texts: Optimising a single pulse precision peak amplitude detector

texts:
So I made this precision peak detector circuit (with reference from EEVblog's video and experimenting with the resistor/capacitor values), with which I want to measure the peak amplitude of a single pulse of width 5us (50ns each rise/fall time at best and 155ns/90ns rise/fall time at worst) and the amplitude is variable and can be within 3mV to 3V. I would like the peak-detector to hold the voltage level for a sufficient amount of time (in this case around 60ms, although I have simulated up to 3s with the same result) without degrading the voltage level too much (a maximum of 1-2mV degradation over 60ms is acceptable for me).
So the result of the above circuit looks good in the simulation. When testing for the extremes I see the following (pics below). Here Green is the final output (voltage at R2), Red is D2 current(essentially to show the peak current the opamp can handle), Blue is the input pulse (V1):

For 3mV pulse, here are the results:

As, you can see there is a slight offset of around 0.6mV, which is acceptable for me as long it is fairly constant over all my measurements.

For 3V pulse, here are the results:

Here the peak current in diode D2 (or as I think is a measure of maximum current required from the opamp (U1) is around 79.6mA which is right below LTC6268-10's typical peak output current rating of 80mA.

R2 is basically modeling the input impedance of an ADC which I'll directly connect at the output of U2. I chose LTC6268-10 because of its low input bias current which 'should' help the capacitor to retain the voltage (in this double diode configuration as per the video) for a long time. I would also be using a low leakage analog switch/mux to discharge the capacitor (short it to ground) after I sample it using my ADC.
I need to be as sure as possible that this circuit would work as in simulation (or at least, close enough) before I put it in a PCB.
So my questions are:

Do you find any obvious mistakes that I am making here with my component selection (or their values) or the circuit itself? or do you suggest a better circuit to achieve my goal (of measuring peak voltages of a single pulse with an ADC)?

In the simulation the capacitor is holding the voltage very very well, which is good but I am thinking if there are any other ways the capacitor could get discharged (in the real world), and what should I take into consideration? Is there a specific type of capacitor, I should go for?

Is there a ready-made peak detector IC available already that would perform better than this circuit? I am not looking for S/H IC because I would require precise trigger timing to sample at the middle of the pulse.

Since I'll be using SMD components, if you would like, you may suggest anything important that I need to know regarding using SMD diodes, capacitors, etc for this particular circuit.

Side note: If the requirements are too high then I may be inclined to reduce the hold time (currently 60ms) to 6ms depending on the suggestions if that results in a simple circuit.
Thank you so much for reading my post.


texts:
I am trying to learn signal processing and digital pre-distortion.

http://www.altera.com/end-markets/wireless/advanced-dsp/predistortion/wir-digital-predistortion.html

I am currently trying to auto correlate the input signal and from this I make a matrix.  I then get the coefficients for this matrix and use them with a LUT to help pre-distort the signal. I am having difficulty understanding what these coefficients represent?  Why are they useful when added to the LUT? So the coefficients are used as a weight in those LUTs. Can anyone give me a pointer?

Same goes for the cross-correlation with the feedback, what do the coefficients from that vector represent?


texts: Can wet-cell and gel-cell batteries be mixed?

texts:
Given the same power ratings, can a (lead-acid/deep-cycle) gel-cell battery be paired together with a wet-cell battery in use?

For example, with a motorized/electric wheelchair, would one be able to use both a gel-cell and wet-cell battery concurrently in the chair?


texts: Question about the Karnaugh maps and the number of solutions

texts:
I'm given the K-map \$\sum_{(w,x,y,z)}0,2,4,5,10,12,15\$ and was able to reduce it down to \$\overline y\space \overline z+\overline w x \overline y +wxy+\overline x\space \overline z \$

However, it says that there are two solutions. My question is what exactly does it mean to be a minimum expression? Also, what would the other "solution" be? It seems there are as many as 4+ perfectly valid expressions that would have the same number of terms. How do I know I chose the right solution?


texts: Using Bessel function graph to finde out side bands

texts:
If I am not wrong, using Bessel function we can estimate the side bands of a carrier? Is this correct? If so, what are the steps to find these values from the graph?

For example if modulation index is 2 and amplitude of the signal is 2volt what are the first few side bands?


texts:
As far as simulation goes, I can handle ngspice interactive simulator to validate an design.
But there are cases where I need to format the plot, chart or whatever is required by a design report.
So, what is the comunity using for post-procesing ngspice results, and what output format to use, how to import the data?


texts:
In my module I am taking two input 8-bits.

mymodule(input clk, input [7:0] AS_1,input [7:0] AS_2, output [7:0] AS)

Now I want to create a container that will keep both inputs, I mean I want to join them in a single one. I want to do something like that:

reg [15:0] JOIN = AS_1 and AS_2 ---> all their bits should be arranged in a single container

But I don't know whether it should be a reg type or wire or something else, because I'll need to make other operations with that JOIN

Any help, advise or suggestion would be highly appreciated!!!


texts: Replace Thermistor with Thermocouple in a circuit

texts:
I had a simple temperature controlling relay board (Novus N321). It would open or close a circuit powering a heater based on the reading of a thermocouple, versus a set value. The circuit is now broken. I was browsing replacements and saw a really cheap one (W1209), however, that one employs a thermistor (an "NTC sensor"). And I would prefer to keep using my thermocouple.

Is it possible to simply replace its thermistor with the thermocouple?

If not, how worthwhile would it be to adapt the new circuit to the thermocouple?  Note that in my country a replacement for the original is about $75, and the cheaper one is $5. Also, I have almost no knowledge or experience in electronics.


texts: On/Off toggle with delay using bi-color led

texts:
I need to design a circuit so that when a button is pressed, the red LED  lights and starts an activate delay circuit so that when capacitor C2 (100uF) is charged it turns  the red LED OFF and green LED on.

I tried this in a simulator and it's working fine, but i would like not to use two led diodes, just one bi-color red/green LED. What do I need to add to circuit to make it simple as is and to acheive above idea? (On toggles RED on, after capacitor in delay circuit is charged, turns off RED, and turn green ON.

Here is schematic:


texts: How do you compute a product machine from two finite state machine transition tables?

texts:
I have been asked to show 2 Finite State Machines are equivalent by computing the product machine of both.  Below is an image of 2 transition tables corresponding to 2 Finite State Machines.

How do I construct the product machine of both of them?

Both FSMs have an initial state of A.  So my understanding is you start at A and feed an input of 0 and see where both machines take you.  In this case, starting at A with input of 0 takes you to D for the left transition table and outputs 0.  Starting at A with input of 0 takes you to B for the right transition table and outputs 0.  Isn't this a counter-example immediately (i.e. both of these FSMs are not equivalent)?

But for some reason the problem is stated in such a way that I need to prove they are equivalent.  So I"m a little confused, is the problem stated incorrectly or are these two machines really equivalent?


texts: what does it mean for a to BJT operating at the edge between the active and saturation modes?

texts: ive recently been fascinated with diodes and was wondering how i'd design a circuit that works at the edge of the breakpoint between the active and saturation mode. How would the circuit be analysed?


texts: How do I make an opamp comparator work in schmitt-trigger mode?

texts:
I want to control a small 12V case fan. I will set values of R1, R2 and R3 so that the fan will work above temperatures 40oC.

I understand that in these kind of systems, there will be an indecisive region in which the comparator output will be fast changing between high and low. In this practical case, when the temperature is in the vicinity of 40oC, there will be an unstable behavior.

Is there any way of make this circuit work in schmitt trigger mode (e.g.; stop under 38oC, start above 42oC, and keep previous state between 38oC and 42oC) by changing it as little as possible, and without using any schmitt trigger logic gate.


texts:
I've come across old synthesizer schematics for an oscillator which makes use of a couple E402s. I am looking for a suitable replacement, and I don't think the specs have to be spot on at all, but I still want "professional" advice.
The source gets between 5 and 10 volts, the drain delivers that voltage minus whatever drop across the JFET, and the gate gets 5 volts so the circuit isn't very demanding. If you need more info I'll gladly add it since I have no clue what info you need to find a replacement.


texts: Is there any arduino module to control water flow?

texts: I want to build my super cool auto flower water gadget. I'm looking for some arduino module like valve or water gate, which can be controlled by input power. So, it can open or close water flow from some bottle by a signal. Any ideas?


texts:
I can not understand why GCC compiler cutting out part of my code while it preserve absolutely the same one in the neighborhood?

The C code:

#define setb_SYNCO do{(PORTA|= (1<<0));} while(0);

ISR(INT0_vect){
    unsigned char i;

    i = 10;
    while(i>0)i--;   // first pause - omitted

    setb_SYNCO;
    setb_GATE;
    i=30;
    clrb_SYNCO;
    while(i>0)i--;  // second pause - preserved
    clrb_GATE;
}

The corresponding part of LSS (assembler file, created by the compiler):

ISR(INT0_vect){
  a4:   1f 92           push    r1
  a6:   0f 92           push    r0
  a8:   0f b6           in  r0, 0x3f    ; 63
  aa:   0f 92           push    r0
  ac:   11 24           eor r1, r1
  ae:   8f 93           push    r24
    unsigned char i;

    i = 10;
    while(i>0)i--;

    setb_SYNCO;
  b0:   d8 9a           sbi 0x1b, 0 ; 27
    setb_GATE;
  b2:   d9 9a           sbi 0x1b, 1 ; 27
    i=30;
    clrb_SYNCO;
  b4:   d8 98           cbi 0x1b, 0 ; 27
  b6:   8e e1           ldi r24, 0x1E   ; 30
  b8:   81 50           subi    r24, 0x01   ; 1
    while(i>0)i--;
  ba:   f1 f7           brne    .-4         ; 0xb8 <__vector_1+0x14>
    clrb_GATE;
  bc:   d9 98           cbi 0x1b, 1 ; 27
}
  be:   8f 91           pop r24
  c0:   0f 90           pop r0
  c2:   0f be           out 0x3f, r0    ; 63
  c4:   0f 90           pop r0
  c6:   1f 90           pop r1
  c8:   18 95           reti

I could assume that compiler figure out that such code is dummy and cuts it out but why is it preserve the same one in the end of the code?

Is there any compiler instructions to prevent from such optimization?


texts: Plotting amplifier transfer characteristics

texts:
Attempting to plot the transfer characteristics of a simple demonstration-kit amp. I reasoned if I extend from roughly equidistant points on both in/out signal, they should meet to represent a fairly correct result.  And since the out-signal is not symmetrical, there must be different response on a falling and rising signal, hence the two.

