texts:
We are using the LMH6611 OpAmp from TI as it offers  high current rail-to-rail output (100mA) and high frequency (345MHz), which seems to be quite unique in this combination. In addition, the power consumption is only 3-4mA due to the datasheet, which is also important for us.

However, we noticed that our opAmps draw more than 30mA, even if they do not have to drive anything.

The setup is a multilayer PCB with GND and 3.3V plane with decoupling capacitors near the chip. the opamp is powered by this voltages.

A 1:1 voltage divider passes half the supply voltage to one input, the other usually gets an external signal, but for testing, we connect it to GND or the supply voltage. The output is not connected to anything for the test.

We also inspected supply voltage, inputs and output via scope, but we found no increased noise, oscillation or whatever. We tested several chips, even from different batches, always with the same result. We have no idea any more and start to believe in an error in the datasheet...

Does anyone have an idea why this opAmp draws so much more current than written in the datasheet?

Edit:

Here is an schematic.

The current was first observed on the bench power supply, later we measured it directly at the supply pin of the opAmp either via ampere-meter or voltage drop across a measurement resistor.

simulate this circuit – Schematic created using CircuitLab


texts: Timebase Ground-Loops - why place the isolation transformer at the input instead of the output?

texts:
In the course of investigating the construction of a home-made 10 MHz lab frequency reference I wondered if the output from such a reference should be isolated. I came across a small article about this in an issue of Hewlett Packard Bench Briefs (1st Quarter 1995, page 2-3) where the author had a problem with ground loops due to the shared connection to his "house frequency standard". Here is a quote from the article and a retouched copy of the illustration showing the problem and the solution:

The Solution
Break the timebase ground-loop by inserting isolation transformers between the frequency distribution amplifier and the external timebase input of each instrument. (Place each isolation transformer as near the external timebase input as possible.)

Figure 1. Block diagram showing simplified ground-loop problem

The author is carefully telling us that the isolation should happen at the input to each device, both by writing so explicitly and by pointing to them in the diagram.
Why is the position of the isolation transformer so important here? What is the difference when placing it at the output of the distribution amplifier?


texts:
I am very surprised with difference in capacitor cost (up to 10 times) like this and this.
These two have same capacitance along with voltage rating and tolerance level.Then what are the reasons behind these high differences in cost ,is it something due to material used to design it or it is just due to the different vendor providing it ?


texts: Transistors are closing slower than opening - will it be problem in H-bridge?

texts:
I want to build robot with 2 DC motors to move like a tank. So I need 2 H-bridges (one per motor) to be able reverse the rotation.

I used https://www.pololu.com/product/1117 motors rated for stall 0.8A at 6V, and rated to 3-12V. I also used some H-bridges rated 2A+ and 7.6V LiOn battery, but eventually I burned 3 H-bridges :(

On the last I was able to make some measurment and it showed -30..30V spikes (on DSO138 osciloscope) and sometime about 1.6A (at common mutlimeter - slow).

So I decided to build more robust H-bridge (to not burn at all) and make measurement on that. something like BJH H-bridge going in reverse but not forward, LL transistor overheating with transistors rated 10A, 100V ( TIP142, TIP147 ).

But I found in datasheet, that for Resistive load
Turn-on time is 0.9us while Turn-off time is 4us - this lead me to conclusion, that when swithing eg. left side top/down it would shortcut the rails for 4 - 0.9 = 3.1us

Is that right conclusion? Is that a real problem? And if it can be corrected/used, what is good PWM speed to drive it effectively?

Thank for your help


texts: What voltage and/or current for an unlabelled motor

texts:
I have a box full of DC motors that I've been scavenging from old electronics. Most of them have no labelling whatsoever, so I'm lost at determining what voltage and or current would be adequate to drive them.

I connect them to my power supply and increase the voltage to get the minimum, and after they start spinning, I can keep increasing the voltage and see them spin faster, but, how can I know if I'm within the range of the motor and it's not going to burn if I keep that voltage for a while?

Although the questions is generic, I'm talking small motors here, so voltages from 3V maybe up to maximum 12V or 18V.

Is there a test or rule of thumb or relationship between voltage applied and current drawn that I could use? I'm testing them without load but I guess could test with load if needed.


texts: Direction of flow of current in secondary circuit in AC transformer/rectifier

texts:
In this transformer/rectifier if the current in the primary circuit is clockwise what will be the direction of current in the secondary circuit?Why?

I'm feeling a bit confused about the direction of flow of current due to flux linkage of primary coil with secondary.Please help!


texts:
I'm a hobbyist EE in college, and have been building breadboard circuits and perfboard circuits for the past year or so. I want to move on to doing PCB design.

I wanted to start with something small so I designed a small amplifier circuit for a microphone that I want to make into a module on a PCB.

Here is the file for what I designed in Fritzing (I went with this software because it's user friendly):
http://www.mediafire.com/?2b2as7iibys68cu

Here is an image if you don't have the program:

Is this a good design? How can I improve it?

The general schematic I followed was this (in case you wanted to know):

(Credit @Olin Lathrop)

What advice can you give me on getting started? Any resources you can recommend?
What software would you recommend? Ideal would be free and easy to learn.
What type of class would you suggest I take in college to get deeper into this?


texts:
I'm designing an MCU card for a 64-pin dsPIC, something like this:

I have several questions regarding MCU card design (two-layer board):

Is it enough to place only one bulk 10uF/6.3V capacitor (tantalum), instead of 4 of them? These little buggers are quite expensive, and I've read somewhere that it is perfectly fine to use only one. I also plan to put a tactile switch on MCLR (reset) pin, and a LED indicator for power supply - both of these components would go in separate corners, leaving no space left for bulk capacitors.
Is it OK to place traces under a crystal? When it comes to crystal soldering, should I leave some space between the bottom of the crystal and the board (let's say 1-2 mm), or this does not matter?
The dsPIC has power supply pins on all 4 sides. Is it ok to connect these pins under the microcontroller? Something like this:

I plan to use a combination of 100nF/1uF ceramic capacitors between Vdd and Vss, placed on a bottom layer. Is it enough to use only one pair, or should I use 4 pairs of capacitors - one pair for each Vdd/Vss pair? If it is OK to connect Vdd and Vss under the microcontroller (see Q3), I suppose that it is OK to use only one pair of capacitors.


texts: Memory modelling and Memory module in Verilog synthesis

texts:
I am using a synthesis tool and when I am synthesizing a verilog file

module test();
reg reg1;
reg [1:0] reg2;
reg reg3 [1:0];
reg [1:0] reg4 [0:4];
endmodule

It's giving an error to "use memory module" with the help of a option.
So what I need is to make a memory module. I tried to read this link but it didn't help me very much.

How can we create a memory module that can be used with the above test case. I am new to verilog. So can't understand what "Memory.list file" in the link
means.


texts: Creepage on SMT DIP package with an NC pin

texts:
I'm having trouble understanding how the CPC1972GSTR can have the specs it does.

Here's the datasheet.

In particular, it has a blocking voltage spec of 800V, but if you look at the recommended footprint, there's the NC pin between the two switch pins.

Doesn't the presence of that pin reduce the creepage distance between the two switch pins? Even if it's NC, it's still conductive, no?


texts: AVR timer output when Data Direction Register set to input

texts:
This question refers specifically to an ATmega328P, but probably can be generalized to most or all AVR MCUs.

Known 1:  When the Data Direction Register (DDR) for a pin is set as input mode, it is still possible to write to the PORT for that pin; instead of producing an output, the value written to PORT will just change the pin between pullup and tri-state mode.

Known 2: A pin can be configured to toggle its output state along with the waveform generation module in a timer.

Question: When the DDR for a pin is configured as input, and that same pin is also configured to change state along with a timer, will the timer waveform effectively just rapidly switch the pin between tri-state and pullup modes? Or will the pin behave more reasonably, staying in tri-state/pullup according to the PORT value?

I guess the question could be restated as: Does the timer write to the PORT register in order to change the pin's state?

The only thing remotely relevant I could find in the datasheet is the following line:

  ...However, note that the Data Direction Register (DDR) bit corresponding to the [timer] pin must be set in order to enable the output driver.


texts:
Modes of a waveguide

As shown in the link above, they show how these modes work for various values of m, n, and p. However, where is the antenna/ source of radiation placed within the cavity?

From the picture I have shown the placement of 4 antennas refer to previous post here Visual understanding of EM fields within a rectangular metal container.. I'm am basically working backward in that I already have a cavity resonator and the frequency. I am simulating the modes in the container.

However, as noted in the comments and answer there will exist different modes of operation and I think if I am correct these modes will be the same for each antenna. But does this mean that these will all have the same EM field pattern within the container or will each antenna have it's on EM field pattern?

If there only existed one mode how will the EM field look inside the container for each of the 4 antennas?


texts: How to shorten the signal of a car horn?

texts:
I installed an aftermarket alarm/keyless entry in my wife's car. Everything works well, however, she's not happy with how long the car horn is triggered. I've tried to simulate some circuits to shorten the horn signal and haven't been successful. The alarm/keyless controller is sounding the horn by grounding the horn ground wire. Any help is greatly appreciated before I just cut the connection entirely and remove the alarm/keyless horn functionality.

EDIT: I added a diagram. The controller is seems to be just grounding the speaker connection when it needs to sound the horn.

simulate this circuit – Schematic created using CircuitLab


texts: Is there any alternative to the use of a ground wire?

texts:
Is there anything that can be used as an alternative to a traditional grounding pole that is buried in the ground?
Is it possible to use a lightbulb, a series of lightbulbs, or maybe an inductor in place of the connection to earth and eliminate the voltage by converting into something harmless like light?


texts: Sampling frequency required to detect peaks

texts:
I am processing a signal in the digital domain and I have to detect "peaks" in it, e.g. by finding local maxima formed by three consecutive values. (More sophisticated criteria could be used like setting a minimum peak height or peak width.)

If I know the behavior of the signal spectrum, is there a way to choose the sampling frequency to make sure not to miss a peak ? Is there theory about this ? Is there a relation to the Nyquist limit ?


texts:
I built a quadcopter. It had a very low total thrust/weight ratio, and after I added some components it doesn't fly any more, so I want to change its motors and propellers in order to increase thrust.

The total weight is around 90g; of this, 26g are the motors (20mm brushed motors).

Is it possible to generate [64 + motor weight]g of thrust with 4 brushed motors, each with a small propeller?
If it's possible, what kind of brushed motors and propellers should I use?

Here are my actual motors/propellers; I don't have technical data about them because I don't remember where they come from (I have the since a very long time).
Looking around on Google I found those images; in the motor image's site I found some information, but not very precise...


texts: Why aren't PCB mounted male mini USB connector parts common?

texts:
I'm looking to build a USB device that plugs directly into a mini USB OTG port - similar to those USB flash drives that can plug directly into smartphones with OTG-enabled micro USB ports.

