texts: How can I solder LCD Pins when solder does not "stick"?

texts:
I have a 16 * 2 LCD Display, with 16 input pins. However while I am soldering the pins it it does not stick or "take".

How can I fix this?

Is there any other metal for soldering a display ?


texts:
A user already asked a question about it at TL431 Constant current source. My SPECIFIC question is about the figure 29. Sure it is not a complete circuit, so I completed it, in order to understand it, with two resistors, R3 and R4, as place holder for possible "useful circuit".

And sure, AM1 shows that the current through it is roughly constant (I am using TINA(TM) de Texas Instruments). Also note that AM2 isn't:

So, the net effect can be accomplished without using the transistor, with a single diode, as shown here:
And yes, not shown, but AM1 will still be constant.
In fact, if we use nothing, and no connection between R3 and R4, AM1 is constant, as it should.
So my question: what is the use of that transistor since it does not help in sinking a constant current between R3 and R4 (which was, I thought, was the purpose of the building block) and since a single diode can do the job ( maybe at a higher expense of energy though ) ?
Note that I varied R3 and R4 with 3 steps each, producing 9 cases, but similar results occur if I use a larger number of steps.


texts: Is this implementation of activating of boom-arm vehicle barrier correct?

texts:
Previous Post
From my previous, I asked about how the trig pin works on the boom-arm vehicle barrier. I would like to know if the below circuit is correct?
This circuit assumes the boom barrier opens when the trg pin is grounded. The relay is a 12V DC 10A relay.
The circuit uses an Arduino to trigger the boom barrier via a relay by using a MOSFET. So in theory when the Arduino is HIGH the MOSFET activates and de-energizes the relay. When the Arduino is LOW the MOSFET is opened and therefore will energize the relay thus grounding the trig pin.
The figure suppose to say boom-arm vehicle barrier, not driveway gate, but they use the same setup.

simulate this circuit – Schematic created using CircuitLab
Updated schematic


texts: 3.7 to 5 V boost converter does not work as desired

texts:
I was trying to boost 3.7 V to 5 V @ max 1A.
Used LTC3426 DC-DC converter for it.
LTC3426 datasheet here.
I made a simulation before printing PCB and I get the voltage I needed.
However, now I have the PCB and it is not giving the desired voltage.
Simulation Circuit:

Graph:

Actual Circuit:

I dont know why, I get only 3.8 V not 5 V.
My current battery voltage is 4 V also it is not different.
I checked shdn pin of the converter and it is on HIGH state.
I removed D3 diode on schematic and nothing has changed.
I changed the inductor to 220 uH(normally it is 2.2 uH and nothing has changed.
With Vcc signal I run microcontrollers or similar 5 V operating voltage devices which means I have load also.
What is the problem? Where is my mistake?
Update:
I changed the resistors to the values which are given in the datasheet

But my inductor was 22uH
I got 5v finally. However after some time like 3 seconds, the regulator burned!
Is it because of the 22uH inductor? Because on the reference design it is 2.2uH.
I dont think it burned because of high current consumption. Because the other part of the circuit is just Atmega2560 and SIM808 chips and some sensors. I think this devices does not need too much current to break the regulator.
The layout of the regulator is(u2) is the regulator you can check it from the schematic on above post:


texts: Why are induction motors controlled with a constant V/f?

texts: It seems that induction motors are always controlled using a constant ratio of voltage over frequency. Why is that? Take the classic torque-speed characteristic curve - varying the frequency shifts it sideways such that it's possible to start the machine, and control it at any operating point within the frequency and rated torque limits. What advantage does that give?


texts:
I have an H-bridge I am driving with an Arduino Mega.  The motors I am driving are fairly large, steady state 48 watts, maximum 300 watts.  I am driving them at 16 volts and a switching frequency to the H-bridge of 30Hz (The lowest the Mega will go.) As I try to increase the switching frequency of the PWM for the H-bridge, the motors seam to lose more and more power the higher the switching frequency.  I suspect this is due to the impedance of the motor increasing with the switching frequency of the bridge.
H-Bridge
Can anyone help me to understand if I need to add capacitors to the H-bridge outputs to smooth out the current pulses to reduce the motor impedance?
Also at work we are driving the same motors at 20kHz right now and they are having no issues,  so I am confused as to what I am missing.


texts: What are the use cases of FIFO Half-Full and Three-Quarter Full interrupts in Receive FIFO of a UART?

texts:
I am implementing a protocol decoder which receives bytes through UART of a microcontroller. The ISR takes bytes from the UART peripheral and puts it in a ring buffer. The main loop reads from the ring buffer and runs a state machine to decode it.

The UART internally has a 32-byte receive FIFO, and provides interrupts when this FIFO is quarter-full, half-full, three-quarter full and completely full.

How should I determine which of these interrupts should trigger my ISR?
What is the trade-off involved?

Note - The protocol involves packets of 32-byte (fixed length), send every 10ms.


texts: How to use a MUX DEMUX to communicate two circuits?

texts:
I'm trying to reduce two circuits with 14 connections to only 3. I was googling for hours and I read a lot about multiplexor and demultiplexor. But as is my first investigation in electronics (I'm a really noob) I can't found a solution to this.
My near aproximation to resolve this problem is the following one (is a concept/analogy, not the real circuit).

Any help or comment will be preciated as any answer!
Thanks in advance


texts: Why does Intel looks so advanced compared to other foundries, engraving fineness-wise?

texts:
Latest chips from Intel were 22nm, and they are now targeting 14nm (coming in 2014 or 2015 it seems).

On the other hand, Global Foundries or TSMC struggle since several years to go beyond the 28nm for their clients (mostly Nvidia and AMD, as I can tell from reading news about GPUs). They have delayed 20nm for quite a long time.

Why is Intel (or looks like) so advanced compared to GloFo or TSMC ?


texts:
I was doing the transient analysis experiment with the Series LCR circuit, and my mentor asked me some questions, which I don't have a clue about. I read but did not get any rigorous satisfactory answer.
the very basic question was, (1) Why we use square wave instead of the sinusoidal wave to study the transient response?
why can't we perform this study using a sinusoidal wave? (I was using CRO)


texts: Change Pilkor MKP 10nF with WIMA MKP 10 10nF Capacitor

texts:
I need your help with capacitors...

I'm restoring a 160A inverter welding machine, model Fimer X164. One of the capacitors has cracked and I need tochange that..

Information about the capacitor on the board (i.e. exploded):

PILKOR 10nF 300V-Y2 PCY2 130 MKP

I can't find an identical capacitor but find similar values.

I have

1- WIMA MKP 10 10nF 400 630

Can I use capacitor? Or what do you suggest as a replacement for this capacitor?

THANK YOU FOR ALL Answers other question:
About MKP Capacitors for Inverter Welding Machine


texts: External diodes for Solar panels in parallel

texts: I have two solar panels, same brand same model and same voltage and current characteristics. I wish to connect them in parallel. Must I use an external diode? I have checked, they have two diodes within the electrical terminal box.


texts: what to do to prototype with logic gates?

texts:
I have a couple of fun electronics projects I have designed, very simple, that require some logic (i.e. cascading 555 timers and doing different things with logical combinations of their outputs).

I would need to use some AND/OR/NAND/NOR gates as well as some inverters, but it's not obvious to me what people normally use to prototype these. I've seen where to buy ICs containing gates, but looks there's not a lot of single gates available, they normally come in ICs with a few of the same type, and many times I just need one or two, and would prefer to not "waste" an IC containing 8. Also there are some options for through-hole, but not that many. For example, I inverters seem hard to find to mount through-hole. I have also seen IC with multifunction gates or mixed types of gates. I wonder if this is what's useful to have a bunch of spares of.

As an extra question, many times the same simple logic that I refer above can be recreated with a mux/demux. In cases like this, is there a preferred way to do it (logic gates VS mux/demux)?

Note: I know how to create logic gates from transistors, but that's not what I'm after.


texts:
I am planning on ordering a panel with four different designs on it. Two were made in Altium, while the other two were made in Eagle.

Altium has a great tool for panelizing boards designed in it, but I don't believe it can put designs from other programs on the panel.

How can I panelize these PCBs?


texts: Basic Capacitor Question To help Cement My Foundation Properly (LTSpice)

texts:
I have the following circuit in LTSPice.  I can see +- 3.5 uA of current at various nodes.  I should be able to calculate the 3.5 uA given the R and the C.  I note that the sim output is sinusoidal.  If there were no battery in the circuit, I would not be posting this question.

So what is the question....

My question is, in a simple easy to understand chunk of words, what is the effect of the battery on the circuit and why?

I understand that the capacitor will pass ac current.  I understand the capacitor will block dc.  I can look at the RC and frequency and can (probably) figure out how much charge the capacitor accumulates between cycles.

The basic foundation I am stuck on is the following....

At the peak of the first positive cycle, both sides of the capacitor should have 10 volts on it and hence no current or charge occurring.  Battey always supplies 10 volts DC.  Prior to this point, maybe it discharges?  If so, where, into the ac source?

When the AC flips polarity, it looks to me like a signal rising to 10 volts is going into a battery, which looks to be in series, so 20 volts on the capacitor this time?

In ltspice, i look at the voltage between v1 and r3, it is at a constant 10 volts.  I would think it should show a rise to volts?

In ltspice, i look at the voltage between r3 and c1 and it appeats to have a sinusoidal signal on it on 10 volts varion +- 15 millivolts.

Why is this sinusoidal and not showing more current (20 volts) on one side and less current (10 volts) on the other?

Thanks for some basic clarification.


texts: Coplanar waveguide for differential trace calculator

texts:
Although there are plenty of free impedance calculators out there, I'm struggling to find one that can solve impedances for a differential pair using coplanar waveguide. Anyone know of any free software that can do that? The only one I was able to find was Si9000 and Si8000m by Polar instruments, but they aren't free.

Reason I'm interested is because I'm trying to route USB 2.0 HS signals on a 2 layer 1.6mm FR4 board and want to see if using coplanar waveguide will make it more practical (i.e. thinner traces).

Amr


texts:
I got some oem switches and I want to mod them into light switches.

Here is my situation:

I would like to use the oem switch since it has illumination and button that matches the car.I have already located the illuminations and found out the switch is momentary.

I'd want them to operated as on/off switches.
Here is the diagram for the lights and the included switch:
https://dl.dropboxusercontent.com/u/6569565/Forester/2014-12-09%20201.jpg

The momentary switch has 2 wires, but the included switch has 3, + - and ground.

So far I've found latch relay and ic jk flip flop would work, but they are too complex (I can't seem to find the right diagram for my needs). Are there any pre made relay for my purpose, 12v?

Edit by Kamil:

I've found this one on the net, but it's for 5V: link

and can someone list the parts that are in this circuit?