Would these plots be fairly correct, or am I missing something?


texts: What is the difference between these two relays?

texts:
1- DC12V Coil Power Relay 10A DPDT LY2NJ HH62P HHC68A-2Z With Socket Base

2- Amico 12V DC Coil Power Relay DPDT LY2NJ HH62P-L JQX-13F 10A With PTF08A Socket Base

First assumption is that they are the same thing, but before I jumped to a conclusion I wanted to get some clarification.

If these are different what makes them different?

Thanks in advance!


texts: Will voltage or current determine a diode drop for this battery charging circuit?

texts:
I am using a li-ion battery charger IC that regulates an output to 4.2V. I have a schottky diode in series with the output that then connects to the battery. How do I determine the voltage drop?

If the charger puts out 100mA do I go by the VI curve of the diode at 100mA? Or if the battery voltage is at 3.5V and the output is 4.2V then the drop has to b 0.7V regardless of current? What if the VI curve says at 0.7V the diode is at 200mA, then this case is impossible as the charger can only do 100mA. I'm confused to figuring out the voltage drop of the diode.


texts: In root locus technique, which branch emerging from the open loop poles goes up and which goes down?

texts:
I've recently started to study the root locus concept and I have got this question about the branches. Please refer to this problem here in the link:

http://lpsa.swarthmore.edu/Root_Locus/Example2/Example2.html

In that example, it can be seen that the branches emerging from the open loop poles s=0 and s=-2 when k=0 move along the real axis towards each other as k increases up to the breakaway point. After this, when k is further increased, one of the branches moves downwards and the other moves upwards. It is seen in this case that the branch from the poles s=-2 moves downward and the branch from s=0 moves upward.

Now my question is what is the factor that decides the upward/downward of the branches. Please provide a logical proof.


texts: the output register remains x in the waveform even when clock changes?

texts:
I am using ISE to write my first verilog code .

i wrote a counter :

`timescale 1ns / 1ps

module my_counter( input clk , output reg [3:0] out);

 always @(posedge clk) begin

 out <= out+1 ;

 end

 endmodule

then used ISE to make a testbench (added clk myself!) :

`timescale 1ns / 1ps

module mycounter_test;

// Inputs
reg clk;

// Outputs
wire [3:0] out;

// Instantiate the Unit Under Test (UUT)
my_counter uut (
    .clk(clk),
    .out(out)
);

initial begin
    // Initialize Inputs
    clk = 0;

    // Wait 100 ns for global reset to finish
    #100;

    // Add stimulus here

end

always begin
#5 clk = 1 ; #5 clk =0;
end

endmodule

now when i use ISE simulation mode .

the waveform is like :

to get the proper waveform i first set the time .

then click the "restart" button and then "run for the time specified in the toolbar " .

why the out put is still X after several cycles of the clock ?

does it have anything to do with the comment "  Wait 100 ns for global reset to finish"

(i also tried running the counter for 120 ns but got the same result .)


texts: BJT Voltage Divider Bias Circuit problem

texts:
Let's say we have the following circuit:

The known values are: \$\beta=100\$, \$Vcc=2.5V\$, \$V_A=\infty\$ (meaning the Early effect is not taken into account), \$V_{BE}=0.7V\$, \$I_S=8\cdot10^{-16}A\$ (which is the reverse saturation current of the base–emitter junction), \$Rc=1k\Omega\$, \$R_E=400\Omega\$, \$R_1=13k\Omega\$, \$R_2=12k\Omega\$.

If we assume that the transistor is opperating in active mode, and the Early effect is not taken into account, we can calculate the collector current by:
$$I_C=I_S\cdot e^\frac{V_{BE}}{V_T}$$
where \$V_T\$ is the thermal voltage of approximately \$26mV\$.
All the values are known and we get:
$$I_C\approx0.394mA$$
However, let's say we won't use that formula and we won't assume the transistor is in active mode. We can find the Thevenin equivalent of the base voltage as:
$$Et=\frac{R_2}{R_1+R_2}Vcc=1.2V$$
$$Rt=R_1||R_2=6.24k\Omega$$
Now the equivalent circuit looks like this:

If we apply the second Kirchhoff law to the left contour, we get:

$$Et-Rt\cdot I_B-V_{BE}-Re\cdot I_E=0$$
Since \$I_B=\frac{I_C}{\beta}\$ and \$I_E=\frac{\beta+1}{\beta}I_C\$, we get:

$$Et-Rt\frac{I_C}{\beta}-V_{BE}-Re \frac{\beta+1}{\beta}I_C=0$$
$$I_C=\beta\frac{Et-V_{BE}}{Rt+Re(1+\beta)}\approx 1.07mA$$

As we can see, we get different results. Where did I make a mistake in my calculations?


texts: Anything wrong with this level shift and amplify op amp circuit?

texts:
I posted this circuit in a question about protection clamping, but got a lot of questions around the circuit itself.

Is this not a good / the normal way to shift and amplify a low amplitude (75mv) swinging around ground signal (simulated by Vin) to Vout: 2.5V amplitude signal swinging around ca 2.5V (2.79) ?

For the sake of simplicity Vbat is a stable, regulated 12v source.

Vin is a current sensor, so Vin is practically a DC signal.

The implementation of the circuit gave me a lower than expected center (ca 1.8v) I guess that can explained by too low bias current?

simulate this circuit – Schematic created using CircuitLab


texts:
I need to control the speed of a 220v universal motor using arduino and I am thinking to use an atteny85 ic with a phase control circuit (ltv814 to detect zero crosses and moc3052 to drive a triac to clip the ac sine wave)

I found many example on the internet where people use the same method to control light bulbs and heaters

Will this way work with universal motors (that has brushes)?

If not what is the best way for that ?

Thank you in advance


texts:
I have got two LMC6001 samples.
I will use them for pH sensor interfacing.
With one LMC6001, I can cope with high input impedance errors.
But I want to set offset voltage near by to 2 V.
Can I make offset circuit with other LMC6001?


texts: Stepping from 5 V / 1000 mA to 3 V / 750 mA

texts:
I'm trying to go from 5 V, 1000 mA, which is a USB transformer for Apple devices, to 3 V, 750 mA (which is a small camera I have). I have purchased a NTE1904 3 terminal volatage regulator which 3.3 V, 1 A.

Do I need anything else like resistors to protect the camera? I see in various equations that there is an R1 and R2 on the output side of these things, but I have no idea if I need to put one inline before the camera and what size.


texts:
I was fooling around with a DFPlayer Mini MP3 player, which looks like a really nice and easy to use device.
For some reason I couldn't get mine to output sound on its speaker outputs, so I decided it is faulty. But it did output fine on its line out output, so I attached some headphones and had fun with it.
While it worked (the line out, I never managed to get speaker out to work) I was powering it with 4.5V - 5V from my PSU.
I tried powering it with 3.3V (more like ~3.22) from the same PCU and it didn't work. I thought it is OK, since 3.3V is stated as its minimum operating voltage and my PSU outputs a bit less, so whatever.
But then I tried powering it with a coin cell, which I first measured to about 3.25V, it blinked once and never ever came back to life.
Now it won't work no matter how I power it. It still draws its typical ~30ma from the PSU, but doesn't play any sounds anymore.
Honestly, I don't really care about the device (it seemed like it was faulty anyway), but it made me ask myself, whether undervoltage can actually be dangerous for a circuit and potentially kill it.
It could be just a coincidence, but I'd rather know whether or not undervoltage can be potentially dangerous, so I don't brick something I actually care about in the future.


texts: Are chicken bits left in space-qualified ICs?

texts:
A chicken bit "is a bit on a chip that can be used by the designer to disable one of the features of the chip if it proves faulty or negatively impacts performance."

Would space-qualified logic components leave this feature in, or would the final design "best practice" of space-qualified IC take redundant features controlled by a chicken bit out of the final die?

My guess is that, if a feature with undesirable performance is left in the final die, the chicken bit could be susceptible to a bit-flip by an SEE (single event effect) or other radiation effects, thus running the risk of activating the undesired feature, and possibly affecting the mission in space.


texts:
In 54722-0604, which is the pin #1?

connector page at molex.com


texts:
How can I calculate Kilowatt Hours from:

Complex Power = 1,5 kVA

Electrical current consumption = 10 A

It's three-phase electric power.


texts:
I have two audio systems, one in my living room and one in my office. My sound system in the living room is a Teufel Concept E450 Digital which sadly isn't compatible with receivers (since it's a complete system there's a filter so external sub-in simply doesn't work - I tried everything). I currently don't have the money to upgrade my stuff to an HDMI compatible solution so I wanted to go with a budget solution: I found this tutorial for a 5.1 switch box. As of now I actually just need the front and mid/sub channel as I don't use rear on either sound system.
The tutorial is great but there's a downside: I'm certain that when I switch the channels using this and forget that one of my systems volume is up, I probably die from popping sounds.
So I'd like to avoid this. I asked a friend of my parents' who told me that I basically only need a resistor and a capacitor which compensates the voltage changes when flipping the switch. It's been a long time since I worked with electronics and I'm not really sure where to start here. Can you give me some hints what I should focus on learning (besides the basics obviously)? I'm not sure what I have to take into consideration when it comes to analog audio signals, switching them and so on.
I do have a blueprint which I don't fully understand though. I guess this project shouldn't be too difficult, but I really need to freshen up my knowledge about electronics here. So any help and hint is appreciated.


texts: Wiring Diagram for Split Micro-USB Cable?

texts: I have a customer who is looking for a split Micro-USB cable, which has one USB-A host connector on one end and two Micro-USB cables on the opposite end (they will be plugging into cameras). Can I simply wire it like this diagram I've attached? I believe he has software he is experimenting with where he is trying to control two cameras simultaneously. I've seen "zipper-stlye" split Micro cables like this. Is this simply the operative wiring? Thanks in advnace, friends.


texts: Simulation tool to calculate microprocessor power consumption?

texts: Are there any simulation tools to calculate microprocessor power consumption at the early brainstorming stage of development?


texts: Typical zero sequence data for 80MVA transformer

texts:
I need to model a 80MVA transformer 132/33kV built in 1973. There is very little information on this transformer but I need to populate certain values in the model.

Where can I find typical zero sequence impedance values for this type of transformer?

The positive sequence impedances are as follows:

HV – MV  = 15%
HV – LV   =  22.9%
MV – LV  =  4.9%

Here is the information given:

And the fields which need to be populated:


texts: What happens when we discharge a capacitor through a SCR which we leave open?

texts: I am wondering what would happen when we discharge a capacitor, by using a SCR, through a coil and we leave a current applied to the gate of the SCR. The coil should generate a ‘reverse’ current right? Can this current go through the still open SCR or is this not possible because the SCR consists of diodes, which only let current in from one direction? (We have placed a flyback-diode in series with a resistor in parallel of the coil, if this would make a difference.)


texts:
For very special project I need to transfer data from a USB device to another system remotely as RAW "commands".

