texts: Why am I getting this error when placing a capacitor in Proteus?

texts:
I have a circuit in Proteus with a few logic components (logic gates, counters, comparators, adders, etc).

I have a 3 input AND gate which two of the inputs are '0' and the other one is a Clock signal, even when 2 of the inputs are '0' I have some transients in the output signal of my and gate as you can see in this picture, I don't know if it is intended or a Proteus bug:

So I solved this putting a .1 uF capacitor to ground in my 4-bit counter clock input and everything is working perfectly.

Now I want to package this circuit in a component to use it in another schematic as I always do, I create my component and attach to it a hierarchy module which is the circuit I created. The problem is that when I add the capacitor on this way:

When I execute the simulation I get this errors:

  SPICE failed to connect pin V+!  U45_U2_#P

  Node U45_VDD not found whilst binding pin V+ of U45_U8_ADC#0001!

If I disconnect the capacitor only to from the IC simulation works but I got the problem with the clock, no matter where I connect the capacitor, If I connect it to any IC I get this error. Why? How can I get it working?

The circuit is working perfectly but when I put it inside the component I get this error. I am using Proteus 7.7 SP2.


texts: What is the package name of this Through Hole LED?

texts: Does anyone know the name of this package type for an LED?  Does anyone know where I can get one like this in red?


texts: Running small external speaker via 3.5mm connection

texts:
In short the question is: how can I get the audio from the 3.5mm port of my Raspberry Pi board to play through a small external speaker? Space is a concern in this project I will only have a few square inches and it only needs to be loud enough to be audible within ~20 feet.

More details: I'm working on a Raspberry Pi project where I want to have it play some sounds. The board itself will not be hooked up to a monitor or anything at run time so the audio will need to come through the 3.5mm jack. I raided an old clock radio to steal the speaker out of it and stripped one side of an old set of headphones so that I could connect the wires to the speaker I pulled. The sounds are playing fine through the intact earbud but when I connect the bare wires to the speaker I don't hear anything.

What can I do to get this working? Do I need some sort of amplifier? Are there better options than what I'm trying? I was hoping that the small speaker would just run off of the power coming through the headset wires.


texts:
I bought a bunch of very cheap 18W LED lamps.  I love them; they look great and the light is excellent, however the drivers throw out a lot of RFI and is interfering with my radio (quite bad at 50MHz, but also significant from 25MHz-150MHz).  The interference is being caused by the driver (I can outline how this was diagnosed if helpful; the radiation all seems to be coming from the transformer though it decreases a little when I add common mode chokes to the AC input and DC output wires).  This has to get fixed.

I have been reading many of the related questions regarding LED drivers and have learned a lot.  Am experimenting with capacitors and ferrite to reduce the RFI.  Ultimately, I suspect I will end up replacing the driver.  How do I know the new driver will be any better than the current one?  What should I look for?  Are there any certifications that matter?  There are plenty to select from at the usual electronics component stores.

In case it helps, I think this is the driver with the RFI condition:  https://www.dhgate.com/store/product/led-driver-input-ac85v-265v-output-36-63v/259582128.html  The resemblance is uncanny; the specifications are the same, but my driver's PCB has the DC output wires slightly closer together.


texts: Why is it universally stated in so many places that the Base Current Ib controls the collector current Ic in a Bipolar Junction Transistor when I guess it is pretty obvious that its the Emitter Base forward bias voltage that will be responsible for the change in the base current.. Making the Vbe controlling factor of Ic.. It is all very confusing


texts: How to create address independent code for STM32F746?

texts: I need to create an address independent, dynamically reallocable code for STM32F746: a code (program) that I will store in one place (i.e. external Flash), than load it into the RAM (internal or external SDRAM) to some other (always different) address and run it. Basically, all internal program calls should be relative calls and relative jumps instead of traditional, absolute calls and jumps. The code will be loaded from th Flash to the RAM by the "code loader" that will run in the background - the part I have already resolved. Someone knows how to set GCC to create this kind of code? I am using Eclispe STM32 as a development IDE. Thanks in advance.


texts: Can I reinsert a partially discharged 12v battery back into a solar battery bank?

texts:
These two questions are close to what I'm asking, but I'd like some specific clarifications:

How do we charge a small 12V battery from a large 12V battery bank

Increase the capacity of a 12v battery bank by adding new batteries

So, I have a sort of rag tag 12v Deep Cycle battery bank that is normally on a trickle charge. It contains a 56Ah (2yrs old) and a 35Ah (new) as the two main batteries that are not removed. I also have a couple of smaller batteries that are trickling with the mains most of the year. They are a 4.5Ah and 12Ah. This entire bank is used to power my telescope a few times a year. When we go to Burning Man, the two smaller batteries power the lights for our two bikes at night.

Through the course of the night these smaller batteries are discharged a fair amount, but probably not below 50%. The mains stay put and power a small fan that runs 24/7 and the LEDs for interior lighting. The mains may only discharge at most 20% over the course of a given evening. The 35Ah is new (replacing an worn out 18Ah) and hasn't really been properly cycled yet.

So, before we turn in for the night, I take the smaller batteries off of the bikes and plug them right back directly into the battery bank. No circuits or anything, just straight wire to wire contact (I'm using power poles and power pole splitters).

In the morning, a 30w solar panel and 4.5A charge controller come "online" and begin to charge the entire system. After a few hours of daylight, I'll turn on a small AC inverter and charge cameras, 18650s and phones (mostly the 18650s as they power other night time LEDs). All 12v batteries are just shuffling around whatever charge to wherever it's needed. I've never really analyzed the system outside of how discharged everything gets, and how much energy is coming from the solar panel during the day; mostly so I can move the panel to get the best angle. I've done this in the past years and it seemed to work, but I'm curious about the science behind "shuffling energy around wherever, whenever".

My question is if this is good, bad, or could be better? Is it bad to have a smaller battery at a lower voltage suddenly directly connected to a larger battery at a higher voltage bad?


texts:
This is the problem:

And this is my attempt to solve it:

For (1):
I don't know how to get vgs or how to use the hint to get rid of it.

For (2):
I assume that my solution is right but should I add details on how did I get Rout ?


texts: Do digital signal isolators shift the level of the signal

texts:
I am using 2 digital signal isolators, the ISOW7841 and the ISO7730.

The datasheet does not seem to explicitly say that if a signal coming from the 5V side comes out 3.3V on the other side or vice versa. I just want to make sure.

Do digital signal isolators inherently shift the voltage level of the signal?


texts: How to roll of dc gain to unity via an opamp ac amplifier..?

texts:
The following circuit is of an opamp ac amplifier..

The text says:

If only ac signals are being amplified, it is often a good idea to "roll off' the gain to unity at dc, especially if the amplifier has large voltage gain, in order to reduce the effects of finite "input off- set voltage.

How exactly the capacitor help in putting the gain of amplifier to unity at dc inputs(input bias currents)..i mean..look the capacitor is attached in parallel acting as low pass filter i.e shorting all AC to ground..which means attenuated dc output voltage will pass to the inverting input of the opamp causing dc amplification(opamp  action)..which is against what is said in the text...

please help....


texts: Effects of Different AC Adapters On Various Electronics

texts:
Long time programmer starting to learn about electrical engineering a little bit.  I have a Raspberry Pi, an Arduino, and various simple projects I've soldered together out of kits and schematics friends have given me.

Recently I moved and lost many of my AC adapters.  I found I was able to use different ones from other devices.  AC adapters from devices such as the original kindle, old accessory USB AC adapters, old and new Apple AC adapters, and many others that do not have a USB input but rather the older style (I forget the name of the connector on the end, some sort of DC power connector Arduino UNO's have one).

So an example of what I'm asking is this:  What effect does it have using say an Amazon kindle AC adapter (or any other mismatched brand adapter) with an iPhone lightning to USB cord?

Specifically, my Arduino/Raspberry Pi are using random usb min/micro cables plugged into completely random AC adapters.  Most of which have no indication of their specifications.  What effect could this have?  I have another dubbed a "Fast Charger" that puts out (from what I can tell) 2-3 amps based on the voltage.

Another example would be the Arduino DC power connector, I also have the same connector on a small breadboard power supply.  I find anything that fits seems to work in there.  What effects might this have?

Thanks


texts:
I am doing a filter analysis of a simple network filter, requiring drawing some equivalent circuit to simplify the expression and analysis of the transfer function.

The issue I've got is regarding a simplification step on 2 RC cell in parallel :

In one hand, the equivalence seems right : I've got two identical RC cells in parallel with the same voltage across each of them. So in each branch I have the same impedance, thus the same current, thus each cap will charge at the same speed. This will be equal to a 2 time bigger cap we a 2 time weaker resistor.

However, in the other hand, when I try to calculate the equivalent impedance of the 2 parallel cells, I definitely see that the result is different than an \$ (R/2)(2C) \$ impedance :

$$
\frac{(R + 1/jCw)(R + 1/jCw)}{(2R + 2/jCw)} =!    \frac{R}{2} + \frac{1}{j2Cw}
$$

So, is this equivalence suitable in a filter analysis purpose, or did I miss something with my calculations/ understanding ?

Thank you very much,


texts: Least expensive way to plug in a microcontroller into 120V (without wall wart or batteries)

texts:
I need to be able to power a Atmega168 by plugging it into a wall.  The circuit is a little bit more complex but not too much.  The Atmega168 needs between 1.8V and 5V at 200mA.  The ideal solution needs to be contained all on the PCB board.  No wall warts or batteries.

What is a good strategy or set of components that will allow this to be done safely and inexpensively?  I'm new to the area but I have heard things about switched-mode power supply.  Also, efficiency is not very important as long as it is not hot to the touch.


texts:
My understanding of the audio domain is very bad and I apologize for that.
In a Wikipedia article, they say in the "History" section that
"Those headphones used with early wireless radio had to be more sensitive and were made with more turns of finer wire. Impedance of 1000 to 2000 ohms was common, which suited both crystal sets and triode receivers. Some very sensitive headphones, such as those manufactured by Brandes around 1919, were commonly used for early radio work."

In the "impedance" section, they say that "As the impedance of a pair of headphones increases, more voltage (at a given current) is required to drive it, and the loudness of the headphones for a given voltage decreases".

Aren't these two assertions contradictory? if a headphone with high impedance is highly sensitive, should not a very low voltage be sufficient for hearing something?


texts: This may seem a very silly question, but does a servo draw more current when it's moving? I need to be able to log when a servo flips, and being able to log the current drawn from the battery pack seems to be the most obvious and simple solution


texts: RS-485 using USART or UART port on STM32

texts:
On STM32F405 MCUs there are USART ports as well as UART ports available. If I need to implement RS-485 communication then which one of these should be used, USART or UART? Or are both of them equally good for RS-485 communication?

