texts:
I am creating a Li-ion battery discharger. Only thing left is temperature control loop right now and I want to use PID for that purpose. I want to keep the temperature inside the device at max 95 Celsius. I am using PWM to set the discharging current. Which is 4500 for 2 Ampere ( maximum rate) and 9999 is the minimum discharging rate which is 0 ampere. So I will be discharging the battery at 2 ampere till temperature ( if it will ) reaches the 95 Celsius then I want to increase PWM values according to PID which will decrease the discharging current. However I cannot figure out how PID will be used for this purpose. I though following a way like this :

if(temperature <90) {
}
else{PID loop
.
.
.}

Will this approach break the PID loop? If yes then what kind of path I should follow. I am worried about integral part. It will keep increasing when the temperature is less than 95. But since the discharge current is constant 2 amp for this case, temperature will not rise and integral part will be increasing and increasing. And in case of any heat rise, piled up integration will break up the PID term in this case. I am looking forward for all the suggestions.


texts: Measuring a magnetic pulse using a coil, and circuit adjustments

texts:
I have the following circuit,

I am using it to create a pulsed magnetic field, in the coil. I am trying to measure and verify the magnetic field in the coil. I am testing it with 40 V to drive the coil at the moment, which should provide 20 A of current to the coil and produce a 12.5 mT field within it. There are additional unwanted oscillations that are making things less straight forward for me.

First I would like to verify the current going through the coil, so I included R8, to measure the voltage across it, to work out the pulsed current in the circuit.

The model result comes out a lot smoother, which is expected, as it is more ideal.

There is a lot more ringing/oscillations in my built circuit, but it comes out at just over 200 mV which indicates approximately 20 A of current.

I am curious about the large spike and oscillations, what might be causing this and how I might reduce these. Below I mention additional inductance that appears to be cause by the resistors R4 and R7, so this is a likely contributing factor.

Next I want to measure the magnetic field using a coil. Based on the design of the coil in the circuit, for 20 A of current it should theoretically produce a 12.5 mT B field.

Using a single turn loop, with an area of 1.29e-4 m^2 placed at the centre of the coil, the voltage should theoretically be V = -1.6125e-6/dt

based on V = -N dBA/dt

My plot of the loop voltage is

It spikes when the current goes on and off. However there is a lot of oscillation

If I use the first peak of the voltage, taking its time, the formula suggests a output voltage of 47 V needed for the 12.5 mT I expect, not the ~250 mV I am getting. So I have made a mistake somewhere or am missing something in my assumptions. The formula I am using I have typically seen for an oscillating field, but I thought it is applicable here also.

I would like to know where I am going wrong with my assumptions with the measurement coil, either theoretical or with my set up.

I noticed that the oscillations reduce further away from the initial spike if I touch the casing of R4 (and to some degree R3), which suggests they are adding an additional inductance to my circuit which is being reduced by the capacitance of my body as I touch it, and I have missed in the model.

Also looking at my pulse signal to switch on/off M1, it is not quite a square pulse when it is connected to the circuit.

This graph shows what happens to my function generator signal as from what it is set to do, when connected to the circuit with V3 OFF, and with V3 ON. It kind of gets up to 6 V which is about where M2 should switch on and goes down before going up again.

Note that M2 in the model is not the same MOSFET as in my circuit, it is actually a IRFP260NPNF MOSFET, I am unable to model the exact one in the circuit simulation (still learning).

I am hoping for suggestions as to how I might improve my circuit and reduce unwanted oscillations, and to improve the method I am using to measure the magnetic field, and how I might be going wrong.


texts: Using the ST-LINK Utility to configure the RTC to current time

texts:
What I was doing

I am using a STM32 microcontroller and for my project I need to be able to send data at specific times of the day (say, at 11am and 2pm). The microcontroller needs to know what time it is before I can achieve this. Unfortunately, I only have an one-way communication, and I therefore cannot request the current time from the network.

Therefore I want to set the current time, directly after I am done programming. I knew I am able to write data to the flash using the ST-LINK Utility Command Line Interface (ST-LINK_CLI) using the following command:

ST-LINK_CLI.exe -w32 <Address> <data> -Rst

I wrote a simple test script that writes the Unix time stamp to some address not currently in use by the code.

I was about to write a function to read the time-stamp and use it to set the RTC time. Until I read the following in the ST-LINK Utility User Manual:

  -w32 supports writing to Flash memory, OTP, SRAM and R/W registers.

When the manual says it supports writing to the R/W registers, does this mean I can directly access the RTC registers and set them? I have tried, but I can't seem to write to these registers.

I would prefer to use this method if it does, as I would not need to write a specific function to handle it on the microcontroller anymore. This means that I can set the RTC time of any microcontroller we currently have in use, instead of needing to update their code.

What I intended to do

To set the RTC registers, I tried to do the following steps, as described in the STM Reference Manual:

set DPB bit in PWR_CR register
write 0xCA to RTC_WPR register
write 0x53 to RTC_WPR register
stop the RTC by setting the INIT bit in RTC_ISR register
select the 1Hz clock by writing to the RTC_PRER register
load the current time by writing to the RTC_TR register
load the current date by writing to the RTC_DR register
start the RTC by resetting the INIT bit in RTC_ISR register

To access the registers, I have used the following addresses:

PWR_CR:   0x4000 7000
RTC_WPR:  0x4000 2824
RTC_ISR:  0x4000 280C
RTC_PRER: 0x4000 2810
RTC_TR:   0x4000 2800
RTC_DR:   0x4000 2804

What went wrong

I am not able to write to either of these registers. With the ST-LINK Utility, I get the following message:

  Error occured during memory writing!

Using the ST-LINK_CLI:

  Writing 0x00000100 at 0x40007000...Error!

Reading these registers is no problem, but I cannot write to them using either the ST-LINK Utility or its Command Line Interface.

The question

How can I write to the R/W registers using the ST-LINK Utility?

Is there some kind of write protect to allow writing to the RTC registers which I overlooked?


texts:
simulate this circuit – Schematic created using CircuitLab

At the top is a schematic of an H-bridge that I built. Im conducting experiments where I attempt to use it as an inverter. I built a circuit that drives the mosfets with a modified sine wave waveform. The circuit consists of an astable multivibrator with the two outputs connected each to monostable multivibrators. The output signals look like this:

This picture is from earlier experiment. When I acctually use the signals to drive the mosfets, the amplitude is over 10V. The blue waveform is offset down for clarity.

The blue and the yellow waveforms are applied to mosfets as shown in the schematic above. The idea is to allow current flow through one pair of mosfets, pause, and then drive the other pair. Here is the output as measured by my oscilloscope:

The space between the pulses is longer than intended (the  but that is not important for this experiment). This happened when I increased the voltage of the oscillator.

The output looks somewhat satisfactory except for the parts I've circled in red. They occur during the pause in the driving signal (on the edge of the driving pulse going zero). I understand that this is because the current now decreases, I get a voltage with the opposite polarity.

I would very much like to know how to possibly reduce or remove these unwanted opposite voltages. I have searched an answer to this problem but I have not been able to find a solution. I've been told that the diodes should be of help as they provide a path for the transformer primary current to discharge during the time when the driving signal is off. But they still ARE discharging and therefore producing an unwanted opposite voltage.

Any suggestions will be much appreciated!

EDIT: I did as Dave suggested and I reduced the dead time between pulses and added a load (a 100kohm resistor) across the secondary. This is the output:

The output looks the same with or without the load.


texts: Solution of current in series RLC circuit for a forcing function

texts:
I have a basic conecptual question related to series RLC circuit response
Assuming that I have sinusoidal source of the form
$$
V_{source}=V_m*sin(\omega*t)
$$
The equation for voltages in RLC circuit can be given as
$$
\ d''i(t)/dt  + R/L*di(t)/dt + i(t)/(L*C) = V_{source}
$$
I hope the above equation is correct. Now the solution to this equation is
$$
i(t) = I(t)_{ss} + I(t)_{tr}
$$
where \$I(t)_{ss}\$ is the steady state response (otherwise known as solution to non homogenous equation/forced response/particular solution) and \$I(t)_{tr}\$ is transient response (otherwise known as general solution/solution to homogenous equation/natural response).

Lets assume that frequency of \$ V_{source} \$ is equal to resonance frequency of the RLC circuit.
Now \$I(t)_{tr}\$ will tell you whether the circuit is under/over/critically damped and \$I(t)_{ss}\$ will give you the maximum amplitude of current which in this case will be \$ V_m*cos(\omega*t)/R \$ since the circuit is in resonance.
But i get the following response Now in the steady state (roughly after 0.8 ms), the current is completly defined by \$I(t)_{ss}\$.

So my questions are:

What is the governing equation for the rise of current in RLC series circuit (basically I need the governing equation for the green curve). I tried to simulate the complete equation in Matlab i.e steady state + transient thinking that the transient solution should take care of the initial green curve but apparently that is not the case
If the steady state solution describes the current after 0.8 ms then transient solution should be able to describe the green curve. The total solution should effectively describe the current profile shown in the picture. Is this correct?
To solve the homogenous equation, the initial condition is \$ i(0) = 0\$ and final condition should be \$ i(\inf) = V_m * sin(\omega*t)/R\$. Am I correct? How to include these conditions to find constants in homogenous solution?
This kind of current behavior is not covered in most of the literatures on the internet. Why not?
In order to define the green curve i will need an equation in the form \$ i(t) = {V_m(t)*sin(\omega*t)}/R\$. Am i correct?

Any help will be greatly appreciated. I know there are tonnes of forums/literature discussing the RLC circuit, but none has given me answers to my questions. I still remain confused.

edit:
I have added the input signal


texts: What does "Pins are on 0.17" centers" mean?

texts:
I'm looking at some switches (here) and the description reads:

  Small PC mounting slide switch features SPDT contacts and white
  positive action slide lever. Size about 0.56"L x 0.25"W x 0.34"H
  (excluding lever). Pins are on 0.17" centers.

What does "centers" mean in this context?  Will I be able to mount the switch on a standard breadboard?


texts: attenuated and biased output from op-amp

texts:
I've been struggling on build a noninverting amplifier with TL972IP (datasheet).

Here's what I've made:

Orange is for VCC+, Yellow is for VCC-, Green is for GND. Blue is for a signal input. Resistors are for feedback.

As it is hard to see, here's a diagram:

simulate this circuit – Schematic created using CircuitLab

With the configuration above, I've got this:

Yellow is the input and Blue is the output. As you see, input is attenuated (expected: gain of 2) and nagatively biased.

Where can I look into and see what's going wrong with this circuit?


texts:
Suppose all nodes in a CAN network are configured using acceptance filters to rx packets that are addressed only to them. Example: Node A configured to rx packets addressed only to "A" in the 11-bit ID field and so on.

Scenario: If there are four nodes, A, B, C, and D.