The source device is something like a security dongle (not exactly but is a good example to explain the problem) with its own protocol based on USB with is own device driver both on windows and linux and with a medium transfer rate (about 50% of USB2 specification ~200Mbit/s).

The destination system, is reachable only from a specific WiFi network that is isolated from the wired network.

So, without using another PC, I need a way to "Emulate" the source USB device on the destination device without possibility to connect physically to the destination system.

My idea is to build something like a "repeater" using two Arduino as Source and destination. So I will have two Arduino devices with wifi shield, one with the original dongle connected and another one connected to destination device as HID Host.

Now, I've three questions:

Already exists some solution (DIY with schematics is preferable) that solve my problem?
If nothing exists, do you think that this solution will work?
What is the best way to accomplish this task at software level? like some library for Arduino that will simplify my work, something like "Read/Write Raw data from USB and send it over the wifi shield attached to Arduino.


texts: What is the explanation of non-zero VCE voltage of an IGBT while its gate is high?

texts:
While investigating a malfunctioning high power induction heater system (which constantly destroys its IGBT modules), I came across an interesting situation.
Circuit

Gate drivers are SKYPER 32 PRO R and IGBT modules are SKM300GB12T4. There are snubber capacitors on every IGBT's Collector-Emitter terminals. Resonance frequency is ~6.4kHz. The driver module has a built-in overshoot protection and it's enabled. Minimum dead time is set to 1µs.
During the investigation we found out that the short circuit protection function of the gate driver was permanently disabled by connecting the Vc_sense pin to Emitter. So the gate driver can only see zero volts between Vc_sense and Ve.
I thought that enabling this function could prevent the IGBT destructions. However, as we enabled the short circuit detection function by making the required wiring, system (the gate drivers) immediately switches to fault state above 4.5V of DC bus bar voltage.
We disabled the protection again and run the system with a low power, current limiting power supply. While system is correctly functioning, we measured the V_GE and V_CE voltages with an isolated ground scope. Blue is V_GE and red is V_CE of A1 IGBT:

At this moment, the heater heats the sample iron block, indicating the system is working as it should.
Question
As can be seen, when gate is high, V_CE stays ~0V for 10µs and then rises like a sinus wave. How can this happen? Shouldn't V_CE stay at ~0V while its gate is high?
Further experiment
I suspected that it's because of the L//C load and the user side can not drive the gate drivers in a correct frequency/phase, so the load might behave like a power source. In order to eliminate this possibility, I disconnected the L//C load and connected a group of incandescent light bulbs as a pure resistive load.
Results were somewhat similar:

The Voltage source is 55V and current is 130mA during this light bulb experiment.


texts:
I am uncomfortable with the notion of chassis ground but I can't pin down what exactly bugs me. So I'll start with an example and ask a couple of questions on the way. My background is this: I have studied quite a bit of advanced physics at college but somehow I dodged electronics and the practical aspects of electromagnetism almost completely.

Let's suppose we have a battery which is realized as a simple galvanic cell. Because of the difference in electronegativity, there are more electrons in the anode than there are in the kathode. Now if I connect the anode to the chassis, electrons flow from the anode to the chassis until both have the same charge density, right? And if I connect a load to the battery, electrons from the chassis and the anode are exchanged such that the charge density remains approximately the same? So could I say that after chassis grounding, I have the same kathode as before but a bigger anode which consists of the former anode and the chassis?

If the whole chassis gets charged, isn't there a problem that the charges may somehow escape to the environment? Do we have to pay attention to isolate the chassis from the environment?


texts:
I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the battery over time which may or may not have protection circuitry built in. Since the AVR I'm using has a recommended input impedance of no higher than 10K I can't make the divider too large either.

Can anyone suggest a solution that would allow me to monitor this voltage without killing an unprotected battery over a couple of months? The circuit might enter deep sleep mode for an extended period meaning a voltage divider solution would consume the most power.

I ended up using both Hanno and Andy's solution. Thanks for all the input. Can only choose one answer unfortunately.


texts: AVR programming and corresponding machine code

texts:
This is a question on a hand out, it asks:

  What is the machine code that corresponds to the AVR Assembly Language Instruction inc r22? Enter your answer as a 16 bit binary number. There must be no spaces or punctuation marks - just enter sixteen 1's or 0's.

I found the corresponding machine code which is 1001 010d dddd 0011. I added the binaries together for 22 which is 16 + 6 so:

10000 + 110
= 010110

I assume from here that you just sub it into the d's hence,

1001 010d dddd 0011
1001 0101 0110 0011

And there's the 16 bit answer. Is this correct, or have I done this the wrong way?


texts:
I've got a Peltier element rated at 12V / 2.5A (30W), but I'd like some clarification on how I should power it. I'm familiar with building power supplies with LM78xx linear regulators, and I've had a little experience with the LM317, but I've never tried to power anything beyond about 500mW. I'll also be powering two small 12V fans to cool the hot side of the device.

I found the LM350, which seems like a good bet - 3A rated, voltage up to 33V.

I'd be powering this off a UK mains socket (230V AC), so I'd probably set it up the same way I would an LM78xx regulator - run the mains into a transformer's primary, run the secondary into a diode bridge to half-rectify, use a 1mF electrolytic cap to smooth it, then run that source into the regulator.

I have a few questions about this, though.

What voltage should I aim for on the transformer's secondary coil? Somewhere around 15V (e.g. this) seems about right to me, but I'm not entirely sure. As far as I can tell from Farnell and RS, there don't seem to be many transformers around that have low voltage secondaries.
Do I need to use a heatsink on the regulator? If so, are there any resources that would help me select an appropriate one?
Can/should I run the two fans off the same regulator as the element, or should I use a second regulator to power them? I figure an inductive load in parallel with the element might complicate things.
Would I need to do this on a PCB due to higher currents, or could I get away with using stripboard?
Are there any special safety considerations I should take into consideration for this build, aside from the usual ones when playing with mains electricity?

Thanks.


texts:
My question might be already answered but I have some problem with resolving it.
I'm using PC817 Opto-Coupler to turn on a relay. My VCC voltage is about 4.2 volts and the MCU is an STM32F4 with 3.3v voltage level.
When I set the MCU pin (M_Relay) low, it seems that Opto doesn't turn on. I measure the voltage of the input diode(Opto input) and it was about 1v which is below the minimal voltage. I'm not sure about what value should I use for R56.


texts: Force xc32-ld to place all application code in kseg0_boot_mem

texts:
I have written a PIC32MX bootloader application. I would like to tell the linker to put it completely in the boot memory, so that all program space is kept for the final application.

Currently, the what I think are the relevant parts of my .ld file look like this:

_RESET_ADDR              = 0xBFC00000;
_BEV_EXCPT_ADDR          = (0xBFC00000 + 0x380);
_DBG_EXCPT_ADDR          = (0xBFC00000 + 0x480);
_DBG_CODE_ADDR           = 0xBFC02000;
_DBG_CODE_SIZE           = 0xFF0     ;
_GEN_EXCPT_ADDR          = _ebase_address + 0x180;

MEMORY
{
  kseg0_program_mem    (rx)  : ORIGIN = 0x9D000000, LENGTH = 0x10000 /* All C Files will be located here */
  kseg0_boot_mem             : ORIGIN = 0x9FC00000, LENGTH = 0x1000 /* This memory region is dummy */
  exception_mem              : ORIGIN = 0x9FC01000, LENGTH = 0x200 /* Interrupt vector table */
  config3                    : ORIGIN = 0xBFC02FF0, LENGTH = 0x4
  config2                    : ORIGIN = 0xBFC02FF4, LENGTH = 0x4
  config1                    : ORIGIN = 0xBFC02FF8, LENGTH = 0x4
  config0                    : ORIGIN = 0xBFC02FFC, LENGTH = 0x4
  kseg1_boot_mem             : ORIGIN = 0xBFC00000, LENGTH = 0x2FF0 /* C Startup code */
  kseg1_data_mem       (w!x) : ORIGIN = 0xA0000000, LENGTH = 0x8000
  sfrs                       : ORIGIN = 0xBF800000, LENGTH = 0x100000
  debug_exec_mem             : ORIGIN = 0xBFC02000, LENGTH = 0xFF0
  configsfrs                 : ORIGIN = 0xBFC02FF0, LENGTH = 0x10
}

This is the default generated linker script, for a PIC32MX695F512H, although the length of some sections may have changed - the memory layout of the chip is on page 61 of the datasheet.

Should I simply change the ORIGIN and LENGTH of kseg0_program_mem to the values of kseg0_boot_mem and tell the linker to allow for overlapping sections? That doesn't feel that clean. Is there a way to tell the linker to put the application code not in kseg0_program_mem but in kseg0_boot_mem?


texts: Building circuit for n-relays using flip flops, is this the best solution?

texts:
I'm trying to build a circuit for n relays, each relay should hold it's state (ie latched).

My first Idea was to use decoders, but clearly this was a bad option, since the state of the relays won't be maintained, basically there is no on/off toggle.

Finally I've found out that flip flops seem to be a good option, is this the correct path to follow? are there better and simple solutions? Let me know some topics to study.


texts:
I have been trying to figure out some ways on how to resolve the following clipper circuit, but I got confused with the diode which is not in the same line with the resistor.

Also both difference potentials are positive. Does this mean the circuit cuts the signal only through its positive half wave?


texts:
I'm using XCircuit on my laptop running Ubuntu. Since getting middle mouse button action using touchpad is not easy I want to configure xcircuit configuration file. But due to lack of examples I'm unable to the get the desired result. I want to "start wire" with "w"(already defined), "finish" with "e" and "select box" using "Hold_q". Also I want to start the windows in fullscreen.
This is how my current .xcircuitrc file looks like

xcircuit::keybind e { finish }
xcircuit::keybind Hold_q { select box }

But tcl console is giving me following errors.

invalid command name "finish"
invalid command name "finish"
    while executing
"finish  "
    invoked from within
"if {![xcircuit::keyaction 26 16]} {  finish  }"
    (command bound to event)


texts: Triac based switching with reverse voltage protection

texts:
I have created an ESP8266 based controlling circuit which seems to be working fine. But there is only one problem when rotating the fan speed regulator I always see some lights flicker. I think I need to put some reverse voltage protection. And how I can do that I am not sure.
Here is how my schematics looks like.

Is there any suggestions why this is happening and how can I protect my switches to flicker from that?


texts: How to connect multidigit 7seg common anode/cathode display to cascading shift register?

texts:
How can I connect this type of 7 segment display to cascading register like 74HC595? I know I can use 7219, but at the moment I have those cheap registers and would like to see if it's possible.

Not looking for MCU scanning solution!

