texts:
I'm having trouble to identify this bad boy:

'680' or '089' i don't even know how to read it.
Can someone give me the value ?

I used a Chinese T4 LCR on it and according to the result the value is 61/62 pF

What the difference between this next capacitor (except value) and the previous one if there is any?


texts:
I'm trying to design a circuit in which a microcontroller produces a signal and then using an amplifier drives an 8ohm speaker.
I've so far used LM386, but it cannot go above 1W, which turned out to be insufficient.
Besides that, I wish to add an (second order) anti aliasing LPF at the output of the microcontroller.

The general schematic is below.

If I wish to feed the speaker with 2W, then I would need 4v, 500mA on the speaker.
Is it possible for me to do it this way, or is there a better circuit for my needs?
Is there an op amp that can comply with these requirements?


texts:
I have not a big background in electronics. I am designing a PCB including a MCU (EFM32) and some ICs. I have seen in lots of circuits that they generally add an external Crystal Clock on the board and I wondered why not to use the internal MCU clock to clock the circuit ?

I know this question is a beginner question, but I have hard time to find an answer (keyword problem I suppose).


texts:
I am dealing with a regenerative power situation with BLDC motor and servo drive controller.The power supply is 48V regulated DC but during deceleration due to regeneration, the voltage at drive increases beyond 48 V

I plan to dissipate the reverse current through power resistor in the form of heat. To achieve this dynamic braking, the driver circuit for MOSFET switch has to turn ON during regeneration when voltage exceeds certain limit and turn off when the voltage drops. I tried  looking for hysteretic comparator to generate signal for switch but could not find for such voltage level. Can you suggest any different technique for controlling the Braking MOSFET switch?


texts: I am messing around with some power supplies. There are pinouts labelled "reserved" and "remote"- what are they?

texts:
I have worked out that that the Remote pin works like the Green "Power Supply On (active low)" wire on an ATX supply, and found a wiki on remote sensing about it being used to get diagnostics on the power-supply (if I understand correctly)

Now I have a little red wire that does nothing, with .5V on it.
I am viewing pins 1 and 5 on This

Just curious, Is it perhaps simply a case of leaving a wire in because the standard connector/wire has X terminals and axials?
It is called the "Reserved" pin, and other sites cite it as a second "Remote pin" even though it does not activate the power supply.


texts: Implementing a class-compliant USB MIDI device

texts:
I'm building a device that I want to communicate with a computer using MIDI over a USB connection. There are lots of USB MIDI devices that are class-compliant and thus require no special drivers, which is exactly what I want.

I was hoping that I could use a microcontroller with hardware USB (e.g., MSP430) or a FTDI-style serial-to-USB chip to do this, but it seems like none of them support setting the device descriptors to identify as a MIDI device. So how can I accomplish this? Do I need a dedicated USB controller MCU?

I have only a fractured understanding of USB, but I've tried to read the USB MIDI spec.

I'm aware of serial-to-MIDI converter software, but it's not what I'm looking for here.


texts: Reducing the voltage into a speaker passively

texts:
Well not high power, low resistance. I have an unusual situation where I am directly driving speakers from an oscillating signal ( its not audio its more like a buzz )

I only have 2 inputs

12v
square wave signal that oscillates at audio frequencies between 0v and 12v ( not open circuit and ground )

so the speaker basically sees a negative signal which is no problem in this situation and I block too much current with a capacitor.

Ideally though I would like to reduce the voltage to make it quieter, so I have gone through the following ideas.

Cant use resistors as they would have to be low resistance = heat and power!
diodes in series work but to get down to a good voltage I need about 10+ diodes
I tried a LM317 but it has ripple protection? It was too quiet

I know ideally if I had a steady 0v it would be easy, but does anyone have any other ideas I could use? or perhaps I am doing something futile?

Ok edit:

I am not making sense , the title makes no sense sorry so I corrected it.

clear info

I am driving an 8 ohm speaker off a circuit that drives LEDs.

It supplies 12v and another connection between 0v and 12v that pwm fades the led at audio frequencies.

I can't touch the circuit driving it and I want to passively cut down the voltage to reduce the volume on the speaker as it is fairly loud.

Ideally with not too much concentrated heat.

What is the best way to do it?


texts: Some segments not working on 7 segment multi led digital clock

texts:
I have this old homemade digital clock which i'm trying to revive. It has sentimental value as it was built by my dad in his youth.
The problem is 2 of the segments only sometimes light up on the third module. There is no part number visible.
It doesn't look like it's a bad connection, i've resoldered most the wires that go to that module and as i've said, it occasionally works out of the blue..
I'm not sure where to begin investigating. I understand what most components do, but i'm a newby in electrical engineering. Any help appreciated.
My next idea is to start replacing components.. but i'm not sure how to check for bad components on the board.
I added the boost module in order to power it from 5v instead of 220v mains. The output is set to 15v as that was the value written on the board.


texts: Current mirror Configuration using BJT application

texts:
I want to design a circuit having output voltage of 3.3 V and 30mA current. As I am newbie in the electronics field, I see lots of circuit using buck topology, using IC's and using transformers.

Now as I heard something great in my BOOK i.e. current mirror configuration using BJT. As far as explained in my book, it is a circuit consisting of two matching transistors with the collector of one connected to the bases of both,thus producing the same collector current in each transistor.

Now in order to get the collector current in mA, only a small amount of uA current is required. By providing a little amount of base current can I get the sufficient amount of current from the collector end which s furthur used in my application??

If using this (current mirror configuration) with a capacitor power supply(using 0.15uF cap which gives upto 11mA currnt) then its easy to get a small amount of current in uA which is furthur supplied to the base terminal.

If not then what is the reason as I really stuck at that place.I also searched it on internet but didn't get a good response.


texts:
In particular two cases.

1) Unregulated: Supercap versus battery.

2) Regulated: Best regulation method to power precision low current analog circuits again with battery versus supercaps.

I know "best" is dependent on a lot of things. I'm looking for off the shelf linear regulator versus op-amp and precision reference, etc. I'm ignoring power supply and common mode rejection of the rest of the circuit at this point.


texts: MOSFET shorted after I connect them in parallel, what's wrong?

texts:
One of my MOSFET source-drain shorted after I connect them in parallel?

So I was making an ARC speaker yesterday, and I used one MOSFET ( irf540), and it got really hot, but it did not blow up, so I decided to put another MOSFET connected in parallel, and before I connected them I have tested both MOSFET and both of them worked normally, but when I connected them in parallel, the whole setup shutdown immediately due to overloading, and I found that one of my MOSFET was source-drain shorted that's why the power supply shut down to protect itself.

How do you connect the MOSFETs?
Just normal parallel circuit gate to gate, drain to drain, source to source, .connected with a piece of wire

PWM controller?
TL494CN, powered by a battery, completely isolated from the MOSFET side

MOSFETs?
IRF540 from IR

As you can see in this video there are two MOSFETs on the heat sink but the lead was disconnected because it was shorted.
By the way this video is not specially made to show the setup so it would be more focused on the fly-back.

Here is the full schematic and the PWM board.


texts: What additional electronics are required for construction and use of a 240-cell Ni-MH battery pack?

texts:
The robot (R2-D2) that I am building requires a MASSIVE battery. 800 Wh, to be precise. Cost is the primary driver, second to weight and volume. This, in combination to the high cost of any (non-lead) pre-made battery of this capacity has driven me to consider the design of a homemade pack of individual AA cells. The configuration in mind calls for the use of 240 (1.2-volt, 2.8-Ah) in a 10S-24P arrangement (12-volt, 67.2-Ah). This battery may commonly be drained to (or close to) zero. This inquiry has 3 parts.

BALANCING. I understand that normal Ni-MH packs (4.8, 7.2, 9.6, 19.2) do not require balancing. They need only be attached in series. However, I should consider this FAR from normal. Over the entire lifetime of this droid (~2 years), would a balancing circuit be ideal? If so, what suppliers exist for a single board capable of a 12-volt, 40-amp (peak) current?

CHARGING. A number of functionalities in droid require continuous operation, and must remain powered during charging of the battery. In addition, this droid will be used on a daily basis, and must be fully re-charged within 8 hours. Do any specific regulator circuits exist, capable of providing these characteristics for a Ni-MH pack of such size? Is a special converter of regulator required to prevent over-charging?

SAFETY. If additional equipment is not required for balancing, charging, or regulation, what are good practices? What is better for protection from overheating, short-circuit, and over-current draw (fuses, limiters, regulators, etc.)?


texts: Most efficient way to read analog signals in c++

texts:
I am new to AVR programming, and I am trying to learn the basic I/O with C++.

I am trying to find the simplest, most efficient way to read analog signals using the same function for different devices, just like the analogRead() function in the Wiring language (Arduino code). But I have not found anything very simplistic that I could use for AVR programming.

Any suggestions?


texts: Transformers circuit question,where is my mistake?

texts:
I have to find the power in the 4-ohm resistor in the circuit below.

In mesh 1 we have: \$16\angle 0 \mathrm V = 2I_1 - 8I_3 + V_1\$

In mesh 2 we have: \$V_2 = 4I_2\$

In mesh 3 we have: \$0 = 10I_3 - 2I_1\$

\$5I_3 = I_1\$

By the circuit we notice that \$V_2 = 2V_1\$ and \$I_1=2I_2\$.

Here I find \$I_2\$ So I can find \$P = 0.5*I_2^2 * 4\Omega\$ but the problem is that in my book \$P = 18 \mathrm W\$, which isn't the result I get. Where is my mistake?


texts: Help understanding frequency calculation for VCO Schematic in LM13700 Datasheet

texts:
I am trying to work through the math of the following schematic pulled from the LM13700 datasheet:

I can certainly hook this up and mess with the values to change the frequency range to my liking (and I will) but I am more interested in working out the math formula using the values provided in the data sheet at this point.

Problem: Using the values in the schematic, I am unable to come up with the same frequency range (f_OSC) that the datasheet describes when I put the numbers into the formula.

The formula for fig 33 in the data sjeet is: f_OSC = I_C/(4*CI_AR_A)

Sorry for the plain text equations, MathJax editor doesn't appear to be available right now.

According to the Datasheet, using the values shown in the schematic above, if I plug in ~0 < I_C < .001 Amps, I would expect a resulting frequency of 2Hz < f_OSC < 200kHz.  However, plugging in the high end value (.001A) I get more than double what I should on f_OSC.  I'll try to show my work below in hopes it will point out an obvious error to those more mathematically inclined:

f_OSC = (.001 Amps) / (4*(.0000000002 Farads)*(30 Volts/51000 Ohms)(5100 Ohms))

f_OSC = (.001 Amps) / (4*(.0000000002 Farads)*(.00058 Amps)(5100 Ohms)

f_OSC = .001 / (4*.0000000006) Farad*Ohms

f_OSC = .001 / .0000000024 Farad*Ohms (Seconds?)

f_OSC = 1 / .0000024 Seconds

f_OSC = 416,666.67 Hz

As for the .00058 Amps you see in the denominator for part of the equation above, I used 30 Volts to divide down the resistance instead of +15 Volts because the pin that receives I_C follows a path to -15 Volts, not Gnd.  So the total potential difference there is ~30 Volts.

