texts: Why don’t most RISC ISAs write integer MULH/MUL or DIV/REM to two general-purpose registers?

texts:
Most hardware multiplication and division algorithms can compute the high and low words of a product of two integers, or both the quotient and remainder of the division of two integers, at the same time.  In major RISC ISAs, there are many different approaches to integer multiplication and division.  (In this post, I am only considering integer and not floating-point math.)

Most early RISC designs do not have such instructions at all.
MIPS I has multiply instructions that return the double-word result in a pair of special-purpose registers, $HI:$LO, as well as divide instructions that return the quotient in $LO and the remainder in $HI.  Moving the contents of either $HI or $LO into a general-purpose register is another instruction.
SPARC V8 and higher will store the low word of a multiplication or the quotient of a division into a specified register, but stores the high word of multiplication or the remainder of division in a special-purpose register, %y.
Most RISC architectures of the ’90s, including POWER, Alpha, and PA-RISC, have separate instructions to put either the high word or the low word of a multiplication in any general-purpose register, and to put a quotient in any general-purpose register, but not to compute a remainder at all; to get the remainder, you would calculate c = a/b, then find d = a - b × c.
The ARM A32 ISA does have two of the instructions I’m interested in, SMULL and UMULL, which were introduced in v3M.  These store the high and the low word of the product of two 32-bit integers in different 32-bit registers. It has many other variant multiplication instructions as well.  It does not, however, compute the remainder of a division.
ARM A64 redefines SMULL and UMULL to store the 64-bit product of two 32-bit integers in a 64-bit register.  It has no 64-bit multiply instruction, per se.  To multiply, you do a multiply-add that adds the zero register.  There is integer division, but no integer modulus.
The RISC-V ISA with the M extension has several variants of MULH, MUL, DIV and REM, but the RISC-V Instruction Set Manual recommends that when a MULH is followed by a MUL with the same source operands, or a DIV by a REM with the same source operands, microarchitectures can fuse these operations into a single operation instead of performing two separate ones.

It’s definitely possible to compute the full result of a multiplication, or division and remainder, at the same time.  Several RISC ISAs have one instruction to do so!  In theory, if you want only one result, you could set the destination of the other to the zero register.  Why, then, does no RISC ISA that I looked at have an instruction to store both the quotient and remainder in separate general-purpose registers, and why does the one ISA I found that does this for the high and low words of a product, ARM A32, drop it in the next major revision?

I am particularly interested in why the early RISC chips of the mid-’80s made this design choice.  SPARC V8 didn’t have an instruction format with two source and two destination registers and possibly didn’t want to complicate its decoder with another format.  MIPS I: cutting corners to fit more complex instructions into a classic RISC pipeline?

But I am also wondering why modern RISC architectures have moved away from it.  I’m guessing ARM A64 does it that way because fixed-precision multiply-add is useful for multimedia decoding, with less relative overhead the more bits you multiply, and, once you have that, it makes sense to reuse the circuits for multiplication (just add 0). But the RISC-V documentation suggests that the core should have a single operation that computes both results, so why not, in a RISC design, expose that in the ISA?

Have there been any published papers discussing this issue?  Or have the designers of these architectures ever explained their rationale for it?


texts: Can't for the life of me figure out voltage of batteries in series

texts:
Imagine a 1.5V battery.

Before the battery is connected to anything, is there any voltage on either end? That is, is there already a build up of negative charge on the anode? OR is it that when the battery is connected to a circuit electrons easily moved from the anode enters the conductor and push charges to the cathode creating a voltage difference escalating the process to a potential difference of 1.5V?

I assume the end already has a charge buildup creating an E-field but because of the material(e.g. air) it's too weak to displace the electrons.
As a conductor is connected the E-field in the conducting material is strong enough to Force the electrons through.

If there are 2 1.5V batteries and the anode of one is pressed against the cathode of the other why doesn't current flow? One end is positive and the other is negative and the ends are conducting?

If there are 2 1.5V batteries connected in SERIES and connected to a circuit the potential doubles. Now I can kind of understand why as the second cathode has an additional set of positive charges increasing the E-field. But then why do the two batteries even have to be connected, wouldn't it be enough for them to be close to each other and just connect the cathode of one to the anode of the other?

So then I assume there is no charge until the ends are connected to a conductor. But that leads back to question 2. The anode of one connected to the cathode of the other doesn't create a current?

What happens if the two batteries are not connected in SERIES but one cathode is connected to the others anode, is there a current but with still 1.5V potential? It shouldn't have to be a closed loop as electrons don't go round and round, just from lower potential to higher potential.

It's all very confusing for me.


texts: Why do manufacturers strongly discourage using X7R capacitors in AC signal and mains filtering applications?

texts:
Recently I've seen notes in datasheets from capacitor manufacturers Kemet and AVX that recommend designers not use X7R capacitors for applications in which they will be placed across mains or used for mains filtering. From AVX:

Capacitors with X7R dielectrics are not intended for applications across AC supply mains or AC line filtering with polarity reversal.

