texts: Chaining 25 74HC595 shift registers together

texts:
Situation:

I am doing a project which requires me to chain 25 74HC595 shift registers together. They ate controlled by an Arduino microcontroller.

Question:

Will it work when chaining that number of shift registers together?
Will there be any problem such as the clock signal false and data transmission errors because of the long transmission distance?
Do I need something like a buffer or capacitor to make sure the transmitted signal is correct? If needed, any recommended type and where to connect them?


texts: LSM6DS33 how to filter accelerometer values even more (< 50Hz)

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I'm trying to use a LSM6DS33 6-axis accelerometer/gyro chip as an inertial navigation aid, participating in sensor fusion. The problem is that the application has large amount of vibrations and the accelerometer data is quite noisy. I need around 25 accelerometer samples per second, so to get a smoother signal I have enabled the analog low-pass filter at the lowest BW = 50Hz and the accelerometer ODR is 104 Hz; I average 4 samples manually whilst reading them to get equivalent ODR of 26 Hz with less aliasing.
This is better than before (when there was no low-pass and at 52 Hz ODR), but there's still some noise (around 0.1g peak-to-peak - measured on a vibrating platform that vibrates at ~65 Hz) present in the resulting averaged samples. I verified that increasing the accelerometer ODR to 208 Hz decreases noise (aliasing) further. 416Hz reduces it even further (0.025g p-p). But that needs more I²C traffic and CPU time, so increasing the ODR will be prohibitive.
My question is: is it possible to set up the LSM6DS33 to sample the accelerometer at 833 Hz, average each 8 samples, and put the results in the FIFO (equivalent 104 ODR)? Or put in other way, to get an equivalent low-pass filtering BW lower than 50 Hz, ideally around 12 Hz?
For reference, my current config is:

CTRL1_XL = 0x4F; // acc setup -> 104 Hz, 8 g full scale, 50Hz bandwidth
CTRL2_G = 0x4C; // gyro setup -> 104 Hz, 2000 dps full scale
CTRL3_C = 0x44;  // set BDU (block data update) bit high
CTRL4_C = 0x81;  // enable FIFO length limit; XL_BW_SCAL_ODR=1
... (and also some unrelated code for setting up the FIFO).


texts: Circuit analysis technique, is there a different way to solve the question?

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The above question I solved it as follows:

But, I noticed the following:

Is there a different method to solve this question?


texts: Reverse Polarity & Load Dump Protection (TVS)

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Based on this and other material I’ve read, I should have a diode for reverse polarity protection and a TVS for load-dump protection in an automotive circuit. I have prototyped the circuit and its associated load (an ATtiny85 at NODE1) without the diodes and everything works as desired, but I want to add appropriate protection.  I would like the circuit to be compatible with both 12V (~14V) and 24V (~28V) automobiles with replacement of the TVS.  I believe D2 could be one of any number of diodes like the 1N4148 shown or a 1N400x series diode.  Because I don’t want any voltage leaking past D1 under normal conditions, I think a P6KE18A (VR = 15.3V) would work for a 12V system and a P6KE36A (VR = 30.8V) for a 24V system.

Do those diodes seem reasonable?
Is there a better approach or different values I should use?
With 28V approaching the 30V max input of the LP2950, should I also consider something else to lower the input voltage of the 2950?

simulate this circuit – Schematic created using CircuitLab

How to select power line polarity protection diodes
http://www.eetimes.com/document.asp?doc_id=1279734

Transient Voltage Suppressors (TVS) for Automotive Electronic Protection
http://www.vishay.com/docs/88490/tvs.pdf

Fairchild TVS Data Sheet
http://www.farnell.com/datasheets/1725637.pdf?_ga=1.259177292.759527797.1468595075

How do I protect against an automotive load dump?
How do I protect against an automotive load dump?


texts: Debugging a LPC23XX based CAN bus sniffer

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I am trying to get a CAN bus sniffer working, based on LPC2368. I keep getting a bus error interrupt, of type "form error". I suspect my timing settings. I verified that the sending party is transmitting at 125 kbit/s (8 μs bit duration). Here is my setting for a 72 MHz CPU clock and 125 kbit/s bus speed:

#define PULSE_BEFORE_SAMPLE 8
#define PULSE_AFTER_SAMPLE 3
#define PULSE_PER_BIT (PULSE_BEFORE_SAMPLE + PULSE_AFTER_SAMPLE + 1)
#define TSEG1 (PULSE_BEFORE_SAMPLE - 1)
#define TSEG2 (PULSE_AFTER_SAMPLE - 1)
#define SJW 3 //sync jump width
#define SAM 0 //sampling 0=single sample 1=triple sample

#define CAN_PRESCALER 7 //((CPU_CLK_HZ / PCLK_DIVIDER / CAN1_BAUDRATE / PULSE_PER_BIT) - 1 )
...
PCLKSEL0 |= PCLK_CAN1 << 26; //clock source = CCLK/6
...
CAN1BTR = (CAN_PRESCALER | (SJW << 14) | (TSEG1 << 16) | (TSEG2 << 20) | (SAM << 23));

Am I making an obvious mistake here? The controller is running in listen-only mode, all other mode bits are set to 0.


texts: Center tap transformer. Voltages 180 out of phase but what about direction of current in 2 parts?

texts: In the center tap transformer (attached picture), my understanding is that volatges in 2 parts in secondary coil would be 180 out of phase. I want to understand the direction of current in both the parts. Will the direction of current in Part 11 would be same as Part 1.? If yes how does that reconcile with voltages being out of phase by 180 in both the parts.?


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I'm working on a photodiode circuit which has been designed by someone else a few years ago.

The basics of the circuit seem simple enough, photodiode to op-amp, op-amp to ADC, ADC to FPGA.

The circuit has worked on and off for a while and everyone has always told me "It's the photodiode, just swap the photodiode and it works usually".

However looking at the actual circuit something doesn't make sense. I've always read/seen that a transimpedance amplifier always has the photodiode as shown in the picture below.

The circuit I have has the photodiode connected in the opposite direction.

simulate this circuit – Schematic created using CircuitLab

What would connecting the photodiode in this orientation do?
Is there a reason why you would do it this way?
Could I flip the photodiode round or will I need to change the whole circuit?

Edit:

I've added the full section of the concerning circuit incase it's needed at all

Op-amp supply rails:

ISL2812: -38V   +2V
AD8676:  -2V    +10V


texts: make motor ON and OFF for fixed interval of time

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I am new to electronic, studied this subject long time back but now not able to recall anything out of it. I have requirement to ON the motor after fix interval of 4 hours and run it for 30 seconds and turn it OFF, this cycle will repeat as long as power supply is maintained, I gone through some of the web links where they had explained the use of 555 and 4060B for this perpose, they also have suggestion to use microcontroller for this. I need cheapest possible solution for this.

I will be thankful if someone help me on this.


texts: How much Ampere is displayed on the multimeter?

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here is a picture of a multimeter:

the display shows: 02,0
is it 2A or 2mA ?


texts:
I'm trying to replace a relay with a SPDT cmos analog switch MAX4678 for switching a sine wave, The switch is powered with dual power supply +5/-5 and +5 to its V_logic pin.

This is what i got in mind:

I tried the two setups and both of the works but which one is better and has low distortion ?


texts: Circuit with coupled inductors, need help with mesh equations

texts: Are the mesh equations in the image below correct? It gets a little tricky with the mutual inductance and my textbook gives no solution (American textbooks..). Click the image below for a larger view.


texts: Antenna Theory and Electron Paramagnetic Resonance

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Hi I am trying to understand why and how Antenna Theory works as it does.

I can only link Antenna Theory to Electron Paramagnetic Resonance @ 2.8Ghz but I do not know how I can link the resonant movement of Electrons in the Antenna.

Can anyone give me more information on where I may look to try to answer my questions?


texts: How do brushless motors provide more torque and longer battery life to cordless drills?

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I was in the market for a cordless drill and came across a drill manufacturer claiming higher torque and longer battery life since it utilized a brushless motor.

Is it true that brushless motors tend to have higher torque than their brushed counterparts? I'm assuming that the efficiency of such motors would be higher as well resulting in longer battery life.


texts: Modelling a positive edge triggered T flip flop with asynchronous clear

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I am modelling a positive edge triggered T flip flop with asynchronous clear. Here is the code :
module t_flip_flop_exam (q,clk,clear,t);
  input t ;
  input clk;
  input clear;
  output reg q ;
  reg internal_t;
  always @ (clear)begin
    if (clear==1)
      q=0;
    else
      q=q;
  end
  always @ (posedge clk)begin
        if (t==1)
          q=~q;
        else
          q=q;

  end

endmodule

Is this is an efficient code?  Is it ok to have to separate always blocks, or is there is a way to include both the clear and the clk signals behavioral code in a single always block?


texts:
I recently bought an SBC8100 plus board

The board uses a MINI8510 board. Now I want to connect to its jtag interface. On the image of the previous link it is the yellow connector, labeled as CN3 which is described as a "10-pin 1.0mm pitch connector".

The JTAG schematic:

The fact is that I'm fairly new to all this connector-cables stuff, and i can't figure out which kind of connector should i buy or where to buy it.


texts: Amplifier output goes haywire with load attached

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I'm trying to create an op amp using FETs and BJTs.  I need the gain to be over 500, currently without a load attached I have the gain about 1000.  The input is a 0.05V sine wave, the output is beautiful as you can see below on the left:

However when I attach a load to the output (40 ohms, which is also the output impedance we are trying to attain), the output goes really haywire as you can see on the right side of the above picture.

The current schematic we have is using a two differential amps with current mirrors, then 3 gain stages using FETS.  It's below:

I'm just wondering whether anyone has any ideas on why the output changes so much with the load attached?  And how to fix the output?  I've been reading into push-pull amplifier circuits as a friend made a suggestion that it might help, would this be the right way to head?


texts:
I am designing a 12-5 V Buck converter on a pcb (as part of a larger design) with a LM2596S-5.0 and using one of the recommended diodes, a 50WQ03.

On the datasheet, both pins 1 & 3 are connected to the anode, and 2 & 4 connected to the cathode, however it looks like 2 isn't able to be connected to the pcb because it is too short and not lowered to the same level as the rest of the pins, as well as not being included on the recommended pcb footprint.

I was wondering if it is in any way advantageous to use both pin 1 & 3 (I am thinking more copper area for heat dissipation), or just one of them, and also what the purpose of a stub pin (not sure if this is the correct name) like pin 2 is?


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Can anyone assist me regarding the design of a circular polarized rectangular patch antenna that is driven at adjacent sides through a power divider?

I already calculated the parameters of the width and length of the patch and the substrate size. However, I am having difficulties calculating the positioning of the microstrip transmission line in order to get a circularly polarized antenna. I am running at a frequency of 915MHz, using FR-4 substrate and a height of 1.6mm.


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I am using Kicad version 4.0.2-stable, which I think is the current version.