Question: Can someone please help me understand why my math shows an output f_OSC = 400KHz for an input current of 1 milliAmp when the data sheet indicates the answer should be 200KHz for the same input?  Did I solve the equation above correctly or perhaps misinterpret the information in the datasheet?


texts: Are there reasons besides audible noise to run a VFD at a higher carrier frequency?

texts: VFDs - variable frequency (motor) drives - output a pulse-width-modulated carrier approximating a sine wave. The carrier frequency is typically variable. I've seen numbers as low as 1 kHz, and as high as 16 kHz. Higher switching frequencies inevitably lead to higher losses in the drive, lower efficiency, and possibly derating of the drive. Higher carrier frequencies also run into problems with long cable runs. I understand that audible noise is a concern; are there other reasons to ever run a higher-than-minimum carrier frequency?


texts: How do I know if this is a positive or negative feedback to the op-amp?

texts:
I am trying to build a line-following robot with the schematics I found below. I have just started to understand the use of feedback in op-amp. Ie. The continuous balancing mechanism creates a very stable gain determined by resistors connected to the op-amp.

I have tried to trace the current path marked in green and orange lines for the respective op-amp. Both lead to the same inverting and non-inverting input terminal of different op-amp.

I am kind of puzzled by this.

1) What is the point to have feedback to the different input terminals?

2) Because of the different input terminals used, how do I know which is the negative feedback? And is there even a thing like "positive feedback" happening here?

3) Or could it be a schematic drawn wrongly because it is just not technically practical nor possible to have the feedback wired in this manner?

Many thanks in advance.


texts:
I am wondering if I can make a vacuum tube oscillator for a LED flasher.

The problem is I only have 4 vacuum tubes: 14GT8, 12AU6 and 2 12BA6 tubes. I have a 12 volt DC power supply, 10 volt AC, 20 volt DC, and 5 volt DC.

I know it is most likely impossible to make a flasher with these tubes, so I am wondering if I can combine it with common semiconductors like a 555 timer or a 2N2222 transistor.

I just want a LED flasher/oscillator  circuit that needs the tube(s) to function for fun. Is this possible?


texts:
The image shown right below is a schematic diagram of the circuit.

There we need to find the equivalent resistance through X and Y.

I reduce the inner most resistors  , because I figure out that there is a Wheatstone bridge out there,   the resistance that I removed are shown below.

How can I proceed further , I have  no idea , I am stuck on this .How could I  proceed further and  find the equivalent resistance through X and Y  ?


texts: Constant current regulator enable when current and voltage reached

texts: I have constant current regulator which consists of one transistor, two diodes,  enable transistor (1.5k ohm) and resistor connected from emitter to GND (~15-20ohm) as visible in schematic. It limits current up to 80mA.  Base is enabled when there is only 0.8-1.2mA. I want to fully enable transistor when there is reached 6-7V and at least 6-10mA. How could this be done?


texts: Calculation results depend on simulation time (LTSpice)

texts: I am trying to simulate a circuit with several neonbulbs. And I have notified that the results I get depend on the simulation time described in the '.tran' command. An example is in the picture below. In an 80-second simulation, the same peak (at the same time) has about 180 nA, with a simulation time of 200 s, the peak has 90 nA. This is not the only example of this difference. This is just one of many and it completely blocks my project. I don't know what real value is. Moreover, I cannot compare different values. Please help me.


texts: Do a Thevenin source and its equivalent Norton source always supply equal power?

texts:
Power supplied by a Thevenin source

$$P_{Thevenin} = V_{Th}^2 \frac{1}{R_{Th}+R_L}$$

Power supplied by its equivalent Norton source

$$\begin{eqnarray}
P_{Norton} & = & I_N^2 \frac{R_{Th} R_L}{R_{Th}+R_L} \\
 & = & \left(\frac{V_{Th}}{R_{Th}}\right)^2 \frac{R_{Th} R_L}{R_{Th}+R_L} \\
 & = & V_{Th}^2 \frac{R_L/R_{Th}}{R_{Th}+R_L}
\end{eqnarray}$$

So power supplied by a Thevenin Source and its equivalent Norton source are equal only when \$R_{Th} = R_L\$.

Is it true or am I missing something?


texts: how to calculate rms voltage value of PWM motor

texts:
My motor is of brushless type controlled by a PWM signal, it is three-phase synchronous.
I measured the three voltages of each phase and now I need to calculate the RMS value on all 3 phases.


texts: Why are vacuum tubes more resistant to electromagnetic pulses than solid-state devices?

texts:
I heard that equipment that uses vacuum tubes are generally less susceptible to electromagnetic pulses than those that employ solid-state devices.
I don't know if its true, because I didn't find any detailed research about this topic.

If its true, is this because of the physical size difference between these devices, or is there another reason?

I searched about this subject, and I found an article from the Science Magazine.
I searched for the relevant parts, and it says:

  Most important, the U.S. military itself had not experienced problems,
  since most of the field equipment and ships exposed to EMP dated from
  the 1940's and 1950's, their electronic systems relying on vacuum
  tubes.

  In the 1970's, it was discovered that vacuum tubes have about 10
  million times more hardness against EMP than integrated solid-state
  circuitry (2).

As you can see at the end, it references another article:

  M. A. King et al., An overview of the effects of nuclear weapons on
  communications capabilities," Signal (January 1980).

After 2 hours of searching for this article, I couldn't find any traces of a Signal magazine or anything like that, released in the 80's.
I found other citations of the same article, and it has the additional author not present in citation part of the Science article, P. B. Fleming, but still, no info on these guys apart from people with the same name but entirely different professions and other irrelevant research papers.

I have some doubts about the science behind the claim that vacuum tubes are 10 million times more resistant against EMP, it kinda sounds like an advertisement from that time.

Source:

Broad, William J. - Nuclear Pulse (I): Awakening to the Chaos Factor
Science  29 May 1981: Vol. 212, Issue 4498, pp. 1009-1012
DOI: 10.1126/science.212.4498.1009


texts: Large to medium size e-Ink Display for prototyping

texts:
I have been doing research in finding various raw screens for prototyping, stuff like e-ink, color e-ink and OLED screens.  Then I saw this earlier post: Gumstix with an e-ink screen

So after one year since the original post by @tjameson, has anyone find a place to get e-ink screens that are larger than 6 inches?  For what I am trying to do, I really need 6 to 11 inches screens.


texts: Converting a 120V universal motor to run on 240V

texts:
Is it as simple as rewinding the field coils with twice the number of turns and wire half the cross-sectional area of the original?
or would the armature coils also need to be rewound as well?

The motor is rated 120V, 200W. I live in  SE Asia, so wall voltages are 240V. I do have a voltage transformer, I just wanted to know what is involved in converting the motor to run on a different voltage.


texts:
I bought 5 identical 12V drill DC motors. First thing I did was to measure (for one of them):

the current consumption without any load: 0.16A
the inrush current at turning the motor on: 1.5A
the stall current: 1.5A (the lab power supply showed 2A once)

I plan to use 5 of these motors to make a tool for drilling 5 equally spaced holes in a 3mm thick wood. I have a DC power supply (12V, 10A) which I intend to connect them to. The diameter of the drill collet, which will be used is 2.5mm. The pieces of the wood, which I'll be drilling holes into, are part of a honeycomb frame (2 pieces per frame, 5 holes per piece).

My question are:

can I connect them directly to the power supply and activate them using a bistable switch (while using flyback diodes)?
or should I use an arduino, 5 MOSFETS, flyback diodes (I have a lot of 1N4007) to slowly (with PWM) start each one?


texts: How is this method of addressing memory scalable?

texts:
I've been watching Computerphile videos about memory. I'm currently watching this one

In it he goes over using some logic gates to address flip flops. He explains that is is cumbersome to add a wire for each memory address, and that using some logic circuitry is better. He only goes over the case for two bits.

It would seem to me that adding more bits make the logic circuits increasingly complex. I designed a simple logic circuit for 3 bits and it looks like this:

Perhaps my design is poor, but it seems to me that as you add more addresses, the logic circuit to address them would become increasingly complex. Wouldn't adding all these extra components to the memory chip be just as bad as adding more wires? Or am I missing something fundamental?

What is the advantage over using logic circuits as opposed to individual wires to address the flip flops?


texts: Center tapped transformer equivalent circuit model

texts:
What is the correct equivalent circuit model of an arbitrary center tapped transformer? i.e. I simply want the equivalent circuit model with has to look something like this:

In center tapped the secondary (or primary) we have multiple couplings between wingdings and I wasn't sure my model was correct.

Any advice is appreciable.

EDIT1: circuit model is needed for the following center tapped transformer:


texts: VLSI channel routing: Why only route through channels?

texts:
I know that after placement you have your blocks and channels between the blocks. Now, the routing only takes place in the channels.

My question is: Why can't we just route 'over' the blocks by placing the wires in a higher metal layer?


texts:
I have the following connectors on a USB dongle (the ones on the left of DEBUG):

They are tiny (I put the dongle on an Arduino to show the differences with the typical ones I know)

Are they standard? And if so - is there a specific name for them which I could use to search a connector? (I clumsily tried to solder some cables instead but this is out of my soldering league)


texts: Way to determine order of cards plugged into controller board

texts:
REVISED: I have a master controller PCB with four bus bars (+, -, and two signal lines), see image below. I have module PCBs A-C (or could be 10 or 15 of them), each with MCUs and unique identifiers, that plug into the sockets in an unknown order (and may or may not all be present).  How could the module PCBs communicate with the master controller so that the master controller would know the ordering of the module PCBs. (In the digram it would be [C, A, B].) The two "signal" lines drawn could be reconfigured (or additional components/circuitry added).

ORIGINAL: I have a master controller PCB with sockets 0-5. I have module PCBs A-F (these are also the unique IDs, either through an MCU or other means) that plug into the sockets in an unknown order (and may or may not all be present).  I am wondering if there is a simple way for the master controller to know the ordering of the module PCBs. (In the digram it would be [C, E, A, B, F, D].) There is one "signal" line drawn but additional ones could be added (or additional components/circuitry).


texts: How to calculate torque of a 4-pole BDC hobby motor

texts:
I have a hobby motor that claims to be a 2200KV motor. This particular one is a 4-pole motor.

Using a drill, I spun the motor at 1312 RPM. On an oscilloscope I see 1.3V peak-to-peak waveform between two of the phases (a pretty distorted sine-ish wave) having a frequency of 43.73 Hz.