Mainly the spec for the jk flipflop? For 12v tho.


texts: Best device to read/write memory on multiple architectures?

texts:
tl;dr: I want to read/write memory from a PIC MCU and an EEPROM, both of which are soldered to an experiment board. I would like to explore programming and debugging ARM in the near future. Which device makes the most sense for me to invest in that does both (if this is possible)?

PART I

I'm attempting to reproduce the exercises from an introductory hardware class I took recently before I take on something more advanced. The board in class used a PIC16(L)F1847 microcontroller and a 24AA512 EEPROM, both of which are soldered to the board.

As I'm starting to build my tool library, I'm interested in which device(s) would be best suited for me to:

Read/write memory to the 24AA512 I2C EEPROM
Read/write the existing code from the PIC16(L)F1847 MCU
Eventually transition to debugging/programming ARM MCUs

I'm looking at the MPLAB Starter Kit for Memory Products and the PICkit 3 Starter Kit as possible options. However, it's not clear to me whether I can read/write the code stored on the PIC16 (presumably this is in on-board memory) and of the detached EEPROM using either device.

From what I can tell, it appears the MPLAB Starter Kit for Memory Products simply read/writes memory and does not debug, while the PICkit 3 Starter Kit appears to program/debug PIC ICs and not EEPROMs.

Is that correct?

PART II

A friend suggested I skip PIC altogether, go straight to ARM, and pick up the J-Link EDU debugger. However, since I want to refresh the knowledge I learned in class, I'm curious:

Can this device be used to read/write memory stored on the chips above?

If so, it seems this would the right way to go considering my interest in starting with the PIC experiment and then moving on to ARM as suggested.


texts:
I have an RF 443.92 MHz transmitter and the receiver, the model is TWS-DS-3 and I'm trying to understand how does it works. There are 4 pins (GND, Data In, Vcc, ANT), I'm going to wire the Vcc on a 5V power (of a Raspberry Pi), the GND on the GND and the Data In on a digital output GPIO that provides 3.3v logic level. What happens when I set the Data In pin to the HIGH state ? It will set the receiver Data Out to the HIGH state too after transmitting ? Do I need any resistor to limit the current between the GPIO data pin or in the Vcc pin ?

Update: I just plugged the receiver RWS-375-6 into an Arduino with the "Linear Out" pin on an analog pin and the TWS-DS-3 (transmitter) I plugged into a Raspberry Pi, when I set the pin to a HIGH state the output on the analog output of the Arduino is this:

The peaks are when I set the GPIO pin (which is connected into the Data In of the transmitter) to HIGH state, sleep 100ms and then turn it LOW and wait for 1 second.

If someone is also interested, here is the wiring I've done on the Raspberry Pi:


texts: Current consumption of a current transducer (LEM LA 55-P)

texts:
I have a question regarding a current consumption of a current transducer (LEM LA 55-P). In the current transducer datasheet it says that the current consumption at \$ \pm 15~\text{V} \$ is \$ I_c = 10 + I_s~\text{mA} \$, where \$ I_s \$ is the secondary current (in my case, up to \$50~\text{mA}\$). This means that the current consumption is \$ I_s = 60~\text{mA} \$.

This current transducer has 2 supply pins:

\$ V_{sup} \$ (in my case \$ + 15~\text{V} \$)
\$ -V_{sup} \$ (in my case \$ - 15~\text{V} \$)

I was wondering, what is the total power consumption of this transducer:

\$ P_c = 15 \cdot 60 + 15 \cdot 60 ~\text{mW} = 1800~\text{mW} \$, or
\$ P_c = 15 \cdot 60 ~\text{mW} = 900~\text{mW} \$

In other words, is this transducer going to draw up to \$ 60 ~\text{mA} \$ for every supply pin, or in total. If this is total consumption (for both supply pins), can I except that the transducer is going to draw equally on each supply pin, i.e., \$ 30 ~\text{mA} \$ per supply pin?

Thanks, M.


texts: DIY Power supply kit suggestion (Fan & pull-up resistor, cap)

texts:
I bought this 0-30v power supply DIY kit... There is three suggestion I need...

1. I want to use a 12V fan, so I'm changing the 7824 to 7812. So, I'm thinking to change the pull-up resistor (2.2K) to 1K/1W. Is it right? (as \$V =I * R\$)

2. I don't know about this heat-sink plate... Should I use heat-sink paste also?

3. For C1, can I use 2200uF instead of 3300uF? The provided capacitor is okay but came dented, and I have some 2200uF capacitors handy. (Is there any equation to get capacitor value?)


texts: Are AVR multi-cycle instructions pipelined?

texts:
Since AVR is a RISC architecture, most instructions only take a single cycle to execute. Still some need two or more cycles, e.g. adiw, which performs 16-bit addition, or ld to load data from SRAM.

Do these execution times denote only the latency of these instructions, or does the processor actually wait this long before moving to the next instruction?

Could I run, say, 6 two-cycle instructions, and the entire code would still only need 7 cycles to run?


texts: Using ESP32 as a2dp sink and access point at the same time

texts:
I am trying to make a project where bluetooth and wifi collaborate with each other. Precisely I want to use the a2dp profile to stream the music to one esp, from there via UDP sockets to N esp's.

I am at a point where I thought I would be done, but when I try to send the received data from my phone over the socket, the access point is crashing. It seems like the whole resources are used to power the a2dp sink.

Does anyone has any ideas? Is this technically achieveable? If yes I surely have something in my code.

Appreciate any help.

Here's my code: https://github.com/Dimfred/esp32_bt_streamer

I am using the esp32-wroom btw.


texts: Adding footprints to multiple components at once in Altium

texts:
I have a library with a few hundreds of passives, each with 2 footprints (ie. 0603_IPC_A, 0603_IPC_B).
I want to replace these footprints with new ones from a different library. Is there a way to do it for multiple components at once so I don't have to traverse them 1 by 1?
I tried through SchLib List panel, but there is no column "footprints", only "current footprint" which when changed to a new value "A" just adds "A" to the available footprints.
Thanks


texts: Modelling of center tapped transformer in SPICE and driving it with switches

texts:
I am using SPICE engine (LTSpice) to model a center tapped transformer and then drive its primary side (center tapped) using MOS switches as follows:

What I am expecting to see at the output terminals is the amplified square-wave given at the input. However, my output under this configuration is a high voltage peake around 40V and then just flattens. It is possible to get an alternating triangular waveform by changing the inductance values and R2 and R3 but still not even close to what I need to produce. I understand the 0.98 parameter adds a leakage inductance at the primary center tapped side of around 0.01 times Lp1 but do not exactly know where in circuit it resides (schematically).
So any answer to following questions is very much appreciated:

is my modelling of "center tapped transformer" in SPICE, an accurate representation of real world transformer? If not, how do I change that?
Assuming the model is correct (or corrected), how can I model this circuit for hand calculations? i.e. from the moment M1 opens, what network should I consider my load to be in series with R2 in order to write differential equations etc for a solution of voltage/current in time domain?
Finally, I understand I may need freewheeling diodes connection in primary side for current escape. Where should I put the diode in primary side?

Any additional insight (considering my intention mentioned above) is also appreciated.

P.S. the input frequency is 1MHz

EDIT1:
by choosing: Lp1 = Lp2 = 2.5 uH, Ls1 = 10 uH and transistor component of SI7336ADP, following result is observed:


texts: Do I need to suppress ringing in a flyback converter?

texts:
I am about to design a flyback converter.
As all flybacks with no extra measures it has some ringing.
You can see that ringing in this example from -1µs to 4µs:

This ringing can be surpressed by a snubber (common measure to cancel this type of ringing.) The drawback might be a bit less efficiency of the flyback converter.
Here would be an example of the snubber which I would implement, if the ringing should be canceled:

-Is it necessary to cancel it due to EMI emissions?
-Do some of you have experience with bad side effects of such a ringing, when not canceled?
Edit (clarification): The green circle marks the ringing.


texts:
its a small question ...i got on my cell charger the indications as follow:

input:100-240 V 50-60 Hz
output: 5 V DC 1 A....

the question is what does the 1 A mean? i am new to circuits and etc..when plugging the cell then the current is created by the cell's total resistance and stuff so what does mean the 1 A mean in the charger indication?


texts: Testing a board without placing a component

texts:
Is there a way to build a (functional) board without placing 1 component?

I am designing a PCB and want to have the option to make it work w/ or w/o placing a specific component (X). This component X doesn't impact the main feature of the board.

One solution of this problem is using a jumper - design in a way so that the jumper on/off can make the circuit close/open. But I don't want to use jumper in my board.

Any other approach?


texts: Onboard charging system for hybrid electric tractor

texts:
I’m in the process of converting a Cub Cadet SLT1554 from gas to a hybrid-electric tractor using a Motenergy ME0909 PMDC Motor. See description/specifications below:

Motenergy ME9090 PMDC Motor
12-48V, 4 hp cont, 12.8 hp pk
4 Hp Brush-Type PM DC. 4000RPM at 48VDC

The Motenergy ME0909 is a Brush-Type, Permanent Magnet DC motor with very high efficiency. Capable of 4.8 KW continuous and 15 KW for 30 seconds. For voltages from 12 to 48 VDC input and 100 amps continuous (300 amps for 30 seconds). Designed for battery operated equipment. It makes a great replacement for the original Etek motor because it has the same  bolt pattern and is actually lighter in weight.

Specifications

Power: 4 cont - 12.8 pk hp
Voltage: 12-48 Volt rated
Speed: 2150-4850 rpm
Size: 6” OD, (w/o shaft)
Shaft: 7/8” x 1-3/4”, 3/16” key
Weight: 24 lbs.

Voltage Constant: 0.0107
Revolutions per volt: 93.45 RPM
Torque Constant: 0.102 Nm/Amp
Generated Current: 9.8A per Nm

If possible, I would like to operate the electric motor at 24 volts powered by two 12-volt deep cycle batteries in series.

At the same time in order to guarantee sustained power, I would like to have an onboard generator powered by an 8hp I/C horizontal shaft engine driving a 12 volt, 253 amp alternator recharging the batteries. I’m under the impression that I would need at least 2,984 watts of electricity to create 4hp, and 3,730 watts (5 hp) would be even better.

QUESTION: Is it possible to create some type of configuration so that a 12v alternator can charge two 12-volt batteries in series. Also, I’m concerned that the ME0909 ad speaks of only 100 amps for continuous service.

Would the battery not act as a “cushion” between the alternator and the electric motor?