I was thinking that the easiest way to build something like that is to have the connector soldered directly onto the PCB board - similar to how existing USB flash drives do it.

However, I'm not able to find a single supplier that sells PCB mounted male mini USB connectors. All my searches either come up with the female connector or a PCB mounted USB-A connector. The few I have found (from one supplier in China) aren't the USB OTG rounded type (although they would work).

Is there a reason why this is the case? Is it simply because it's not a commonly used part or am I simply not using the right search terms?


texts: Why All 1's used as a second input in decrement operation of ALU?

texts: Suppose the first four data inputs are X (X0, X1, X2, X3) and the second four data inputs are Y (Y0, Y1, Y2, Y3) in a 4-bit ALU. Why "All 1's" are used as an input for Y in the decrement operation of ALU?


texts: Is the current, Ids, through a MOSFET truly 0 when in the cutoff region?

texts:
I was testing a circuit using this circuit simulator and found that the nMOS transistor had a current of a few nanoamps running through it when it was in the "off" state. This was unexpected because I was taught (and found online) that the current through a MOSFET in the cutoff region was 0.

After a lot of thinking, I've decided that it seems odd that it would ever be exactly 0 since everything about a MOSFET varies in a continuous fashion. In the same way that there is no real point that the MOSFET changes from linear to saturation (as in, it does not suddenly switch to saturation as soon as , it's more of a transitional phase), it seems reasonable to assume that there is no real "off" state of a MOSFET, rather just a very low current linear region. But if that was true, surely I'd be able to find an equation which models the current in the cut-off region. I thought the linear region equation would work, but the results I get from that do not match those of the simulation.

The reason this is an issue for me is that it means the voltage output is dependent on the value of the resistor when in the off state.


texts: Why is the placement of the series resistor in data lines important?

texts:
It's a general question about series resistors in this type of application but I will use an example to make it easier to understand.

I have a LCD controller which uses an SDRAM, we can read a lot on the internet and it is common knowledge that you can put series resistors on numeric signals to increase the rising and falling time. For example, if my controller emits a clock in the direction of the SDRAM, the resistor has to be close to the controller. Since this resistor is meant to limitate the current which will flow through the parasitic capacitor at the input,I don't understand why the placement is important?

The question is : Why does this resistor has to be as close as possible to the source of the signal? What is the difference if it is close to the destination?


texts: Understanding the Texas Instruments CD4075 datasheet table

texts: I downloaded the CD4075 IC datasheet and I'm having trouble understanding the lines labelled "Output High (Source) Current" in the table below. The table shows current values relative to temperature and input voltage. Why are there 2 lines indicating current values for VDD = 5V? I realize that VO is different on both lines (4.6V and 2.5V), but isn't VO an output value (dependent on VDD and the High/Low value)? What determines which of the 2 lines different lines of values I'll get? What am I missing? Thanks in advance.


texts:
How can an op amp be prevented from going into saturation if the feedback is intermittently disconnected?

For example, in this circuit (simplified case of a real-life problem), the op amp acts as a current source to a load, but the load may be disconnected sometimes.

When the load is disconnected, the op amp output goes to the positive rail and the op amp goes into saturation.  When the load is reconnected, the op amp takes extra time to start regulating current) and then slews to the expected current set point.  Depending on the op amp, the time to recover from saturation may be very long.  The current through the load is the maximum possible for that time (ouch).

How can saturation be avoided in this case?  Are there some additional components to a feedback network that would do it?  Perhaps some kind of input or output clipping circuit?  Are there op-amps that would inherently limit their outputs (or inputs) some voltage away from the rails using built-in circuitry?


texts: How do I select long-lived microcontrollers for designs so we do not have to revamp our product if they stop making the chip?

texts:
I'm working for a small toy company who has all of their engineering/programming in China. They have had a few of their electronics product needing revamping because the microcontroller that the design was based on is no longer being manufactured. I think a lot of the Chinese vendors select Chinese chip manufacturers.

How do I go about selecting microcontrollers that have a lower risk of becoming decommissioned? What are some stable companies that are out there that produce microcontrollers for toys?

Do I look for PIC chips, Atmel, TI, etc. chips? These will probably have a higher cost associated with them, but if it will save money on revamping then the cost may be worth it.


texts:
I've got a vehicle that has a small bed with a dumping action controlled by an electric actuator. With the ignition on, power to the switch, you press up and the bed rises, you press down it goes down. When you let go of the switch, nothing happens, as it is designed. There is one relay to raise the bed and one relay to lower it. The vehicle is powered by two 12 volt car type batteries wired in parallel.

Here's what happened:

The batteries were dead so we jumped it using a 24 volt system designed to jump start 24 volt vehicles. We hooked up to the positive terminal on one battery and the negative on the other battery. We turned the ignition to the on position, trying to start the vehicle but it wouldn't start. We raised the bed to get at the engine, since it was hooked to the jumper we could raise it.

We left the vehicle charging for a few minutes, 10-15 minutes. When we came back, the bed was down and the actuator had torn itself apart but the motor of the actuator was still spinning, while no one was pressing the switch. We accidentally left the ignition switch in the "on" position but even after turning the ignition off, the actuator motor kept spinning.

My question is, is it possible that charging a 12 volt system with a 24 volt system shorted out the 1080p relay, making the connection on its own?

I know using the 24 volt jumper wasn't the healthiest idea but could it have sent enough current to the relay to arc it into turning it on?

I apologize for the simpleton terms but alas, I am no electrician so I am seeking advice from experts.


texts: Analog (POTS) telephone off-hook detection

texts:
With a single POTS telephone line and two or more handsets, when a call comes in, each handset can join in with the call.  This can sometimes be an issue when one user doesn't know the line is in use, and picks up the phone and starts dialing, or listens in to the original call.

Doing some research, I've found that there is a nominal 50v on the line in idle, the ringing is a 25hz wave superimposed on the 50v, and normal "off-hook" voltage is ~10v. Telephone Technical Information

What I'd like to do is detect the 10v and light an LED to give an indication of this "off-hook" call-in-progress state.

I suspect a simple circuit powered by a AA battery should be easy enough to do, but not sure how to go about it, nor have I found anything that does something similar that I can hack together.


texts: How is a zeta converter different from a buck-boost converter?

texts: Both the topologies have the same output equation, but zeta appears to be better. Why's that?


texts: Calculating the excact size of a PCB from a photo?

texts:
I have multiple photos of Graphics card PCBs. I would like to come up with a technique to calculate the exact size of them using Pictures.

The Picture is slightly distorted by the lens and not taken from a exact top- view angle.

The only size reference I have is that the part with the golden connector is 8.35 cm long.

Is there a way for me to calculate the exact (mm) width and lenght from this picture? If so, how?

I tried straightening the image using Photoshop but ended up modifying the actual size.


texts:
So I want to learn about batteries and the process of charging them.

As a project, I'm going to create a solar powered charger to charge a 9v NiMh battery with 175mah capacity.

I have a 15v solar panel which produces 0.32A of current. I will use this to charge my battery.

So here are my questions:

I read somewhere on the net that you should not charge a battery with a higher voltage than its capacity. So if I was to just connect the panel to the 9v battery, while it's generating 15v - boooooooom? I should use a 9v voltage regulator, right?
I also saw something on the net about only charging batteries with 10% of their current. Is this true? Should I be resisting my current to 17.5mah (for a 175mah battery)? If so, why?
15v is the peak voltage of the solar panel. It won't always be at this rate. Infact, it may even be lower than 9v. Does this mean that if the current battery charge produces more power than the solar panels, the charge will actually travel in the wrong direction and damage my panels? Should I be using a diode and/or something else to prevent this?
How do I work out the amount of hours required to fully charge the battery?
If something was to go wrong with this project, could I blow up my whole house and kill myself and invalidate my home insurance and make my family homeless? No seriously, is it safe?
Is there anything else I should know (saftey, good practices, etc etc)?


texts: Don't individual signal sources affect each other when using a summing amplifier?

texts:
I am studying the book Electric Circuits by Nilsson & Riedel. There I learned about "summing amplifiers" and how to derive equations by applying KCL at inverting input of the op amp.

I see that solving equations result in this "voltage adding" behavior but I couldn't stop myself asking "Doesn't any current flow between those signals (voltage sources whose voltage values to be added) and doesn't that change how the whole circuit operates?" I cannot intuitively see why this circuit works.

Until today, I always thought that it is not wise to connect batteries with different voltage values in parallel (even with some resistor in between) because then the one with the higher voltage will try to charge the other battery(ies). Further, I remember watching the battery management system video of GreatScott! and that also gives me a feeling that no voltage source should be connected to each other in such "simple" manner.

If you could explain (preferably, like I am five) to me this summing op amp, I want to make a crude analog summing calculator. Thank you for any help.


texts: How to determine the sign of passive elements in mesh analysis?

texts:
simulate this circuit – Schematic created using CircuitLab

The KVL equation for the right loop is:
$$-(I-gV_c)(\frac{10}{s}+10)-5I+V_s=0$$

But my professor use:
$$(I-gV_c)(\frac{10}{s}+10)+5I+V_s=0$$

Which sign convention is right?

If I solve for the transfer function $$H=\frac{V_0}{V_s}$$ using my equation $$-(I-gV_c)(\frac{10}{s}+10)-5I+V_s=0$$.

First I find an equation relating Vc to I: $$gV_c-I=\frac{sV_c}{10}$$. This is the Ohm law for the capacitor. s is Laplace variable. So $$V_c=\frac{10I}{10g-s}$$. Plug this into the my KVL equation $$(I-gV_c)(\frac{10}{s}+10)+5I=V_s$$, you get $$(I-\frac{10gI}{10g-s})(\frac{10}{s}+10)+5I=V_s$$. $$V_s=\frac{50gI-10I-15sI}{10g-s}$$.

I found an equation relating V0, the voltage at the top node, to I, this is basically the Ohm law for the center branch: $$gV_c-I_1=\frac{V_0}{\frac{10}{s}+10}$$ So $$V_0=I\frac{10+10s}{10g-s}$$.

Finally, we divide V0 by Vs:$$H=\frac{10+10s}{50g-10-15s}$$

Now using my professor's equation: $$(I-gV_c)(\frac{10}{s}+10)+5I+V_s=0$$. My professor has the same equation: $$V_0=I\frac{10+10s}{10g-s}$$ and $$V_c=\frac{10I}{10g-s}$$

Finally, my professor got: $$H=\frac{2(s+1)}{3s+2-10g}$$ The denominator is mine multiplied by -1.


texts: How to safely measure a 480VAC waveform with a DAQ?

texts:
I have a LabJack U6 Data Acquisition unit and would like to measure 12 (4 sets of 3 phase) 480VAC lines simultaneously at 600 samples/second. This would be used to evaluate a 480VAC 3phase, generator and utility system that has intermittent brown-out and black-out issues.  The voltage transducers in the existing hardware are not responding fast enough to determine which system or load is causing the issue. I have looked at other voltage transducers, but it seems they all average and have a relatively slow refresh rate (~250ms).