Converting this frequency into radians per second, I get 274.649 radians per second. Calculating KT from this I get 0.65 volts peak / 274.649 rads/sec = 0.002367 N*M/Amp, which just seems really low.

Since the motor is a 4-pole motor, whose electrical frequency is twice the mechanical frequency, should I have used half the frequency seen on the oscilloscope? That would make the calculation 0.65 volts peak / 137.325 rads/sec = 0.0047333 NM*Amp, which might seem more reasonable.

I guess the main question is -- when calculating torque constant by dividing the back-EMF voltage by radians per second, is it the radians per second of the shaft speed itself, or radians per second of the back-EMF frequency (which increases for each pole-pair)?


texts: The luminous intensity and beam angle of LEDs

texts:
Do the luminous intensities of LEDs mean the peak intensities of the LEDs, or the intensities averaged over different beam angles?

Typically the data sheet of a LED specifies its luminous intensity and beam angle, like the following.
 https://www.sparkfun.com/datasheets/Components/LED/COM-09590-YSL-R531R3D-D2.pdf
The data sheet says the intensity of the LED is between 150mcd and 200mcd. Would it mean that the intensity is 200mcd at the beam angle of 0 degree? Or is it the intensity averaged over entire beam angle?


texts: Smallest possible PCB size for TI CC3200

texts:
I'm just getting started with hardware side of Computers. At this point, I'm really interested in TI's CC3200 Network Processor, which has an integrated CPU to allow me to run custom code. You can see the datasheet here: enter link description here.

Since I'm a hardware noob, to me it looks like this SoC is pretty much self-contained and that if I just powered the chip it will work, but I'm also thinking that it probably requires more components. Can anyone look at the datasheet and quickly tell me what's the smallest pcb size you think is required for this chip, assuming I only need to power this chip and don't need to connect any LEDs etc.


texts: Why does reading 1 byte from hard disk has the same speed as operation reading 1000 bytes?

texts:
Two operations:

read 1 byte from disk
read 1000 bytes from disk

Why exactly will they have approximately the same speed?


texts: Stripboard/veroboard/matrix board design software

texts:
I'm prototyping a simple layout for a small project on matrix board, but figured there must be a better way than drawing it all out on paper. Are there any aimed at matrix board?

I've found the following software for stripboard, but nothing explicitly for matrix board:

DIY Layout Creator
Stripboard Designer
Stripboard Magic (seems to be abandonware, but there's page about it here)
VeeCAD Stripboard Editor Limited free version, designed to integrate well with TinyCAD
VeroDes

Any more I've missed? Any recommendations?


texts: Timer of 12 seconds using hardware circuit

texts:
In my design, say there are 2 pins A and B.

Now I want to implement circuit in such a way that B is initially high , but when A goes low, after 12 seconds B will go low for short duration and again will become 1.
Is there any circuit which I can implement.

I tried below Monostable multivibrator as timer using IC555, but issue is that initially B is low as per configuration.

Required signals as below:

Can someone help me and suggest? Thanks in advance.


texts:
In the IGLOO2 FPGA, I know there are several FCCC available for use. As best I can tell, which one is used is picked at synthesis. Is it possible to force the LiberoSOC tools to use a particular FCCC instead of choosing for me?

Specifically, I'm using a M2GL025T-1FG484 IGLOO2 FPGA, and I want to use either the NE0 or NE1 FCCC's, but the synthesis tools pick either the NW or SW FCCCs for my particular design.


texts: Is the roll-off gain of filters always -20 dB/dec?

texts: I have been doing some preliminary lab calculations since I have an intense session coming up next week. I have to solve many filters, most of which are just basic, passive RC filters; others form part of Operational Amplifier circuits (which I have been told are called active filters). My lab instructor told us that the roll-off of filters after the cutoff frequency is -20 dB/decade (he was talking about a Low Pass RC filter). However, sometimes, when I am solving circuits involving OpAmps, I get that for instance, the gain at the cutoff frequency is 17 dB, and at \$10f_c\$, I get 0 dB, which is not a -20 dB roll-off. Other times I have gotten \$G(f_c)= -3dB\$ and \$G(10f_c)= -20dB\$, which is yet again a 17 dB difference. Is this normal? How can I expect these results?


texts: LM3478/LM5155 configuration on a wide input and output voltage range

texts:
In my last question I mentioned the case of obtaining different output voltages from a single switching regulator. I ended up running a successful simulation of such setup in LTSpice using MC34063 and mosfet transistors to switch the feedback resistor and set the output voltage based on the input from a CD4017 counter.
Now, I would like to do a similar thing on a higher power regulator like LM3478 or LM51551 chosen based on the TI's WEBENCH Power Designer online.
I ended up setting up both models in the LTSpice to simulate it like previously and they seem to work right, however just for the initial Vin and Vout settings. After changing the resistor pair or setting different voltage input the whole thing either does not manage to obtain the set output or is completely off in terms of its performance. My guess is that it is due to the fact, that these ICs are more complex in their configuration than the MC34063 used before in the learning process.
Also, my input is to be such as:
Case 1: 6.4V Battery - 8V, 10V and 12V settings possible;
Case 2: 12.8V Battery - 15v, 20V, 25V settings on the output.
All based on one circuit with proper analog logic and jumpers applied to switch between these cases.
Do you think it is possible to obtain a viable configuration operating on these wide ranges using these kind of voltage regulators with complex setup? Is there any widely used, high power, but simpler to configure switching regulator which would be a valuable option to look at in this use-case?
I'll appreciate any advice on that. Below is a picture of the configuration with LM3478 from LTSpice.


texts: How to determine which motors give me faster acceleration to a speed?

texts:
I have two motors for one system, assume that I do not allow to do experiment to fund the answer.

One of them is
http://www.servocomponents.com/Pittman-Brush-Motor-14000-series/14207s008-SP

The other one is
http://www.servocomponents.com/Pittman-Brush-Motor-9000-series/9237s011-SP

They connect to a 0.3520 [oz·in 2] system respectively.

Which one will accelerate faster to reach 1500 rpm?

When I study this problem, I know that there are two parts.

One is the mechanical which is the torque, inertia part.

The other part is the electrical part, which has the back EMF, internal resistance, etc.

How to find the answer?


texts: Data Transmission Using RJ45 Cable in Stratix IV dev board

texts:
I'm totally a beginner and my question may seem a little bit stupid, but I would be grateful if you provide any help.

I want to transmit data between my laptop and a Stratix IV GX Development board using RJ45 cable but I don't really know what procedure I should follow. There are tons of reference designs/examples in Altera website (10Gb MAC, Triple-speed ethernet, lots of "application notes", etc.) and I'm completely confused.

I just want to transmit a single bit to the board, invert it and send it back to my laptop, so I don't really need any sophisticated hardware implemented in the board.

I'm familiar with Verilog and design flow using Quartus II software, but not really into communication protocols.
It would much help if you provide me some procedure to follow to accomplish this task.

Thanks in advance,
Behdad

P.S. I'm using Quartus II 13.1 64-bit on a linux machine.


texts: Why Op Amp circuit not behaving as desired

texts:
I want to convert PWM output of microcontroller  to 4-20mA. I use below circuit for this
work :

But voltage on pin + and - Are not equal in this circuit!!! for example when pin + is 1.2 volt with voltmeter ,pin - is 2.04 volt . while They should be equal http://en.wikipedia.org/wiki/Operational_amplifier

in your opinion , what is my problem ?


texts: How much heat is generated by a Li-ion phosphate battery during discharge

texts:
I am designing an enclosed container with 10 kWh 50 V battery in it which requires me to actively remove the heat. The battery feeds an 8.8 kVA inverter.
Assume I have a load of 8 kW, which would draw 160 amp at 50 V.
One of the sources https://batteryuniversity.com/learn/archive/how_does_internal_resistance_affect_performance referred to small Li-ion and gave internal resistance of about 320 mΩ to 340 mΩ.
Other sources were more academic and incomprehensible. Most addressed charging - nothing on large batteries.
If this is the case the internal heat generated would be I2 × R = 1602 × 320/1000 = 8192 W, an impossible result.
Either the internal resistance is wrong or I am using the wrong logic. How much heat would the battery create during discharge?


texts:
What is the difference between the threshold voltage (Vth) and gate-emitter voltage (Vge) for IGBT devices?

How can I calculate Vth of an IGBT chip?


texts: Do batteries lose voltage as they're used up?

texts:
V = IR

Resistance stays same, and I know as a fact that I (or current) decreases (my stuff runs slower on old batteries).

So could a 9 Volt battery turn into a 1.5 volt one?


texts: how to implement ab+bc+ca using nor gates

texts: How do I implement the function ab+bc+ca using nor gates only ?  I am having trouble figuring out all the steps.


texts: Controller Area Network - RLC filter for filtering noise

texts:
Here is the circuit :

simulate this circuit – Schematic created using CircuitLab

I suppose the circuit is used for filtering the noise coming from the CAN Bus. According to the transceiver datasheet between the microcontroller and the filter, "High Speed (up to 1 Mbit/s)", the maximal CAN speed is 1 MBits. First question, does the CAN protocol need a filter ? The can protocol is said to be robust and working in harsh environnement. So what is an harsh environnement... I have no informations about the operating environnement of this CAN and filter.

I do not really know how does the CAN physically works. According to the informations that I found, I did the approximation that the input waveform coming from the bus was a square wave. So the input waveform at the filter stage is a square waveform whose the frequency is 1 MHz (worst case). I do not know if it lower or not... According to Fourier, there is a lot of (infinite) harmonics into a square wave, so obviously the filter will have an impact on the input waveform. The filter should be designed to have a high attenuation on noise and a very low attenuation on the waveform. Even if I do not consider the noise, the filter will have a high impact on the input waveform... Indeed, the resonant frequency is equal to 2.29 MHz, Q is equal to 2.23 > 1/2 so the filter is underdamped. I would like to have your opinion about this filter. Is it well designed ? Under which conditions ? I can understand that the filter have to be underdamped as to increase the rise time and fall time of the waveform. Nevertheless it rings ... Do you think that those oscillations can introduce error when decoding the signal coming from the bus ? In other words, wouldn't be better if the filter was not here ? Wouldn't be better if the resonant frequncy would be higher than 2.2 MHz ? There would be less attenuation on low frequency noise but the filter would less modify the input waveform.

It will also deform the waveform coming from the transceiver and going to the bus.

By the way, what is the purpose of using a common mode inductance rather than two separates inductances ? it means that when one input (CAN_High) of the transceiver is sourcing current the other (CAN_Low) is sinking current for example and inversely ?