Any assistance in this project will be greatly appreciated.


texts: Rule of thumb for boost converter current usage

texts: I have a sensor that requires 12V DC for 14 seconds. I only have a 6V source. The device pulls 6.2mA at 12V during the 14 seconds. If I use a boost converter to get to 12V should I assume >12.4mA usage during the 14 seconds ignoring the boost converter efficiency for the moment?


texts:
I am trying to create a counter that starts counting when a start signal goes from 0 to 1. Then, I want the counter to keep counting until both the start and stop signal are 1. Once both signals are 1 the counter should reset to 0.
I am confident that the reason my counter does not reset is because of the "else if (start && stop)" statement.
Thanks for the help!
Here is my code:
module count2     (
out  ,   // output of counter
start ,   // start pulse
stop,     // stop pulse
clk  ,  // clock input
reset    // reset input
);

input start, stop, clk, reset;
output out;

reg [7:0] out;
reg [7:0] counter;

always @ (posedge clk)
if (reset)
begin
    counter <= 8'b0;
end
else if (start)
    counter <= counter + 1;
else if (start && stop)
begin
    counter <= 8'b0;
end
endmodule

Here is my tesetbench:
`timescale 1ns/100ps

module count2_tb;

// parameter SYSCLK_PERIOD = 20;// 50MHZ

reg clk_1;
reg start_1;
reg stop_1;
reg reset_1;

wire [7:0] out_1;

initial
begin
    clk_1 = 1'b0;
    start_1 = 1'b0;
    stop_1 = 1'b0;
    reset_1 = 1'b1;
    #20;
    reset_1 = 1'b0;
    #20;
    start_1 = 1'b1;
    #50;
    stop_1 = 1'b1;
    #50;
    $stop;
end

//////////////////////////////////////////////////////////////////////
// Clock Driver
//////////////////////////////////////////////////////////////////////
always
    #5 clk_1 = ~clk_1;
//////////////////////////////////////////////////////////////////////
// Instantiate Unit Under Test:  counter
//////////////////////////////////////////////////////////////////////
count2 count2_0 (
    // Inputs
    .start(start_1),
    .stop(stop_1),
    .clk(clk_1),
    .reset(reset_1),

    // Outputs
    .out( out_1 )
);

endmodule

Here is my waveform output from ModelSim:


texts:
I'm currently working through some convolution examples and I'm unsure of something.

The question is given as:

  Consider the input \$\ x(n) = u(n) \$ and the impulse response \$\ h(n) = (0.5)^n u(n) \$ for a certain system. What is the output of the system?

From the convolution equation, I understand that the first step produces:
\$\  y(n) = \sum\limits_{m=-\infty}^\infty u(m)(.5)^{n-m} u(n-m) \$

The question goes on to say:

  But since \$\ u(m) = 1 \$ for \$\ n \ge 0 \$ and both \$\ x(n) \$ and \$\ h(n) \$ start at \$\ n = 0 \$, we have
  \$\  y(n) = \sum\limits_{m=0}^{m=n} = (.5)^{n-m} \$

I understand that \$\ u(m) \$ disappears as it is a constant, but how is \$\ u(n-m) \$ removed?

Thanks in advance for any help on this.

EDIT: Additionally, why do the limits change from +/- infinity to \$\ m=n \$ and \$\ n = 0 \$?


texts: Electronic component that is like an LCD version of an LED?

texts:
Is there a liquid crystal display version of a light emitting diode? I want a visual indicator that is a small and simple 2 pin device like an LED, but instead of emitting light it just turns black or white, or black and clear like how an LCD screen does.

I want to make a solar electronic compass. Its a magnetometer wired up to a solar panel and then to some kind of indicator that turns on when you point north. LEDs would be perfect for the indicator except they cannot be seen in sunlight, and they drain several milliamps which is a bit much for a solar panel.

LCDs can operate in the microamp range which is perfect, and can also be seen in direct sunlight because they reflect light. This seemed like an ideal fit, but most LCD modules I can find are several inches across which is kind of big for what I had in mind. They also involve a lot of pins and complex interfaces. Also the cheapest LCD modules I could find cost about 2 dollars. All of this is a bit much for a simple on-off visual indicator. LEDs cost like 2 cents each for comparison.

After that I looked into 7 segment displays, but almost all of those that I can find for a reasonable price are LED versions that you would be unable to see in sunlight, and would again draw too much power. They make LCD versions of these too, but they seem to be much more rare and expensive. Again you have a lot of pins and large sizes and higher costs.

All I want is a little plastic dot that can turn black or clear when you run some power to it. Does this exist? This doesn't seem like it should be so hard to find. Does humanity not have little black dot technology? We definitely have little glowing dot technology; you can get LEDs in huge packs for cheap in every color of the rainbow. I guess you could call this a "LCD pixel" or "single-segment LCD display" or something like that.

UPDATE: A few people said I was underestimating the visibility of LEDs and overestimating the visibility of LCDs. I decided to test it just to make sure and took a few photos.

Direct sunlight. Left LED is on, right is off for comparison.

Outside but shaded. Left LED is on, right is off for comparison.

Indoors.

I really could see the green LED even in direct sunlight. It was faint, but I could tell that it was on. The LED on the right is completely unpowered for comparison. This LED drew 3.25 milliamps. The LCD I used to compare is a cheap eggtimer I got from walmart for 88 cents.

Judging from the posts here it does not seem like this circuit component exists. The light valve was the closest one and they don't make them small enough to be used for a small indicator.

Could we get this made? Based on the large number of views relative to other questions asked on this site it seems like people are interested in a component like this. Is there any chance that writing to some kind of LCD manufacturer could get something like this made?

I know LCDs run on AC power, but I also know factories can build fairly complex circuity right into the plastic somehow. I have seen LEDs that have built in blinker mechanisms, where you just hook them up to a battery and they automatically blink once per second. The blinking circuit is built right into the base of the LED so small you can't even see it. It seems like they could do a similar setup with some sort of h-bridge to invert the power to AC so the LCD would work even just hooked up to regular dc power.

Another possibility was a "Grating light valve" which uses microscopic metal ribbons instead of liquid crystals. As far as I can tell it runs on DC power. It also looks like the patent is just about to expire.


texts:
I want to build a BlinkM as a simple temperature indicator as seen at
http://thingm.com/products/blinkm/project-gallery.html
Anyone know where I can get a schematic & parts list?   The link on the page doesn't take me anywhere useful.


texts:
Some 20 years ago I created an audiovisual art installation, connecting RCA Video output from a TV set to a HiFi system's audio-in, just plain via cable, in order to "hear" the video signal. Also vice versa, sound from the HiFi system to the TV set, in order to "see" the audio signal.
I was wondering if the first part "hearing the video signal" would be somehow possible nowadays with a laptop having a HDMI output.
There are some HDMI to RCA cables out there. Would it work, to connect the RCA video output jack to the HiFi system's audio in?
Or is there more required? Maybe something like a converter first?
Or are there better solutions to achieve "hearing the video signal"?


texts: Preserving state of variables in RAM on Power Failure

texts:
I'm developing a code with Nuc240(ARM Cortex M0) Microcontroller.
Where I need to store the value in some of the variables to the Internal Data Flash.
I use ISP procedure for this, but i have seen the following statement in the datasheet of the Microcontroller ,about the Data Flash.

  'The size of each erase unit is 512 bytes.'

The Data Flash Memory starts form 0x20000,and if I need to update this location I will have to erase this location first, does this mean that if I erase 0x20000 - memory till 0x20200 will be also erased? and that might result in other values stored in these locations. How can I overcome this situation?


texts: SAMD21 1μs timer handler taking longer than the timer period?

texts:
Before I begin I'd like to mention that I'm relatively new to working with microcontrollers at this low level, so please bear with me.

I am trying to use an Adafruit Trinket M0 to process and generate signals to communicate over the Nintendo GameCube communications protocol. Namely, the SAMD21 microcontroller needs to be able to output bit sequences with a frequency of 1 microsecond. I know this is possible on 16MHz AVR microcontrollers with the existence of this library; therefore I imagine it would be possible to do so as well on the 48MHz SAMD21.

From some research online I found this code sample, based on which I made the following sketch to toggle the output pin on the Trinket M0 every 1μs:

// Physical pin labelled 3 on the Trinket M0
const uint8_t PIN = 7;

volatile uint8_t n = 0;
volatile uint8_t next_bit = 0;

void TC5_Handler(void)
{
    // Toggle pin
    PORT->Group[PORTA].OUTTGL.reg = (1 << PIN);

    // Reset timer interrupt flag
    TC5->COUNT16.INTFLAG.bit.MC0 = 1;
}

void setup()
{
    // Initialize serial
    Serial.begin(115200);

    // Configure pin as output
    PORT->Group[PORTA].PINCFG[PIN].reg = PORT_PINCFG_INEN;
    PORT->Group[PORTA].DIRSET.reg = (1ul << PIN);

    // Enable generic clock for Timer/Counter 4 and 5
    GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 |
        GCLK_CLKCTRL_ID(GCM_TC4_TC5);
    while (GCLK->STATUS.bit.SYNCBUSY);

    // Perform software reset
    TC5->COUNT16.CTRLA.reg = TC_CTRLA_SWRST;
    while (TC5->COUNT16.STATUS.reg & TC_STATUS_SYNCBUSY);
    while (TC5->COUNT16.CTRLA.bit.SWRST);

    // Configure TC5
    TC5->COUNT16.CTRLA.reg =
        TC_CTRLA_MODE_COUNT16 |     // Counter of 16 bits
        TC_CTRLA_WAVEGEN_MFRQ |     // Match frequency
        TC_CTRLA_PRESCALER_DIV1;    // Prescaler of 1 (no division)
    TC5->COUNT16.CC[0].reg = F_CPU / 1e6 - 1; // Trigger @ 1MHz=10^6Hz
    while (TC5->COUNT16.STATUS.bit.SYNCBUSY);

    // Configure interrupt
    uint32_t oldISER = NVIC->ISER[0];
    NVIC->ICER[0] |= ~0ul;  // Disable all interrupts
    NVIC->ICPR[0] = 1ul << TC5_IRQn;            // Clear pending timer interrupt
    NVIC->ISER[0] = 1ul << (TC5_IRQn & 0x1f);   // Enable TC5 interrupt
    TC5->COUNT16.INTENSET.bit.MC0 = 1;          // Match/Compare 0 interrupt
    while (TC5->COUNT16.STATUS.bit.SYNCBUSY);

    // Start counter
    TC5->COUNT16.CTRLA.reg |= TC_CTRLA_ENABLE;  // Enable TC5
    while (TC5->COUNT16.STATUS.bit.SYNCBUSY);
}

void loop()
{
}

This works great. My logic analyzer shows me perfect 1μs pulses.

However, trying to add a small conditional statement in there to output "0" bit sequences according to the GameCube protocol causes the signal to instead adopt a frequency of closer to 2μs.

void TC5_Handler(void)
{
    // Toggle pin
    (next_bit ?
        PORT->Group[PORTA].OUTSET.reg :
        PORT->Group[PORTA].OUTCLR.reg) = (1 << PIN);
    next_bit = (n & 3) < 3 ? 0 : 1;
    ++n;

    // Reset timer interrupt flag
    TC5->COUNT16.INTFLAG.bit.MC0 = 1;
}

I didn't expect that little added code to suddenly make the function take that much longer than a microsecond. In that case, how can I make this task more efficient? Must I pursue a different route with generating these signals?


texts:
Building a robot that will run on 12V.
Using four DC motors and basing my design around an older robot that has been around my school for many years.  It uses the LM 298 H-bridge for motor control.