Question 1: If A addresses a packet to E (not a valid ID), will node A's ACK flag be set indicating that a message has been acknowledged by a node? That is, if a message is not accepted by an acceptance filter, will, whether a message has been rxd or not be known to the sender.

Question 2 (depends on question 1): If A addresses a packet to D (valid ID), does acknowledgement of the message indicate that only D has successfully received the message? Or, does it mean that all nodes received the message though their acceptance filters are configured to rx only their specific IDs?


texts:
I have an N Channel Mosfets I'm trying to use as a switch for a motion sensor and an LED strip light (12V <0.8A). It seems like no matter how I hook up the mosfet it is always set to 12V or stuck at 6.5V. It's my first time using one, so I'm sure I'm missing something simple.

Mosfet: RFP30N06LE
Motion Sensor: SR501 (Signal is ~3.3V)


texts: Connecting 2 male headers on a pcb together

texts:
I have 2 male headers like this on 2 different boards:

I need to connect 2 such male headers together. One way to do this would be to use something like individual female to female jumper wires. However, I am operating at a frequency of about 32-48 Mhz and don't want such long traces. I wanted something like a female connector on both sides, but I looked through all the types shown here and I still can't find any. Could someone give me any ideas as to what kind of connector I need to use? I dont want to make a PCB just for this.


texts:
I've been trying to create a balance control circuit for two audio channels. I'm finding it extremely difficult. I'm very adamant about a single knob controlling both the left and right balance while the center being even.

I've tried a bunch of voltage dividers using log pots, linear pots, dual dang pots, etc.. But I just can't quite get the behavior I'm looking for. It doesn't have to be perfect, just passable as an actual balance control. I find that it's very easy to get 1 channel to pan quite well from the center, while nearly impossible to get any sort of "near" linear panning from the other channel (this was mainly the case with dual-gang log pots). Another huge problem I have is setting the middle of the potentiates rotation as full amplitude for each channel.

I've recently considered using two MOSFETS/BJT's (one each channel) as some sort of variable attenuater each controlled by a voltage from a potentiometer (or a resistance from a dual gang potentiometer) but I began running into the problem of how to prevent one channel from being amplified while the other channel is attenuated. I cannot amplify the original signal very much (I can, but just a little) due to the fact that the output of this balance control circuit is the input to a class A amplifier circuit thats biased with 5V with a gain of about 13. I'm worried that if I amplify one channel due to balancing and then try to amplify I could exceed my voltage swing and cause distortion.

I asked a much vaguer version of this question earlier which ended up yielding a design that would work with well with the B5 (maybe B4) taper of this potentiometer series: http://www.bourns.com/docs/Product-Datasheets/pdb18.pdf
This works well creating two voltage dividers by connecting the 3rd terminal to ground but I couldn't find either of those models for sale online anywhere. Unfortunately this means I can't actually use this solution to my problem.

Lastly, I'd prefer to not use a microcontroller if at all possible. I want to print my amplifier circuit to a PCB at some point and I wouldn't want to have to interface it with anything.

This is the type of balance control I'm looking for:

Here's my current circuit diagram along with some strange voltage behavior.

The strange distortion as walked through the circuit:

The only thing I've changed in this simulation is that I disconnected Vsig_RIGHT.

I realize there's a fair amount of distortion even in the second graph I posted, but this is only when the volume is maxed by setting Rp1/Rp2 to 0. I'm still tuning the circuit. But obviously there's a serious difference between with the second source connected and disconnected. Any ideas why?

Obviously nothing is perfect, the main thing that I NEED is at 0.5 rotations of the potentiometer, I need the dB loss to be -3 or less. From there on out of course I'd like the "ideal" balance control curve, but I'm really just trying to find something that works well enough that isn't too difficult to implement.

It's also entirely impossible I have no idea what I'm talking about and this is a horrible curve for a balance control, so feel free to call me out if that's the case. I'd rather that than build the thing and have it be.. not so great.

Thanks for any help in advance!


texts:
I gotta get a Roomba because the dog hair builds up faster than I can get to vacuum it but I also want to make a beer bot that can go and fetch beer from the kegorator. Seems the Roomba is the perfect base and since I usually only drink on special occasions (read: the weekend) I think a dual purpose Roomba would be perfect.

I know there is a "developer Roomba" but it doesn't come with a vacuum. Is it (relatively) easy to add a usb connector to any Roomba?


texts: Can anyone help me understand how to implement a karnaugh map using multiplexers in logism?

texts:
I am quite confused on how to implement a function using multiplexers. I know how to use a karnaugh map and get the necessary minimized function that I need, but I don't know how to implement it in logism using muxes.

For example, if I were to get the following function:

f = \$\Sigma\$ (6,8,9,10,11,12,13,14)

The answer would be A!C + A!B + BC!D.

However, how does that translate in logism? what would the select bits be? And how would you use the 4 inputs A,B,C,D? Would you have to use multiple muxes, or just one?


texts:
I'm attempting to set up an H-Bridge that can be controlled from 1 GPIO pin of an Arduino.

I tried setting up the following circuit with a lab power supply and noticed the following:

When Vin was set to 5V, current was flowing through R5 to the right
When Vin was set to 0V, the power supply read 2.0V (wasn't able to bring it  down to 0V)
When Vin was directly grounded, current was flowing through R5 to the left

I then tried changing Vin via a GPIO pin on an Arduino Uno, flipping every five seconds. I noticed the following:

When Vin was set to high (5V), there was a voltage drop of 3.426-0.263=3.163V across R5 (going right). The GPIO read around 4.2V.
When Vin was set to low (0V), there was a voltage drop of 0.889-5.033=-4.144V across R5 (going right). The GPIO read around 0.3V.
When Vin was set to high, transistor Q4 got really hot.

I'm confused about a few things.

Why was the power supply unable to provide 0V to Vin?
Why was the Arduino unable to provide 0V and 5V for low and high?
Why did Q4 get really hot when none of the others did?
With the Arduino, why was the current in R5 smaller when Vin was high as compared to low when the circuit is symmetric?

( I(R5) is in the left direction )


texts: Multisim virtual JFET saturation current

texts: How I can set virtual JFET saturation current in Multisim. I can't find any parameter with appropriate name in model settings of virtual JFET?


texts:
I have an microcontroller ATmega8, TRIAC MOC3083 and thyristor M166P. I need to develop and device which will turn on/off lamp(220V).

But while I'm developing I don't want work with AC 220V now, DC 12/5V will be fine for me.

How can I connect these parts on the breadboard to be able debug my code? Please, show me a correct circuit.


texts:
We are using PICkit 2 (STL035V2.0 See here )  to program a PIC 16F676. We got the error :

  PICkit 2 VPP voltage level error. Check target & retry operation.
  Error in PICkit 2.

  We also get the error: Invalid OSCCAL Value detected warning.

We just found a solution and would like to post it here.


texts: Adding capacitor banks inside conventional PC to compensate for temporary power line disruptions

texts:
I've tried different ways to search the web for anyone who might have done this already, but can't find anything.  So I'll ask here.
Would it be possible to add banks of large capacitors inside the case of a conventional PC to act as a sort of short-term UPS to hold up the various supply lines (ie 3.3 volt, 5 and 12 volt, etc) for perhaps several seconds to maybe a minute or so just to overcome the temporary loss or a glitch in the mains AC power?  I know the effectiveness of this will depend on the current draw on any given line and the size of capacitors that are used.  The one drawback I can see is that the inrush current into the capacitors on power-up might be more than the power supply can handle.
A slight tangent would be to use a 12-volt sealed lead acid battery (instead of a capacitor bank) and put it directly on the 12v supply.


texts: How can I measure AC magnetic field using linear hall effect sensor with the arduino?

texts:
I have a SS49E hall effect sensor. I want to measure magnetic field in gauss using arduino analog output. I have a code for analog application but is this appropriate just for the dc magnetic field measurement? I am using a voltage transformer whose turn ratio is 100 V and 34,5 kV primary and secondary windings respectively. The transformer provide AC current at 50 Hz so there is AC magnetic field in the test setup.
Finally, can i measure the AC magnetic field at a constant frequency is 50 Hz with the arduino? Or is there another microconroller for the this measurement?


texts: How can wind turbine be used to frequency control in a grid?

texts:
I was listening to an interview (sorry don't have the source) from the Mexican's minister of energy, where he mentioned 'Wind turbines are useful even when the wind is not blowing because they can be used as frequency regulator'.
Now I understand the need for ancillary systems to regulate frequency swings, but I'm not sure I understand how a turbine can be used to do so.
Can a wind turbine consume energy (reducing frequency on the grid)?
Is there any way for a wind turbine to increase the frequency of the grid without the wind blowing?


texts: What is the best way to add a LED indicator to an open-drain sensor that's read with a GPIO?

texts:
I'm designing a circuit around a QRD1113 optical proximity sensor. Its output is open-drain, and I'm implementing a 10k pullup.
The signal is ultimately read by a GPIO on a RPI.
I'd like to add a small LED that turns on when the sensor activates, but I'm unsure of the best way to do it without causing issues with the GPIO. My instinct is to put the LED as if I were driving it directly with the sensor, and connecting the GPIO and pullup to the cathode as normal.
My design is below - is this a sound approach?


texts: Replacing a Switching Power Supply for an AC-DC Adapter

texts:
I am designing a 3D printer. I need 12V and 5 amp for powering the printer extruder and 11 amp for powering the heated bed.

At the moment I am using the model Model S-240-12 capable of delivering 12V at 20 amp.

In order to reduce some weight I thought that if I replaced the switching power supply for something smaller it would be great

I was thinking in replacing it for this AC-DC Adapter that says that it can deliver 12V DC at 16 Max:

AC-DC Adapter: 100-240 VAC to 12V 16Amp, 192W

So here I have some doubts.

1) If I am correct if I use the AC-DC Adapter provided in the link, I just need to make a current divider with the ramps and it will work fine, isn't?

2) The switching power supply has 3 terminals. Is it possible to connect the COM terminal that I want with any of the 3 +V terminal to close the circuit? Or is there an specific order that I have to follow?

3) Every closed connection of the switching power supply terminals is it capable of delivering 20 amp? But if one closed connection at the moment is delivering 20 amp. The other two closed connections are not going to be capable of delivering anything, right?

4) In my local city, it is not possible to find AC-DC adapters capable of delivering 16 amp. The maximum amount of current that I have found is 6 amp. After that if you want something that can deliver more current you need to use an switching power supply. So why is this? How is it possible that this company has an AC-DC adapter with those specifications? Is it legitimate?


texts: Assign record to different type without conversion function in VHDL

texts:
Brief introduction to the issue I am trying to solve. I have type, which is a subtype of std_logic_vector, representing generic frame. I have also few record types, which represent specific types of frame.

  subtype t_frame is std_logic_vector(23 downto 0);

  type t_frame_x is record
    a : std_logic_vector(3 downto 0);
    b : std_logic_vector(19 downto 0);
  end record t_frame_x;

  -- Conversion functions
  function to_frame_x (
    constant f : t_frame
  ) return t_frame_x;

  function to_frame (
    constant fx : t_frame_x
  ) return t_frame;

I would like to be able to assign signals/variables of these types without calling conversion functions. I was thinking about 2 ways to achieve this.