Thank you very much !


texts: Understanding Meanwell CV+CC driver characteristics

texts:
I have an LED fixture that can take 2 to 2.5 amps. Vf is around 36 volts.
I am planning to use Meanwell ELG series driver to power it up. [Datasheet here]
This particular model can work in CV+CC mode and I want to make sure if I understand it correctly. It gives the following graph:

I want to use ELG-100-42 model.

If I use ELG-100-42 model LED driver, my fixture will draw 2.28 amps and LED driver will be go in CC mode at that current and the output voltage will stabilize near 36 V. Since 36 V is greater than 50% of output voltage (50% x 42 V = 21 V), my output voltage and current will remain stable and it won't go into hiccup mode. Am I right?
I want to confirm if my chosen driver is suitable for my fixture or not.


texts: Replacing two LEDs with a 2-pin, bicolor LED, using a circuit that reverses polarity based on two inputs

texts:
I'm working with a commercially available circuit that can optionally be configured to disable its internal LEDs and use two external LEDs. This post discusses the use of external LEDs. One LED or the other may be activated periodically; simultaneous activation of both LEDs never occurs. Both external LEDs connect to a common 5V source, and the cathode of each connects to one of the circuit's two LED output pins. When not activated, the output pins are left floating. When a pin is activated, it pulls its connected cathode to ground. The output pins each accept a maximum voltage of 5V, a maximum sink current of 20mA and cannot source current. I think the circuit, configured to use external LEDs, looks something like the following. (The mfr. documentation calls the output pins "open collector outputs", so I've shown them that way. But I think this is questionable, because their operation is described as though input signal is not inverted. It could also be that my understanding of open collector outputs is incomplete.)

If possible, I would like to replace the two LEDs with a single, 2-pin, bicolor LED (in effect, 2 LEDs connected in reverse parallel). The new circuit would behave as follows: when neither of the circuit's output pins are grounded, no power is supplied to the LED; when one of the pins is grounded, power is supplied to the LED with polarity oriented one way or the other, depending on which output pin is grounded. The power source is a battery whose voltage will range from 11V to 13.6V.

Additional requirement: Relays are not an option. In its default configuration (using internal LEDs), the circuit's current consumption is advertised as 0.125mA. If a solution that keeps power consumption similarly low isn't possible, I'll stay with two external LEDs, or I'll go with the internal LEDs and a light pipe if possible. As the enclosure might need to be opened by the user, an electrical connection to a panel LED is preferable. Also, zero (or as close to zero as possible) RF and conducted noise is a requirement.

Related threads: I think the answer in this thread might come close to what I need. If this solution could meet my requirements, I would need help with how to adapt it for two inputs and to allow both LEDs to be off. Answers in this thread also seem applicable, but again, I would need help in adapting a solution to my needs. This one contains a number of interesting solutions, but again, one logical input, not two.


texts: How to repair solar panels without being able to source an exact replacement diode

texts:
How can I repair a solar panel (replace the blocking diodes) without access to the exact same components?

I have a 100 watt 20volt semi-flexible solar panel marked  PV-XC502 on the junction box, opening it up I can see two components each marked 20S0045 in what appears to be a T0-252 package (or similar). It has a symbol which appears to be a pair of inwards pointing diodes. I assume that each component is either a single blocking diode OR (going by the picture on the case) a pair of blocking diodes.

The problem is that googling the chip markings produces no useful results. Re-soldering a couple of diodes should be within my skill level, but I’m not 100% sure what the components actually are (diodes or pairs of diodes) and without that information I can’t even look to replace with something similar.

The solar panel does still produce a reduced output, so I’m reluctant to start on a destructive investigation, the junction boxes is full of copious amounts of solder which makes it very hard to work out what’s connected to what.

How can I either a) find out exactly what the component is supposed to be, OR b) work out exactly how the existing cells are wired up do I can try to source some similar components.

I have tried to photo the item, but it’s so small and dirty and the markings are so faint it’s impossible to produce a usable image.

UPDATE - When I google I get both the items that @Bimpelrekkie links to. But these don't appear (to me) to be the same component. The tag 20S0045 doesn't appear in either of the linked datasheets, so how's is it possible to be confident it's the same device? or even a like for like replacement? Aren't these two links just random google guesses?


texts:
I'm working my way into an Electronics Technician career diploma and have came across a question that is kind of throwing me for a loop.

I'm kind of confused on which resistors would be considered parallel.  I'm assuming the answer is 6V just as an educated guess but was hoping I could get some elaboration.

Thanks


texts:
I am attempting to use a N-Channel Logic Level MOSFET as a switch for a phone charger that runs on a 42V battery.

I have a resistor circuit with an LDR that currently outputs 3.3v when LIT with a torch and 0v when completely dark. Daylight outputs around 0.7V. The circuit works as expected for a few uses and then the MOSFET fails short and is now always on permanently (even when removed).

simulate this circuit – Schematic created using CircuitLab

My Guess:
Could the load (5V Step Down Regulator/Phone Charger) be inductive, similar to a relay and need a flyback diode somewhere? Placing one on +/- of the charger has no effect on longevity, as well as one on the main +/- of the battery.

The current of the charger should be less than 200ma at 42V for a 5W charger. Could it be higher at startup (it's rated for 30A).

They seem to fail when it is switched on/off more frequently.

MOSFETs can be placed in parallel to split the load, would this help?

I have killed more than 10 MOSFETs so far trying different combinations

The MOSFET is FQP30N06L with this datasheet.
The Phone Charger is this 5V Regulator


texts: Control 5 V load with transistor 3.3 V - Raspberry Pi

texts:
I'm currently having this project where I put a Raspberry Pi, batteries and a touch screen inside a book that can fit my pocket. This screen is constantly on, and I want to be able to turn it on and off with a transistor.

I'll be controlling the 5 V instead of ground because it is also getting ground over HDMI. The base will have 3.3 V, and the output should be 5 V.

I've tried many things with both NPN and PNP.

I'm running a Python script that outputs 0.02 V as LOW and 3.3 V as HIGH.

I'm ending up with the screen being either on/blinking, grey/grey, grey/off or off/off. It stays totally off with 5 V with PNP transistor.

This is curcuit that has almost worked (grey/off):

When GPIO is HIGH (3.33 V):

Monitor: Grey
Base: 4.32 V
Collector: 2.21 V
Emitter: 5 V

When GPIO is LOW (0.02 V)

Monitor: off (no back-light)
Base: 4.38 V
Collector: 1.6 V
Emitter: 5 V

I tried with two 2N3906 transistors to make sure it wasn't broken.

I'm kind of confused over this circuit and it seems that my knowledge doesn't match.

What can I do to make this work? What am I missing?


texts: Arduino Battery Over-Discharge Protection (O-DP)

texts:
I am getting an Arduino Uno soon, and am planning to run off a 8-cell NiMH battery pack (through the power jack). Assuming a .9V cut-off per cell, that'll mean a 7.2 cut-off voltage. How would I wire it to detect the <7.2V voltage and turn off?

Would this Schematic work?

#pseudo-code
if A0 < 3.65v then BUZZ
#buzz makes a square wave w/ PWM to PWM0


texts:
This may sound silly to most, however, it answers a million questions for me, so please have mercy on the down voting, thanks.

A simple example without specifics, when a battery and a DC motor are connected via +/-, the motor spins.

Theoretically, in my mind atleast, an AC-DC adapter(again without specifics) with the wire cut at the output end will have a positive and negative wire. If these were to be correctly connected to the same DC motor as before, the motor should also spin. Is this correct or am I missing a screw?


texts:
I want to design a concentric circle shaped footprint in Altium. The inner one is Vcc while the outer is GND. I tried placing the pad and such but there is no way I can have the outer circle with the clearance as shown.

One way is to place an arc (that is complete). But then how can I assign a designator (pin 1,2) to it ?


texts:
So, my goal is to print (on the standard output) a number using a Nios II system on a FPGA Cyclone II Altera.

MY STEPS:

1) I created the following Nios II system with the Qsys tool (Quartus II):

(NIOS II CPU - JTAG - ONCHIP MEMORY RAM - SYS ID)

2) I wrote the following C code:

#include <stdio.h>
int main(){
    char a[13]="Hello world!";
    printf("%s\n", a);
}

3) I downloaded the system on the FPGA and I compiled and loaded my code using Altera Monitor Program, I ran the code and it works, my code prints "Hello world" on the Monitor Program terminal.

4) So, I tried to print a number and it fails :(

The code:

#include <stdio.h>
int main(){
    int a=3;
    printf("%i\n", a);
}

The error:

NOTES:
I tried to change %i with %d %u

Why it doesn't work?


texts:
So, I drew a two sided PCB of a circuit represented in the picture below. I used the program DipTrace to draw it. The first picture represents the top side. And the next one represents the bottom side.

I wanted to ask is it preferred to change anything and does the space at the bottom right corner that is left there cause any problem?

This picture represents the schematics:


texts: How to build a large WIFI system inside a factory which supports thousands of devices?

texts:
I am a newbie at network and I am trying to find an architecture for a WI-FI system which is deployed in large area(over 50,000 square meters) and connects 1000-2000 devices with a server.

Each of the devices is a robot and will be navigating inside the factory. The server will communicate with each robot, read data from the robot and control the behaviour of the robots. The server connects to the robots through WI-FI.

The requirements of the systems are:

The robots will navigate inside the 50,000 square meters(200m * 250m) factory;
The robots shall be connected to the server all the time. If there is any disconnection and re-connection, it shall happen in 100ms;
The data delay shall be around 100ms;
The communication rate is around 5Hz, meaning there is a send and receive from the robot to the server every 200ms;
The data amount for every communication is around 1KB;

What I am thinking

1.The server will be connected with several wireless APs which are located at the roof of the factory. The APs will cover all the area of the factory.

2.Each robot will have two WI-FI modules on it. The two WI-FI modules always connect to different APs to ensure that when there is a transition from the coverage of an AP to the coverage of another AP there is always an established connection.

Any comments/insights will be really appreciated


texts: Finding Time Constant without voltage source in diagram

texts:
Is this question right in the sense that a time constant can be deduced from this diagram without a voltage supply? If yes, then how do I calculate RxC from this network ? I am very confused.
Edit : my concern and question is whether the teacher should have mentioned an open node where the supply voltage can be assumed, otherwise in some cases the time constant will be 0 ?


texts:
I've seen reverse-mount LEDs which are meant to have the light shine through a hole in the PCB, instead of straight off. Is it possible to just add a drill hole for normal LEDs and just place them upside down before soldering?