I have searched through the datasheet as well as reference manual for the MCU, but it does not provide additional information regarding the RS-485 implementation.


texts: I'm trying to set up a PCB with an atmega168 and no programming header. I intend to use a serial bootloader (there is a ft232 on the board) to reprogram but I am wondering about the best way to program the bootloader on. Has anyone else tried this before? I am having trouble sourcing a tqfp-32 zif socket.


texts: Never seen this kind of op amp. How do I solve for voltage output?


texts: Computer bus frequency and electricity frequency

texts:
From http://en.kioskea.net/contents/pc/bus.php3

  A computer bus is characterised by the amount of information that can be
  transmitted at once. This amount, expressed in bits, corresponds to
  the width of the bus, i.e. the number of physical lines over which
  data is sent simultaneously. A 32-wire ribbon cable can transmit 32
  bits in parallel. The term "width" is used to refer to the number of
  bits that a bus can transmit at once.

  Additionally, the bus speed is also defined by its frequency
  (expressed in Hertz), the number of data packets sent or received per
  second. Each time that data is sent or received is called a cycle.

  This way, it is possible to find the maximum transfer speed of the
  bus, the amount of data which it can transport per unit of time, by
  multiplying its width by its frequency.

  A bus with a width of 16 bits and a frequency of 133 MHz, therefore,
  has a transfer speed equal to: 16 * 133*10^6 = 2128*10^6 bit/s.

Also if I understand correctly, a signal/data transmitted in a
computer bus is actually an electrical current with its electricity
frequency.  The power supply unit on the power chord for a computer
is a AC->DC converter, so is the electricity frequency zero in
computer buses?

I wonder if the bus frequency and the electricity current frequency are the same concept? If not, how are they related?

Also if I understand correctly, cables  such as USB cables and Ethernet cables are also computer buses. So the above questions are asked for them too.

Thanks!


texts: would a 5V/1.25w solar panel be able to charge an iphone 6?

texts:
I found a small solar panel with this spec:

Power: 1.25W
Voltage: 5V
ma:250

this is an iphone 6 batery:

Current: 1809 mA
Power: 6.91 Whr
Voltage: 3.82 V

Would it work if I just modify an iphone cable by cutting the usb part and solder the wires in the solar panel positive and negative and then plunging the lightning part in the iphone? And then how long would it take to charge?


texts: Field weakening effect on stator voltage

texts: In case of field weakening of PMSM, we weaken the rotor flux along d-axis to increase speed. I sort of understand the fact that the motor consumes id and hence iq reduces since there is a current limited curve (enter link description here) due to inverter current limit. Likewise is there a limit on voltage applied to the stator from inverter? I guess, there should be due to new back emf due to reduced flux, but cannot reason out further. I am unable to search for good articles on this, and I hope someone can point me in right direction.


texts: Unusual Voltage Spike at minimum Voltage Peak

texts:
I recently started to get into electronics. I am messing arround with amplifiers right now. I’m trying create a unity gain amplifier. I hooked the amp up to a dc supply then threw in an AC signal and measure the input and output voltage on an oscilloscope.

This spike will cause a lot of issues when I construct an active low pass filter. Any ideas on why this is there?

I attached some pictures to help. I marked the dc supply input and this is a LM358 Dual Op Amp. Thanks!


texts: Why is my microphone circuit not working?

texts:
I'm trying to make a simple microphone/speaker circuit with a PreAmp and an Op-Amp. Currently, the speaker just outputs a high frequency squeal, and not anything from the microphone.

Looking at the schematic, is there anything you can see that I've done wrong?

Datasheets:

Preamp (INA217) http://www.ti.com/lit/ds/symlink/ina217.pdf

Op-Amp (OPA1652) http://www.ti.com/lit/ds/symlink/opa1652.pdf

-5V (MAX1044) http://pdfserv.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf

Edit 1:

I've discovered some good news and some bad news. First, the good news! I've eliminated the high pitched tone from the speaker by connecting pin 1 of the MAX1044 to pin 8. The bad news... the circuit still doesn't output any sound from the microphone. So, I've simplified the circuit to try and isolate the problem:

More good news! Eliminating the OPA1652, I get actual audio from the microphone through the speaker and can adjust the mic gain with the pot and actually gets quite loud on a cheap pair of earbuds.

Revised question: Where have I messed up when it comes to the OPA1652 and how should I wire it differently?

For what it's worth, the end goal is to make a small audio mixer. Multiple mic inputs and a single output signal.


texts: What is an audio output transformer? Is it the same thing as an impedance matching transformer?

texts: What is meant by an audio output transformer, does it mean that it is designed to operate at audio frequency or to match impedance?


texts: Capacitor in parallel with a resistor between live and full bridge rectifier

texts:
I have an LED light bulb and dismantled it to look at the circuit inside.

I made some google search for pcb but couldn't find any relevant info about FST-855 or FST-854:

After drawing the schematic, I could not figure out what is the purpose of some of the elements. Here is the schematic (sorry for hand drawing):

I was expecting to see the electrolytic cap however did not understand the reason for film cap. Can you tell me why there is this "capacitor in parallel with a resistor" in between Live and full wave rectifier?


texts: What happens when discharging coin cell battery too much?

texts:
BACKGROUND:

I'm working on a project where we use the nRF51 Bluetooth low energy chip, and our first prototype boards just arrived.

So I've made some power measurements trying to calculate the battery life:

When idle: 3,1uA
When bluetooth connected: 4,5mA

The bluetooth won't be connected that often, so this I can actually live with the resulting battery life for the prototype (gives me around 17-18 weeks battery life).

We're using a Panasonic CR1216 battery: https://industrial.panasonic.com/cdbs/www-data/pdf2/AAA4000/AAA4000C277.pdf

And just now I realised that the battery voltage takes a good drop when the bluetooth is connected for a longer time. The max connected time is 10sec and there I got:

Start: 2,99V drops exponentially to 2,7V over 10sec.

When the bluetooth disconnects it slowly climbs towards 2,99V again. I've waited 10min now and it is around 2,96V.

QUESTION:

In the battery datasheet I can't find anything about max discharge current? But clearly the 4,5mA is too much? What will happen to the battery's 25mAh? (I know that it is hard to give a specific number, I'm just interested in knowing if my battery will die within 2 days instead of my 17weeks).

EDIT :----
I've found the similar battery that says max cont. discharge current = 1mA http://www.rossmannweb.de/files/File/Kataloge/CR1216_Renata_Rossmann.pdf


texts: Capacitors as sensor output data storage?

texts: Can we use capacitors to be the input of an opamp? If we have a sensor and we store the value of the sensor in a capacitor, and we do that 2 different moments of the day (different capacitors) can we compare those 2 values? And how we will connect the capacitors to the opamp? Do we need to ground the plates with negative voltage?


texts: Inrush current in the Boost Converter during start

texts:
I am making a 400V 1kW boost converter but in the LT-SPICE simulation, it is drawing a huge current of 50-60A at the start for 1ms-3ms, but the current comes down to 12A after that.
The inductor current rating is 20A and I will be making PCB trace for 25-30A rating. I am afraid that the large current at the start might damage the costly components and PCB trace.
Please suggest me how to solve the problem and what do people do In practical boost converters?


texts: What is an op-amp's differential input impedance?

texts:
I've heard of differential voltages, but the concept of a differential impedance is new to me.
Suppose we are trying to calculate/derive the differential input impedance of the following difference amplifier:

Then what would that mean and how would we go about that?
Pages such as this give information about the impedance seen at the inverting and non inverting inputs to the op-amp but they make no mention of the differential impedance, which leaves me stuck looking for answers. This post is very similar and gives us the answer R1 + R2 (which in our case is really R1 + R3), but there is no explanation of how we arise at that result, and this is where 'im stuck.
Thank you for any help and have a nice day.


texts: Driving P-Channel MOSFET with switch to Ground

texts:
My understanding of working with P-Channel MOSFET's gave me this basic schematic which I'm sure is missing a few things here and there.
My load side will be connected to a complex load with a boost converter, microcontroller, IC's
and a bunch of other things, so I'm using a P-Channel to ensure I have a valid reference
to ground. The LED and resistor in here are just for reference. The actual load is likely sensitive to ground-shifts [AT90 MCU], otherwise I'd much rather use an N-Channel.
I am planning on using a toggle switch to turn the whole circuit On and Off, but the switch I want is not rated for enough current unfortunately [I need it to be quite small]. Thus, instead of putting it in-line, I'm using it to "drive" a MOSFET instead. My goal is for the entire load side to be off when the switch is one way and on when the other.
Will this super simple circuit accomplish the job or am I missing some current limiting resistors somewhere along the way? Note that MOSFET part number is just arbitrary. I'm going to be looking for one with a much lower gate threshold voltage instead.


texts: Best way to estimate number of 'active' cell phones nearby

texts:
I work in a place where we're very interested in ways to measure occupancy, one way being to extrapolate this data from an estimate of the number of cell phones near to a fixed point.

How does one measure the number of nearby 'active' cell phones; 'active' meaning they are transmitting data over a cellular network (3G, 4G, LTE, etc.).

Is there some way of tuning an RF receiver and then measuring the volume of traffic within that frequency band?  I assume that it can't be done easily via 'analog' means, e.g. with just an aerial and a spectrum analyser?

How else could we passively estimate the number of nearby active cell phones?

Footnote: We wouldn't need to capture, or decrypt, any of the data, this is not a snooping exercise.


texts: How to send data through XBee using ATMega328?

texts:
I bought

Seeeduino Stalker
UartsBee
Two XBees

When I physically connect (1), (2) and the computer USB, I can receive on my computer data sent by (1) at 115200 Kbps. But when I physically  disconnect (1) and to (2), and link them again using the XBees the computer receives no data.

I noticed that in (1) the UART Tx and Rx are directly connected to XBee's Dout and Dint. But in (2) there are 1k resistors in each of those connections. Can such resistance be the cause of the problem?

The UartsBee is configured to use 3V, and I tested both connecting and disconnecting the DTR interrupt from the XBee to the ATMega328 (there is a jumper slot for it on (1)). The board is supplied with a 9V 200mA wall adapter. Both XBees were installed pointing the closest edges of the respective boards.


texts: How to connect 3 cell series Li ion charger and protection IC for each cell?

texts:
I am using max745 4 cell Li-ion battery charger to charge 3 cells in series.
I want to put additional protection IC for each cell (NCR18650pf). Because I need to run the max745 always on as a backup rechargeable pack.