I cannot figure out how to get what I presume is the net name GND to “stick” between the schematic editor and the PCB layout editor.

In the first image above, CO2Pad4 is an item I made in the schematic library editor.  It has 4 pins, all labeled ‘1’ and is intended to ultimately represent a soldering pad on the PCB.  Notice that it is connected to GND by wires.

When the net list is created and imported into the PCB layout editor, Pcbnew, Kicad gives it a net name of Net-(CO2Pad4-Pad1) rather than GND.  This prevents the rat’s nest from showing a connection between CO2Pad4 to GND, and thus Kicad will prevent a trace being drawn from the CO2Pad4 to ground.

I have found that in PCB layout editor, Pcbnew, I can change the net name for CO2Pad4 from Net-(CO2Pad4-Pad1) to GND and then the rat’s nest will show a connection.

The problem is that when I make a change to the schematic, Kicad reverses this change.  On a more complicated circuit, I am afraid that I will miss the reversion.

I have tried both local and global labels applied to the wire connecting to CO2Pad4 to no avail.  I thought I had solved it when I applied a global label to a pin on CO2Pad4 (again, all the pins are number '1') and a global label to the wire connecting to the GND symbol on the right side of the first figure.  That worked, until…

I have another, grounded connection pad, CO2Pad2, elsewhere in the circuit.  When I applied the global label GND to one of its pins, Pcbnew applied the net name GND to the second pad, but reverted to Net-(CO2Pad4-Pad1) for the first pad!

Since the local label symbol in the schematic editor indicates that it is a “net name - local label”, I am puzzled as to why this is so hard.

Thanks for any suggestions.


texts:
I think I understand the principle of transistor biasing but i'm a bit lost on forward vs reverse biasing.

Can an EE look at a schematic and tell the biasing of a transistor--reverse/forward?
Or is this something that must be calculated to understand how and where it's occurring?


texts:
So - I have a little situation. I have a MC68000 as my system's main CPU, and a 68008 as my sound CPU to interface with a YM2612 and my RGB video generator. Right now, I'm just going to stop the sub CPU whenever I need to tell it something, but that seems horridly inefficient.

I've programmed the Sega Mega Drive before, and they implement a concept of "Comms RAM" which is basically a part of memory one CPU can write to and the other reads. How would I implement something like this without bus collisions?


texts: What is the power requirement for switching this relay?

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I bought a heavy duty relay to control fluid pumps.  I'll have a 12VDC power source to operate the pumps and I bought the following relay board to control them using an Arduino or other type of board.
https://www.amazon.com/gp/product/B082HKPLFJ/ref=ppx_yo_dt_b_asin_title_o00_s02?ie=UTF8&psc=1
The board with the relays on it would get 12VDC from a separate power supply that also runs the pumps.  The only connection to the Arduino would be to connect from COM to IN1..IN4.
The board has connections on one side as follows:
DC+ DC- CH1 CH2 CH3 CH4 COM
DC+ to the 12V PS
DC- to the 12V PS
CH1..CH4 to Arduino
COM to Arduino.
The Arduino would simply connect COM to CH1..CH4 based on the program it's running.
Q1. does the Arduino have to process 12VDC in order to do this?
Q2. would an Arduino be able to do this?
Q3. if I need the 5V version of this, would the Arduino be able to provide that 5VDC over extended periods of time, say 2 hours?
I just checked the current from COM to CH4 and it's 11 on the 20m scale, so that should be 11mA and 12VDC.  That's the wire I'm asking the Arduino to switch on/off.
Would 12VDC 11mA damage an Arduino if it's asked to switch it on/off?
Note: the Arduino is NOT supplying power to the relay board and the power to the Arduino is a separate supply, it's only doing on/off switching of a wire that has 12VDC and 11mA on it.


texts: Is it feasible to decode an 15 kHz RGB (SCART) signal using a sound card?

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Do you know whether it would be feasible to decode an 15 kHz RGB signal (from a video game console) using a sound card ?

Providing such input can be captured finely enough by a 192 kHz sound card, the decoding process would be done by a software.

I've been trying to find out more information about the encoding of such format such as these diagrams for PAL encoding but I couldn't find any. The only thing that I'm sure about is that since a CVBS signal carrier runs at about 6 MHz there's absolutely no hope of feeding a sound card with it since it is way beyond 192 kHz. But no idea about an RGB signal coming out from the SCART. (a simple thought tends to make me think it would be possible : it runs at 15 kHz)

My questions :

Does an RGB signal really runs at 15 kHz ?
If yes then would some simple components such as resistors be all that is needed to lower the voltage to a value that is acceptable to the sound card input? Or have I missed something?


texts:
I need to simplify the following logic expression:

$$\begin{array}{|c|c|c|c|c|}
\hline
A & B & C & X & SOP \\
\hline
0 & 0 & 0 & 0 & \\
\hline
0 & 0 & 1 & 1 & \overline{A}\ \overline{B}C \\
\hline
0 & 1 & 0 & 1 & \overline AB\overline C\\
\hline
0 & 1 & 1 & 1 & \overline ABC \\
\hline
1 & 0 & 0 & 0 & \\
\hline
1 & 0 & 1 & 1 & A\overline BC\\
\hline
1 & 1 & 0 & 0 &\\
\hline
1 & 1 & 1 & 1 & ABC \\
\hline
\end{array}$$

$$X=\overline{A}\ \overline{B}C+\overline AB\overline C+\overline ABC+A\overline BC+ABC$$

I get the following logic expression after simplification:

$$\begin{aligned}X
&=\overline{A}\ \overline{B}C+\overline AB\overline C+\overline ABC+A\overline BC+ABC\\
&=ABC+\overline ABC+\overline{A}\ \overline{B}C+A\overline BC+\overline AB\overline C\\
&=BC(A+\overline A)+\overline BC(A+\overline A)+\overline AB\overline C\\
&=BC+\overline BC+\overline AB\overline C\\
&=C(B+\overline B)+\overline AB\overline C\\
&=C+\overline AB\overline C
\end{aligned}$$

However, K-MAP and Logic Friday each give me a different answer.

Edit: I changed the SOP, there was a mistake.


texts: Power consumption of unimplemented pins?

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New versions of TI's Code composer studio have a lint-like tool which checks the code and provides recommendations on how to modify the code to decrease power consumption. One of the things I've noticed it complains about is the power consumption of pins which aren't set to low.

What caught my interest was the fact that the microcontrolers I was experimenting with have different number of ports depending on the package and the package I used didn't have the port the tool complained about pinned out. In this particular case, I was using MSP430G2553-IN20 and if my information is correct, the IN20 has same core as other versions, but the port 3 isn't connected to any pins.

So my question is: Are there any ways to estimate the power consumption of unimplemented pins in general?


texts:
I'm trying to replace a part of a circuit with the Thevenin equivalent. I managed to find \$R_{\text{th}}\$, but I'm not sure if my solutions for \$E_{\text{th}}\$ are correct. I have 3 sources, so the logical method for finding \$E_{\text{th}}\$ was the superposition theorem. Here are my results:

Here's the complete circuit:

1) 9V only

So, the voltage between A and B should be:
\$50 + 200 = 250 \Omega\$ and \$350 + 150 = 500 \Omega\$, then \$250 + 500 = 750 \Omega\$. This gives us a voltage of: $$U_{AB} = \frac{9\text{ V} \times 750 \Omega}{500 \Omega + 750 \Omega}$$

which is 5.4V?

2) 5V only

$$(350 + 150) \parallel 500 + 200 = 450 \Omega$$ Then $$U_{AB} = \frac{5V \times 50}{450 + 50} = 0.5\text{ V?}$$

3) 12mA only -- This one is a real problem for me

I solved the resistors the same as in 2), which gives: $$U_{AB} = 50 \times \frac{450 \times 12\text{ mA}}{50 + 50} = 0.54V$$

\$E_{\text{th}} = 6.44\text{ V}\$???

Please help! I'm not sure if this is correct.. Can someone explain how to solve these circuits the right way?


texts: Discontinuity in the charging of an inductor

texts:
I have a buck converter without the output capacitor connected so I would able to see the current of the inductor by the voltage at the load.

I'm using a IR2110 to drive the mosfet.

simulate this circuit – Schematic created using CircuitLab

I have this response:

At the beginning of the cycle there are some peaks those what worse when I increase the load.


texts: Do I have to explicitly connect all pins of the ethernet chip in the FPGA when designing a new controller?

texts:
Regarding the Ethernet peripheral of the Spartan 3E FPGA specifically the SMSC LAN83C185 Ethernet chip. The task is to create our own interface between the PLB and the ethernet chip. So far, I've been basing it on the xps_ethernetlite_v4.00 controller. The physical connections of the controller only shows the MII signals. However, I also saw that there are other pins in the Ethernet chip such like the oscillator, vdd, vss, mode and etc. My question is: are those pins already implicitly connected or do we have to explicitly connect all pins of the ethernet chip?

Second question is, the controller said to send 7 preamble bytes. However, the SMSC datasheet shows that it only receives 2 bytes. Why is that so?


texts: How many I/O pins does this device have?

texts:
Digilent Online Store Page I have attached a link to the digilent store webpage of an FPGA board where the datasheet and schematic can be viewed in PDF's.
I want to know how many free digital I/O pins I have to connect to external devices to not counting the I/O already used for the on board switches, buttons, LED's etc.
I'm guessing its the 4 Pmod connectors leaving me 40 pins to use?


texts: Can SSC be a problem if operating PCIe interface asynchronously through a re-driver?

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I am operating PCIe over copper cables via re-drivers asynchronously. i.e. I only send over the RX/TX data.

The clock is sourced locally at the end point.  For the host root port, I am designing a little PCIe add-in card that will have a PCIe re-driver.

For the add-in card I am wondering if I will need some sort of spread-spectrum clock squelching circuitry.

I am concerned that there will always be some hosts that will not let me turn off the spread-spectrum clocking.

Thank you in advance.


texts: High PCB copper thickness: What are the pitfalls?

texts:
We need to carry high currents on a PCB (~30Amps sustained), so we are likely to order our PCBs with high copper thickness. So far we've only used 35 microns (1 oz) in our designs, so 'high thickness' for us means, 70 (2 oz) or 105 (3 oz).

We do not know what are the things to watch out for with thickness copper. We'd appreciate any experiences. Since this is a very broad topic, I'll go ahead and ask specific questions:

It appears that for a lot of manufacturing houses, 105 microns is as high as its gets. Is that correct or are higher thickness possible?
Can the copper in the inner layers be as thick as the copper at the top and bottom of the board?
If I'm pushing current through several board layers, is it necessary or preferred (or even possible?) to distribute the current as equally as possible throughout the layers?
About the IPC rules regarding trace widths: Do they hold up in real life? For 30 Amps and a 10 degrees temperature rise, if I'm reading the graphs correctly, I need about 11mms of trace width on the top or bottom layer.
When connecting multiple layers of high current traces, what's the better practice: Placing an array or grid of vias close to the current source, or placing the vias throughout the high current trace?


texts: Capacitor Bank Design for Electric Vehicle

texts:
Good day all, I'm toying with the idea of using a small supercapacitor bank to buffer short bursts for acceleration/regen of an electric vehicle (likely an e-bike).