The problem for me is that segments are interconnected... What is the simple way to connect?

UPDATE:

I've found the following in google. Is it close to what I am trying to achieve? There is only 1 shift register instead of 4 though.

UPDATE 3:

Enlarge


texts: Need some help understanding PIC memory map

texts:
Some background. I use MPLABx with a PicKit2 to program different types of pics. At the moment its the 16F887. I try to stick to the Hi-Tech PICC Lite tool chain but I'm growing increasingly unhappy with how some things are assembled. Operations which should be relativly fast (considering the 500ns instruction cycle at 8Mhz) are taking up to 20us to complete. So I've started inserting my own ASM code to deal with it.

However, I'm having difficulties understanding the memory map provided in the datasheet on Page 20.

Program memory starts at 0005h. However page 23 shows file addresses of special purpose registers, such as Port A for example. The address of Port A is shown as "05h".

I am confused how to differentiate between a memory location 0005h, and the special purpose register located at 05h. How do I reference the special purpose registers?

I've done pretty extensive assembler programming for older HC11 chips, but this is my first venture into PIC asm coding. Any help here would be appreciated.


texts: Tesla coil primary and secondary resistance

texts:
I've been been doing some research about building my own solid state tesla coil.

I've built my tesla coil primary and secondary so I can mount them on an mdf board.

The question is, is it okay if my primary and secondary coil resistance is almost the same.  I'm afraid that something might go wrong because I'm a student and I'm still learning.

Finnaly can someone provide a slayer exiter circuit using tip41c
Please i need guidance

I really need your guys help on this build.


texts: Photon Shot Noise and an Ideal Photodiode and Ideal Transimpedance Amplifier

texts:
Light hits an noiseless photodiode and transimpedance amplifier. The light has photon shot noise. If it is relevant, lets say that the light is monochromatic. The photodiode, amplifier, and any optics create enough gain to observe and characterize the photon shot noise. We want to predict the power spectral density of the noise at the output of the transimpedance amplifier.

On one hand, photon shot noise has a poisson probability distribution function. On the other hand, a probability distribution function of noise tells us nothing about the power spectral density of the noise.

Is the photon shot noise like flicker noise, having a 1/f component or is it like white noise and constant over electrical frequency.


texts: Power in circuit fading away after a few seconds

texts:
I have an RGB LED strip connected to a power source via a breadboard with three MOSFETs that are controlled by a Raspberry Pi. I followed this tutorial to build exactly this setup:

This worked before, but I disassembled everything and moved to a new place. Since I put it together again, it doesn't work any more. When I connect the power supply, nothing happens. If I connect it with interchanged poles for a while, then disconnect it and reconnect it again, with the poles connected like in the picture, than the LED glows for a few seconds and then slowly fades out.
The power adapter is connected like this:

The strip originally came with an IR-controllable power supply. If I use that, the LEDs work:

I double checked that all wires are connected as shown in the image and as it worked before. Can anybody tell me, which pieces could be responsible for my problem and if there might be damaged hardware?


texts: PCIe fails on "polling compliance" state

texts:
I am using the PCIe block of Altera Cyclone IV FPGA, and I have an issue whereby about half the PCIe slots I have tried (on three different computers) do not work.

Debugging with SignalTap shows that the LTSSM (Link Training and Status State Machine) gets stuck on state 3, which is the "polling compliance" state where "all voltage, noise emission and timing specifications are within tolerance".

Altera has a support page but it is not relevant to the Cyclone IV. Some chaps using TI hardware also had a similar problem.

Strangely, given a computer, some of the ports always work, and some of the ports always fail, which suggests (fingers crossed) that my design is not out of spec. I have checked that each PCIe port I have tried is at least gen2 and has at least 4 lanes.

What could cause the LTSSM to be stuck on "polling compliance"? How can I further debug the problem?


texts:
I am working on a 3 Lead amperometric cell in Potentiostat configuration (CE, RE and WE) and I found the word "Biased sensor" and "Bias voltage" all over the datasheet. My question is:

What is a biased sensor ?
Why shall we inject a Bias voltage in a biased sensor ?

Link: http://www.ti.com/lit/ds/symlink/lmp91000.pdf


texts: Capacity of a capacitor fully charged vs half charged

texts:
I read in most places, when people ask "can I replace a 10v 10uf with 100v 10uf?" and everybody answers "it's the same".

Well... how can it be!?, I have a comparator circuit, that uses a little capacitor to set the "on time" of the circuit.

And it makes no sense, is not the same a 10v 10uf cap charged to 10 volts, that a 100v 10uf cap charged to 10 volts...

If I am correct, where can I find more info related to this? if I have a 100v 10uf cap charged to 10 volts, what is the real uF of that cap? when is 10v only?


texts: How can a resistor affect current AND potential at the same time?

texts:
Though the resistor is always introduced as one of the most simple components it is the one which makes least sense to me.

Ohm's law defines the resistance as$$R = \frac{V}{I}$$ this means that the voltage is defined as $$V = I \cdot R$$ and the current as $$I = \frac{V}{R}$$.

So following the law a resistor must affect both voltage and current however the reality is that it only changes one size.

To lower the voltage
To lower the current

This does not make much sense to me because in my understanding voltage and current must be lowered both but in the common LED resistor example it only affects one size:

$$
U = 9V\\
I = 30mA\\
R = 300Ω
$$

you also find use cases where only voltage is affected. How do I interpret this?

What is the factor which determines if the resistor affects either voltage or current?


texts: How to increase write speed with USB High speed host mode with STM32F4?

texts:
I want to write into a text file in a Flash drive using STM32F407 (XCore407I Core Board) and via USB HS mode. I have used fatfs library and also Tilen Majerle Libraries for USB HS HOST mode. I succeeded to write to a text file in a 8GB flash memory. But I have two problems here:

When I use another flash drive except 8GB, for example 16GB one, it can't write to flash and an error occurs in mounting stage.
Maximum speed that I have reached is 1.3MB/s. I want to increase this speed, how can I do this? Does anybody have  any document for using USB HS in STM32?


texts: Does a circuit breaker trip depending on voltage or current?

texts: I've have a GE 120V 20A circuit breaker. I'm aware that once it exceeds the 20A rating the breaker does its job and trips, but what happens if the current is less than 20A and the voltage lets says jumps to 320V. Will the breaker trip?


texts: Charging a high voltage capacitor with power supply. How exactly?

texts:
I have a semi-serious hobby project with a couple of friends where we need to charge a pulse operated capacitor rated to around 4kV with 1500nF capacitance.
For this I need a high voltage supply and correct configuration to do the charging. Now I've done this before at around 300V but simulating this process with multisim is nontrivial because in this case I don't know the inner workings of kV-level sources and now I have some questions:
If I were to use an off the shelf high voltage source of around 10kV maximum voltage and 20W power, how will the system react when the source is connected, possibly through appropriate resistor?
Someone suggested that exceeding 10kV would immediately break the capacitor as the voltage drop is all seen through the insulation inside the capacitor. I think this is incorrect and the voltage drop will mostly happen inside the HV supply, but I'm not entirely sure.
Let's use this cheap individual as our HV source example: Electrostatic Precipitator Power Supply With Output 300W 30KV

Will an excess voltage (measured at the source) break the capacitor before actually charging it?

If not, how does a typical HV source react to the situation? If connected straight to a capacitor (with effectively zero resistance), will the source just see the connection as a short circuit and promptly break or blow a fuse? Or will it just slowly start to ramp the voltage up, until the external capacitor is at equal voltage to source target (or until the capacitor breaks)?


texts:
I have a Sugon T26 soldering station.
It has an European 2 pin plug, I have a 3 pin adapter for it.
As far as I am aware there will be no ground connection using this method.
It comes with a ground connector on the station, crocodile clip style.
Where should I connect the clip? (I am situated at home.)
I have no access to a ground other than in the wall socket.
Am I better off trying to source a 3 cable wire for the power supply and fixing a standard UK plug to it?


texts:
I'm unable to get the correct result for this question.

I've tried using ohm's law like this:

30 = INRTh

I'm not sure if the current through the shorted branch ab would be the same as the current from the source. The answers seem to indicate that this isn't the case.


texts:
Why does the program memory of the said pic contains 1K x 14 where in fact it only contains 13 bit of instructions. Specifically, where does the 1 bit go out of the 14 bit?

Thank you.


texts:
I'm designing a relatively high power pulse generator.

Basically I have a microcontroller generating a clean square wave (0-3.3 V or 0-5 V) which then goes into my amplification circuitry. I want to keep the microcontroller front-end as a signal generator for various pulse shape experiments.

The specs are :

V = 0-40 V (for unipolar pulses), +/- 20 V for bipolar pulses.
Current - up to 20 A peak.
pulse length is [10 us - 10 ms].
budget is a up to 50$ for the amplification circuitry (have the micro front end).
Load : resistive > 2 ohm (hence the 40 V, 20 A requirements)

So far I have a 2 basic designs using bjts:

A pnp -> emitter follower for low output impedance which seems to do
the job, but requires the level at the entrance to be shifted very high (around Vcc which is in my case ~40 V)
Trying to get around the  signal shifting issues, I've come up with a different topology where a npn -> emitter follower.

This time, my first common emitter stage is inverting, so I need to invert the input signal in terms of its polarity. The problem with this amplifier is that it has a huge quiescent current running through its load resistor Using  a common emitter and an emitter follower: using the first one as a switch and the second one as an emitter follower for reduced output impedance (schematic attached). (bottom part). The good thing about this design is that allows me to feed in a pulse 0-1.5 which is convenient to get for my micro (micro=digital=robust, at least in my mind).

I could use some advice as for the following points:

What topology would you use for this type of application?
How could this unipolar (now) amplifier be extended to a bipolar, meaning that the pulses are centered around a center ground line?


texts:
I have an old vacuum sensor. This sensor consists of two windings on a coil and a metal shaft that moves according to the ambient pressure and the vacuum level.
The sensor is calibrated at the factory so that a known atmospheric pressure gives a known inductance on the two coils.
Other people have reverse engineered the operation to produce charts that show the relationship between pressure and inductance of the coils.
Over the vacuum operating range the inductance varies from 0.3H to 1.4H.
How can I simulate this sensor using a combination of software and hardware? For example suppose I have an MCU running firmware that accepts a user input for the current vacuum level. In the firmware I can calculate the inductance of both coils. How can I then produce that result in hardware so that a device which thinks it is attached to one of these sensors is actually attached to my hardware instead?
I know that programmable pots exist for changing resistance programmatically, but what about inductance?
Thanks, Andy


texts: Can I supply a voltage at a specific current? I doubt it

texts:
I recently bought a 100W LED module that recommended 24V 5A to operate. However when I power it up using DC power supply that could supply 30V and 5A max, only the fan (for cooling) is functioning, the LED is not light up. And the current being withdrawn by the module is only 0.X A. I contacted the seller, and I get a reply saying that I should supply the module with 24V AT 5A. The thing is, there's no current demand from the module itself, how I am suppose to supply it? Thus I came to conclusion that the module is defect. Am I right in this case? Or you can actually supply 24V at 5A with some adapter? But I really doubt it.