I am going to use
AP9101CK6-AETRG1DICT. (protection - OV/UV/OC/short circuit)

AP9101C have P+ and P- pin.
In my case, I have 3cells in series,
If I connect AP9101CK6 IC per cell (each cell have one AP9101CK6 IC)
Is follow configuration correct?

1st cell (1st AP9101 IC) P+ --> BATT pin of max745

1st cell (1st AP9101 IC) P- --> 2nd cell (2nd AP9101 IC)P +

2nd cell (2nd AP9101 IC) P- --> 3rd  cell(3rd AP9101 IC) P+

3rd cell (3rd AP9101 IC) P- --> GND of max745

same time AP9101C P- the pin is connected to common GND as shown in the circuit
will this become a short circuit?


texts: Under what circumstances is one better than the other? I can't seem to find much data on their use, as opposed to their resistances.


texts:
I am building MP3 player. Some time ago I was asking about feasibility of building headphones driver based on D-class amplifier. Now I am tired, I want to go for simple R-2R network, followed by opamp.

Here is what I am trying to do:

I need to get 44100@16 bit stereo sound.

As I don't have crystals which are multiple of 44100 (the only frequency I need to support), I oversample sound to let's say 125kHz (from 25Mhz crystal). Then I output data from uC to 595 serial counters, and latch it in hardware to avoid any jitter due to interrupts and stuff (but if I would set it as highest priority interrupt, it might work just fine even when driven directly from uC).

Just before latch I turn 595/uC outputs into Z-state to avoid spikes during transition.

Then R2R(0.1%), then opamp, then headphones. As I might get some non-linearity, I can calibrate each output code individually on 24-bit precision ADC with precision reference voltage source I have, and store calibration values into flash.

Will it work and produce decent sound quality, or are there any pitfalls? I know that it's easier to get audio DAC, but seems like there are not much available, and what is available costs ~20$, and I am not a big fan of waiting 2-3-4 weeks for a part...


texts: Output current of step-down switching regulator

texts:
Could the output current of step-down switching regulator be larger than its input current?

Assuming that the efficiency of your switching regulator is 90% and you are converting 5 V to 1.8 V. If you measure that input current is 100 mA, do you expect that the output current would be 250 mA?
(5 V * 100 mA * 0.9 / 1.8 V = 250 mA)

If so, where do the charges come from?


texts:
Consider the below circuit with it solution. We need to find the current io3.

My question is why we have a -ve sign in the equation of i03 ?


texts: When and why did 5.8 GHz become an ISM band?

texts:
It's common knowledge that the 2.4 GHz band was set aside for industrial, scientific, and medical (ISM) purposes due to its use in microwave heating. From what I've found, the United States proposed the creation of international ISM bands at an ITU convention in Atlantic City in 1947. Page 464 of this PDF of scanned documents from the convention (source) contains the U.S. proposal, which suggests five frequency bands centered at 13.66 MHz, 27.320 MHz, 40.980 MHz, and 2.45 GHz. Page 270 contains a concurrence from the French delegation, which proposes 13.32 MHz, 26.505 MHz, and 39.96 MHz. (There are current ISM bands around the middle of these proposed frequencies.) However, the 5.8 GHz band is not in the ISM proposals. The radio regulations (PDF page 57) that came out of the 1947 meeting list 5.65 - 5.85 GHz as an amateur radio band.

The ITU's search engine is pretty terrible, so I haven't been able to find when or why they declared 5.8 GHz to be an ISM band. A more recent document dated (1994-2007) suggests that 5.8 GHz is used for "environmental space heating" "bulk thawing and cooling", and "RF lighting", but I haven't found many mentions of those on Google. There's a mention of 5.8 GHz being used for wireless power transfer, but all of the examples are 2.45 GHz and below.

So why was 5.8 GHz chosen, and when did it happen? Microwave heating is apparently pretty flexible, so why that frequency in particular? I'd have expected 4.9 GHz, since it's a harmonic of 2.45 GHz. Is 5.8 GHz heating commonly used today, or is there some other common ISM usage of that band?

EDIT: To clarify, I'm not asking about the use of the 5.8 GHz band for unlicensed telecommunications, or about the purpose of ISM bands in general. I'm asking specifically about ISM (non-comm) uses of the 5.8 GHz band, and when it was designated for that purpose.


texts:
I have chosen a power harvester to power a few things as part of a wireless system.
This one is the one I have and it seems to be operational:

http://www.powercastco.com/PDF/P2110-datasheet.pdf
http://www.powercastco.com/PDF/P2110-EVB.pdf

It provides the proper voltage set around 3V, and otherwise fits the RF frequencies required including the range of dbms .

However, I want to characterize the rfid system further than the nominal values given on the data sheet. i.e. get experimental values as well as relevant information relating to my use case.

I have standard laboratory tools such as a signal generator, oscilloscope, etc.
I have already gotten charge/discharge time of a capacitor at a given frequency and dbm. Further, I want to measure the charge times with different loads.

For my prototype, I will use the evaluation board with capacitors on it. My issue lies in that the power harvester only outputs one DC voltage at the threshold of 1V at the capacitor. This means that as I discharge it, and my reading goes to 0V for the output, the capacitor still has energy stored at that 1V threshold, and my Vout reading remains 'useless' with a 0v. As such when Vout is 0V and thus not providing power or discharging the capacitor.
I am using the Vout and GND pins as well as the capacitor pins for readings.

How can I characterize this threshold, and the discharge past the threshold? What other things should I measure about the power harvester? Perhaps I am missing some information to do with the capacitors.


texts: What are stepper motors commonly used in?

texts: I like finding motors and parts from recycled electronics and I want to find some stepper motors. What are these most often used in?


texts: Avalanche diode circuit analysis of the current load

texts:
I have no idea how to work out this past exam question.

I'm kinda sure is that the diode is an Avalanche diode, but I'm not even sure how Zener diodes or this work.
All I think I know is that with a reverse bias voltage they wont break down? And they let some current pass through.

First I thought the IL would be zero, and also because of the voltage follower, Op Amps don't let any current flow through right?

I also tried to calculate total current and I don't know how with a diode in the circuit.

Any help would be greatly appreciated.

My calculations


texts: Serial connection between Raspberry Pi and Roomba

texts:
I have a Raspberry Pi with this FTDI cable and a Roomba 560. The Roomba has an SCI port to allow for control of the roomba via serial. I installed the PySerial library on the pi and send valid commands to Roomba, but the roomba doesn't respond. I have the TXD of the cable attached to the TXD of the roomba, the RXD on the cable wired to the RXD on the roomba, and a ground on the cable wired to the ground on the roomba (everything in  it's respective port). I do not have power going from the cable to the roomba or vice-versa.

What I can't figure out is why the commands aren't working. There's no error message upon running the python code. This is the information sheet for the Roomba's SCI port.

Code:

import serial

ser = serial.Serial('/dev/ttyUSB0')
# this is the defualt Roomba baud rate
ser.baudrate = 57600

# Start SCI - puts into safe mode
ser.write(chr(128))
# Enable full mode
ser.write(chr(131))
# Spot clean
ser.write(chr(134))

print 'Done'


texts: What happen to electricity when you turn off the lights

texts:
Sorry if this is the wrong place, but hopefully someone here can help me

OK so the way I have been taught is that turning off the lights doesn't really actually save electricity due to the fact that all electricity is is electric fields pushing electrons. So when you shut off a light and stop the electron flow, the electric field is still there.  So to my understanding the only real way to save electricity is to save it in a battery of some sort. Otherwise it just dissipates in the wires? Can someone pleas confirm or deny this. All that happens when I try and google it is I get a bunch of "10 awesome power saving tips" that don't really help me at all

Again sorry if this is the wrong place. Hopefully this won't take up much of anyone's time.


texts: How to measure dynamic power consumption of each component of a Microcontroller?

texts:
I am interested to get the dynamic power consumption of each of the component of a micro-controller. Can I do it by adding the power lines in place and route (PAR)? The purpose of it to get the more precised power consumption of a MC. In simulation I can do it by several means, but what would be the effect of adding power lines to the chip? More importantly, is it possible practically , i.e measuring power of each component through power lines? What will be the power network distribution? Vdd distribution, etc?
Thanks


texts: How can I build a simple USB signalling device?

texts:
I would like to construct a simple device that plugs into a USB port and sends the computer a signal (i.e just a 1) when a user presses the button or switch etc.

I imagine there must be some way to take a USB cable and modify the side that doesn't plug into the computer so that it sends a signal when activated, perhaps by tapping a battery or something.

My goal is to build a simple button that I can use to perform a regular series of actions with a simple press. I know they sell things like this but it would be cooler and perhaps cheaper if there was a DIY way.


texts: How much can I cut off an RFID card without breaking it?

texts: I have an RFID bus pass, and my phone case has an indent on the inside for a magnetic car mount plate. The indent is smaller than the bus pass card by around an inch on all sides. I'm wondering if I can safely cut some part of the plastic off my RFID card so it'll fit inside, but I'm not sure how to tell what's all inside. How would you go about doing this?


texts: I have a question that seems to baffle electricians that I've spoken to.  I'm running a 115V Fan off a TRIAC controller that utilizes a 0-10VDC control signal.  When I power the DC control signal down, the fan stops running as expected.  However, when I take voltage readings at the fan terminal box I get 120V readings from Line/Ground and 120V from Neutral/Ground but zero volts from Line/Neutral.  Can somebody explain this to me?


texts: Do resistors limit voltage, or reduce it?

texts:
I have been very confused with resistors because I have not found a great, although simple explanation about if resistors reduce or limit voltage.
Also, I want a explinaton on why you subtract Vf from V when finding the right resistor for a LED. I get that V=IR, but I don't get how to get the resistor value. I take (V-Vf)=I*R, that means that if I want to get 5v to 3.3v@25mA, I take 1.7=0.025*r, meaning that the resistor would REDUCE VOLTAGE by 1.7 volts, correct? Thanks!
*Feel free to make any comments and questions, this is quite vague.


texts:
My LED is running too fast while asleep, and it runs as expected when it's not asleep. Strange!! What is the problem here?