Overload assignment operators. However it looks like custom overloading of assignment operators is not possible. I am not 100% as I failed to find this explicitly being said in the standard, but I think so because I have found no examples of such overloading in the IEEE library source codes.
Make specific frame record types a subtypes of t_frame type. It looks like declaring a record as a subtype is also not possible. I have found no examples in the standard.

Does anyone know if it is possible to assign record to different type without conversion function in VHDL?


texts: In the example image below the pcb is shown to have a textured honeycomb like mesh texture on the solder mask. My question is how would one go about creating a textured finish to the PCB like seen in this picture below?


texts: Thermal Faliure of thermal overload protected ICs

texts:
I have encountered a number of instances now where ICs that supposedly include "thermal overload protection" will still heat up until they fry. Examples: LM338,LM2576.

These devices datasheets provide little details of the thermal limiting (temperature cutoff, reaction time, reset time, etc.) and also provide no power limit. Max power dissipation is simply stated "Internally Limited".

I no longer expect "thermal overload protection" to function at all unless the datasheet has a whole lot more data than the above.

Does anybody have any experience with these or other similar switching and linear regulator ICs actually shutting down non-destructively at a temperature limit, and is there some way I can roughly predict when this happens?


texts: Getting resonant frequency in LC circuit with L as air core coil

texts:
im trying to find inductance of the air core coil,i read that in LC parallel circuit with known capacitor value we can find unknown inductance value by the formula

so need to find 'f' resonant frequency.to find L

Im getting that resonant frequency in normal inductor (resistor like) but not in air core coil.
check the scope output with normal inductor and air core coil below.

1).with normal inductor 42uh getting resonant frequency

2). this is the output of air core coil,i didnt get the waveform like normal inductor,not able to find resonant frequency.

3) the coil i used ,68mh , i checked that inductance value with LCR meter

why the resonant frequency is not coming in air core coil?,how do i find inductance value of air core coil.?


texts: How much power can reasonably be collected from ambient background radiation?

texts: It seems that with a coil or simple antenna it should be possible to collect energy from the background 60Hz radiation in any modern home. How much could reasonably collected at low voltages (3.3-5V)? Could it be enough to maintain a sleeping microcontroller (e.g. 1uA - 100uA @ 3.3V?)


texts: Dictionary: is PWM precision the same of PWM resolution?

texts:
I have an issue in identifying the meaning of PWM precision. I've always talked about PWM resolution, and to me seems to be 1/2^(n-1).

Is the precision of the PWM just prequency precision? Or is the uncertainty?
Is the relative resolution just the indication of the minimum digital step?
Is the absolute resolution just the relative multiplied with the PWM period and therefore carrying the PWM precision or uncertainty?


texts:
In our lab we have NI cards and work with -10 to 10V. Oscilloscopes are rare and some mobile and quick-and-dirty solution would be fine for debugging. Therefore the 'poor man's oscilloscopes' that read out voltages on your phone USB (or audio jack) seemed perfect, and I want to build it - essentially this is inspired by VoltOTG and a review comment that you can 'just build your own using a voltage divider circuit and profit'. This seemed like a cool project!
However - most designs I found do not really match the low requirements I need, as in they seem way more complicated:

measure voltages -10 to 10V, only DC
Have a resolution of ca 2-200mV
Display voltages over time, ca 1khz speed
Do not (under any circumstances) damage my phone
allow for some stupidity on user side: allow for ca 30-50V inputs
be as portable as possible, ideally just a wire plus small circuit

My thinking: Use a voltage divider and a zener diode (or voltage regulator, like ams1117... to protect the phone) to measure, like this, then some kind of analog to digital converter chip to read out the voltage.
simple circuit diagram

essentially it's a 20V voltage supply a 20V Zener and two resistors in parallel to the zener, 1kOhm and 333Ohms to map -10 to 10V onto 5V (which I presume is safe and easy to read out?)
Questions:

What are the inherent limitations for a project like this (i.e. realistic expectations in terms of orders of magnitude: sampling frequencies, max voltage input)? Are the requirements achievable with affordable and few components?
What are (very generally) good ways to make a circuit like this 'user foolproof' to a degree that makes sense in an Arduino-like environment, especially, how can I protect my phone maximally?
Is there any general advice and feedback to give here from experts (like, this will never work, or it will blow up etc)?

Thanks!


texts:
I volunteer at the Dauphin Railway Museum in Manitoba, where we recently received a donation of equipment collected by CNCP Telecommunications in the 1970s and earlier.

Most has been identified, including testing equipment, telegraph relays, Telex terminals and a medical coil (!) but one piece has stumped everyone who's looked at it. It is a cylinder about 17cm diameter, wood at either end with a number of thick metal plates through it. On the upper surface there are a couple of connections for wire. The five hard metal posts on the top seem to be the heads of bolts to hold the whole thing together. A.E. Morrison (a former manufacturer of electric milk floats in the UK) is stamped into the top surface. I have not attempted to open it up as I suspect it would tell me nothing.


texts:
considering the following circuit :

         R1
    |--/\/\/\--------- A
    |                |
    |+               |
   (E1)              |
    |                |
    |------/\/\/\----|
    |        R2
    |
    |------/\/\/\---- B
              R3

Can anyone please explain to me why the voltage V(AB) calculated by the
voltage divider rule is equal to

Vab=[R2/(R1+R2)]*E1 ?

Is it fair to assert that you consider only R1 and R2 because R3 has no current flowing in it therefore has null voltage ?


texts: XBee dropping packets and actual data rate lower than expected

texts:
I am transmitting continuously at 9600 bps using the default configurations for both my XBees XB24-B.
The communication is one way only, the transmitter is connected to the ATMega328 UART and the receiver is connected to the PC via USB (FTDI).
Here is the actual data rate for a given program:

Wired connection (no XBee) : 7694 bps
from the ZNET 2.5 Router/End Device AT to ZNET 2.5 Coordinator AT: 6800 bps (some lost packets)
from the ZNET 2.5 Coordinator AT to ZNET 2.5 Router/End Device AT: 0356 bps (many lost packets)
from the Zigbee Router/End Device AT to Zigbee Coordinator AT : 0000 bps (doesn't work)
from the Zigbee Coordinator AT to Zigbee Router/End Device AT : 0328 bps (many lost packets)

Why is that? Is there anything I can do to improve these rates?

Edit For higher baud rates (115200) I get even worse packet drop rates:

Wired connection (no XBee) : 94200 bps
using XBee XB24-B ZNet 2.5 : 27900 bps

Edit If I make the Coordinator address the End device, then the packet drop rate falls to the normal levels (6800 bps), which is not ideal but better than the previous scenario


texts: Is it possible to just take a normal (continuous) laser diode and pulse it? Or does this not produce the same effect as pulsed laser diodes?

texts: At the moment, I am planning for a project involving lasers (yes, I have been lectured on laser safety). I am looking for a cheap way to build a pulsed laser in the near-infrared range. Since laser diodes are typically relatively cheap, I thought that it would do well in satisfying this requirement of my project. I managed to find a relatively cheap laser diode of appropriate wavelength, but it is not pulsed. Is it possible to just take a normal (continuous) laser diode and pulse it (by building an appropriate pulsed laser driver, or something)? Or does this not produce the same effect as pulsed laser diodes? If this is indeed practically feasible, then how can one go about doing this (links to resources/information are appreciated)?


texts: What tools or standards can be used to improve embedded C code reliability?

texts: I typically program PICs in C, usually for switched-mode converters. I've heard of various static analysis tools and standards like MISRA C that can be used to help improve the reliability of code. I'd like to know more. What standards or tools might be appropriate for my context?


texts: Nokia is a mobile phone brand, but what is an FAID? I tried searching but no definition came up. I'm guessing it's a security feature checked by the hardware in order to function properly.


texts:
I understand that FPGAs can be used for digital glue logic on a circuit board, like NOR gates.  They can also directly run AES encryption, Ethernet and Linux.

I'm not very rich and not an electronics expert.  Nor do I have a posh logic analyser.  I could probably put together a single board 6502 computer if I copied the code from somewhere.  If I wanted to rationalise my component count of AND gates, flip flops and BCD decoders, is a FPGA feasible for my position?  This is the level of sophistication I'm looking for, rather than microprocessor cores.  Or, is there an alternative glue technology suitable for a downbeat hobbyist?

Supplemental:

A better question might be "what can I replace 5 OR gates, 3 Schmitts and a Divide by 10 counter with?"  Thing is, I'm also factoring in the cost of the design software.  A £25 development board + £5000 /seat compiler + £1000 programmer isn't much good to the poor and deprived.


texts: Is there a chance that this will still work after replacing the capacitors?

texts: PCB from an acer monitor. I just plugged it in and it went up in smoke. i opened it up and saw that the capacitor is leaking fluid. will this burnt pcb still work?


texts: 555 Timer Circuit Simulation Generates an Error

texts:
I simulated the circuit below:

The expected output is a 50% duty cycle 40 kHz square wave but the simulator (MultiSim) generates an error and doesn't compile. The error message is as follows:
"A simulation error has occurred. Would you like to run the Convergence Assistant to attempt to resolve this problem automatically?"
I ran the Convergence Assistant and that didn't solve anything.
Any ideas why this might be the case?


texts: How to use same low pass filter for square and sine wave

texts: I'm trying to desing simple DDS waveform generator using DDS IC, but I'm a bit lost about designing output filter for it. My requirements are 1 Hz - 25 MHz sine, square and triangle/ramp wave. Using Analog Device's great online evaluation tool I've came up with a fact that I need to use ~50 MHz lowpass filter, but I'm struggling about how will it behave with square and triangular waves of maximum required frequency. Won't it just try to drop them down to sine waves. If it's true, then do I have to create 3 different filters for different waveforms and switch them when switching waveforms? How this problem is solved in production-quality devices?


texts: Starting in circuity, Should I use Arduino?

texts:
Possible Duplicate:
  How to become an embedded software developer?

First, I am sorry if this is the wrong stack, feel free to move it to the correct one if possible.

I am a rather experienced programmer, knowing C#, VB.net, PHP, C, C++, Objective-C, Java, JavaScript, and I have even coded briefly in ASM86.  That being said, most of my coding is done in Visual Studio, which I prefer as my IDE whenever possible.

