texts: Is it safe to use individual conductors removed from a multi-conductor cable?

texts:
I am working on setting up a research lab at a university as a graduate research assistant. We're working on power electronics in a three-phase environment, which means we'll be using at most five high-current wires per connection (three phases, neutral, and earth, though not always all of those). We already have bundled cables picked out—five-conductor "type W" cable (this in a few different wire gauges for different applications).

Now, we want to also have single-conductor high-current jumper links, for connecting two boards together (perhaps a rectifier and an inverter, or some power module and a load; we're going for generality here). Ideally, we'd have this in several different colors, but this combination of high current and high flexibility seems to be difficult to find with any sort of variety as to its coloration.

So my question is this: Is it safe to cut the outer sheath off of that type W cable linked above, and use the five interior conductors as single cables in their own right? I'd imagine the insulation is up to the job, since it has to be able to withstand the full rated voltage between two adjacent conductors, but I'm not sure.

We're almost certainly going to just get standard single-color welding cable for these connections, but I can't help but be curious whether this would even be an option.


texts:
Right now i am thinking about changing all my alkaline 9V blocks to lithium blocks.
But I'm not sure how to load the cells. Sure...I could buy a charger...but I have enough chargers and a bench power supply at home already :P

I read that the 9V Li-ion blocks have a nominal voltage of 7.4 V and a maximum voltage of ~8.4 V. So it just seems to be two Li-ion batteries connected in series.

But I don't see any possibility of balancing on the blocks. Are the cells internally balanced? Or am I missing something?


texts: VCC trace routing on a two-layer board with TQFP chip

texts:
I'm just trying to layout a PCB with CY7C68013A (100-pin TQFP) on it. It's a sort of experiment, so I'd like to use 2-layer PCB, 4 layer PCBs are just too expensive. This leads to some interesting layout issues (note, that I'm more concerned with signal integrity than EMI).

I decided to use bottom layer as a ground plane, yet I have a really hard time choosing the best way to route the VCC trace. There are a few high-speed signals routed from the left and bottom edges of the chip to the connector on the left side of the board (carrying up to ~30MHz signals). There are 3 VCC/GND pairs on the left side, and 3 more on the bottom of the chip, to make things complex - I need to route VCC away from between those fast signals..

This makes it necessary to either:

a) route parts of these signals on the bottom layer and keep most VCC on top

b) route these signals on top of the board and route some segments of VCC on the bottom layer (but this introduces holes in the bottom layer's ground plane, exactly underneath the signal traces, making the return path's loop bigger)

Any advice? Is it OK to route the VCC underneath the chip on the bottom layer?
This would let me leave the ground solid under my fast signals.

How about top layer? (this would require a power track connected to the pin from one side, and decoupling capacitor stub track from the other side - that doesn't sound good to me).

Perhaps I'm overestimating the potential issues, but it's interesting problem on its own - I can imagine many projects choosing 2-layer PCBs to lower the costs.


texts:
I am designing a capacitive touch keypad using cypress MBR series. The design guide has an excel spreadsheet to help with max trace length and button dia requirements. The idea is to keep the button + trace capacitance in a working range. For the same, they have mentioned capacitance per inch of trace length in pF as shown in table below:

There is no mention of trace width in the document (64 mils appears to be the pcb thickness because it's equal to 1.6mm - one of the standard pcb thickness).

Is trace capacitance per unit length is independent of trace width?

Is there any recommended trace width that I should use or can I use anything as per my convenience?


texts: Given is the circuit for supply independent current biasing. What are the spice models that should be used in place of nmos and pmos so thay we get the desired output? It is required that the aspect ratio of M2 should be 'K' times the aspect ratio of M1. Should the 'K'  be obtained by tying the  gate,drain,source of the respective mosfets?


texts: Why is the rotor power factor of the induction motor lagging?

texts:
A 460-V 60-Hz four-pole Y-connected induction motor is rated at 25 hp. The equivalent circuit parameters are R1 = 0.15 Ω, R2 = 0.154 Ω, XM = 20 Ω, X1 = 0.852 Ω, and X2 = 1.066 Ω.

The rotor power factor is found using θ = tan-1(X2/R2/s) = tan-1(1.066/7.7) = 7.88° and PF = cos(7.88°) = 0.991 and is stated to be lagging.

Why is the power factor lagging and not leading? I thought if the angle was positive, the power factor is leading.


texts: Where to place a RC filter regarding decoupling capacitor?

texts:
I would like to add a low-pass RC filter (500Hz) to the power rail of a TLV2782 op-amp. Datasheet of TLV2782 recommends two decoupling capacitors: 0.1uF and 4.7uF and they are currently placed on the VDD pin of the TLV2782.

Where should I place the RC filter? Should I place it before those decoupling capacitors or after? Should I consider that the decoupling 0.1uF capacitor is the capacitor of my RC filter (then forcing a resistor value) or should I consider the decoupling and the filter independently?

Any advice would be appreciated.


texts: Independence of the two channel architecture of LPDDR4

texts:
I'm working on a project involving LPDDR4. I've read the pertinent sections of the recently released JEDEC LPDDR4 spec. I have several questions regarding the independence of the two channel architecture. These answers to these questions may be self-evident to those with a strong knowledge of DDR, but this is my first experience with it. My questions are:

Are the mode registers per channel or per device?
Do CK_t/c_A and CK_t/c_B need to be the same frequency?  If not, how different can they be?
Are CA_A and CA_B completely independent or are they intended to be identical?


texts: Measuring the bode plot of an op-amp circuit

texts:
So a few weeks ago I had to do an experiment and one of the exercises was to measure the bode plot of an op-amp. The instructions told us to measure the voltage and phase difference at the points \$TP_{37}\$ and \$R_{41}\$. During the experiment, one of the instructors told us to use \$TP_{44}\$ instead of \$R_{41}\$.

However, when I look at the schematic of the circuit, I don't understand how these points will give me the correct information. The 2nd op-amp acts like a buffer, and shouldn't change the signal in any way (theoretically), so we were told to ignore it. What's the point then of taking the ratio of \$ TP_{44} \$ and \$TP_{37}\$? To my understanding you're supposed to take the ratio of \$V_{in}\$ (= \$TP_{41}\$) and \$V_{out}\$ (= \$TP_{42} \approx TP_{44} \approx TP_{37})\$. Anyone have an idea on what the correct method is?

Anyway, I found the following transfer function for the op-amp.

$$ H(s) = \frac{-C_1}{C_2} \frac{ \frac{1}{R_1C_1} +s }{ \frac{1}{R_2C_2} + s } \\  C_1 = 220pF, \quad C_2 = 100pF, \quad R_1 = R_2 = 22k\Omega$$

.

The measured voltages:

When I take the ratio of the voltages, none of them seems to follow the magnitude of the bode plot. I know that a 100% match is very unlikely, but it doesn't even come close. I've tried different combinations.

Does anyone know what kind of op-amp setup this is? I've looked all over google images for a similar setup, but couldn't find anything. I did however find this same setup in the book "Schaum's Outlines of Electronic Devices and Circuits (2nd ed.), p288". It only confirms my transfer function.

Any advice/help is greatly appreciated.

EDIT

Some of you pointed out that I should use JP22 as my input, and I agree. I was confused since in the task they asked to look at the signals on TP37 and R41.
The input signal should be 2.1V pk-pk.

Also I believe I'm supposed to calculate the bode plot of the whole circuit, not only from the first op-amp. The questions reads as:

"Measure the bode plot for voltage amplification and phase difference between input and output AC from 50Hz to 10MHz."

My apologies for this lack of clarity.


texts:
As a learning project, I'm trying to create a simple linear power supply using LM317.
The basic circuit is well documented on internet, but I want to create a variant that allows me to have multiple output channels.

One of these output channels is for internals of the power supply: powering up an INA219 to measure current drawn, an atmega328 and an LCD for display.

Ideally I want to have two independant variable output channels (1.25V - 12V) and a single internal output channel (5V).

I think the following circuit should work, on paper, but I am not sure it will be really usable in practice. I have the feeling that sharing the same input lines (and grounds) between all channels will create undesirable side effects between them, especially with ICs using spike currents like the LCD.

Here is my take at a circuit diagram:

The top part is the variable output channel, the bottom part is the internal 5V channel. They are both forked from the 15V input from a switching wall adapter.


texts: Feasibility of controlling a dimmable LED matrix

texts:
I have a beginners question: I'd like to create a custom LED matrix (at least 7x7; one-color only), where each row of LEDs can be dimmed separately or ideally even each LED. The whole thing should be controlled by an Arduino or some other microcontroller.

I have extensive programming knowledge, however my electronics knowledge is limited to those Thames-and-Kosmos kits I used to "play" with as a kid, i.e. I can interpret simple circuit diagrams but that's about it.
For now I'd only like to know if the following is doable, what the hardware requirements roughly would be and if a newbie like myself would be able to do this. Is there even a off-the-shelf hardware solution?

Thanks a lot for your answers and patience with a beginner.

Andreas

PS: My initially posted question contains wrong requirements (two-color LED) which is why I posted this quite similar question. One of the replies there links to a related thread which doesn't really help to answer my questions.


texts:
This past summer I installed a couple of 12 volt 100 watt solar cells on the roof of my caravan.

I was never naive enough to actually expect to get 100 watts out of them, but I've still been very disappointed with the actual power produced.

Here are my sums, have I missed something?

The Solar cells says 100W – that means it should produce 100 watts in the noonday sun on the equator at 25 C with an assumed solar radiation of 1000 watts per square meter.

There are maps published which suggest that in the UK were I live the peak solar radiation should be around 650 watts per square meter.

This brings the power I think I can expect down to 65 watts.

Then I need to adjust for the fact that performance goes down as temperature goes up.  (click here for details) .The Temperature Coefficient of Pmax for my panels is -0.40% per degree. That means for every degree above 25C it loses 0.40% of its power. I’m guessing that the temperature on the roof of my caravan is quite warm – lets say 50C, that’s 25 degrees above test conditions, or a total power reduction of 12.5% due to the temperature. So deduct 12.5% off my UK power of 65 watts  and I’m down to about 57 watts.

I'm calculating my actual power output simply by measuring the voltage across the solar panels and multiplying by the current through them (P=IV). The largest value I've seen is about 18-22 watts - less than half what my most pessimistic theoretical calculations have suggested.

I've been doing my test in the middle of the day, with the sun vertically overhead in the middle of the best summer the UK has experienced for 40 years.

Either I've missed something in my calculations, or I've made an error in my testing, or my panels are just cheap cr4p.

Further info.....