#include <avr/io.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>

volatile int8_t ss;

int main(void){

  DDRC = 1<<7;
  ASSR =  (1<<AS2);
  TCCR2B= (1<<CS21);  //  32768/8= 4096/256=16hz  1/16=62ms
  while ( ASSR & (0x1f) );
  TIMSK2=  (1<<TOIE2);
  sei();

  while (1){
    set_sleep_mode(SLEEP_MODE_PWR_SAVE);  // if this line removed, LED blinks at 1hz
    sleep_enable();
    sleep_cpu();
    sleep_disable();
  }
}

// 16hz
ISR(TIMER2_OVF_vect){
ss++;
if(ss==16) {
  PORTD^=(1<<7);
  ss=0;
}

}


texts: How can I design my FPGA power supply if I don't know how it will be used exactly?

texts: I'm designing a little dev board for FPGA experimentation using the Cyclone IV EP4CE10 but I am having a bit of trouble estimating the power requirements. I understand this depends almost completely on the usage and configuration of the device but since I'm a bit new to this and really have no idea how and what I'm going to be using it for, (because, you know, it's a dev board) I could use some advice on what would be "enough" for the different power rails. I won't be doing anything extreme, I believe, but I would like to have a bit of headroom for experimentation.


texts: Unclear common-mode voltage specs in the DMS-20LCD volt-panel-meter

texts:
I would like to buy a small digital volt-panel-meter. My eye fell on this series from Murata:

  DMS-20LCD (https://www.murata-ps.com/data/meters/20lcd.pdf)

This meter can be powerd by either a 5V supply or 9V battery.

The datasheet limits the Common Mode Voltage Range to +/-2V on the second page, but no further explanation is given.
Page 4 in the datasheet mentions the Common Mode Voltage again in the first application example:

When I see the picture, I would say:

Vcm = 2.5V
Vin- = 2.5V - 0.833V
Vin+ = 2.5V + 0.833V

Since Vcm = 2.5V, it is outside the +/-2V range. Why would Murata give an example which doesn't meet its own specs? I'm clearly missing something here.


texts: Transformer primary and secondary voltage phase shift

texts:
If we apply a voltage at the primary terminals of a transformer then for this we can get a voltage at the secondary. But they have 180 degree phase difference. What is the reason behind this??

I want to know why the phase difference between primary voltage and secondary voltage is 180 degree.


texts: Arduino robot wire follower + how to position on wire

texts:
I'm designing my lawn mower robot, and I am in the perimeter stage. The electronic part is done, and works quite good, now comes the software.

I have 2 sensors on the front of the robot, left and right, turned 45° with respect to the forward direction. They sense the signal emitted by the wire.

I need an advice on how to manage the approach of the robot to the line. I mean the stage right before it starts following the line..

It can approach the wire from any angle, so the signals are always different and I don't know how to move the robot in the right position in order to start the following...

What's the usual approach?

Thanks


texts: For a constant load, how does increasing supply voltage increase speed of the motor?

texts:
For a given load:

Increase in supply voltage results in increase in  armature drop. Increase in armature drop results in higher armature current. But we know that speed is inversely proportional to armature current.

We also know that increase in supply voltage increases speed. What am I missing here?

Edited to make the question clear as to what I'm asking


texts: Care to be taken while connecting 220 VAC to MCU pin

texts:
I have a product with a non isolated power supply which has 220 VAC live line as the GND reference:

My MCU receives 3.3 VDC from the same circuit.

I want to detect the presence of 220 VAC (same phase which powers up the device) using GPIO. (you might be wondering why bother because device will switch off if the 220 VAC is not present. However this is not the case. Phase is same but power line is connected directly to the 220 VAC live line and the GPIO sensing is required on a switch. When switch is closed, I will get 220 VAC, if switch is open, I will get nothing. This is what I intend to sense using GPIO.)

This is what I am planning to do:

There are two ways to do this:

1) Opto coupler way where I use an intermediate opto coupler to protect my GPIO as shown below:

2) Direct connection to GPIO as shown below:

I want to use the second circuit because of these reasons:

1) Cost is lower

2) Simplicity

3) First circuit is voltage dependent. If I am designing for 220 VAC and line voltage drops down to 110 VAC, the circuit won't work because optocoupler will not turn ON. If I design for 110 VAC and use it in 220 VAC, it will get damaged due to excessive heating/current.

My questions are as follows:

1) Since I am using non-isolated power supply circuit, does it even make sense to use opto couplers?

2) Since my GND is referenced to 220 VAC, do I need to bother about voltage spikes on phase line?

3) What protection should I put in place for my IO lines against voltage spikes (if it's a concern)?


texts: Clock generator with two inverters - how does it work?

texts:
I recently assembled a little electronics toy that flashes 10 LEDs one after the other. Unfortunately I do not understand why this circuit is able to provide a clock signal- it looks to me like the CLK line would always be high.
Two out of the three sections of the diagram make sense. The part that I do not understand is the clock generator at the top. Here's what I see:
The momentary switch charges C3 which then serves as "power source/time out" for the circuit. There are two inverters with what looks like a feedback line to the input. There's another inverter which eventually drives the clock. When C3 is charged there's going to be current through R4 and R1 towards the first inverter.
If the feedback line was connected to the third inverter I could see how this could be used for oscillation, but with an even number of inverters this looks more like a buffer.
However, since C3 is always going to be positive, how can the input to the inverters ever oscillate ? In other words how can the CLK line ever change ?
What is that R3/D1 line for ?


texts: Is programmable gain amplifier(PGA) in ADC enought to get me precision

texts:
I have 4 x 3wire load cells from a old weight scale connected as a full-bridge and I want to connect them in my uC ( Atmega328P, but not arduino ).

I want to measure weight under these specs:

Precision is the first most important spec
Error due to sensor is not important. I will change them in the future.
Measuring 0-200kg ( Each load cell is 50 kg so 4x50 = 200kg. Am I right? )
5g resolution ( calculated 16bit ADC = 3,052g )
I2C interface ( ADCs: LT2451, ADS1113 or similar )
Update: Load cells work at 3-6Volts

In most of similar ADCs IC there is a programmable gain amplifier capable of gaining up to 8 times. Some have external some internal Vref.

I would like guidance in these areas:

Vref source

Use 3.3 Volts from DC-DC converter?
Use uC Aref pin?
Use new IC voltage reference?

Best method for minimizing signal error

Use PGA provided by ADC?
Use instrumental amplifier?

I have no great expierience in ADCs but from my point of view I see it as using the smallest Vref source i can find that is also bigger than the bridge output( 200 milli Amps ) and having a opamp before the ADC with a fixed gain and not just putting PGA which is max 8 times.

I find it a little complicated task so I seek guidance in learning from the process...

simulate this circuit – Schematic created using CircuitLab

Update:

What I understood so far is that I get a 20bit or bigger ADC in order to minimize the error use Vref from a voltage reference dedicated IC and use no amplifier. If there is a better answer I will wait some days. Am I right? Feel free to edit this assumption if I made a mistake.

Update 2:

After some thought I do not like having 20bit ADC for error free signals. There must be a more professional way to do my math.


texts: Could you power a complete circuit using a Dc-Dc boost inverting IC?

texts:
I was making a circuit, and i was limited to using one Dc-Dc boost inverting IC, with a power supply of 3.8V.
I used the Dc-Dc to make -5V on its output, and (if i change the polarity of its output) i can use these 5V to power everything i needed, and i was fine until here.

The issue is, how can i have a common Ground point with my 3.8V power supply?

the reason i want a common GND point with my power supply, is that, if i use a POWER mosfet to control another circuit (led array for example), the voltage i send to the Gate of the Mosfet, cannot activate it.

Side note:(Also when i try to activate the gate of the mosfet, the voltage on the Microcontroller increases to 5.3V)


texts: atmega32u4 use Timer as souce for a counter

texts:
I started to play around with an atmega32u4 and came across a question I wasn't able to solve right now (may be I just missed the right page in the 500 pages datasheet).

I was able to create a routine that allows me to generate a configurable clock signal on PB5. Yeah! :D

Now I had the idea to use this clock as source for an counter to easy able to generate interrupts on a configurable amount of clock cycles for example on every 42nd.

As far as I figured out the use of counters I need to connect the T(0-1) pin to the clock source right?

Now my question is there a way to use the generated clock without the need of a wire between PB5 and the Tx pin?

Sadly there is no T pin for Timer3?
So I need to swap timer1 and timer3 to generating clock with timer3 and connect it to timer1's T pin?


texts:
I am reading the product page for TSMC's 20nm process. It states

  Compared to its 28nm node, the 20nm process provides 15% better performance and can reduce total power consumption by a third.

What exactly is meant by "performance" in this context? Which metric(s) is improved by 15%?


texts:
I signed up for a class on edX that involves microcontroller programming, and my kit arrived today so I wanted to start experimenting a bit, the only problem is, I have no clue how to connect the LaunchPad (TI Tiva C Series TM4C123GXL) to the breadboard. I was hoping to create a simple "traffic light" project, following Arduino Street Traffic Light - Breadboard Edition

The problem is that tutorial uses an Arduino. I see on the back of my LaunchPad there are several female headers marked PA#, PB#, PC#, PD#, PE#, PF#, 2 GNDs, RST, VBUS, and +3.3V.

I have a very (very) limited knowledge, so I know GND is ground and goes to the - column on the breadboard's voltage rail. Is there a difference which GND I connect? Do I need to connect the Reset, VBUS, or +3.3V pins? Are any of the P... pins similar to the digital out pins on the Arduino? I'm just trying to figure out which pins on the LaunchPad I need to connect to the breadboard.

I have extensive programming background, but hardware is a mythical beast to me, so if this should be obvious (or if what I was thinking is impossible) please forgive me.


texts: Asynchronous Active High SET & RESET D-FlipFlop

texts:
I have two pieces of modules as below, may I ask which one is the right verilog to represent an Asynchronous active high set/reset D-flip flop (Rising clock edge)? Are both of them logically equivalent?

Expected Truth Table for my D-flip Flop

reset  set     clk        q
  1     x       x         0
  0     1       x         1
  0     0   rise-edge     d1
  0     0       0         Qo (previous d1)

First Module dff_async_RS

module dff_async_RS(q, d1, clk, reset, set);
  input d1, clk, set, reset;
  output q;
  reg q_reg;
  always @ (posedge clk)
    begin
    if (reset)
      q_reg <= 1'b0;
    else if (set)
      q_reg <= 1'b1;
    else
      q_reg <= d1;
    end
  assign q = reset ? 1'b0 : (set ? 1'b1 : q_reg);
endmodule

Second Module dff_async

module dff_async(q, d1, clk, reset, set);
  input d1, clk, set, reset;
  output q;
  reg q;
  always @ (posedge clk or posedge set or posedge reset)
    begin
    if (reset)
      q <= 1'b0;
    else if (set)
      q <= 1'b1;
    else
      q <= d1;
    end
endmodule


texts: Is voltage and current sources linear or nonlinear?

texts:
From the circuit theory it is known that an element whose response is linear is called linear element such as resistor, capacitor. For example, in case of resistor the slope between V and I is a straight line, but I have some confusion what about current source or voltage source? Is it linear element or non-linear?