After browsing LifeHacker and reading about Arduino, I instantly became interested in building stuff with this.  I been researching it the last few days, but figured I can ask some experienced people if this is the best, most flexiable beginner option, or if there are better (specifically since I prefer my Visual Studio IDE) options?  I don't mind coding C++ once so ever, though I love Visual Studio so C# would be fine too. I recall seeing something about VS and building robotics, so if that's an option thats fine.  However I def do not want to use Java, as I am not found of the language or IDE options (just a matter of preference).

I would appreciate some constructive feedback on which microcontroller would be a good starting point, and would allow a lot of flexibility.  I understand I would eventually need to expand to different boards, however I would like to start with one that allows for the best transition to these.

My first project, after doing the basics, will be making a doorbell with MP3 Support.  I already know this is possible combining several projects I found for the Arduino (though memory wise, not sure if it can handle), so I need to make sure what I choose is flexible.  Note, I have no interest in building huge robots that battle, almost anything I build would be DIY convince items for my house.  Plus I always wanted to learn the principles of circuitry.

If Arduino is the best option, I would love some advice on nice starter kits.  I found a few already, but it always helps to have feedback from users who have used the kits.  I know this kit won't include what I want for my first project, but I would like one that includes everything I need to do all the basics before I move on to this project.

Thank you so much in advance for your feedback!

Edit:
I am currently looking at netduino.com as we speak including reading:
Should I buy a Netduino or Arduino?


texts: Synchronize internal DAC to I2S on STM32F4

texts:
I have a CS4344 DAC connected to my STM32F407 outputting sound at a 44.1kHz rate with DMA and I2S and I would like to output and envelope signal through the internal DAC of the STM32F4, in sync with the I2S.

I could use a timer at a frequency of 44.1kHz but the 2 outputs wouldn't be in sync.

Is it possible to use the I2S WS clock to trigger the DAC conversion? So that everytime a sample is sent through I2S, a sample is converted through the internal DAC?

Thanks in advance!


texts: Prevent MOSFET input being low when connected to output of powered off device

texts:
I am driving a row of LEDs using an P channel logic level MOSFET (SI2323DS-T1-E3CT-ND) to switch power from a bench power supply. The gate is connected via a current limiting resistor to an output of a 74HC165 8 bit shift register.
The shift register VCC is being powered from an Arduino 5V supply, I have connected the grounds between the Arduino power supply and the bench power supply.

simulate this circuit – Schematic created using CircuitLab

The gate of the Si2323DS has a pull up resistor, the intention being to turn off the leds until Q1 pulls it low, everything works as expected until I turn off the power to the Arduino, at which time the MOSFET turns on.
It seems that in the "powered off" state the output from the 74HC595 acts like a low resistance pathway to ground and the pull up resistor is unable to raise the gate to a logic 1?

It's important that the MOSFET is off under normal conditions because if all the rows are enabled by default in the final design, an over current condition will occur.

Given this configuration, is there any way to ensure the MOSFET is turned off when the 74HC595 is powered off?

I thought it might be possible to invert the logic using a transistor such that a logic high form the 74HC595 would be required to turn on the MOSFET, but if the problem can be solved with fewer components that would be optimal.

I am only using 2 power supplies during the prototype phase, ultimately the Arduino and the LEDs will be powered from the same PSU.
Thanks for any help/suggestions you can offer.

I should also point out this was just a bench test for using the MOSFET, ultimately I am going to use current sinking high power shift registers (MIC5821) to sink the columns of my LED matrix similar to this design.


texts: What would be needed to read USB keyboard input on the 8266 or ESP32 chip?

texts:
My objective is to read input from a Keyboard Wedge device (i.e. Hand Scanner) which will emulate a keyboard entry and a carriage return and then broadcast that information to the cloud.

I think I may be good from a software perspective (once I figure out how to capture the input) to make that happen but not certain if I can capture that input directly using an OTG cable directly into the 8266 or if I need some other board to use in conjunction with the 8266 to capture this information.

As an alternative I could use a Pie W but I'd like to see if I can produce something even cheaper when you consider all the accessories involved etc... and like the 8266 and the ESP32 as options.


texts: Is Power Factor only relevant at rated load in Light Equipment?

texts:
As you might know, LED lamps over 25W require a minimum 0.9 power factor in Europe.

I have designed a PSU for a specific LED lamp which is rated about 50W. There is a PFC-stage (crm) in order to achieve a high PF. However, if I reduce the load to 25W (input) by dimming the light, the pf will be below this value (0.85 - 0.87) for 230VAC. For 264VAC, there is not even a chance to come close (below 0.8).

Now the question is, has the power factor requirement of the lamp to be fulfilled for the nominal rating or also for different loads (dim level)?

I have checked some datasheets of 50W LED drivers which would not achieve 0.9 pf at 25W load although they have a build-in active pfc function. At nominal load, there is no issue.
I have also checked a UCC28051 TI Eval Board with same issue (0.87 at about 25W):- datasheet, See Table 5 in Chapter 6.1.1.

If the requirement has to be fulfilled for different dim levels as well, how is it possible to achieve this with a standard pfc? What about 265VAC?


texts: How to calculate the total charge of a sphere which has a none uniform charge distribution?

texts:
If I am given a certain funciton which describes the volume charge density within the sphere with respect to the radius (ρ(r)),how can I calculate the total charge within the sphere.My idea was by calculating the total charge of many infinitesimally small and thin circles.
Initially, I though that I could use  $$\int (πy^2)*(ρ(r)) \, dr$$
Where $$\ x^2 + y^2 = r^2$$
Because this idea it didnt work i thought of using the areas of small spheres times the volume charge density
$$\int (4πr^2)*(ρ(r)) \, dr$$
It worked by I am not sure if this is the proper way or if it was pure luck due to the numbers that i got the answer right.

Even if the 2nd way is right can someone give me some more information in order to understand it better, or is there a better solution which is more understandable.


texts: IR LED for night vision LED driver necessary?

texts:
I am working on a project that requires a night vision camera. I have a small camera placed on the PCB and 4 IR LEDs placed around it to illuminate the dark room. The rooms are about 20-30qm.

I have selected the OSRAM SFH 4250 IR SMD LED. It has forward voltage of 1.5V, 100mA forward current.

I have two questions:

Are there any security issues with this kind of IR radiance? I want to use the system in my home with 2 small children. Is this kind of IR radiance dangerous to the eyes?
Do I need to use a LED driver? Or is it enough to run with a MOSFET (N-Channel) is shown in the schematic below.

If I need a LED-driver. What is a good choice. There are so many devices to choose from and I actually find it difficult to find an appropriate one.

Thanks for your help.
Phillip


texts: What is the Cheapest way to build a proximity-aware led wall

texts:
I want to build a led wall pretty much like this one:
interactive led wall

What are the different approaches to detect the people passing by? Looking for an easy - unexpensive way to do it.

This led wall can be  mounted indoors, and leds / lights may be smaller as well as the whole led array size.

Thanks!


texts: Do same current formulas apply if a capacitor is added, and vice versa for inductor

texts:
Ok so the title question is a bit misleading but its hard to explain in that small space.
My questions concern themselves with the analyzing of the circuit observed below, however fundamentally speaking my questions are about understanding the concepts.
In my text book (and no I am not looking for numerical answers) it wants to know a plethora of values of the peak to peak kind , rms , average etc...
The issue is that I am given the techniques to find something like voltage ripple peak to peak and output voltage minimum , BUT using a "C filter" with just a resistive load. Then I am given techniques for finding load inductance to limit ripple current BUT the sample problem only has a resistive load.
I am given an LC example but it only works out how to find L1 and C1 which I have worked out and figured them out , but all the other things like ripple voltage , filtered output max, min , form factor and all those other things are only explained for simpler circuits and not this one.
Then I am given this circuit which is not just a "C filter" and not just an "L filter" but an LC filter and not just a resistive load but an RL load.
So my question is do the techniques for finding values still apply , when finding currents do I just look at the inductor techniques and when finding voltages do I just concern myself mostly with the capacitor techniques? Regardless of the fact that they were for simpler circuit with no RL load.
I dont know how to jump form  a simple isolated example using a capacitor or inductor filter with resistive load, to a problem with both LC filter  and an RL load.
And I repeat I have the values for C1 and L1 already they are dependent on Freq. R1 and L2.
Average Output DC Voltage
average output DC current
Output DC power
RMS output Voltage
RMS output current
Rectification Ratio
Form Factor
Ripple Factor
Crest Factor
Transformer Utilization Factor
I am given techniques for some of a the above but the example are always different circuits.


texts: Which way to hook up boostrap diode for switching regulator?

texts:
In the datasheet for the switching regulator I'm using, it says you can supply an optional diode to put on the BST pin of the regulator, and in Figure 2 it says IN if Vin less than 5.5V, or OUT if Vout less than 5.5V. In the picture, I am unsure which way they have it hooked up, I am assuming 'IN' since the diode is pointing towards the BST pin? The regulator is a fixed 5V output model.

So I need help on trying to understand which way to hook it up, as the datasheet doesn't say much about this diode: An external bootstrap diode (D2 in Figure 2) is recommended if the input voltage is less than 5.5V or if there is a 5V system rail available. This diode helps strengthen gate drive at lower input voltages, result- ing in lower on-resistance and higher efficiency.

The regulator's input is on the same power source as a 12V starter motor, which is controlled by a MOSFET, there will be a voltage drop on the circuit when the FET is activated, so would hooking this diode to 'OUT' help the situation since in Figure 2 it specifies 'OUT' if Vout less than 5.5V?

Would hooking up the diode's cathode to GND and anode to the BST pin be what they consider 'OUT'? On second thought maybe I need to hook it up as 'IN' since the voltage drop happens on the input if the starter motor approaches stall current, the battery voltage can dip to 4.4V temporarily.

Sorry for the multitude of questions.

Thank you for your help.


texts:
I'm trying to build large LED panels (3x128 LED modules) using WS2801 LEDs, with data coming from a Teensy 3.0 microcontroller. I'm having difficulties transmitting my Data and Clock signals between the different panels. The three panels have a separate power supply, so I can't transmit my signals directly because of ground problems.

I want to transmit my signals using RS485, so I got myself MAX485 chips, and am using them to symmetrize my signals. So far, it works without any problem if I want to get my signal to the first panel:

  Teensy output TTL -> Max485 => (RS485) => Max485 -> TTL

However, when I want to get my signal to the following panel, I'm having a problem. I want to get Clock and Data coming out from the last LED, and RS485 them to the next panel - and this is precisely what does not work. What I want to do is:

  Teensy output TTL -> Max485 => (RS485) => Max485 -> TTL -> Max485 => (RS485) => Max485 -> TTL.

I know RS485 is in fact a 3-wire system, and I do have a common ground routed from my microcontroller.
I was thinking it might be a ground problem, but I don't know exactly where my problem comes from, since my reception MAX485 and my emission MAX485 are all powered by the same 12V power going to the LED (brought down to 5V, using a LM7805 regulator).