My initial thoughts on this would be to use a voltage divider of 100:1 to get the voltage lower, feed that to a linear optocoupler, then feed the isolated side of the optocoupler into the DAQ. Am I reinventing the wheel here?

I would prefer to find a manufactured device for this, but have had no luck. I'm a mechanical engineer so maybe I just don't know the correct vocabulary.


texts: How to design individual commutation for SCRs in H Bridge configuration?

texts:
I am designing a DC drive using SCRs in H bridge(with protection circuits). Triggering is done via an optocoupler.
Motor specifics:24V DC , 10 Amps
Supply specifics: 24 V DC, 15 Amps(with regulation, protection)
SCR switches are specifically preferred by the application for reliability and robustness in high temperature.So I have preferred them over MOSFETs and IGBTs for my H Bridge design.Moreover, the machine for which the drive is designed is structurally designed for SCRs, with heat sinks specifically for individual SCRs


texts: What is the purpose of the opamp in an integrator circuit?

texts: What is the exact role of opamp in an integrator circuit....?


texts: Power Arduino / Magnet valve with 12V solar panel

texts:
I bought the following solar panel: Link to eBay it has the following data:

Max. Power: 10 W
Open circuit voltage: 21 V
Ideal operating voltage: 18 V
Ideal operating current: 0,56 A
Short-circuit current: 0,61 A

Can I power the following two devices (or at least the valve)?

Arduino Nano: Arduino Website
Magnet valve: Amazon Link

I'm new to the work with solar modules and a bit confused about the "ideal operating voltage" of 21V and the 12V in the solar panel description / title?

Thank you!


texts:
I'm designing a project based on Atmega328P which uses QMatrix to drive 15 capacitive touch buttons.
Well, QMatrix sensors requires a couple of resistors and capacitors on sensor pins

Is any issue if some of the ISP pins are wired to capacitors and used as touch?

simulate this circuit – Schematic created using CircuitLab

This schematics shows typical wiring for a single QMatrix sensor, along with recomended component values. X/YA/YB/SMP are simply names QMatrix spec give to pins based on it's role.

The X line and YA line are not directly in eletrical contact on the button, though they form an interdigitated pattern which happens to form a capacitor


texts: Designing a relaxation oscillator using TL074

texts:
I've been trying to design a relaxation oscillator using a TL074 op-amp:

simulate this circuit – Schematic created using CircuitLab

For an ideal op-amp this should produce a square wave with frequency

$$ f = \frac{1}{2\ln(3)100\cdot 10^{-12}\cdot 200000} \approx  22.7kHz $$

When I run this on LTspice using TI's spice model I get a square wave with a 20.5kHz frequency.

My question is, how do I approach picking the correct capacitor/resistor values
when taking into account the real world characteristics of TL074 such that the circuit achieves a 22kHz frequency?


texts: What are the functional differences between a digital sampling 'scope and a digital spectrum analyzer?

texts:
I'm interested in measuring the spectral amplitudes / frequency content of RF frequencies up to 30 GHz. This can be done using a digital sampling oscilloscope (I'll call it a SO) with FFT or a digital spectrum analyzer (SA) [or a fantastic digital storage 'scope, noted below]. As I understand it, a SO samples the signals directly with known sample jitter, then recreates the signal using regression. A SA, on the other hand, first downconverts the high-frequency signal with a mixer, then samples. It would seem that a SA should deliver greater frequency resolution given comparable ADC sampling rates to the sampling oscilloscope.

What are the limits of functionality of each type? How is one better than the other at spectral analysis? (They both rely on the FFT, right?) What makes either expensive?

Unrelated POIs: 32 GHz Agilent, 120 GS/s Lecroy, 100 GS/s Tek, Gameboy SA.
edit: There seems to be some confusion between digital storage 'scopes (DSOs) and digital sampling oscilloscopes (what I called SOs) -- they are not the same, although they both sample digitally. I've also updated the question.


texts:
I can't understand the schematics of the 20pin slide switch SS44D04.

The schematics are in this pdf: http://www.lightcountry.com/download/slide/Slide%20Switch%20SS%20Series-11.pdf

It is the first one in the pdf.

Can anyone help me?


texts: Verilog Adding value in an always block. SIMPLE

texts:
module prizes(TESTSSD);
output reg [6:0]TESTSSD;
reg [1:0]equals;

always @(*) begin
    equals = equals + 1;
    case (equals)
        0: TESTSSD = 7'b0000001;
        1: TESTSSD = 7'b1001111;
        2: TESTSSD = 7'b0010010;
        3: TESTSSD = 7'b0000110;
        4: TESTSSD = 7'b1001100;
        default:TESTSSD = 7'b0000000;
    endcase
end
endmodule

When I run the code above, I get a messed up looking 2 on the seven segment display; it is missing the middle part. What am I doing wrong?


texts:
(This photo isn't mine!)
Why there is welding on some iron transformers' core?
is it only for holding the laminations together?
edit
can we repair or rewind this kind of transformers?


texts: Full wave diode bridge rectifier troubleshooting

texts:
I am trying to  make a full wave diode bridge rectifier, as the title suggests. I have a 120-12vac transformer that I'm using to supply the circuit. However, whenever I measure the voltage across the output of the bridge, I am still getting an AC signal. Whats even weirder is that I now get readings across the terminal on both DC and AC settings of my multimeter, and the VDC measurement is ~20V, which seems a bit odd... Anyways, I have no idea what is happening, so any suggestions would be fantastic.

simulate this circuit – Schematic created using CircuitLab


texts: How to run micro servo with ATmega 328 PU

texts:
When I use arduino board it works fine but when I try to put it on prototype breadboard it just freez and start humming.

For circuit I am using 5v regulator, duracel 9v battery, ZTT 16.0 mx resonator(for clock), and thats it. I test it with blink sketch it works find but when I tried it with servo it not working  poroperly...

Circuit look like this:

https://www.youtube.com/watch?v=KXFGgVN98J0&t=5m56s

Anyone know what can be a problem?

EDIT

When I power arduino just with 9v battery and use pin 9 from arduino board  it works so must be some problem with resonator?


texts: Decoder Simulation Results are incorrect

texts:
I was trying to design a simple address decoder using VHDL. The simulation results are wrong. I am sharing the code below for your reference.
In my design, I want to set a bit in my output corresponding to my input
entity Decoder is
  generic (
    NUM_BITS : integer :=3
    );
  Port (
    a : in STD_LOGIC_VECTOR (NUM_BITS -1 downto 0);
    ena : in STD_LOGIC;
    b : out STD_LOGIC_VECTOR ((2**NUM_BITS)-1 downto 0)
    );
end Decoder;

architecture Behavioral of Decoder is
begin
  process(ena)
  begin
    if(ena ='0') then
      b <= (others => '0');
    else
      b(to_integer(unsigned(a))) <= '1';
    end if;
  end process;
end Behavioral;

I am also sharing my simulation results for additional reference


texts: Cannot understand the attenuation in signal from PC to microcontroller(NI myRIO)

texts:
I am working on Active Noise Cancellation Project. I came across a problem, where the signal is getting attenuated as the audio bit depth changes from PC data to Microcontroller and I cannot understand it!
My circutit :I connected Audio Output(Head phones) of PC[which is supposed to be analog  signal] to Audio IN of NI myRIO 1900 device using AUX cable (two way 3.5mm jack cable). I have a pre-recorded signal(.wav) of sinusoidal waveform with Amplitude 1, Frequency 2kHz, 40000 Sample Rate, 80 Number of Samples, Bit depth( bits per sample) = 16.
Now, I just played .wav file using windows media player and tried to record the waveform on NI myRIO module. Surprisingly, I am getting an attenuation of the signal corresponding to the volume reduction in PC(not linear!!). Only I can see the waveform in microcontroller close to amplitude 1, when I increased the volume of the system to 100%. Please explain this !!

The ADC of NI myRIO has its Resolution as 12 bits but the audio Output(.wav file) is 16 bit data. I am expecting it does not have to matter except in quantization errors, as at the PC Audio Out, the audio data should be converted to analog and and again at the 'NI myRIO Audio In', this analog signal will be sampled! (please correct me if I am wrong !)
Another question is, I have tried the same with sinusoidal sound of Amplitude 2.5, now the audio signal is clipped off at 1V above and below -1V.

 ADC(NI myRIO) nominal range is 2.499V to -2.5V! Is it bacause of the bit depth conversion?
Please explain these things !TQ
EDIT: I am not converting either 16 bit digital data to 12 bit digital data neither 12 to 16 !! I happen to have a 16 bit audio data, when I played this through windows media player will get converted to analog signal at head phones terminal, and I am feeding this ANALOG Signal to an ADC of NI myRIO, which has 12 bit resolution.


texts:
I want to connect 8 strings of addressable LEDs so the strings do exactly the same thing at the same time.

All 8 strings start at the same point, but radiate outwards.

Would the controller be able to supply strong enough data pulse to drive 8 strings? Is there a maximum??


texts: What is this process called: Analog input, with a analog output with setpoint

texts:
What is this process called:

In my example the analog input represents line current. The analog output represents voltage. this is a closed loop with a target set point. The behavior would be that when the current level of the input is below the set point it would increase the output. When it went over the set point it would decrease the output.

My question is does this process have a name? I am told it is not a PID loop.


texts: UART no reply from BTM511 Bluetooth module

texts:
I am trying to connect a Bluetooth module (BTM511) with my Arduino.

In order to see that I can actually communicate with the module, I first try to just send AT<cr> to the module, where I should get an <cr,lf>OK<cr,lf> from the module, using the signal generation function of my Scanalogic2 analyzer. Pin 1 (in output mode) of the analyzer is connected to the module's RX, pin 4 (in input mode) connected to the module's TX.

Now, when I send the AT command, I never get a reply back. The TX line stays LOW all the time. I DO get it work when I start the analyzer, setting it to wait sending for a logic change on Pin 4 and then, while it is waiting, connecting Pin 3 (which is in input mode) to the TX as well. Then somehow the TX line goes HIGH, and the module reports back with the OK signal.

I hope the situation is clear. Could anybody explain to me what might be happening here, and what I am doing wrong?


texts: Correct equation for describing *exactly* the output of a current follower

texts:
In the textbook I use for teaching Instrumental Methods to Analytical Chemistry, there is a discussion about current follower circuits based upon the following figure:

After describing the ideal relationship between input current (ii) and output voltage (vo) they provide a "more exact relationship":

$$v_o=-R_f(i_i-i_b)\frac{A}{1+A} \tag {1}$$
$$v_0=-i_iR_f+i_bR_f\frac{v_o}{A} \tag {2}$$

Equation 1 can be found using a KVL/KCL analysis; however, it is unclear to me how one arrives at equation 2 and I am wondering if there is a typographical error in the textbook.