It seems wasteful to put a capacitor bank in parallel with the battery stack (both with independent balancing systems for their respective unit/cell voltages) because the capacitor bank would only provide/accept energy over the small voltage fluctuation when the battery pack provides/accepts current.

What cheap alternatives are there to use the entire capacitor bank capacity over a small voltage fluctuation? An active solution would be a bidirectional DC-DC converter that can fully discharge the capacitor bank when it sees the battery pack voltage sag and then recharge the capacitors when the battery pack voltage jumps up. I imagine this being nonideal though because the DC-DC converter would need to be high power (and therefore heavy/expensive) to handle the relatively infrequent use case of start/stopping.

Edit:

For the sake of making this fun for us engineers let's throw in some numbers with a more likely situation: we want 20kW for 10 seconds to help accelerate an electric car. 200kJ stored in a supercap bank that has a 5Wh/kg density is about 11kg of capacitors, totally reasonable for an EV! This page cites Maxwell's supercaps as capable of charging/discharging in under 10 seconds: https://batteryuniversity.com/learn/article/whats_the_role_of_the_supercapacitor

To highlight the problem, if we have a sad battery pack with 200mOhm of internal DC resistance cough Leaf, a load of 20kW on the battery would still only sag it's voltage from 360V to about 349V so a supercap bank sized for 200kJ in parallel (3.08F @ 360V) would only provide 12kJ, about 6% of the energy, hardly the capacity we could get if we could extract down to 0V.

Is the only other solution to use a DC-DC converter capable of converting 20kW bursts and tracking a huge voltage swing (following the capacitor charge/discharge voltage profile)?


texts: Simple Class A Output Power Stage of Amplifier

texts:
I made this circuit and the output signal wasn't really what I was expecting to be.

simulate this circuit – Schematic created using CircuitLab

This is class A amplifier (both Q1 and Q2 conducting both negative and positive half cycles). I was only curious how the signal from V1 is buffered to the output and I am already (at this point) insecure about its operation.

Here is the measurement of a signal I scoped:

As can be seen, there is a "double-amplitude" signal at the point where I probed the circuit.

Is this the consequence of Q1 and Q2 constantly conducting the signal?


texts: How to drive an 100 mA forward current LED using STM32H743 Microcontroller to the collector without using external power supply?

texts:
I am new to electronics hardware so kindly help me and give me suggestions.

I am working on STM32H743 microcontroller for dual camera interface and LED interface.

The total current of my STM32H743 Nucleo board is 500 mA in that both the cameras and microcontroller consumes 450 mA of current, so there is only 50 mA left to drive an LED (forward current 100 mA).

I am planning to drive an LED using PWM signal from the microcontroller using an NPN transistor.

Since I have only 50 mA left for supply current, I'm not able to drive my LED (forward current 100 mA).

Is there any solution for it?

Please find my circuit below:


texts: Can I power my circuit from the car stereo power wires?

texts: I have a circuit that should be turned on whenever the car stereo is turned on. It will draw ~300mA. My plan is to connect my circuit to the wire harness behind the stereo as it has +12v, ground and ignition swith-on signal available. Is there a reason why I shouldn't connect it directly to the car stereo wire harness as shown in the picture below?


texts: Will using the positive end of an AA battery to touch my phone screen damage my phone?

texts:
I'm playing a game where it will be helpful to hold down a button for an extended period of time. I didn't have a stylus, so I looked online for any ideas. Lots of people said to use the negative end of an AA battery. It works, but only when you're touching the battery. So I tried the positive end of the battery on my phone's touch screen, and it works (even when I'm not touching the battery). I haven't seen anything online about this, which I found very unusual.
So my question is, will it damage my phone if I use the positive end of an AA battery on my phone screen?


texts: Ouija board Christmas lights a la "Stranger Things" wall

texts:
first time poster here. I am NOT an electrician and I have limited experience beyond basic wiring and home improvement, so please bear with me and feel free to over-explain. :)

If you've seen the series "Stranger Things", I'm planning to recreate the wall of letters w/corresponding Christmas lights for a Halloween display (reference: https://www.youtube.com/watch?v=MEZnX14qaUc).

I want to avoid using a lighting controller or anything like that due to the complexity and cost. The most straightforward solution I can think of is to get a strand of C9 LED bulbs and:

Cut the wires between each one.
Insert each 26 bulbs in the correct position but with the wires poking
THROUGH the wall to the other side.
Extend the wires out and connect each positive and negative to it's
own momentary switch.
Arrange the momentary switches on a surface like a homemade
keyboard, labeled with the corresponding letter it controls.
Drape another (dead) wire across the bulbs on the front side of the
wall to give the appearance that they are connected in a series,
just for show.
Connected all the positives and negatives off the other end of the momentary      switches together into one positive, one negative lead and connect that to a battery pack (2 AA batteries).

Assumptions (again, amateur here, please let me know if any of this is wrong):

Using an inverter shouldn't be necessary for this application since the lights aren't going through a controller, it's a simple one-at-a-time light circuit w/a switch.
2 AA batteries should suffice, since the intended use is to light up one LED light at a time.
I want to avoid plugging the lights into an outlet because I'm not comfortable with electrocuting myself, and it seems that LED's can run just fine off of a battery pack.
More of a question, what is the most efficient way to merge 26 wires into one? Is there a piece of hardware that can like... crimp them together or something? I would rather not solder the whole thing.

Shopping List

Lights
Momentary Switches
Battery Pack
A bunch of extra speaker wire.

What do think, will this work? Any suggestions and/or improvements? I am thankful for your expertise!


texts: Looking at a RS485 signal with an ocilloscope

texts:
Is it possible to view a RS 485 diffential signal using a
Rigol DS1102E 100MHz Digital Oscilloscope, Dual Analog Channels, 1 GSa/s Sampling, USB Storage?

I can see a signal that looks more like amplitude modulation, but not a square wave.
How can I view serial data?


texts:
I think I'm missing something on the PID theory.
I have a motor rotating at X rpm, controlled by a pwm output (range 1 - 1000).
Let's say it rotates at 20 rpm when pwm is halfway (500).
I need to control the PWM to keep the motor rotating at a set speed.
How should I setup the PID?
Please tell me where I'm wrong (assuming the motor rotates at 18 rpm instead of 20):
error = setpoint - current_value = 20 - 18 = 2
Only by considering the proportinal part, for sake of simplicity, in this case the output should be:
out = Kp * error = Kp * 2
in order to even move the motor, I should use a Kp of about 250... In my understanding the K values should be very little ones..
thanks


texts: External fan to come on when AC unit comes on.

texts: I want to have an additional 120v fan come on when the AC unit is on. Am I able to wire that off the thermostat somehow?


texts: Protection against electrostatic paint by draining the charge

texts: I have a circuit for an automotive sensor aimed for 24V supply. The circuit itself is well tested for EMC requirements including power line transients and EMC immunity. Usually the requirement is for all the terminal pins to be galvanically isolated from the metal housing. We have but a strange requirement from one of our customers that demands the opposite. They subject our sensors to electrostatic painting and it may be - just may be- that some charge gets induced on one of the terminal pins. They want some high resistance conduction path from the pins to the case-housing to provide as a relief valve for the charge to be grounded in such situation. I already have the Y-caps from case-housing to all the lines. I was thinking of some high resistors in parallel to each of these caps as a charge draining path. but then what effect would it have on the galvanic insulation requirement (>10Meg @ 500V)?


texts: Why such low voltage across my filtered half-wave rectifier?

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Essentially my problem is this: I built a simple half-wave rectifier with some capacitive filtering, but I can't account for why my voltage is so low.

Below is the circuit I built:

Vs is 5V amplitude, 10 Vpp, 60 Hz, sine wave. Using newer Tektronix Oscilliscopes and Signal Generators.

As you can see from the diagram, the scope probe locations are defined. In the image below, yellow is CH-1 (input) and blue is CH-2 (output):

From my hand calcs, the output voltage should have been about 3.1V to 4.4V (the 1N4007 diode has a forward voltage of about 0.6V). Just to make sure I wasn't crazy, I confirmed this with LTSpice:

So there are a number of things bothering me here:

Why does the input waveform look strange?
Why is the output voltage so much lower than expected?
Why is the ripple voltage narrower than expected?

I spent some time with the 1N4007's datasheet and played with the SigGen impedance but that didn't help and I'm not really able to answer this question in my head.

Thanks!


texts:
I have recently received an old 70's era Tektronix 465b dual trace oscilloscope.  Unfortunately I have close to no clue how to use it.

I understand the concept of triggering but this scope has two triggers, named trigger A and trigger B(DLY). Is trigger A for channel 1 and trigger B(DLY) for channel 2?

Some insight would be greatly appreciated as the manual is nearly useless in describing this.


texts:
Sorry if the following looks like a  very specialized (or programming) question, but I'm hoping there are people on this forum who have done VHDL/Verilog modeling, and might be able to answer:

I'm writing a simulation model of a multi-processor cache system. My processor model is a 32-bit Sparc V8 processor. I was trying to understand how the processor- L1 data cache interface looks like. I have the following doubts:

How wide is the processor-L1 interface? If it is 32 bits wide, then how are doubleword accesses handled atomically? Example: if the DoubleWord instruction is split into two word-accesses, can the block in the cache get invalidated between the first and the second word access? Doesn't it mean the instruction is not atomic? Is the load/store doubleword instruction required to be atomic?
How are atomic load/store or swap instructions implemented on this interface? Is there a signal going from the processor to cache that says "stall all other operations until I say so", and then execute a load followed by store?

I'd be thankful for any links pointing in this direction


texts: STM32F303K8 ADC value is between 27 to 112 instead of 4095

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I have an STM32F303K8 and I am reading now ADC values. The values are too small. Between 27 and 112 instead of going up to 4095. Any idea why?
Can it be because I am debugging with USB port and STM32 is only connected to USB. Will it have enough power?