Note: the signal and clock signals output by my last LED are correct, if I route them directly to the following panel, it works alright, but I'm getting artifacts when all 3 panels are connected - that's why I switched to RS485

Does anyone have a hint regarding this ?


texts: What does this circuit do? Op-amp with transistors in feedback

texts:
I'm an electrical engineering student and I find this circuit in a guitar amplifier schematic, and basically, I'm just wondering what it does, and how one would go about working out what it does.  Like what approach do you take when you're confronted with this kind of problem.

P.S.  The voltage source supplies for the op-amp are actually 16V, not 15V.


texts:
My UPS is dead, or more correctly speaking, its battery is dead. I want to make a lithium battery pack to replace it instead of buying a new lead acid battery for it. Here are few questions:

1, it's rated at 350 VA / 200 W; Does that means that I need to provide 350va/12v=29.1 A from my lithium battery pack? It comes with a 3ah lead acid battery. Does it mean that this UPS was sucking almost 10c at that tiny sucker?

2, How large, in capacity, do I need my 12v 3-cells lithium battery to be? I got some tested 2ah 18650 from used laptop packs. If I use 9 of them, then it's a 6ah battery, and for 29A, It would be discharging @ 4.8C. Is it safe for typical laptop 18650 to discharge @ 4.8C?


texts:
Soldering wire is very soft and pliable, but solder on a circuit board is hard.  Why?  I haven't been able to find a definitive answer, but some ideas that come to mind are:

Some kind of chemical reaction that takes place when the solder is heated and then cools.  If so, what is this reaction?  Maybe with flux reacts somehow, but what about solder that doesn't have flux?
The solder wire is less dense, either through being hollow or having a flux core, making it seem easier to bend.  This seems less likely, because tin whiskers seems much harder than solder wire despite being thinner.


texts: ESP32 Neopixel acting strange when using dual core functionality

texts:
I have just started using ESP32 and tested dual core functionality, which works fine i.e. can blink two leds with different blink intervals parallelly. Also I've tested touch sensors, they also works fine. Problem came when I combined both. Actually I wanted to execute touch detection in one core and control neopixel led strip(WS2812) in another core.
Below is the code I am using:-
#include <Adafruit_NeoPixel.h>

TaskHandle_t ConnectTask;

#define LED_PIN 26
#define LED_COUNT 300
Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

int touch[] = {27, 14, 12, 13};
boolean touchStarted[] = {false, false, false, false};
unsigned long touchTime[] = {0, 0, 0, 0};

int threshold = 90;
int touchMinDuration = 100;

void setup() {
  Serial.begin(115200);

  strip.begin();
  strip.show();
  strip.setBrightness(50);

  xTaskCreatePinnedToCore(Connect, "Connect", 10000, NULL, 1, &ConnectTask, 0);
  delay(500);
}

void loop() {
  colorWipe(strip.Color(255,   0,   0), 50);
  colorWipe(strip.Color(  0, 255,   0), 50);
  colorWipe(strip.Color(  0,   0, 255), 50);

  theaterChase(strip.Color(127, 127, 127), 50);
  theaterChase(strip.Color(127,   0,   0), 50);
  theaterChase(strip.Color(  0,   0, 127), 50);

  rainbow(10);
  theaterChaseRainbow(50);
}

void Connect( void * pvParameters ) {
  for (;;) {
    checkTouch(); // works fine if comment this
    delay(10);
  }
}

void checkTouch(){
  for (int i = 0; i < 4; i++) {
    int t = touchRead(touch[i]);
    if (t < threshold && !touchStarted[i]) { // touched
      touchStarted[i] = true;
      touchTime[i] = millis();
    } else if (t >= threshold && touchStarted[i]) { // touched not
      if (millis() - touchTime[i] > touchMinDuration)
        touched(i);
      touchStarted[i] = false;
    }
  }
}

void touched(int id)
{
  switch (id) {
    case 0: Serial.println("TOUCH 1"); break;
    case 1: Serial.println("TOUCH 2"); break;
    case 2: Serial.println("TOUCH 3"); break;
    case 3: Serial.println("TOUCH 4"); break;
  }
}

void colorWipe(uint32_t color, int wait) {
  for (int i = 0; i < strip.numPixels(); i++) {
    strip.setPixelColor(i, color);
    strip.show();
    delay(wait);
  }
}

void theaterChase(uint32_t color, int wait) {
  for (int a = 0; a < 10; a++) {
    for (int b = 0; b < 3; b++) {
      strip.clear();
      for (int c = b; c < strip.numPixels(); c += 3) {
        strip.setPixelColor(c, color);
      }
      strip.show();
      delay(wait);
    }
  }
}

void rainbow(int wait) {
  for (long firstPixelHue = 0; firstPixelHue < 5 * 65536; firstPixelHue += 256) {
    for (int i = 0; i < strip.numPixels(); i++) {
      int pixelHue = firstPixelHue + (i * 65536L / strip.numPixels());
      strip.setPixelColor(i, strip.gamma32(strip.ColorHSV(pixelHue)));
    }
    strip.show();
    delay(wait);
  }
}

void theaterChaseRainbow(int wait) {
  int firstPixelHue = 0;
  for (int a = 0; a < 30; a++) {
    for (int b = 0; b < 3; b++) {
      strip.clear();

      for (int c = b; c < strip.numPixels(); c += 3) {
        int      hue   = firstPixelHue + c * 65536L / strip.numPixels();
        uint32_t color = strip.gamma32(strip.ColorHSV(hue));
        strip.setPixelColor(c, color);
      }
      strip.show();
      delay(wait);
      firstPixelHue += 65536 / 90;
    }
  }
}

Problem with this code is that led strip working strangely i.e. strip turn white and starts performing white spiral loop at certain intervals (Let me know if video is needed).
If I comment this line:-

checkTouch();

inside Connect task. Strip animation works as expected. I can't understand why Connect task is interfering with loop() when they are running on separate cores, also Connect task don't have any code for neopixel control, just checking touches (touch functionality is working i.e. prints "TOUCH 1" etc).


texts:
How do I measure the inductance of this air round coil attached to the antenna of a tube radio? I have read something about LC tank circuit here but im not sure how I would apply it. Would I use the resistor already attached to the coil and probe it with my oscilloscope? Inductance is an unfamiliar territory for me and any assistance or advice would be great!!

I have the tube radio schematic below.


texts:
Can somebody please help me with understanding how to derive the equation from the red box from included picture (the other equations are trivial, it's just the right usage of De'Morgan's law)? I am able to derive the equation for the NMOS device thanks to this video: https://www.youtube.com/watch?v=CoTR3bwtW_c , but not for the PMOS one. Can You, please, explain how to do it step-by-step? On the upcoming test we will probably have something more complicated, so the more I understand the better. Also, I don't know what should I do with more complex circuits, especially with PMOS.

Unfortunately, my lecturer didn't explain this good enough...

What about something like this? (I came up with this by myself, so I don't know if it is even doable, so please excuse me my lack of knowledge, I am still learning; L is the output)


texts: Why TIP127 is heating up when used in the circuit given below?

texts:
I am using this circuit as the automatic transfer switch where I am providing input from battery and solar panel and taking the output to run the motor.
Where AC/DC is written I am using the battery from this input where the motor is running slower and TIP127 is getting heated up and consuming extra energy.
As I have nearly no knowledge of electronics and took this circuit from a website.
It would be great if anybody could tell me why this is happening and how can I stop it?
As I want to make circuit very efficient and hence trying to reduce any kind of energy loss. Also when run via second input the motor is running extremely well.
Thank you.


texts:
I have bought a new 24v dc fan for my 3D printer’s power supply.  It’s meant to be quieter. To install it I had to crimp a JST-XH 2 pin 2.54 pitch connector onto the wires and open up the supply.  I matched the existing red wire from the old fan, screwed it into place and closed up the supply.  When I turned on the printer, the fan did not start.
I haven’t actually taken it out yet.  Wanted to get some ideas.  Can I test for continuity?  Part of the issue with testing is that the only 24v supply I have is the printer.  Will it turn With 12 v?  WhaT do I need to look for to tell if it is DOA or my crimp job?


texts: Understanding why not to use a resistor for multiple LEDs

texts:
I'm researching into using one resistor to control a 7 segment display. Not because I want to do so (could save some time), but just to understand concepts.
Some say that slight differences between each LED can cause very unequal lighting, which make sense, but at the same time they say that this could cause damage.
I don't understand this: On an LED Voltage-Current graph, does the LED "pull" a certain current like it has resistance?
If I have 2 LEDs in a parallel circuit, both parallels have to drop 2V, but one LED is 2V at 5mA, and the other is 2V at 10mA, this does NOT make sense to me. I have a resistor before the circuit, lets say from an Arduino 5V, that drops 3V (to give 2V to the LEDs) at 15mA, so 200 Ohms. This is what I dont understand: Wouldn't the current be shared between the two, giving 7.5mA to each? What is the usage of the 'voltage versus current' graph? My guess is to show what equal lighting takes.
Hopefully someone could explain where my understanding went wrong, am I not factoring in LED resistance, or do they follow strange rules?


texts: Erasing Flash with X-rays to remove security bits

texts:
Scenario: A chip is read/write protected by programming a security bit in its onboard flash memory. Normally this would mean it cannot be re-written. Would a dose of X-rays be capable of erasing the flash to the extent the part could be reprogrammed? So, a number of questions.

a) How much X-ray flux is required?

b) Are such X-ray sources easily available?

c) Would the X-ray flux cause permanent damage to the chip?

d) Has this been done by anyone?


texts:
To use an ATX supply outside of a PC while preventing output voltage to run away at low/no load, can I just use a couple of diodes in series to provide some kind of voltage-dependent load?

Like:

simulate this circuit – Schematic created using CircuitLab

The idea is simply to have a base load which limits the output voltage to some level so as to not damage the PSU. The no-load output voltage for my appliance is not critical.


texts: What indicates a capacitor being charged or discharge in a circuit

texts:
I am having troubles determining when a capacitor is being charged or being discharged, never understood the concept when a capacitor is under going that process besides the fact when a Source is connected to a cap it will charged to said source, and once removed it will start discharging.

I am talking about more complicated circuit such as ones below.

Circuit Diagram: being questioned

simulate this circuit – Schematic created using CircuitLab

Positive Cycle Analysis :

simulate this circuit

Negative Cycle analysis

simulate this circuit

I understand the positive cycle is charging the capacitor through R1, and R2, however for the negative Cycle I have no idea what that capacitor is doing? I am not even sure if this analysis is right, but this is the only thing that makes sense to me.

This is suppose to be a rectifier circuit, where it charges on every cycle I guess? So maybe the negative cycle is charging the cap as well, but when is it being discharge?