Thanks for any input!


texts: Problem of noise with load cell and INA125P + Arduino Uno

texts:
I am here with a problem that I cannot solve. Here are the facts:

I have a load cell : http://www.robotshop.com/en/micro-load-cell-50-kg.html
that I want to use in both directions, from -30kg to 30kg approximately (it will be a force sensor in some applications).

To obtain the signal coming from the load cell on my Arduino, I am using an INA125P.

Due to technical constraints, I need to use a 9V battery to power the whole system.
Also, needing to measure the force in both directions, I need the signal that comes out of the INA125P tp be referenced to 2.5V approximately.
Here is the actual schematic:

My problem:
When I am in certain locations, where probably there is a lot of parasitics, the signal from the INA125P varies about 5% when my hand is near the load cell, but not touching it! It only happens at some locations but not others. For example, at home, there is no problem; the signal is very stable. Also, the amplitude of the noise seems to be proportional to the gain of the amplifier.

What could be the problem ?

Thank you

UPDATE 6/05 : To be more precise about the variation, here are some examples:
- When the load cell lays on a table, no forces on it, the signal (after ADC) is 440 (the value are from 0 to 1024). If I approach my hand close to the cell without touching it, the signal drops to 425 and if I touch it, it drops a little bit more to approximately 400.
- When I have the load cell in my hand, and I lift my arm up of about 20 inches, the signal goes up to 460, when I come back to the table, the signal returns back to its initial value.

Therefore the signal is not oscillating, and the variations are always approximately the same, it is not aleatory.


texts: IC which can drive an RGB input to two outputs

texts: Is there a way to duplicate a wire from an RGB source without degrading the signal. I wish to take a wire and split it into two wires without the current halving. (edit) 75 ohms and one RGB signal wire i.e just the blue line.


texts: Designing effective usage time from 12v car battery

texts:
Need a little power design help:

I have a project I'm working on where I have measured that I will use approximately 14.4Ah over 24 hours. This is quite the load for a small timelapse setup where I need the camera clicking for 5 months. I need 24 hour power because once the camera turns off, it needs a human to press the power on button. I will have access to the site, but it won't be everyday access - most likely on the weekends.

I think I'm looking at needing to go with a deep cycle marine battery and a 25w solar panel to keep this system powered on and the battery charged.

As an example, if I have a 40Ah 12v car battery, and I know my draw is 14.4Ah a day, then this battery can give me 2 days of usage?

However my project requires only 5v, and my 14.4Ah is calculated from 5v.

This is where my math breaks up, but if I convert the car battery 12v to 5v output, and draw 14.4Ah a day from it, does this mean I'll get approximately 4 days of usage?

Ultimately I'd like to hook a 25w solar panel to the battery to try and keep it charged, too.

Thoughts? Thanks!

Edit: adding a little info about my project. It may help with the design.

I'm an electronics rookie, I know enough to get me in trouble, but not enough to help fix it :)

I'm looking to setup a long-term timelapse camera. The enclosure will consist of 1 camera and 1 mobile broadband device. I'd like to use solar power to try and keep the unit operational.

Some brief details on my setup:
The camera is a Canon ELPH 130 point and shoot which has firmware on it to take 1 photo every 10 minutes, between 6am and 6pm. When a photo is taken, it'll save it to an Eye-Fi SD Card. When the Eye-Fi receives a new photo, it'll connect to the MiFi and automatically upload it to the internet.

I've connected my Multimeter in-line with these devices to gauge their amp usage.

Here's my findings:

Camera: average current of 0.25a over 2 hours.
Mobile Broadband: average current of 0.35a over 2 hours.

Both devices showed various spikes - mainly when a photo was taken and uploaded. Then the current seemed to "settle down" back into the averages above.

The downside: I need these devices up 24 hours a day because if they lose power it requires human intervention to push a button to power them back on.

So here's my math:

Camera: 250mA x 24 hours a day = 6000mAh
Mobile Broadband: 350mA x 24 hours a day = 8400mAh
Totaling: 14400mAh battery required to keep this thing going for 24 hours.

One thought on the camera and current usage: The camera does not have a sleep function, so it's powered on all the time. It does have a power-reducing mode (LCD off), but that's about it. Perhaps I can connect some jumper wires to the power button to be able to control on/off without a human needing to press it?


texts: Should I wire my electrical actuators in series, parallel or a combination of both?

texts:
I'm working on a project that requires four (4) electrical linear actuators to work together. They must be driven at the same speed, simultaneously.
Let's assume that I have four identical actuators with the following characteristics:

-> 12V DC -> Max draw of 2.5A

(Something like these... http://bit.ly/1QXNqve)

These guys are all rated for 200 pounds or more, which is about 4 times the lifting power I need, and so I figure I can drive them all from a single power source, with the following characteristics:

-> 12V -> Max 6A

(Something like this... http://amzn.to/22m8D7j)

Now, what I'm wondering is whether I should drive them in parallel or in series?
My understanding is that running them in series will draw, at most, the max 2.5A, but at a decreased voltage. It makes sense that they would each get about 3V (12V / 4 motors). Would the decrease in voltage only manifest as a decrease in speed, or also a decrease in lifting strength?

On the flip-side, running them in parallel will provide them all with the 12V they are designed for, but will limit their current to a combined 6A. It makes sense, then, that they would each get about 1.5A, assuming they are equally sharing the load (6A / 4 motors). Would the decrease in current only cause a decrease in lifting strength, or would it also cause a decrease in speed?

I assume that a combination of the two would land somewhere in the middle? (i.e. two motors in series, parallel to another two motors in series)

Please let me know if the logic isn't right. Makes sense to me, but my experience is that motors aren't exactly equivalent to resistors or other constant-draw components, particularly when one motor might have a slightly higher or lower draw/load than the others.

The application requires four actuators, but only a combined total lifting capacity of about 250#. Speed is not a huge concern, they are only required to travel about 15 inches in roughly a minute or less. The quicker, the better, but it isn't a huge deal.

Finally, is one method preferable over the other for maintaining nearly identical driving speeds? These actuators will be responsible for moving a platform, that must remain as level as possible while it is being raised and lowered. If the platform has a concentration of weight on one side/corner, will the opposing motors always drive faster? If I run them in parallel, it makes sense to me that the constant voltage should drive them identically, regardless of load.

I am trying to make this as simple as possible, and so want to avoid additional electronics for monitoring and changing speeds with microcontrollers, etc. Just a simple up/down switch, and hopefully everything else falls into place. The single power source is desirable for space/cost savings, as well as any slight variances in output that two power supplies might have.
Math, sources, experience are all welcome!


texts:
I need some help designing a high current test. I know just the basic concepts of circuits so any help would be appreciated. I currently have a programmable DC power supply that can supply up to 220 Amps. I need to increment the current up to 200 Amps max through all 5 parts and measure the temperature rise. The current output can be controlled by XFR 12-220 but I need some guidance safely routing the current through each part. I was told to put the circuit in series so that each part can be tested up to 200 amps:

We rarely test the parts past 10 amps but we need to have the capability of testing up to 220 amps just in case. I was think that if the resistance of one of the parts starts to spike (i.e. R1), the rest of the resistors will not experience the same current.

If the circuit is designed to be in parallel, the maximum current would be limited to 40 amps per part.

From reading several posts from this site, I'm guessing that I would have to use some sort of a current limiter that would be adjustable since the current would have to incremented.

What I have: XFR 12-220 Programmable DC Power Supply
What I need: Put incremental current up to 220 amps through 5 parts and measure the temperature rise


texts: Why pass pointer to register as volatile?

texts:
I'm working on learning to TDD embedded C by creating an LED driver for an AVR.
In James Grenning's book, he recommends injecting the PORT by passing a pointer to the register into the function.

I came across the following code in the AvrLibc documentation, How do I pass an IO port as a parameter to a function?, and am confused as to why the *port parameter is declared as volatile.

void
set_bits_func_correct (volatile uint8_t *port, uint8_t mask)
{
    *port |= mask;
}

Can anyone explain why they're passing it as volatile? As someone who's a beginner with C, I'm confused and would appreciate an explanation (if there is one).


texts:
I'm building a retro computer around the 68008 CPU
The main board will be simple, The CPU, 1MB of RAM, and a 32kB ROM (Bios/boot rom)

here is the adress map

$000000 - $07FFFF : RAM0
$080000 - $0FFFFF : RAM1
$3F8000 - $FFFFFF : ROM

The rest of the address space is free for any other use, I/O, Floppy, ...

I have in mind a modular computer like the IMSAI 8080 but around 68K CPU, that's why the bus connector as 16 data lines and some other feature for the 68000 CPU

So I'm looking for some review, advice for my design and point me the weakness of it


texts: I want to power some coils using a controlled current, but I know as the coils heat the resistance changes. Will the L298N keep that current controlled at a certain enabler voltage?


texts:
simulate this circuit – Schematic created using CircuitLab
How can I find the power provided by the battery? I've calculated the operation point:

Vce(Q1): 8.12V
IC(Q1) = 1.63 mA
Vec(Q2): 6.25V
IC(Q2) = 4.4 mA

Is there another way instead of summing all the currents entering one of the nodes of the battery and then multiplying it by battery voltage?


texts:
I'm trying to model a Piezoelectric transducer on Proteus and I'm facing the following problem:
the screenshot shows an experiment-derived electromechanical model for the transducer, the output as appears, is measured around the 48.6nF capacitor.

and this is the output waveform over 10 seconds.

afetr attacing a load to the circuit loading effect occures droping the voltage as follows:

as you can see the output vlotage drops signifctaly due to the loading (as far as I know), so to solve the problem I connected a 741 buffer op amp.
and look what I had!!

as you can see the output voltage isn't being heavily droped know but kind od a negative Dc component is being added to wave overtime.
the supply Dc vlotage is +-20 and the sinsiudal input to the circuit is has a frequancy 53.1HZ
any Ideas of what that is and how to slove it?
*this might be a common but I don't know a lot about op amps so sorry if it is.


texts: I want to design a MOSFET amplifier circuit with pulse input. The current and frequency of the pulse is 2.5A and 1kHz respectively. How do I select the input gate capacitor for the MOSFET and what is the purpose of adding capacitor across gate? The input voltage for drain is 5V . How the voltage and frequency of the output is varied if the input capacitor and output capacitor value is varied?


texts: Solid State Relay is giving off voltage even when turned off

texts:
I'm currently creating a circuit according to this schematics i made. I have removed some irrelevant parts for simplification sake.