Is it possible the lense/substrate will melt if reflowed on a hotplate? If it matters any, I've got 0805 components.


texts: Parallel transistors for brightness control of large quantity of LEDs

texts:
I'm working on an art project that consists of ~180 LEDs with about a dozen fading/flashing PWM patterns, with each pattern group/circuit controlled by a PN2222A transistor on the cathode side, with the transistor bases' signals coming from a microcontroller.
I would like to be able to control the overall brightness of all LEDs simultaneously (not really possible via the microcontroller with how I've programmed it), so I had the idea to use a few leftover transistors connected in "parallel" on the anode side to create a PWM brightness controlling "main bus" for all LEDs. The PN2222A transistors I'm using are rated up to 2A, so I figured putting 2-3 in parallel would allow the control of the LEDs high current draw (~3.6A @20mA each):

I'm wondering if this looks like a reasonable solution? Or is there some reason not to do this in favor of a better way? Thank you very much!


texts: Wiring a bluetooth module into car radio, issue with switching between radio and bluetooth

texts:
I have an old Blaupunkt Radio in my 91 VW golf. I have purchased a Bluetooth module from eBay and I have wired the line out from this into the Left and Right inputs to the amplifier that would normally be used for the outputs from the cassette player. The pre-amp for the cassette player is still wired in also, although the tape reader is disconnected.

From the data sheet for the radio, I can see that when a tape is inserted, the audio source should switch from radio to tape. Here is a link to the data sheet. On page 5 of the linked PDF, on the top right of the sheet you can see the switching circuit for the audio inputs. I have wired my Bluetooth L and R inputs into R1304 and R1305. The input MS is set high when a tape is inserted into the radio.

The problem that I am having is that the two audio sources are playing through the speakers at the same time.

I have a few theories as to why and wanted to see what others thought:

The pre-amp for the cassette player is still connected and is interfering with the switching circuit?
The signal from the Bluetooth module isn't the same voltage as the pre-amp for the cassette so the switching circuit isn't functioning correctly?
Maybe I need to wire the Bluetooth module line out into the cassette pre-amp?

I have some more testing to do this evening, it was getting late and I ran out of time, but if anyone has any thoughts on this I would greatly appreciate the help.


texts: How to calculate impedance of a PCB trace Antenna in Altium w.r.t. a given frequency?

texts:
I am keeping things abstract as I intend to learn and not just copy another design.
So, suppose I am trying to design an antenna of impedance Z and frequency f.
Now, in Altium 18, there is a feature that suggests trace widths for a specified impedance.
Now, what I fail to understand is :

how is that the impedance is not dependent on trace length and only on trace widths ?

how can Altium suggest a trace width without me specifying the frequency ?
I mean to calculate trace
width from Impedance , one surely needs to know the working frequency . I guess, it is only taking
resistance in consideration but then , that would depend on the length too?

Is there a way I can calculate Impedance between any two given points on a trace for a given
frequency ? I want both the resistance and reactance to design matching .

If there is no such way in Altium(which I suspect), then how do people design Antennas these days ?


texts: Voltage drop across each diode and current drawn from battery

texts:
I'm wondering if below configuration forward biases D1.
D2 is clearly reverse biased. Would D1 drop 0.7 V and D2 drop 10-0.7 = 9.3 V?

simulate this circuit – Schematic created using CircuitLab

I know how leakage current flows in reverse bias with one diode: Due to thermal agitation electron-hole pairs get generated inside junction, electric field inside the junction pushes these away in opposite directions to P,N type regions. Battery then sucks them. But with two back to back diodes wouldn't the holes from both D1 and D2 get stuck in the wire joining them? So there shouldn't exist any leakage current?


texts:
I am looking for a way to automatically update the PCB dimensions in my PCB documentation.  I have the X & Y dimensions listed in the title block as PCB strings.  They are currently set as project parameters so the documentation updates as I update the parameters, but I still have to manually update the parameters if I change the board size.

Text from PCB String Window:

Board Size: '.PCB_X' x '.PCB_Y'
Board Thickness: '.PCB_Z'
Component count: .Component_Count
Pad Count: .Pad_Count
Hole Count: .Hole_Count
Soldermask Color: '.PCB_SolderMask_Color'
Silkscreen Color:  '.PCB_ SilkScreen_Color'

The pad, hole, and component count are system variables.  Is there a system variable that I can set the PCB string to automatically update the X & Y dimensions?  The information is in Altium since it is in the PCB Information window:

Which is opened thru the menu Reports->Board Information.

Your help is appreciated.


texts:
I'm doing a project with PiFace, but being a software guy my capabilities apparently end when it comes to a circuit to detect low voltage.

Basically, as far as I understand PiFace input port is +5V with 10kohm resistor. Connect it to gnd and it's "on".

My best guess is something like this, with the input port connected to the transistor. Id' just need to have the right values for resistors and the LED should cut the flow in case the voltage drops below say 4.5V... yeah, as I've said, I have no idea what I'm doing :-)

Is there a simple circuit that would actually work?


texts: How does this radio transmitter circuit oscillate?

texts:
Hello. I am trying to understand how this circuit operates. I understand how the circuit works on the right side of the transistor, but the oscillation stage with the crystal confuses me. It appears that the crystal has no feedback from the output of the oscillator. I researched this and found out that the collector-base capacitance of the transistor provides a feedback path, but wouldn’t that only give a 90° phase shift instead of the 180° phase shift required for positive feedback?
    I have seen similar circuits where a variable capacitor is included with the crystal to adjust frequency. Would that give the phase shift for the remaining 90°? Thanks, your help is appreciated.


texts: How to use PNP transistor as a switch for serial communication

texts:
I am trying to interface a 3.3volt TTY bluetooth dongle to my arduino.  The dongle requires 3.3volt but the arduino's Tx and Rx signals are 5 volt.  Apperently the 3.3volt is enough for the arduino Rx, but the 5volt Rx for the bluetooth will be too much.

I have a couple PNP transistors laying around.  I am not at all familiar with transistors (I do more with large electronics and relays).  I know that a transistor can be used similarly to a relay though.

Would it be possible to control the state of the transistor with the 5 volt Tx from the arduino.  But have the transistor output 3.3volt from a separate power source?

If it is possible.  How can I do this?  Could someone please explain.

Thank you.


texts: How can an AC source be connected in parallel with a DC one (through a capacitor) in a common-collector BJT configuration?

texts:
As far as I understand, voltage sources (regardless they are AC or DC) should never be connected in parallel, since they are not ideal and one would end up charging the other.
However, in the following common-collector BJT schmatics:

an AC voltage source (Vin) is connected in parallel with a DC voltage source (Vcc). Is this possible because C1 is preventing the DC component of Vcc to 'charge' Vin? If yes, that only works if we assume that Vcc > Vin, doesn't it? If Vin would be greater than Vcc, could Vin be charging-discharging Vcc?


texts: I found some WIMA MKBS capacitors, not a dielectric I have seem before.  WIMA has not been helpful so far (nor Google).  Any idea what MKBS means?


texts: PCB Toner Transfer Method - How to remove toner when it fails before etching?

texts:
I am trying to do a PCB toner transfer, however sometimes the transfer is imperfect and the really small traces fail so I would like to start over and reuse the board again instead of etching it.

I initially just wiped the toner off with acetone. But it still left marks where the toner was - I highlighted two occurrences but others are in the image too, see image:

I then soaked it in acetone instead and scrubbed. But the marks remain unchanged.

Is there a recommended chemical to remove it? I do not want to sand or etch it off because the application is in RF and the design is very sensitive to copper thickness.


texts:
I am designing a device that will use a small heating element. The client initially designed it to use an incandescent bulb as a heat source. I want to maintain that as a back-up which will not only provide the necessary heat if the element fails, but also alert the user that the unit is not functioning properly.
My thought is that if the heating element fails it becomes an open circuit. It seems to me there should be some sort of switch, where if one leg opens a second leg will automatically close.
It seems to me a normally-closed relay would do this. Although I'd be using it with current normally running to the element keeping the relay open most of the time. When that current ceases it closes. I'm not sure it works like this, and in my searches these things aren't relatively cheap.
Also it seems to me a transistor might be able to do this. They seem to be relatively cheap, but again I'm not sure it can work like this. Since a resistor seems to be required, I'd need to have it on a parallel leg to the heating element as the element needs the amps to do its job. So the circuit gets more complex.
Is there a better way to do this that I'm unaware of?
A second question if I may. I want there to be a test button to see if the bulb works, the client is concerned of the cost of adding another device to the circuit.
It seems to me if a spring loaded button pushes a piece of metal between a contact on the hot lead and a contact leading to the bulb it will do the trick without adding an electronic element to the board. What I don't know is if the power back-feeding into the open switching device will cause a problem.
Edits, here are the facts I know, the rest I will figured out as I go, which might lead to more questions. Household electrical current in the US, so 120V AC. The bulb is a small nightlight type, about 7 watts. The heating element needs sized to put out an equivalent amount of heat as the bulb. We will use a commercially available cord with an integrated temperature switch, when outside temp drops to 30 it turns on and remains on until outside temp hits 50.
Thanks Everyone.


texts: Problems with a back-to-back MOSFET dimmer for 230VAC

texts:
I've been trying, unsuccessfully, to dim a 60W incandescent light bulb with two back-to-back MOSFETs, similar to this web page:

http://easy-electronics4u.blogspot.co.uk/2012/02/switch-ac-loads-using-mosfets-as-relay.html

My circuit looks like this:

(there is also a 2A fast blow fuse and a 7D471K MOV on the mains input)

Below is the output from my scope:

Channel 1: Live_230VAC
Channel 2: DIM_GPIO
Channel 3: Drain of Q5
Channel 4: Source of Q5 and Q6

Q6 gets burning hot,
Q5 stays cool.
The lamp (obviously) flickers as we are only getting every other half wave.
Thinking about the circuit, I feel that it will be impossible to get a Vgs voltage that is higher than the voltage at the source pin, since the source pin will see the peak of the 230VAC?

Is there a way (preferably simple & cheap :)) of solving this kind of double MOSFET dimmer?

Edit 1: Added revised schematic as per suggestions from @RoyC for consideration (and so that RoyC doesn't have to click my pasteboard.co link)


texts: I want to install a Siriusxm radio receiver in an antique car with a 6 volt system. The Sirius receiver 12 volt power adaptor states that the output is 5 volts. If I wire the receiver directly into the 6 volt system, will that extra volt burn out the receiver over time? If so, what device can be wired in to drop the voltage to 5 volts? I have read here about diodes and SEPIC to do this, but not being savvy in electronics, I don't understand which way to go. Could someone advise me on how specifically to do this? Any recommendations on what I should buy, to include source if known, would be appreciated.


texts: Can audio isolation transformer be used for AC power isolation?

texts:
I am developing my own PLC that is powered off a 24VAC transformer that is shared with a thermostat and some other controller devices. I wanted to isolate the 24VAC going into my PLC to protect it and I've been trying to find some small isolation transformers to attach to my PCB. I found a link off aliexpress for a cheap audio isolation transformer:

https://www.aliexpress.com/item/10pcs-600-ohm-Audio-Transformer-Isolator-Transformateur-1-1-Transformador-De-Transformers-Ring-600-600-Transformation/32692812269.html

Can I use this to isolate the 24VAC? How can I derive the max amps and power loss from the values given by the seller?