I guess what I am trying to ask if that if a cap is charging or discharging How do one find the path it takes to be charged/discharge.

EDIT: With a bit more thinking I figured the capacitor is both charging and discharging in the same cycle both postive and negative. I am still confused on which path current takes for discharging, and charging. For example if you look at the positive cycle and its discharging, is the current flow opposite and if so does that make the diode forward bias again thus changing the topology of the circuit?


texts: How to modify an existing part in an installed integrated library in Altium designer?

texts: I'm new to PCB design, I'm using Altium to design a PCB. I have installed a few useful libraries. Sometimes in my design I find that a part is not exactly what I want, it needs some modifications. Is it possible to make changes to the library and then immediately use it? When I open the integrated library It asks me to extract it, then I compile it and reinstall the library! I'm sure I'm doing it the wrong way.


texts:
I have to add driving/dimming circuit to the design based on NHD-1.8-128160EF-SSXN-F display. The schematics suggested by the manufacturer is practically taken from MIC2289 datasheet (Figure 4-4).

Now, I do not have experience with backlight, but it seems to me that their choice of a driver is far from optimal. First, MIC2289 is a booster designed to drive up to 34V diodes in series, while the display has five LEDs in parallel. Second, the chip requires external components for soft-start, while many of the alternatives have that built-in.

While looking through LED drivers at digikey I realized that this particular application falls into weird "grey area" because of the way the LEDs are connected. The majority of chips are either step-ups designed to drive series of diodes from single lithium battery in mobile applications, or step-downs designed for higher voltage sources in lighting/automotive applications.

The display datasheet says backlight should be driven by constant current 100mA and "for the reference only" implies that this would require 2.8V to 3.4V. In my case there is 3.3V available from on-board DC-DC, which falls smack-dab in that range. So, any step-up seems to be wrong, for that potential 0.1V difference. Step-downs could be OK, but I don't know if they really necessary. There are some linear chips like BCR421U that can do the job just fine with only one external resistor, while dissipating 0.05 Watt in the worst case and supporting nice 25kHz PWM dimming.

QUESTION: Which driver topology would you recommend? Do you know of any drivers better suitable for this application and requiring minimum external components?


texts: Are SMT components bad for high voltage applications?

texts:
Majority of the assembly factories are asking for SMT jobs. My gut tells me through hole would be a better option for a high voltage application.

Before the high voltage project is started, we need to make a call on SMT or Through hole parts.

Is there a study on this?

High Voltage application I mean : 3Phase 480v systems. The electronics will be in place to monitor loads and drive a bunch of 24v relays.


texts: Which electrode is anode and which cathode in a plasma reactor with high-voltage DC power supply?

texts: Which electrode is anode and which cathode in a set-up like this (plasma reactor)? Or, what is high-voltage sharp electrode - anode or cathode?


texts: Will a 6 volt LED kill a 9 volt battery quickly?

texts: I am building a little circuit and I am adding a little 6 volt LED to tell me when I have power going through. But my power source is a little 9 volt battery, will this LED kill this battery quickly? I want it to last, will I be okay?


texts: I'm trying to determine the Thevenin voltage of a circuit using the node voltage method

texts:
I'm trying to determine the Thevenin voltage between the terminals a and b on this circuit:

Notice that I've named the three essential nodes \$v_1\$, \$v_2\$ and \$v_3\$. I've highlighted the ground node to the far left. Using the node voltage method, I produced these three equations.

$$v_1: \frac{v_1-600}{10} + \frac{v_1 - v_2}{40} = 0$$
$$v_2: \frac{v_2}{14} + \frac{v_2-v_1}{40} + \frac{v_2 - v_3}{2} = 0$$
$$v_3: \frac{v_3 - v_2}{2} - 12 = 0$$

According to my logic, the Thevenin voltage should equal \$v_1-v_3\$. After solving the system of equations, I got \$270\$V. However, this voltage is not the voltage it's supposed to be, which is \$246\$V. Does anyone know where I got it wrong?


texts: Weird waveforms for a transmitter circuit

texts:
My book about digital logics ("Digital systems" of Ronald Tocci) provides a waveform which seems illogical to me about a transmitter circuit. This is the diagram of the circuit:

The inputs for the waveforms are [A] (0011), [B] (0110), [C] (1001), [D] (0111).
However, the outputs:

At the O3, I believe it must be 1110 instead of 0111 in the picture because the LSD always comes first to Z.


texts:
Moisture Sensitivity Level (MSL) relates to the packaging and handling precautions for some semiconductors.

Components with an MSL of 1 have an unlimited floor life, whereas components with an MSL of 6 must be baked before use to remove excess moisture. More info here: https://en.wikipedia.org/wiki/Moisture_sensitivity_level

I have found this document from LT giving examples of parts ranging between MSL 1 and MSL 4, but I have been unable to find any parts with an MSL of 5 or 6.
http://cds.linear.com/docs/en/quality/MSL-PACKAGE_26Apr2016.pdf

My questions:

Are MSL’s of 5 and 6 never used and just included in the standard for completeness?
If there are parts with MSL’s of 5 and 6, I am curious to see examples.

Thanks


texts: How good is the Paracord 550 as an electrical insulator?

texts:
So following wikipedia the Parachute cord 550 is made from nylon Kernmantle rope, however this site where I sourced the cables from says that it is made of a Polyester sleeve (outer layer) and a core of Nylon draden.

People are using it for cable sleeves, but I want to be sure how good of an insulator it is. My use case is basically the above, using it as a cable sleeve to mod a mouse and make the cable basically more flexible and lighter, however my cable route for my mouse is below the circuit board so the mouse button which is basically an Omron switch has it's soldered pins there (6 of them in like a 1 cm square region) and it will be basically touching the cable. Here is a picture of it:

Should I cut the paracord shorter to start just before it leaves the mouse where no pins are located, or there is no problem leaving it likes this? Not many mice route it below the circuit board where it touches and contacts  pins, however I am assuming that it would've been already thought about accidental touchings. So my biggest gripe is that I am not sure if the materials used are good conductors.


texts: What would i change about this diagram to power and regulate this motor to make this a working model

texts:
what if the battery was 12v? would this be a working model? a previous comment suggested a BJT, and to regulate the BJT with a potentiometer.. what is a BJT?

i am looking to get as small of components as possible as to fit in a plastic case ( aren't we all lol)...

i would also like to know if there are any other components i would need to run the mini digi voltmeter

Basically trying to make a regulated battery with a on off switch to run this tiny motor...


texts: How do I modify a small blower motor to be variable speed?

texts: I have a small blower motor 120 v, 1.87 amps, and I want to make it variable speed. I hooked up a dimmer switch for a light bulb but it did not work very well. I went to a electronics store and they wanted to sell me a $150 item but could not tell me why the dimmer switch would not work. A friend told me I needed a variable resistor good for 0 to 3 amps not 0 to 15 like the one I am using. I have no idea. Can someone at least tell me why the dimmer switch doesn't work, in layman's terms?


texts: Speed of Synchronous motor determined by frequency, but how about current?

texts:
The speed of a permanent magnet synchronous motor is determined by

  n = 120f/p

where f is frequency, n is speed in rpm and p is number of poles.
p is fixed in a motor so changing the frequency changes the speed.

But if I have a 4 pole motor and I set the frequency to 50Hz I get 1500rpm.

Does this mean the amplitude of the current does not matter at all?
(I know that torque is determined by current and flux per pole but my question is merely about speed of the motor)


texts:
I'm a novice when it come to electrical engineering and I may be missing a few key concepts but I'll try my best to respond to questions.

I have a "Low Cost 10-Bit Monolothic D/A Converter" (AD561J) that is in an arcade unit. I am attempting to inspect the data coming into the DAC using a logic analyzer with 8 leads. I'll have to do this for another DAC on the board which has an identical configuration.

What is the best way to convert these 10-bits that come in at the same time into a binary stream that I can then inspect with my logic analyzer?

DACY# correspond to the input pins. For example:

 DACY1 - 0
 DACY2 - 1
 DACY3 - 1
 DACY4 - 0
 DACY5 - 1
 DACY6 - 0
 DACY7 - 1
 DACY8 - 0
 DACY9 - 1
DACY10 - 1

And the output:

0110101011

Preferably as soon as all 10 inputs have been received. Looking at the datasheet for the DAC I don't see a clock input. How does the DAC know when to output the correct voltage, or is it always fluctuating as new bits come down the pipe?

Bottom line: How can I turn 10 digital inputs into one binary output, preserving the bit significance order?

Any help would be greatly appreciated!


texts: Will this power selection, soft power latching, buck cicuit work?

texts:
I designed power part of my circuit, but don't know will it work as I expected.

This circuit should auto switch power between VBUS and VBAT (VBUS preferred), after power selection it should step-down voltage to 3.3v and it should work as soft power latch.
There are few pins that should be connected to the MCU (nrf52):

BTN_SENS should be connected to the MCU pin with intenal pull-down resistor.
If at the moment of press everything was off, press should cause the step-down conveter to turn on, then the controller should turn on and send a high signal to the HOLD pin.
If at the moment of press everything already on, latch button should act as ordinary button.

VBAT_SENS should be connected to ADC MCU pin. This pin is responsible for monitoring the battery level.

HOLD should be connected to any of MCU pin.

Will this schema work as expected? Thanks.


texts: How to get 12V from (automotive) 7V to 42V?

texts:
I'm trying to design a circuit that is supplied with a voltage between 7V to 30V (12V battery) and needs to output 12V @100mA.