I am talking about Pin7 or Pa4

Code
static returnCode_t remoteInputs_getADCbufferAverage(uint16_t* buffer, uint32_t size, uint16_t *AverageADC)
{
    if( (buffer != first_half) && (buffer != second_half) )
    {
        return RC_ERR_ARG;
    }

    static uint16_t oldAverage = 0;
    uint32_t average = 0;

    for (uint32_t i = 0; i < size; i++)
    {
        average += buffer[i];
    }

    uint16_t newAverage = average/size;//simple_filter(oldAverage, (average/size));

    *AverageADC = newAverage;
    latestAverageADC = newAverage;

    if( latestAverageADC != oldAverage)
    {
        oldAverage = latestAverageADC;
        return RC_SUCCESS;
    }
    // TODO for test only return RC_ERR_UNKNOWN;
    return RC_SUCCESS;
}


texts: Why so little current through bypass capacitor?

texts: 20V going into NMOS enhancment BSB012N03LX3 FET, gate is completely DC offset sinewave. Capacitor C1 does yeild AC only @ ~180nA - how would I go about making higher currents with this or a similar topology?


texts: Imprecise bus error when setting Vector Table Offset Register. TI CC2652

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I am developing a bootloader and want to jump to the application.
I am new to this so I am not entirely sure I am doing it right, but as far as I know I have to change the value stored in the VTOR (Vector Table Offset Register) to point to the Vector Table of the application. However when I try to do this I end up in the FaultISR(). In the CFSR (Configurable Fault Status Register) I can see that the IMPRECISERR bit is set. This is the description of that register:

  Imprecise data bus error. It is a BusFault, but the Return PC is not related to the causing instruction. This is not a synchronous fault. So, if detected when the priority of the current activation is higher than the Bus Fault, it only pends. Bus fault activates when returning to a lower priority activation. If a precise fault occurs before returning to a lower priority exception, the handler detects both IMPRECISERR set and one of the precise fault status bits set at the same time. BFAR is not written.

The following function is the function I use to try to jump to the application.

void svcallIRQ(void) {
    typedef void (*p_function)(void);
    uint32_t jump_address = *(volatile uint32_t*)(FIRM_OFFSET + 4); // FIRM_OFFSET = 0x2E000
    p_function p_jump_function = (p_function) jump_address;

    __disable_irq();

    uint32_t *vtor = (uint32_t*)CPU_SCS_O_VTOR; // CPU_SCS_O_VTOR = 0x00000D08
    *vtor = ((uint32_t )FIRM_OFFSET); // change vector table offset to first bytes of firmware

    __NOP(); // The error occurs after this NOP
    __NOP();
    __NOP();

    __DSB();

    __set_MSP(*(volatile uint32_t*) FIRM_OFFSET);

    p_jump_function();
}

This function is a SVCall handler so it should be run in Privileged mode, which according to the documentation of the CC2652 is the mode you have to be in when trying to modify the VTOR.

Can someone tell me what I am doing wrong here?

Edit:
The paragraph below is taken from the Technical Manual of the CC2652 and explains writing to the VTOR.

  On system reset, the vector table is fixed at address 0x00000000. Privileged software can write to the Vector Table Offset register (CPU_SCS:VTOR) to relocate the vector table start address to a different memory location, in the range 0x00000200 to 0x3FFFFE00. When configuring the CPU_SCS:VTOR register, the offset must be aligned on a 512-byte boundary.


texts: Running AVRStudio 32 and JTAGICE MKII on Vista 64

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I've attempted installation of AVR studio 32 (for AVR32 UC3 development) and it doesn't appear to work.

Has anyone here gotten this to work in Vista 64?


texts: Dual Feedback Transistor Biasing a Common Emitter Amplifier

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I was reviewing/following a tutorial describing the pros/cons of various transistor base biasing configurations.  Configuration #4 is shown above.  Resistor Rb2 was added to what was previously Configuration #3.  The circuit with the text is shown below (in quotes)....

Why does adding Rb2  increase stability with respect to variations in Beta, ( β ) by increasing the current flowing through the base biasing resistors?  The unclear (to me) original text is below.  Thanks

"Adding an additional resistor to the base bias network of the previous configuration improves stability even more with respect to variations in Beta, ( β ) by increasing the current flowing through the base biasing resistors.

The current flowing through RB1 is generally set at a value equal to about 10% of collector current, IC. Obviously it must also be greater than the base current required for the minimum value of Beta, β.

One of the advantages of this type of self biasing configuration is that the resistors provide both automatic biasing and Rf feedback at the same time."


texts: Why does wire gauge go down as the physical wire size goes up?

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I've always just accepted this but why is it that wire gauge goes down as wire size increases? Why not the other way which would make a bit more logical sense?

i.e. Why isn't it that 40 AWG = big wire, 0000 AWG = small wire.


texts:
I'm trying to build a guitar amplifier and I've run into some problems that I can't understand.

The input has an op amp to buffer and amplify the guitar signal which looks like this:

simulate this circuit – Schematic created using CircuitLab

Open wires on the left are where the guitar is supposed to be connected (I'm measuring it with no input) and out will go to a tube, but I've taken it out for testing now.

My problem is that without any input I'm expecting (and the simulator agrees) the circuit to output almost exactly the voltage of the virtual ground (2.04V, from what I've measured), but I'm seeing 1.45V -- 0.6 V lower than expected. The values measured are DC; when measuring AC everything shows 0 exactly as I would expect. Also my amplifier has two identical channels and the second one shows almost identical voltages -- I think that it decreases the probabilty of the problems being caused by my soldering.

I've checked all the voltages around and tested continuity to see if there aren't any unexpected shorts, but I didn't find any other problems than this, but I've run out of ideas. Are there any obvious problems with my design? What else can I try to find the problem?


texts: Finding the Transfer Function and Simplifying it to Standard Form

texts:
Hello, forgive my formatting- I am new and am trying to learn the ropes.
When I tried to find H(s)=Vo/Vi, I derived:

[R2 || 1/(sC2)] / [(R1 || 1/(sC1) + (R2 || 1/(sC2)].

However, when trying to simplify the function into the form,

H(s) = K(1 + sTz)/(1 + sTp)

I am stumped. This might be as trivial as simple algebra, but perhaps I don't understand transfer functions that well. The closest I have gotten is:

1 / [((1/R2) + sC2) / ((1/R1) + sC1) + 1]

That was obtained from just dividing the top and bottom by the same expression 1 or 2 times.

I would like a hint or a push in the right direction. Thank you for your time.


texts: What are important inductor parameters to specify for use in a matching circuit?

texts:
The title could be more clear: I have a matching circuit but the datasheet is restricted. I'll post a reference matching network as a schematic here.

simulate this circuit – Schematic created using CircuitLab

So here I am, on my favorite distributor's webpage looking at a few hundred surface mount inductors (preferably 0402 sized). Yes I want a low DCR, but how does self-resonance come into play? How does Q come into play? The capacitors are less worrysome since all the pFs are going to be NP0 dielectric and the 2.2n is XR7 as specified in the datasheet.

I'm specifically redesigning to maximize RF link performance so I'd like to get this one right!


texts:
I repair laser tag vests and on the phaser board is a strange component on what appears to be the phaserboard. See the black box on the center of the bottom, close to the left edge of the ribbon cable.

It has no reliably measurable resistance and as far as I can tell is involved in power delivery, as when it falls off (which it does often) the phaserboard no longer gets power. It has a marking on the top saying "100k" but nothing else. I would like to know what it is so I don't depend on trying to find it when it falls off and can just order new ones.

Edit: It would appear from answers that it is an inductor of some kind. During my next shift I'll try to get some closer, higher quality photos to see if we can narrow down, since I've combed through DigiKey and haven't found any matches I'm comfortable with.

Edit: Here are more pictures (I can post more if I get more reputation, sorry!):


texts: How many watts will the resistor in this naîve PSU dissipate?

texts:
One would be inclined to think the average current on resistor R would be exactly the same as in the load L, but I'm not so sure of that fact, due to the effect of the (big, 1000uF+) capacitors. During a significant portion of the AC cycle, the current supplying the load comes from the second capacitor, not the resistor.

What are the calculations involved to assess R's wattage? (Oh, and apologies for the pathetic drawing.)


texts: Are there any low temperature (60 - 100 degree celsius) soldering pastes?

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I'm looking for  low temperature soldering paste that doesn't come in a wheel of filament. It seems tin and bismuth soldering pastes have a melting point of around 160 degrees Celsius.

Are there any formulations, or products on the market, for an even lower temperature soldering paste? I guess this company makes them, but I'm wondering if there is a formulation with a stronger market presence.

I need a conductivity strong enough to use ICs.


texts:
I'm working with mpu9250 gyroscope and I got fine measurements for beginning period (few minutes). I calculated offset at start in manner to average sum of first 1000 results from mpu9250 gyro. But If I put mpu9250 on one place and I don't move it I got accumulated error of axes.
For example after 5min I got offset of pitch ~1.2degree, roll ~2.5degree and yaw ~1degree.
Does anyone have idea how to solve this or what is there happening? I assume that mpu9250 need some movement each period (for example mpu9250 need position change every 10sec to avoid accumulating of error)


texts: Why measuring a differential signal requires a differential probe?

texts:
I am planning to measure an RS485 signal with an oscilloscope. Since I want to see the signal that is "seen" by the receiver side, I was planning to plug the reference terminal of probe to Sig(-), and the measurement terminal to Sig(+).

However, I saw in many places that a differential probe should be used for measuring differential signals, and I couldn't understand the reason.

Measuring differential signal with single ended probe

What is the reason? Why does a differential probe exist after all, since all measurements in electronics are inherently differential?


texts: If I connected N numbers of amplifiers each have X gain 'dB" and Y power "dBm", how to calculate total gain and power?

texts:
sorry for bad description, I am a beginner.

my question is just for knowledge and I did not test anything.

If I connect for example 3 amplifier , each one has 60 dB gain and 15 dBm power.

can we say simply total gain is 180 dB and total power is 15 dBm ?

or I am wrong ?


texts:
I have a PIC32MX, and I'm using the UART interface to communicate with an external device.  When I first start up the PIC, I am properly able to get interrupts on UART1 whenever I receive a byte of data.  However, after a short period of time(<1 minute) I will stop getting UART interrupts.  Here's the basic sekeleton of code that I'm using to test this:

void DelayUs(unsigned int delay) {
    unsigned int int_status;
    while (delay--) {
        int_status = INTDisableInterrupts();
        OpenCoreTimer(SYS_FREQ / 2000000);
        INTRestoreInterrupts(int_status);
        mCTClearIntFlag();
        while (!mCTGetIntFlag());
    }
    mCTClearIntFlag();
}

extern "C"{
void __ISR(_UART_1_VECTOR, ipl2) IntUart1Handler(void) {
    // Is this an RX interrupt?
    if (INTGetFlag(INT_U1RX)) {
        uint8_t data = (UARTGetData(UART1)).data8bit;
        // Clear the RX interrupt Flag
        INTClearFlag(INT_U1RX);
    }

    // We don't care about TX interrupt
    if (INTGetFlag(INT_U1TX)) {
        INTClearFlag(INT_U1TX);
    }
}
}

main(){
    UARTConfigure(UART1, UART_ENABLE_PINS_TX_RX_ONLY );
    UARTSetFifoMode(UART1, UART_INTERRUPT_ON_TX_NOT_FULL |UART_INTERRUPT_ON_RX_NOT_EMPTY);
    UARTSetLineControl(UART1, UART_DATA_SIZE_8_BITS | UART_PARITY_NONE | UART_STOP_BITS_1);
    UARTSetDataRate(UART1, GetPeripheralClock(), 16660);
    UARTEnable(UART1, UART_ENABLE_FLAGS(UART_PERIPHERAL | UART_RX | UART_TX));

    // Configure UART RX Interrupt
    INTEnable(INT_SOURCE_UART_RX( UART1 ), INT_ENABLED);
    INTSetVectorPriority(INT_VECTOR_UART( UART1 ), INT_PRIORITY_LEVEL_2);
    INTSetVectorSubPriority(INT_VECTOR_UART( UART1 ), INT_SUB_PRIORITY_LEVEL_0);

    //set up the output and input pins for UART1
    TRISBbits.TRISB7 = 0;  //RB7 = TX
    TRISBbits.TRISB6 = 1; //RB6 = RX
    RPB7Rbits.RPB7R = 1; //RPB7 = U1TX
    U1RXRbits.U1RXR = 1; //RPB6 = U1RX

    // we can turn on interrupts now
    INTConfigureSystem(INT_SYSTEM_CONFIG_MULT_VECTOR);
    INTEnableInterrupts();

    while (1) {
        // Do work here...

