of such cables?

Thanks.

Edit like:


texts:
I want to use SG3524 for generating a PWM signal of 200kHz frequency to be provided at the common base for the two complementary transistors SS8050 & SS8550. This is to be a gate driver circuit for a mosfet used as a switch in a Buck converter.

How do I proceed after selecting R and C values?


texts: How does this sample and hold circuit work?

texts:
What role does the 30k resistor play in the LF398?

How would that resistor eliminate any offsets introduced by the op-amps in a circuit like this one:

On this explanation, I don't get this line:

  These diodes then require the 30k resistor to avoid overloading the
  output amplifier.


texts: Is it possible to extend LVDS and SPI to 3 meter distance

texts:
In a hardware design application, we need to extend below signals to 3-meter cable.

LVDS data @ 720Mbps
Clock: 72Mhz
SPI signals

So, I wanted to know

Is it possible to extend above signal to 3-meter distance via cable? What are the pros and cons of extending cable to 3 meter?
If yes can please suggest some cable.

Thank you!!


texts: Varying input voltage, constant current and varying output voltage from a buck converter?

texts:
I'm wondering the possibility of a circuit where there is a varying input voltage to a DC buck converter, that would output a constant current with varying voltages?

Let me explain via this diagram:

A simple buck convert circuit:

simulate this circuit – Schematic created using CircuitLab

The output voltage \$\ V_o\$ is now less than \$\ V_p\$(or \$\ V_i\$), however, the output current is now higher than the input current as that is the functionality of the buck converter. What if I  introduced \$\ V_1\$ in series with\$\ V_p\$ after some time \$\ t\$, is there a way to output the same current with the following: \$\ V_o + V_1\$? With \$\ V_1\$ as one of the input voltages(meaning can't have it in series with the output).

simulate this circuit


texts:
The following code basically blinks yellow  LED on MSP430 Launch Pad on port 1.6.

I had to use two

  do-while

loops for providing delays. Is there a way I can do this using a single do-while ?

int main(void)
{
      P2DIR = 0xFF;
      P2OUT = 0x00;
          P3DIR = 0xFF;
          P3OUT = 0x00;
        volatile unsigned int i;    // volatile to prevent optimization
       WDTCTL = WDTPW + WDTHOLD;       // Stop watchdog timer
       P1DIR |= 0x40;                  // Set P1.6 (Green LED) to output
       while( 1 ) {
           i = 9000;                    // SW Delay
           do i--;
               while(i != 0);
           P1OUT |= 0x40;              // Green LED On
           i = 9000;                    // SW Delay
             do i--;
       while(i != 0);

       P1OUT &= ~0x40;             // Green LED Off
   }
}


texts:
I am learning about the "AND" gate function in Navy school. What I know is that when a low voltage is at the base of Q1, the transistor is in cutoff mode since the collector is reading high (> 2 volts). This drives Q2 into saturation mode, meaning that its collector is reading a low close to 0 volts.

This is the accompanying image that I'm talking about:

I was wondering if someone could show me the math involved in all this. For example, if I applied 2.8 volts on test point A and 0.7 volts on test point B, then what is the predicted output voltage at test point X (reading off from Q2)? What diodes' resistance and resistors' resistance are needed for the "and" function? I should get a low, but I need to see the math.

In my textbook, it says that when the diodes are reversed we get the "OR" function so I know that the diodes play a role in the calculations.


texts: Why this LED strip is emitting light if any driver output wire alone is connected to either one of its terminals but only near the floor?

texts:
I was experimenting with LEDs, when I encountered the following strange behavior:
5 LEDs on a strip simultaneously emit  light when  I connect eny output wire from a mean well +36V 700mA constant current power source.
the strip  is about 40cm and has a clip to connect to its neighbor strip but the contacts on the clip are marked (+, -)
Connecting only red wire to + the strip lights
Connecting only red wire to - the strip lights
Connecting only black wire to + the strip lights
Connecting only black wire to - the strip lights
Trying all the above using another 18-32v 0.6A driver same result except they are now blinking at around 2 Hz
Try it on a wooden table:NOTHING, it works only when the strip is on the ceramic floor
Try it with a paper sheet between the floor and the strip IT WORKS
Try it with the whole sketch book: IT WORKS but very dimm
OK probably some mysterious EM field is causing this but maybe the strip has some hidden capacitors or capacitance behavior :
Try it with another strip: IT WORKS
TRY IT IN THE ALMOST DARK ROOM: IT WORKS
Try it with a 9v battery doesn't work(for the batery i used only 4 and less LEDs and the light is very bright when connected properly )
Try it with normal long legs red, yellow and green LEDs near the floor: doesn't work
the strip has glass buttons shaped defusers over each of the 4 leged LEDs and they don't light with one wire without removing it or maybe not visible . It also have other tow secondary side terminals that produce dimmer light for the same source than the main marked terminals when properly connected but nothing happens when a single wire is connected to either one of them.
What's going on?