How can I implement it?
Do I have to use an DC-DC (step-up/boost) converter?


texts: How can I make Verilog HDL ModelSim test bench for a simple ripple adder circuit output an addition table instead of a long list of every calculation?

texts:
I've completed my assignment and I'd like to make the output look something like this, with one table for sum output and one table for carry output:
Sum:
    1  2  3  4  5  6  7  8  9  10 11 12 13 14 15
    __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
1 | 2  3  4  5  6  7  8  9  10 11 12 13 14 15 16
2 | 3  4  5  6  7  8  9  10 11 12 13 14 15 16 17
3 | 4  5  6  7  8  9  10 11 12 13 14 15 16 17 18
4 | 5  6  7  8  9  10 11 12 13 14 15 16 17 18 19
...
15| 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Is this something that could be easily achievable?
Here's my main file, RCA.v:
module RCA(CIN,A,B,S,C);

    input CIN;
    input wire [3:0] A,B;
    output wire [4:0] S;
    output wire [3:0] C;

    CA bit0 (CIN, A[0], B[0], S[0], C[0]);
    CA bit1 (C[0], A[1], B[1], S[1], C[1]);
    CA bit2 (C[1], A[2], B[2], S[2], C[2]);
    CA bit3 (C[2], A[3], B[3], S[3], C[3]);
    assign S[4] = C[3];

endmodule

module CA(cIn,a,b,s,cOut);

    input a,b,cIn;
    output s,cOut;

    assign cOut = (a & b)|((a ^ b) & cIn);

    assign s = (cIn ^ (a ^ b));

endmodule

And this is my current testbench file, tb_RCA.v:
`timescale 1ns / 1ps

module tb_RCA ();
    reg [3:0] A;
    reg [3:0] B;
    reg CIN;
    wire [4:0] S;
    wire [3:0] C;

integer i;

RCA uut (
    .A(A),
    .B(B),
    .S(S),
    .C(C),
    .CIN(CIN)
);

initial begin
    for(i=0; i < 2**8; i = i+1) begin
        {A,B} = i;
        CIN = 0;
        #5;
        $display( "%d + %d = %d | %d", A, B, S, C );
        #5;
    end
end

endmodule

The testbench output looks like this right now, where the first two numbers are each number to be summed, followed by the sum and the carry bit at the end:
 0 +  0 =  0 |  0
 0 +  1 =  1 |  0
 0 +  2 =  2 |  0
...
15 + 13 = 28 | 15
15 + 14 = 29 | 14
15 + 15 = 30 | 15

I'm not very experienced with programming, but I know enough to at least get me this far. I think that this could be fun to learn. Any guidance or references to external instructions would be greatly appreciated. I would also appreciate any comments on what I have presented here that could help me write better Verilog code.
Thanks!


texts: I desoldered a bunch of connectors (out of a Baird VHS player IIRC) long ago and never made an effort to find out what they are. The only markings I can find on them are a very faint SMK on the underside of the moulding. I looked around SMK's website but they only show current products. Is there a legacy datasheet/series identifier for these connectors? I'd like to at least try and get hold of some wire-end parts to recycle the collection of PCB ends that I have.


texts:
I'm designing a board with a GSM modem, and the plan is to hook this up to an SMA connector and thence to an external antenna which will live outside the metal enclosure. I'm aware of the need to observe impedance rules for the CPW track that does this, but it's my first time doing this and I'm outside my comfort zone. I'd also like to minimise the radiated emissions from the CPW as there's some delicate ADCs on board. So any observations or advice would be appreciated.

The circuit looks like this:

I'd like to use 0603 and 0402 parts for the matching components, so my current PCB layout is:

The track width and gap size are from the online calculator

To get the required dielectric thickness, I had to skip the L2 copper and go to L3 for a ground plane. This is not ideal, as L2 is in fact my ground plane and L3 is signal, but I can put plenty of ground on L3 under this area. The bottom layer L4 is also ground.

So this is my layup info:

And my L2 looks like this

So firstly, have I got this right?

Secondly, if I rotate the GSM module, I could have a much shorter CPW. Would this be advantageous in reducing the emissions from it?

All advice much appreciated.


texts: USB 3.1 AC Coupling Capacitor Implementation

texts:
How should the AC coupling should be implemented when connecting a USB 3.1 hub to a USB Type-C connector through a MUX. Is it:

Both sides of each MUX.

On the switched output of each MUX.

On the input to each MUX.

I think it should be option 2, however, the capacitors should be placed close to the SSTX pins of the hub.


texts: A question about the exact formula for the collector current

texts:
Regarding the collector current Ic equation in the below figure:

The above figure tells:

Ic = Is * (exp(Vbe/Ut)-1)

But I thought it should be:

Ic = α * Is * (exp(Vbe/Ut)-1) + Icbo

1-) Is α and Icbo neglected in the figure?

2-) Is the reverse saturation current Is the reverse saturation current between the base-emitter junction? Is Is that the same thing called Ieo in some texts?


texts: I have two pieces of hardware I'd like to interface with via USB. The first are 2002 Series Actuated Valves and the second is a Mass-Flo Controller for regulating gas exchange. To my (admittedly limited) knowledge of hardware interfacing, I imagine for example, as stated on page 38 of the MKS manual, I simply need to "apply a TTL low to pin 4" of the 15-pin connector to open the valve. I've purchased the following USB-DB25/DB15 cables, however am unsure of exactly how to apply this signal voltage through USB. The manufacturers sell their own cables like a DB15 to HD15/VGA but their prices seem a tad outrageous and the shipping times won't work. How can I achieve this task through USB?


texts:
When it comes to (synchronously) resetting registers in HDL (I'll use Verilog), is it considered bad practice to code the reset combinatorially? As far as I can tell, the following two snippets are functionally equivalent.

Behavioral:

always @ (posedge clk) begin
    if (rst) current_val <= 1'b0;
    else     current_val <= din;
end

Structural:

assign next_val = (rst == 1'b0) ? din : 1'b0;
always @ (posedge clk) begin
    current_val <= next_val;
end

I learned to write the logic the behavioral way, and only recently came across the second. In terms of HDL convention/best practices, is one preferrable to the other? Also, would they be mapped to different hardware?


texts:
I am trying to build a keyboard sewn into a shirt and since there doesn't seem to be any suitable flat (and thin) pressure switches I will need to DIY one. Here is my idea for a pressure plate viewed from the side:

The orange parts are conductive layers and the grey ones are some form of elastomers (perhaps rubber?) to push the conductors apart. When the user touches the plate the conductive layers meet and form a circuit.

What is the best material for the conductive layers? Copper?
How many cycles can I expect before the sensor breaks?
Do I need to worry about tinpest, oxidation or similar problems?
Is it better to use high or low voltage? Would 3v work?

My biggest worry is durability since I know that making a good, tough switch is hard. Obviously a hall effect sensor would be the best choice but I don't think it would work on such a small scale.

Another approach is to use conductive fabric like this: http://www.instructables.com/id/Three-Fabric-Buttons/step4/Making-holes/

Would that be more durable compared to my idea?

Or are there any better ways to solve this problem? At first I looked into piezo transducers but they can only detect taps and I need to know if the user is holding down a button.


texts:
I have assembled a diy m590e gsm gprs module kit, bought from Amazon. The seller provided image is:

The Schematic used to assemble the kit is:

I connected it to the Laptop using a CP2102 based USB to TTL converter:

GSM Module    CP2102 Module
 GND           GND
 RXD           TXD
 TXD           RXD
 VCC           5V

Then after opening putty, the output from the serial reads as:

at
OK

at+cpas
+CPAS: 0

OK

MODEM:STARTUP

+PBREADY

MODEM:STARTUP

+PBREADY

MODEM:STARTUP

+PBREADY

MODEM:STARTUP

...

However, on powering up without sim card, the modem acts normally without getting into the loop.

The SIM Card used is Airtel Prepaid.


texts: How to using a 3.5 mm stereo plug mic with a EM11G LM 386N-1 amplifier

texts:
I have built a simple amplifier circuit using a EM11G LM 386N-1 amplifier chip which follows the following design (cap and resister values are slightly different):

I connected this mic to the circuit, and the circuit produce some good sound in a pair of headphones:

VideoSecu High Sensitive Preamp Mini Audio Pickup Tiny Spy Microphone with Power Bypass for Security Audio Sound Voice Monitoring Recording and bonus Warning Decal WD4

After this mic was damaged, I tried to replace it with this mic:

Sound Tech CM-1000 Table Top Conference Meeting Microphone with Omni-Directional Stereo 3.5mm Plug

I connect it so that the left and right channel are connected to the 'input' and the ground ring is connect to the common ground.

The new mic does not work in this configuration.  The sound that should be picked up by this mic is not coming out of the headphones, not even slightly.  If I listen closely, I think I can hear a faint radio station, but that's it.  I know that the mic is working because I plugged it into a voice recorded and tested it.  No problems.

Is there something that the voice recorded is doing differently to cause the mic to work? How do I need to change the circuit so that the mic will be heard?

Edit: Would adding a preamp like this (between the mic and 386N) possibly correct the problem?


texts:
I am planning to design a 65W power supply which will use a PWM frequency of around 100kHz. I am specifically concerned about conducted EMI (not as much about radiated for now). I am currently considering using the following to lower my EMI:

LC ladder filter
Common-Mode choke (using 2 inductors)

Knowing this, if I chose to ignore efficiency, wouldn't is be better to you a higher frequency? If I choose a higher PWM frequency (say 1MHz), wouldn't have lower conducted emissions?


texts: Replacing a 12v battery (model A23) with power pack

texts:
I have a fan RF remote which runs using the a small 12v A23 battery. Note this is not 23 Amps but the battery model. They can provide something like 50mAh and are quite small.

I am hacking the remote for use with a home automation system however have been unable to run it free of the battery. I have tried connecting the battery terminals up to a 12V 2A power supply however it blew up the remote (capacitors I think) and made a burning smell.

I had a few of them so assuming I must has used the incorrect polarity I exploded another remote.

I am totally at a loss why I cannot run this from a power back, and the only working theory I have is a minimum power draw for my 12v 2Amp supply?

Does anyone have any other ideas?

Should I risk my last remote on a smaller power pack, say a 12v 600mAh?


texts: Where can I buy a finished mobile camera module?

texts:
I am interested in buying a really small camera module for one of my projects. I know I can buy some iPhone/Samsung camera replacements on Ebay. But I have no information on their connectors and interfacing mechanisms.

Does anyone knows of a merchant/vendor/manufacturer of a complete camera on chip system with the lens and datasheet that gives examples on how to interface with it?


texts:
According to Wikipedia,

The reason that a tunnel diode conducts current in reverse direction is :

1)In the tunnel diode, the dopant concentrations in the p and n layers are increased to the point where the reverse breakdown voltage becomes zero and the diode conducts in the reverse direction.

2)Quantum Tunneling : Under reverse bias, filled states on the p-side become increasingly aligned with empty states on the n-side and electrons now tunnel through the pn junction barrier in reverse direction.

Which is the more appropriate and more dominant reason, i.e. which effect contributes more current ?


texts: Can I get 2 AA to provide 4+ amp pulses at 5V?

texts:
I can find plenty of circuits that can boost 1-3V to 5V at low 200mA ranges, but nothing that would allow for a powerful burst, like IR remote at high power, needing 30-50ms pulses of 4A at 5V, then back to idling at 100mA or less...

What is the minimum number of AA battery possible to achieve this?

Any existing IC from any manufacturer, or is it a custom circuit design?

I currently use Li-Ion, but want to make removable disposable battery and light weight.


texts: Why can't i calculate the Inductive reactance in this way?

texts:
Question:

\$V_1=40sin(1000t)\$,what is the value of  Inductive reactance?

Solution :

\$Z=\frac{V_1}{I}=\frac{40}{8}=5\$,so \$5=\sqrt{R^2+X^2_L}=\sqrt{4^2+X^2_L}\$,so \$X_L=3\$

But i want to ask that why can't i calculate the Inductive reactance  in this way below?