Additionally, one of the end of chapter problems mentions the percent relative error for a current follower circuit with a given open-loop gain, input bias current and feedback resistor if the input current is doubled.  I assume that the authors are looking for a comparison between the exact output defined by equation 1 to that of the ideal output \$v_o=-i_fR_f\$ but I have not found this terminology in another source so it is difficult to confirm my assumption.

Question 1 Is there a typo in equation 2 and if so, what it is?  If not, how does one get from equation 1 to equation 2?

Question 2 Is my assumption about the definition of percent relative error in the output correct?  Is there another source (text/website) that supports this definition?


texts:
I am trying to obtain v(t) (voltage across capacitor) and i(t) (current through inductor) for all t > 0;

simulate this circuit – Schematic created using CircuitLab

The textbook's solution uses source transformation on the current source in order to analyze the circuit with just 1 type of source for t > 0. I am wondering if it is possible to solve this circuit if I leave the current source as it is (no transformation).

I tried, but failed. At this point I am confused. Shouldn't I be able to solve this circuit without source transformation?

The steps to my approach are here. I am providing them for context. If you want to jump to my question, it's at the end of this post.

Consider the circuit for t < 0. Solve for the current through the inductor and voltaqe across resistor, i(0-), v(0-).
Voltage across capacitor cannot change simultaneously so v(0-) = v(0+). Same idea for the inductor, i(0-) = i(0+).
Next we calculate the Neper frequency. Since this is a series RLC circuit, it is R/(2*L) = 8/(2*5) = 0.8.
Then we calculate the natural response w0 = 1/(sqrt(LC)) = 1.
Since Neper Freq. < w0, we have an underdamped response.

Now here is the issue. We have a step response caused by the sources. The equation for the voltage for underdamped responses is of the form

v(t) = Vss + V(0)

Where Vss is the steady-state voltage of the circuit. HOWEVER, in this circuit we also have a current source. How should I deal with this current source if I don't want to turn it into a Voltage Source?


texts: 3 way selector switch to Push Button switch

texts:
I have 3 way video switcher which uses selector switch, is it possible to change this to momentary push button?

Project - I want watch 3 video feed from camera over 1 screen, with this selector button it works but i want use lighted push button which will give me idea which video to select.

Please bear with me, i am new learner in Electronics and don't know much, i am just trying to learn from Youtube and online tutorial. if you need more details let me know.


texts:
I am working on a data acquisition system project . I have used SMPS power supply and two pressure sensors(-5V to +5V input) and (0-20mV o/p)
my analog circuit consists of one op-amp(OP07) and one instrumentation amplifier(AD620)
Output of circuit after signal conditioning is given to 16 bit ADC (ads1115).
output of sensors show lot of fluctuation so i have used this low pass filter (Image attached)
if anyone could please explain how this filter works and what is GAIN of this filter it would be of immense help.

Thank you .


texts: Relationship between Zener diode voltage and knee voltage in forward bias? Also the resistance in forward bias

texts: Can somebody please help me establish a relationship between Zener diode voltage and knee voltage in forward bias? That is something where I could not find anywhere.


texts:
I found myself looking for a low-noise PNP transistor the other day.

I couldn't find any parametric searches that listed noise performance. Even from the transistor manufacturers. You can search by beta, \$V_{ceo}\$, and \$I_{c}MAX\$.  All these searches seem to return a table of every general-purpose part in the manufacturer's portfolio. Not helpful.

This circuit needs to have low-noise at audio frequencies.  RF transistors seems to be better characterized for noise, but they aren't necessarily low-noise at audio frequencies.

The best I have found was a forum thread at DIYaudio, but the recommendations tended to be old-school, even obsolete parts. I'm looking for a mass produced transistor in SOT-23 or smaller.

So recommendations are welcome, but I'd really like to see a selection tool or parametric search that includes this information.


texts: How electrical signals converted into Digital (binary 1 0)

texts:
I already ask this question in yahoo and in Microsoft........they say that : did I mean to say how to convert analog signals to digital signals.....and they suggest me the theory of AD converter
So, here is my question : the electricity that we use in our daily life to operate computers, refrigerators, televisions etc   =   ANALOG SIGNAL ?......because I want to know how this electricity is converted into digital signals

1. if electricity = analog signal, then ok I already got the answer(AD converter)

if electricity ≠ analog signal, then suggest me any book where from I learn this mechanism step by step to convert it to digital signals
if electricity ≠ analog signal, can I convert this electricity directly to digital, without converting it first to analog signal


texts:
I'm working on a LED project similar to the one in the picture, and I need to identify the black wire that the arrows are pointing to. What are those called?

Here is a picture:


texts: Faster charging of Lithium Polymer battery possible?

texts:
I am designing a system which needs to run for 3 minutes, then charge as quickly as possible, then run for 3 minutes, then charge as quickly as possible, and so on.

In order to reduce the charging time, I am using a very high capacity Lithium Polymer battery pack. Since these can charge at 1C, the higher the capacity the faster they can charge.

Also, since the capacity is so high, I am only using a few percent of the capacity. So the battery stays within 45% - 55% capacity for its whole life.

Question: What is the reason Lithium Polymer batteries are limited to 1C charging?

Question: If I'm charging a Lithium Polymer battery for about 90 seconds at 1C, taking it to no more than 3.8v, could I safely charge at more than 1C?


texts: Fan Speed Control - Speed Step Up Problem/Control Method

texts:
I am controlling the speed of a single phase, 120vac, centrifugal blower with a particle photon microcontroller, optocoupler, triac, and snubber circuit. I'm currently using phase control, but intend to try integral cycle/burst fire control next.

I am able to control the speed, and am measuring the output with a hot wire anemometer. Full on, the fan is blowing 28 cfm. I can barely reduce this down to 27, and then there is this large jump at the next microcontroller output level down to 12 cfm, from which I can step it accurately down 1 cfm at a time to 0. This meets my purposes, as I need around 27, 10, 5, 3, and 1 cfm at different times in my project.

However, the output level resulting in 12 cfm will, if left running for 5 minutes, eventually speed the fan up to the higher step of 27 cfm.

What is happening? Why is there this big step from 12 to 27, and why if slowed down to the lower step would the fan eventually ramp up to the higher step when run long enough?

I'm currently running a temperature test to make sure I'm not overheating the fan motor with speed control, but I don't have full results in yet.

My second question is about phase control vs. integral cycle control. I've seen competing information on both being better for motor speed control. Any advice on which will give better results?


texts: Calculating total torque of stepper motor to lift and rotate some weight

texts:
I am going to design a system that would be control remotely. The system consist of stepper motor and solid cylinder rod of about 30 inches long and needs to lift about 0.5 lb/0.223 kg mean up to 90\$^\circ\$ up and down in less than one second, maybe 0.7 sec.
Now I want to calculate torque and the total power required to do the above task. For the total torque I knew that the total torque would be equal to;

  \$t\$(total)=\$t\$(require to lift the weight of 0.5lb)+\$t\$(torque required to
  rotate the rod up to 90\$^\circ\$ up or down);

How can I calculate \$t=Ia\$
where \$I\$=moment of inertia=\$\frac{MR^2}{2}\$ for solid cylinder? I am confused how to calculate the angular acceleration \$t=Ia\$.
Any help would be appreciated.

The rod is hollow from inside.
Here is the key idea (time to \$\frac{\pi}{2}\$ or \$90^\circ\$. \$90^\circ\$ is missing in the diagram)


texts: What is a 3.6V / 4.2V LiPo cell? (as opposed to 3.6/4.1 or 3.7/4.2)

texts:
I am familiar with 3.6V/4.1V and 3.7V/4.2V LiPo cells.  I have a bunch of cells rated at 3.6V/4.2V.  What's up with the odd rating?  Can these be safely charged with a 4.2V charger IC such as the MCP73831?

This is all the info I have on the cells:

Models: Sony NP-FD1, NP-FT1, or NP-BD1
Nominal voltage: 3.6V
Maximum charge voltage: DC 4.2 V
Maximum charge current: 1.24 A
Typical capacity: 2.4Wh (680mAh)

(All three models have the same form factor and power specs but different keying; thanks Sony)

Addendum

The battery voltage reads as 4.20V after being fully charged using the original charger.  I opened up the charger and the charge control is being done by an M34501E4FP microcontroller so no clues there.


texts:
I am looking for a algorithm that can detect the rate of symbols in a base-band signal.

The Gardner method is a way to cancel out the timing drift and synchronize the receiver to sender when the symbol rate (number of samples per symbol) is known. The MATLAB also provides a package which implements Gardner method.

But what if we don't know the symbol rate? I found some proposed methods like using cyclostationary properties of signals.

Is there any package/implementation of these methods (or any other method) in MATLAB or C symbol rate estimation?

Update #1:

This is a simple implementation which uses cyclostationary properties to estimate baud rate, but it is not suitable for large inputs like wave files.

Update #2:

After demodulating and filtering the received signal I have a basedband signal like:

Symbols are encoded as different shapes in this signal (e.g. different levels of voltage if the sender uses square shape filter).
As we can see, the highest frequency in this signal is not the symbol-rate.

I am not seeking for a new solution/idea to estimate symbol rate. I am looking for an implementation of a known method (like cyclostationary-based or wavelet-based methods) for symbol rate estimation.


texts:
Has anybody experienced using the Invensense IMU3000 gyroscope with some microcontroller?

The hardware comes with a really good library integrating full control of its features. This library is structured in 3 different layers, the bottom one is the one that implements the communication with the chip itself. The vendor provides this layer for using the IMU3000 with an adapter board in WindowsXP. Basically, what I need to do (and what is suggested in the application note) is rewrite this layer to use the whole library with my PIC (I2C communication). After that, I can just use the library (this is what it's said in the application note).

I am trying to build the IMU library in Visual Studio 2005 (the project was originally made this way) for a PIC but I am stuck with the dependencies..

Alternatively, I can compile the .lib with the PIC IDE, but.. is it possible=

Any hint, even with other platforms, would help!

Thank you all!

P.S. Unfortunately I cannot find the DS online.. just after you install the package you find it.


texts:
Title says it all: can an opto-isolated input be analog or are they intrinsically digital?

Why: I am looking to purchase a relay control board and am deciding between a few options.

Here is my primary option, however I need 5 analog inputs and this one states that it has opto-isolated inputs. Could those be analog?

EDIT: Page 6 of the user manual has each opto-isolated line connected to a digital and an analog input pin. Does this mean it can accept analog (voltage) inputs?


texts: Howe to do a sam3x single channel ADC conversion

texts:
I have a Sam3x (Arduino Due hardware, but I don't use the Arduino IDE or libraries, and I don't use the Atmel libraries, just the register interface in sam.h).