The SSR in question is a 861SSR210-DC-1. When 5v is applied between the + and - the SSR is able to open the circuit and able to give power to the load which is just a cellphone charger. The problem though is when I turn off the SSR it is still letting through some power, the phone goes back on and off of charging.

Tests I have done that might help:

I removed the load and measure the voltage between A1 and A2. ON = 238v and OFF = 99v on AC settings of my multitester.
Put the both + and - on GND, A1 and A2 read around 99v AC.
There are 2 holes in our wall outlet :)
The SSR is atached to an extension cord, and this extension cord has a LED indicator on it, and when the ssr is off it dims a little bit, sometimes it blinks really fast
The SSR also has a led indicator so when I say on and off, I have checked that the led is also on and off respectively


texts: I would like to use MC34063 in step up mode, but when I change the resistor value it stopped to work

texts:
I would like to use MC34063 in step up mode, to step up 19V to 24V and 1Amps current.

I made this circuit: (the values not correct its only an image from the internet)
The correct values: input 19V, 470uF capacitor, output 24V 1000uF capacitor, inductor 470uH 5.8Amps, timer capacitor 200pF

I recalculated the capacitors and the inductor value with a calculator.

First I made it without transistor and the R1 was 0.27R. It worked fine but the current was only ~400mA.

I added the transistor and changed R1 to 0.1 ohm to be able to serve  1Amps.

When I modified the MC34063 stopped to work, the output voltage equal with the input voltage.

The transistor is fine, because I tried with another MC34063 and the R1 resistor value was 0.27R. When I changed to 0.1R it stopped to work again...

What is the problem? Why doesn't work with 1A output current?


texts:
I am working on a programmable power supply project that has a 15V 30A switch supply and the output voltage would be regulated with a series pass mosfet. I've got some problems figuring out how to sense voltage and current. And I am using an Arduino for controlling everything.

For voltage sense I was thinking to use three voltage dividers (for three ranges: 0-5, 0-10 and 0-15) and switch them with mosfets. Then I would use a 16 Bit ADC rather than the 10 Bit ADC built in the Arduino... Is that an accurate way to sense voltage and what tolerances would the resistors need to have?

For the current sense on the other hand I've got more trouble. I was thinking a current shunt but then I don't know how to amplify that voltage over the shunt. Are there any ICs pre-built for this application? And what resistance should the shunt have?


texts: Renesas CS+ for CC vs for CA, CX vs e2 studio

texts:
I just get started with renesas MCU: RL78 - D1A – R5F10DPJJFB.  I went to Renesas website and saw different IDEs: CS+ for CC, CS+ for CA, CX, e2 studio so I would like to ask what is the differences between them? Pros and cons of each IDE and which one will be most suitable for me?
Thanks in advance.


texts:
I am using a magnet encoder chip AS5147 and I chose to use SPI to read the output position of a gearbox connected to a motor. The position resolution is claimed to be 14-bit when using SPI reading. A button magnet was mounted on the output gear shaft with a plastic holder, and the sensor was mounted on a PCB and the sensor alignment and distance from the magnet was carefully adjusted according to the spec. When the motor was at standstill and I read the position value using SPI command, however, the value was not stable at all. The value variation is about 3bit, which actually made it to be 11bit encoder.

What I want to ask is, if anyone has ever used such magnet encoder before and is it actually so unstable in position reading? Or is it because the alignment or sensor distance from the magnet was not well adjusted?


texts: Configure a PIC pin for Input and Output

texts:
I am working on a project which uses a PIC24FJ64GA002 mcu.
I am working on a bit-banged serial communication function that will use one wire to send data and then switch to receive mode to receive data on the same pin. A separate pin will be used for clocking which will always be controlled by a different board (always an input). I am wondering is there a way to configure the pin for open-collector operation that that it can be used as an input and and output or do I have to change the pin configuration every time i go from reading to writing?


texts:
I have a number of 4 ft (1200 mm) linear LED assemblies which were replacements for fluorescent tubes. (Ballasts were removed).

Three-four of these (~10%) have started to fail after 1-2 years of infrequent use. I'd like to troubleshoot this if possible.

The failure starts as with constant flickering, and this lasts for months. Eventually however the light dies completely.

In all cases the other LED tube in the same fixture continued to work. So its not the fixture.

I've posted photos of the driver board carefully extracted from the assembly. If its possible to test & identify a bad component I'd like to try that, both out of interest & possible economy.

If testing is needed I Can perform a comparison to an identical working unit.

Maybe the whole driver board could be replaced but would have to fit in the same restricted space.

Driver lives under the upper right white housing:


texts:
I have been using LM317L as a current source for generating 2-50mA current for a load, by following the datasheet, P14:

So far so good, but now I have come across LM31L-n, particularly LM317LM/NOPB, which also comes in 8-Pin SOIC form which in the datasheet states that 4 of the pins are Vout.
My question is that is it possible to use those 4 outputs to generate 4 different current sources by using different resistors on each line, given that they are in the allowed range and all together will not pass 100mA, doesn't seem right or am I missing something?

My goal is to have multiple current sources within the given range, so if I can have less IC, it would be great.

datasheet

Thanks and regards,
Pat


texts:
I am trying to use a TIP2955 PNP as a simple switch for an amplifier circuit. (I know TIP2955 is overkill, but I have so many laying around). The amp requires 12V. My logic is 5V. PNP pinouts:

* Emitter connected to +12V
* Collector connected to amp input
* Base connected to logic circuit through a 1K resistor.

When the logic is disconnected the PNP is off.
However, when I apply 5V to the base (via the 1K), the PNP switches on.

What is the required ratio between the emitter and base voltages? From a little testing, it seems this ratio is about 1/2. That is, the base voltage must be at least 1/2 the emitter voltage for the PNP to be in off state. This is unfortunate, as I need to control the 12V switch from 5V.


texts: Can an array of fuses protect a PC port from damage?

texts:
I'm paranoid right now because I made another circuit meant for the parallel port of the PC. While all my previous experiments involving the port were successful (except for one experiment I made a long time ago), I feel I need to make some sort of protection circuit just in case my circuits in the future decide to blow the parallel port.

So my question is, if I made a miniature parallel port extension cable that's about a couple inches long and replaced all of the wires in the cable with fuses, would this be sufficient enough protection for all computers?

I'll explain by example:

If my circuit accidentally sends a logic high output to a data pin on a parallel port hardwired in SPP mode that outputs a logic low, I can see something blow up, but I'm thinking adding a fuse in series with this connection so that this "accidental" connection will blow up the fuse instead of the electronics in the computer. Is my theory correct on this?

If fuses work, what ratings and values would be best?

My circuitry runs on 5V maximum and will likely draw less than 150 mA current.

Also, can I apply this idea to the serial port (or any other port) as well but with fuses of different ratings to match the serial port?

After all, its much cheaper to blow up fuses than it is to blow up my circuit or the PC itself.


texts: Transient Simulation Wilkinson Power Divider

texts:
In ADS, I am trying to simulate Wilkinson power divider with
Transient analysis option using microstrip lines.

However, I am unable to see the effect of 3 db power dividing. That is, at the output, amplitude is the same as input whereas I am expecting it to be half of input. What might be the problem?


texts: Impedance matching for custom level translator board

texts:
I have designed a custom board using SN74LVC1T45. I have followed the schematic of EVM and added few 150R resistors at input and output for reducing the ringing effect.
The custom board will be receiving inputs from an FPGA board and level translating.

The board operating frequency is 10Hz to 20Mhz. I have verified the custom board with signal generator without impedance mathching resistors and results are satisfactory.

Should I use impedance matching resistors at output and input?

EVM Schematic:-


texts: Voltage dip on MOSFET switchable current shunt

texts:
I have the following circuit built up in LTSpice which will be used to switch in different sense resistors for current measurements.

The mAEn signal switches the M1 transistor on at t=10ms which allow current to flow through the 30m Ohm resistor in branch 2.  M3 in branch 1 is turned off the entire time.

Here is a plot of the voltage on Vdev.

The dip goes below 3.2V for about 10ns.

Now, if I remove Branch 1 like so.

I simulate this circuit, there is no voltage dip on the Vdev net as can be seen below.

Just cutting the line on the branch 1 path gives the same result (ie the following circuit also produces the same voltage as above with no dropout).

Why is it that turning on the transistor with less line impedance (branch 2) the voltage drops.  This is like having a pipe with a small amount of water flowing, then opening a valve to another pipe with much higher water pressure and the pressure in the original water pipe dropping when you do it? Can somebody explain what is going on here?

What modifications can be made to the circuit to remove the transient voltage drop but have multiple branches?


texts: Power Supply stopped working after soldering

texts:
I am new to electronic circuits.
I built a basic led circuit on a breadboard to test everything out.It worked as in pictures,but the connections were not stable because the holes were very large.I started soldering some connectors for easily using the supply (it was the first time soldering something). After that it didn't work anymore...I believe maybe I melted the T05 part of the supply(it's close to the positive hole).
1.Why did it stopped working?I tried remove the connections(but I don't have anything to drain the metal).
2.Can I repair it or is it dead?The little led on the battery block is still working.
3.Why can't I use only a basic battery and place some connectors at the end?
4.Why does this power supply has 3 negative terminals and only one positive?
Thank you in advance!


texts: Is a BJT at the edge of saturation when Vce is at a given constant or when Vce=Vbe?

texts:
We are shamelessly inconsistent with this in our Electronics intro class. If Vce,sat is given we use that but if it isn't we make sure that the base-collector junction is neither forward nor reverse biased and find it ourselves. The TA horribly failed at explaining this so I thought I would ask for the infinite wisdom of random strangers online.

I understand how the junction biasing would be decisive of this but the Vce=0.2V approximations independent of base voltage also exist so I want to learn where that comes from and which is the more correct way.


texts: Different time constants for charging and discharging of modified RC circuit

texts:
I recently performed a test in an electrical measurements lab which left me confused. I measured the response of the following circuit:

And obtained the following output:

According to my professor, the charging and discharging of the capacitor has different time constants. Why is this the case?


texts: The equivalent Potential difference across an inductor and a capacitor?

texts:
In the figure below,

The current intensity is 4A, and V1 reads 80V, and V2 reads 64V. What is the reading of V3? In another way what is the equivalent voltage for an inductor and a capacitor?
In my textbook, it says that V3 reads 16V, but I don't understand why the voltage across Xc and Xl together would be:

  V1-V2=V3=
  80-64=16.