I like the simplicity of the LM 298 but was wondering if there might be a better device I should be looking at or if it's still a good choice.

What are the attributes I should be looking at for best performance?


texts:
I was browsing and found some very informative answers on this site. They didn't specifically answer my question, so I decided to Register and ask ...

We are importing digital cameras from Europe. These cameras have a CE certification (i.e., they have been tested and found to comply with the CE requirements (test protocols available). For use in the US they need of course FCC compliance, which is a voluntary test for unintentional emitters.

1) To my knowledge, the CE requirements are more expansive than the FCC requirements, and also more stringent. Does CE compliance then automatically imply FCC compliance? CE also Comes in different classes (A-E, I think). Does a specific class then perhaps imply FCC compliance?

2) Some of the tests are made with specific configurations (shielded cables, etc). Is this then part of the configuration, i.e., do the products have to be sold with the parts used for the tests (for example with the shielded cable), or can the products be sold without the parts , perhaps with a note that in order to reach FCC compliance certain parts are necessary?

Thanks.


texts: What is the least complex way to implement a DP3T ON-X-ON switch?

texts:
I have an application below that requires 2 MCUs to be on a PCB, along with a single FTDI header. Both are programmed thru their RX/TX UART pins.

In normal operation, the RX pin on MCU_1 is connected to TX pin on MCU_2, and vice versa, for inter-MCU communication.

To flash MCU_1, a DP3T switch is toggled to the left to route the MCU_1 TX/RX pins to the FTDI header.

To flash MCU_2, the switch is toggled to the right to route the MCU_2 TX/RX pins to the FTDI header.

simulate this circuit – Schematic created using CircuitLab

So far, I have found DP3T switches with the following configurations:

I'm looking for such a configuration instead:

I'm guessing such a switch probably doesn't exist? How is it best then, using the least wiring/components as possible, to implement such a setup?


texts: 2 loads not working together on the same battery

texts: One 12v car battery powers 2 loads. One load is 3.5A and the other is 100mA. The 100mA load is always on. When the 3.5A load gets switched on, scope readings show the amp draw momentarily dropping to half or less and voltage dropping from 12v to about 9.5v on the 100mA load. How can I maintain steady, smooth voltage and current to the low amp load during the brief time that the much larger load is being energized? Would I need to use a large inductor or large cap to help momentarily sustain the 100mA current and voltage during this time? I think I need an "isolator". If so, can it be explained in more detail?


texts: Determining whether signal meets the 12 dB SINAD voltage

texts: The specification for the sensitivity of a certain radio receiver says: Typically 12dB SINAD NBFM for 0.15uV at 145MHz. If I understand correctly, this means that the received radio wave should have a voltage level of at least 0.15uV for the receiver to produce a signal with a quality of 12dB SINAD. I know how to calculate the signal power with the link equation, I can also calculate the electric field intensity of the EM wave, but I don't see how I can calculate the voltage level of a signal. How do I verify that my transmitted radio wave will meet this voltage requirement?


texts: How to configure a relay to operate as a transistor?

texts:
We have a FINDER 40.51.9.012.0000 relay, with this scheme:

I want it to operate as a transistor, in the sense that a signal can control the connection of two other lines (i.e., the collector connects to the emitter only when there is 12V on the base).

According to the relay pinout, the collector should be clearly the pin labelled 11, and the emitter to 14 (given 11 connects to 12 by default, i.e. base=0V). Now, where should the base connect? And the power supply? Actually, the collector is the power supply itself, is there any problem if the line connects two pins?


texts:
I posted previously that the hot water button (PA in red) no longer causes the hot water solenoid (Eac in red) to dispense water. It now causes the left coffee group solenoid (G1 in green) to dispense water which should normally only be the case when its buttons (Z1 in green) are pushed.

Today I discovered a couple of water drops dripping on the board (brown square on schematic, between 3rd resistor and 3rd cap on picture). Is there any way water damage to this area could explain the mentioned behaviour? If so, how would you recommend checking the board for the specific issue and what can be a likely solution?


texts: What properties of MOSFET amplifiers made it so popular?

texts:
It seems to me that any circuit where the output voltage varies faster than the input voltage can be used to create an amplifier (for example a diode). We can bias the input voltage and use small signals to deal with nonlinearity to exploit this circuit for amplification.

Why then, was the MOSFET special as an amplifier? Was it cheapest to build, simplest, etc.?


texts: What determines the required bandwidth of current sensors in an electric motor drive?

texts:
Most motor drive control systems incorporate current feedback of some description.

What determines the required frequency response or bandwidth of the current transducer?

Is there any other consideration other than ensuring the sensor bandwidth is greater than the sampling/switching frequency?


texts:
Does it make sense to apply high pass filter over gyroscope data coming from an IMU?
I am using MEMSENSE nano IMU and I am getting rotation angle rates from it.
Earlier as I tried to directly integrate the data to get the rotation angles I did not get anything making sense. I am doing a random motion experiment to find out if the device is working or not. I start moving the IMU from rest and after rotating it randomly I bring it back to rest. Without this high pass filtering, my output looked like this:

After that I don't know why I applied that but it is giving me perfect results.

By High Pass Filter I mean:

During the sample collection from gyroscope of IMU, calculate the average value of the rotation rate
subtract this mean from all the samples

Following are my results:


texts: Problem simulating transistor on Proteus

texts: I'm using PNP transistor to be a switch for CC pin of 7Segment (Common Anode) led and trying simulating it on Proteus at first. Something weird happens is that no matter high or low level at B gate, the voltage at E keeps being high level and just reciprocally changed between about 2V5 and 5V. Therefore, all 7SEGs are always enabled at the same time, and not able to display accurately. I added a pull-down resistor for each Collector and saw it working properly. I wonder why almost of the example on the Internet design the same one without using pull-down resistor but it still works. Does the problem result from Proteus and it's unnecessary to use these resistors in reality? Hope someone used to have this problem could help me figure it out. I've updated my circuit below:


texts: Designing electronics systems with weight constraints

texts:
How would you go about designing a PCB with weight constraints? Suppose, the PCB has a weight constraint that say it must weight less than 140grams.

In searching for parts and components, I realized most if not all components' datasheets do not have any weight information. For example, I need to use two DB25 connectors among a few other connectors on board. None of them carry weight info in their datasheets. Similarly, ICs, discretes etc do not have weight information.

Do I just need to sample components and actually weigh them?


texts: How can I instruct my compiler to use 8 bit bytes instead of 16 bit integers?

texts:
I have the following code in my microcontroler program:

int analogValue = ADCH;        // ADC Data Register

//
// Simple analog comparator.
// If analogValue lower than threshold then toggle output high,
// Otherwise toggle it low.
//
if ( analogValue > 128 ) {
    PORTB = 0;                 // Port B Data Register
} else {
    PORTB = _BS( outputPin );  // Port B Data Register
}

Where:

ADCH is the register that contains the value from the ADC
PORTB is a dital output port that toggles an LED

Looking at the resulting assembly code, I noticed that it is doing a 16 bit compare (lines 40-44) where strictly speaking only 8 bits would have been sufficient:

40:   90 e0           ldi     r25, 0x00       ; 0
42:   81 38           cpi     r24, 0x81       ; 129
44:   91 05           cpc     r25, r1
46:   14 f0           brlt    .+4             ; 0x4c <__SREG__+0xd>
48:   18 ba           out     0x18, r1        ; PORTB
4a:   f5 cf           rjmp    .-22            ; 0x36 <__CCP__+0x2>
4c:   28 bb           out     0x18, r18       ; PORTB
4e:   f3 cf           rjmp    .-26            ; 0x36 <__CCP__+0x2>

I realize I declared analogValue as int, which indeed is 16 bit on AVR, but ...

How can I instruct the compiler to use 8 bit comparison? The Arduino IDE allows me to use byte, but avr-gcc by default doesn't.

Check this page for the complete program and its disassembled resulting code.

EDIT1:

Changing int to char changes the assembly code to:

14:   11 24           eor     r1, r1          ; r1 = 0
3e:   18 ba           out     0x18, r1        ; PORTB

Basically skipping the test entirely.

EDIT2: (Thnx: Wouter van Ooijen)

Changing int to unsigned char changes the assembly code to:

3c:   85 b1           in      r24, 0x05       ; ADCH
3e:   ...
40:   87 fd           sbrc    r24, 7          ; compare < 128 (well optimized)
42:   02 c0           rjmp    .+4             ; 0x48 <__SREG__+0x9>
44:   18 ba           out     0x18, r1        ; 24
46:   f7 cf           rjmp    .-18            ; 0x36 <__CCP__+0x2>
48:   98 bb           out     0x18, r25       ; 24
4a:   f5 cf           rjmp    .-22            ; 0x36 <__CCP__+0x2>


texts:
Is it a valid and synthesizeable VHDL code?

case IR(10 downto 7) is -- RD
    when "0000" => R0 <= RTA;
    when "0001" => R1 <= RTA;
    when "0010" => R2 <= RTA;
    when "0011" => R3 <= RTA;
    when "0100" => R4 <= RTA;
    when "0101" => R5 <= RTA;
    when "0110" => R6 <= RTA;
    when "0111" => R7 <= RTA;
    when "1000" => R8 <= RTA;
    when "1001" => R9 <= RTA;
    when "1010" => R10 <= RTA;
    when "1011" => R11 <= RTA;
    when "1100" => R12 <= RTA;
    when "1101" => R13 <= RTA;
    when "1110" => R14 <= RTA;
    when "1111" => R15 <= RTA;
    when others => null ;
end case;

As you see in each case the output signal is different: R0, R1, R2, etc. I thought maybe I have to put all the outputs in each case; Something like this:

case IR(10 downto 7) is -- RD
    when "0000" =>
       R0 <= RTA;
       R1 <= 0;  -- The problem here is that I don't want R1 to be 0
                 --   but to retain its previous value
       R2 <= 0;
       R3 <= 0;
       R4 <= 0;
       R5 <= 0;
       R6 <= 0;
       R7 <= 0;
       R8 <= 0;
       R9 <= 0;
       R10 <= 0;
       R11 <= 0;
       R12 <= 0;
       R13 <= 0;
       R14 <= 0;
       R15 <= 0;
    when "0001" =>
       R0 <= 0;
       R1 <= RTA;
       R2 <= 0;
       R3 <= 0;
       R4 <= 0;
       R5 <= 0;
       R6 <= 0;
       R7 <= 0;
       R8 <= 0;
       R9 <= 0;
       R10 <= 0;
       R11 <= 0;
       R12 <= 0;
       R13 <= 0;
       R14 <= 0;
       R15 <= 0;
    .
    .
    .
    when others => null ;
end case;

If I don't have all the outputs (R0 to R15) into each case the VHDL compiler gives me a warning: "Found 1-bit latch for signal . Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems."