I used to be an electronics engineer so I hope I’ve avoided any really stupid mistakes, however this is my first time working with solar panels so their could be something I’ve missed.
Current and voltage has been measured repeatedly with a number of quality fluke multi-meters, similar values from all of the them.
Current and voltage are being measured on the input side of the solar regulator so my measurements should be giving me power before taking into account any regulator inefficiencies.
I've installed two identical solar cells and have had very similar results with both, so it's  unlikely to be just a faulty unit.

The specification for the panels (according to the sticker on the back) is...

Guangzhou Jinsheng New Energy Technology Co Ltd
Model No: JS100W-12MP
Wattage: 100W
Dimensions(mm):1100*540*2
Cell Type: Monocrystaline
Peak Power (Pmax) : 100W
Maximum Power Voltage (Vmp) : DC18.0V
Maximum Power Current (Imp) : 5.6A
Open circuit Voltage (Voc) : DC22.5V
Short-circuit Current (Isc) :5.8A
Maximum System Voltage (V) : DC 1000V
Test Conditions : AM1.5, Ec=1000W/m2, TC=25C
Made in China

In summary, the most power I've ever managed to get out of a 100w panel is about 20w. Why?

UPDATE - I'm not sure on the spec for the solar regulator, I don't have it in front of me now, it was a closing-down-sale item from Maplin, so I'm guess it was pretty low spec. I can remember that when wired up as-per the spec the battery charging voltage would be about 14.4 volts, and the solar-cell voltage would drop to about 16 volts (2 volts below the max power voltage quoted)

I don't currently have access to my caravan (it's in storage for winter) and when I do it's not currently sunny enough to produce much power, so I'd like to re-phrase my question. Can anyone point me in the direction of some worked-examples of how to calculate the practical power output of solar cells and what I'd need to do to achieve maximum power? Comments so far seem to be suggesting that my solar regulator may not be optimum. But maybe there's something else that I've missed?


texts:
I'd like to complete an electronics project by allowing it to be powered over USB-C. The specification is complex, I'd love some help understanding it!

I'll need to draw ~ 250mA at 5V for my project (though if there's an appreciable difference for drawing up to 1.5A I'd be interested to hear about it); assuming I have a dumb USB-C socket, what circuit should I build to:

Provide 5V, ~250mA for my project
Suitably protect the power source from issues with my project

Thanks!


texts: Ground in the circuit of full wave rectifier

texts:
While performing rectification task in lab. We use 0V and 12V as negative and positive terminal of input supply in central tap full wave rectifier and -6V and 6V as negative and positive terminal of input supply in bridge rectifier.
We are told that we have to use 0V(ground) in central tap rectifier but there is no need of ground in bridge rectifier.
Please tell me what is the reason behind it and why ground is not needed in bridge rectifier?


texts: How does this transformerless 5V power supply work?

texts:
I recently took apart a crock-pot cooker that stopped working correctly.

It had two boards:

One that dealt with the high-voltage for controlling output to the heating element
The other had a 4-bit microcontroller and a few buttons/LEDs.

I was surprised to see no transformer anywhere, and very few parts, considering there was a signal labeled +5V for powering the microcontroller.

I reverse-engineered the schematic:

simulate this circuit – Schematic created using CircuitLab

Is it me or is this a really crappy design?

I was very surprised to see that the DC GND was connected directly to the 120VAC L!

Is the 5V DC basically just a rectifier with a voltage divider?


texts:
The instruction call Rn,sub is a two word instruction.Assuming that PC is incremented during the fetch cycle of the first word of the instruction,its resister transfer operation is

Rn<=PC+1;
PC<=M[PC];

Someone please help me to calculate minimum clock cycles needed during the execution cycle of the instruction.I am student of computer science and not very good in microprocessor ,please explain how to count minimum clock cycles?

Should it not be 5 in 8085.

For loading PC to ALU register
Cycle to increment PC (PC+1)
Transferring it to Rn from accumulator.
2 cycles for memory read operation.

Please let me know where i am wrong ? Please.


texts: Proper way of drawing a lot of current from a 12v Battery

texts:
Introduction

I am using a DC motor to raise this desk that I purchased on amazon.

I first purchased this DC motor that was capable of lifting the desk. This DC motor costs almost $40 dollars and it is very slow! I know it is slow because it is a trade off between torque and speed.

Because it was so slow I started using my electric drill to raise/lower my desk. As a result I replaced that slow motor with the motor of the drill. It now looks like this:

The electric drill costs the same amount of money than the DC motor that I purchased and it is 5 times faster with the same amount of torque! Because I was not able to find a DC motor with the same amount of torque I ended up buying the electric drill instead of a DC motor.**

Anyways maybe someone can point me on the right direction on where to buy a DC motor that has the same torque and RPM as my electric drill so that in the future I do not have to do all this trouble.

Question

Everything worked amazing at the beginning. Now one of the batteries of the drill has stopped working and I am guessing the other battery will stop working soon too because its life keeps getting shorter. I believe the reason is because the batteries are drawing too much current. I know I can limit the amount of current by placing some resistance. If I place resistance then the motor will not have enough strength to carry the desk. The battery gets hot and that is another sign why I may be drawing a lot of current.

This question states that is dangerous to draw a lot of current (amps) from a battery:
What happens if you draw too much current from a 12 volt sealed lead acid battery?

Solutions

These are my solutions please help me determine the best one.

Use the first DC motor that I purchased that is too slow.
With this solution I can place resistance to the battery and very little current is drawn. The battery life is way longer. I would like to discard this solution because it takes forever to raise the desk.
Purchase the same 12V batteries that come with the electric drill. Instead of using one at a time use them in parallel. If I use the batteries in parallel I will be drawing half of the current on each thus making it safer? Should I purchase 4 to be even safer?
Purchase a 24V battery and a 5 Ohm 100W resistor. Maybe if I increase the voltage the DC motor will have more strengh to lift the table. If I have double the strength then maybe I can use some resistance to limit the current?


texts: Can you implement a control algorithm and send the inputs via xbee?

texts:
I know this question is little bit vague, but let's say that I have a robot or a quadrotor to control. I want to implement the control algorithm (PID, robust, or LQR) in the PC not in the robot/quad, to receive the feedback and send the inputs via xbee.

Can the xbee keep up, and do all the receiving and sending the inputs and the feedback, without delays?

One xbee is in the robot/quad and the other is plugged to the PC. You can say it's a 6 degree of freedom, (six variables) what type of xbee? I haven't got one yet, so can the cheapest do that, or the average one?


texts: How can I design the BJT based inverter question given in description?

texts:
QUES: Design a BJT based inverter  operated from a 1.5 V supply.With the input connected to the 1.5 V supply through a resistance equal to RC, the total power dissipation should be 1 mW and forced β should be 10. Use VBE = 0.7 V and VCEsat = 0.2 V

I tried solving this but I am not sure that total dissipation will be due to Rc only or both Rc and Rb. Please help.
Below is my solved design.


texts:
I have read some articals about design of Hi-Fi power amps and from what i understand most of the amplifiers use 2-3 or 4 stage amplification while 3 stage is most common (trans-admitance -> trans-impedance -> unity power stage)

why in most amplifiers circuits i have seen the design implements the trans-admitance stage from descrete op-amp and current source (4-6 BJTs) and not IC op-amp?

ie what are the benefits of desinging it from descrete transistors and not ICs?


texts:
He everybody.
I've already done my firts PCB project. I did draw Boost converter and I have a few quenstions about my layout. How is my layout? Can I improve my layout and placement?
If you check and give me some tips I'll be happy.


texts: Choosing the right capacitors for LM2596

texts:
Picture above is from LM2596 datasheet.

Is the recommended values is for fixed output voltages? If yes how to choose right capacitor value for variable output?

What's the role of Iload in choosing capacitors?

My input voltage is 24V with the output voltage of 3-23V.


texts: How to panelize Gerber files using Proteus ARES?

texts:
Suppose I have a few different sets of Gerber files (generated from an external software package, say, EagleCAD) corresponding to different boards.

How do I go about panelizing them on Proteus (i.e., in this case, merging the multiple different designs) onto one panel prior to production?

I'm wondering if it's possible to also merge externally generated Gerbers in this way, as opposed to just Proteus's project files.


texts: How do I decide the bandwidth of a driver through 'input transition rise and fall rate'?

texts:
I am carrying out a design with a driver:74LVC1G125 datasheet of 74LVC1G125. Signal that will go through this driver is about 600khz so I have to know the bandwaidth of 74LVC1G125. I have read the datasheet and I can not find anything about bandwidth but an unknown parameter:input transition rise and fall rate.

I think it must has something to do with the bandwidth of 74LVC1G125 and I find a description about itinput transition rise and fall rate.Unluckily, it makes me more confused that this parameter is about the amount of ground current. So can anyone give suggestions about bandwidth of this driver?


texts:
I'm trying to build a +/- 150V battery powered DC power supply variable power supply.
I have two of these 150V nixie power supplies: http://desmith.net/NMdS/Electronics/NixiePSU.html
And was thinking about putting two of them in series, and setting ground to the middle which gives me -150V and +150V. I would then feed these into two IRF740A MOSFETs (same as those used in the PSU). The IRF740s would then receive an external control voltage to control the output. In my mind the MOSFETs kind of work as a voltage divider. Here is the basic schematic:

(source: 41j.com)
Does this idea make sense? What have I missed?


texts:
This question is out of curiosity. I know fairly well that mains SMPS can suffer from bad electrolytic caps. Now I wonder if replacing all electrolytics with MLCCs work? Will it make a more durable SMPS?

If MLCCs work as filter caps, why the manufacturers are still using electrolytics? Here I mean SMPS a sold as parts of industrial equipment or long-lasting equipment (like computer servers that can be designed to last for 20-50 years)


texts: Parallel resistor before voltage amplifier

texts:
For my project, I would like to amplify the output from a photodetector for subsequent analysis with an oscilloscope.
The output of the photodetector is a current. Since we are using a voltage-amplifier, we would like to "convert" this output to a voltage by having a resistor after the photodetector but before the amplifier. Would you recommend using a resistor in series (e.g. a 50 Ohm series resistor) or would you rather use a t-piece with e.g. a 50 Ohm termination?
It would be really interesting to know the difference between those two options.
Thanks a lot for your help!! :)


texts: Can I make KiCAD pcbnew NOT place all components at (0,0)

texts:
In EAGLE, when you create a board from an existing schematic or incrementally add components to a linked board/schematic project, it does not overlap components in the board file.

In KiCAD/Pcbnew I drew a schematic and created a board from it. Every component was placed at (0,0) which is the upper left hand corner.