Could you please explain it for me?


texts: Sense Resistor in Battery Charging Circuit

texts: I have a 3 18650 in parallel Li-ion battery pack and wish to use the LTC4162 as the charger and LTC2944 and the level indicator. I am unsure as to who to wire them to effectively use both. I noticed that they both have a sense resistor and worry that it will be redundant for both of them to have it. Is there a way to correctly use both parts on one battery? I don't think the 4162 makes for a good level indicator, although it has a sense resistor to measure battery current, it cannot display that information as effectively as the 2944 could. Can I use both? How do I?


texts:
I am trying to create a circuit with multiple 5V logical control lines pulled down with 10K resistor.

Is the below circuit the right answer? I can't help but feel like this will create a short across all logic lines.


texts: Connecting two power supplies and preventing reverse feeding either

texts:
Is there any way to prevent current from passing through a certain wire without actually cutting off the power from that line.

To be clear, I'm using 2 power source and because of "even with 0.0001v difference, they are going to fry each other when you connected them in parallel" rule, I used Schottky diode but the voltage drop is too much. My power source is 3.3v but with the voltage drop it went to 2.9v. Is there any work around.

Also, will this be a good way for my application
https://www.instructables.com/id/Reverse-polarity-protection-for-your-circuit-with/

Based from the circuit alone, I can say that it will cut the power from the source as soon as it sense a reverse current.

I don't wanna protect my device, I just want to combine the 2 power source without frying them. (Wait that's protection)
So that's it.


texts: It is quite obvious that we can't build an amplifier out of resistors (because of their linearity). But is there a circuit theorem that states the impossibility of building an amplifier out of diodes (semiconductor or vacuum tube ones) without using transistors, relays and other 3-terminal devices?


texts: Relationship between brushless coil inductance and back EMF as a function of phase angle

texts:
In general, does the inductance across the coils of a brushless motor have the same waveform as the back EMF? That is, if back EMF is sinusoidal, should I expect the inductance to be sinusoidal [with twice the frequency]?

My understanding is that the inductance of a coil in the stator changes with rotor position when the nearby permeable material in the rotor magnets changes the effective permeability of the inductor depending on their proximity to the rotor magnets. I am assuming that the small test signal to probe inductance doesn't saturate the magnetic material, so it stays linear and reacts identically independent of the pole orientation. However, it's beyond my introductory understanding of magnetism whether the geometry that produces a certain waveform for back EMF also varies the inductance in the same way.

So far, I've taken a crude look at the inductance of a motor with a sinusoidal back EMF signal:

The measurement circuit

I see a vaguely sinusoidal dependence on rotor angle, but this preliminary glance was exceptionally ad hoc, using the ADC of a cheap microcontroller and a tabletop function generator to get a quick look into the system. I'm seeking a theoretical relationship between the inductance and back EMF before moving much further with the idea.


texts: Wide Range Input DC DC Buck Convetrer Design

texts:
Im having trouble understanding how i can achieve a constant output voltage with a varied input voltage. I know how to design a buck converter with a constant output when the input voltage is fixed but not when the input voltage varies.
How do i ensure the output voltage stays constant for a varied input voltage.
Thakyou


texts: Why is common-mode noise on a power line bad?

texts:
I've always been intrigued by common-mode noise, as it seems to be such a pertinent issue when it comes to op-amps, chokes, etc. used as solutions to remove it.
I understand from a digital signal point of view (as explained very well here) why it is a bad thing, as on a differential pair it means the differential voltage (V+ - V-) taken at the receiver will bounce and fluctuate around some value (the common-mode voltage), when you would in reality want this to be stable.
What I still haven't quite understood is why it is a bad thing on power lines (mainly low voltage ones, not really talking about mains voltage here but I suppose it's the same deal). Like such, consider a power supply (maybe even isolated) that has an output of 24V. It is fairly common from the designs I have seen to use a choke on the output:

What exactly would this achieve? I could be wrong but no matter what the common-mode noise is, the device being powered won't care as the only voltage that matters is the differential voltage relative between the two rails. I.e. at an instance of time, say the common-mode noise is rapidly bouncing between -10V and +3.5V. The rails (Vcc, GND) will be bouncing between (14V, -10V) and (27.5V, 3.5V), which still leaves the differential at (14 - -10) (27.5-3.5) 24V in either extreme (duh).
So, why is the choke helpful at all?
They have a whole category on Digi-Key ("Common Mode Chokes > Power Line"), so surely there is some reason they are used.


texts: Simple surge protection circuit for incandescent bulbs

texts:
A friend of mine is having a large, fancy / artistic lamp at home (Europe) and uses a "500W incandescent bulbs on 230V" as recommended by the manufacturer (link).

His problem : every month or so the bulb blows up, and he needs to change it (it's annoying and these bulbs are expensive). It mostly (only?) blows up when he turns on the light from the wall electrical switch (which actions the wall socket where the lamp is plugged into).

Without being certain, I suspect the issue is coming from overvoltage (*).

My question : if indeed the cause is overvoltage, what would be a simple (in a minimalistic sense), yet practical and robust electrical / electronic circuit that a hobbyist could build to insert between the mains socket and the lamp plug to remove the surge? I assume that the right combination of inductors, capacitors, resistors or diodes (maybe a fuse?) used properly could be enough, but if more "fancy" components could make a significant improvement (eg gas discharge tubes?), then why not.

Thanks for your help.

(*) not very scientific but in order to make sure that the issue is not due to a defective wall socket (or another part of is home's electrical wiring), I suggested that he temporarily plug the lamp into another socket, in another room. He did that but he got the same issue (burnt two bulbs in 3 months). I am not living nearby, so I could not go and test the surge myself.

PS : for those of us who are "environmentally minded", I did suggest to stop using incandescent bulbs, but he would not listen - apparently the point with these lamps is to use old style bulbs, that's what makes their charm (I do not really understand but anyway my motivation is elsewhere, I want to learn how to fix this sort of technical issues efficiently).

Addition : here are a couple of photos of the bulbs used, in case it helps.


texts: Question about a circuit problem with opamp

texts:
I would like to solve the following circuit, but I can't understand why i1=0, whereas i2=v2/R1.

If i2 is not equal to 0, where does the current go after the first resistor?


texts: Need help with sequential element being partly removed from the module even if I am using completely

texts:
I have a simple module that split rows between different engines. In this module row_start_r is a register that is a counter that skips the count by a specified offset and eventually gets written in a FIFO. The following code works in simualtion but not on the actual FPGA.

The only thing suspicious in the synthesis report is that the tool sets the lower bits of row_start_r register to 0 and gives the following warning

 INFO: propagating constant 0 across sequential element (i_13/\LOAD_BALANCER/row_start_reg_reg[0]
 INFO: propagating constant 0 across sequential element (i_13/\LOAD_BALANCER/row_start_reg_reg[1] )
 INFO:  propagating constant 0 across sequential element(i_13/\LOAD_BALANCER/row_start_reg_reg[2] )

Following is my code.

`timescale 1 ns / 1 ps

module split_rows #(
     parameter NUM_ENGINES               = 2
)(
   input  wire                  clk,
   input  wire                  rst,
   output wire                  done,
   input  wire [63:0]           num_rows,
   output wire                  ready_out,
   input  wire [NUM_ENGINES-1:0] engine_ready_in,
   output   [63:0]              start_row_pos_out,
   output   [63:0]              end_row_pos_out,
   output  [NUM_ENGINES-1:0] engine_select_wr_out

);
reg [2:0]                  engine_id; /// num_engines
wire                       fifo_empty_s;
wire                       fifo_full_s;
reg                        fifo_rd_en;
wire                       fifo_wr_en;
reg [NUM_ENGINES-1:0]      engine_select_s;

reg  [63:0]              row_start_r;
wire [63:0]                row_start_out;
reg  [63:0]             start_row_pos_out_s;
wire [63:0]             end_row_pos_out_s;

always @(posedge clk)
 begin
  if (rst == 1'd1)           engine_id <= 3'd0;
  else if (engine_id ==  NUM_ENGINES-1) engine_id <= 3'd0;
  else                       engine_id <= engine_id + 3'd1;
end
always @(posedge clk)
begin
        if(rst) begin
                row_start_r <= 64'd0;
        end
        else if (fifo_wr_en) begin
                row_start_r <= row_start_r + 64'd32; //skip_offset ;
        end
end
assign fifo_wr_en = !rst && !fifo_full_s && (row_start_r < num_rows);

fifo #(.DEPTH(64), .WIDTH(64), .AFULLCNT(60), .RAM_STYLE("block") ) offset_holder (
    .clk    (clk),
    .reset  (rst),
    .push   (fifo_wr_en),
    .din    (row_start_r),
    .afull  (fifo_full_s),
    .full   (),
    .cnt    (),
    .oclk   (clk),
    .pop    (fifo_rd_en), // from write engine
    .dout   (row_start_out),
    .empty  (fifo_empty_s),
    .rcnt   ()
   );

always @(*)
   begin
      engine_select_s = 0;
      fifo_rd_en      = 0;
      start_row_pos_out_s = 64'd0;
      if ( !rst &&  engine_ready_in[engine_id] == 1  && !fifo_empty_s  )
      begin
         engine_select_s[engine_id] = 1;
         fifo_rd_en = 1;
         start_row_pos_out_s = row_start_out;
      end
end
 assign end_row_pos_out_s = (start_row_pos_out_s + 64'd32 >= num_rows) ? num_rows: row_start_out + 64'd32;
     assign ready_out            =  !rst && !fifo_empty_s;

assign start_row_pos_out        =  start_row_pos_out_s;
assign end_row_pos_out          =  end_row_pos_out_s  ;
assign engine_select_wr_out     =  engine_select_s    ;

done_stall #(
      .LENGTH                 (4)
   ) DONE_OUT (
      .clk                    (clk),
      .rst                    (rst),
      .done_in                (fifo_empty_s),
      .done_out               (done)
   );
endmodule

If somebody can review it and point out the mistake that would be really helpful.Thank you.


texts: Servo or Stepper, which is best for forward and backward rotational or linear motion (Horizontal)

texts:
Im designing a simple system which holds a weight of around 5Kg in a platform. The platform semi rotates on a center point. 20 or 30 degrees both direction. There could be maximum kg of weight on the platform.
So its like below ddesign

There I marked the red x to say it rotates maximum up to those points.
So my query is which is best for this purpose , Servo or Stepper. Also any suggestion about motor specification for that scenario. Im using Arduino to control. and thinking about 2 motors(Is it required). Also I need to control the speed of rotation.


texts:
I am working on a headphone circuit that plugs into an iPhone , between the mic wire and the GND wire there is the mic , and a push button , with iPhones when you press the button once it will pause/play music , twice will skip too the next song , and three times will go too the previous song , this is all done with one button , however I want too implement 3 buttons for previous song / play-pause / next song , is there any way to implement a button trigger delay so that when I press the forward and reverse button , it will send a signal to the phone that it has been pressed 2/3 times , is there any way of putting in a delay , thanks
UPDATE: I have found a step up module from 0.8v too 3.3v , does anyone know how much current I can draw from a 3.5mm socket and whether this will be enough too power a small micro controller such as the Arduino pro mini ? Thanks


texts: Are there any transparent enclosures or housing options out there for the Stellaris LaunchPad?

texts:
I come from an Arduino background, where there are a number of enclosures available for the standard board sizes.
We've just installed some software on a Stellaris LaunchPad at work, and we want to show it off so people can see the RGB LED, but the board not only lacks any mounting holes, but googling doesn't seem to show up any options for enclosures either.