I have multiple pins configures as ADC pins. How can I do an AD conversion on one of these pins? The way the relevant datasheet chapter is written seems to suppose that I always want to do a conversion of ALL pins that are configured as input.

Datasheet http://www.atmel.com/images/atmel-11057-32-bit-cortex-m3-microcontroller-sam3x-sam3a_datasheet.pdf ADC starts at page 1317.


texts:
I have old Hewlet Packard 33120A function generator (it should be the same type as Agilent 33120A) and I would like to control it with MCU (ATMega). The generator has RS232 and use SCPI commands.

I made simple RS232 to TTL converter with MAX232, just with RX and TX lines. According to User's guide (chapter 4, section DTR/DSR Handshake Protocol) I tied the DSR to logic TRUE (negative voltage) and DTR is not connected. This configuration should disabled hardware handshake.

Now, I can connect converter to MCU or to computer. For my first experiment I used computer and this Python script:

import serial, sys, time

if __name__ == '__main__':
        if len(sys.argv) < 2:
                print 'Usage: %s <serial_port>' % sys.argv[0]
                sys.exit(1)

        s = serial.Serial(port=sys.argv[1], baudrate=2400, bytesize=8, parity='N', stopbits=2, timeout=None, xonxoff=0, rtscts=0)

        time.sleep(0.5)
        s.write('\n*CLS\n')
        time.sleep(0.5)
        s.write('SYST:REM\n')
        time.sleep(0.5)
        s.write('APPL:SIN 30E+3, 0.1\n')

        s.close()

This works without any problem. The generator set its output to 30kHz as expected. The problem is, when I try to read some response from generator. For example, this should return device name:

        s.write('*IDN?\n')
        print s.realine()

I am pretty sure the response is stored in generator's output buffer but no data are actually transmitted.

Is there any command to trigger transmitting data from buffer? Or do I need enable hardware handshake?

Is there anyone who has this generator? Do you use it with RS232 and SCPI?


texts: How to waterproof electronics for an underwater project?

texts: I am building a project that has to do with underwater and I am having trouble waterproofing the electronic and the depth is about 15-20 feet. How will I assure that the electronic will be waterproof at that depth. Thank you


texts: Bypass capacitor in common emitter input impedance question

texts:
I can't seem to sort out how the bypass capacitor and the input impedance interact on this.  I designed this simple CE amplifier stage (it doesn't do much of anything and it's mostly an example problem).  I computed the input impedance using 10k||50k||hFE(re) and got 1408 ohms for Zin.  [I used 150 for beta.]
I simply don't know how to find out if my calculations are correct.  I imagine that I can't simply apply Ohm's Law to look to see if I'm getting the correct current through my source resistance (100 ohms), right?  When I run the sim as pictured with a 20mV peak-to-peak signal input, that source resistor eats up 8 uA (peak-to-peak), but of course this changes quite a bit as I adjust the cap.  Shouldn't my expression for Zin take that into account the value of the capacitor or its reactance at 1kHz somehow?
Does anyone have a clear source that will describe a good sizing method for the bypass capacitor if I'm building something to amplify 20Hz-20kHz?  Also, can anyone tell me whether my 1408 ohms figure for Zin looks correct?
In case it's helpful, this is simply a learning circuit for me -- no real-world application and a lot of the component values made up to practice.  My interest down the road will be in audio, so perhaps imagine this as a stage in an instrument amplifier.


texts: Summing Amplifier - Resistor at non-inverting input terminal

texts: This signal conditional circuit outputs the sum of five 76Ohm output sensors in the 10mV range and the voltage gains are 10,15,20,25,30. Could someone please explain to me why do we need a resistor at the non-inverting terminal of the summer amplifier and why do we need an inverting amplifier connected to the summing amplifier? I think it is because the output voltage of the summer opamp is negative but I do not know if that's the reason to add an inverting opamp to the circuit.


texts: What is the "C rating" of a LiPo battery determined by?

texts: In a LiPo battery, we find the "C rating" to be the maximum discharge rate (current draw) in terms of C (the capacity of the battery divided by one hour). But, what determines this value? Does it have something to do with its inside chemistry? Is it only limited by the protection circuit that comes with it? Is it just roughly calculated by testing which current it blows up at?


texts:
I have a non invasive current sensor SCT 013-030 and I connected it to an AVR mcu using this circuit below (circuit 1).

Circuit 1.

simulate this circuit – Schematic created using CircuitLab

Circuit 2.

simulate this circuit

The questions are:

What does the C1 on the circuit 1 do? What's its purpose on the circuit?
What's the difference about circuit 2? Is it better? Why someone would chose circuit 2 instead of circuit 1?

I understand that: Circuit 1 is way cheaper. Circuit 2 provides much more safety to microcontroller adc input and it's got low output impedance. Also the phase of the signal is inverted which I think it doesn't bother much.
Am I missing something more important than that?


texts: I am currently communicating between two microcontrollers using a single pin and the LIN protocol over a short distance of 0.2m. Now I would like to extend the distance up to 5m by differentially driving the communication (using a RS485 or 232 transceiver etc.). It is not possible to change any aspect of the current design so I am thinking of attaching a PCB to the microcontrollers at each end and communicate between the PCBs differentially.  Is anything like the attached image possible? The difficulty I am having is in splitting the signal from single to differential as most transceivers require an Rx and Tx. This would be fine If I could split the signal before the transceiver.


texts: STM32 L4 HAL_FLASH Writes in one function but not another

texts:
I am working with an STM32 L476RG evaluation board on a project. The goal currently is to utilize STM's mass storage library to write data to flash over USB. I've got the USB library working properly (simply reading and writing data from/to RAM as a start), but I've encountered a strange problem when using flash.

If I write to the flash in the STORAGE_Init_FS function (Using HAL_FLASH_Program(....)), I can write to the flash just fine. I clear the page, write arbitrary data to it, and it appears in the memory view of the debugger.

However, if I try to do the exact same thing in STORAGE_Write_FS (tried with line-for-line, the same code), then the flash operation returns an error and doesn't ever write any data.

Here are the relevant code portions:

{
  /* USER CODE BEGIN 2 */
    USB_Flash_Init();
  return (USBD_OK);
  /* USER CODE END 2 */
}

HAL_StatusTypeDef USB_Flash_Init() {
    __HAL_RCC_SYSCFG_CLK_ENABLE();
    __HAL_RCC_FLASH_CLK_ENABLE();
    /* Clear flash flags */
    HAL_FLASH_Unlock();
    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
    HAL_FLASH_Lock();

    HAL_FLASH_Unlock();
    HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, 0x8080000, 0x0001);
    HAL_FLASH_Lock();
    return HAL_OK;
}

In the above code, the data 0x0001 is properly written to memory address 0x8080000. (The erase call is not there, but the page has been erased).

However, in the below function,

int8_t STORAGE_Write_FS(uint8_t lun, uint8_t *buf, uint32_t blk_addr, uint16_t blk_len)
{
  /* USER CODE BEGIN 7 */
    __HAL_RCC_SYSCFG_CLK_ENABLE();
    __HAL_RCC_FLASH_CLK_ENABLE();
    HAL_FLASH_Unlock();
    __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
    HAL_FLASH_Lock();
    HAL_FLASH_Unlock();
    FLASH_PageErase(0, FLASH_BANK_2);
    HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, 0x8080000, 0x0001);
    FLASH_PageErase(0, FLASH_BANK_2);
    HAL_FLASH_Lock();
  return (USBD_OK);
  /* USER CODE END 7 */
}

The data gets properly wiped (viewing the memory address through the debugger), but then never written, it remains 0xFFFFFFFF. I know some of the init stuff had already been done, but I wanted to be certain it wasn't the cause so I threw it in there as well.
The only thing I can really think of would be the stack potentially not having enough space (unlikely with the massive amount of memory this thing has). In order to verify this wasn't the cause, I tried both taking my 2k buffer (not shown here) out of the function to no longer be a local variable, and increasing the stack and heap sizes to 0x4096 (excessive) in the RAM.ld.

Neither changed the behavior. Anyone I've spoken to has been at a loss as to the cause of this. What could I be doing wrong?

I do get two errors when I check HAL_FLASH_CheckError() (might not be the exact function name), 0xA0, which corresponds to HAL_FLASH_ERROR_PGS and HAL_FLASH_ERROR_PGA, programming sequence and programming alignment errors respectively. I'm not certain these errors are relevant, considering the actual function calls and setup are identical, only the scope is different.

If anyone has any advice, I'd be glad to hear it! Hopefully I'm just missing some control register or bit somewhere.


texts:
A long time ago I understood this, but right now it totally escapes me.

Taking an audio amplifier for example. Say it drives a speaker which is 8 ohms at all frequencies. Taking the amplifier as a Thevenin equivalent. If the Thevenin resistance is zero ohms, that would drive the speaker at the highest voltage, hence highest current and power?


texts: What kind of FPC is this, and what should I couple it with?

texts:
I'm working with these planetary geared micro stepper motors which come without a datasheet or any information from the sellers. I'm having a trouble figuring out how I should mate the FPC cable, can anyone tell me what kind of THT or SMD socket it'd fit?
Edit: This is for an academic research paper, and a researcher wants to use this motor because of it's small size. I know using ebay for component procurement is a horrid thing.


texts: Is this a standard cable? (USB Type A + unknown)

texts:
I have a cable that I cannot match with any device. My question is whether this is a standard cable, or rather a proprietary invention.
On one side there is a standard USB Type A male connector.

The other side is the one I cannot recognize. It looks like an electrical connector (230V, Europe, often used to connect some "mobile radios" (usually also powered by batteries)), such as this one: https://imgur.com/a/D2iyYc2. It is smaller, enforces polarity, and is obviously not for 230V.
(the scale on the images below is in centimeters)


texts:
I am playing around with real implementation of basic logic schemes from transistors.

Could you suggest any compact implementations of T-trigger? Obviously, classic "CMOS" way eats way too many.

Other nonlinear elements are allowed (like tunnel diodes), diodes and other components does not counts.

I will need this to implement binary counter.


texts: Visible Light Communication Signal Transmission

texts: Im working on a VLC project where Ill need to transmit encoded data through an LED using an Arduino board to a photodiode receiver that somehow demodulates the signal and extracts the data. Im looking for a transmission rate of atleast 1Kbps where anything higher is bonus points. The problem is there will be ambient light present and my LED cant be a distinct red or green color to resemble a common lighting fixture. So one solution Im considering is to modulate the LED at two set frequencies, say 30kHz and 35kHz, where and connect the photodiode to a bandpass filter designed for 35kHz so that the output of the filter is a logic one when my LED is modulated at 35kHz and a logic 0 when its mod at 30kHz(this is simplified, id do something where a logic 1 is a certain duration of 35 followed by a certain duration of 30). Pretty much this idea is modeled from the NEC protocol used for remote controls. Id like to know if this setup would work before I start putting it together as I cant find any simulator that reasonably simulates LED/Photodiode interactions. Also, since im a beginner and im sure you all have wonderful ideas, is there anything I can do better or differently? Any input would be golden!


texts: If I am discharging a battery at 30% of its energy and then charging it at 0.8C. How long will it take to be completely charged?

texts:
Suppose that I have a lead acid battery that:

Can (and will) be discharged by using 70% of its energy (energy left is 30%)
When the battery is at 30%, I will recharge it at 0.8C.