I would like the components to be "exploded". That is to say non-overlapping so I can find/grab what I want instead of spending 5 minutes dragging apart 30+ footprints.


texts:
While studying the Go back n protocol,in a part of the C code its written :

static boolean between(seq _nr a, seq _nr b, seq _nr c)
{
/
* Return true if a <= b < c circularly; false otherwise.*/
if (((a <= b) && (b < c)) || ((c < a) && (a <= b)) || ((b < c) && (c < a)))
return(true);
else
return(false);
}

What does this mean,can you explain it to me?


texts:
I am looking to have a program which would alert me whenever a certain RFID tag would no longer be read, however I don't want to use NFC since I need the distance to be of at least 50cm+.
Is there anyway to transmit an RFID tag over that distance which would be more cost, space and power effective then just doing it over bluetooth?


texts: Load spread metric issues in power amplifiers

texts: Power amplifier saturation or maximum power depends a lot on the load seen by the collector or the drain of the amplifier. If the load impedance varies across frequency, how serious is this in terms of the PA performance? I would be particularly interested to know the impact of load spread on class F or inverse F power amplifiers.


texts: Variable frequency for sine wave in Verilog

texts:
I am trying to implement 4 different frequencies at which sine wave is going to be simulated in testbench. I am using a counter to do so. However, it can not toggle clk_out in simulation window. Not sure where the error is.

Code:

module functionGenerator(Clk,data_out, reg0, clk_out);
//declare input and output
    input Clk;
    output [9:0] data_out;
    output reg clk_out;
    input [3:0] reg0;
    reg [31:0] constantNumber;
    reg [9:0] sine [0:99];
    integer i;
    reg [9:0] data_out;
    reg [31:0] count;
//Initialize the sine rom with samples.
    initial begin
        i = 0;
        clk_out = 0;

        sine[0] = 0;        sine[1] = 10;        sine[2] = 20;        sine[3] = 29;        sine[4] = 39;
        sine[5] = 48;       sine[6] = 58;        sine[7] = 67;        sine[8] = 75;        sine[9] = 84;
        sine[10] = 92;      sine[11] = 100;      sine[12] = 107;      sine[13] = 114;      sine[14] = 120;
        sine[15] = 126;     sine[16] = 132;      sine[17] = 137;      sine[18] = 141;      sine[19] = 145;
        sine[20] = 149;     sine[21] = 151;      sine[22] = 153;      sine[23] = 155;      sine[24] = 156;
        sine[25] = 156;

    end

    always @ (reg0)
    begin
        if(reg0 == 4'b0000)
            constantNumber = 50;
        else if(reg0 == 4'b0001)
            constantNumber = 100;
        else if(reg0 == 4'b0010)
            constantNumber = 200;
        else if(reg0 == 4'b0100)
            constantNumber = 300;
        else if(reg0 == 4'b1000)
            constantNumber = 400;
        else
            constantNumber = 500;
    end

    always @ (posedge(Clk))
    begin
        if (count == constantNumber - 1)
            begin
            count <= 32'b0;
            end
        else
            begin
            count <= count + 1;
            end
    end

    always @ (posedge(Clk))
    begin
        if (count == constantNumber - 1)
            clk_out <= ~clk_out;
        else
            clk_out <= clk_out;
    end

    //At every change in clk_out state, output a sine wave sample.
    always@ (clk_out)
        begin
            if ( i < 25 )
               data_out = sine[i];
            else if ( i < 50 )
               data_out = sine[50 - i];
            else if  ( i < 75 )
               data_out = - sine[i - 50];
            else
               data_out = - sine[100 - i];
            i = i+ 1;
            if(i == 100)
                i = 0;
    end
endmodule

and Test bench:

module functionGeneratror_tb();

    // Inputs
    reg Clk;
    reg reg0;
    wire clk_out;
    // Outputs
    wire [9:0] data_out;

    // Instantiate the Unit Under Test (UUT)
    functionGenerator uut (
        .Clk(Clk),
        .data_out(data_out),
        .reg0(reg0),
        .clk_out(clk_out)

    );

    //Generate a clock with 10 ns clock period.
    initial
    begin
    Clk = 0;
    reg0 = 4'b0000;
    end
    always #5 Clk = ~Clk;

endmodule


texts:
I have 4 data lines that I want to put to high-Z if a pin (let's call it EN_OUT) is high (or low, if necessary), otherwise connect through.  I've successfully done that by putting an N-FET on each line (gate to EN_OUT).  For space considerations, I'd like to replace that with a logic IC that I'm sure exists... I'm just failing to figure out what it would be called :)

The closest I've come is a 4x1:1 de/mux like the NXP 74HC4066, which is fine but it has an enable pin for each circuit and is a tiny bit larger than I'd like.  I was hoping there'd be one with a single EN for all 4 circuits.

Can someone give me a nudge on what that would be called?  Thanks.


texts:
I'm preparing to teach some people regarding filters, and I'm confused regarding the use of the LC-filter circuit, specifically the circuit below:

simulate this circuit – Schematic created using CircuitLab

Taking the output at the capacitor, it seems you get a strange looking low pass filter with the transfer function

\$H(\omega)=1/(1-(\omega^2LC)\$

It's similar to a RC circuit, but at the cutoff frequency, there's a spike in the magnitude. With the basic RC/RL filter circuits, the cutoff frequency occurs when the power is 3 dB below the max value, but with the LC circuit, calculating that leads to a very long equation to the 4th power. With that, why do we calculate the resonance frequencies when the denominator is equal to 0? Similarly, since there's no imaginary components, what does that say about the phase of the circuit with regards to frequency?


texts: Can twisted pair replaced by two wires which are closely placed?

texts:
If I have differential signal wires, can I place two wires closely 1mm-2mm gap between them but not twisted? (1mm or 2mm gap is fixed it won't change from place to place )

I am using Differential I2C modules

because having a twisted wire in the application is not possible

how bad this will affect the signal?

are there any other issues with the above setup?
example

edited

I2C communicate through cables long-distance up to 10ft-20ft

There is no noise from motors or magnetic fields around my application

I can use very thin cables (<1mm) in my application


texts:
In the code below, I want to pull out statements surrounding the the ** asterisks ** below.
stateS0 = 1' and o_done = '1'

and
o_done = '1' and stateS0 = '0'

into separate comparisons using if or elseif.
I am struggling at how to pull out and compare if I am in state S0 and o_done = 1 and I am in state 1 and o_done = 1 into seperate if, then, else, elsif statements.
        process begin
        wait until rising_edge(clk);
        if (reset = '1') then
          stuff;
        else
          **if( StateS0 = '1' AND o_done = '1' ) then**
            stuff;
          elsif( ...stuff... ) then
            stuff;
          end if;
        end if;
      end process;

      process begin
        wait until rising_edge(clk);
        if (reset = '1') then
          o_done <= '0';
        else
          if ( ...stuff ...) then
            o_done <= '1';
          **elsif ( o_done = '1' AND StateS0 = '0' ) then**
            o_done <= '1';
          else
            o_done <= '0';
          end if;
        end if;
      end process;

I was thinking something like:
if stateS0=0 then if
o_done='1' then...

if o_done='1' then if
stateS0='1' then...

but can you do...
process begin
    wait until rising_edge(clk);
    if (reset = '1') then
      stuff;
    else
    if( state0 = '1') then
        if o_done='1' then
                stuff;
        end if;
    end if;
      elsif( stuff ) then
                stuff;
    end if;
  end process;

is that legal code ?
Or is this legal ?
  process begin
    wait until rising_edge(clk);
    if (reset = '1') then
      o_done <= '0';
    else
      if ( stuff ) then
        o_done <= '1';
      elsif ( o_done = '1') then
       if state0 = '0' ) then
        o_done <= '1';
      else
        o_done <= '0';
      end if;
    end if;
  end process;

But I am not sure about if I am nesting these right.  Can you nest an:
if
if
end if
end if

within after an elsif or else ?
Can you nest elseif in if, then else statements ?  Or elseif only check 0 or 1 conditions and not combinatorial conditions like if then else can ?


texts: AVR (attiny24) resets itself driving more than 5 outputs under no load

texts:
I have the blink code below running on an attiny24 with the default fuses, via Atmel Studio 6.  If I set DDRA to any combination of 5 pins (or set DDRA to 0xFF and then blink by setting PORTA to any combination of 5 pins) then it works but as soon as I use 6 pins it resets itself.  The PORTB.0 toggle at start up demonstrates the reset.

The usual cause for this sort of behaviour is sourcing or sinking too much current on the outputs, however this is happening when the outputs are left open, nothing attached, so I can't see what's causing it.  Any suggestions?

int main(void)
{
  // DEBUG: Toggle PORTB.0 to demonstrate AVR reset.
  DDRB = 0x01; PORTB ^= 0x01; _delay_ms(10); PORTB ^= 0x01;

  // Output 6 pins at once (change to 5 pins and AVR does not reset).
  DDRA = 0b00111111;
  for (;;)
  {
    PORTA = 0xff;
    _delay_ms(1000);
    PORTA = 0x00;
    _delay_ms(1000);
  }
}

I've tried the usual suspects, power supply, running with AVRISP disconnected and ensuring there is a cap between +VE and GND.  Also tried setting pins individually and as soon as it hits 6 it resets.


texts: If I have 8-bit parallel data being clocked out of a chip at 250MHz, is there some way I can buffer it? I only need to store about 1kB. Preferably this would be a FIFO. Does such a fast FIFO exist at a reasonable price (


texts:
So I was writing some verilog in quartus and wondering why the heck it was misbehaving.

I eventually discovered the problem was some constants where I had inadvertantly used a backtick instead of a single quote. For example I had 32`hdeadbeef instead of 32'hdeadbeef.

What I find surprising is that this compiled, did I find a bug in quartus? is this some obscure bit of verilog syntax? if so what does it mean?


texts:
Why is this transfer function unstable? The poles are \$0\$ and \$-4\$, so they are in the negative half-plane, theoretically it was to be stable. Can anyone explain to me what makes it unstable?

$$G(s)=\frac{10}{s^2+4s}$$


texts: LTSpice Transient Analysis - How to specify the number of data points per step

texts:
I performed a 1us duration transient analysis on a basic inverting op-amp circuit with the resistor value Rx sweeping from 846 Ohms to 1385 Ohms. When I export the data to a text file (File -> Export data as text), the resulting text file has multiple data points for each "step". As an example, for Rx = 848, LTSpice creates 3 data points at 0s, 819ns, and 1us (See Figure 2).

Parsing this text file in excel is a bit annoying but not impossible, I just need to extract every 4th element. However, the problem is that LTSpice generates more data points for some "steps". In Figure 3, for Rx = 1.38k, LTSpice generates 4 data points instead of 3. Now data parsing in excel becomes annoying because sometimes I need to extract every 5th element, while other times I need to extract every 6th element.

So my question is: Is there a way to specify the number of data points created in each step?