Images attached:

I am currently using a half wave rectifier
I was going to configure the isolation transformer
Here is what the audio isolation transformer on my PLC will look


texts: Infineon XMC4200 alternative pin function for I2C using XMClib

texts:
Since i'm unable to post on the infineon XMC forum any more i will try to find help on this forum.

I'm working on my first I2C code with the XMC4200 hexagon kit. I'm using Dave4 with the XMCLib.
I'm trying to use I2C with a PCA9865, the standard address is 0x40(i tested this with a I2C scanner code).
The problem i have now: there is no ACK coming back from the PCA9865.
My first question is:
According to the XMC datasheet, a I2C addres should be shifted 1 position to the left(for the read write bit) or am i wrong at this one? I this is correct is should use the address 0x80, right?
My second question:
Since i have no scope, i'm unable to check if there is really an I2C signal coming from the pins i'm using.
I'm very unsure about the alternative function/pins i choose to work with.
I will post my code(I2C only) below, could somebody verify if this is correct for the XMC4200?
Thanks to everyone!

#include <xmc_i2c.h>
#define PIN_SDA P0_4
#define PIN_SCL P0_5

    /*I2C settings*/

XMC_USIC_CH_t *i2c = XMC_I2C1_CH0;
XMC_I2C_CH_CONFIG_t i2c_cfg =
{
        .baudrate = 100000U,
};

    /* I2C init*/
XMC_I2C_CH_Init(i2c, &i2c_cfg);
XMC_I2C_CH_SetInputSource(i2c, XMC_I2C_CH_INPUT_SDA, USIC1_C0_DX0_P0_4); /*eerst USIC1_C0_DX0_P0_4*/
XMC_I2C_CH_SetInputSource(i2c, XMC_I2C_CH_INPUT_SCL, USIC1_C0_DX0_P0_5); /*eerst USIC1_C0_DX0_P0_5*/
XMC_I2C_CH_Start(i2c);

    /*config pins I2C*/
XMC_GPIO_CONFIG_t   config_SDA;
config_SDA.mode = XMC_GPIO_MODE_OUTPUT_OPEN_DRAIN_ALT2;
config_SDA.output_strength = XMC_GPIO_OUTPUT_STRENGTH_MEDIUM;
config_SDA.output_level = XMC_GPIO_OUTPUT_LEVEL_HIGH;
XMC_GPIO_Init(PIN_SDA, &config_SDA);

XMC_GPIO_CONFIG_t   config_SCL;
config_SCL.mode = XMC_GPIO_MODE_OUTPUT_OPEN_DRAIN_ALT2;
config_SCL.output_strength = XMC_GPIO_OUTPUT_STRENGTH_MEDIUM;
config_SCL.output_level = XMC_GPIO_OUTPUT_LEVEL_HIGH;
XMC_GPIO_Init(PIN_SCL, &config_SCL);

    /*I2C COMMUNICATION*/
/*Address(addr) should reserve an additional bit at the LSB for read/write indication. For example, address 0x05 should be provided as 0x0a.*/
#define PCA9865_ADDRES (0x40)

XMC_I2C_CH_MasterStart(i2c, PCA9865_ADDRES, XMC_I2C_CH_CMD_WRITE);
while((XMC_I2C_CH_GetStatusFlag(i2c) & XMC_I2C_CH_STATUS_FLAG_ACK_RECEIVED) == 0U)
{
    /*wait for ack*/
}

XMC_I2C_CH_ClearStatusFlag(i2c, XMC_I2C_CH_STATUS_FLAG_ACK_RECEIVED);


texts:
I have a question about sensitivity calculations. I have a lowpass Sallen & Key filter. I calculated:

the relative error of the pole frequency due to the relative error of passive components and the respective sensitivities
the relative error of the pole frequency due to the finite gain-bandwidth product of the OPAMP
the relative error of the pole frequency due to the relative error of the gain-bandwidth product of the OPAMP.

My question now is, to obtain the total relative error do I simply add up all these components? Or is there other operation to perform? Do I only add up the first and third components?


texts: 555 timer in astable mode: How can I achieve longer low output than high?

texts:
I'm attempting to make a simplistic solenoid driver circuit using a standard astable 555 timer configuration with a TIP122 NPN transistor. The problem with the current circuit is that the output is typically high and goes low only for short durations. I'd like to invert this but I'm not sure how.

Ideally I would like a high output every 1 second that lasts only for 100ms.

Do I just need to change RC values or utilize the 555 differently?

(The schematic shows a 556, which is what I am currently using. The lamp-looking squiggle is the solenoid and I have added a 1N4001 diode across it in reverse bias.)


texts:
I have a laptop with a battery described as:

  3 cell Li-Ion 57Wh

I would like to know how this compares to a powerbank with 26500 mAh capacity.

How do you perform these kind of comparisons? What is theory behind it? AFAIK:

Wh is a unit of energy = 3600 J (joules)
mAh is a unit of electric charge = 3.6 coulombs

Why are some batteries measured in mAh? In my view, a battery has a certain amount of energy, not a certain amount of electric charge.


texts:
The reference of the comparator is placed in that range, in particular, Vh=1.282, Vl=1.182  meaning that the hysteresis is 100mV.
But I am getting an output which is always High.
May I know why is it coming like that. Attached schematic and Simulation results.


texts: Direct port manipulation gives random result: Delay necessary?

texts:
Setup (Arduino Pro Mini ATmega328p 16MHz, 5V, no pin connected):

When called from the setup(), this works:

pinMode(11, INPUT_PULLUP);
bool identifiesAsFast = digitalRead(11); // always true

This doesn't:

const uint8_t identificationPinBitNumber = PB3; // pin 11
const byte identificationPinBit = bit(identificationPinBitNumber);
DDRB &= ~identificationPinBit;
PORTB |= identificationPinBit;
bool identifiesAsFast = PINB & identificationPinBit; // occasionally false

Pin 11 is not connected, but - as you can see above - I have it pulled high. So I would expect it to always have a value of 1.

What am I missing when doing direct port manipulation?

I get the behavior with four different Arduino Pro Minis. All are original Pro Minis, designed by Sparkfun, made in the USA and bought from Digi-Key. One of them I pulled freshly out of the original bag. I may have to remove and insert the FTDI adapter around thirty times, but eventually I am able to reproduce the issue.

Adding a delay of 100 ms in between pulling pin 11 high and reading it seems to resolve the issue. However, I don't understand why that delay would be necessary.

PB3 for pin 11 is correct, as I verified by connecting an LED and making it blink. See also the pin mapping diagram which can be found elsewhere on the web:

Full code:

// Felix E. Klee <felix.klee@inka.de>

const uint8_t ledPinBitNumber = PB5; // pin 13
const byte ledPinBit = bit(ledPinBitNumber);

const uint8_t identificationPinBitNumber = PB3; // pin 11
const byte identificationPinBit = bit(identificationPinBitNumber);

unsigned long delayDuration; // ms

void turnLedOn() {
  PORTB |= ledPinBit;
}

void turnLedOff() {
  PORTB &= ~ledPinBit;
}

void setDelayDuration() {
#if 0
  pinMode(11, INPUT_PULLUP);

  bool identifiesAsFast = digitalRead(11); // always true
#else
  // Input pullup:
  DDRB &= ~identificationPinBit;
  PORTB |= identificationPinBit;

  bool identifiesAsFast = PINB & identificationPinBit; // occasionally false
#endif

  delayDuration = identifiesAsFast ? 300 : 3000;
}

void setup() {
  DDRB |= ledPinBit; // Set up LED pin for output
  setDelayDuration();
}

void loop() {
  turnLedOn();
  delay(delayDuration);
  turnLedOff();
  delay(delayDuration);
}


texts:
I have been looking at xbees recently but can't seem to find a tutorial on configuring and programming for 3 xbees on the same network - 1 to act as a master the other 2 respond as slaves, but the slaves will do separate functions such as one could be a device for turning on a light the other could be a sensor. So here are a couple of questions:

Is this possible?
What terminology should I be using when searching for this as i feel that this where my research is going wrong.
How are the 2 slaves addressed across the network?


texts:
I am trying to build a basic 2 input summing amplifier using radio shacks 741 op amp. I have a feeling I damaged my IC chip through my wacky experimentation's. But lets run through the math just in case I am missing something. After all, I am new to this!

If I power the op amp with a voltage supply of +-5V and I set one input to 1.28V and the other input to 0 the voltage output should be -1.28V. Simple node voltage calculations and a PSpice simulation confirm this prediction. For some reason I am getting an output of 1.92 V without attaching anything to my inverted and non inverted inputs. So the 1.92 is coming directly from the supply. I was under the impression that the supply did not effect the sum. Where am I going wrong? Or is the chip busted, playing tricks and causing me severe electonxiety.

Any advice? Thanks in advance.

Turns out I can not add images, I am two points shy! Here is the link, sorry for the inconvenience.


texts: How do I calculate capacitor size in relation to LED quantities?

texts:
According to the NeoPixel best practices (which is the exact product I'm using):

  Before connecting NeoPixels to any large power source (DC “wall wart”
  or even a large battery), add a capacitor (1000 µF, 6.3V or higher)
  across the + and – terminals as shown above. The capacitor buffers
  sudden changes in the current drawn by the strip.

Seems to me that the size of the capacitor is linked to the amount of pixels to be used (since more pixels = more max current drawn). If I'm correct, would anyone care to explain how to calculate the capacitor size in relation to the amount of pixels?

Some extra specs:

Each individual NeoPixel draws up to 60 milliamps at maximum brightness white (avg 20 milliamps).
They require 5V.

Update based on comments:

Power supply will be a low quality wall wart that puts out anywhere from 9-15V (but my circuit has a LM7805 voltage regulator that will bring this down to 5V.
The distance from the capacitor to the first LED in the strip will be around 1 inch.


texts: Fastest moving averaging techniques with minimum footprint

texts:
I have tried few running averaging techs for smoothing the change in ADC data in AtMega48 for controlling lights(PWM) when rotating a pot(ADC).

The filters (pseudo codes):

Moving average:

adc_avg += new adc_raw;
adc_avg >>= 1;

8-point Moving Average Filter:

fill adc_raw_array[i] = adc_raw;
adc_raw_array[8] <-- delete left most, move left, push adc_raw.
adc_avg = sum(adc_raw_array);
adc_avg >>=3 ; // divide by 8

I observed that the filters are very nice. But slow in response which is expected.

I am looking for a techniques like Exponential moving average. Said to be more responsive. Is there another like this one?  As it says:

adc_Eavg = α * adc_raw + ( 1 - α ) * adc_Eavg ;

where α is between 0 and 1.