I need to get rid of this warning.


texts: How can I calculate/estimate the resistance of the thin film structured like in the picture (top view)?

texts:
let's say the thin film is made of metal with resistivity rho and thickness t.

I need to calculate the sheet resistance between point A and B.

any reference suggestion is really appreciated.


texts: Append calculated CRC to data and recalculate does not yield zero

texts:
I have been working on understanding CRC calculations for implementation in VHDL. Specifically I have implemented the CRC-32C (polynomial = 0x1EDC6F41) a couple of ways. First using an LFSR approach and secondly using a lookup table for speed. Everything seems to agree with the online checkers but I am having trouble understanding why, if you calculate a CRC of some data, append the CRC to the end of the data and then recalculate the CRC, I do not get a result of zero.

For example, if I calculate the CRC of the string "123456789" (hex values 313233343536373839) I get a result from the calculator of E3 06 92 83.

Now if I calculate the CRC of 313233343536373839 E3069283 the resulting calculated CRC is BA F5 57 BE; I was expecting this to be zero.

If I repeat the same procedure above with any other of the 8 & 16 bit CRCs available on the calculator I do get zero returned.

FYI, I have been using this calculator for reference.

Also, for anyone else struggling on this topic here are some useful links:

https://github.com/Michaelangel007/crc32
http://www.wolfgang-ehrhardt.de/crc_v3.html


texts: Phase margin analysis of a [diy] PMOS LDO [with LTspice]

texts:
I'm somewhat familiar with using LTspice to do phase margin analysis for a classic i.e. obvious negative feedback path opamp circuit; in fact I've done that analysis successfully for fixing real opamp circuits. But I'm confused how to do this properly for the kind of circuit that is the core of a PMOS LDO. The circuit is actually based on another EE.SE question, which I could answer/fix with some cookbook knowledge of what works for such circuits. But I'm now trying to understand better how the fix worked. (Also, in this circuit there's no voltage divider for the reference voltage, so it's just a follower, which is unlike an actual LDO.)

In this type of circuit the positive feedback pin of the opamp receives the obvious feedback, but this is already out of phase, so it's negative positive feedback, LOL. It seems to me that since I can't meaningfully cut the feedback loop where I normally do it, i.e. at the negative input pin of the opamp, I should do it at the positive one. So I've done that and added a 0V DC but 1V AC stimulus as per the usual procedure. But the result I get doesn't seem to indicate any instability at all...

... which is quite in contrast with the transient simulation (and the real [uncompensated] circuit behavior from the other question).

A few extra notes: I've tried zeroing V2 but makes little difference and if possible I'd prefer to keep the DC point as close the real circuit as possible. Also the fix/compensation cap and its ESR resistor are purposefully disconnected above [so I can see the unstable circuit's bad phase margin], although if I connect them I can't see any amazing difference but the phase does stay higher for longer.

So what am I doing wrong in terms of phase margin analysis here?

A few more notes:

I've tried decreasing the AC stimulus to 0.1V or 0.01V but that makes no difference.
Source uploaded to http://pastebin.com/w3HBiBPw. The LM358 model is the one from TI.


texts:
I'm trying to build a bracelet (fastened such that it does not rotate with respect to the wrist) with small vibrating motors at regular intervals. The goal is to pulse these motors to indicate the direction of magnetic north relative to the bracelet, with the motor closest to magnetic north being pulsed. This is inspired by similar projects using belts or anklets instead of bracelets. In my previous attempts, I have had difficulty telling which motor was vibrating, because activating any motor caused the entire bracelet to vibrate.

Are there any existing projects or products with directional haptic input via bracelet? If not, can you recommend any techniques for isolating vibrations between segments?

(I'm using an arduino, a HMC5883L 3 axis magnetometer, and small eccentric rotating mass motors, but I'm open to suggestion)


texts:
I have a delta to delta 2000 kVA transformer that on power up with no load except whatever is in the main switch gear I am getting 400 volts to ground on one phase 280 on another and 95 on another, the nominal voltage is 480 phase to phase and it is a 3 wire system. The one ground fault light is out until the main gets turned on then it gets better but not completely bright.

Can anyone explain this?

I have had the buss duct and the transformer meggered and they are all good.


texts:
I understand the wave solder process for pin soldering, I have seen videos and read literature while pot solder is used for tinning purposes.

My question is about why we requires the solder to flow.

1- wetting process:
Q: why the wetting requires the solder flow in the Nozzle
q:  why the nozzle full of solder but not flowing would not wet, based on wave flow needed?

Q:  how could we use small pot to solder edge pins connector to pre-built board
without hand solder and without damage if I can get the hot solder in the nozzle in a small pot, but not flowing, but remains at the temperature during the soldering period?

or is that not possible without the flowing process in the nozzle?


texts: Quartus Prime Lite: Error (209053): Unexpected error in JTAG server -- error code 35 and Error 202940 Can't access JTAG chain with SSH

texts:
Today I received a Terasic USB Blaster and I want to program an Altera 10M04SCE144C8G FPGA. I am using the Intel Quartus Prime 20.1.1 Lite Edition installed in Ubuntu 20.04. This FPGA has already been programed before using another Terasic USB Blaster, now I have a new one and my installation of Quartus is also new. When I hit the "Start" button in the "Programmer" window the blue LED in the Terasic USB Blaster turns on for some seconds and then I get this
Error (209053): Unexpected error in JTAG server -- error code 35

as seen below:

Any idea?
Edit
After a while googling I found this link and in FAQ #6 they describe exactly my error. As suggested there I removed the .pof file and selected the .sof file instead. In this case I get the error
202940 Can't access JTAG chain

as shown below:

I still could not program my FPGA.
Edit 2
I discovered that this problem arises when I try to program the FPGA connecting remotely with SSH to the computer to which the USB blaster is connected. If I go to the computer "physically" and hit "program" there, it works out of the box.


texts: Output voltage on pin 14 (A5) address input pin of SP0256

texts:
I'm playing with an SP0256 speech synthesizer.  Ive bread boarded and am checking all my connections (as it doesn't work) and have found a very strange thing.  Pin 14 of the IC being driven to ground.  Pin 14 is defined as address bit A5 of input addressing.  All the other address pins are of high impedance but A5 is most definitely low.  I have checked, checked and re-checked my circuit.  I'm posting here in the hopes that someone else may have played with an SP0256 and might have seen something similar.

Later ... it was pointed out that I hadn't previously provided enough information and I appreciate those who showed me my error.  From the SP0256 datasheet, this is the diagram I am following:

Notice A5 (Pin 14).  Notice that it is an address input line.

Here is a picture of my breadboard.

Pin 14 is the bottom right of the 28 pin IC on the right.  It is connected via the "green" wire to a GPIO on my Raspberry PI.  The thing is ... when I pull the wire from the breadboard, the signal on Pin 14 is low (ground) while all the other address pins A1-A4 and A6 are high impedance.  Something smells awfully fishy as an input line (with zero other connections) should never have an output signal. (I think).

Later ... in the discussion, it was suggested that my IC might be counterfeit.  Here is a detailed picture of the IC received:


texts:
I am learning digital modulation basics and I have question about frequency shift keying — how the constellation diagram of M-ary FSK looks like? I can somehow figure how binary FSK diagram looks (it is similar to PSK), but I cannot imagine M-ary FSK diagram.

EDIT: And ome more question. Do you know any nice applet/online-tool where I can play with different modulations and their parameters?


texts:
The wikipedia article on Step up converters says

  A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage.

However if I look at any given step up converter it will mention that the input and output is AC. Why this discrepancy? I hope and guess it's just a terminology thing, but the concept of an AC step-up converter is something I have a lot of trouble understanding, so I would like to have my terminology right.


texts:
I am testing small DC Motors for toy cars. In determining the watt rating, I was informed of a formula used for them. I simply cannot find any reason for the introduction of 100 000 in the equation.

$$P = \dfrac{\dfrac{RPM_{max}}{2} \cdot \dfrac{Torque_{max}}{2}}{100000}~~[W]$$

The motors are simple FC 130/FK 180 types. Designed for 12VDC power.

Here is an example of a test someone has done:

FC130 - rated 21,500 RPM/12V, and 170 gcm torque

$$P = \dfrac{\dfrac{21500~RPM}{2} \cdot \dfrac{170~gcm}{2}}{100000} =\\
= \dfrac{10750~RPM \cdot 85~gcm}{100000} =\\ = \dfrac {913750}{100000} = 9.1~W
$$
or:
$$P = \dfrac{9.1~W}{746} = 0.012~HP$$

These motors normally draw only 0.15 Amps. I cannot see them pulling 9 watts.

Anyone know where the formula comes from and why the added 100000 is used?


texts: Is an instrumentation amplifier design same with a standard op amp?

texts:
Is instrumentation amplifier nothing but a standard op-amp with a different configuration? I wonder if the inner complicated circuit of an instrumentation amplifier same with standard op-amp's.
At one forum I read: "An instrumentation amplifier is nothing more than a standard op-Amp configured in a differential mode with isolation buffering
to the inverting input and non-inverting input." Is that true? I mean is the only difference configuration or inner circuitry? Does that mean any op-amp can be used as an instrumentation amplifier.

But here at page 9 of pdf document it says: "In contrast, if a standard op amp amplifier circuit were used in this application, it would simply amplify both the signal voltage and any dc, noise, or other common-mode voltages. As a result, the signal would remain buried under the dc offset and noise" : here is the link: http://www.analog.com/static/imported-files/design_handbooks/5812756674312778737Complete_In_Amp.pdf

Im asking about the IC part of the amplifier if it is manufactured the same way.


texts:
I've been working with a buck converter since a few weeks, I've tested it with load and it works just fine, but today I've measured the output with no load and saw some unexpected behavior.

simulate this circuit – Schematic created using CircuitLab

I'm using an arduino and an IR2110 to drive the transistor, initially the power source V1 is turned off, and the duty cycle of the control signal is 0, with I turn on V1 the output voltage start to increase until it reach about 14V, but the circuit is practically no draining any current from the source, just 30mA for all the circuit which includes an optocoupler, to linear voltage regulators and the IR2110. When I connect the load about 5ohm the output voltage immediately drop to 0V, the power supply V1, the circuit is still consuming the same 30mA. How can I explain the output voltage with no load?


texts: How come optical data modulation is faster than that of electrical modulation while optical modulation is done by electricity?

texts: why optical data is of high bandwidth that that of electrical copper data bandwidth when we use electrical signal to achieve optical data modulation ?


texts:
I'm using an LM2734 buck regulator to get +3.3V at 400mA. The datasheet is unclear on how to lay out the supply, so I tried to follow some common sense, keeping all power traces short where possible. The power supply has to be very small, which is why it uses ceramic caps and the LM2734, which operates at 3 MHz and thus requires a smaller inductor (it's still pretty massive!)