Figure 1:

Figure 2:

Figure 3:


texts: 230V AC / 460V DC Optocoupler using Led and Voltage Divider

texts:
I am building a primitive optocoupler to sense if a bulb has blown/if current is flowing.
It receives either 230VAC or 230VDC (rectified..) as supply.

I have calculated and built a voltage divider as pictured, but I am getting no LED action on 230AC tests, would dearly love any tips on how to get it working, but still keep it "primitive" simple as a design consideration :D
So what's wrong with this picture?!

Details:
The bulb measures 77 Ohm across the filament, and acts as a resistor (R2) in my calculations (and as the switch..).

R1 (two resistors in parralell) is 3 Ohm as measured-.
I calculate 11V@230V AC and 17V@460DC, as the voltage across the LED (but measure nothing..)

I plan to buy a 5W,  1.7 Ohm to get a more manageable 5V / 10V combo, and choose the LED resistor accordingly.

I will put a rectifying diode in series with the led I think..
Is there any advantage crossing two LEDS to get a steady light on AC, or should I just smooth the 60hz signal with cap on the LDR side?


texts:
We've noticed that off-the-shelf LEDs exhibit some change in the shape (and sometimes peak) of their spectrum as the amount of current flowing through them changes.

For example, a UV LED we tested showed the following change in the shape of it's spectrum when we changed from 0.2 mA (black line) to 2 mA (orange and green line).

According to some information I've found, the magnitude of this effect may relate to the quality of the semiconductor crystal used during manufacturing.

I'm wondering if anyone knows of a supplier that produces extremely high quality LEDs that may exhibit more stable spectra. Or, perhaps there is another solution someone is aware of to improve the spectral stability of LEDs vs. current.


texts: Is this current clamp meter measuring correct according to its specs?

texts:
A 24V DC power supply is supplying around 2.4A to a pure resistive load.
The input voltage is 230Vrms. So I estimated the rms current drawn from the power network as:

P/230 = (24*2.4)/230 = 250mA.

And with a multimeter this current is measured as around 260mA.
So it was consistent.

But when I measured with a current clampmeter(which is very new with a calibration certificate),
the clampmeter shows around 430mA.

(I measure the rms value of the Line current in both multimeter and clampmeter cases)

Here is the manual of the clampmeter. And under the electrical specifications it provides the following:

And here is the part from the calibration certificate:

Given the electrical characteristics and the calibration information, is 430mA measurement for a 260mA current expected for the provided error range or something is wrong?


texts:
I've been researching here and on google regarding potential battery technologies for a toy that I want to make for my kids.  I was hoping to get others' perspectives on this, keeping in mind that this is for a child.

I'm trying to look at this from all angles, but safety is the most important.  Here are the things I have come up with:

volatility: can the cell explode if mistreated, i.e. charged too long, toy thrown around, etc.
lifespan: does my son have to keep an eye on the toy to make sure it's always charged?
size: can I even fit the cell in the toy?
cost: cheaper is obviously better

Have I missed anything obvious?

As far as those four points go, here is what I have found from my research so far:

volatility: LiPo sure sounds like you have to be more careful.  There are battery packs that have overvoltage and undervoltage protection circuitry built-in, but I would like to see if I can find an off-board circuit that can be built for less money since that's NRE and cells might need to be changed.  Battery management ICs like the MCP73831 should help, as well as a fuel gauge like the MAX17043.  Not sure if there's anything else I can do.  NiMH has similar ICs available, like the DS2715 for charging and the BQ2014NS-D120 fuel gauge.  Either technology would probably benefit from a temperature sensor / cutoff of some kind.  LiPo looks like it does not like shock, so having the toy thrown onto the pavement might not be a good thing.
lifespan: LiPo shouldn't be allowed to discharge below a threshold voltage.  Neither should NiMH.  Need to check if fuel gauge can cut off toy's circuit if below threshold.
size: LiPo has the huge advantage here.  At 3.7V per cell, I only need a 1S LiPo, and they come in all kinds of (small) sizes.  NiMH will likely require 3 1/3-AAA cells, which I should still be able to fit.
cost: LiPo batteries without protection circuitry are super cheap, like $2 in single quantities.  The ones I have found with protection circuitry are larger and 4x the price.  The NiMH 1/3-AAA cells I found were about the same price.  No mention of protection circuitry so I don't know if that's important if I have the battery management IC (same goes for LiPo)

I'd love to hear what others have to say about these points.  Did I miss anything really critical, and just as importantly, did I post any bad information about these two battery types?

EDIT -- I have added LiFePO4 as suggested by Russell and AndreKr.  I don't necessarily trust myself to design a proper circuit that is bulletproof, so I am looking at the MCP73123 since its current limitations are within the range of the single cell that I want to charge.  I saw the Tenergy cells previously, but wasn't sure about them and ended up ordering a few of these from a shop in the US: http://www.batteryspace.com/LiFePO4-Rechargeable-14430-Cell-3.2V-400-mAh-0.4A-Rate-1.28Wh.aspx.  I really like how they can be ordered with tabs attached, which is what I did.

So right now I have a LiPo protected cell and MCP73831-based charger coming from Sparkfun so I can play with it, as well as the Powerizer LiFePO4 cell and a sample of the MCP73123 which I'll somehow try to breadboard to test its charging capability.

I'm going to look around, but if anyone knows of good app notes to make a PIC-based LiFePO4 charger that explains constant-current source circuits, I'm all ears!  Thank you for your input.


texts: Multi-channel Wireless Microphone vs Home Wireless Telephone System

texts:
I'm curious why a wireless microphone system for school plays requires a multi-channel receiver while a home telephone system allows as many conversation participants as there are handsets with only one base receiver???

My daughter in law is a school drama teacher and needs good wireless microphones for her 6th through 8th graders play productions.  How do home phone systems work that multiple people can be speaking on one base receiver, while each wireless microphone requires it's own frequency and receiver?  I'd like to build a lavalier microphone w/pocket transmitters for the kids that can all be received by the same base model and amplified out to the speakers.  I think it would be fun to base it on a home wireless phone set with 8 or more handsets.  Is that possible?


texts: How does the output voltage of an Op-Amp swing to keep the inverting terminal at virtual ground in this circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

Vout should be -10 volts according to the voltage gain equation of inverting amplifier which is based on the rule of op amp that A is at zero volts. Here the output is grounded and the node A becomes 0.91 V (i.e) it is not at virtual ground. What would happen now? would the output voltage change? if it does change I am having a hard time understanding how it would?


texts: Using S-mosfets to construct AND, do the nand gates need to have high resistance?

texts: In order for the out to receive most of the current, are R3 and R5 selected large to prevent waste of current to the ground? This is an AB or !(!A or !B) from agarwal lang.


texts: 5V power supply using 7805 with multiple outputs

texts:
I need to make a 5V power supply using LM7805 IC but it should have multiple outputs I'll be needing 6 outputs for my project.
Can anyone guide me how do I build a circuit on multisim for the same?


texts: 3rd lumped circuit abstraction postulate

texts:
So i was reading Anant Agarwal's book Foundation of Circuits and stumble upon this postulate

"Operate in the regime in which signal timescales of interest are much
larger than the propagation delay of electromagnetic waves across the
lumped elements"

"The signal timescales must be much larger than the propagation delay of
electromagnetic waves through the circuit."

Why is that the signal timescale be so much larger than the propagation delay of electromagnetic waves? I dont get the consequences if we are to bypass this limitation. Thank you


texts:
I have a battery application. With an 11.1 V battery input, I need to maintain a 12 V, 2 A output as the battery discharges.

I bought a 1500 mAh, 11.1 V LiPo battery pack with a 35 C rating and I fully charged and balanced it.

I also got an LM3481 SEPIC mode dev board.

The test setup

Battery feeds the input of the boost converter, the output of the boost converter goes to an electronic load.

Load is a 1.2 A constant current load.

The problem

The test starts off fine, but quickly becomes out of control. The battery input current keep going up and up, within 7 minutes and battery current reaches almost 4 A and rising. The output stays at 12 V at 1 A.

What I think is the issue

I think this is due to the internal resistance of the battery. Once the current starts to flow, the voltage drop across the internal resistance will cause the input voltage to drop, therefore the boost convert will have to draw more current to keep the output current going, then the resistance would drop even more voltage, causing more current to be drawn. This just keeps happening in a "runaway" unstable system.

Possible Solution

Regulate the input current. Put a max input current based on the current load. If the input current gets too high, control the boost converter via a DAC to lower the output voltage, and keep the input current at that max value.

But that max input current draw will depend on what the load is. If the load requires an input current of 500 mA, I would want the input current to limit to be around 500 mA, but if the load changes, so does that set point.

Questions

1) Is this a common problem using boost converters with batteries?

2) Did I just buy a bad battery?

3) What would work for this application?

4) This battery that I bought seems like it has really high internal resistance. Like 1.65 Ω (for 3 cells in series). I put on a 3 A load and the battery voltage drops very low!

Sorry I don't have exact numbers on that, I didn't write it down. What is a normal internal resistance for a LiPo battery? For a 35 C rated battery, there is no way it would be able to provide 35 times its capacity and have any voltage left over for the load. It is a 1500 mAh battery.

Extra Tests

I put it on my charger to get some metrics that it gives me

When I put it in balancing mode. I get this reading for each cell

Cell 1 = 4.06

Cell 2 = 4.06

Cell 3 = 4.06

Then I put it in discharge mode.

Open (no load) voltage 12.06V

Then it goes to 500mA load
The voltage immediately goes down to 11.18V

While discharging at 500mA it also gives each cell voltage

Cell 1 = 3.48

Cell 2 = 4.03

Cell 3 = 4.03

Cell 1 is not balanced at all, even though the balancing mode reads that it is.

Should LiPo battery drop that much voltage at 500mA load?

12.06-11.18 = 880mV

880mV/500mA = 1.76 Ohms of internal resistance.

I tested both batteries. They came in a two pack. Could both be bad?
Is Floureon a bad brand?


texts:
I asked something similar here.
Now, when I make my circuit, I've seen that I don't need something that gives a pulse after being powered-up, but I just need a delayed pulse.

I know nothing about electronics, so here my (easy?) question.

Which circuit do I need, when I want to give a input pulse with a push-button (16V DC), a delay of 0.5 s and then an output pulse?
This pulse doesn't have to be the same length.

I'm open to everything. I know that, in my previous question, the solution was with a 555 timer. Now it is not necessary. I only need a (cheap) circuit that does the things I want.