My thinking:

\$Z=4+jX_L\$, and \$Z=\frac{V_1}{I}=\frac{40}{8}=5\$,so \$5=4+jX_L\$,then \$1=jX_L\$,so \$X_L=\frac{1}{j}\$ ,why will i get the wrong answer with this method? what is the problem of this method?


texts: What is the point of converting everything to NAND/NOR and how do you do it right?

texts:
The title pretty much says it all. I know that A' + B' = (AB)' is the basic transformation needed to do so (at least for NAND gates), but whenever I apply this I feel like I'm doing it wrong. For example:

C' + AB' + A'BD'

Here's what I did:

I took - C' + AB' - and made it into - (CA'B)' -

which reduced the problem to:

(CA'B)' + A'BD'

Which further reduced down to:

((CA'B)')'(AB'D)'

Is this the right way to do this? Also, why is this form sometimes wanted? It seems more complicated than the original form.


texts:
In order to work on programming a DDR3 SDRAM, I was going through the JEDEC standard DDR3 SDRAM specification (link to pdf, pg 30).
I got a bit confused about the DDR3 addressing, a snapshot of which is below

Correct me if I am wrong. 512Mb corresponds to the total number of bits that SDRAM can store. There can be 3 configuration in which data can be stored, 128Mb x 4, 64Mb x 8, 32Mb x 16.
The 4, 8 & 16 in the above configuration I think is the length of each location in SDRAM, ie, in in 128Mb x 4 configuration, there will be 128Mb location each of 4 bits. Similarly for the other 2 configuration.

What I dont understand is that DDR3 SDRAM has 64 data I/Os namely DDR_DQ pins. So why is that there is no configuration like 8Mb x 64 to utilise all the 64 I/O pins of data?

Or have I figured it out completely wrong?


texts: Is this Radio Frequency and will it work?

texts:
I really don't understand radio-frequency and how it works, and I get very confused on the theory and how an antenna etc. works. I first start with the electrical transformer. Energy is transferred through the magnetic field transferring the AC power to the LED without touching the wire.

Then, the inductors loose a core and are moved farther apart. I still got the LED to light up at <2 Cm.

Last, Now, I want it even further. I know the energy can't travel too far, so I have to AMPLIFY it in some way. I amplify it in half-wave rectification (wouldn't need full for the LED anyway) and then I estimate the LED will turn on. I use a BJT. I think this will work but I am not sure and am not the expert in electronics. Is this RF? I understand the coil thing with electromagnets but why would an antenna be used because that is not a closed circuit and just one wire going in the air. Is it something to just expand the magnetic field and is it just attached to the inductor or something? Here is the circuit, again I don't know if it will work and I need advice. I just want it to be turning the led off or on depending if there is the AC voltage on or off.


texts: How to change logic when system shuts down

texts:
I try to think on a good way to control motor when I shut down the main PCB (which includes the MCU).

How the system works today is when it's ON, the MCU enables the motor, the motor moves a mechanical part which presses on a push button and "lock" it (gives the MCU the sign to disable motor).

I would like your help to think on a way to return the motor to his normal state after I turn off the system and the MCU no longer have voltage.

What I was thinking on is another small PCB circuit that will connect to the same motor and another push button. The small PCB will always get voltage and when system turns off, it will "recognize" it, maybe using a transistor base (please advise if possible), turn the motor to the other way and press the other push button- which will stop the motor from moving.

Other suggestion is somehow "delay" the "shut down" after moving the "shut down" switch and give a few second to the MCU to keep work, activate the motor to the other way and then turn it off.

I would appreciate any kind of help to that hard problem.

Added in edit:

The MCU controls the motor driver which controls the Motor using A and B nets. If "10" is send, motor switch to one direction,  if "01" it switched to the other direction and if "00" then it stops. The system start by moving the motor, let say with "10", until a mechanical part pressing the "open motor" button, which tells the MCU to stop motor ("00"). My problem is, that I want somehow, that when I completely shut down the voltage, the motor will move to the other way until it presses the other button ("close motor" button) and then stop moving. How can I in the most simple and low cost way you can think of?

I was thinking on adding another PCB which will always get voltage from batteries, connect to shutdown switch, A and B nets and close motor button. How can I make such PCB do the trick and close it?

Thanks,


texts: Verilog - Use integer constant to define signal width

texts:
I have a module which takes two parameters, ParameterOne and ParameterTwo. I use their ratio a lot, so I gave it a name const integer Ratio = ParameterOne/ParameterTwo.
I want to have a signal whose width is this ratio, so I defined a signal logic [Ratio-1:0] wires. However, I get the error message Range must be bounded by constant expressions. This leaves me perplexed, as this range is bounded by a constant expression (I explicitly declare it to be const).
Does anyone here know why it's complaining about this code?


texts:
We are designing a 868MHz keyfob, which is transmitting in a band with a 1% duty-cycle limit.

According to the ETSI EN 300 220-1 standard section 5.4,  the duty-cycle should be measured for a period of 1 hour.
In normal use, the keyfob will transmit well below 1% duty-cycle. But if some user activates the keyfob rapidly for a long period, the 1% duty-cycle will be violated.

Section 5.4.2 of the standard states that the representative period should be the most active in normal use, so does this mean, that we do not need to make some algorithm, that would block transmissions, if a user activates the keyfob more than intended. ?


texts: Is BJT a Voltage controlled device or Current controlled device?

texts: I have searched already for this question, but everywhere I see debate instead of clear answer. Though it is not that important of a matter whether we call it a voltage controlled device or current controlled device. I believe it can be called both voltage controlled or current controlled depending on the situation. Still I believe it requires a little clarification. Which part it really is in view of the core operating principle?


texts:
I'm new to arduino and RF modules so I bought some cheap set (XY-MK-5V and FS1000A) to transfer data between two arduinos. Transmitting the data looks fine to me, but I can't receive any Data so far.

This is my Receiver source. It's connected to pin 11.
 When I start  the receiving board, the TX-LED won't turn off, in case this is important somehow. The RX-LED is off, the TX-LED of my sending arduino is turning on and off when I send a message.

I set my buffer size to the VW_MAX_MESSAGE_LEN (30). I just wan't to transfer "hello" for the first time. Is this the correct setup?

 /*
      SimpleReceive
      This sketch  displays text strings received using VirtualWire
      Connect the Receiver data pin to Arduino pin 11
    */
    #include <VirtualWire.h>

    byte message[VW_MAX_MESSAGE_LEN];    // a buffer to hold the incoming messages
    byte msgLength = VW_MAX_MESSAGE_LEN; // the size of the message

    void setup()
    {
        Serial.begin(9600);
        Serial.println("Ready");

        // Initialize the IO and ISR
        vw_setup(2000);             // Bits per sec
        vw_rx_start();              // Start the receiver
    }

    void loop()
    {
        if (vw_get_message(message, &msgLength)) // Non-blocking
        {
            Serial.print("Got: ");
        for (int i = 0; i < msgLength; i++)
        {
            Serial.write(message[i]);
        }
        Serial.println();
        }
    }

Transmitting Arduino :

/*
  SimpleSend
  This sketch transmits a short text message using the VirtualWire library
  connect the Transmitter data pin to Arduino pin 12
*/

#include <VirtualWire.h>

void setup()
{
    // Initialize the IO and ISR
    vw_setup(2000);           // Bits per sec
    Serial.begin(9600);
        Serial.println("Ready  transmitter");

}

void loop()
{
    send("hello");
    Serial.println("transmitted");
    delay(100);
}

void send (char *message)
{
  vw_send((uint8_t *)message, strlen(message));
  vw_wait_tx(); // Wait until the whole message is gone
}

Ís it possible that the receiving module is not working?


texts: Output of LM393 won't swing LOW unless it is pulled up with a LED

texts:
I built the following circuit using an LM393 as part of a noise gate for audio applications. It's a voltage comparator with hysteresis.

I originally connected a 10 kΩ pull-up resistor and then added a 5 mm UV LED to serve as a visual reference. The circuit worked fine like this, however, if I remove the LED and connect the 10 kΩ pull-up resistor directly to the supply, the output doesn't swing low and gets stuck on its high state.

I've tried adding 1N4148 diodes in anti-parallel to the pull-up resistor, in reverse from the output node to ground, and I also tried substituting the LED with a 1N4148, but neither worked.

Here's a picture of my protoboard with the UV LED:

Here are two oscilloscope captures of the input and output signals:


texts: H-bridge driver circuit where voltage is higher than control ic

texts:
I am using an H-bridge to give a clock time signals.

The H-bridge is controlled from an ESP8266 (Wemos D1 mini board)

The clock requires an 18V signal (alternating every minute for a fraction of a second with very little current).

The ESP8266 has an output of 3.3V on its pins.

I use NPN transistors as level shifters.
The transistors are BC817.
(Collector-emmiter breakdown Voltage 45V)

The whole kicad project can be found on gitlab.

This board manages to kill the ESP8266 boards, even though there shouldn't be a path from the 18V (P1S/P2S) to the ESP.

It works perfectly if I use 5V instead of 18V on P1S/P2S!

I've used my multimeter to measure the current on the 18V wire.

When I increase the voltage (P1S/P2S) to around 8V current starts to flow even if both signals are 0 (H-Bridge-A-Signal and H-Bridge-B-Signal).
Below 8V the current is around ~10µA jumping to >100µA (at ~8V).

I use a DC-DC buck boost converter to get the P1S/P2S voltage using 5V as input.

At 18V the H-Bridge becomes hot really fast.

It is possible that I have damaged the board, as I have attached it to an ESP8266 which had the wrong firmware.

The measured values above are without any connection to an ESP8266 but on my bread-board where only 18V/P1S/P2S, GND and the 2 H-Bridge-*-Signals are connected (both signals to GND).

So my questions are:

Is there anything wrong with my driver circuit?
Is it likely that rebuilding the board fixes my problems?
Do you have any tips / advice for me?

My reasoning:
H-Bridge-A-Signal == GND ⇒ H-Bridge-A == 18V
H-Bridge-B-Signal == GND ⇒ H-Bridge-B == 18V
Both P-channel mosfets are off.  The N-channel mosfets are both on.

H-Bridge-A-Signal == 3.3V ⇒ H-Bridge-A == GND
H-Bridge-B-Signal == GND ⇒ H-Bridge-B == 18V
The P1 channel mosfet is now on (P1G).  The P2 channel mosfet is still off (P2G).
The N1 channel mosfet is now off (N1G).  The N2 channel mosfet is still on (N2G).

I've ordered PCBs from oshpark:


texts: Why is there a need for an eNVM and an eSRAM in the same SoC FPGA

texts: SmartFusion2 SoC FPGA is distinguished by containing an embedded Non-Volatile-Memory (eNVM) that is used to store the code needed for the booting process of the FPGA after power up. So in the presence of this Flash memory why do we still need the eSRAM ?