Edit: Measuring the main AC voltage with the multimeter with only the red probe to the line(hot) while the black probe with its wire laying on the ground and not connected to anything gives 38 volts. Extending the black probe by conecting it to a other twi probes it reads 51 volts AC.
This is a first draft  of answering my own question and I'm not an electrical engineer nor an electrician so it can make no sense :If anyone can improve it and link it to the LEDs and the drivers and explain how they emit even by connecting the black wire alone  then I will accept that answer.
my theory that doesn't explain the whole story is:
This is happening in the first floor in concrete building where the house is grounded or the neutral is connected to the reinforcement steel cages between the floors and when the LED strip circuit or the COM probe from the multimeter is on the floor it interacts with the steel reinforcement cage by inductance similar to what happens in a transformer, if that is at all  what is happening in a transformer.
This came to my mind because some years ago after discovering that a similar house was not grounded an electrician suggested to me to do the grounding to the reinforcement cages.


texts:
I would like to replace original NTC sensor for: https://www.aliexpress.com/item/TGT70-EP-Thermoregulator-Touch-Screen-Heating-Thermostat-for-Warm-Floor-Water-Electric-Heating-System-Thermostat/32669215824.html?spm=2114.13010308.0.64.mHnkr7
with self-made NTC probe. The problem is that manufacturer doesn't want to share any information on it. All I got is the picture and short description of it (not type or chart/table). Can anybody help to identify it?

Thanks


texts: I want when 5V input is available the battery to start charging and disconnect from output. Also when 5V is not present battery be connected to the output load. Will this idea will work? Can I use 10k for R-Pull?


texts: N-channel MOSFET used to control 5V relay from 3.3V ESP8266 pin

texts:
Today I "played" with a relay for the first time.

I only had an N-channel MOSFET available (an IRLZ44N) and wanted to control the relay from an ESP8266's GPIO pin - i.e. use a 3.3V signal to control the relay's input pin, which expects 0 or 5V.

I had a 10K resistor handy, so I used it to current-limit the fet's Gate. To my understanding, MOSFETs only care about voltage, not current - so a "big" current limiter at the gate shouldn't matter anyway.
When the IRLZ44N is off, the relay's input is connected to the 5V over R1 - and when it's on, the input goes to ground. At that operational mode a resistor is needed; without it, the 5V would end up going directly to ground.

The circuit works - I tested it and the relay responds as expected. But measuring voltages, I saw that the voltage after R1 is not 5V; it's less, since some current goes in the relay's input. In doing so, the voltage drops from 5V to 3.5V; there's approximately 5mA going in the relay's input, and 1.5V ends up being wasted on R1.

It seems that if I had used a larger R1, the circuit wouldn't work - the voltage would drop too far. And as-is, 3.5V may be a marginal situation for the relay. EDIT: Using the 3.3V signal from the ESP directly on the IN1 input doesn't trigger the relay - so it seems the 3.5V we reach with this circuit is indeed borderline

Another disappointing thing about this circuit: when the relay is off, we  waste current through R1.

Can you guys recommend a better circuit to use with my IRLZ44N, to turn the ESP8266's 3.3V to 5V and optimally control my relay?

Thanks in advance.


texts:
Hell,
I'm trying to use the following sensor VL6180 with software I2C on PIC18F2458 running at 4Mhz, with USB functionality.
Currently the sensor doesn't work in terms of sending measurmenet, it can only be initialized at startup, but sometimes it couldn't do that also.
The max frequency from the software I2c library that MikroC provides is 20khz.
So my question would that sensor work with 20KHz.
https://cdn.sparkfun.com/datasheets/Sensors/Proximity/DM00112632.pdf Sensor Data sheet.


texts: Why not reverting back to DC current as main electricity?

texts:
In the early days the DC current was dominate, until Tesla came with AC because it can by step up/down by using transformer.