EDIT: I know this is more or less a duplicate of my previous question, and my english is not very good.
The point is: I know nothing about electronics and I know the circuit I need will be similar to what I already have in the previous answers. I know that. But I'm not capable to adapt that solution, sorry. Is there someone so kind to help me. A solution with two 555 timers is good, but will someone be so kind to make a scheme? Please?


texts: Cascading Non-Inverting Amplifiers in LTSPICE

texts:
I am trying to simulate in LTSPICE a circuit containing two op amps cascaded in series (so that individual gains will be multiplied) but for some reason the gain of the first stage is higher than the last stage, but when I remove the power pins of the last stage, the circuit behaves normally. What is happening?
I am trying to do a frequency sweep and have tried two different op amps (TL072, NE5532) but they both behave abnormally. I don't know what i am doing wrong.
I got my op amp spice models from TI.


texts: Help wiring multiple different colored LED lights

texts:
I am working on a project right now, and it is the first time that I have worked with wiring anything. I have 70 LED lights. 10 red, 10 orange, 10 yellow, 10 green, 10 blue, 10 purple, and 10 pink. I know that the red, orange and yellow have a 2v drop, the green, blue and purple have ~3.7v drop, and the pink has a 3.3v drop. I want to wire all of these LEDs together into a total of 14 parallel circuits coming off of one series circuit. Each parallel circuit will have 5 LEDs of the same color. So there will be 2 parallel circuits of 5 red LEDs, 2 parrallel circuits of Orange LEDs, etc.

I would like to power the LEDs with 9 volt batteries. I am not 100% sure how many I need to get an appropriate voltage to power all of the LEDs. That is the first thing I could use a hand on.

I also have a handful of 200 ohm resistors. I would like to place resitors at the beginning of each parallel circuit so that each led in the circuit does not need its own resitor (I know that this is not the best way to do it if an led fails, but I am limited on resources and need this done semi quickly) I need to know how to calculate just how many 200 ohm resistors each parrallel circuit needs. The part that gets me confused is the different voltages for the different colors. I am not sure how to factor that in.

Thank you in advance! If any more information is needed, please let me know.

Edit: I could probably get away with 3.3 volts drop on the green, blue, purple, and pink so that they all have the same.

Each led takes ~25 ma


texts: If you plug in a bridge rectifier directly to a power outlet, and touching one of the outputs, isn't it like touching live wire?

texts: If you touch the output of the Full bridge Rectifier, and the circuit is powered directly from the city power, does it shock you with every positive wave of the 120ac? How about a half bridge rectifier? Its only one diode, but what happens if you touch the other end of the output, and how does this guy not get shocked:  https://www.youtube.com/watch?v=sI5Ftm1-jik (2:00),  and how does switched mode wall adapters isolate the live wire? This is so confusing!


texts: Soldering one PCB to another with 90 degrees angle

texts:
I want two PCB's to be soldered with each other in 90-degrees style.

I think that the base PCB should have a slot with the width equals to the top board thickness. The top board should have a flange with SMD pads. Looks simple:

Questions:

How do I calculate the slot width? Let's say the top board is 1.8mm thick with two 70 um copper layers. This will give me the total stack fhickness of 1.94 mm. Is it OK to mill the slot with 2mm cutter?
Should I make the slot plated or not? Or should I make the slot with "castellated" style edges to allow the solder flow through the slot?
Is there anything more I should think of doing things like that?

UPDATE

Forget to mention: I need these connections to withstand a lot of Amps. Like 30 or so.

Regarding the forces: I did not think about it. Moreover - I will have a heavy component on the top board (relay). So I can become a problem... Now I think that I could make additional fixtures on the top cover to prevent the top board from bending. However this is not a solution is the board will be soldered with an inclanation.


texts: If you have an I/O pin to protect, don't you always need the protection from both positive and negative ESD? I see that many circuits have clamping diodes connected between I/O nodes and power nodes. But only sometimes additional diodes are connected between the I/O nodes and ground. Is there a reason for not expecting negative ESD?


texts:
What are my options for video development? I am talking buying a development board, then translate that to custom pcbs and hardware.
With the rise of smart phones we have seen a plethora of hardware that can do video capure, and/or output to dispaly.

But there is not much documentation available on building your own systems.

The only options i know is the DaVinci SoC with the leopardboard for testing. But since it is a BGA package, it has problems to get your custom pcb.

I also know of the MCUCam5 which uses LPC4330.

Any experienced person in this domain to guide my through my development?
I wan to create an application that will record video from common cell phone cameras (through SPI or I2C) to SD card and dispaly on a colour display at the same time.


texts:
Ok, so I goofed... accidentally spec'd a 4mm footprint for a 3mm real-time-clock-calendar IC.

Rather than scrap these boards, I'm thinking of designing a double-sided PCB "adapter" to go from the 3mm to 4mm sizes, and sandwich this between the device and main PCB. Hand-reflow using hot air. Device is low power so no thermal conerns.

Has anyone tried SMT conversion like this? Envision any pitfalls? Anything to be aware of? Do I earn the "bodge of the year" award? :)


texts: How can I modify this circuit for some hysteresis and better design?

texts:
I need to make a circuit even when the push button pushed and released very fast, the final output will stay ON at 12V for roughly a second. %10 accuracy for the timing is fine. An LED will indicate the ON and OFF time. I tried to combine couple of circuits to obtain the goal.

Below circuit uses C1 and R4 for adjusting the pulse ON time. LM2903 is used as a comparator. The output of the comparator is buffered by a transistor buffer to obtain enough current to the load and the LED. The need for buffer is to obtain better results for different loads:

(left-click to enlarge)

And here is the voltage and current waveforms from the simulation for the nodes marked as n, p, op, out, LED current I(D1) and switch current I(S1):

My problem in this circuit I cannot add hysteresis. Because if I add positive feedback it will be connected to the RC timing circuit. I might overcome this by changing R4 but I cannot even create hysteresis by adding a resistor between the nodes out and p.

How can I add some hysteresis to this comparator without affecting the function of this circuit?
Is there anything fundamentally wrong or missing with this design?


texts:
I pulled an old PIC from the PIC24 family out of storage, probably last used about a year ago.  I reprogrammed the device with a bare minimum program.  It seems to work fine on all counts except that it pulls 55 mA from the Vdd pin and the current exits through Vss.  All other pins seem to draw current in the uA range.

No peripherals are enabled
Input pins are not floating
Output pins are not drawing current

This current draw is way out of specification for this device which should draw about 2mA.  What would cause such high current to be drawn on a device that is otherwise operating normally?


texts:
Hello fellow engineers

I have decided to solder busbars to a high current pcb  , but i have 2 concerns :

Does soldering a flat busbar (shown in left image) could cause thermal stress and deformation of the PCB , since i donot have the height to use busbar that work as pcb stiffeners also shown in second image.

Can i use a high temperature (ex. 350 degree C) paste or solder for the busbars , since after finishing this step the boards have to be sent to a small assembly shop for soldering the rest of the "small" components using standard re-flow process and I don't want the busbars to "fall off".

Additional info : board size is 140 x 100 mm , busbars are 90 x 30 x 1 mm. The current rating of the trace is 100A DC at 12v-24v . Using saturn calculator for 100A outer trace at 4oz copper you need a 60mm wide trace at 20 degree temperature rise , which consumes too much of board space.

any additional advice or ideas are more than welcome :)


texts: I'm planning to make an always on torrentbox, I get my internet from a 4g usb dongle modem, but I've very limited experience with such boards. From what I read on the internet, it seems BeagleBone is little bit more powerful and has an easier time setting up than Rpi, but it is slightly more expensive and I'm on a shoestring budget. Which board would better suited for my kind of project?


texts: How to filter/clamp/suppress positive voltage spikes from IC

texts:
I need to work with an IC or more specifically a PCB (RFID reader) that is feeding back positive voltage spikes into my supply line.

What is the generally accepted solution of isolating noisy IC's from feeding back into the supply line? Preferably up to the kHz range.

I read up on Capacitance multipliers, they should work really well with any droops from current draw but not with preventing positive spikes from the load.


texts: I don't understand the windings inside my power drill.

texts:
I was curious about how my power drill worked and I disassembled it. I understand the general principles at work here but I don't understand why the winding is set up this way.

I assume running current through the solenoid in the center induces a magnetic field and causes the motor to spin. I notice the wires go parallel the axis of rotation (I assume to align the field correctly) so I'm not sure if you still refer to this as a solenoid.

You can see there are 2 sets of winding. I am not sure why.

Not sure why the winding is configured this way either.

The trigger is a rheostat that goes from open -> ~15MOhm -> closed. The directional switch (not sure) I believe just changes which coil gets power. Since it's just AC and there's no AC-DC transformer I'm not sure how it would even matter which coil gets power since the field would presumably be flipping at the frequency of mains.


texts:
Having different types of capacitors (electrolytic, film, silicon, tantalum, etc.), which types would be the optimal choice for polar/non-polar pair in this common configuration:

I understand the reason for having two or more caps of different capacitance values. Though wonder, why does the pair includes a polar and a non-polar capacitor? Is it essential to include a polar capacitor, or it's OK to use two non-polar caps?

The application is for bypassing power supply for opAmps, ADCs, DACs, microcontrollers, and other low power ICs up to 100MHz bandwith. I know that electrolytic ones would be too big for surface mounting apps.


texts: Most efficient way to switch order in which data is read in assembly

texts:
I have an assembly assignment that requires me to be able to store a number and via a lookup table output the number on a 7 seg display in both forward and reverse order depending on the state of an input switch.
While it's not a requirement, I'd like to use the least number of cycles and code that I can and still follow good coding practices.

My current thinking is to store the number twice( once in either direction) and choose the starting memory address depending on the switch state. This way I only need one lookup routine that essentially reads either number in a fwd direction.

An alternative I have considered is to have two lookup routines. One that inc Z and one that decrements it. This has the obvious advantage of only requiring one stored number at the expense of additional lines of code.

Are either of these approaches acceptable or are there other methods I've not considered?

I tend to think the former is more effective but less flexible than the latter.


texts: Relation between diodes and laser diodes

texts:
I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5 Resistance, Resistivity, and Conductivity presents makes the following claim when discussing the concept of resistance:

  Ohm's law can be applied only to ohmic materials -- materials whose resistance remains constant over a range of voltages. Nonohmic materials, on the other hand, do not follow this pattern; they do not obey Ohm's law. For example, a diode is a device that allows current to pass easily when the voltage is positive, but prevents current flow (creates a high resistance) when the voltage is negative.

I'm wondering what, if any, relationship there is between this explanation of diodes and the laser diode? The explanation provided is obviously very basic, but how does it, if at all, contribute to the functioning of laser diodes?