Do such things exist for the Stellaris LaunchPad, or is it only intended as a learning aid for hacking around with, and never for actual use?

The dimensions are listed as 5.0 cm x 5.715 cm x 10.795 mm (L x W x H)


texts: What to use instead of 1k1 Ohm PTC thermistor?

texts:
I've got uni-t ut60a damaged. IC was replaced. Two tracks were repaired. The PTC thermistor of 1k1 Ohm is left. Unfortunately it is not easily available, in fact I couldn't find any of these being sold (wmz11a 75HV).

simulate this circuit – Schematic created using CircuitLab

I measured at what voltage clamp transistors pair start to conduct, it is 8.3V.

So my guess is that the device in place of PTC thermistor should have drop voltage = Voltage_applied - 8.3 (at least) in order to not damage anything.

Is there anything which could replace 1k1 Ohm PTC thermistor?

By the way, multimeter is rated 1000V. I would be happy it to work with mains 230V 50Hz.


texts:
I'm designing a battery charging circuit for a portable device. Conceptually it looks lik so:

simulate this circuit – Schematic created using CircuitLab

As a safety function, the circuit can be interrupted by the transistor, thus interrupting the battery charging process. What leads me to write this post is that I need a transistor design that is normally closed (battery is normally charging). However, if a problem is detected, an MCU would send a control signal to it in order to open the circuit and stop the charging process.

My questions in conclusion are:

What kind of transistor should I use? A depletion P-Channel Mosfet? If so, how would the circuit look like?
Could this be accomplished with a normal P-Channel Mosfet (normally open unless activated) with some additional circuitry?

Thank you very much for your time and help!


texts:
I’m trying to see if a copper sheet I have with me (25 cm X 30 cm, 0.05 cm thick. There's a 6 cm X 6 cm square hole in the center to place a lamp.) is sufficient to keep 36 luxeon rebel LEDs (mounted on coolbase square) at a junction temperature below maximum. The arrangement of LEDs in the copper sheet is fixed, and is as shown in the attached figure. As shown, the arrangement is very compact. So I did the following calculations:

Maximum Junction temperature: For Red LEDs in the array, this is 125°C, so I chose 115 °C for design.

Power dissipated as heat (~80 % of LED power): 67 W for 36 High power LEDs.

Considering individual junction to case thermal resistances, thermal resistance of coolbase MCPCB and interface material, and applying law of parallel pathof thermal resistances, I get a junction to heatsink thermal resistance of 0.3818 °C/W.
Thus allowable maximum heatsink temperature = 115 - 67 X 0.3818 = 25.6 °C = 89.4 °C

The heat transfer from heatsink to ambient air takes place through convection and radiation. The equation is:
Power,
$$P = hA(T_{s}-T_{\infty})+\epsilon \sigma A ((T_{s})^4 - (T_{\infty})^4)$$

h is the convective heat transfer coefficient. For forced air convection, (I'm using a fan on top of the heatsink) h begins from 25.

A is the surface area.
\$\epsilon\$ is the emissivity. For burnished copper, emissivity is 0.07 according to this page.

\$T_{s}\$ is surface temperature or heat sink temperature
\$T_{\infty}\$ is ambient temperature.

Substituting an ambient of 43 °C (316 K) and solving for surface area, I get:
Required minimum surface area: 0.056 \$m^2\$.

Available surface area (copper sheet outer surface, excluding 6 cm X 6 cm hole) is 0.0714 \$m^2\$.

I think I should be safe. Did I miss something, or can I use this copper sheet?:D


texts: How to limit base current in transistor when collector current is unknown?

texts:
In the followig circuit I am trying to replace a push button with a transistor:

simulate this circuit – Schematic created using CircuitLab

In the schematic SW1 is the push button that opens and closes the tray of a CDROM drive, V1 is the 5V power supply of the CDROM is the control board for the drive.

I want to control the tray operation with an arduino connected to the base of an NPN transistor with collector connected to V1 and emitter to P1.
The transistor I'm going to use is a TIP120 (I know it's overkill for this operation but it's what I have lying around).

The problem I'm having is that I don't know how to calculate the value of the current limiting resistor that is needed between the arduino pin and the transistor base to prevent the transistor drawing too much current from the pin, damaging the pin.

According to all the documentation I read (one example http://www.zen22142.zen.co.uk/Design/bjtsw.htm) one needs to know the current that will flow across the transistor when it is on.

But in my case, I only know the voltage across the two terminals of the switch. I have no idea what's between P1 and P2 (i.e. inside the CDROM control board), and no idea of how much current is drawn when the switch is closed.

How do I calculate a safe resistor value for the base resistor in cases like this ?


texts: What is the minimum current a current transformer can sense?

texts:
Datasheet of AS-100 mentions a maximum current it can sense before saturation, but what is the minimum current it can sense.

For instance, if I put 10 mA 50Hz through a conductor passing through the sensor AS-100 (1:50 ratio), will it produce 0.2mA through a 50 Ohm (suggested) terminal resistance on it's secondary?


texts: Control rheostat digital pot w. arduino - rheostat can't "turn off"?

texts:
I have a digital rheostat 10 kOhm potentiometer, that I want ultimately to control the volume of a radio, but for now, just want to fade an LED.

I have it fading in/ almost out, except I cannot make the LED turn of entirely.

I've been reading about the differences between rheostat and potentiometers - and many people mention different things, so I'm kind of confused. Also - i thought I ordered a digital potentiometer, but by accident bought a rheostat. soo.. is it even possible to make a rheostat "turn off" entirely?

I have attached a schematic of the setup, and the code:

link to digi pot datasheet:

http://ww1.microchip.com/downloads/en/DeviceDoc/22060b.pdf

BREADBOARD:

SCHEMATICS:

ARDUINO CODE:

#include <SPI.h>
int ss = 10; // slave select pins

void setup() {

 // set SS pin directions
 // Others are handled automatically

 pinMode(ss, OUTPUT);

 //Initialize SPI
 SPI.begin();

 Serial.begin(9600);

}
// function to set LED to specific level
// reg is the register, register is the index - this is only one pot,
// so the reg is == 00000000
// level is the leve

void setLed(int reg, int level) {

  digitalWrite(ss, LOW);  // set SS to low for communicating to that chip
  SPI.transfer(reg);      // send register / index
  SPI.transfer(level);
  digitalWrite(ss, HIGH); // Finish writing to that chip
}

void loop() {

 for(int i = 0; i<255; i++) {

   setLed(0, i);
   delay(20);

   Serial.println(i);
 }

 delay(500);

   for(int i = 255; i >= 0; i--) {

    setLed(0, i);
    delay(20);

    Serial.println(i);
   }
 delay(500);
}


texts:
because UV-C machines tend to be expensive, our lab working on biological/biochemical research has reverted to attempting to build a machine from scratch.

Therefore, we recently purchased a G23 socket and a Phillips 11W UV-C bulb. Ideally, I would like to be able to make use of an IEC socket in this system, and just simply plug the machine into the wall when we need it for experiments.

Of course I would like to do this as safely as possible. I have found bits and pieces of information around, but no concrete guide.

Any advice about how to minimally and safely connect the pieces is very helpful.


texts: Will this 5-watt audio amplifier work for my speakers?

texts:
I found this schematic and it says the speaker used is 5W and 8Ω. However, the speaker I have is a 5W and 3.2Ω. Will it work? What are the conditions? And what would be the effects?

And if it's okay, I want to modify this to work in stereo because I have two of these speakers. How will I do it?


texts: Optimal Grounding for a PVC Dust Collection System?

texts:
It is common in woodworking (A hobby of mine) to make a dust collection system (Basically a tube hooked up to a vacuum to carry away dust created from automatic woodworking tools) out of PVC.

We'll assume that we're using a PVC dust collection system (I'm aware that we could sidestep the issue by insisting that we use a conductor)

Apparently, due to the physics-chemistry of rubbing PVC, this develops a large static charge.

Solutions to this problem include running a bare copper wire around the outside, inside, or some combination of both. (Similar to https://www.youtube.com/watch?v=XtkHzmXe4ZA)

My question is: What solution is optimal, and are certain solution invalid or wishful thinking?

PVC is an insulator, meaning (In the traditional charge model) that charge cannot move through regions of the PVC and is not guaranteed to be distributed equally.

Is grounding on the outside of the PVC useless since this isn't where the charge builds? Is screwing into the inside of the tube not helpful since charge can't move to the grounded screw?

What is the optimal way to ground a PVC dust collection system?


texts: Solving for equivalent resistance w/ short circuiting

texts: I am working on finding the equivalent norton and thevenin circuits. To fond the equivalent resistance, I zero out any sources. When this happens, according to my professor. Only the 10 ohm resistor to the left is short circuited as a result of the zeroing. Why is this the case? Why is the 12 ohm resistor not also short circuited by zeroing out any sources?


texts: Preventing my amplifier from being fried again and using diodes

texts:
I'm experimenting with sending different signals through different toroidal coil windings, I also place a ball compass in the center to see the type of rotation it creates.

I would like to prevent my amplifier from being "fried" again.

I'm thinking I need diodes between the amplifier and the coil but I'm not exactly sure how to calculate the correct values needed.  I'm also open to using a different type of setup but please know I'm limited on funds.

The reason I think diodes may help is "current passing through a diode can only go in one direction, called the forward direction. Current trying to flow the reverse direction is blocked. They're like the one-way valve of electronics"

The way I have it setup is very simple:
signal generator(computer) -> amplifier output 8 ohm impedance -> toroidal coil

See video link to my test setup:
https://youtu.be/rPHWugUoHCs


texts: Been struggling to find information that I find to be obviously missing on how to interpret antenna radiation patterns. For example have a look in the datasheet for my chip antenna. I can understand the three 2D radiation pattern graphs, one for each plane, what I don't understand is what the Horizontal and Vertical plots mean in the context of an antenna. I know it refers to the polarization of the RF waves transmitted/received, but couldn't find a decent source explaining exactly how this information can be used correctly.