But today with advancing in power semiconductor devices, DC can be easily step up/down, most devices at homes are DC powered(or can be DC), in addition high voltage DC is more efficiency in transmission line(compared with AC) and also is less difficult to synchronize with other DC lines.

So why isn't there a comeback of DC as the main electricity?


texts: Types of sampling and signal processing: some conceptual questions

texts:
I'm studying signal processing and right now I'm going through types of sampling and how they apply, advantages and disadvantages. I have some questions about these concepts that I would like to clarify
Ideal periodic sampling: Can it be used in practice?
So my first question is regarding ideal sampling. Can it be used in practice? The notes I was reading told us that A/D conversion usually use this type of sampling. But how? One of the advantages I read about sampling with retention is that, unlike ideal
sampling, it doesn't deal with ideal impulses (impossible to generate?) and therefore it can be realized with a circuit. So then I concluded that ideal sampling cannot be realized by a circuit and therefore cannot be used in practice, let alone with A/D converters. But apparently it can? How is that so? Or is this just done by a computer and therefore we can generate the ideal impulses and apply them? I'm confused about this.
A/D converters: What sampling process can be used?
As I said before reading my notes I read that: A/D conversion usually uses ideal periodic sample, while D/A conversion (signal reconstruction) usually uses the sampling with retention process.
Then I read this:

In a sampling system followed by analog to digital conversion using an A/D converter ideal sampling with retention must be used but the sampled signal spectrum is not distorted.

Err... how is this correct? Isn't the point of sampling with retention that the replicas come distorted? What am I missing here?
Another thing that I read was

The rectangular sampling type can not be used in a digital signal processing system because the analog to digital converter requires a finite, nonzero retention time.

I understand this but then I wonder why is the ideal sampling then used in A/D converters. Is there any retention when using ideal impulses? Or the problem here is that the A/D converter cannot "follow" a signal, but it is fine with either sampling and holding, or sampling with an impulse? Can someone clarify this to me?


texts:
I am currently working on my first microcontroller hardware design; I had a microcontroller class in college, but it focused on the software side of things, and used a pre-made development board (for the Freescale 68HC12).

I have a question that I hesitate to ask because it seems fairly basic, and perhaps even obvious, but at the same time I have not been able to find a clear answer while searching through either datasheets or online forums.

I have decided on an STM32F7-series chip, and I am running into this query while planning out its basic power and ground connections. I see a total of 12 Vdd pins on the 144-LQFP package (9xVdd + 1xVdda + 1xVddusb + 1xVddsdmmc), but only 10 Vss pins. Quick aside: I briefly considered Microchip's dsPIC33F for this project, and I noticed a similar imbalance (7 Vdd pins and 6 Vss pins).

I have been reading some introductory hardware design documentation, and the importance of decoupling caps placed close to the device for each Vdd/Vss pair is always emphasized forcefully for high-speed designs. I wonder what I should do for those Vdd pins which have no obvious Vss pairing. My PCB will certainly be incorporating a ground plane layer, so I could simply decouple those un-paired Vdd pins directly to the plane, but I just always got the sense that those Vdd/Vss pin pairings were important.

Am I missing something obvious?

I have included a couple of pictures below, which show my current strategy for decoupling both a Vdd/Vss pair and a single Vdd pin. Please do let me know if there is an obvious issue with either method.


texts: How do you determine if a new microcontroller is defective?

texts:
I've never dealt with parts being defective strait from digikey, but 3 new Atmel ATmega164A's that I've received have been exhibiting extremely odd behaviour.

I narrowed it down to something to do with the clock and it turned out that the resulting clock signal from the supposedly "factory calibrated" internal oscillator was jittering between 650-700 kHz instead of the solid 1 MHz it's supposed to be.  I was able to write in to the calibration byte to get this very close to 1 MHz (still with some jitter) and most things work but the UARTs just don't behave properly, they seem to output a continuous stream of short pulses no matter what you ask them to do.

I've dealt with the low power version of this microcontroller before (164P) with zero issues and decided to drop it in place and check the clock output on that, and its a solid 1 MHz with no jitter.  I'm leaning towards the conclusion that these 164A chips are defective, but would there be any other tests I could try to confirm that?