I would greatly appreciate it if people would please take the time to clarify this.


texts: Is a snubber for transformer primary winding necessary?

texts:
When there is a inductor in the circuit and is being switched on and off it is necessary to put diode across that inductor to prevent high voltage overshoots.

simulate this circuit – Schematic created using CircuitLab

In case of AC voltage this diode protection is not possible and instead of that is used a snubber of some sort. Across the switch or switched load.

simulate this circuit

But what about primary side of transformers? It is a inductive load, right? Is a snubber required or recommended? All the circuits I found have no snubber. They all seem to be basically like this:

simulate this circuit

But there has to be some switch at the primary side. Should there be some RC snubber?


texts:
Im trying to control a temperature controller using Arduino MEGA over SoftwareSerial.

Im using Modbus-Master-Slave-for-Arduino library and I tried to test using example code below.
It gives only 0 for each item of the received data array au16data[].

Im using RS-485 serial transceiver module for interface to temperature controller and SoftwareSerial pins. But, There is no any pin definition for DE and RE pins. How can I connect A and B terminal of the controller to Arduino?

#include <ModbusRtu.h>
#include <SoftwareSerial.h>

// data array for modbus network sharing
uint16_t au16data[16];
uint8_t u8state;

/**
 *  Modbus object declaration
 *  u8id : node id = 0 for master, = 1..247 for slave
 *  u8serno : serial port (use 0 for Serial)
 *  u8txenpin : 0 for RS-232 and USB-FTDI
 *               or any pin number > 1 for RS-485
 */
Modbus master(0); // this is master and RS-232 or USB-FTDI via software serial

/**
 * This is an structe which contains a query to an slave device
 */
modbus_t telegram;

unsigned long u32wait;

SoftwareSerial mySerial(12, 13);//Create a SoftwareSerial object so that we can use software serial. Search "software serial" on Arduino.cc to find out more details.

void setup() {
  Serial.begin(9600);//use the hardware serial if you want to connect to your computer via usb cable, etc.
  master.begin( &mySerial, 9600 ); // begin the ModBus object. The first parameter is the address of your SoftwareSerial address. Do not forget the "&". 9600 means baud-rate at 9600
  master.setTimeOut( 2000 ); // if there is no answer in 2000 ms, roll over
  u32wait = millis() + 1000;
  u8state = 0;
}

void loop() {
  switch( u8state ) {
  case 0:
    if (millis() > u32wait) u8state++; // wait state
    break;
  case 1:
    telegram.u8id = 0x01; // slave address
    telegram.u8fct = 0x04; // function code (this one is registers read)
    telegram.u16RegAdd = 0x03E8; // start address in slave
    telegram.u16CoilsNo = 0x01; // number of elements (coils or registers) to read
    telegram.au16reg = au16data; // pointer to a memory array in the Arduino

    master.query( telegram ); // send query (only once)
    u8state++;
    break;
  case 2:
    master.poll(); // check incoming messages
    if (master.getState() == COM_IDLE) {
      u8state = 0;
      u32wait = millis() + 2000;
        Serial.println(au16data[0]);//Or do something else!
        Serial.println(au16data[1]);//Or do something else!
        Serial.println(au16data[2]);//Or do something else!
        Serial.println(au16data[3]);//Or do something else!
        Serial.println(au16data[4]);//Or do something else!
        Serial.println(au16data[5]);//Or do something else!
        Serial.println(au16data[6]);//Or do something else!
        Serial.println(au16data[7]);//Or do something else!
        Serial.println(au16data[8]);//Or do something else!
        Serial.println(au16data[9]);//Or do something else!
        Serial.println(au16data[10]);//Or do something else!
        Serial.println(au16data[11]);//Or do something else!
        Serial.println(au16data[12]);//Or do something else!
        Serial.println(au16data[13]);//Or do something else!
        Serial.println(au16data[14]);//Or do something else!
        Serial.println(au16data[15]);//Or do something else!
    }
    break;
  }
}


texts: What type of oscillator is this? (Theremin Project. Variable Pitch / LC Oscillator)

texts:
I found this oscillator at a Theremin project pdf. I simulated the circuit, and found that the output (left wire) oscillates at 236.5 kHz.

This circuit is referred to as "Variable Pitch Oscillator", but that doesn't seem to be the best reference for it.

So I'm wondering: what circuit is this, and how do I calculate the oscillation frequency??


texts: I am trying to supply 5V 3amps to my breadboard. I have an 18AWGX2C wire but it is too thick to simply connect into the breadboard inputs. Is there any way for me to connect these cables (PWR and GND) into the breadboard?


texts: Wire soil moisture sensor such that it only powered when measuring

texts:
I am a rookie electronics tinkerer who wants to use the SparkFun soil moisture sensor. I plan on connecting it to ADC MCP3008 to the GPIO pins on a Raspberry Pi. On the SparkFun site the vendor warns that the quality of the sensor may degrade fast if the power is left on continuously. I understand that I need to use a transistor to regulate the power to sensor but I am not sure which one I would need and how I can best connect it to the Raspberry Pi.

I came up with the following design with a BC548 transistor. Could someone give me feedback whether:

this is the right wiring
I need resistors

simulate this circuit – Schematic created using CircuitLab


texts: What is the purpose of the 250uF capacitor in the LM386 circuit?

texts:
The basic amplification schematics shown in the LM386 datasheet shows a 250 uF capacitor in series with the output. I don't have any 250 uF, but I do have plenty of 470uF. If I understand correctly, is this capacitor used as a high pass filter, so should I be able to use a 470 uF instead of a 250 uF?

Also, is the resistor (10 ohm) and capacitor (0.05 uF) going to ground a low pass filter?


texts: Ultrasonic transducer for fish finder - TD02002

texts:
I am looking to construct an MCU based ultrasonic fish finder.  I have found a potential component that is a transducer called the TD02002 which can be found here:

http://www.chinaultrasound.com/index.php/200khz-ultrasonic-transducer-for-depth-measurement/

Unfortunately, try as I might, I haven't found any data sheets on how it might be used

http://www.chinaultrasound.com/index.php/200khz-ultrasonic-transducer-for-for-depth-measurement/

It has a phono type plug on its cabling.  I am at a loss on how to drive it.  Does anyone have any source materials or circuits for building fish finders?  Ive performed an evenings worth of Google searches but come up dry.

Update: The supplier sent me a datasheet ... but I am still lost on how to drive it:

Datasheet


texts: LED s calculation of beam area, dosage and energy from data sheet information

texts:
I have an application with LEDs with following data sheet

LED631E    635 nm
optical power 4 mW
half angle    20°
FWHMa   10 nm,

Could you help me with calculation of beam area at the distance of 20 mm from LED?

Also please help me with calculation of dosage (J/cm2) and total energy delivered [Joules] in 20 minutes at the same distance : 20 mm from LED.

Thank you a lot.


texts: A question on using shield wire for single-ended transmission with CAT6 cable

texts:
My question is very hard to put in words therefore sorry for using six photos along with the details.

For investigating a noise issue when using a sensor with a CAT6 cable for single ended signals, I use a 9V battery as a floating source with 100 Ohm output impedance as below.

Since the receiving ADC daq system is also floating, I use a scope isolated from earth.

Below is how I first hook up the source output to the CAT6 cable:

Now at the receiving end (where the end of CAT6 and scope probe meet) I do wiring this way(CT6 shield wire is not connected to anywhere):

And here is what I see as noise in AC coupled view:

But if I wire the scope probe this way(cable shield is connected to ground of the scope):

The noise reduces significantly as below:

My question is:

1) Why is the noise attenuated?

2) Is it okay to wire the shield of CAT6 to GND of the sensors in receiving end as in my second way to mitigate noise? Is it okay if both sides are not earth grounded?


texts:
My Lumia 535 claims, that leaving my WiFi connection turned on can save the battery.

How can that be true?

I'm a layman, if not ignorant to this area of expertise, but from what I was always told comes assumptions, that:

WiFi uses separate antennae, not used by any other technology, so turning it on causes device to power up another antennae and thus consumes more energy,
Turning any wireless technology (WiFi, GPS, GPRS), when there is no connection to the destination or signal strength is very weak, consumes even more energy.

Since mobile devices are quite often used outside building and in other kind of areas with no or very poor WiFi coverage, leaving WiFi turned on all the time should in my opinion drain the battery like a hell. What am I missing?

Note: This question is general to WiFi or even general to wireless technology, so I assume, it can be asked here.


texts: Can an Adjustable Circuit Breaker be adjusted while Energized?

texts:
For a Low Voltage Circuit Breaker, such as the Legrand DPX3 630, 3x400A, 36kA, 400V, we have adjustment dials to change the properties of the magnetic (Magnetic adjustable from 5 to 10 In) and or thermal (Thermal adjustable from 0.8 to 1 In) trip curve.

In practice this normally don't happen, but, Should be any damage risk to the breaker to change those adjustments while the equipment is energized?


texts: Finding/figuring out pin configuration on undocumented components

texts:
I recently purchased an assorted set of LCD/LED displays, and inside there were a set of components which I cannot find a datasheet for upon googling the component number.

For instance in the component below:

I have googled what appears to be the serial number: HNM-05SS62T, but I cannot find a datasheet for this component. Also, googling Samsung SSED doesn't appear to yield any better results.

How do you go about identifying how to use a component like this in this case?


texts:
This is something that has bothered me for ages. I wasn't sure it could be made up as a question here, until Olin Lathrop suggested it to me in a comment to another thread.

We all know what we are talking about when someone mentions, for example, an 1N4007 or 1N4148 diode. The first is a general purpose rectifier with 1A max forward current and 1000V max reverse voltage, just to be explicit. And this information is completely independent from the manufacturer of the specimen we have at hand (I'll bet anyone with a bit of experience in EE would go crazy if he saw, say, a DIAC labeled as 1N4007 produced by a reputable manufacturer).

So we know there are "standard" part numbers which corresponds to devices with well-known characteristics. As Olin pointed out in that answer to the question in the thread I mentioned above, although we all know what a standard part is, sometimes different manufacturers give slightly different specs for the same part. Still, an 1N4007 is an 1N4007, this little differences notwithstanding!

So my question is, what defines what a standard part actually is? Historical reasons (the first manufacturer got the part number; second sourcing the part to others made that part a de-facto standard)? Industrial agreements (some manufacturers decided it would be good not to do cutthroat competition on low-tech parts, so they decided to standardize)? Official standardization organizations (Olin mentioned JEDEC in that comment; may it be some other institution as well)?