How to code and optimize those; code wise (without using floats) ? Or How would I convert the floats to corresponding integers for making code small, fast and responsive one.

I tried as

adc_Eavg  += α * ( adc_raw - adc_Eavg );

and I kept
    α = 1;

Other then that it wont work as expected. Because I'd've to change all the variables to float.

Please do not concentrate on following statement for the time being but note.
Keeping floats in my code base is filling the program memory from 45% to 137%, in case of

adc_avg = adc_avg * 0.8f + adc_raw * 0.2f;


texts:
I am designing an ADC front-end circuit that will accept a 230 Vrms mains connection.  My goal is to measure the RMS voltage of the mains.

Though not really necessary, I think it would make sense to galvanically isolate the mains voltage from the rest of the board.

This entails using either digital isolation or analog isolation between the mains section and the MCU section of the board.  I was just reading the National Instruments white paper on isolation types and am now wondering what the most cost-effective way of meeting my self-imposed isolation requirement would be.

Analog Isolation:

Digital Isolation:

For the gain amplifier section of the front end, I plan on using precision resistors to scale and offset the AC input:

simulate this circuit – Schematic created using CircuitLab

According to the white paper, the only real benefit of going with analog isolation is that the isolation barrier comes before the ADC, thus adding a modicum of protection to the ADC inputs.  The downside is that this method introduces offset, gain, and nonlinear errors into the measurement and have a reduced operating bandwidth compared to digital isolation techniques.

According the white paper, digital isolation topologies also tend to be less expensive to implement than their analog isolation bretheren.  I have been unable to confirm this, however, as I look through datasheets for the parts needed:

Parts common to both approaches:

$4.50 for Isolated power supply for isolated section (i.e. R1SE-0505-R )
$1 for Voltage reference for ADC gain/offset resistive adder (i.e. MCP1501T-33E/CHY)
$2 Precision gain/offset resistors

Parts for digital isolation:

$11 ADC with integrated isolated serial output (e.g. AD7402)

Parts for analog isolation:

$3 Isolation amplifier (e.g. LIA135STR)
$2 precision gain/offset resistors on MCU side of isolation barrier

or, in short: Digital = $20  |  Analog = $12.50

I'm guessing that this whitepaper assumed digital was cheaper because there is not already an ADC available that can be used, however in my application I have an ADC available on the MCU.

I am hesitant to spend $20 to use a digitally isolated topology, especially since I already have an ADC that I can use.  On the other hand, I am weary of spending $10 for an analog isolation topology that doesn't really have precision.

There has to be a less expensive way to do this, isn't there?

I am starting to think that perhaps I should just scrap the idea of having isolation, or perhaps that I need to start looking at simply using a step-down transformer from mains to MCU board for isolation and live with the fact that the signal I am measuring will have a different shape than the mains voltage.  Thoughts?

UPDATE
As @DanMills has pointed out, another option is to just use a 230VAC transformer on the incoming mains power to accomplish analog isolation.  A search of Digikey shows that the least expensive transformer rated for 230 VAC is $6.80 (canadian):

So, still pretty pricey, but definitely a bit more palateable.  The downside of this approach obviously is that it distorts the incoming waveform and wastes energy.


texts:
Please provide an intuitive explanation of maximum power transfer.

This is a conceptual question therefore I want to ask with an example. I'm wondering in which cases impedance matching is used.

For example, if one has a sensor which can be modeled as voltage source call it Vs. Imagine it is outputting mV level voltage signals and it has 1k output resistance. And if we want to amplify it we would use an amplifier with a very big input impedance like 10Meg so that most of the Vs reach the amplifier input.

But for maximum power transfer the input impedance of the amplifier must be equal to 1k which would halve the Vs reaching to the amplifier input.

If we have a signal to be amplified why would we match the source output impedance to receiver's input impedance? In my example it was not a good idea. And I know that in radio transmission impedance matching is used. But again I'm stuck at the same point. There must be a difference in two cases where we need maximum voltage at the receiver or we need maximum power at the receiver.

Can this be explained by two examples for each case?


texts: I have an AXI4 master on one board and AXI slave on the other (BRAM controller). The data is transferred using Chip2Chip and Aurora as shown in the figure. I would like to initiate several burst transactions, but cannot because the awready signal is LO. So, there's a long pause between the bursts (see the delay between the yellow and blue markers). The BRAM controller (slave) almost always keeps those signals asserted, so the master should always see the ready lines to be HI. However, it seems like the Interconnect that is on the Master's board is holding the awready signal low. Why?.  When I remove the Interconnect from the masters board and connect the master directly to the C2C, everything works as expected.


texts: High Voltage Cascode with MOSFET LT Spice Simulation

texts:
I'm an electronics engineering student and want to develop a high voltage switch with normal Si N-MOSFETs. After some research, I discovered cascode switches for this application. Most of these cascodes use depletion SiC JFETs. But those are expensive, so I tried to develop a circuit with standard enhancement N-MOSFETs. I've chosen the STD3NK100Z (Datasheet), because of the high Vds, the low price and the availability in TO-220 (for the first prototype) and D-PAK (for SMD). Now I'm stuck at simulating the circuit in LT Spice XVII (64bit)...

I used the PSpice Model from here. Simple circuits with this model seem to work fine:

And produce the following output:

However, if I try to simulate more MOSFETs the simulation becomes really slow. My take on a cascode circuit is this:

But LT Spice says my timestep is too small.

It is also strange, that with another MOSFET (SIHP5N50D) model (from here) and the same schematic, LT Spice produces the following Output:

That is roughly what I'm trying to achieve. But the simulation only seems to work with V2 = 2kV. If I try higher values, Spice seems to calculate for infinity.

Changes in the .tran directive don't seem to help. I've tried playing with the Reltol, Abstol, Gmin, Chgtol and Trtol Spice parameters, but to no avail. Does anybody know a solution to this?

P.S. I'm new here, and hope I'm doing this right. If you need more pieces of information feel free to ask.


texts: Need some help trying to identify an IC package for soldering

texts:
Please see the below image, it's a BCM4366 WiFi IC.
I'm looking to reflow/replace one of these ICs and trying to figure out what the package is and how best to solder a replacement. (Reball/paste/reflow etc.)

EDIT:
Should probably have provided some context.
This is for a D8500 Netgear router whereby one of the radios has failed owing to I believe cold solder joints.
I have reflow requirement and am experienced in circuitry and repair. I bought this router because it was faulty (£11 Inc p&p) with the intention of repairing it. Initially thought it was a software issue, tried various firmwares, drivers ect but the radio would not initialise.
Then attempted to reflow the IC but couldn't get enough heat into the board owing to large ground planes and not having a pre-heater at the time.
However, after letting the board cool and turning it back on, the radio did start to work for a few minutes until it disappeared.
I've got an IR Hotplate PCB heater winging it's way to me now as I could have used one with my last project so that will tackle the board heating issue and I'm hoping to just reflow the chip with plenty of flux.
However, I've also got some replacement ICs on their way (hopefully) hence asking how best to solder one of these incase I need to replace fully.


texts: interrupt-on-change on 8051 microcontroller

texts:
I am trying to read the speed or number of rotations pulses of a self-made encoder motor.

I am using an AT89C52 microcontroller. It gives external interrupt on rising or falling edge.

How can I attach both rising and falling edge interrupt in AT89C52?


texts: AC-circuit with resistors and capacitors in series and parallel

texts:
Is there any frequency for E, where the potential between A and B is zero in this circuit?

I tried using the jw-method to get the current, but it became to complex which tells me that there must be a shorter way.


texts: Obtaining 15 V from a single lithium polymer cell

texts:
I want to get 15V output from a  1 cell lithium polymer battery which has a voltage range of 3v-4v.  I am thinking about using a 34063 to accomplish this.  But will this work over a 1v range or do I need a different ic?

edit:
I want to get around 250mA


texts:
I'm designing a circuit that requires me to measure three low value (8-60 ohms) resistors with a hard wired common connection on one end. My ADC doesn't have enough inputs to measure all three at once along with everything else it needs to do.

My two questions are:

What's the best method of current measurement? A Wheatstone bridge will draw way too much power, so I'm leaning towards a constant current source, and measuring the (amplified) voltage drop over the resistors. At 20mA (I don't want to go much higher as the resistors may warm up and change resistance) this gives me a voltage drop range of 0.16-1.2V.
How should I switch between resistors? Automatic switching is required as this device needs to be a one-button operation - plug in sample, press button, receive information label. Is there a better option than two SPDT relays?

Thanks!


texts: Designing flyback converter - minimum primary turns

texts:
Calculating minimum primary turns: when formulas provided they are based on transformer specs that are not always available, like permeability, air gap etc.

In many cases, however, it is assumed that a suitable transformer will be selected by Lp, Isat and coil ratios. Is this acceptable simplification?

It seems to me all those calculations are supposed to be done already by the transformer manufacturer.

Speaking of transformer selection, a lot of DC-DC use much more compact inductors or toroids. Can I use something like these (DRQ, CTX, Polecat) chosen by primary inductance and saturation current and rewind secondaries as required?


texts: ADC conversion value spike during ADC conversion

texts:
Description of the situation

I am trying to get an analog vibration sensor signal to a Raspberry Pi 3 B+.

To convert the analog signal to digital values, I'm using Waveshare High-Precision AD/DA Board (a raspberry pi 3 shield) that includes an ADS1256 ADC chip from Texas Instruments (30 kSPS, Gain 1, 24Bit).

I'm currently using a differential connection to connect sensor output to the ADC. Since the sample code provided by Waveshare did not include continuous mode  conversion, I've tweaked code found on Github (link below) and implemented in my application.

This allowed me to convert data, with conversion speed measured to be around 29k per second.

In order to test the conversion integrity, I've disconnected the analog sensor from the ADC board and instead connected a function generator (sinwave of 1.5V, 60Hz).

The problem

When I plotted and checked the converted data, there were unusual spikes of converted data (Figure 1) even though the sine wave produced from the function generator did not (checked with oscilloscope). These spikes were not periodic and seemed random (Figure 2).

I've looked at the ADS1256 datasheet and Waveshare board manual but could not find any solution to this problem.

The question

What is the cause of these value spikes?
Is there any solution to overcome these value spikes (in terms of hardware or software?)