Also if we see the graph of its V-I we can see that it is also constant: straight vertical or horizontal line.


texts:
I'm planning to make a multi range voltmeter, ranging from 10,50,110,220,330,440,550, and 660. This is my first time making high-voltage things. Here is my current scheme

The input freq is 50hz. I'm using ADUM1401 as isolator.
Here is the question:

I'm pretty sure about the resistor (R6-R13) size, but not about the capacitor. Is the capacitor still needed to (maybe) minimize noise or else? Or perhaps I can remove it because the input freq. is constant (50hz), thus the capacitor (which I think act as a LPF) doesn't needed.
I've tested this circuit on 20Vac input, but I'm still in doubt to test it with high voltage input, because I think there are no safety components (such as fuse), while (correct me if I'm wrong) the isolator is just to kept the MCU boards safe. Is there any chance the op-amp blows up?
Before it's too late, is there anything that I should add or remove anything in this current scheme in order to avoid noise or voltage drops and get a proper measurement result?

Thanks in advance


texts:
I have a 2-layer PCB, where I'd like to connect the top and bottom layers of two pads with a trace.
However, when I try to connect one layer, the other layer simply disappears, as shown below, where I'm able to connect the bottom-layer trace, but not the top one without the bottom-layer trace disappearing.
Is there a way to allow redundant tracks to exist in EagleCAD like in KiCAD?

(Note: The reason for doing this is related to my fabrication process. Also, in my present situation, I'm forced to use EagleCAD.)


texts: Why won't the Xilinx block RAM in a Spartan-3E consistently return data in a single clock cycle?

texts:
I'm creating a design using Verilog on a Xilinx Spartan-3E (XC3S500E) that uses multiple dual-port block RAMs, all instantiated through Verilog primitives such as RAMB16_S18_S18. I am using one port for both reading and writing (using write-enable) and the second for only reading (by setting WEB to 0). Both ports share the same clock. The block RAM is set to 18-bit wide, but I am ignoring the parity data (that is, not using its output value, and always writing zeros to parity bits)

I am using Xilinx ISE 13.4 and synthesizing/implementing using the GUI workflow with default settings. (non-default settings such as aggressive timing optimization and/or physical synthesis did not have a difference in regard to this issue)

I have timing constraints made for my one and only clock net, and it is consistent with the actual clock signal being put in (the constraint is for 50MHz, there is a 50MHz clock on the dev board I am using, and the timing report states that the maximum frequency for my design is 64.7MHz. The clock runs through a clock mutliplexer used as a clock enable, before going to the entirety of my logic.

In my code, I have a state machine that has three states (transitioning on rising edge of the same 50MHz clock that the block RAM uses):

Write address to a register connected to the address inputs of ports A and B.
Read data, perform some logic operations on it, and write it to a reg[15:0] that is connected to DIA (data in A) on the block RAM (with the address not changing). Turn on write enable for port A.
Read some IO pins into unrelated registers. Turn off block RAM write enable.

This consistently succeeds in a behavioral simulation in ISim, and (although it had less testing than the simulator) consistently succeeds on port A. Port B has identical logic (simply bit-slicing for address, and the same configuration for SSR, SRVAL, INIT) but does not succeed in reading during this one clock cycle. By simply adding an extra state between 1 and 2 (thus giving a setup time of over one entire clock cycle for the address) the design works, although as a learner of FPGA development I would like to know why and how to avert it.

According to Xilinx datasheet DS312 and timing diagrams within, this should be an acceptable way of using the block RAM. There are setup and hold times given in that same datasheet, but the ISE tools should already be aware of them and apply them during timing analysis, if I'm not mistaken. Additionally, I've re-read the block RAM section of UG331 (Spartan-3 Generation User Guide) a few times and could not find any inconsistencies between the instructions and my use of the block RAM.

The timing report list of the slowest paths mysteriously does not list any paths going to the offending RAM port.

If someone could make a recommendation, that would be appreciated, as I've spent quite a while debugging this and fear that I might be making some beginners' mistake. If any additional info is needed, please let me know so I can provide it.


texts: LED glowing when the driver's ground is cut off

texts:
I made a simple circuit with a premade LED driver (Recom RCD-24-0.35), analog-dimmed by a MCP4921 DAC, which is controlled by a 3.3V microcontroller board. You can see the schematic below, Q1 is unrelated to the LED, but is used for switching an external device via common emitter amplifier and is connected to the same 24V source. Since the LED driver analog dimming input is inverted (full dimming is at 4.5V, the voltage divider below the dimming port ensures that 4.5V is the maximum), Q2 logic level FET was added to cut the ground off the driver until the microcontroller board boots up to prevent the LED glowing at full power until it does. S1 allows to turn the LED off manually by the same method.

Problem is, when S1 is disconnected or/and Q2 is off, the LED still gets ~1.2mA of current and visibly glows, even though the return path is supposed to be cut off. Another thing that might help is that the glowing intensifies when dimmed more (lower dimming voltage applied) and disappears if the controller board is not powered, so it must be related to the dimming part of the circuit.

Am I missing something obvious here? All ideas are appreciated.

EDIT: Shorting out Q1 removes the annoying glow and the device works as supposed to (besides not having external device control, that is), what could be causing this?


texts: Can someone help me identify this circuit symbol please?

texts: I'm trying to fix something and there is a component on the schematic that I don't recognize. Is this symbol supposed to represent a jumper?


texts: Is there any advantage in running a universal motor on DC power?

texts: Since a universal motor can run on AC or DC, is there any advantage of using DC over AC?  If so, what chracteristics of the motor improves, if any.  What about noise levels?


texts: Does PNP collector current influence base current?

texts:
I'm trying to understand the classic "ideal power diode" circuit. An example (taken from the Raspberry Pi) was in this question.

My question concerns the left-hand PNP transistor. The function of it's EB junction is clear, but why is the collector tied... anywhere? What purpose does the collector current serve? Why wouldn't it work just as well with that collector disconnected?

The collector on the right transistor is more straightforward - it's purpose is to draw the gate voltage high to turn the MOSFET off. But what about the left one?


texts: Spectrum Analyzer Mode -- TX Duty Cycle With Time Domain?

texts:
I have a basic Rigol spectrum analyzer that sweeps across a range of frequencies and displays the amplitude of the signal.

When we go to a testing lab, their expensive spectrum analyzer has a mode where you put in a fixed frequency and it measures the duty cycles of your signal in the time domain.

What is that time-domain / duty cycle reading called for spectrum analyzers?


texts:
I have a set of solid state contactors that I want to turn on and off with 24v PLC outputs.

That contactor takes 4.5 - 15V inputs ( Changing the relay to the 24v input model is not an option right now).  I need some help calculating the size of the series resistor that I should use, or some other method to reduce the 24V output to 4.5-15v.

DP4RSC60D20B - http://www.crydom.com/en/products/catalog/d_p4_r.pdf

Logic Supply Voltage Range [VDC]:       4.5-15
Minimum Logic Supply Current mA:   16
Maximum Logic Supply Current mA:   20
Minimum Control Input Current @ Min voltage [mA]: 0.20
Maximum Control Input Current @ Max voltage [mA]: 1.0


texts:
I need to wire the following three-axis axis accelerometer:

http://docs-europe.electrocomponents.com/webdocs/127c/0900766b8127c68c.pdf

Here when I click on ADXL335, the below link comes with some more information:
http://www.analog.com/en/mems-sensors/mems-inertial-sensors/adxl335/products/product.html

Here it says:
Single-supply operation 1.8 V to 3.6 V

I have 3 problems here:

1)  Is COM the common ground for Vs and X,Y,Z outputs?

2)  What is ST pin for? I couldn't figure out what it is used for?

3)  Should the power supply be constant? Can I use a battery? The reason I am asking these if I have 9V constant power supply and I use 3 resistors to make a voltage divider, would it be ok?

4)  How can I extend that 6-pin, 0.1 inch spaced header? Is there generic plug name?


texts: What's the purpose of this combination of capacitors and TVS diodes?

texts: In the schematic attached below, what's the purpose of C5 and C6 in conjunction with D7 and D8?


texts: Wiring a 24VAC Vacuum Pump to 220VAC Mains Supply - Need Help

texts:
perhaps you can help me understand what I need to do.

I have a MEDO VP0125-C001, 50/60Hz, 24VAC, 19/15W Vacuum Piston Pump, with a black wire and a white wire. For all intents and purposes it is new. It was bought on Ebay.
I have a CLEM 220VAC/24VAC 100W double outlet transformer. Its old, has a Bakelite Case and on testing puts out around 25VAC at each outlet.
I contacted Nitto-Kohki, the suppliers/distributors of this MEDO pump and have obtained the pump specs. They advised me, after consultation with Japan, that this pump has not been in circulation for some time and they have no further information or circuit suggestions for its operation.

Here is my conundrum: they have stipulated, that I need to connect, "in series to both leads of the pump" a Vishay GP30M Diode regardless of wether I power it directly from the mains or from the step down transformer - its that part that has me confused.

I eventually found the specs on the diode, rectifier in this case, part number and supplier based in Europe (I didn't fancy the 20 euro surcharge for shipping, customs, etc on 3 euros worth of parts.)

Can you please help me to understand what I need to do to move forward on making this pump operational?

Thank your for your wisdom and help,

Tsc Tempest
Hamburg, Germany.

Addendum:

Many thanks so far.

a) The transformer is a thing of beauty, I opened it up: wood spacers between the housing and the transformer, fuses on either side of the input and output coils, and no center tap.

b) The pump is a linear piston pump, http://www.nitto-kohki.eu/en/technology-en/operating-principles-en/linear-piston-pumps.html and after re-reading the information provided by the company I'm not sure if it requires full or half rectification. Their advice is somewhat conflicting. At one point, they say it needs a rectifier connected in series with both leads to connect it to 230V mains, in another its to connect the rectifier "...to both leads..." regardless if I use a transformer.

However, I think, with your help, I AM moving forward. Thanks.

Addendum (03.05.2014) Circuit Diagram

Addendum (07.05.2014) Advice from the MEDO Engineer on the above circuit...

For the pump to operate correctly it needs a half sine wave input, i.e. a single rectifier connected in series on the black wire will result in correct and safe operation. It seems that the pump needs to have the half cycle time in order to allow for the magnetic linear shuttle to move between draw and exhaust positions.

I am now clear on where I need to go on this, I hope that this will help someone else out in the future. Thanks for your help folks. Much appreciated.  :-D


texts: lcd 16x2 replacement and or interchangeability

texts:
I need to replace a 16x2 LCD on a salt chlorinator display.

I searched the part number (GX1602KP) but can't find it.

I see alot of 16x2 lcd displays which look similar - are these lcd's interchangeable ?


texts:
I was simulating a transient test on an SRAM cell, added a transient noise of 1-30MHZ frequency with 100 multiple simulations and calculated a VQ-QB graph(dots).