How long will the battery need to be completely charged?

My reasoning would be the following:
$$V_n = 100 V$$
$$Capacity = 50Ah$$

Then the (theoretical) energy that the battery can deliver is 100*50=5 kWh. If I use 70% of it then that 70% is 3.5 kWh. To get the battery back to its original state (neglecting charging efficiency) I need to put 3.5 kWh back into the battery. If I recharge it at 0.8C=40Ah assuming 40 A of current through the battery then
$$t=3.5kWh/(100 V *40 A)=3150 s = 52.5 minutes$$

Bonus point: What does recharging a battery at 0.8C means? 0.8C is a measure of capacity but in practice I'll have a current running through the battery terminals. How do I reconcile the two?


texts: Best practice for earth connections on isolated equipment

texts:
We have a piece of equipment that runs on 230VAC being shipped to the USA (110VAC).
We are shipping it with an isolation transformer (5kW)
The input is E,N,L and the output is neutral and live (isolated).
What do we do with the earth connection on the equipment?

(a) Leave earth unconnected

(b) Connect it to 230VAC neutral at the transformer

(c) Connect it to 110VAC earth (ie the building's earth)

Additional comment: There is likely to be local mains driven equipment connected to our box eg computers


texts: How to uplad program into Arduino Nano Clone with CH340?

texts:
I've started to build a Arduino Nano with CH340g using this schematic:

Which use the CH340 chip :

With one difference, I've use SPI pin to program the MCU.
I've uploaded OptiBoot to Atmega328 and then I've set BLB1 to lock LPM and SPM in the boot section and I've set the BOOTRST fuse to One.
All the process below was also done in Win7 with installed driver from the original IC website.
When the board connects to UBUNTU the computer recognize the device as : QinHeng Electronics HL-340 USB-Serial adapter and when I tried to upload the code, It uploads the code(famous blink) with Arduino IDE(set to use Arduino Nano) for a few times(If i get lucky) and the it stops.
The other strange thing is when I use Arduino bootloader to print something in serial, I can see it in terminal through USB but when
I upload the hex file of echo program:
#define F_CPU 16000000UL
#include<avr/io.h>

#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU/(USART_BAUDRATE*16UL)))-1)

int main(void){
 char recieved_byte;

 UCSR0B |= (1<<RXEN0)  | (1<<TXEN0);
 UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01);
 UBRR0H  = (BAUD_PRESCALE >> 8);
 UBRR0L  = BAUD_PRESCALE;

    for(;;){
  // wait until a byte is ready to read
  while( ( UCSR0A & ( 1 << RXC0 ) ) == 0 ){}

  // grab the byte from the serial port
  recieved_byte = UDR0;

  // wait until the port is ready to be written to
  while( ( UCSR0A & ( 1 << UDRE0 ) ) == 0 ){}

  // write the byte to the serial port
  UDR0 = recieved_byte;
    }
    return 0;   /* never reached */
}

I couldn't communicate(It doesn't echo back)!
How can I fix this? any help would be appreciated.
PS:
My goal is not to build an Arduino and I want to communicate to my MCU through USB and I've thought it would be good start to build an Arduino to test super cheap CH340 on the already tested schematic!
UPDATE1:
There are reported problem with ch340 in Arduino boards but non of those solutions helps! I guess if ch340g was that good, It would became  standard USB serial chip in all devices with its low price.
UPDATE2:
I've manage to make MCU echo back(without Arduino boot loader) correctly by tuning parameters(F_CPU and BAUD_PRESCALE) but self programming is seems far fetch!


texts:
I'm building a project based on ltc3108, Linear Technologies IC, and the Peltier cells, TEC 12706. The basic idea is to recharge a battery by the temperature difference between the body-skin and the room.
The problem is the current, how many cells do I need to have a proper current?
Is it best to connect them in series or in parallel?

Thanks :-)


texts:
I have a client that has an equipement in an area where sometimes electricity goes on and off many times a minute , and it can dammage his equipement, so he asked me for protection system that works as following:

1- the system needs to starts with an ON button (on button or push button or whatever)

2- if the power goes off the system will shutdown (that is normal)

3- But if the power goes on again, the system will not start automaticly

4- it needs some sort of timer, that will check if the electrity was back for 5 mins for example without any cut again to start the system

5- and of corse an OFF Button.

NB : I DONT THINK MY CLIENT CAN AFFORD A SMART RELAY.

Thank you


texts: Arduino UNO R3 Plus Digital Pins Overused?

texts:
I have an Arduino UNO R3 Plus with 14 digital pins, but they don't function well. Or maybe they do, but the point is, I think I am overusing them. I have an LCD connected to ports 13-7, 4 LED lights connected to 5-2 and 2 buttons connected to 0-1. But I'm only using one button, so it is technically 1 button connected to port 1. The LED + button is an LED game, and I'm  trying to make the LCD screen a counter for it. The LCD and and the LED "power cords" share the same breadboard segments, the LED is the one going up to the 5V power pin. The problem is that I can only make one work at a time, so I don't know if its the programming or the hardware. So please tell me how I can reprogram/rewire this (or else explain why it is impossible).

My code:

int currentLED = 2;
int delayValue = 200;
int numberShown = 0;

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(13, 12, 10, 9, 8, 7);

void setup() {
    pinMode(1, INPUT); //Button
    pinMode(2, OUTPUT); //White LED
    pinMode(3, OUTPUT); //Yellow LED
    pinMode(4, OUTPUT); //Green LED
    pinMode(5, OUTPUT); //RED LED
    // set up the LCD's number of columns and rows:
    lcd.begin(16, 2);
    // Print a message to the LCD.
    lcd.print("hello, world!");
}

int checkInput() {
  if(digitalRead(1)==0) {
    return 1;
  } else {
    return 0;
  }
}

}
void loop(){

// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 1);
// print the number of seconds since reset:
lcd.print(millis()/1000);

  if(digitalRead(1) == 0){
    if(currentLED == 4) {
      digitalWrite(4, HIGH);
      delay(200);
      digitalWrite(4, LOW);
      delay(200);
      digitalWrite(4, HIGH);
      delay(200);
      digitalWrite(4, LOW);
      delay(200);
      delayValue = delayValue - 10;
    } else {
      digitalWrite(currentLED, HIGH);
      delay(200);
      digitalWrite(currentLED, LOW);
      delay(200);
      digitalWrite(currentLED, HIGH);
      delay(200);
      digitalWrite(currentLED, LOW);
      delay(200);
    }
  }
  digitalWrite(currentLED, HIGH);
  delay(delayValue);
  digitalWrite(currentLED, LOW);
  delay(delayValue);
  currentLED = currentLED + 1;
  if(currentLED > 5) {
    currentLED = 2;
  }
}


texts: How to calculate small signal parameter for a BJT when early voltage is taken into consideration?

texts:
I have proved one formula of

output impedance
ro = (Va+Vce)/Ic = Va/Ic'

where Ic is collector current and Ic' is collector current neglecting early effect.

But reading from standard texts other formulas are diverging like for
gm{trans-conductance} = Ic/Vt

is formula given in Razavi, Neamen .

But I am getting

gm=β/rb = Ic'/Vt

where rb is base emitter resistance and β is common emitter current gain.

Am I doing some mistake or its rather approximation the books are taking and in later case plz comment if the approximation is rather universally valid.


texts:
I bought a development board from Matrix Multimedia, HP488(datasheet), but I dont know why I fail with a small program.

The program must flash a led with a delay (4 sec) using TMR0.
So, from my calculations, using formula :
Freq. out = Freq. osc / [prescaler * (256 - TMR0) * count]
The prescaler is 1 : 256; TMR0 is 0, anf the frequency oscilator is 4Mhz (osccon = 0b01100000)
An instruction is executed in 4 clock cycles. So the frequency clock is 4Mhz / 4 = 1Mhz.
count = 61.
I use sourceBoost IDE, and the compiler is BoostC.

Look my code :

#include<system.h>
unsigned int counter = 0;

void Delay(void)
{
  if(intcon & 2)                   // check if TMR0IF is set
   {
      clear_bit( intcon, 2 );     // if TMR0IF is set, clear this bit
      counter = counter + 1;      // increments the counter
      if(counter == 61)
        {
           counter = 0;
           portb = ~portb;        // flash the Led 0 of Port B
        }
   }
}

void main(void)
{
    trisb = 0x00;                    // set all pins of Port B as output
    portb = 0x01;                    // RB0 is high
    tmr0 = 0;                        // the value of TMR0 register is zero.
    cmcon = 0x07;                    // comparators is off.
    option_reg = 0b00000111;         // prescaler is assigned to the WDT, prescaler 1:256
    intcon = 0b10100000;             // GIE - enable, TMR0IE - enable
    while(1)
    {   }
}

The program compiles fine, upload fine, but dont show me the led flashing.
What I am doing wrong ? Are there any configuration settings that I am not aware of ?


texts: I've got some spare phone batteries and I'd like to be able to charge them without a phone. However, it seems like I can only charge it with my phone: I attach + pin to 5V DC, - pin to GND, the third, middle pin disconnected. My battery charges only if it's in a telephone, why? How can I charge it? Do I need to connect somethin to the middle pin? The battery is Samsung Galaxy Mini 2's own.


texts: use transistor to switch on/off a window alarm

texts:
basically I am follow the Schematic in this link- https://stackoverflow.com/questions/14833999/arduino-switch-control ,

I can get the transistor to switch on/off a motor, but now instead of a motor, I try to switch on/off a window alarm similar to this one https://www.amazon.com/Window-Door-Alarm-Kit-Pack/dp/B007RUGANC , but the problem is the alarm is already on even there is no supplied base current, please advise how to resolve this.


texts: Is it possible to combine two 8 bits DACs together to create a 16 bit DAC, one byte of the 16 bit word shall be sent to each of them

texts:
For two DACs, one being sent D0-D7 and the other being sent D8-D15, with power supply being 5V, if 5V is added to output of 2nd DAC and then the two DAC outputs are summed, should result in a 16 bit DAC made up of two 8 bit DACs.

The only problem is that if the second DAC has 0x00 input then the 5V addition needs to be cancelled out which I am not sure how to do. The summing can be done by summing amplifier. The circuit need only work upto few 10s of kHz.