        DelayUs(100); //wait .1mS until next ping
                        //This is in reality ~200 uS
    }
}

I'm testing to see if I'm still getting interrupts by setting a breakpoint in the ISR using MPLABX and an ICD3.  I can trigger incoming data into the PIC.  When everything is working fine, I can set/remove the breakpoint in the ISR, but after a certain point the ISR does not get triggered anymore.

I think that what could be happening is that I'm getting a TX interrupt when I am delaying my main loop as part of the DelayUs function.  Could that happen?  Is there anything else that could cause the interrupt to stop firing?


texts: Optocouplers driving MOSFETs in an inverter

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For many hours I was trying to simulate in LTspice XVII an optocoupler driver for MOSFETs in an inverter. My project is to build a SMPS with linear voltage stabilizer (I didnt put it on the schematic yet) that is conotrolled by AVR microcontroller. I've managed earlier to succesfully drive a MOSFET through an optocoupler but I couldn't succesfully apply it to my main schematic.

Here is the picture of my schematic of LTspice:

I don't know what seems to be the problem. My guesses are that I've made mistake somewhere in the schematic (most likely) or the optocoupler isn't capable of switching at 20 kHz.

Here is what I tried to solve:

I've tried changing the PULSE voltage source (microcontroller output) frequency to 200 Hz and the voltage on the 10k resistor at least dropped to 0 V (at 20 kHz it varied from ~10V to 15V).

Here is the picture of the voltage on the resistor (I suppose that is the Vgs) (10k - blue, 1k2 - green):

Changing resistance of the 10k resistor to 1k2 (with the pulse voltage freq = 20 kHz) and the voltage also managed to drop to 0 V.
I've connected te ground of the resistor to the source of the MOSFET - but that short circuited the primary winding of the transformer.

Question:

How can I make this optocouplers to drive the MOSFET transistors, so that the transforer works (right now there is no voltage on the primary winding).
(In case the simulation works properly) What would you suggest to reduce Vgs rise time? Are Totem Pole optocouplers faster and also can be applied to driving MOSFETs?

Thanks in advance for any help.


texts: Simulation showing different results for a same practical case

texts:
Below I have this simulation.
The diodes represent the clamping diodes placed inside the microcontroller GPIO pins.
Case 1 - Given directly using the voltage source.

Case 2 - Given the same voltage through a resistor divider.

In the above image, both the circuits are providing 12V at the GPIO pin. But first one is given through the voltage source. Second is through a resistor divider network. But effectively, same voltage is given and provide at the GPIO pin. But we are getting different results.
I understand that in the first case, since the Voltage source output is very low impedance, it is showing 12V. But I am confused on this behaviour and unable to arrive at a conclusion on how the 2 cases are different. Please help to provide an answer in simple terms for my clarity.


texts: Is it possible that an outlet can kill AC motors?

texts:
I have two recently dead tower fans. The first, I've had for over 6 months, no problems. Recently, I moved it to a new room an plugged it into a different outlet. It died within a day: it seems to be just the main motor, the controls still work as does the separate motor for swiveling the fan. Took it apart to look for anything obvious, tried to run it with the fan blades off of the motor but no go. So I bought a new one, different brand and model but same basic setup. Plugged it into same outlet, died within a day. Is it possible that there's something in the wiring of the outlet that kills the fans' motors? I've plugged a humidifier and lamp into the same outlet with no problems. One other factor that may be related is it's a 20A outlet with the T-shape (probably for AC as it's near an AC sleeve).

TLDR: two fans motors broke (controls still work) after being plugged into same 20A outlet (not at the same time). One six months old, one brand new. Curious if something might be wrong with the outlet and if so what I can do to test or fix it.


texts: Transfer function of a real opamp circuit

texts:
I know how to calculate the transfer function of an ideal opamp. But when calculating for a real opamp, should I use the Input Bias Current values specified in the datasheet? If so, use the Min, Typ, or Max value?

Note: the links provided are only an example, not of the circuit I trying to figure.

How should I approach finding the transfer function, and essentially the value at VOUT?


texts: How to get I2C to shut up while waiting for data in master transmit mode on LPC1114

texts:
I have an LPC1114(FN28) that I am writing some code for. Currently I am trying to provide an asynchronous view of the I2C interface to my code (the chip has a built-in I2C controller). The controller itself is basically a state machine, but since the I2C spec specifies no timeout or other restrictions on the SCL clock rate, I should be able to delay sending (it doesn't have to be perfectly synchronous) as long as the controller controls SCL correctly when data is being sent, and holds it low when no data is being sent.

The idea is to be able to buffer data to be sent on the I2C bus. A few libraries I see around deal with this by just buffering the whole thing and bitbanging it all at once, which is okay most of the time since you generally don't send lots of data over I2C, but I want to do it properly.

I've set up the base code and the problem I am having when transmitting data is that whenever the controller enters the "transmit data to slave" mode, it triggers an interrupt requiring me to fill in a byte of data to send (or send a STOP signal). The problem is if I do nothing, it immediately issues the same interrupt, so my main code can't even get the chance to execute! What I want is the ability to tell the controller "I have no bytes to send right now, so don't issue another interrupt until I tell you to from my main code"!

I've rigged something up that works by (ab?)using the NVIC to disable the I2C interrupt when I am waiting for data, and re-enabling it when I am ready to send on the I2C interface, but this seems very unorthodox and I don't know if it is actually reliable or even correct especially if bad stuff should happen to the bus in the meantime (bus error, etc...)

Here is the manual for the chip, the docs for the I2C controller are at page 239. I thought I could use the SI control bit to tell it to not issue an interrupt until I clear it again but apparently that's not what it's for.

Does anyone have experience with this or similar I2C controllers and know how I can achieve what I am looking for? Clearly it must be possible, since a protocol where you need to have all the data ready up front every time doesn't seem viable to me.


texts: Failsafe solution to vertical router Z-axis assembly

texts:
Thank you for taking the time to read this.
TL;DR: I need to somehow check the state of the motor and solenoid actuator. Only if the motor is ON and the actuator OFF should current pass into a relay (in the diagram, another actuator that pushes power button) that shuts off all power.
I'm currently making a CNC router for my startup with a very small budget. Due to space constraints, the router will be of the vertical sort.
In the event of a power failure on a vertical router, the Y axis, which moves up and down, can slam into the bottom causing potentially expensive damage. As such, I'm looking for a failsafe solution to this. The weight of the moving assembly is 10kg.
I know there are brakes on the market, but the ones that brake when unpowered are several hundred, far out of budget.
My idea is to use an electromagnetic solenoid actuator, which is extended when powered off. As such, when powered off, the actuator would move into a cog that would be mounted on the ball screw shaft, locking it in place
I have, however, read that such actuators are not meant to be powered on for longer periods of time. With this setup, the actuator would be powered on when the router is on. If it were to fail, it would engage the lock while the motor would try to turn. To prevent this, I figured it would be possible to use 2 relays, one NO and one NC in series. The Y-axis motor would be connected to the NO signal input, so when the motor is ON, it would allow current through. Next would be the NC, the signal of which would be connected to the actuator, so when the actuator is OFF current flows through. It is my understanding that should the solenoid break, power would not pass from positive to negative.
As such, it essentially "checks" the states of the motor and solenoid, and if the motor is on and solenoid is off (locking the ballscrew) it will pass current through. This current will then go to another solenoid that pushes a power switch (low tech, I know, cheapest idea I could come up with). The power switch should also be pretty easy to reset once things are fixed.
I attached the best diagram I could make of this, I hope it will be understandable. In the diagram everything is working as intended, but should the actuator die, the normally closed relay will close and other actuator will push the power button. At least that's what's intended.
I would love to both hear if I'm an idiot, KISS, and any either better, simpler, cheaper solutions to this. Keep in mind I'm in no way an engineer, only a hobbyist and the only thing I know about electronics is not to let the magic smoke out.


texts: Adequate Power Supply for 300 Daisy-Chained LEDs

texts:
I have 300 LEDs (WS2812B) wired in a series. They were sold as 150 LED/5 meters and rated to power at 9W/m, so 45W/5m strip. I would need 90 Watts to power my entire 300 LED strip. I have a 3-rail power supply that has an output of 5v 40A (200W), would this be adequate to power the LEDs?

Naively, I thought I could power them straight from the PS but got major color change around the halfway mark (expectedly where the second strip is connected). I soldered +V and -V of the second rail to the halfway point and it helped my situation but not entirely and I am worried I am going about it wrong. If anyone could shed some light (haha) on my situation I would greatly appreciate it.


texts: Why is reading the 3T1C DRAM cell not destructive?

texts: Could anyone help explain how the above 3T1C DRAM cell works?  T means transistor and C means capacitor. Why is reading it not destructive?


texts: Using aluminium electrolytic capacitors in RC filter

texts:
I have a RC filter on which I need to increase the capacitance. I have one 47uF ceramic capacitor and 2 47uF aluminum electrolytic ones at home. Can I use these in parallel in the RC circuit?
Thank you for your help!


texts: Would adding ~2 ft of copper wire to extend high voltage power supply cause problems?

texts:
I have a high voltage power supply (LabSmith HVS) that I've been using to output a in the range of 100-300V across a microfluidic channel. The cables that came with the power supply are pretty short, so they can't reach the region of an instrument I'm using to make measurements. My solution to this is going to be to wire a few feet of copper wiring through the instrument and out the back to a place where I can connect the electrodes that came with the power supply.

What this means effectively is that I plan on introducing about three feet of copper wiring to this system. Is the addition of this wiring going to impact how the voltage is applied? My intuition is that, since the effective resistance of the device I'm using is about 10 megaohms, this additional wiring would be negligible.

Side-question: My electrodes are copper wire soldered to platinum wire, which actually makes contact with salt solutions. Does applying ~100-300V have any non-negligible effects on the soldering or conductivity through the wires?