I want to be able to only plot the noise graph itself. Can anyone help me with that?

Thanks


texts:
I know LED stands for Light Emitting Diode; but why does this component need to be a diode to emit light?

My question assumes that the "leds" we see everywhere (for lighting, screens, etc) are actually diodes -- this assumption might be wrong.


texts: Toroid Core Selection for Audio Isolation Transformer

texts:
I am a newbie. I have attempted to make an isolation transformer with some toroid cores and it worked, but not well. I tried using a "wide band" toroid core and it seemed to have killed a lot of the lower frequencies.
FT37-43

What is a good toroid core to use for making an isolation transformer for audio? How do I choose the right size?

I have Left, Right, & Signal Ground with my unbalanced audio signal.

Am I right in looking/targeting for 2Hz-20kHz frequency range in the toroid cores?
If the toroid core specs doesn't state the frequency, how can I figure out what frequencies it works with?


texts: Send data from MCU to Embedded Linux CoM

texts:
I'm using an ATSAME70Q21 MCU to record 32 channels of analogue data (via SPI ADCs) and 32 channels of digital data (via GPIO). My embedded device has an iMX6-based CoM (Toradex Apalis), which runs Embedded Linux and provides an OpenGL GUI, touch interface, USB connectivity, etc. Before implementing the MCU approach, I was collecting the data from the Embedded Linux SoM directly, and saving it to a SQLite DB.

How can I save the data to the CoM SQLite DB directly from the MCU? Would an RPC approach be sensible? If not, would a socket-based TCP/IP approach be sensible? In terms of hardware, I'm leaning towards utilising a direct ethernet connection between the MCU and CoM, but could use UART instead if that's more appropriate. Assume the highest bitrate is 5Mbps.


texts: I'm an electronics hobbyist and I recently purchased a breadboard for prototyping. However, it seems that under it all there is simply a metal grid. If I were to run power through this, wouldn't the electricity just run through the grid and short?


texts:
Although I can understand the difference between programmed IO (PIO) and interrupt (INT) transfers, still there is something vague.

In PIO, the processor repeatedly checks READY pin to see if the device is ready. However, in interrupt mode, the processor checks the INT pin at the end of the instruction cycle.

My question is, in interrupt mode, the processor still has to repeatedly checks the INT pin. I know that in this mode, the external device send the interrupt signal, but how processor becomes aware of that interrupt? The processor has to repeatedly check the INT pin on every cycle (or instruction cycle). Doesn't it?

References:

{1} http://www.louiewong.com/archives/137

{2} https://www.quora.com/What-is-the-difference-between-programmed-driven-I-O-and-interrupt-driven-I-O-What-is-one-advantage-and-one-disadvantage-of-each

{3} http://homepage.cs.uiowa.edu/~ghosh/Chapter3.ppt


texts:
The internal reference of the MCU is 1.45 V. I am relying on this to measure ambient temperature ratio-metrically using NTC and a resistor. The MCU datasheet says that the internal voltage reference can vary from 1.38 to 1.5. I am assuming that for the given instant, If I sample the 3 V supply with the internal reference and immediately sample the NTC, the short term variation of the internal reference will not add errors in my measurements.

Question: Is my assumption right? Or, any other suggestions?
[datasheet of MCU:][1]

[1]: http://am.renesas.com/req/product_document_lineup_child.do?REGION_KEY=3&LAYER_KEY=85282&PDF_URL=http://documentation.renesas.com/doc/products/mpumcu/doc/rl78/r01uh0382ej0200_rl78l13.pdf&TKUPDATE=true&APNOTE=true&AUTHORFLG=  Temperature Measurement range: -10 to 40C


texts: I am a beginner to this Raspberry Pi board. I wanted to power my board using 5V adaptor. I am currently having phone charger whose output specifications are 5V, 0.7 to 1A. So can I use the same adaptor to power my board?


texts: Why do PCBs always have an even number of layers?

texts:
Looking at many online PCB fabs, when spec'ing out a board and uploading your gerbers, often you select how many Layers your board should have. Invariably, the options are always multiples of two.

Why is that expected? While if you have three layers, throwing a ground plane in isn't a big deal, but what is the reasoning behind always sticking to even numbers?


texts: Why is the line-to-ground voltage half of what it should be?

texts:
Our electric power provider delivers 240 V, 60 Hz split-phase power to residential buildings. I've been checking our three-prong receptacles and I normally get the following measurements:

line-to-line: 240 V

line-to-ground: 120 V

However, there are two receptacles which have a different line-to-ground reading: 60 V instead of the expected 120 V. For both, line-to-line is also 240 V; only the line-to-ground voltage is different.

What possible connection/grounding error could have caused this?


texts: freechargeontroller.org. Half Bridge Driver

texts:
I built a full prototype per the plans available. Yes it seems power is getting to the low side. I wired on ammeter to the low side. I'm running my special power supply on the high side so that i can keep the current down to a level readable by my 250ma ammeter. Pictures I am attaching:

What I am finding out right now is that when I plug in my 6V battery to the low side my 5A short stopper fuse is blown pretty much immediately. I'm doing this while the driver_test.ino is connected and running on Arduino. So at this point I can see that if I were to plug in my battery to the low side without a shortstop I think what will happen is that mosfet will melt down (6V @ 6A = mosfets max power dissipation).

So at this point I ask is this happening because its in the design or am I doing something that is causing this?

By the way I added to this design a 470KOhm resistor on M3 between gate and source. I knew this was going to happen and I tried to prevent it with that big resistor. It didn't work.

Thanks in advance for any more information. I really liked the design especially the current sensing IC.

For reference the schematic:


texts: How to detect and measure a step change in resistance

texts:
I replaced my car stereo with a Raspberry Pi 3 and the 7" touch screen. Everything's working nicely, but now I want to hook up the volume control buttons on the steering wheel to the Pi. The buttons work by changing the resistance across two wires in the stereo wiring harness. With no buttons pressed, the resistance is 10kΩ, volume up changes that to 300Ω, and volume down is 50Ω.

I have previously used an MCP3008 ADC to read resistance values with a Pi, however in that case I just polled the ADC as needed. In this case I think polling would take up too much CPU power for the sampling rate I need.

I have also previously used the Wiring Pi library to set up GPIO interrupts to detect rising and falling edges on voltage. My current plan is to use an interrupt to detect the change in voltage when I press a button, then use that to trigger a read from the ADC to get the precise resistance value.

My question is, is this a good way to do this, or is there something better?


texts:
I want to use a tuned ferrite antenna with my RTL-SDR. From what I understand at the point of resonance, only the real (resistive) impedance remains. This should be a few ohms for the resistance of the wire, capacitor and ferrite losses.

The input pins of the RTL-SDR are about 3300 ohms, how do I go about matching these two ?

I was thinking of a negative feedback amplifier, I've seen some examples of this online but it is generally used for broadband matching when there is no capacitor. Can this also be used for a tuned antenna ?

Here is an example of an amplifier used in this way, the rest of the circuit is irrelevant. I won't post a 1000 pictures but a google of "broadband magnetic antenna schematic" shows this is a recurring method.


texts: Why can't CMOS simply be made of n-type enhancement mode MOSFETs and n-type depletion mode MOSFETs?

texts:
According to my textbook, a CMOS must use both PMOS and NMOS transistors because a CMOS needs transistors that follow the positive logic system and transistors that don't follow the positive logic system. n-type enhancement mode MOSFETs do follow the positive logic system and n-type depletion mode MOSFETs don't follow the positive logic system, so why can't only NMOS transistors be used?

The positive logic system defines 0 (off) as low voltage and 1 (on) as high voltage.


texts:
I am reading though a product manual for an amplifier that I am working with. It says that if you view the motor Back-EMF while it is disconnected from the controller and spun in a clockwise direction you should see the following outputs:

can someone tell me why the phases are only 60 degrees apart? I thought for a balanced, 3-phase system (which these motors are) the phases were supposed to be 120 degrees apart:

does it have anything to do with the fact that they are referenced from the same phase? If so, could someone show me how this mathematically works out?


texts:
In this article a RF Amplifier Design is proposed.
It's written that (page 2):

In an RF transmission network, if the reflection
coefficient of a certain port is greater than 1,
positive feedback will be introduced which may
cause the amplifier unstable. In order to ensure
unconditional stability, the real part of the impedance of the signal source, the load, the amplifier
input, and the amplifier output, respectively, should
be greater than 0.

To understand it, I think I should firstly understand what is meant for stability.  Is it BIBO stability (Bounded Input Bounded Output) or does it mean that the amplifier starts oscillating?

The author speaks about load (or input) resistance and positive feedback. If the first one is negative, the last one occurs. Why? If the author refers to absolute negative resistance, it means that the latter changes its voltage proportionally to the current (like a positive resistor) but adds it to the input voltage (instead to subtract). I can't see what this has to do with positive feedback.

Positive feedback doesn't necessarily mean instability. It depends on the poles of the resulting transfer function. So, which is the point of this analysis?


texts: How to "translate" to C the assembly command mov

texts:
I'm not sure how to understand the assembly command mov. e.g. in the following section:

mov -4(%ebp),%eax # %eax=*(%ebp-4), so eax is geting the **value** that is stored in ebp-4

in general, whenever I do:

mov (mem_address), %reg # reg = *(mem_address), so the **value** inside the adress mem is stored in the register

but if I do:

mov %eax, -8(%ebp) # in C: ebp-8 = eax

so if I try to translate into C then, moving data from mem to reg is like reg=*mem but moving data from reg to mem is just mem=reg because the register stores the value and not the address to the value? did I get it right?

and one last thing, is a label an address or a value? e.g.

mov label, %eax # in C: eax = *label? just like regular address in memory?

thank you for your help!


texts:
We discussed BJT-transistors in the lecture and this circuit came up, the professor said that this circuit would act as some sort of amplifier for the transimitted signal between the two transistor but I dont understand how it works.

Later I discussed it in a training group and was told that the signal would bounce between the two transistors because of the capacitor, but this confused me even more.


texts: Can Atmega 32 development board be used to program atmega 8 as well?

texts: I wish to buy a development board thus wish to know if this is possible? I'm a beginner so which development I should use? Any suggestions are welcome.


texts: Best way to get components for a new electronics lab

texts: I recently joined a lab that is still in the process of getting set up.  Our approach to acquiring electrical components (e.g. resistors, caps, opamps, etc.) so far has been to just wait until we decide we need something, and then when we do need it we buy a bunch of that component, along with maybe some related components.  Unfortunately, I'm finding that this work flow leads to a lot of time spent waiting for parts to arrive.  So my (soft) question is: What's the best way to stock a new lab with (standard) electronics components?  Are there e.g. kits one can buy, or should I just go systematically through a vendor website and buy 20 of everything I could possibly need?  (Or perhaps the approach we are taking is best, and we should just suffer with it for a month or two until we are eventually all stocked up...)


texts:
I recently got a set of 20 breakout PCBs. I didn't realize that they came in one piece- that they had not been cut apart yet. However, there are grooves between each board that are cut into the material. The grooves extend about 1/3 of the thickness through on each side, leaving about 1/3 left of circuit board in the middle.