Edit: Just thought I'd describe the process by which I'm measuring the clock.  I've enabled the clock output fuse bit and measured the appropriate pin with a logic analyser sampling at a very high rate.  I have a program which writes in to the calibration register OSCCAL and I've been able to trial & error my way to 1 MHz.

Edit #2: After further investigation, it appears that the microcontroller starts acting up after a certain program size threshold.  A bare-bones project with a single source file flashing an LED seems to be OK, but compiling and linking in any of my other files (say UART library or whatever) without even making a function call to those methods causes the microcontroller to behave in the described behaviour above.  Power connections are fine and proper decoupling has been exercised.  I don't have time to debug this any further at the moment, so we've gone ahead with the low power version instead.  I am unsure where exactly the problem could be either 1) 164A and 164P are not code compatible 2) Programming procedure is different for these two uC's 3) Units are defective.  I am confident in our board design and would rule out power issues.  Unfortunately, I can't really pick a correct answer so I'll leave this question as is - maybe I'll come back to the problem again in the future.  Thanks to everyone who provided insightful comments or answers, they might serve useful to someone else with uC issues out of the box.


texts:
So as some background, I have a bathroom exhaust fan with a built-in Bluetooth speaker. By default, the speaker is powered only when the light is on, but my goal is to have that on all the time.

The manufacturer was able to tell me that the speaker is powered by 8v, which I was able to confirm via multimeter. The speaker itself is rated for 3W; does that mean that it should require 350mA?

I tried to get a measurement of the current (using the A⎓ on my multimeter) coming from the existing line just to be sure, and I got very confused. It cycles in repeated steps: (roughly) 100mA, 200mA, 400mA, 600mA, 800mA, 1A, then back again.

Does this make sense to anyone? I wasn't able to find anything online about what this means. How can I measure the amperage so that I can ensure I get the correct adapter/transformer for this project?


texts: schematic errors in eagle regarding vcc and vdd

texts:
Hello somebody there ?

Can someone explain to me why VDD is connected to VCC directly ? Call me stupid but this cant be right . I hope I am stupid and to be able to learn something out of this :+1: Came on the schematic as soon as I did ERC and came as an error I tought ok maybe nothing severe ... maybe a warning but can this be valid ?

greets


texts: I am building an led matrix having 75 SMD 2835 60mA leds. I am connecting 3 in series with a resistance and then connecting the 25 series parallely to a 12V power source supplying 3A@12V. This means that 120mA will be divided among the 25 series, will this set up burn up the leds. Also what value of the resistance will i need to connect to the 3 leds in series?


texts: Why is there no frequency compensation required in TI's TL494 example buck regulator design?

texts:
This example circuit is given in Texas Instrument's application note SLVA001: "Designing Switching Voltage Regulators With the TL494":

They use a 140 μH inductor and a 220 μF electrolytic capacitor for the LC filter (capacitor value not printed on the circuit diagram but given in the accompanying calculations). This results in a cutoff frequency around 1 kHz and a -180 degree phase shift in the output. This output is then fed back trough resistive divider R8/R9 to one of the TL494's error amplifiers.
I don't understand why there is no need for any frequency compensation in this example. In fact, both this application note and TI's TL494 datasheet never even mention the error amplifier's phase. In the region above 1 kHz where the LC isn't yet attenuating much and the TL494's error amplifier can still easily reach the configured 40 dB gain surely the loop gain is above unity and the phase shift (LC filter + error amp's own) exceeds -180 degrees?
(I do realize the output capacitor's ESR introduces a zero that makes the LC filter's phase come back to -90 degrees at higher frequencies but that does not seem to be much help in the region right above the LC's cutoff point).


texts:
I've found this question but they don't talk about damage (Multimeter ranges)

If I measure a 20KOhm resistance an I'm for example in the 200Ohm range, can this damage my multimeter ?


texts: Calculating resistor divider ratio with load resistor value input and output voltage given

texts:
In the given circuit, the variable resistor R = 1MΩ is connected as shown to a load RL = 1MΩ. The
variable resistor is adjusted until the voltage V
 across the load is 8 V when the input voltage Vin =
27 V. What is the position of the wiper arm in percentage?

This is the question. I have solve it and my answer is 42%, but the solution said 36%.