Thanks for the help.


texts:
First off I should probably mention that I'm a beginner when it comes to electronics.

I am planning on adding some buttons to a controller but have limited space for wires. Only 2 of the wires I have will fit (3 with a little modification perhaps). I would like at least 6 buttons (2 groups of 3) to connect to the microcontroller using only these wires. There are plenty of digital and analogue pins available.

What are my best options? I've read about multiplexing and using an analog pin with resistors on the buttons to give each its own voltage but they both only allow one button to be pressed at a time. Ideally I want to be able to push at least two buttons at the same time (one from each group).


texts: Why the prevelance of mechanical oscillators in electronic circuits?

texts:
The clock sources in modern electronics seem to come invariably from quartz and MEMS oscillators, both of which generate vibrations mechanically. The amplitude and frequency of the vibration are orders of magnitudes different from the everday mechanical vibrations I observe in, say, musical instruments. Nevertheless, it's surprising to me that we don't get clock sources in the electromagnetic domain directly, say using capacitive or inductive elements.

I know that inductors especially are hard to manufacture without parasitic losses. But I would expect mechanical oscillators to be non-ideal as well.

You could use the propagation delay of electricity, but then it would be hard to make a small oscillator that operates at slow frequencies.

Is it really true we can make microscopic vibrating devices more ideally than we can make electrical oscillating components?


texts: Advice needed for a final year project on wheelchair automation and control

texts:
My project partners and I have been trying to design a wheelchair for people with neuro-degenerative diseases. I know this has been done in the past, however we are using a different approach. We are trying to implement a semi-automatic system, whereby the user can switch to a fully manual or a fully automatic control.
The control signals are provided through an EEG device, so as the name suggests a fully manual system will need the user to control the wheelchair using EEG. The fully automatic portion will implement object detection and distance gauging and ask for the user input to select an object to move towards, and then the wheelchair will automatically move towards that object while avoiding any obstacles.
The method we have decided to use on the part of automation is using a stereo camera configuration for  object detection and using that same setup for measuring the distance, and the algorithm will try to minimize the distance up to a certain threshold. For now we have decided to use triangulation to measure the distance, however we are not sure if that will work with multiple objects in view.
Is the above approach viable? And can it be implemented on a real-time embedded system? Are there any sources I should look up to further aid myself in the project? Any advice will be appreciated.
As a side note, the purpose of using only cameras is to reduce the bulk of the overall machine. And it will provide more flexibility in case we need to update or add certain features. The switch between automatic and manual will also be accomplished through EEG signals.


texts: Using multiple resistors on a breadboard to limit voltage to LED

texts:
so I've recently begun my venture into electrical engineering, just got myself a breadboard with some jumper cables, a pack of assorted LED's and a few 200 ohm resistors.

I'm trying to understand how to further limit voltage to my LED using a 9V battery and multiple 200 ohm resistors but I've come up with the following question / problem.

Judging from this image: can you please tell me if this is wired properly? I have 7 200 ohm resistors connected in this circuit and it doesn't appear to be dimming the LED at all. When I take away 3-4 resistors, it's still just as bright. @ 1400 ohms, I figured the LED's would be significantly dimmer but alas they're not.

The specification of the LED i'm trying to power with my 9V battery is, Green, 2.9-3.1V with a forward voltage of 20mA

Anyhow, I'm having a heck of a time tying to wrap my head around this and figure it's something small I'm missing. When I touch all 7 resistors connected to this circuit, I can definitely feel a significant amount of heat coming off of them.

Would anyone be able to assist me with this issue I'm having? any advise or criticism is appreciated.

Thanks all.


texts: how to drive a 1.35V led with a 1.4V AA battery

texts:
I would like to mount a TSAL6400 led on a single AA size battery box, with a simple ON/OFF switch. My problem is that the LED needs exactly 1.35V to function at its rated brightness. At this voltage it uses 100 mA current.

I would like to use Sanyo Eneloop batteries. I've measured them and they have 1.405V one day after charging. I think they will drop to about 1.395V @ 100mA.

I've followed the LED tutorials, which all say I have to wire a resistor in serial with the LED. My problem is that if I calculate, that resistor needs to have (1.4-1.35)/0.1 = 0.5 Ohm resistance.

My question is that what would you recommend me to do this project? I would like to make the box as little as possible, I'm planning on mounting everything directly on a single AA box.

Shell I use two 1 Ohm resistors in parallel, to get a 0.5 Ohm resistor?
Can I possibily use some micro turn potentiometers for my problem? It would be the best solution, as then I could just use different batteries, as all I would need to do is to set it after changing batteries. I am mostly interested in this solution. Can someone explain to me what is the best way to get 1.35V from 1.4V-1.6V sources using a simple potentiometer?
Maybe it's an overkill, and I really don't know how to use them, but can I use a voltage regulator for this purpose? I mean is there a voltage regulator which is small and can provide as little as 0.4V drop?

UPDATE:
I've made some measurements on my LED:

1.184 V -  12 mA
1.315 V -  75 mA
1.345 V -  93 mA
1.357 V - 100 mA
1.380 V - 110 mA

The last one is when I connected it directly to a Eneloop AA battery. By definition it's overdriving, but I don't know how dangerous it is for the LED.


texts: How to achieve the max efficiency from a Buck converter

texts:
I have a question about switching step-down regulators.
(As I stated in my previous questions, please consider the fact that that I'm not very expert, so feel free to reply/talk as if I were a student.)

Let's take a practical example of a switching step-down regulator, based on this IC.
(I've seen that is largely used and common in various circuits):

We need to feed a device which needs 12V with a power consumption of 200mA.
Ok: We'll take a buck converter circuit, and as Vin we'll provide, for example, a voltage of 30V from a batteries pack with a total capacity of 2000mAh, then we will set the Vout of the buck converter to 12V. But If we want to make use of a less number of batteries we can also go with a Vin of 20 or less volt: I have read that for the lm2596 IC, the Vin, should be at least greater of 1,5V than the Vout.

I was thinking: If I reduce 30V (from a batteries pack) to 12V, the difference of 18V could be reason of an higher power consumption from the batteries? Am I right? Eg I know that linear regulators (differently from switching regulators) have a bad efficiency because some of the power will be lost as heat. But what about switching regulators? Some days ago, by a search on Google, I've read of a person which had the needs to get 5V using a Buck converter: someone told him that would be better get the 5V from a Vin of 18V instead of using a Vin of 12V.

So, taking again in consideration my example: when using a switching regulator, is better to start from an higher Vin, for obtaining a same Vout? Why?

I'd also like to see some charts of the switching regulators.


texts: Limiting inrush current in N Channel MOSFET power switch

texts:
I have a N-MOSFET as power switch like this:

I want to add a fuse on the power line but I have few capacitors on the across the load and I am worried that the inrush current might blow the fuse off. How can I limit the inrush current here? I saw that for P-channel one can add capacitor across drain and gate. I am not sure if this works for N-ch MOSFET as well.


texts:
I have this bode diagram. I am wondering how to interpret this. We start off with 90 degree phase lag e.g. a integrator. Then at approx 12 Hz we drop another 180 degrees indicating two integrators.

Now my problem is with the ripples which start at about 60 Hz and continue to blow up till it reaches some maximum? and then it stops at 4KHz? What are these?

ps. it has to do with this question, Derive transfer function from block diagram, for which I was able to derive the frequency response.


texts:
I wish to use some 12 V, 5 W xenon light bulbs under separate shelves of a cabinet.  I'd like them to power-on using a magnetic reed switch attached to the cabinet door.

The magnetic reed switch I have has a current rating of 0.5 A 20 V DC: 10 W max.

My question:  Since the lights are 12 V and NOT 20 V, would stepping down to 12 V change the ratings at all in regards to wattage?  Or in other words, could the switch handle 3 of these 12V 5W bulbs (15 watts) since the voltage is less?  Not sure if that changes the max specs or not.

The lighting company also offers 3 watt bulbs but I'm trying to get the maximum brightness possible.

I'll have to get a DC transformer as well to match specs.

Any and all advice is very much appreciated!


texts: Can I use a 11.1V LiPo directly on 12V electronics?

texts:
I'm considering using a TS351 video transmitter (6.5-12V) and a 700TVL camera (8-13V) on an RC aircraft where a 3S LiPo battery (11.1V) is used as the main power source. The rest of the electronics on board use a 5V source that I tap off of a brushless motor's ESC (via the included 2A BEC). What is the best way to power the transmitter and camera? Is it safe to tap a line directly off the battery for each or do I need regulators of some sort? I'm thinking one common regulator to both would be best.

A fully charge 3S LiPo outputs about 12.6V.

The vehicle currently has 4 20A ESCs for 4 brushless motors and the flight control electronics run off 5V. Currently I am running the flight controller and RC receiver from the 5V tap from the ESCs, but I probably need to separate the two power busses, or do I?


texts: What could have caused the MOSFET to fail in this high-side switching circuit?

texts:
I was trying to help my friend fix an issue with his car not getting a signal to the coil (obviously this isn't the correct fix, but it has had the car running previously).
The circuit is driving the trigger of a car's coil pack, is driven by the distributor with around 12VDC.

R1 is 3.3k
R2 is also 3.3k
PC817 optoisolator
IRF9520 PMOS

simulate this circuit – Schematic created using CircuitLab
12v is enough for more than 30-50ma that the trigger pulls from datasheet
MOSFET failed with 1300 ohms gate to drain, 1100 gate to source.
Bench testing with 11.6v without the mosfet when opto is off, gate has 11.6v, on, 0.24v, seems to be working fine.
I'll spare you the details of when the mosfet is installed since it's failed.
He doesn't have an oscilloscope to test for voltages and claims the diode in the mosfet should be sufficient, what other options do we have to protect the mosfet and improve the circuit?


texts: Designing an effective extensible solar cell + car battery setup

texts:
I've got a cabin that I visit on weekends and because I need to charge my computer and tools there, I decided to bring an old car battery and bought a solar panel to charge it. Right now I use a cheap regulator and there's enough energy to power the lights and charge a laptop twice a week but I'm planning to expand the setup to achieve greater input and battery capacity and more effective charging. I'll probably have multiple solar cells and multiple batteries.

Starting from the solar panel, I'll probably need a MPPT regulator to harvest the maximum power available from the cell. I think that I'll have to use just one regulator even if I buy more solar cells, since most regulators aren't waterproof, I guess, and I've got only two wires to the roof. Does this mean that I'll have to buy solar panels with similar V-I curve and connect them in parallel?

I'm not really sure about the next part. If my understanding is correct, I get some power from the MPPT and I need to convert it to a form that is best suited to charging the battery using some kind of an intelligent step-up convertor. How does that work exactly? I guess it's not enough to use this thing set to 14.4 V output, or is it? What exactly do I need to do with the voltage?


texts: dc motor, hall sensor 10-20VDC to arduino

texts:
I have a linear actuator with a brushed DC motor with 2 hall sensors. I intent to use the sensors to monitor the position of the actuator.