How do I break these circuit boards apart? Is a forceful slice from a box cutter appropriate? Can I snap them apart with my bare hands? Or should I use a saw or a bandsaw to cut them apart?


texts: Two power sources, common ground and noise

texts:
I'm having the following circuit:

Where TWL6030 is a DC-DC buck converter and INA219 is a high side current sensing circuit.

My problem is with the power sources,Vbat and Vs are two different (no common ground) power supplies and Vs is a cheap noisy power source.

Is there a problem of having the common ground between INA219 and TWL6030?

Is the noise of Vs going to influence the functioning of the buck converter?


texts: Finding the frequencies for a given phase difference between supply voltage and supply current

texts:
I am trying to solve a LCR related exercise, but I ran into a problem.

Here is the exercise task and information:

  An alternating current circuit is composed of a 50 Ω resistor, an ideal inductor with an inductance of 10 mH and 1 μF capacitor. Find out the frequencies of the AC for which a phase difference of \$\frac{π}{4}\$ is present between the supply current and the supply voltage.

So:
\$R=50\ Ω\$
\$L=10\ mH=10^{-2}\ H\$
\$C=1\ μF=10^{-6}\ F\$

I also know know the value of the resonant frequency if it helps.

simulate this circuit – Schematic created using CircuitLab

Since it is not specified which of the current and voltage leads, I've figured that there will be only two values, one below the resonant frequency when the entire circuit acts as a capacitor and the other bigger than the resonant frequency when the circuit works as an inductor.

simulate this circuit

simulate this circuit

For the first diagram:
 \$tan\ φ=\frac{X_L-X_C}{R}\$
\$tan\ \frac{π}{4} =\frac{X_L-X_C}{R}\$

\$\frac{X_L-X_C}{R}=1\$
φ is the angle between the voltage phasor and the current phasor. The phasor values are all peaks.

Something similar can be written for the second phasor diagram.

The problem is that if I continue solving the above equation I will be obliged to deal with a quadratic equation which makes me think I'm overcomplicating everything, given the numbers I have to use in order to calculate \$\Delta\$ and then find \$\omega_1\$ and \$\omega_2\$. I'm thinking that there is an easier way to solve the task.

How should I go about solving this exercise?


texts: Since there is a voltage drop occur across a resistor in series, what happens when there is also a capacitor in series?

texts:
I am trying to calculate the initial voltage across the capacitor. This textbook has used the Potential Divider formula to get the voltage across the 9ohm resistor (15V).

But I don't understand why the initial voltage across the capacitor is also 15V. Surely due to the 1ohm resistor in series with the source, there is a voltage drop across the 1ohm resistor, so there is less voltage stored in the capacitor.


texts: PD control (PID without I) - Homework help

texts:
I've been given a system -

    x" = bx′ + kx + ru

and I've been asked to rewrite it in the canonical form x' = AX + BU.
I've got --

   [x1' x2']' = [0 1 ; k b]' * [x1 x2]' + [0 r]* u(t)

by considering x = x1, and x2 = x1'.

I'm pretty sure this is correct, and describes a spring-mass-damper system.
However,

I've now been asked to give the PD negative feedback control law ufb(t) for a desired trajectory xd(t) in matrix form, which I have no clue as to how to proceed.

-------------- I know the theory of PID control. And I know PD control equation would be

xd(t) = kp [    (xd(t) - x(t))   +    Td (xd(t) - x(t))'  ]

However I am hitting a road block about solving this. I'd really appreciate constructive suggestions and pointers. Thanks.

(I don't know why the equation form doesn't work here unlike math stack exchange hence bolded them all)


texts: "Starter Kit for electronics" - What to buy?

texts:
I'm going to buy some things for back to the electronic world.

Starting with an Resistor Assorted Kit.
Need to buy some kits containing the most common capacitors and transistors... what to buy???

[I want to buy to create a lot of things that there is schematic on the web without having to buy new components]

Inward merge from duplicate question, now closed; Summary for reference:

Electronics for everyday inventor

... capacitors, trimmers, resistors, pots, diodes, transisters, leds and laser diodes, timers (like the 555), inductors, ICs and common microchips, LOTS of sensors (temperature, gasses, radiation, light, sound, motion etc) and sensor like pieces (like selenium chips), and a bunch of other things ... for the chaotic inventor.


texts: What happens to charge in a 3-capacitor loop when link between two capacitors is opened and closed?

texts: Initially, charge is shared between Source C1 and the two Co capacitors which make up Ctotal. Once charge is stabilized, the wire link is cut, forming a tiny capacitor Cm in series which is added to C total, reducing Ctotal to zero. What happens to the charges and voltages in the loop then, and also when the gap Cm is opened and closed repeatedly?


texts:
I'm going to use my Rasp as a GPS tracking and it should be running even if the car is off; however, I don't want run out the car battery.

To make it happens I added a battery controller (https://www.adafruit.com/products/1944) that receives power from the car DC "car battery" (only when the car is on) to charge the rasp battery and keep it running; nonetheless, when the vehicle is off the rasp uses the backup battery.

To avoid unexpected shut down when the battery is low I'm using a GPIO pin and the output  pin "Low battery" of the battery controller to halt the device; however, even if the device is off and the battery is low, the device will still receive sort of voltage (~4v) from the battery.

The issue is, when the car switches on, the raspberry doesn't turn on as the battery keeps supplying voltage to the raspberry, so I need a circuit that detects when the raspberry is off and the car is on to reset the device or at least disconnect and connect the power supply of the rasp and makes it turn on.

I'm not good at electronics, but I'm trying to develop the circuit below, please could someone help me to see if I'm going to the right direction?

I've built a circuit below that disconnect and connect the rasp power supply when the "GPIO 18" is 0 (it will be 1 when the raspberry is running) and the car is supplying voltage (consider the car voltage as 5v regulated for a while).

What I'm planning to do are:

The gate "AND" will charge the capacitors C1 and C2 when the raspberry is off (GPIO 18 = 0) and the capacitor C1 is empty. Once the capacitors are charged, the gate "AND" will be 0 as the C1 will make the NOR output 0 and consequently make the "AND" as 0. The C2 will momently open the relay and reset the rasp.

Capacitors:
A) C1 should discharge in ~2 mins, so it is going to allow the raspberry turn on and change the GPIO 18 to 1
B) C2 should discharge in 3 secs and let the relay open and close the circuit (reset the raspberry) .

Sorry but it is hard to explain and I'm not good at circuits.


texts: Using a diode to ensure current flows in only one direction, without causing a voltage drop

texts:
To power my microcontroller (ATmega8), I am using a ~5.4V voltage source. I want to ensure that I don't accidentally connect the voltage source in reverse, and figured a diode would be a nice way to accomplish this as from what I have learned so far, a diode allows current to flow in one direction, and blocks it in the other.

But what I also learned is that diodes create drops in voltage. I have a few of the typical diodes (1N4001, 1N4148, etc.), and would like to use them to achieve the aforementioned result without dropping the voltage as it would be too low to power the IC.

My question is, is there any way to do this with a diode? Or do I need some other component (if so, what would you recommend)?


texts:
I'm trying to make a generic STM32F103 board output a sawtooth wave on DAC channel 1 but I'm getting nothing. The code is very straightforward and I've endlessly studied the datasheet, Google, various examples and tutorials. I just can't see what I'm missing here.

The IRQ function is being called at about 44.1KHz, and PORTA:0 is toggling correctly, but PORTA:4 is just 0 volts.

Can anyone see a mistake in this?

Reference manual is here

Datasheet is here

#include "misc.h"

extern "C" void TIM2_IRQHandler()
{
    static int i, j;

    // clear timer2 irq status
    TIM2->SR = (uint16_t)~TIM_IT_Update;

    // heartbeat toggle PORTA:0 every 256th tick
    (&GPIOA->BSRR)[(++i >> 8) & 1] = 0x1;

    // set new DAC data every tick
    DAC_SetChannel1Data(DAC_Align_12b_R, ++j & 0xfff);
}

int main()
{
    // switch on some peripheral clocks
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);   // PORTA
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);    // TIMER2
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);     // DAC

    // set PORTA:0 to output
    GPIO_InitTypeDef a0;
    a0.GPIO_Pin = GPIO_Pin_0;
    a0.GPIO_Mode = GPIO_Mode_Out_PP;
    a0.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &a0);

    // set PORTA:4 to analog input (manual says to do this when using DAC Channel 1)
    GPIO_InitTypeDef a4;
    a4.GPIO_Pin = GPIO_Pin_4;
    a4.GPIO_Mode = GPIO_Mode_AIN;
    a0.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &a4);

    // setup DAC channel 1
    DAC_InitTypeDef dacInit;
    dacInit.DAC_Trigger = DAC_Trigger_None;                             // set instantly
    dacInit.DAC_WaveGeneration = DAC_WaveGeneration_None;               // raw data
    dacInit.DAC_OutputBuffer = DAC_OutputBuffer_Enable;                 // enable filter
    dacInit.DAC_LFSRUnmask_TriangleAmplitude = DAC_LFSRUnmask_Bits8_0;  // filter level
    DAC_Init(DAC_Channel_1, &dacInit);
    DAC_Cmd(DAC_Channel_1, ENABLE);

    // enable TIMER2 IRQs
    NVIC_InitTypeDef nvicInit;
    nvicInit.NVIC_IRQChannel = TIM2_IRQn;
    nvicInit.NVIC_IRQChannelPreemptionPriority = 0;
    nvicInit.NVIC_IRQChannelSubPriority = 1;
    nvicInit.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&nvicInit);

    // setup timer2 @ approx 44.1KHz
    TIM_TimeBaseInitTypeDef timerInit;
    timerInit.TIM_CounterMode = TIM_CounterMode_Up;     // set scale/period etc
    timerInit.TIM_Prescaler = 0;
    timerInit.TIM_Period = 36000000 / 44100 - 1;
    timerInit.TIM_ClockDivision = TIM_CKD_DIV1;
    timerInit.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &timerInit);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);          // switch on TIMER2 update IRQs

    TIM_Cmd(TIM2, ENABLE);                              // start TIMER2

    while(1)
    {
    }
}


texts: Using optoisolator and triac with mcu to switch light on/off--need low power alternative

texts:
I'm using the schematic below to control a lamp (light bulb) with a microcontroller and I'm running the mcu (and moc3010) off of AA batteries. I just realized the moc3010 has an LED in it that needs typically 15ma. I'm assuming this 15ma needs to be applied constantly if I want the lamp to be on for say 6 hours a day--this will drain the batteries very quickly.