My Calculation


texts: Does operating a DC motor at low PWM freq (500 Hz and below) deteriorate the motor performance?

texts:
What impact does a PWM signal of 500Hz and 20KHz have on a DC motor, especially in terms of performance, life-span of the motor, etc?

So far I have seen posts that only talk about the buzzing sound that occurs at low PWM frequencies.


texts: Conformal coating compatibility - parylene- or polyurethane-based vs aqueous NaSiO4

texts:
How compatible are parylene-based or polyurethane-based conformal coatings for tin-whisker mitigation with aqueous \$NaSiO_4\$ (sodium silicate) conductive coatings used for EMI\RFI\ЕSD protection in electronic circuit boards?

Which would I apply first?

Can I then pot the assembly?


texts: Is this optocoupler-based circuit design reliable?

texts:
Hello,

I have designed this optocoupler interface to an stepper driver. However, I'm not sure if it's all right. For R1 I made (5-3.3)/10mA ≈ 180 ohms. 3.3V taking into account the two leds voltage drops.

The output part is the one confusing for me. It's an open collector configuration that will be connected to the stepper as shown. I know that the circuit could be done without the 2n3904, but I want to include it. What do you think about the values of R2=10k and R3=3.3k? I'm not experted at designing so I'm asking for your suggestions. I'm not taking the CTR concept into account. Also I need to review the currents to be sure that it's all right at the output.

The circuit part inside the box is an input of the driver, so it's unmodifiable.


texts: "Shorting" clock inputs of multiple flip-flops

texts:
I have 2 7473 (JK-FF) ICs. So there are a total of 4 flip-flops with 4 clock inputs. They will all have the same clock pulse (check attached simulation screenshot).

I'm using a 555 timer IC to send the clock pulse. My question is can I just short the clock pins on the 7473 ICs and connect them to pin-3 of the 555 IC, using wires? Or do I need to use resistors to short them?


texts: two or more SDP610 Pressure sensor Interface with Arduino uno using I2C

texts:
I have interfaced one SDP610 Pressure Sensor using I2C with Arduino Uno R3.
Now I want to Interface more than one sensor with same controller(uno board).
I don't find any higher or lower address in my sensor datasheet.  In my code address of sensor is

typedef enum { eSDP6xAddress = 0x40, //(64) } PRES_SENSOR_P;

  The I2C address consists of a 7-digit binary value. By default, the I2C address is set to 64 (binary: 1000 000).The address is always followed by a write bit (0) or read bit (1). The default hexadecimal I2C header for readaccess to the sensor is therefore h81.

  from section 3.2 in the SDP610 datasheet

Is there any chances to change the address of SDP610 sensor and its possible to interface with same I2C bus?


texts:
When do you need a laser diode driver to power and pulse a laser diode?

Is it related to the power it needs or the speed of the pulse?
I am looking to use multiple laser diodes which have an output power of
5mW, can this be done directly from a PCB circuit board. And I am
wanting to pulse it at 1ns or faster.


texts: What is the difference between clock and pulse?

texts:
What is the difference between clock and pulse ?
For example:

Is the CLK-signal a pulse ?

By the way, why do they invented the term frequence ? In my point of view, they could have said 20 times that period in a second?


texts: I have a WiFi application that we need to encapsulate for environmental reasons. We did some test shoots with Krayden PA2692 since the molder had experience with it. It's a polyamide material. The datasheet didn't give any RF parameters, but searching indicates the dielectric constant should be in the 2.5-2.8 range. RF performance once encapsulated was about 30% of free air. Does anyone have any suggestions for classes of material or what parameters matter most?


texts: In BLDC sine commutation, why are the low and high of each phase inversions of each other?

texts:
In the diagrams that I have seen showing the PWM plots vs the sign wave of the high and low side fets for each phase of BLDC sine commutation, they are shown as being the inverse of each other:

Please could someone explain why it is preferable to drive the gates on inverse signals? (ignoring deadtime for the purposes of this question)

IE Why is it better to pull a phase to high during the off cycle of the low side, rather than leave it floating when you actually want current flowing out of the low side of that phase? e.g. at 240 degrees on phase A

Obviously while the sine is positive for a phase, the high side would be needed, and in order keep the bootstrap capacity charged it will also need switching to low side during the off part for the high side - so that side of it I can see an explanation for - though I may be missing the whole picture and I am unsure why the entire inverse is the best setting, when only a fraction of that should be needed to keep the boot capacitor charged.