The specifications of the hall sensors are as follows:

Hall Vcc recommended value 10-20 VDC, max 24 VDC
Hall output sink max 24VDC/100mA (open collector type)
188 pulses/resolution

Now I intent to read the signal using an arduino uno board, which has a maximum input voltage of 5.5V

My question is how to hook this up, such that I do not exceed the voltage of the arduino board. I have read about using a voltage divider, but not sure if this is the right way.

Could somebody point me in the right direction?

To clarify a bit further, this link shows a schematic of the situation.

http://www.solar-motors.com/inc/getfile.php?id=783163FD-16DB-4AE0-9A48-C1CD71093105

The arduino internal pull-up resistor is 20kOhm.


texts: Solid state relay (or equivalent/alternative) to drive 6V DC from a 3.3V micro

texts:
I have to open/close two wire from a closed device. I cannot open due to it's under warranty, and the only part that I can open and modify is an external button that connects the two wires.

Firstly I wrongly thought that I can simulate the button press ion with only optocoupler (4N25), but thanks to this answer I understood that this piece of hardware is not only an opto-isolator but an opto-transistor: it is better to use a SSR instead (a mechanical relay will not work because of the noisy "tick"). I don't have the GND signal but only Vcc and Vo (thanks to Peter R. Bloomfield for this elucidation).

Just to recap, my needs, I have in one side an Arduino Due that runs at 3.3V. In the other side of the circuit I have a signal that, when closed has 0-6V.

I have seen some other questions about how to simulate a SSR like this and this bit as I got this is not tailored to my case: I don't need a zero-cross detection because I have to drive a DC circuit, and I need to drive it from Arduino Due that runs at 3.3V.

What can I do? Are there some cheap SSR that fit my 3.3V driver and DC lead? Is there some simple opto-isolator that I can use without the GND signal (no opto-transistor)? Or something I can add to the 4N25 that I already tried? Is there some other alternatives that I ignore?

Please sorry my entry level in the electronics so correct me in terminology if I have used unsuitable words.


texts:
I am trying to define a 2d array in verilog but I don't understand them very well in the way they are assigned. What I mean is if I define an array like

reg [6:0] array[7:0]

I hope I defined an array with 8 rows and 7 columns. If a number is assigned lets say:

array[0] = 7'b1100000; array[1] = 7'b0101000;

In what order are they placed? My intention is to read the first bit in every row.
So if I read like this do I get the result:

array[0][0]-->should give 1(the first bit of first row)
array[0][1]-->should give 0(the first bit of second row)

So is my assignment way correct? Or should I play with the order like:

reg array[0:6] array[0:7]


texts:
Best Book For Computer Architect , As I have to build SAP this semester.

Most people  told me it is very difficult to make a SimpleAsPossible 8 bit Computer up and running therefore any suggestions for the best book in your view that will make my concepts for this course much strong

Thanks


texts: Problem in getting optocoupler output in Proteus

texts:
I am making a 5 level inverter in Proteus using 4N25 optocouplers but I am not getting any output from the optocouplers.
I don't know what is wrong with this circuit.
complete diagram


texts: RS-485: Error detection/correction mechanism

texts:
Does the RS-485 Standard include an error detection/correction scheme?

RS-232 has a parity bit for error detection, but I do not know anything related to error detection/correction in the RS-485 interface.


texts:
I need to cut a signal wire after one month from it start working.
So I am looking for timer circuit that it work by small battery make a short circuit for my signal wire after around ( few days more less ) one month.


texts: Does the mounting orientation or side of a heat-sink matter?

texts:
Imagine a transistor is normally screwed to a heat-sink as below:

If I screw the transistor in another orientation or from the the outer surface of the heat-sink would it affect the thermal resistance? I need to mount one through same heat-sink hole but from the outer surface of the heat-sink.

edit:

So I have the following heatsink:

But I want to mount this way:


texts:
I want to build an light fixture for my aquarium and decided to use LEDs, almost everywhere it's suggested to wire the LEDs in series. but that will need a high voltage for many high power LEDs. also if one of the LEDs in series for whatever reason burnt, all LED's will turn off.

The main reason to wire LEDs in series (if I understand correctly) is because of the manufacturing variation in LEDs, that may cause one LED pull more current than the others if wired in parallel.

Let's assume that we've 5 LEDs, each needs 1 V / 10 mA and it's connected to a power source which provides 1 V and 60 mA constant current:

simulate this circuit – Schematic created using CircuitLab

In above diagram each LED can't pull more than 10 mA and resistors will not get hot either because the power source have a current limit.

But what if the little variation in LEDs cause one LED to pull less current than the others? what's the solution for that?


texts: Storing pulses, then releasing them on trigger

texts:
I have a BeagleBoneBlack microcontroller that can generate pulses and clock for SPI.  These pulses have rise times of a few tens of nanoseconds, which is nice.

Unforunately, the BeagleBone is 'slow': when it receives an interrupt, it takes several ms to then process and send along the pulses and clock signal.

What I'd like to do is use the BeagleBone to generate the pulses beforehand; they would then be 'stored' in a much faster device. When externally triggered, the faster device simply outputs these pulses. Ideally, this device would respond in the microsecond or nanosecond range. It needs two channels: one for the MOSI SPI line, and one for the SPI CLK. They would need to be synced together.

So, how can I do this? Must I deal with an FPGA (I have little /no experience with this)? If so, is there some breakout board I can use? Or is there some simpler way?


texts: Reducing equivalent self inductance of an inductor

texts:
Let's say I have a coil of N turns and it is wound on a rectangular core and when we connect a voltage source through both terminal of coil flux is generated in core , now I wanted to reduce that flux as minimum as possible (zero would be Even better) .
Although it can be achieved easily if we are allowed to cut the winding   and then wound such a way that net mmf cancel each other
But  What if we are not allowed to cut the winding  ,is it possible reduce flux up to zero ?
First thought comes to mind that we can wound N/2 and N/2 such that flux will cancel each other but I'm not sure it will work because how can a series Inductance reduces (L=L/2-L/2) because (L=L1+L2) series connection are additive
Is above method works or not ? Or it is impossible to cancel or reduce flux because of series connection of winding?


texts: As I know, a clock controls all of the logic operations, but it also limits the speed of a computer because the gates have to wait for the clock to change from low to high or high to low depending on the component. If no clock was incorporated, the gates would change as fast as they could whenever given the command to, so why wouldn't that increase the computers speed  and why are clocks used?


texts: Resonance in Yig oscillators - is it normal?

texts:
The advertised range of my recently bought YIG oscillator is 1.1 - 3.4 GHz.

On my spectrum analyser, I found 2 resonances, spaced at about 1 GHz and 2 GHz from the main peak (see picture below were the first resonance can be seen at about 2GHz).

That means that the resonances fall inside the advertised range.

In the other YIG oscillators I bought, there were resonance only beyond the advertised range. Is it normal or is the oscillator damaged ?


texts: Find tuned vertical movement component for arduino

texts:
I have an automation test setup which uses pneumatics for pressing a button (ordinary push button, like the one on an Arduino uno) on the test devices. I'd like to replace the pneumatics with a smaller, if possible, electrical component, which could be controlled by an Arduino uno.

I read on the web, that people mostly use a servo motor or a solenoid in such cases. With a servo motor I'd have to somehow convert its movement to a vertical movement and the solenoid does not offer fine tuned movement, so I'd like to avoid these two.

Does somebody know of another component which might be helpful in such case?

Thank you in advance.


texts: Shot or thermal noise of a MOS transistor

texts:
I'm trying to compare the shot and thermal noise contributions in a MOS transistor.

In the literature, the above-threshold MOS transistor has only thermal noise, which is found by integrating the noise of infinitesimal lengths of the channel that behave as resistors.

Of less importance is shot noise, which is said to appear only in the subthreshold region, so for very small drain currents.

Well, when I model the transistor as in the picture below (thermal noise current instead of voltage to get a direct comparison between the two sources), for \$V_\mathrm{DS}\$ above \$2\mathrm{kT}\$ (about \$50\mathrm{mV}\$), the shot noise current is bigger than the thermal noise current no matter what resistor I use. Thermal noise gets bigger than shot noise only for drain-source voltages below \$50\mathrm{mV}\$.

This is not a surprise, since I've found before that the shot-thermal crossover when the voltage is comparable to \$\mathrm{kT}\$ can be used as a very good thermometer: here are some references

Lafe-Spietz et al. (2003), "Primary Electronic Thermometry Using the Shot Noise of a Tunnel Junction".
Blanter and M. Büttiker ("Shot Noise in Mesoscopic Conductors" (refer to page 18 for the explanation).

From the multiple realizations of shot noise thermometry, if I model the mos transistor in a similar way, it seems that shot noise should dominate at voltages above \$50\mathrm{mV}\$.

Why is it necessary to integrate over the channel to get the thermal noise? Wouldn't dividing the drain-source voltage by the drain current be enough to get the resistance used for thermal noise calculations? Or the differential resistance? In both cases I get a shot noise dominating the thermal one for \$V_\mathrm{DS} > 50\mathrm{mV}\$.
Is it correct that shot noise is a larger contribution than thermal noise for \$V_\mathrm{DS} > 50\mathrm{mV}\$?

EDIT: there's a shot noise limit for tunnel junctions and for mosfets in subthreshold, but for 3N163 at 3K, there isn't. At least not according to this document https://ntrs.nasa.gov/search.jsp?R=19810012750   (Cryogenic switched MOSFET characterization)


texts: 1-Wire bus implementation in PIC18F series for Parallax ColorPAL #28380 sensors

texts:
I've bought a Parallax ColorPal 28380 color sensor,
http://www.parallax.com/Portals/0/Downloads/docs/prod/sens/28380ColorPAL.pdf

In the documentation above, they've used a Basic Stamp microcontroller, and I want to use this sensor with Microchip's 18F (18F2550 or 18F4550) microcontroller series.

The problem that I've been experiencing is, the sensor communicates in 2400-7200 bps range.
I can't use PIC's own UART unit because the sensor has 1 pin only.
First thing that came into my mind is using 1-wire protocol but it is operating at 15400 bps which is too fast.

Now I'm wondering, if I place a diode in front of TX line and merge it with RX line, is this setup works ?
Or is there any way to control the transmission speed of the 1-Wire protocol ?

Thanks in advance,


texts: Why does the Tx pin of an USB to TTL adapter provide current?

texts:
I'm currently making a little electronic board on my own. On it, a microcontroller: an ATmega328p running with 5V. To communicate with a computer, I've planned to use an XBee, but for now I'm using simply an adapter TTL <-> USB based on an FTDI FT232RL chip (here).

The problem is, no matter if the power is plugged to my board or not, as soon as I plug this serial adapter to it, a little LED used to display whether my own board is alimented or not lights. After verification, the TX pin of the adapter is guilty: from it flow almost 11 mA.