I need a lower power alternative (in 10s of uA to be constantly drawn instead of 15ma) for this to work, is that possible? Or am I better off just splitting the lamp wires and tying the first two to an ac adapter for the mcu/moc3010 and the second two to the light bulb-triac part?


texts: Transient Voltage Protection of an automotive circuit

texts:
Im an electronics engineer student, and im doing a project where im designing a circuit which will be used in automotive applications. More specific it contains a PIC controller which has 16 digital/analog inputs. It also has 16 outputs which will control 24V devices. It also has CANbus to connect several of these devices together.
Im having a problem grasping what kind of Transient voltages the circuit might be exposed of. Since this circuit might be used as a data collector e.g.temperature sensor read or as a controller in which an operator can press buttons that control another unit through canbus, I imagine that there might be different Transient types I need to consider. Many TVS devices state conformity to IEC 61000 standards. My initial plan was to use a TVS array as close to the input connector terminal on pcb. But as Ive read further Im really uncertain whether I can use TVS arrays. Most of these arrays are meant for High speed data lines and not MCU GPIOs. The requirement of the input lines are 5V,4-20mA. The MCU can handle a maximum of 5.3V,25mA on each pin. But these TVS array are meant for very small currents(?). And Im also afraid that they might disturb ADC readout(?).

Example of ESD event I can think of: Operator steps out of vehicle and carries a charge. Does not discharge until he touches buttons on a controller which might be inside a plastic chassis.

Im not the one designing the button panel, but I should be able to provide recommendations which will protect the controller. Which makes me think whether I should recommend protection on each button instead?

Im using a Can transceiver which isolates the Bus side from the MCU side. Im also using a DC-DC converter to power the 5V devices which isolates up to 1500V which should be enough protection against power surges coming from the 24V battery on the truck?

If someone could help me down the right path I would be very grateful.

Ive tried to elaborate my problem as good as I can. Hope it is clear.


texts: Linear hall sensor to detect large fields with digital output?

texts:
For an application I need to measure magnetic fields in the range between -200mT to +200mT with sub-mT resolution. Additionally a microprocessor is available but I don't have a high resolution ADC and want to avoid sensing low voltages in a noisy laboratory environment if possible.

Are there Hall sensors available that have a serial, I2C or similar output with at least 12 bit resolution in the field range given above?

An additional caveat: this is a beginner's one-off project, so I want to avoid sensors that require an custom EEPROM programmer or other expensive items. In principle something like the TLE4998S from Infineon but without a custom protocol and $600 evaluation kit.


texts: What would cause this kind of amplitude interference on my ADC recording?

texts:
I am using a 12-bit 6.4Mhz ADC to record a sensor reading.

It's an ultrasound doppler system. A DAC is used to generate a TX frequency, that frequency is bounced off a moving target and received via an ultrasonic sensor.

In my testing environment, the amplitude of this reading is fairly consistent over time:

However, when the sensor is installed on site, I see this weird amplitude-modulation type interference:

I'm familiar with interference where additional frequencies are received/interfere with the recording, however I don't know what causes this, where the amplitude seems to drop out at points.

I'm not even sure what this is called, does it have a name?
and, more importantly, what would cause this behaviour?

More info:

More results with FFTs:

This isn't a display artefact. Zoomed in on one of the "zero crossings":

I even reproduced this in Matlab by mixing the adc data with a sinusoid of 200 Hz.

The top of each of the two FFT peaks has two separate frequency maxes instead of one.


texts: TRIAC dimmer, circuit design help (resistive load)

texts:
Okay guys, I've been tasked with making a light-dimming control system for a 240V heat lamp dissipating around 250W. I need to adjust the heat output on the lamp by control from a microprocessor.

I'm developing on an 8051-based SoC with RF circuitry and some sensors and actuators. Basically it's a node in a wireless sensor network. I've left all other components out.

I'm mostly a software guy, so I might need some help here. Pardon my lingo and if I raise fundamental questions, I don't have a lot of experience with this.

I am thinking of a design like this for the dimmer circuit:

.. and I have some questions :) I've marked red boxes with numbers matching the questions:

1)

Is this a sensible way to drive a triac ? The resistor on pin 6 should have a higher power rating. Like 5W or something I would guess.
The GPIO leg can supply up to 500mA, so it should be plenty to drive the gate for the transistor right?
And mostly any transistor will do I take it.

2)

I don't know how inductive the heat lamp is, or how its resistance changes with temperature. I want to do an estimate of how the triac should be spec'd.

240VAC(rms) would be ~340VAC(peak2peak), so 400V max isolation voltage should suffice, no?
A max surge-current rating of 4A would leave some overhead I would assume, but I'm not sure how much I need. I am assuming a switch-on from cold could draw a lot of current - should I instrument to be sure? I don't have any data on the heat lamp other than its rated for 250W max.

3)

Am I understanding correctly that this is the snubber?

I've found a couple of topics that helped me, but I'd appreciate a comment. I read these:

Trouble with triac driven dimmer circuit
Sanity-check on snubber design
Why Snub an Optoisolator?
Is a protection diode needed on a TRIAC optocoupler and what for?
How to use a phototriac coupler to trigger the main triac?
http://www.nxp.com/documents/application_note/AN_GOLDEN_RULES.pdf

TL;DR: Am I way off with the schematic? Some help on guestimating the rating of the components would be nice as well :)


texts: When driving a high-side MOSFET, we have the option of either bootstrapping or using a charge-pump. Assume that my operating frequency is very high. Which method I should go for to drive the high-side MOSFET?


texts:
I need to sample 8 power switches connected to 230 Volt supply. I want to record the status of these switch every 10 seconds and send to cloud for which I am using arduino with ethernet shield.

For example if status of switches is as below

On Off on On Off Off Off Off

then output should be a single byte 10110000.

I am a novice in electronic so bare with me if its quite straight forward.

As i want this circuit to be place in box for switch space is a concern.

Also my digital pins on Arduino are already used for other purposes.

One option which I was thinking was to use 8 differnt LM7805 to convert AC to dc from all switches and then use some D to A converter, and feed back this Analog signal to analog pin of Arduino from where I can convert that to byte and send to web.

Please guide if LM7805 will take 220V supply (home supply in India) and if not how that can be managed. Also I think using 8 LM7805 will take lot of space.


texts:
I'm relatively new to programming, Arduinos, and online forums in general. I would really appreciate an explanation for one of the basic tutorials for Arduinos:

I connected 8 LEDs to 8 pins (2 through 9) and programmed a short script to light the LEDs up successively, based on a schematic (found here): http://www.instructables.com/files/deriv/F45/G030/FVT7A09T/F45G030FVT7A09T.LARGE.jpg

A sample code suggests:

int ledPins[] = {2,3,4,5,6,7,8,9);

void setup(){
  for(int i = 0; i<8; i++){
    pinMode(ledPins[i], OUTPUT);
  }
}
void loop(){
  oneAfterAnotherNoLoop();
}
void oneAfterAnotherNoLoop(){
  digitalWrite(ledPins[0], HIGH);
  delay(10);
  digitalWrite(ledPins[0], LOW);
  delay(10);
  ...
}

However, I'm confused about the function of the setup() method! I'm told that the setup() method only runs once, so shouldn't the lights stop blinking after one iteration? Or is it a way to initialize ALL 8 pins continuously (and not successively)? Additionally, why is the setup() and oneAfterAnotherNoLoop() methods needed? I wrote everything into the loop() method:

void loop(){
  for(int i = 0; i<10; i++){
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], HIGH);
    delay(250);
    digitalWrite(ledPins[i], LOW);
    delay(250);
  }
}

And this ran pretty well, except after maybe 20 iterations, it just got stuck on the first LED light :(

Any feedback would be greatly appreciated! Thanks!


texts: Pin Layout Unknown - 5-way navigational switch

texts:
Completely at a loss, been searching for a datasheet or anything to help for a cou0ple hours... So I came to the only place where I can usually find help

Does anyone know what the pin layout of this 5-way navigational switch would be:

Here's the Link to where I purchased it: https://www.aliexpress.com/item/32815153642.html?spm=a2g0s.9042311.0.0.113f4c4dmzJuNZ
the only mark i see is letter D on the bottom right
Unfortunately my wife took out my battery from my multimeter, without using a screwdriver so I have none right now


texts:
I know cables are protected from short-circuit by using fuses / circuit breakers. Cables have I²t curves, which should be checked with fuses or cb's I²t curves in time / current chart.

Here I have chart printed from ABB's DOC. You can find MCB's and cables I²t curves.

Cable is protected from short-circuit from 0,01s. How cable is protected from 0s to 0,01s during short-circuit, since cbs / fuses can't work faster at 50Hz AC? In chart we can see there is an area where cable is not protected from short-circuit and in theory maximum short-circuit current can exceed cables I²t curve in that certain area (in this case it would be very likely).

How should cable be protected in these cases, where maximum short-circuit current is more than cable's I²t curve at < 0,01s?

UPDATE:

So in example above the cable is protected up to 3kA?

Some fuse charts confused me, because charts don't have horizontal line up to their short circuit current rating, in above example that horizontal line would continue until SCCR if it was higher (?)

I would like to further my question:

How fast does short circuit current reach its peak value?
Does it ever reach highest (calculated) value, since fuse disconnects the circuit before that?
Why breakers / fuses have short circuit current rating if circuit never reaches prospective short circuit current (of course there must be safety margin)?
I guess fuse disconnects the circuit before s/c current peak value, since the selectivity must be retained between multiple fuses. How long can be a distance between 2 fuses to retain selectivity (I guess this doesn't matter much, since electricity travels at speed of light)? Some manufacturers have selectivity charts for their fuses (mostly "must be at least two size bigger fuse").


texts:
I am trying to learn the features of IEEE rounding from the following source On fast IEEE Rounding

Can anyone one explain the equation for round up ? What does round up with fix up mean ? And what are floor and ceiling functions ? I tried IEEE 754 , but it does not mention these


texts: why do avr fuses need to be set when avr recognises crystal automatically

texts:
Today I had trouble getting my programmer to recognise my avr. The reason was because the sck period was incorrect for the internal oscillator. As soon as I fitted a crystal it worked fine.

I'm confused as to why do we bother setting the avr fuses for the crystals if it can recognise the crystal anyway.