However when the sine value is negative for the phase, I do not see the reason for the high side gate being active at all (eg for phase A from 180 degrees to 360 degrees)?

Is this related to an inductive property of the windings that I am missing?

Note I am specifically looking for what the benefits might be in terms of optimal operation of a BLDC motor, such as avoiding torque ripple or other losses of those are factors.


texts:
I am looking to make a capacitive single touch screen into a small table. Which I can use to put coffee cup etc on. It does not have to be waterproof but rugged enough to not scratch over time easily or break. There is a number of touch screens available but none seem to be rugged for this kind of use.

What can I use on top of the screen to make it durable without losing the touch capabilities of the screen?
Or are there screens like that available for a reasonable cost?


texts: s-domain to z-domain conversion in MATLAB

texts:
I want to convert a transfer function from s-domain to z-domain. But, by keeping variable i.e without assigning values to variables.
I tried to do it with s2z command but it demands numeric input, not variable
Thanks in advance.


texts: how will i convert an if less than condition to hardware in digital?

texts: i have a condition like if a number less than a constant ,then how can this be converted into hardware in digital design.Will this be converted into mux or something else?


texts: Transformer selection about arbitrary signal generator

texts: I need to produce an AWG output (or specifically a sinusoidal signal), using a transformer to implement isolation and voltage amplification. There is an OPA to produce a 20V output (20mA driving ability) connected to input of transformer, how to choose the transformer to implement 100V output on the secondary side with 20mA driving capability?


texts:
When I sample a sine wave output of a DDS based bench function generator I have noticed there is always harmonics of the fundamental frequency. For example, below is the function generator's output set for 2Hz 1Vrms sine wave in time series and this is sampled by a 16-bit single ended DAQ at 1kHz sampling rate:

And here is the FFT spectrum of the above stored signal.

Then I went to a DDS chip's datasheet and observed this type of harmonics in some of the plots. I'm not sure whether these two are related but here below from page 9, one of such spectrum:

What could be said about these observations about the harmonics? Is that because DAC part of the DDS? Or can that be a totally unrelated cause?


texts: Can't seem to get high-votage source driver (TD62783APG) working

texts:
I'm trying to power 12V DC motors using a  high-voltage source driver (TD62783APG or UDN2981.)

I made a small testproject with a 5V power supply and a single LED.
I thought that when driving I2 high that output 2 would get the voltage of VCC. But I can't figure out why it's not working. The IC is getting very hot and seems to short-circuit.

What mistake am I making with this circuit?


texts:
I'd like some input on whether or not to use a mechanical relay or some form of SCR setup to change the capacitance in my LC circuit that is currently operating at around 170V, 1A at 150kHz. (Not 220V, as the circuit shows)

Power is fused, isolated, rectified and sent through an H-bridge to the LC circuit from a Variac.

I thought of a design like this;

However, I think the opto-isolator should be on the MT2 side, not the M1 side. I may be wrong in that regard, but whatever; the main point being, I would like to put 3 of these capacitors in parallel and 'switch' them into the LC configuration separately.

Will this kind of design work, or am I better off using something like the aforementioned back-to-back SCR configuration, back-to-back MOSFET/IGBT configuration.

Please take into account the fact that I know very well this is quite possible using the correct relays, but it's more a question of whether or not this can be done using solid state parts.

EDIT: By the way, this is so I can tune what is essentially a Tesla coil digitally.


texts:
I am using software to simulate and learn more about 3-phase semi-conductor rectifiers (using SCR.) I also learn about the voltage notches due to the possible overlap between the SCR commutation. If I am correct the voltage notches appear on the input voltage.

So my problem is, no matter what angles I used on the SCR or experiments I make, I can't see any voltage notches happening on the input voltage.