Is there something fundamentally wrong with this idea?


texts:
I ran a parameter extraction program and its output is expected to be run under HSPICE. It looks similar to this:

.SUBCKT DAC BIT0 BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7

C1234 BIT0:5 0 1e-12
C4321 BIT0:6 0 5e-12

.ENDS

Why is there a : in the node names as in BIT0:5 and BIT0:6. What are they used for? Do they refer to the same node?


texts:
I need a tiny PCB for a tiny IC. Is this something I have to design in autocad? Do I have to go to a shop to print it for me?

Ultimately I want to be able to flux solder the IC on the tiny board so that I can plug it into my prototype where I need it. I would use a breakout accelerometer on Amazon but they are too big for what I need them for.

Ideas?


texts: PSRAM: First operation bogus, later operations fine

texts:
I have a PSRAM driven by an STM32F2 in the default asynchronous mode. The PSRAM works fine except for the very first read or write operation.

After the first read or write operation (which produces bugus results), all the read/write operations behave as expected. The address of the first read or write operation does not change things.

I have tried inserting a one second delay between the SRAM initialisation and the first read or write operation, but that did not help.

What could I be causing this problem?


texts: Two Wire Cable: Two Inputs to one output

texts:
[partially reposting from Music Stack Exchange (I was told to go here)]

NOVICE QUESTION

My question is simple: If I open up a guitar cable (which uses two inner wires: signal and ground) and connect the signal outputs and grounds together, could I connect that to another cable, therefore get a 2 inputs connected to one output?

My idea is this:

simulate this circuit – Schematic created using CircuitLab

Any ideas? I am trying to be able to plug in 2 inputs and send those to a single output. If this doesn't work, what should I try? Any help is appreciated


texts: Shortening a long antenna with a capacitance

texts:
In many circumstances it is not possible to make a dipole antenna that has the optimum length of \$\lambda/2\$ (or monopole with ground plane of length \$\lambda/4\$). Car antennas are for example shorter than they should be, which would result in an antenna that behaves like a capacitive load. An inductor is added to counteract this, basically lengthening the antenna electrically.

Now, is it possible to reverse this to electrically shorten an antenna, which is much longer than \$\lambda/2\$? It would behave like an inductive load, so adding a capacitance would make it resonant by analogy.

It seems to me that from an electrical standpoint, it there shouldn't be a difference between using a \$\lambda/2\$ dipole and a much longer antenna that has been "shortened" by an appropriate capacitor, other than the introduction of the real parts of both the antenna and capacitor resistance. What am I missing here, or under what circumstances can such an antenna tuning work?


texts: Is there a proper way to enable a digital counter?

texts:
I'm asking this because, while learning about how counters work, I read that one can add an input that enables or disables the counter depending on its logical value. Now, my first instinct would have been to AND the enable input with the clock signal, so that the Flip Flops of the counter are only clocked when the counter is enabled, like so

However, pretty much every source that I have found that teaches the principles of counters present this kind of circuit instead

Here, making enable low inhibits the inpts of all JKs so that they hold their state.

I understand that, from a purely logical standpoint, those two solutions are equivalent (in that they achieve the same goal), but I am curious to know why the second one is almost allways presented, and the first almost never (as far as I have seen at least).
To me the first one seems more instictive, at least it's the one that came to my mind immediately.
But more importantly, it also seems to be simpler to implement in practice since it only requires one additional gate, whereas the second one requires an amount that grows with the width of the counter.

Considering that, is there a practical reason to favour the second circuit over the first one?
I know almost nothing of the physical, electrical, side of digital designs (i.e. things that have to do with stray capacitance or inductance, or phenomenons that occur at high or low frequencies, component wear, etc), so if something is going over my head I'm guessing it has to do with that.


texts: Calculating load regulation in this zener diode circuit

texts:
I'm trying to find a good method to calculate the following two values of the circuit below:

$$\bigg(\frac{dV_L}{dV_S}\bigg)_{i_L=constant}=?$$
$$\bigg(\frac{dV_L}{di_L}\bigg)_{V_s=constant}=?\\ \\$$

I'm not sure if my method is correct, but here is what I did for the first one(KCL on node above Rz):

$$\frac{V_s-V_L}{R}=\frac{V_L-5}{R_z}+i_L\\=>(R+R_z)V_L=R_zV_s+5R_L-RR_zi_L\space \space (1)$$

Taking the derivative of VL with respect to Vs and handling iL as a constant, I get the result:

$$\bigg(\frac{dV_L}{dV_S}\bigg)_{i_L=constant}=\frac{R_z}{R+R_z}$$

However (!), if I'd written the last term in KCL like this :

$$\frac{V_s-V_L}{R}=\frac{V_L-5}{R_z}+\frac{V_L}{R_L}$$

I would get a different result. Why? How do I know if I have the correct equation to take the derivative?

Now for the second part.

Why can't this derivative be equal to RL? I can start from equation (1) and get the correct result but again,Ohm's equation is valid as well. How do I know what equation to start from? Each one leads to a different result. I've obviously understood something wrong.


texts: Netduino + Mosfet Driver + PMDC Motor = Magic Smoke

texts:
I have an old treadmill motor:

  Motor Specs:

  Permanent Magnet DC Motor

  Electrical Rating:
      @130vdc  2.5hp  6700rpm 18amps
      Continuous Duty  @95vdc 1.5 hp

I need a speed controlled drive circuit for it. I didn't want to spend $60-$100 on what seemed like a pretty trivial task. Create a PWM signal, run it through a MOSFET driver, drive my higher voltage with this MOSFET and thus PWM ~90vdc to my motor and control it's speed via a POT.

Well in theory it all worked. I polled a POT from my Netduino, giving me control of a PWM output signal. I fed this signal to a MOSFET Driver IC (tc4452), which would in turn drive my MOSFET(s). The MOSFET(s) would thus be switching the higher voltage.

FETs- http://pdf1.alldatasheet.com/datasheet-pdf/view/43633/SHINDENGEN/2SK2196.html
Driver - http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en025917

Tested it out with a lamp(no scope at home) so I could see if I was on the right track, and it dimmed and brightened (thus modulated the 90vdc) just as expected. However, it did not run my motor. I hooked it all up, everything was cool until I started moving the POT higher and the motor started reacting and then FIREWORKS! My MOSFET was toast. I tried placing 2 parallel thinking it could possibly be too much current and this might divide it, but no dice. More fireworks! :) I always wear my safety gear when toying with this kind of energy though, so no worries. Just frustrating.

So rather than wasting anymore components I would like to ask some expert opinions on the matter. Are my FETs just not beefy enough for this? or is there a possibility that the FET driver isn't actually saturating the FET properly? I would like to hear any opinions really. I just don't wish to waste money on beefier FETS if I'm just not driving the type I have with enough juice, or if I'm just overlooking something really stupid.

Thanks a ton!


texts: unable to understand write policy in Cache memory

texts: I am studying write policies in cache memory ( for first time ). I am able to understand the 'write-through' but i am not able to understand 'write back' and the problems associated with it . Please can anyone explain me the 'write-back' concept clearly .


texts: Crimp terminal insulation of exposed leads

texts:
I'm dealing with an equipment which has a lot of internal wiring. The system is powered in 12V but the wires carry a good amount of current (in excess of 10A). I need to connect different units with screws terminals (power supply, relays, potentiometers etc..) and for this purpose I am using insulating ring terminals which are crimped to the wire and then secured (for reliability issues) with an extra heat shrinking tube. The ring itself of the terminal is not insulated and a single fault condition could cause the terminal to touch any of other electronics inside the panel. In order to increase the reliability level which kind of insulation can I put on top of the screws of the ring terminals? Is hot melt adhesive a good option? Or is there a specific solution? I usually dont rely much on insulation that melts at low temperatures since high currents can cause quite an increase of temperature which can in its turn melt down the insulation and start a negative cycle which in the end destroys the lead.

example


texts: Confusion regarding connecting nport in cadence while trying to find input impedance

texts:
I am a little bit confused on how to to connect the nport in the case where I try to find looking in impedance of a transmission line which is loaded by a 1pF capacitor on the one side.
As shown in the figure there are different ways of connecting the nport instance,

Can you please explain which is the correct configuration and why?


texts:
Does analog audio signal change polarity, or only "voltage level"?
Example, If I took the audio signal from a phone or computer and connected it to an electro magnet (basically just what a speaker is) will the magnet direction oscillate / switch back and forth between north and south or would the magnetic field never change direction only get weaker stronger with the frequency of the audio signal?


texts: I am trying to build a half adder using a 74LS86 XOR gate. Initially I connected both input pins that I am using (9 & 10) on the 74LS86 to the ground rail using 10K ohm resistors. I then connected 5V to pin 9 and expected the LED fed from pin 8 to light. No luck. I then pulled pins 9 and 10 high by connecting the 10K ohm resistors to 5V. When I pulled pin 10 low by connecting it to ground, the LED lit. I substituted 330 ohm resistors for the 10K resistors and reconnected them to ground. Now the circuit works properly when I pull either pin 9 or 10 high. Is 330 ohms an appropriate choice? Are pins 9 and 10 sourcing current when they are not active (pulled high)? I read that low power schottky ICs can only source 8mA. I am calculating that with 5V and 330 ohms that the current draw could be 15mA. I am wondering where I should look on the datasheet to properly size pulldown resistor for TTL ICs.


texts: Battery charger mAh rating - Can it be ignored if battery type is the same?

texts:
I have used a brand of NiMH batteries for years with a charger from the same manufacturer. After reading up on batteries I found the following statement on battery university All about chargers

  The Ah rating of a battery can be marginally different than specified. Charging a larger battery will take a bit longer than a smaller pack and vice versa. Do not charge if the Ah rating deviates too much (more than 25 percent).

After checking the rating of my charger I found it to indicate 1.2V 500mA. The batteries I have been recharging for years rate at 1.2V 900mAh. So is the charger I have used not suited for the batteries which are from the same manufacturer?


texts:
I have a PCB with a single-ended sinusoidal clock input via SMA connector. (It should come from an external, low-jitter clock source).

This clock is used at various places (as references) and hence jitter is the largest concern.

It enters multiple ICs (say 3 for now). The input to these ICs has to be sinusoidal. The input impedance of the clock inputs is capacitive (like CMOS inverters).

Considering signal splitting and matching, what is an appropriate way to split and distribute the clock?

Can I just make a star connection from the SMA connector to the various destinations or do I need some sort of buffers? If yes, which? (the clock distributions I find are just based on inverters and hence not for sinusoidal clocks/low jitter)
Is it enough to terminate once at the connector and use simple PCB traces to the destinations?
Should the traces be such that the characteristic impedance is 50 Ohm or 50/#consumers Ohm or just as thin as possible?