To really gild the lily the answer should also provide references to possible official documentation about common parts or procedures (if they exist) to standardize a part.


texts: Is capacitor reactance [sometimes] defined with negative sign?

texts:
Wikipedia currently claims so

but I've looked in 6 books via Google Books and it's not defined like that, i.e. it's just

$$ X_c = \frac{1}{\omega C} = \frac{1}{2\pi f C} $$

Is Wikipedia full of nonsense on this, is that just a fringe def, or somehow all six books I've checked via GB just happen to contradict that and some EE bible actually defines it with a minus sign like that? Wikipedia cites one book and one unverifiable website; I can't access that book right now. The ones I've checked: 1 2 3 4 5 6. Note that depending on your Google luck you may not be able to see all of these. And I've checked the 3rd ed. of the Art of Electronics by H&H; it also gives it the positive way (on p. 42).

I was actually able to verify a newer edition of the textbook cited in Wikipedia, and indeed it defines it that way with a negative sign. So I'm guessing it's one of those egg-end issues. Still I'm curious if there are any EE standards (IEC etc.) that take a stance on this. Perhaps someone knows...

I've accepted Adams' answer as good enough (and I've fixed Wikipedia too), however if someone knows more about IEC, IEEE or whatever other standard bodies might have said about this, please contribute...

And form the Wikiality department, that article has changed quite a few times it seems; back in March it gave the positive definition.


texts: How can we make LoRaWAN work in Real World

texts:
Today, there are many competitive IoT providers and technologies initiated by many organisations across the world. Sigfox and LoRa Alliance I believe are in the top of the competition line but, please feel to correct me if I am wrong. However, these companies are limited by theories expressed in wireless communication and all unknown physical laws. I think its fair for me to divide wireless communication into two segments; Wide-band and Narrow-band for the sake of my question.

I recently stumbled upon this document by TI which explains why Narrow Band is the De-Facto Standard for IoT.

http://www.mouser.com/pdfdocs/TI-Long-range-RF-communication.pdf

The above document make it sound like, rather prove, that future IoT communication solutions that use large number of nodes should use minimum bandwidths possible. They highlight the fact that "co-existance" can only be achieved through Narrow-band. This makes me wonder how LoraWAN achieves the same as it goes without argument that any IoT technology that doesn't support co-existance is of no use in future. I know that LoRAWAN protocol limits the number of transmissions done through a unit node by setting a limit of the daily quota. I ( I hope you too) see that on its own is not sufficient to support co-existence of thousands of nodes.

As I learnt, LoRaWAN/LoRa PHY does not use Narrowband technology but uses a modulation technique called Spread Spectrum which utilizes a higher bandwidth. I believe this limits the total number of nodes that can transmit at the same time within a given spectrum(e.g. the ISM band). At the same time, radios that utilize narrow-band technologies can support  higher number of simultaneous transmissions using the same spectrum.

I an keen to know how LoRA would support co-existence in future applications in situations where few thousands of nodes involved.

I would also like to know the possible outcomes when two LoRa nodes transmit at the same frequency at the same time from the same place with exact same power. Would data get corrupted?

I also know that the people who invented LoRA are way better at wireless technologies than I am. Hence, I would like to know what possible reasons may have caused them to stick to Spread Spectrum technology rather than narrow band. Or did they do a mistake?

Thanks for your help.


texts:
I have a 240V relay that uses a 120VAC coil.  When I switch power to the coil, the relay makes a faint humming sound.  It isn't very loud, and sounds like a transformer almost.  A normal speaking voice or small fan in the room is enough to drown it out, to give you an idea of the volume.

To be clear, this isn't a situation where the coil isn't getting enough power and contacts open and close rapidly (described as "buzz" in other questions).  I have verified that the voltage is correct, and I have observed that the armature is still (not vibrating) when the coil is getting power.

So I am wondering if I have a bad relay, or if this is normal for AC relays, which I haven't used before.  I am used to 12VDC relays for the record.


texts: Ringing issue on I2C FM+ bus between MCU and few sensors - Power supply issue?

texts:
I'm experiencing some issues while probing a problematic I2C bus on the oscilloscope.

We want to interface several TLV493D-A1B6, with a STM32L4 (we are working as well on STM32F4 and have the same issues).

The STM32L4 has 4 I2C FM+ (1Mbit/s) bus. We want to use the 4 of them in order to communicate with a total of 12-16 sensors, hence 3-4 sensors per bus.

We achieved 4 sensors on the same bus as well as having 1 sensor on each one of the 4 bus.

However, we are not able to interface more sensors (i.e. 4 sensors on 4 bus or even 1 sensor on 3 bus and 2 sensors on the 4th bus). Some bus starts and continue working, some other don't start, some start and stop after couple of seconds, these behaviours being random.

While probing the bus on the oscilloscope I noticed what looks like heavy ringing when SCL (or SDA) goes from HIGH to LOW and I am wondering if it can be the source of the problem. Here you can see
this ringing on the SCL line :

As you can notice, the ringing seems to be less important on the second picture. It has been taken the day after the first one, in a seperate room (different outlet for the oscilloscope) and while the first pic shows the signal with one sensor on the bus, the second one depicts the signal with 3 sensors on the bus.

Some information on the I2C bus:

Frequency : 1 Mbit/s
Capacitance : the capacitance of the bus has been determined by measuring the rising time of the signals. It has been determined that one bus has a capacitance ranging from 50 pF for one sensor to 100 pF for 3 sensors.
Pull-up resistors : 1,2 kOhms (other values have been tried, ranging from 600 Ohms to 2,2 kOhms. Lowering the value seems to improve a bit but the timing has been checked and 1,2k seems correct).
Termination : 33 Ohm series resistors have been used on each line.
Power supply : several power supply schemes has been tried for the sensors including an isolated bench power supply or the same power supply as the MCU.
The I2C lines run through relatively short cables and bread board. The capacicance has been checked and it's apparently not the source of our problem.

I am not the one responsible for the firmware but I do know that we are using DMA on the MCU in order to have 4 I2C FM+ running at the same time.

Some ideas we had but we can't clarify :

The increasing number of sensors is responsible for a over usage of the power supply.
The ringing comes from bad probing and is not happening when the the signals are not probed. It has been noticed that probing the signal usually leads to worst results.

Does anybody have already experienced a similar behaviour with I2C and/or does anybody have any idea to improve our set up ?

Again, what sounds strange to me is that the set up works with 4 sensors on 1 bus, it works as well with 4 sensors on 4 different busses but we are stuck when trying to go further, the goal being 12-16 sensors on the 4 bus.

PS : I can't post a schematics of our set up right now but I'll edit my post as soon as I can.


texts: Current sense op-amp with integrated shunt vs expensive resistor

texts:
To simplify my question lets assume:

I need to convert +/-7.07A RMS AC current into +/-707mV RMS voltage with high acurracy (0.1% or better).

It may be also higher voltage, up to +/-2.5Vpk.

For now I just measure voltage on Ohmite 15FR100E resistor:

100mOhm
90PPM/°C
35°C/W
5W

When I'm trying to measure 5A RMS current It probably heats up by about 87.5°C (calculated from thermal resistance and power) and that gives about 0.788% resistance change (calculated: 87.5°C * 90PPM/°C).

I want to improve this and I'm thinking about two options:

OPTION 1. Use expensive resistor: Powertron FPR 4-T221 0R100 S 1% Q

100mOhm
25PPM/°C
4.8°C/W
3°C/W heatsink
15W
4-terminal

And this should give me 0.024% resistance change (from 5A RMS).

OPTION 2. Use INA250 current sense amplifier with fixed gain and integrated 2mOhm shunt.

INA250 op amp features from datasheet:

I think, that I can assume

I can forgot about thermal problems because shunt R is very small
I can compensate 0.3% gain error
If I pick 200mV/A version - I'll get 2x higher voltage vs my shunt and this is fine

But I'm not sure about (QUESTIONS):

Can I just ignore 50mA offset error (this is ~0,7% of my 7.07A peak current) when I need to measure sine RMS acurrately?
should I expect some extra sources of errors when I replace shunt with INA250?
is this that simple? really? $4 op-amp replaces big expensive shunt just like that?

Attachments:

Cheap Ohmite resistor which I'm using now:

Expensive Powertron resistor:

If someone asks why I'm not using resistor like 10mOhm to reduce heat - the answer is because I tried to avoid 10x gain op-amp in circuit, that would be extra source of errors. Maybe I was wrong. Actually this is not about measurements, I'm building current source similar to this:

http://www.kswichit.com/VCCS/vccs.htm


texts: Is it possible to use ethernet communication between MCUs without using a hub or switch?

texts:
Is it possible to connect some MCUs together in a star topology, without using any hub or switch?
EDIT: There will be a main MCU in the star topology and it will be receiving 2 different GPS datas (From 2 other MCU's). There will be POE coming to the main MCU also. This main MCU will be sending those GPS datas to another two MCU's. All the communication will be done with ethernet. This is the network roughly.
I was thinking using splitter for POE data coming to the Main MCU and using the data of it only. 10 Mbit communication speed will be enough, the events are not that time crucial. However, for designing the circuit what kind of components I will need for the main MCU PCB. I thought there must be a transceiver but then I saw that switches also do the job of the transceivers. There will be no internet connection in the network. So I thought maybe without switches or hubs that might be possible.
Edit 2: Looks like it is doable with only using an ethernet connector.


texts: Seeking recommendation for capacitor to handle high pulse current

texts:
I'm seeking recommendations for an inexpensive capacitor that will handle fairly-large pulse currents.  Maximum voltage is 15 Vdc applied to the capacitor and I'd like to see current pulses in the 100A range if possible.

I will increase the supply voltage if necessary.

Expected pulse width is determined by the total circuit resistance and is expected to be less than 20us.  Repetition rate is about 500 Hz.

My current setup is using a IRF540 MOSFET (RDSon 44 milliOhms max) and a 2u2 250V MKT film capacitor from Epcos (TDK) discharging into a total resistance of less than 0.2 Ohms.  Gate drive is about 12V with rise time better than 100ns and fall time better than 200ns.

This current setup is giving me a peak current somewhat more than 20 A and the film capacitor is running slightly above ambient temperature.

I can go to a much better MOSFET but I think that my main limiting factor is the capacitor.

My gut tells me that a ceramic capacitor is going to give me better results than the film capacitor.  Question is: Which ceramic capacitor?

Or is there a better capacitor choice that I should be exploring?


texts: Ethernet: distance from PHY to magnetics

texts:
I am confused as to the preferred placement of Ethernet PHY and magnetics. I thought that in general, the closer the better. But then SMSC/Microchip app note (http://ww1.microchip.com/downloads/en/AppNotes/en562744.pdf) says:

  SMSC recommends a distance between the LAN950x and the magnetics of 1.0” at a minimum and 3.0” at a maximum.

Confusingly enough, earlier in the same paragraph one can read:

  Ideally, the LAN device should then be placed as close as possible to the magnetics.

I used the excellent LANcheck service from Microchip and the expert reviewing my design also suggested that a minimum of 1" separation between the chip and magnetics is suggested to minimize EMI.