L1: 3.3uH 2A inductor
C1: 4.7uF 50V ceramic cap
C2: 4.7uF 50V ceramic cap
C3: 0.01uF 16V ceramic cap
C4: 22uF 10V ceramic cap
D1: RB160M (input protection)
D2: RB160M
D3: (mislabeled D1, the SOT-23) any small signal silicon diode
R1: 10k
R2: 31.6k
R3: 1k
LED1: any small LED
U1: LM2734, SOT-23-6

I'm generating the boost voltage from the output.


texts: Is there a simple way of measuring the self-capacitance of a coil? There are many estimates out there for self-capacitance based on number of turns and wire specs, but I'm wondering if I can do an experiment to measure it reasonably accurately.


texts: How to use audio signal from car speaker as transistor switching signal?

texts:
I want to make reactive LED strip for my car and I want to make it somehow smart... I figured a schematic like the one below:

The LED has a 12 V source at the beginning of course. KEY3 is a relay but the case we are considering here doesn't matter, because it's closed
I connected the circuit as shown below but it doesn't work as expected. The LEDs are lit when the radio is on but the volume is zero. I checked the voltage on the speaker wire and it shows about 6 V when the radio is on, and near to 0 V when the radio is off. But I measured it with DC voltmeter.
I know speakers work on audio signal between two terminals, which is basically an AC signal, but I thought connecting the base to one speaker wire would create pulses of voltage between the base and the emitter. Instead, the LEDs are on all the time. When I turn up the volume they seem to start pulsating but they are never really off.
The ground shown on the schematic is the cars mass ground, so it isn't connected to the speaker in any way.
Unfortunately, I don't have an oscilloscope to look at the speaker wire signal.
Is there any way I can connect it so that the LEDs flash to the music?


texts:
How I can make this sine to square wave converter accept higher frequency?

Because when I tested it, it only accepts 10KHZ max. I will need to input a higher level of frequency till 1000KHZ.

Would this mean that I need to swap the resistor values to lower values?

New to digital electronics. Would appreciate if someone could help. U1 is an Op Amp.


texts:
I need to make amplifier that its output is Vo = -Vi +Voff  where vi is my input signal while Voff is offset signal come from power supply of amplifier 15v  , Voff  vary from -5v  to +5 V  by variable resistor 100k

It tried with this design i get Ri = Rf
but i have problem when get value of Rx every time i get negative value


texts: I want to use a Voltage divider and i need to divide 5v to ~3.3 so I ordered 10K resistors on eBay, but the voltage divider needs a 20K and a 10K, can i use 2 10K's parralel as a 20K


texts:
I've been trying to build a high capacity UPS with a deep cycle marine battery, 300 W inverter and a Double Pole Double Throw relay. The relay switches the power source from mains to the inverter during a power failure.

The system worked fine for a couple weeks--and then the inverter stopped working. So I tried out a replacement one, but when the UPS was unplugged from mains there was a large spark accompanied by a puff of magic smoke--and that inverter is now toast as well.

I tested out the DPDT relay, and its working normally, as is every other part of the circuit except the inverter. I was thinking that there might be an issue with the mains and inverter ground being connected, or that somehow 120V from the mains is being connected to the inverter output. I can't understand why this would happen though, especially since it was working fine for weeks already.

The other possibility is that the inverters were overloaded. The load is a fish tank pump with a 1200 GPH rating and supposed 150 W max draw. In the weeks that the UPS was working, this was not the test load. I was using a similar load of likely more than 150 W, running two server computer for about 5 hours at a time. Also, both inverters are supposed to have over-current draw protection, so this shouldn't be a problem anyways--wouldn't the inverter just shut off?

Any help or suggestions would be greatly appreciated. Please note that I am pretty new to all this :)

A rough schematic is below. The DPDT relay is drawn in the state it would be when the coil is unpowered.

UPS Schematic


texts:
I recently deployed a custom RFID-based accessed control system.
Before deployment, we (me and my team) did rigorous testing of the system (Linux machine) as well as individual modules (python client, node backend), we found multiple issues during testing which resolved.
RFID Readers are connected to the system. Randomly these scanners didn't get power and hence card isn't read by the system.
The only factor that is different in a production environment when compared to the testing environment is dust. Does someone have any experience with something similar?
Edit:
Dust is my assumption. Please bear with this is my first posting a problem. Thanks in advance.


texts: Are CIN/COUT in series or parallel in this TranSim EE-Sim output?

texts:
I'm needing to use this MAX20034 voltage regulator. Because I know very little about voltage regulators (in how they are structured), I went to MAXIM-Integrated's website and was able to find a simulator using TranSim EE-Sim. It is exactly what I'm looking for, I just need help figuring out this last part.If you notice on the far right side where Cout1 / CIN / Cou2 (from top to bottom) are, you notice at the bottom, below the resistance is either a 2x or 3x. I have no idea if this is saying place 2/3 capacitors in series or in parallel. The only thing that I do know is that in the bill of materials, it does have the multiples of capacitors, so I'm not just going insane here. Any ideas?

Here are some specs for reference if it helps at all. I didn't make most of them, but it's in the report outputted from EE-Sim:

nominal input voltage: 9V
input voltage ripple: 0.5%
output config: fixed output voltage
output 1 voltage: 5V
output 2 voltage: 3.3V
output 1 current: 5A
output 2 current: 2A
output 1 voltage ripple: 0.1%
output 2 voltage ripple: 0.1%
load 1 step current: 2.5A
load 2 step current: 1A
load 1 start current: 5A
load 2 start current: 2A
load 1 step edge rate: 1A/us
load 2 step edge rate: 1A/us
output 1 voltage load step over/undershoot: 5%
output 2 voltage load step over/undershoot: 5%
mode: PWM
switching frequency: 600KHz
inductor 1 current ratio (LIR1): 0.3
inductor 2 current ratio (LIR2): 0.3

I sent a case to MAXIM-Integrated to see what they say, but if anyone knows so I can update sooner, I would greatly appreciate it!


texts:
I am trying to minimze the output voltage ripple of a 4-layer pcb power supply and am curious as to what approach would be better.  So I have 6 low voltage high amp buck converters feeding 6 chips.  The buck converters will all have the same frequency, characteristics and output voltage.  The chips are all the same as well.  My original idea was to have have a power plane, with 6 splits, each one unique to each chip, like below;

              (top view)
              buck Vout----------> cpu
              break
              buck Vout----------> cpu
              break
              .....

They would all share the same ground plane.  Now I'm wondering if I should keep the voltage plane unbroken?  This should make sure the cpus are running at the same voltage, but would the control circuitry of the bucks interfere with each other?


texts:
I'm experimenting with native USB in STM32. I've not found any "step by step", or a little more well structured tutorial, how to implement CDC or mass storage for example. I've found some examples, but would be better some explanation too.

Could you recommend me some nice descriptions about these stuffs?


texts: Building a Circuit that takes constant mA

texts:
I want to discharge a battery at a constant C rate (0.2C) the battery is 3.7V and 380mAh. I did some calculations and found out that the current the circuit will need to take is 76mA. I am planning to build this with LED's. I am not sure but from what i know LED's take a constant current, i am not sure if this is 20ma or 15ma or something else. Also I am not sure if I should connect them in series or in parallel. Can someone help me come up with a circuit I could make that takes up a constant current of 76mA.
Any suggestions of LED's i could buy off amazon do to this would also be helpfull


texts: What is the phase of the impedance at each point on a resonant center fed half wave dipole?

texts:
Everyone knows that for an ideal center fed half wave dipole operated at resonance, the impedance at the center is 73 + j0 ohms.
The impedance at any point on the antenna is determined by the ratio of the amplitude of standing wave of voltage to the amplitude of the standing wave of current at each point.
The graph below is very common and shows how the impedance Z at any point on the antenna is E / I at each point. Notice how Z is between 73 ohms and 2500 ohms with no mention of the value of reactance in the impedance, even though AC impedance has a real part and an imaginary part.
The graph is very simple and easy to understand even for beginners. Especially the part about how the impedance in the center is (E / I) = (0 / I) = 73 + j0 ohms.
What's the value of the reactance in the impedance at all the other points on the antenna ?
The answer that i'm not looking for is that the reactance is zero everywhere on the antenna because it's resonant, but if this is true someone please explain why before i die of brain damage :(


texts: I'm looking to find the Thevenin equivalent of two parallel voltage sources where each source has some internal resistance as well for simulation in Matlab. I don't know where and how exactly to put a voltage meter and current meter in place to measure the open source voltage and short circuit current. Can anyone guide me?


texts: Troubleshooting 16x4 LCD Display Showing No Output

texts: I have a 16x4 LCD (model DCM16433) that I suspect is dead. It has 14 pins rather than 16, but this should just mean no backlight. I have hooked pin 1 to Vss, pin 2 to +5 V, and pin 3 to a 10k pot, but I can't get anything to display at any contrast setting (IIRC, it should display the black character "outlines" even without any data). I know the pot works, and I know the LCD is getting power (that is, the voltage across pins 1 and 2 is +5 V). Am I missing something, or is the LCD just dead?


texts: Do working electrical engineers in circuit design ever use textbook formulas for rise time, peak time, settling time, etc

texts:
This is a very general question. In undergrad electrical engineering, students are usually taught about step response to LC (second order) circuits.

This is usually when many parameters are introduced, some of which are

rise time
peak time
percentage overshoot
settling time

The definition of these could be found in various sources, such as wikipedia:
https://en.wikipedia.org/wiki/Settling_time

and detailed formulas exist for many of these quantities
https://ocw.mit.edu/courses/mechanical-engineering/2-004-dynamics-and-control-ii-spring-2008/lecture-notes/lecture_21.pdf

http://www.personal.psu.edu/faculty/j/x/jxl77/courses/ee380_fa09/ee380_slides3.pdf

I do not have an extensive circuit design background, I am guessing that these parameters can be used as rule of thumb to calculate system transfer function, or location of poles, etc. I have no idea how they can be used in reality.

Can working electrical engineers in circuit design comment on the practical usefulness of these parameters? Or are these parameters found by some algorithm that is used in design process?

Many thanks!


texts: Converting voltage reading from temperature sensor into Celcius

texts:
I'm learning how to read temperature reading from a sensor from this tutorial.

The code (Arduino) to convert from voltage reading into temperature is as follow.

float temperatureC = (voltage - 0.5) * 100 ; // Converting to degrees

I wonder why the formula has to be like this, the numbers and stuffs. Is it different from sensors to sensors? If I buy a temperature sensor, does it come with a specification on how derive temperature from voltage reading?


texts: Increasing ADC resolution by supersampling on a successive approximation ADC

texts:
Is it possible to increase the resolution of an ADC by supersampling on a PIC24F ADC, which has 10 bits of resolution and is implemented using a successive approximation engine? Speed is not critical - greater than 1 kHz or so.