Can someone help me and tell me how I can "force" or proper simulate the circuit in order to see the voltage notches happening?


texts:
I am planning a design for a high voltage (2.5kV) DC power supply to drive a HeNe laser. I would like to add a panel voltmeter at the power supply output to ensure it's operating correctly.
I found a 0-3 kVDC analog panel meter that seems perfectly suited for this purpose, but since it's old/used I don't have a datasheet for it. I do know it has a full-scale current of 1mA and that it says to use an external resistor (as expected). I calculated the series resistor to be ~3MOhms (the meter has 300Ohms of internal resistance, which I ignored). This gives me 833 uA of current across the meter, which seems to be correct - 83% of 3kV = 2.5kV, but at only 250 mV. Does this low voltage matter, or is the meter only sensitive to current? I was thinking it would make more sense for the meter to see 2.5V across it instead of 250mV.
Should I be calculating this a different way, or is this correct? I've never worked with analog meters before.


texts:
Please follow the paper in this link.

I have a 10Gbps NRZ signal generated which is to be fed into a 4:1 MUX. The system contains three components: The serial link chip consists of three individual macros: transmitter , receiver , and a PC Enhanced Parallel Port (EPP) interface. Transmitter consists of a 4:1 multiplexer (MUX) and an 8 tap finite impulse response (FIR) filter.

The link operates at 10 GHz, which is faster than typical CMOS clock speeds for this process, multiplexing is required to combine slower data into one 10 GHz bit stream. Assuming the CMOS clock is 2.5 GHz, the CML 4x1 multiplexer drives four bits every 2.5 GHz cycle. Four 2.5 GHz clock phases are the selection signals to the multiplexer. For example, when phases 0 and 1 are high, bit 0 is selected by the multiplexer. When phases 1 and 2 are high, bit 1 is selected.

Question1: How to drive the 4:1 multiplexer with four bits every 2.5 GHz cycle and 10/4 Gbps signal as input to each of the 4 channels and also do the reverse at the receiver which has a 1:4 demultiplexer?  Is there a general circuit/rule so that the same can be applied to MUX of other categories for different bit rate?
Question2: Is this also called serialization? What is the difference between serialization and the function of MUX?
Question3 : Is there a requirement of an ADC convertor and PLL /DLL for connecting the transmitter and receiver?
Question4 : What shall be the value of the parameter  number of Samples in the Discrete Eye Diagram block for a signal of 10Gbps?


texts: Fuse blown indicator circuits compilation

texts:
I have been working in a compilation of circuits to use that basically show to the user that a fuse has blown up, this is particulary useful in the bench, needless to say I haven’t tested all of them yet (transistor and SCR), and i want to leave them here to receive feedback about how to improve them or fix any mistakes you can find, if anyone can come up with any other designs in order to add them to the compilation, what they have to do is easy

Make a led turn on, when the fuse has blown
Work for positive and negative voltages

Up to now, the best design i have tested is the mosfet one that, makes the led turn on with or without a load connected this is helpfull since saves time and works for both possitive and neg voltages with some changes


texts: Electrolytic capacitors in guitar amps in odd configuration?

texts:
I am building a guitar amp for a senior projects class and one of the amps I am modeling around has some electrolytic capacitors used in a way I don't understand (see picture below) and more importantly I have no idea where to buy some of these values anywhere which makes me think these aren't electrolytic capacitors. Basically, won't this kill this caps considering its AC?

full schematic can be found here, I have completely changed about everything but the capacitors are still relevant.
http://www.mediafire.com/file/0jrroz0jx2ee8cj/Final+Version+Tremoverb+Diagrams+25+Oct+15.pdf


texts: Difference between a 3 phase VFD inverter and UPS inverter

texts:
this might seem like an odd question, but i consider myself still a newbie in Power electronics. This has been circling in my head for a few days.

Intro :

From a Hardware Standpoint i am assuming both are similar using a 6 IGBT inverter. DC source is a Battery. The first is driving an AC motor and the second is driving a 3 phase transformer. (I am not concerned with the charging part of the UPS, i am only interested in the DC/AC part aka inverter).

Question:

What is the control difference (Assuming both output sinwave) ?

VOLTAGE

a- Does A UPS system uses feedback from the output voltage to correct the PWM, to compensate for battery draining, or does it use fixed values since the waveform is constant (no voltage control)?

CURRENT

a- Does A UPS system use current control ? In a VFD you can Limit the motor current using V/hz or FOC, and reduce supply voltage, but that  might not be applicable in UPS.

b- How does a UPS react to an overload typically ?(turn off or limit output).

by the way for motor control there is large resource (app notes and DEV boards) i cannot seem to find much for UPS systems.