Take as an example (IC1 & IC3 have a self-biased inverter as input and IC2 is a discrete CMOS inverter which is biased half-rail of its supply):

simulate this circuit – Schematic created using CircuitLab

PS: lambda/100 is 3cm for 100 MHz. I'm definitely not able to confine everything within that. However, say, 30cm (lambda/10) should be possible.


texts: Using a resistor in series toreduce the voltage supplied to an appliance / microwave bulb

texts:
I just want to reduce the voltage supplied to a appliance microwave bulb from 125 v supply to about 110-115 volt. The bulb that I bought is rated at 120 v and the supply pins / connection supply 125 v. The bulb may blow sooner than necessary.
What size resistor in series do I use? And is this necessary to do?


texts: Trouble in interpreting and calculating temperature effect of an amplifier module

texts:
I want to estimate this industrial amplifier's temperature drift.

There is a section in the data sheet in ratings section as follows:

Basically the amplifier I use above is now set to around total gain of G = 2300. I measured this. And a 10kg nominal force transducer attached to this amplifier has 2mV/V sensitivity. This means for 10V excitation the transducer output increases 20mV for 10kg increase and for a 1kg increase the transducer output increases 2mV.

So to summarize, there is a transducer whose output increases 2mV per 1kg increase. This then goes to the industrial amplifier in question whose total gain i set to 2300 for now.

An example(after setting to around zero volt for no load):

Transducer is loaded 1300 gr and outputs 2.1mV; the amplifier outputs 6.178V

Transducer is loaded 1800 gr and outputs 3.1mV; the amplifier outputs 8.504V

So you can see the total gain is around 2300 from (8.5-6.17)V/1mV.

My question is how can I interpret the data sheet of this amplifier and estimate the change in the amplifier's output voltage for a 10K temperature increase? I don't understand how to do this by data-sheet's way of writing. So as you see above at a constant temperature I obtained  around 2.3V increase for a 1kg load increase. What would that increase in voltage be if the temperature would be 10K degrees more? In other words what would be the total drift of the amplifier output for a 10K temperature increase?


texts: Unable to trigger 12V DC Stepper Motor without driver

texts:
I am trying to test a 12V stepper motor using just a 12V DC adapter without any driver, but I am unable to get it triggered. I am using Velleman's MOTS1 motor and as per the data sheet attaching the power's negative terminal to the red wire and the positive terminal one by one to the other four wires.

1). To eliminate the possibility of a faulty motor, I even tried with two different motors of the same model. But both motors did not work.

2). I also realized that the adapter is delivering 11.8V instead of exact 12V. So, to eliminate the possibility of lower voltage, I supplied 15V using batteries, but that too did not work.

3). Also, using the same adapter and battery sets, I am able to trigger other regular 12V DC motors.

So most probably, I am doing something wrong here specific to stepper motors.

Please help! Let me know if you need more information from me.

I am an absolute newbie electronics hobbyist and have just 3 months of basic theory and practical experience. So, I guess, every suggestion is helpful :) .

Motors specifications from the Velleman's website - https://www.vellemanusa.com/products/view/?id=351245&country=us&lang=enu

resistance: 280 ohm
rated voltage: 12 Vdc
current: 32 mA
impedance: 380 ohm
phase: 4
step angle / step: 5.625° / 64
reduction ratio: 1/64
detent torque: 4.86 ozf.in
pull-in torque: 4.17 ozf.in
max. starting pulse rate: 550 pps
max. slewing pulse rate: 90 pps
temperature range: 77 °F
noise: 40 dB
cable: 420 mm AWG 1095#28
terminal: JST SPH-002T-P0.5S
insulation strength: AC 600 V - 1 sec. cut-off current: 10 mA
colors:

B1: pink
A1: orange
A2: yellow
B2: blue
GND: red
GND2 (for MOTS2): brown

DC Adapter specifications:

DC Volt Output: 12V
DC Current: 2.5 A


texts:
I'd like to generate an integrated calibration signal for a biopotential amplifier.  I'd like to generate a 0.5mV square wave (within 5%) at 200Hz (give or take on the frequency).

I'm thinking of using a large square wave generated by DAC, and divide the amplitude down.  There are clear issues, though.  I'd need to add an offset, as I'd need an inverting op amp, and then invert once more and remove the offset.  Now we're talking precision sources, and some rail to rail op amps.

Is there a way to do this with less hardware?


texts: Logic circuit to handle incrementing by 1

texts: You can use cascaded full adders to add any two binary numbers together. Is there a circuit for when I only want to add 1 (incrementing the value)? Is there a similar circuit for subtracting (i.e. adding 0b1111 1110)? I'm working with 8 bit numbers, but this applies for all word lengths.


texts: truth table for D flip flop with control variables x and y

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So I need to build a counter with D Flip-Flop and 2 control variables x and y.

XY=00 --> 0-3-2-1-0;
XY=01 --> 0-1-2-3-0;
XY=10 --> 0-2-3-1-0;
XY=11 --> 0-1-3-2-0.

How should I make the truth table? Should I put for every sequence for x and y the given controls(00,01,10,11) or I need to put for x and y 0 an 1 in order?


texts: Choosing the right power regulator for Battery powered designs

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I've come across this problem a number of times in my hobby projects, but I am sick of making an educated guess.

I often do microcontroller projects and often want them to be powered by a 3.7V Lipo cell charged by a standard microusb cable. This means input voltage can range from 3.0V to 5.0V and I want an output voltage of 3.3V. With thousands of voltage regulators that can fit those requirements, how do you choose?

I can ask about each specific project to get the right regulators, but I would rather have the knowledge I need to find the right regulators on my own. I'll add edits as I find more answers.

Edit1:

Switching Regulator - This is the only choice if you need to boost voltage. They are the most efficient and produce less heat than LDO's, but produce noise not usable with RF applications including bluetooth and wifi and are generally more expensive. If you want to use this with RF then you will need proper filtering.

LDO - LDO's are cheap and are preferred for RF applications because LDO's produce no EMI interference. They generally have poor efficiency but the efficiency depends on the ratio of the input to output voltage. The closer the two are, the more efficient the output will be. In high current applications they can produce a lot of heat so proper cooling may be required.

Charge-pump - A subset of switching regulators that don't require an external inductor. They generally have worse efficiency than inductor-based switching regulators but are better than LDO's. They can also only output relatively small amounts of current. These should be used when you need better efficiency than an LDO but are constrained on board space.

Hybrid - There are a few companies who make hybrid Switching/ldo regulators. These provide the efficiency of a switching regulator with the noiseless output of an LDO. The downside is there are very view of them and they don't have high output current in most cases. These still produce heat like an LDO.

Quiescent Current - In battery powered applications you need to be concerned about the amount of current the regulator uses to function. The more power it uses, the less battery power is left for your device. LDO's generally have much smaller quiescent current than switching regulators, but since switching regulators have the ability to boost voltage when input voltage drops below desired output voltage, which to use depends on your devices voltage requirements.


texts: Pic18f65k22 writing 2 bytes to a un unsigned char when assigning a value

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I am using pic18f65k22 and mplabx with pic kit 3.

I have an unsigned char variable sim_reg.
When i assign it a value of 0x01 it writes to two consecutive bytes instead of 1 .so it over writes my next variable hence causing a havoc.

The assignment instruction is sim_reg=0x01 and its disassembly is

Movlw 0x1
Movlb 0x2
Movwf count,banked

But it affects two consecutive bytes


texts: Adjusting offset (and possibly gain) of ADC preamp OPAMP with DAC

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I am designing simple 200MHz scope for use with FPGA board and came up to idea of software adjustable offset and gain of input preamplifier.

It is using TI ADC08200 and since I am not much experienced in hi frequency analog stuff I have only slightly altered their original preamplifier with help of LTSpice.

This is original design:

This is my altered version:

I am using quad DAC (I have two identical channels) and quad OPAMP (LMV324M) one of DAC/Opamp channels is making reference voltage for ADC making me able to adjust "gain" but this is limited to reference voltage ranges so it might be better to adjust it somehow on OPAMP, but since I didn't want to use digital pots for their high values (starting on 1kOhm as far as I know) and TI's datasheet clearly states that preamp should incorporate at least 2x or 3x gain which would be not possible with 1kOhm on inverting input (instead of 10+12 ohm).

The second channel is used for adjusting offset and I am not certain wether this is ideal way of doing it. As far as my LTSpice testing it seemed to work but I don't know if it works in real circuits. With one slight problem that it seems that it also adjusts gain a bit. I don't know if it's the cause of misadjusting gain since only difference is that I am not using pot to adjust offset but I adjust voltage direclty.

Next thing which bothers me is how to correctly make protection from overvoltage?

Now I am using pair of silicon diodes on preamp input and pair of diodes on ADC input with help of 5.6V zener diode to get 0.6V by going 5.6V above -5V rail which allows silicon diode to sink overvoltage below -100mV. I think it should work this way and LTSpice simulation seems to confirm it, but I think there is better and simpler way of doing it.

I though about using shottky diodes, but I think that since shottky diodes have high reverese leakage they introduce high distortion and when I have tested it in spice it was noticeable.


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"Why does increasing the load on the secondary coil circuit increase the current in the primary coil circuit"

This question is given as an exercise in my book. I can't figure out whether this is a poorly worded question or if I misunderstand. The answer I can come up with is that power is dissipated over the load so more power is needed to be supplied by the ac source. This seems too hand-wavy to me though, why would it not increase in the first place? How could it know that there is an increase in power needed if there was no change in current or magnetic flux from the secondary side to signify the change? Surely the component would just have a smaller potential drop?


texts: Why doesn't a high current transformer get damaged when shorted?

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In this video a high-current transformer secondary coil is shorted with numerous thick pieces of metal - pieces of rather thick wire and a knife blade. All those pieces either get red-hot or just melt. The video lasts about five minutes. The transformer doesn't seem to have any kind of active cooling yet it doesn't melt and even its windings insulation doesn't burn.

Why doesn't the transformer get damaged when shorted?


texts: Retrigerable Monostable Multivibrator that fires on both rising and falling edge.

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I have a need to generate an active low pulse when a switch is depressed AND when it is released and keep the component count and PCB real estate as low as possible (while still allowing me to manually rework).  Schmitt Triggering would be nice too - after all it is a switch.  Oh and it is a portable 3.3vdc device so power is a supreme concern.

I have a solution using two MOSFETs and a hand full of resistors and caps - not true Schmitt Triggering but pretty good debounce.  But I was wondering if something like the SN74LVC1G123DCUR could be employed to get my component count down.

SN74LVC1G123DCUR is half a low voltage CMOS version of the 74123 with only a single one-shot and a tidy little 8 pin package.  But from the data sheet it does not appear to me that you can simply tie the -A and +B inputs together and accomplish my goal.  Can anyone tell me if this is doable or if it can be accomplished with another small footprint IC?


texts: im just an electronic enthusiast #1?  Is it posible to power the peltier with a motor speed controler 220vac input and varable output. If no, why? What  are the remidies #2? And if i use a 48vdc power supply stack it in series What will b the power consumption. Thank u for any answer