My initial thought was no, as it is not a Delta-Sigma ADC and results are not cumulative, so I thought I could add noise to the voltage reference (3V nominal) using a pin of the MCU and a high valued resistor. Would this work? The additional noise should improve the resolution, but I'm unsure if this applies for all types of ADC's.


texts: Efficient way of setting bits in verilog

texts:
I'm just learning verilog and have a question regarding setting bits in a 2 bit register (assuming I'm even making the register correctly).

Suppose I have a hypothetical module, foo(), which has two inputs, and I want to combine these inputs into a 2 bit register. My thinking is that I would do something like ...

module foo(a,b)
    input a,b;
    reg [1:0] c;

    c[0] = b;
    c[1] = a;

I have two questions:

Am I doing it wrong?
Is there a better way? (e.g. something like c = {a,b};)


texts: What software I can use for CPLD programming?

texts:
I would like to learn more about CPLD circuits (because they are cheaper than FPGA), but I am facing a major problem. I cannot find any simple and userfriendly software for programing and debugging CPLD.

The CPLD I have is XC9500XL from Xilinx. But I hate Xilinx's ISE WebPack. We work with this application in school and it is too complex, huge and not user friendly.

Is there any alternative I can use? Ideally some open-source, which can run under Mac OS.


texts:
In a laser printer's power supply board I have desoldered some of these passives. I think it is a inductor, because it's legs aren't exactly aligned and the round body could be the coil.

Does somebody know what it is and can tell me what the text means.

The label says:

SHM
X1400~
Y1239~
E222M

(The zero looks more like '( )'.)


texts: Simple voltage presence monitoring with negative power supply

texts:
I am switching a 230-240 V load with a TRIAC and relay while also monitoring the presence of voltage on both ends of the load (i.e. not measuring the amplitude -- just that the switch successfully opened/closed).  Previously, I had a positive power supply referenced to L2, and life was peachy.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

(The 'MON' signals drive a small P-FET that switches optoisolator LEDs.)

This is when the TRIAC -- SW1 -- was optically isolated from the drive circuit.  Now, however, I'd like to move to a hot-side microcontroller to control SW1 directly, which means converting to a negative supply in order to (easily) drive the TRIAC in quadrants II and III.

simulate this circuit

This presents a challenge since the 5 V source will now have to sink current if the existing monitoring circuits are used.  This source is a IRM-03-5 that is not rated to sink current like this, and simulations show the monitor circuit behavior breaking down if an inline diode is placed at its output.

Is there a simple circuit that would accomplish this presence monitoring given the negative supply?  Its output isn't too important -- either a pulse train, high, or low -- as long as it is differentiated between the phase being on or off.

Note: I also found an ST app note about driving TRIACs in QII and QIII with a positive supply, but would like to exhaust my options with a negative supply first.


texts: Wrong signature from ATMEGA8-16PU after setting fuses with avrdude

texts:
I am lost in loading bootloader for Arduino Single Sided on ATMEGA8-16PU.
Here is my problem.

I made the Arduino Single Sided V3
Placed ATMEGA8-16PU in the board and attached it to the Parallel Programmer and attached external 9V battery.
Accessed the controller using avrdude using command line and it returned correct signature 0x1e9307.
I executed this command avrdude -p atmega8 -c dapa -P lpt1 -U lock:w:0xff:m it worked well. Everything was fine till this point and controller returning correct signature.
Then this avrdude -p atmega8 -c dapa -P lpt1 -U hfuse:w:0xca:m -U lfuse:w:0xdf:m and suddenly after execution of this command controller was returning wrong signature 0x000012.

What is wrong? I cannot go further? Why it is returning the wrong signature?

But I noticed something odd, controller was not returning 0xffffff it means it is not bricked, its alive and hence returning signature whatever it is.

Maybe the default baud-rate of programmer is not matching anymore with the baud-rate change in controller for different clock source.

What should I do ?


texts: Does the sign matter on the frequency response?

texts:
I've been trying to calculate the frequency response of a series LR circuit with the output measured across the resistor.

I solved it in two ways, one by taking the Fourier Transform of the impulse function of this circuit, and the other method by simply using a voltage divider of the impedances. I've been getting different answers, for some reason. For one answer, I am getting the transfer function to be positive R/(R+jwL) and for the other answer, I am getting the negative of that.

Are they the same or did I do something wrong?


texts: How to find current in this circuit passing through 4ohm resistor

texts:
Below I have added my solution after the question so please let me know how I can solve it after the last step:

These  steps to follow to solve the question from where i left in my post ,

FYI :As the registance values are in killo ohm so current will be in mill amp and power will be milli watt .

Thanks a lot  to @g36, @jasen  and @rabi for your help  . i learned something new today and its really going to help me in solving circuits easily.


texts: Are these pin connectors a standard part? If so, what are they called?

texts:
This is a "wet" temperature sensor for a Boilermate 2000 thermal store. The pin connectors are inserted into a plastic plug that connects to the control board (see 2nd image).

The pins do not stick out from the plug (see 3rd image which shows that the main pins are on the PCB).

Are the pin connectors some sort of standard part? If so, what are they called?


texts: Industry standard for outdoor appliance AC input bulkhead connector

texts:
I am looking to spec an AC input receptacle that is appropriate for outdoor use.  The equipment for which it is required is essentially a relocatable enclosure that is designed to operate unattended for long periods of time.

On first thought IEC 60320 C13/14 style AC input modules seem appealing as adapter cables are readily available for input up to 250V.  Our equipment can accept a range of voltages so this would allow simple in field customization. In our application the bulkhead fitting should be at least IP65/66 in terms of ingress protection to the equipment.  However there seems to be a complete lack of outdoor appropriate power input modules for this requirement. Example search. This leads me to believe there may be another standard that is more widely adopted.

There are obviously many connector systems that will solve this problem (Amphenol/LEMO/Bulgin) though none appear to adhere to a single standard. Captivating a power cord, while easier, does not allow for flexible configuration in terms of input voltages.

My question is what is the general industry standard for outdoor appliances/equipment that will support multiple input voltages?  Does one exist?


texts: How do you run the code without external computer in BeagleBone Black just by powering it?

texts: For example, an autonomous robot. The code should execute once I apply the power supply to BeagleBone Black without having it connected to the computer. I am using angstrom distro.


texts: Sampling: how to determine a "good" sampling rate based on a given filter

texts:
I assume that the sampling rate is w_s = 2w_max if we have an ideal low-pass filter that nulls frequencies whose absolute value is higher than that of w_max. Therefore, that the only reason for oversampling is to compensate for the imperfect filters whose magnitude at the stop-band isn't exactly 0, etc.

Consequently, one should oversample to limit the unwanted effects of the imperfect filters. But how much? What's a "good" sampling rate for a given filter of a given order e.g. the Butterworth of order 7?

Thanks!


texts: Connecting CMOS digital ICs that are powered from different power sources

texts:
Imagine I have 2 CMOS devices with logic gates, etc. Both use the same nominal voltage - 5v but are powered from different sources. If I will use simple regulators like 7805 on both sides, they will give slightly different output. One may give 5.05v, some other 4.97v. The grounds of these devices will be connected. This means that sending logic zero in any direction will not cause a problem, but sending logic one to a device with lower power level may cause a problem. I can put a resistor to limit the current, but would that be adequate?

Is there anything better than this resistor? What would be a good value there? Or maybe this is not a problem at all and I can simply connect the pins directly assuming that the difference of the power levels is small? What would be the difference when the problem will start to appear for our days CMOS logic gates and micro-controllers?


texts: Can someone explain the working of this Surge Suppression Circuit

texts:
This is an old circuit which is still being used.

I am curious to understand that if 600 VAC is applied to AC side of the three phase rectifier which has diodes, and on the DC output side of the Bridge you have Capacitors connected so will these capacitors fight the Voltage rise on the AC input side of the Bridge as well ?? I am asking this because there is a coil connected to the AC side which when activated will remove 10 ohm 225 watt resistor by closing a contact.


texts: Component identification - do you know what are the values of these components?

texts:
I am trying to identify the capacitance and resistance of two components that are soldered on a PCB.

The capacitor below should be 10 nF according to the datasheet. But its code is not 103. What's the value of this capacitor?

The resistor below should be 4k7 Ohms according to the datasheet. Then the band colors should be yellow, violet, red, and tolerance. But the third band is black instead of red. Then it is 47 Ohms instead of 4k7. Am I right?


texts:
I am designing a simple Buffer to get the voltage of a high-impedanze source to an ADC (60k Impedance).
For that I choosed an JFET in the source-follower configuration.

simulate this circuit – Schematic created using CircuitLab
To bias the gate to ground and keep the input-resistance high, there will be an >1Meg Gate-Risistor.
I am a little bit confused about how to select the Source-Risistor, because the Output-Voltage (Voltage at the source) should be nearly independend of the load. So it should not matter, if I am using a 1k or 100k resistor, does it?
Some resources say, with Rs, you bias the JFET.
Could someone please clarify this to me?
A second Question:
To get better linearity, I may use a current Source at the Source (biasing the Gate to Vcc/2 with a single supply-voltage)
What is the approach to choose a current for that?
Thanks for any advice


texts: Doubt regarding inductors and transformers

texts: If inductors block AC then how come transformers work only on AC? Please clear my concept.


texts:
Hopefully this is the right community to ask this question. Does anyone know whether there is a significant chance that ozone at approximately 15 ppm will damage consumer electronics, speakers, keyboards, and lab equipment, such as a Tektronix scope, for example?

I'm very sensitive to smells (actually diagnosed with hyperosmia, if anyone wants to know) and there is a slight but unpleasant odor that builds up in the  apartment when I keep the windows closed for about 10 hours or so. I moved here recently, and except for this and a couple of other minor problems, I really like it. It's cold and rainy outside, so I can't keep the windows open, as I do in the summer.

I decided to blast the place with ozone, which helped for a few days, but now the odor is coming back. The first time I did this I waited until the rain stopped and hauled all of the electronics to the balcony just in case, and left the place, of course. But I'm not going to drag all of this stuff back and forth again, so I wonder how dangerous is this really?

According to a quick guesstimate based on the ozone generator specs ad the volume of air in the apartment, and assuming ozone half-life of about 30 minutes, the concentration should stabilize at about 15 ppm. Would repeated exposure (let's say a couple of hours once a week) pose a significant risk for electronics?


texts:
Given a step change in the input voltage of a standard op-amp based linear regulator, a finite amount of time is needed for the op-amp to sense the voltage difference at its input and do whatever it needs to do to make its differential input voltage nearly zero.