The problem doesn't seem to come from my home-made electric board, since with an arduino, the same issue occurs. Moreover, the programmer (an USBasp clone) heats a bit, and I have the feeling my serial adapter is responsible...

How can I fix this ? Is this normal ? Couldn't it damage my microcontroller ?


texts: DC Motor and Relay in series with each other

texts:
First off thank you for any comments or answers, I've been reading quite a bit on here and it's helped me a lot which is very much appreciated.

Secondly, apologies if I've made any obvious mistakes / stupid errors. I'm only about 4 weeks in to playing with electronics and even had to remind myself what Ohms law was at the start!

I'm trying to design a signalling system for a model railway which is a fairly trivial problem except that I don't really want to power the trains with a battery. So while the downstream logic circuits are all fairly simple with relays being fed from a nice clean 12v dc supply, the track circuit which detects the presence of a train and also provides power to the motor is confusing me.

The below diagram is very simply what I have at the moment...

I wasn't sure what the simple for a dc motor was and so I have put an inductor and variable resistor in parallel.

The push switches here just represent the train wheels, so they are always both closed or both open.

The Relay is an Omron G2R-2, 12 V dc relay with a 275 Ohm coil resistance.

The motor is a 6V 0.5amp motor (that's the current plan anyway). This one... http://www.nigellawton009.com/6VMicroMotors.html

And I intend to control it via Radio Control using the RX45d-v5 found here: http://www.micronradiocontrol.co.uk/rx_dt_land_v5.html#dt_rx45_v5

So, my questions...

Could anyone kindly please point me in the direction of a good learning resource for dc motors? I'm struggling to find decent information that's not a manufacturer extolling the virtues of their particular brand.
When a motor says '6V - 0.5A' is this normally the peak current? i.e. does it guarantee that the inrush current on start up won't exceed the 0.5A value?
I'm assuming that the 6V of the motor is the maximum value and the controller is effectively a very complicated variable resistor to control the motor speed by controlling the voltage to the motor. Have I got this wrong? My intention was to have the flyback diode over the relay be a 12V zener and have an 18V power supply to leave 6V for the motor. Would I need another resistor in series (R1) or do motor controllers tend to handle this internally, drawing a constant 6V and only feeding the motor what is required?

With the motor being 0.5 Amps, I've obviously got to find somewhere for this current to go. I'm not worried too much about spending extra on bigger Watt resistors or such and the circuit will only be closed for about 5% of the time. So plenty of time for things to cool down between energisations. However I'm obviously keen not to break things.

The relay is rated at 0.43Amps, but is this just what it draws normally? i.e. 12/275? Would it be able to cope with an additional power load through it and is that even physically possible if I've pegged the voltage at 12V with a zener and the coil is a static 275 ohms?

The zener diodes I have are 1N5349B - 5 Watt - 395mA max current data sheet below:

I honestly have little idea how to read these.

Is it saying that at 12V the diode will start to conduct in the reverse direction and start out at approx 1mA and 2.5 Ohm of resistance and then, as the current increases, it will be stable all the way to 395mA at which point the diode will have a resistance of 125 Ohms and then any more current will make it go pop? In my mind 395mA at 125 Ohms is 49V, so i assume I'm missing something here?

In which case, is it a very simple thing to add a resistor in parallel with the relay coil to take up the extra current that can't be fed through the coil and diode combination?

Where I plan to use 18V - 12V accross the relay and 6V across the motor (if htis proves to be correct), would it be sensible to use a higher voltage supply and add a current limiting resistor? i.e. 24V supply, 12V across the relay, 6V across the motor and 6V across a 6Watt, 24 Ohm resistor to ensure the current stays at 0.5 Amps and no higher.

Sorry for the very long winded question, any help at all would be very much appreciated. Many thanks.


texts: post equalising technique &opamp circuit

texts:
I have tried to construct this circuit  in LT spice as to compensate the imperfect of DAC of my DDS function generator,for my case fs=125MHz,thus C=6.6pF, and the result as shown :, how do I verify it have compensate the sinc response by looking this result? and then when I am trying to change the resistance value to change the gain,the result become like this :, but the gain still zero..so anyone can explain why the result will look like this? and I am trying to figure the formula for that circuit by google,but it end up with nothing,so anyone can explain it by using formula?

In order to achieve 20 VPP output for 0 to 5MHz,an non-inverting circuit have been designed as shown:


texts: Question on UART parity check verilog source code

texts:
Why is parity_value equal to value of 1 ?

check_parity verilog source code

module check_parity(clk, serial_in, received_data, data_is_valid, is_parity_stage, rx_error); // even parity checker

input clk, serial_in, data_is_valid, is_parity_stage;
input [7:0] received_data;
output reg rx_error = 0;

reg parity_value; // this is being computed from the received 8-bit data
reg parity_bit;  // this bit is received directly through UART

always @(posedge clk)
begin
    parity_value <= ^(received_data);
end

always @(posedge clk)
begin
    if (is_parity_stage)
        parity_bit <= serial_in;
end

always @(posedge clk)
begin
    if ((data_is_valid) && (parity_bit != parity_value))
        rx_error <= 1;
end

endmodule


texts:
I just obtained an old rotary phone at a garage sale. I am working on hooking it up to an arduino project, and I was able to get the dial and hook switches figured out pretty easily. I cannot really figure out how the ringer works, or how to wire it up.

It is an old western electric C4A ringer. It has two bells and a striker arm between them. There is a coil, and some magnetic plates that move the ringer, with four wires going into the coil. I have found schematics online for how the thing connects to the other phone components for normal operation, but I really just wanna figure out how to make the thing ring on its own.

I read that most phone lines run in the vicinity of 90 volts ac. Is there any possibility I can make this thing ring with a 12 volt wall wart, or am I gonna need a full 120 line and a relay or something?


texts:
I have :

 four outputs :
  a, b, c, d ( four output pins )

Assume I have one insect, let us say it jumps one step at a time and I can control its direction.
If input DW = 1 it goes right to left; else it goes left to right.

 clock clk :
 DW = 0
 ( clock goes left to right  )
  0  1  1  0 ( means b,c  = 1, assume rightmost-1 is head of the insect and it goes right )
  0  0  1  1 ( now, c and d are  1 )
  1  0  0  1
  1  1  0  0
 after operation on  combinational and sequential  circuit
 DW = 1
 clock clk :
( now, it goes right to left )
  1  1  0  0 ( a, b = 1 ) ( assume leftmost-1 is now head of the insect and it goes left )
  1  0  0  1 ( a, d = 1 )
  0  0  1  1
  0  1  1  0
  1  1  0  0

How can I construct that circuit ? To construct it, which topic I should (re) read or Can you recommend any web-page?


texts: Can a combinatorial hardware circuit with no inputs solve a crypto problem?

texts:
I am noob at electronics but in short I am interested in stable states of circuit with
no inputs which represents a boolean formula.

Let \$f\$ be some hash function, say md5. Restrict the size of input
to be equal to the output (128 bits for md5).

Cryptographer told be it is open problem if there is
solution to \$f(x)=x\$ (treated as sequence of bits).

Implement \$f\$ as pure combinatorial circuit (NO CLOCK),
with 128 \$i_k\$ inputs and 128 outputs \$o_k\$.

For all \$j\$, connect \$i_j\$ with \$o_j\$ so the circuit
doesn't have inputs(basically
loop the circuit \$f\$).

Power on.

Measure (possibly with oscilloscope) \$i_j=o_j\$.

If you are lucky to hit stable state (logically consistent), you have solved
\$f(x)=x\$.

In an unstable stable (no solution), maybe one will measure very
high frequency.

Probably this is well studied, though an
engineer couldn't find reference for the general case.

  Are there references for this?
  If it fails why will it fail?
  If a solution exists is it known for how long it
  will be found?
  If this makes sense, would please someone try it on something
  simple, though not entirely trivial?

Partial experimental results:

It wasn't easy, but me convinced an engineer to test it
on bare metal.

Take \$n\$ inverters (logical negation) and loop them
in a cycle (basically this corresponds to the cycle
graph \$C_n\$).

There are no input and no outputs.

For even \$n\$ the circuit has exactly 2 stable
states.

For odd \$n\$, there is no stable state since
the boolean formula is unsatisfiable.

The engineer worked with NAND gates on a stand.

Experimentally, for \$n=4\$, the engineer reached
stable state.  Depending on which NAND gates he chose,
the stable state differed.

For \$n=3\$ there was no stable state.
The voltage was in the middle between logical 0-1,
possibly with high frequency which his oscilloscope
couldn't measure.

I wouldn't trust a software simulation for this,
might be wrong.

The experiments were too trivial, so it is
possible electric current to solve easy problems
and not solve hard problems.

Someone suggested this is "adiabatic bruteforce", though
still can't find the right search terms.


texts: How to go from 12VAC to a micro USB cable

texts:
I have a 12VAC dynamo I am planning to put on my bike and I want to know how to transfer the electricity generated into a Micro USB cable or USB port. There are devices out there costing upwards of $100 to do this but I want to know if there is a cheaper way for me to construct something like this.

UPDATE:

The design I had and device I had originally designed worked, I was just using a faulty USB cable.


texts: Very basic questions on resistor and gnd

texts:
Im a total beginner. I bought an arduino starter kit and this is the first sample program - it makes an LED blink. The accompanying text gives no theory about what is happening in the sample programs so I have a couple of questions.

What is the function of the resistor here?
Why is it a 560 ohm resistor (as opposed to 2 ohms or 20000 ohms)?
The circuit starts from arduino pin 13 that I understand puts out a voltage of 5 Volts. But the circuit then ends at gnd. I thought circuits were supposed to loop around so that the currently will keep flowing non-stop? What is the reason for the circuit terminating at gnd?

Here is the circuit -


texts:
I have built the following circuit -

first, I soldered together all the mt3608 components on PCB and tested it (I created DIY voltage step up module), then using jumper wires I connected the battery module to the circuit and the Peltier.

The circuit is designed to deliver 6.6V to the peltier, without the load (the Peltier), it does its job successfully (V7,8=6.6V), but, after connecting the Peltier, I measure only 1.7V (and 300mA) on pins 7 to 8 (voltage drop on the Peltier module).

Why does that happen and how can I get the Peltier to be fed with the original output of the converter of 6v?

Datasheets-
mt3608 - https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf
Peltier - https://peltiermodules.com/peltier.datasheet/TEC1-12706.pdf


texts: EAGLE - how to make ground planes to connect to the smaller PADS

texts:
I cant fid how to configure the GND polygon to connect to smaller IC pads:

EDIT
Following the @Dave Tweed answer the result is exactly as I need:


texts:
I've been looking for a monolithic battery charging / load sharing PMIC that is designed to work with up to 3 or 4 LiFePO4 cells. I had a search on Digikey and could only find one ($6!) chip and that only worked with a single cell.

Ideally I am hoping to charge them in series and keep them balanced.

Does such a thing exist?