Figure1

Figure2

Code

/***************************************************************************************************
 * Name : ADS1256_Collect_Continuous
 * Parameter :
 * Return : void
 ***************************************************************************************************/
void ADS1256_Collect_Continuous(uint8_t channel, int32_t numOfMeasure, int32_t *values)
{

    uint32_t read = 0;
    uint8_t buf[3];
    uint8_t del = 8;

    ADS1256_SetDiffChannal(channel); /* change DiffChannal */
    bsp_DelayUS(del);

    CS_0();
    waitDRDY();
    ADS1256_Send8Bit(CMD_RDATAC); // Start read data continuous.
    bsp_DelayUS(del);   // min delay: t6 = 50 * 1/7.68 MHz = 6.5 microseconds

    for (int i = 0; i < numOfMeasure; ++i)
    {
        waitDRDY();
        /*Read the sample results 24bit*/
        buf[0] = ADS1256_Recive8Bit();
        buf[1] = ADS1256_Recive8Bit();
        buf[2] = ADS1256_Recive8Bit();

        read = ((uint32_t)buf[0] << 16) & 0x00FF0000;
        read |= ((uint32_t)buf[1] << 8); /* Pay attention to It is wrong   read |= (buf[1] << 8) */
        read |= buf[2];

        /* Extend a signed number*/
        if (read & 0x800000)
        {
            read |= 0xFF000000;
        }
        values[i] = read;
        bsp_DelayUS(del);
    }

    waitDRDY();
    ADS1256_Send8Bit(CMD_SDATAC); // Stop read data continuous.
    CS_1();
}

Resources

High-Precision AD/DA Board Schematic : https://www.waveshare.com/w/upload/2/29/High-Precision-AD-DA-board.pdf

High-Precision AD/DA Board Sample Code(30,August,2018) : https://www.waveshare.com/wiki/File:High-Precision-AD-DA-Board-Code.7z

Sample Code (ADS1256 Continuous) : https://github.com/jurebartol/Rpi2_ads1256

ADS1256 DataSheet : http://www.ti.com/lit/ds/symlink/ads1255.pdf

Edited

Spikes of converted data(Figure3)

Figure3

ADC board connected on top of the Raspberry pi with GPIO(Figure4)

Figure4

Raw integer Value(Figure5)

Figure5


texts: how to disconnect a data line with a digital output using the smallest component

texts:
Hi i have two stepper motors and an Arduino Uno and i need both the spetter motors to work at the same time but the only way that can be done is if both the corresponding lines for each stepper are connected together but i dont always want them to be connected, so i need to find a way to connect and disconnect the 4 lines for each stepper, i need the components to be as small as possible and i shall use one of the two remaining digital output on my Arduino which can go High or Low to connect or disconnect the lineswith is 5v logic.

What is the best component for me to use and i assumed i would just get four of them and connect them in parallel.

Many thanks and sorry for such a simple question
from Ed.


texts: How does this biasing work with the two 100 ohm resistors and the 5V to create only positive voltages?

texts: The 5 V is a pin in the Arduino Uno and the 100M Ohm is the input impedance to the analog pin in the Arduino.


texts: cache memory capacity and words in cache memory

texts:
Each block of the set associative cache memory has capacity of 4 words of 16-bits, one section has 2 blocks. Whole cache memory has 4096 words.

I do not understand the differences between these bold ones. Aren't they the same?


texts: I have a 1200 Watt hot plate that works great when connected to the grid but I want to be able to run it off of two deep cycle batteries wired in series to an inverter in an off grid situation. The thing is i want to be able to limit the current going to this device to have more fine tuned control on my battery drain. Testing with my killawatt reveals that despite the plate having a rotary knob heat control, this simply cycles the element on and off more slowly, so full 1200 watts on then off for a varying period of time. i want to be able to keep it cooking at say 600 watts continuous. Whats the best device to do this? Something inline on the power cord? Is there something that can handle these watt levels that i could build from parts?


texts:
I need to measure the voltage across the R2 (VA - VB) but it is above the common mode voltage range of op-amp.

simulate this circuit – Schematic created using CircuitLab

How could I do that? I was thinking of a second voltage divider across the R2, but that would affect the gain of the op-amp and I don't think I can analyse it. Though, I reckon that is not a good practise.

simulate this circuit

Then, I thought of using two voltage dividers in each point (VA, VB). But this would also affect the gain of the op-amp

simulate this circuit

Finally, I'm guessing this is the best way I can think of.

simulate this circuit

V1 could vary from 24V to 30V. The ratio of voltage dividers is arbitary taken. I just wanted to show the circuit.
Is it a good circuit? Is there anything better I can do?


texts:
I have a rodent problem which traditional traps and various other measures have have not been able to solve. I want to try to electricfy a metal cage which I have. I don't believe that is as simple as attaching the plus and negative of say a 6 or 9v battery to the cage, or is it?
Would such a voltage be sufficient or overkill for the mice. Obviously I am looking for a quick clean kill.


texts: Torque-Speed Equation for Induction Motor

texts: I am looking for the Torque-speed equation on an Induction Motor that is used to draw the curve.


texts:
I have recently acquired an old neon transformer (rated 12kV) for conducting some low temperature plasma experiments. It is the mid-point grounded style with  a center tap on the secondary coil. I had overlooked these details and I really need to have a single lead at full potential, so I'd like to remove the center tap ground and ground one side of the secondary. I'm under the impression that this will allow the opposite lead to supply a full 12 kV potential (open circuit, that is).

Will removing the center tap and grounding one end pose any threat to the transformer (such as arcing through the potting material) and how should I ground the opposite end/is it necessary to install a separate ground rod or can I use mains?

PS the NST (neon sign transformer) is an Allanson 12kV 30mA (no-GFI)

Thanks in advance,
Mitchell


texts:
In the context of solar cells, some films such as aluminium oxide reduce recombination by "field effect passivation". I find this mentioned often, but can't find a definition or clear explanation of the mechanism anywhere.

It seems to be something to do with the concentration of negative charge at the surface, which leads to a layer just beneath the film with a high concentration of holes, but it's not clear to me how this leads to passivation.


texts:
I want to connect a microcontroller with a PCIe x1 port to an ASIC with PCIe x4 interface. It is not possible to connect microcontroller to lane 0 of ASIC, and it should be connected to other lanes (like what depicted in picture). is it possible to connect lanes this way and work with microcontroller PCIe x1 mode? In general, could we connect PCIe lanes not in numbered order?

ASIC PCIe is gen 1 compatible with PCIe Base Rev 3.0 and supports x1, x2 and x4 modes.

It would be great if link some documents.


texts:
Ok, so for the past few days, i've been getting more and more interested in Peltier Modules, and i've finally decided to make a portable mini fridge with one. After MANY long hours of research, part selection, crying, and cussing, I finally came up with a circuit diagram that seemed pretty solid.

That is, until I showed it to my chemistry teacher. (He is VERY experienced with computing and circuits)

He says that if I hook up this circuit, it will most likely overload and die out, but he doesn't know why, because his teachers didn't explain it in great detail. He said that I should hook up a resistor and a fuse, but didn't tell me the specifics: how many Ohms, voltage, etc...

Keep in mind, this isn't my first time playing around with circuits. I have grasped the basics and I understand some stuff. However, this is my first time messing around with batteries in a major way. I.E: I have used batteries, like 2 AA batteries for my small breadboard projects; NEVER have I used a 12V, 20 AMPHOUR battery before! So when it comes to the big stuff, i'm a total noob.

I would appreciate it if someone can help me fix my circuit before I turn it on for real! I really would not like to throw away $160 in parts!

A picture of my diagram is below: NOTE: Some stuff has changed, like the temperature sensor now being one unit, not a probe and main unit.

Edit:

ATTENTION!

If anyone can provide me a diagram or design schematic of my fridge that works without overloading or not working in general, you will receive my eternal respect and gratitude!!!


texts: I was shipped a USB dongle in a small pink baggie.  If it's an anti-static bag I would love to re-use it.  How sure can I be that it is, and is there a way to test it?


texts: How to safely limit current for DC12v 30a?

texts:
I am plating my vias with electrolysis, and I need to safely limit the current so it doesn't go over 30 amps.

The power supply I'm going to order is, you guessed it, 12V 30A.

I've calculated the need for a 0.4r resistor, but good luck finding a 0.4r resistor rated for 360+ watts.

I'm following this guide, unfortunately they don't mention how many volts you are supposed to use, they only give you a calculation for the current. (They do say 0.25v, but only when you are first putting the board in the bath)

Is there anything else I can do? Hopefully that doesn't break the bank?

I just had an idea while writing this, would using 4 100 watt, 2 ohm resistors in parallel work(to get it to 0.5r)?


texts: What will happen if the prime mover driving synchronous machine is accidentally disconnected?

texts:
What happens to a synchronous machine connected to an infinite grid, acting as a generator, when its prime mover fails i.e. when mechanical input at the shaft reduces to 0?
I'm assuming that the protective equipments which should've tripped unit in this case failed to do so.
EDIT:
I thought that electromagnetic torque would not change when prime mover torque goes 0, which were wrong as I realised after disccusion in comments.
I found answer on some another Q&A site to similar question which confused me. I'd like to quote a few points from there here:

Here are the various possibilities for a synchronous generator connected to grid when Prime mover is accidently decoupled. The mode depends on whether the field winding is excited.

Field Excitation is available ( Field ON) : Machine will work as a         Synchronous Motor rotating in the same direction.

Field Excitation is failed ( Field OFF)

Cylindrical rotor machine : work as Induction Motor running in same direction with speed less than synchronous speed.
Salient pole machine : work as Reluctance Motor running in same direction at synchronous speed.

I now understand point 1 (field = on case), but I don't completely understand filed = off case.
It appears that motor operating as induction motor case is written considering that damper windings and even field windings will produce induction motor torque.
Question 1 : Is it theoretically sound reasoning if we consider that field winding won't burn and grid is infinite?
Question 2  : Practically it would burn field winding right? And will also cause violent changes at bus to which it is connected?
As far as reluctance motor case is concerned, I believe it is written owing to small reluctance torque which is present in synchronous machines and is independent of excitation. Based on this EE.SE question, I am concluding that it can run at synchronous speed due to this small reluctance torque provided it overcomes load torque on its shaft due to friction and windage. It is stated over there that is very unlikely however since reluctance torque would be very low.
Question 3 : But even if reluctance torque was capable of overcoming air friction, how likely it is that machine after this violent fluctuations would remain in synchronism? In fact I would like to ask the same question for first case where it runs as synchronous motor also. Isn't it more likely that following violent oscillations motor would be pulled out of synchronism? Just because 'it can' stay in synch, doesn't means it would, right?


texts: I am getting this error when I burn with eXtreme Burner.  The LED turns on but does not blink. I am using ATmega8 AVR board.


texts: How closed loop temperate control works in Ecigarette / Vaporisers

texts:
I have been reading about the use of heating elements made from Nickel and Stainless Steel in Ecigarettes. They are used as their resistance changes approximately linearly over the temperature range that it would be used.

If you can measure the resistance, you can approximate the temperature and control it. The thing I'm unsure about is how you can measure the resistance of the heating coil?

Is it possible to measure the resistance while the coil is on, or does it require the coil to be powered down briefly to measure it. I'd love to know what circuitry is needed between my microelectronic, and heating coil to measure the small change in resistance.

Any information would be greatly appreciated.