I'd like to know how the feedback loop is able to stabilize the output voltage when the input does not change in a step-wise fashion but is instead constantly changing with time. If the op-amp must respond to changes in the input, and this response takes non-zero time, then wouldn't the op-amp be 'chasing its tail' when the input is varying? In other words, how does the op-amp 'keep up' with the input if the input is the cause and the loop adjustment is the effect? Isn't the output adjustment always one step behind the change in the input? Is there an input frequency or dVin/dt at which the op-amp would not be able to stabilize the output frequency?


texts: I'm trying to make a robotic drone from the body of an old quad copter, and I was wondering what these pins are


texts: Limiting input frequency to a specified value

texts:
I would like to limit the output frequency of a variable reluctance differential signal to a specified value, in this case 7,000 Hz. It is a constant peak-to-peak of 24.0 V, which remains unchanged throughout the frequency range. This signal comes from a crankshaft position sensor on an engine, and has a "missing tooth" behavior where regardless of frequency, after 34 cycles there is a missing period in the signal.

I am unsure if the missing tooth behavior is necessary for this application, however I would like to know if it is possible.

The output frequency needs to match that of the input until 7,000 Hz, above which it remains at a constant 7,000 Hz and the input is allowed to rise above 7k.

The signal cannot attenuate and the frequency cannot rise above the cutoff point.

Thanks!

Devon


texts:
I'm having a surprisingly hard time figuring out which seven segment display I have on a board I'm looking at.

It is common anode, as there is one pin tied directly to Vcc.

It's like this, except rotated 90 degrees (the pins are vertical, along the sides):

Assuming pin 1 is in the top-left (at the f-a intersection), I know that the CA is at 3,8. But other than that I don't know which pin is which.


texts: how to implement a low pin count stereo display (FPGA)

texts:
I need to design a TX/RX pair which functions like a HDMI 1.4 3D, for a proprietary HUD. The source signals are 2 distinct TFT output in RGB， and the sinks are also two separate OLEDs, and a stereo audio also need to be transferred in the same cable, but is on a lower priority.

The purpose is to reduce pin count of the cable connector.

LVDS signals on Xilinx spartan 6 could be transferred in meaning as GTP(PCIe) or SelectIO(TM) through IOB. The bandwidth estimation is about 600Mb/s in XVGA(single line).

Should i build a SerDes to bundle DVI(HDMI)signal in PCIe, or build something from scratch.

Thanks for your reading and your comment is valuable.


texts:
Before I start, YES this is for homework so I dont expect a full answer.

Just a pointer to the right method would be helpful.

I have a parallel resonant circuit. My known value is the value of the Capacitor. The unknowns are Q, L, and Fo.

The aim is to calculate BW.

Maybe Ive lost me mind, but I do not know how to do this without at least the resonant frequency, or Q. (If i had either it wouldnt be an issue to work out)

Does anyone have any practical advice on how to approach this problem please?

EDIT: I have both source and load resistances, so I can calculate equivalent R, but I am lost in how to calculate Q, L, or F.

BTW thanks. the 1st reply makes total sense to me. ill go and have another look.


texts: RC circuit with current and voltage source

texts:
I am once again stuck on a task. The circuit initially looks like this:

And the question is:

So my attempt:

The first thing that came up in my mind was that the switch had been closed for a long time. That made me think that initially the capacitor behaves like an open circuit. So I redrawed the circuit like this:

Where Vc = Vab

So I thought that I could find Req and find Vab through the voltage divider.
However there are two things that makes it difficult form the to continue:

The question states that when t = 1 μs then the switch opens, but the plot of Vc(t) should be from 0
I don't know how I should consider the current source. Most problems that I solved have either had a current source or a voltage source. How should I look on the circuit when I have a current and voltage source?

Thanks in advance!

Edit:

Here is my new circuit after some help, however on the final state I am uncertain if the switch should be open and the capacitor not acting like an open circuit? :


texts:
I've been using the Arduino starter kit recently, and for a project I require a 10 thousand ohm resistor. The kit comes with a belt of different resistors, and It has some 10k resistors but I've been having some trouble reading the color code on the resistors, I know the color values and the rules for 4 and 5 band resistors.

The main issue is that I don't always know which direction to read the resistors, I know its left to right but I don't know the indicators of the left and right sides. My friend said it doesn't matter but I know this isn't true in this example of a 5 band 220 ohm resistor

The correct way: "red, red, black, black, brown"
The incorrect way: "brown, black, black, red, red"

I do suspect one 5 band resistor, because it reads "brown, black, black, red, brown", I know the last band is wrong but I feel like that could be the way gold shows up on a blue resistor.


texts: Variable Capacitor - capacitance vs. rotation angle

texts:
I have an Elenco AM / FM radio kit.  For the AM section I am trying to figure out the relationship between the frequency shown on the calibrated dial and the angular position of the dial.
For a capacitor, the capacitance is defined as C = epsilon * A / d, epsilon is the permittivity of the dielectric material between the plates, A is the plate area, and d is the plate separation.
The capacitance seems to be a straightforward linear function of rotation angle.  For a variable capacitor like this,

which is representative only, with maximum capacitance being when the rotating blades are all interleaved with the stator blades, I defined the capacitance as C = -k1 * theta + k2, theta being 0 at the maximum capacitance value.
The kit does not specify the inductor value of the ferrite-core antenna and coil, but I estimated it to be about 0.2 mH.
The resonant frequency for an LC circuit is f = 1 / (2 * pi * sqrt(L * C)).
I plotted two lines.

The "Plotted dial data" curve resulted from reading 6 frequencies from the dial and the angles for which they would tune.  The "Theoretical Equation data" is the plot of the frequency equation with the linear C equation substituted into it with k1 and k2 being determined so that the curves meet at 540 kHz and 1600 kHz, the lower and upper ends of the AM band.  The respective theta is 10 and 170 degrees.
You can see that the two have a superficially similar shape, but I cannot determine why the theoretical curve is not more like the plotted dial curve.
I am missing something.
Thanks for any help.


texts: Is this safe? Wiring for power relay jqc-3fc(t73)dc5v

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I have an ac relay jqc-3fc(t73)dc5v that I am trying to use with a atmega and drive with 5v. Is the wiring as shown in the picture a good idea? Considering that ac and DC need to be very close together on the pins? The brass thing will be carrying 220 v ac. The jumpers carry DC. The relay will drive the pump as shown in the picture. The wooden box will be used to contain the relay and ac lines.
.


texts: Choosing a suitable FET for a design project

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I'm currently working on a project to produce a  high speed and high voltage pulse. I'm trying to find a suitable FET.
I intended to supply a voltage of about 50v to circuit. And using the FET to go on and off behaving somewhat like a switch, thus somewhat creating a fast pulse.

However the requirement to produce I require a FET, that will allow to have a switching time in the region of 1ns and also needs a voltage threshold about 50v.

MOSFETs are suitable for this case as I remember reading the voltage threshold and switching times  directly related. A fast switching MOSFET has low voltage threshold. visa versa.
When looking at power MOSFETS, they also don't seem to suitable.
BJTs however I cant seem to find out with a high enough voltage threshold.

Sic JFET (silicone Carbide) - The rise time is too slow in order for them to be suitable choice.

If anyone has got any suggestions for a suitable FET , that has both a fast switching time (in the region of 1ns) and has a high voltage threshold (approximately 50v), please let me know.


texts:
I am struggling with a question(ideal npn) where there is only one resistor Re. Where and how do I start with this question?
Vbb=10V
Vcc=20V
Re=10kOhm
The Question states : determine the terminal voltages of the transistor in the circuit with respect to ground.
Also determine Vce. Vbe and Vcb


texts:
I have captured USB traffic between host and device operating at Full Speed. Then I am filtering on an Interrupt endpoint. bInterval value is 9 for this endpoint.
In the capture I am seeing IN token from host to device on this endpoint every 35 msec.

Based on my readings I was thinking, considering Full Speed operation, the host will send the IN tokens every 9 millisecond. Why am I seeing a 35 second delay between each IN packets?


texts: How do I know current across unknown load if I know voltage

texts:
If I know voltage across a load, but don't know load resistance, how do I know current going through load?

Do I put a resistor of 1K and calculate?

My voltage is square wave so multimeter only get average current. I want current square wave


texts: Arduino Time.h - Resets on Serial Connection for Sync

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I realize and understand the problem with arduino boards resetting whenever you open a serial connection as stated and answered here.

However, because of that I'm trying to figure out how various arduino-based clocks can actually handle a time sync over serial without just resetting every time.

For example, the BulbDial clock checks for a sync every time the loop comes around. But trying to sync via the processing sketch would just reset the controller and it would miss the sync. Granted, I do not have one of these clocks, but I based by design for the sync off of it and every time I open the serial connection to send the sync, the board just resets.

Is there something that I am missing?

Now, I have gotten it to work by placing a 10 uF cap between RESET and GND. But since others are able to do this without that cap I'd love to be able to do it without as well.

I've also written a python script that will set the time and I've tried all sorts of DTR, RTS configurations to try to force those lines to stay high and not reset the board during connection but I've had no luck. Code below:

    com = serial.Serial()
    com.baudrate = baud
    com.port = port
    com.timeout = 1
    com.rtscts=True
    com.dsrdtr=True
    print com
    com.open()

Any thoughts on how this is supposed to be done?


texts: RTC on MSP430 microcontroller with 32.768kHz crystal and low power

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I need to set timer to interrupt every second. I'm using 32.768kHz external crystal with MSP430G2553 MCU. The setup should consume < 10μA.

I tried this code but it consumed 80-90 μA.
What am I doing wrong?

Why is consumption too high?

int main(void) {
  WDTCTL = WDTPW | WDTHOLD;

  BCSCTL1 |= DIVA_3;    // divide by 8
  BCSCTL3 |= XCAP_3;

  //set timer
  TA1CCTL0 = CM_0 + CCIS_0 + OUTMOD_0 + CCIE;
  TA1CCR0 = 1020;
  TA1CTL = TASSEL_1 + ID_2 + MC_1;

  LPM3;
}

//interupt every 1000ms
#pragma vector=TIMER1_A0_VECTOR
__interrupt void TIMER1_A0_ISR(void)
{
}


texts: Isolation Circuit Question - How does this feedback work?

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I am completely stumped. I have been troubleshooting this circuit for some time, and is what powers another circuit. The thing is, I have no idea how this thing works (not well as of late, due to other design errors past this section of the project.) I am new to the engineering side of things, and am a little lost when it comes to diagnosing circuits.
Apparently, this thing works, trouble is, the designer got canned, he left no notes, and I can't find anything else like it out there on the web. U12 is a UC3842B current mode controller, Q9 PN #TSM850N06CX RFG , and the optoisolator, U15 is PN# CNY17F-1S. But, I have no idea how the jeezless thing is getting proper feedback through the optoisolator. I also am not sure on how the isolated voltage is set, I can only assume T1 is acting like a 1:1 transformer, and I have no idea how the Isense pin is being used here.
The data sheet for U12 leaves something to be desired, and I think I just need a little guidance to how to figure out how things work.