I do not understand why increasing the distance the signals have to travel would ever minimize EMI?

Also, a related question — I do not understand reasons for the following:

  To maximize ESD performance, the designer should consider selecting a discrete transformer as opposed to an integrated magnetic/RJ45 module. This may simplify routing and allow greater separation in the Ethernet front end to enhance ESD/susceptibility performance.

Intuitively, magnetics that are embedded inside a shielded RJ45 module should be a better solution than discrete components with traces inbetween?

So, to summarize:

should I try to maintain a minimum distance between the PHY and magnetics or should they be placed as close as possible?
is it better to use a "magjack" or separate magnetics and RJ45 jack?


texts: Creating a low (90-250F) temperature-controlled soldering iron (or modifying a higher temp one to get lower temps)

texts:
I'm a wax sculptor and am interested in getting a temperature controlled soldering iron but I need a very low temperature range (like 100-250F). Most units come with a bottom end of 350F+. Is there a way to open up and modify one of these units easily or is it all pre-programmed in? I don't need the digital readout to report the correct temperature after any modifications but I do need the temperature control to be in-tact and working.

If it's not practical is there any way to modify a non-temperature controlled to be able to get such a range without resorting to programming some chip. I know I'd have to add in a thermocouple in or on the outside of the shaft but I wasn't sure if there are ready-to-go circuits or devices that will switch on/off the device to maintain a temperature based on a thermocouple unit.

(Actually, I have one of these right now but it's in the wrong temperature range and would be way too clunky as it's an external thermostat that does up to 108F for heating pads for plants, and I could i suppose weld the the probe of it onto the shaft of my soldering iron, if it did the right temperature range, but that'd be pretty inelegant).

Thanks!


texts: How to chose the right decoupling/bypass capacitor variant for opAmp power rails?

texts:
Many experts here recommend 100nF bypass caps to the power rails of an op-amp.
I made it a tradition myself that when I use any op-amp I always use 100nF decoupling cap from +Vcc to GND and -Vcc to GND.

But I also see different variants as below examples:

As you see above examples do not just use 100nF at the power rails but either RC like lowpass filters or two caps in parallel.

Does that matter which variant I use for the power rails for decoupling?
Is there a principle or rule of thumb? What should be the criteria?

Note: This is a question specifically only about bypass caps at power rails of an op-amp. I couldn't find a specific satisfactory answer at related questions.


texts: Regarding Multiplexing and Multiple Access

texts: Is Time Division Multiplexing and Time Division Multiple Access same if not what is the difference between them? Similarly between FDM and FDMA.


texts:
I am Nikhil from India, working as an embedded programmer. I made half inch 7segment display based digital clock. But after few months few 7segment displays got damaged. I got same complaints in many boards. Please help me to debug the error.

5v dc power supply is used.Pic16f877a is used for controlling.74hc164 is the shift register ic used.

Bd140 transistor is used for on/off 7segment display.

5v is connected to the emitter of bd140.

Base is connected to pic microcontroller via resistor.Collector is connected to common anode of 7segment display.Cathode pins are connected to 74hc164 via current limiting resistors.

I think this is the recommended connecting method. But around 1/10th of the total segments used are getting damaged within few months.

I used 560e as current limiting resistor and increased its value upto 2k2, but no change only brightness is getting down.


texts: A question on Thevenin and output impedance

texts:
Above figure shows the transformation of a circuit to its Thevenin equivalent. Imagine this is a power supply and A is the + terminal.

In reality the real circuit  model is the one on the left side and just before the A terminal I circled the resistance with red color.

On the right side is its Thevenin equivalent and the Thevenin resistance is circled with green color.

I have the following questions:

1-) When one talks about the "output impedance" of this power supply, would you understand the red or green circled resistor?

2-) Lets say you don't know what lies inside the black box. You can measure the Thevenin voltage across A and B terminals by a voltmeter. But is it also possible to quantify the Thevenin resistance Rth(for example by shorting A and B)?


texts: Converting battery capacity from Ah to Wh: Which voltage should be used?

texts:
I need to convert the battery capacity from ampere-hours to be Watt hours.
I know that \$P=VI\$ in Watts, however I'm unsure of which voltage I will need to use in order to use this relation; there seem to be a lot of different voltages listed in battery data sheet.
For example, with these batteries (Sunica+) the following specs are listed in the data sheets, and these are just some of many related to voltage:

float 1.5 V/cell
boast 1.6 V/cell
battery system 12/24/48 V
Nominal Capacity 120 - 1.0 V Ah
final voltage 1.14-1.20 V
...

So to someone fairly inexperienced in the technical aspects of batteries, simply saying 'V*mAh/1000' is fairly meaningless. Should you use the battery system (12/24 etc) or is it one of the others times the number of cells, or none of these?
Thanks for the help


texts:
Can I get 18V from two 9V batteries if I join two together?

How will I join them?


texts: Create assembly variant with a script in Altium

texts: Is there any way to define a new assembly variant using scripting language? I can see that there are some variant-related procedures in IProjectInterface, however none of them seems to be dedicated to new variant definition.


texts: I want to power some hobby servos from a USB 5V supply. I am daisy chaining 2 ports together from a powered hub so that I can draw up to 1A. Should I power the servos directly from this supply, or is there some kind of simple protection circuit that I should add between servos and USB supply to prevent accidental damage to the hub?


texts: Why is MSP430's Stack Poniter(SP) always alligned to even address?

texts:
While I was reading through the MSP430's User's guide, I came to know that its stack  pointer is alligned to even address. (Read Pg.189 of http://www.ti.com/lit/ug/slau208m/slau208m.pdf)

Why is it so ? Why is the stack pointer alligned to even address?

As per my understanding, each address location in RAM can store 16bits of data irrespective of even or off address location.

From the below image it is clear how that data can be pushed or popped in RAM.

Now it is like each address(even or odd) can store 8 bits of data. But I expected each address can store 16bits of data.


texts: Ripple Current in Boost Converter for Nixies

texts:
I'm trying to design a power supply for 6 IN-8 Nixie Tubes (driven individually, not multiplexed). Each tube has a current draw of 2.5-4.5mA, so they pull around 30mA(max) total. The input voltages is 12V and the output voltage should be 180V. Switching frequency should be around 100kHz (10uS for each cycle).

Using \$Volt = (Henries*Amps)/time\$ from this question, I found the inductance to be around 400uH (\$(12V*0.00001s)/0.03A\$). However, I calculated the inductor ripple current from this IC boost converter pdf (equation 2) and got a ripple current value of 285mA (\$(12V*0.95)/(100000Hz*0.0004H)\$).

These calculations lead me to a series of questions:

As per their datasheet, Nixie tubes can't exceed 4.5mA. Any more
current will affect their lifespan. However, my understanding of
loads is that they will only draw as much current as they need. When
drawing current from the power supply, will the Nixies draw only
their needed current? Or their needed current \$\pm\$ the inductor
ripple current?
Is it possible to create more ripple current than the output current? Assuming its not:

What is the correct way to calculate ripple current?
Is it typical for ripple current to be larger (for an average load of 30mA) in a boost converter operating in CCM or DCM?

Schematic edit (where the switch should function like an ideal mosfet):


texts: How do I take proper voltage measurements on device with multiple voltage sources sharing the same ground?

texts:
If you recognize me, it's in reference to CRT scopes again. I don't understand how to take proper voltage readings on the circuits. An example is the heating element in the CRT. When I hook both test leads to both pins of the election gun, I get the proper 6.4V reading. However, when my negative lead is hooked to chassis (HV probe) each pin going to the electron gun measures at over 1KV.

I'm confused as to how 30V can share the same ground as 1500V in the first place, but what do I need to know to choose which negative side to probe with? The manual for my HV probe tells me to hook the ground lead to the chassis, but in the case of the election gun, that makes it look like the electron gun is receiving over 1KV, which I know is incorrect because it's glowing nicely instead of bursting into flames. I guess the other possibility is to test components directly instead of only testing it's positive and using the chassis. Do I sometimes ground to chassis, and sometimes ground on the individual component?

Thanks again for all the help


texts: Is this a reasonable, robust way for detecting voltage crossing a threshold?

texts:
Updated, functional design at the bottom of this question

I wish to detect when a low-impedance signal is below or above 60VDC (±3V). When the signal is above 60V, I'd like to indicate this by illuminating an LED and opening a relay. Else, illuminate another LED and close the relay.

To do this I propose to use a the following comparator circuit. This is my best attempt - I've made functional blocks and connected them together as best as I can see. Is it a reasonable design?

Here is my justification for each part of the circuit:

HV is the a low-impedance 0-200VDC signal which is divided by 20, so that when HV=60V, the inverting input at the comparator should be approx 3V. Multiple resistors are used within the voltage divider to ensure manageable voltages across each resistor.
A reference voltage of 3.0V is applied to the noninverting input.

When HV < 60V, the comparator output should be high, which drives the relay through Q1, and illuminates D2.
When HV > 60V, the comparator output should be low, which de-energises the relay and illuminates D4.

The comparator output is an open-collector, so R8 acts as a pullup.

The 12V zener at the inverting input is included to provide transient protection.

I have not included input-offset adjustment because this circuit should not be user-adjustable. I've picked a comparator with acceptably low input offset voltage and high accuracy is not a concern.

R6, R7 and C3 seem to be best-practice inclusions - I haven't done this before but I think they eliminate oscillation of the output caused by capacitive coupling between output and input. I've included these components provisionally but may decide against them.

I've avoided adding positive feedback for hysteresis because I'm having trouble including it without shifting the switching thresholds (drastically). Since this circuit is for a visual indicator only, I'm not overly concerned if the output chatters about the switching threshold - HV should never be steady close to 60V. If there is a painless way to add a few tens-of-millivolts hysteresis, I'd love to hear it. I've considered just adding some small capacitance to the output.

Side note:
I'm acutely aware there's probably a very elegant means of doing this with a high-voltage linear regulator referenced by zener diode - a huge advantage there would be the ability to change the trigger voltage by changing only the zener - and doing away with voltage divider and comparator entirely. I don't have the analog-confidence to venture into that realm, but if you have any thoughts I'd love to hear them.

EDIT - an updated design

Thanks for your feedback everyone.
Based off feedback from commentors I arrived with the following design. It performs acceptably when constructed and tested - VHI:62V, VLO:59V. The circuit is basically the same as the first proposed, but with a modified output-circuit. I'm more comfortable with voltage controlled devices like MOSFETs so they were used instead of BJTs. A comparator with reasonably low input-offset was selected to make this a build-and-forget design. It should not be necessary to tune the circuit.

There are plenty of undesirable failure modes - I'm aware. Read the full writeup on the readme.