Q1) Why is this recommendation made? The datasheets don't go into detail, and I have not seen an app notes or white papers that adequately explain the issue.

Q2) Under what AC conditions is it ok to use X7R capacitors across AC signals? Is their suitability based on simply having a current-limited/high-impedance source?


texts: Wireless data transmission options for streaming video

texts:
I am in the initial stages of planning a project that involves the wireless transmission of data between either an Arduino or Raspberry Pi and a base computer/RPi.

Data transmitted includes the state of a number of different environmental sensors, which have low data bandwidth requirements, but ideally I'd also like to be able to transmit a good quality video stream (ideally 720p, but at least 480p).

I see that most of the XBees have a 250kbps limit, and recognise that this is under ideal circumstances and I suspect that actual data transmission rate will be less than this, say 200kbps? So I feel think that an XBee solution is not going to be able to keep up with the data transmitted.

Anyway, I was wondering what options I have for wireless data transfer mechanisms that would be capable of data streams better than 250kbps and with 50m+ range?

I've started to look at modules such as this, but am unsure what the expected range of such units are (see this other question that I recently posted) and so I'm just trying to get an idea of what my options are. Cheers!


texts: LED forward voltage - why does series resistor take excess voltage?

texts:
I am currently having a problem wrapping my head around a pretty simple problem.

I know in multiple sources when taking into account considerations and assumptions of powering an LED you can use it's forward voltage, minus this from the supply voltage, and you obtain the voltage dropped over your current limiting resistor and hence calculate the resistance value to limit the current to a required current level for the LED.

However I have been reading further and it is my understand that from the LED I-V curve and it's exponential behaviour that when standard supply voltages are applied across the LED it will cause a large current to flow and exceed it's (current) specifications and fail. Therefore why if you apply a voltage source below it's forward voltage it will work without a current limiting resistor. So far so good.

However when you put a resistor in series, the voltage across the LED drops to it's forward voltage level and from that you can calculate the resistance value for the current etc etc. I have seen multiple (internet/forum) sources that this works for voltage sources from 5-12V for typical ~2V LEDs.

Therefore my question is:
1. If there is an assumption, which I suspect there is, that allows for a series resistor to instantly allow the LED to be at forward voltage regardless of anything else. I.e. different values of supply voltage and resistors etc, without much variance? Is there a more accurate method to calculate the forward voltage by taking into account more variables, i.e. some sort of mathematical proof apart from assuming the forward voltage is now occuring?

Any help would be greatly appreciated! Hope you have a nice day!

Regards.


texts:
I'm trying to understand the double stub matching impedance using Smith Chart.
Here is the diagram for the double stub impedance:

The impedance on the right has to appear purely resistive.
So admittance \$Y_2=-jb'\$ and admittance \$Y_b=1+jb'\$
and the admittance at \$Y_1\$ is elected to be at \$3\lambda /8\$. Why is this distance chosen to be \$3\lambda /8\$?
And to get the impedance at this location isn't it enough that I rotate \$Y_b\$ by \$270^0\$, why do I have to rotate the whole circle by 270?


texts: VHDL - Can you produce an output corresponding to the input if the input changed in the same clock cycle?

texts: In VHDL, if we have a system where the output changes depending on a variable that changes with the input. Say the output has 2 modes and an input switches between them. In the same clock cycle, can we check whether the input has changed (check if a button is pressed), store current input state and produce an output corresponding the input in the same clock cycle (if the output was changed in the same clock cycle)?


texts: Solenoid Valve for Selecting Between 2 Outputs

texts:
I'm looking for a solenoid (like) valve which will have 1 flow input, and which depending on the applied signal, will switch between 1 of 2 flow outputs.

The electronic equivalent of what I'm looking for would be Single-Pole Double-Throw (SPDT) switch, but for gas (hot air) piping.

This valve would ideally be for 5mm tubing and I would control its actuation through an Arduino. If I can't do this directly, I can use some sort of power transistor or relay.

My question is: Does anyone know where I can find such a valve? Or even what such a valve might be called?

All my searches on ebay and google so far have not dug up what I'm looking for.


texts: Timed Relay Circuit Wiring and Calculating

texts:
I am trying to learn electronics and I have a simple circuit in which a button is pressed, a capacitor is charged, then triggers a relay. (With my limited knowledge) I am using a 4.7μf cap and a 470K ohm resistor to charge the capacitor. If I am not mistaken, the delay should be about 2.2 seconds. However, I don't see any delay.

Here is my Fritzing diagram:

Relay Info:

Coil Voltage = 5vdc
Input Voltage = 6vdc


texts: Using OpAmp to drive LEDs according to incoming signal

texts:
Following schematic was suggested for visualizing the frequency (which is variable) of an oscillator using two LEDs that light up alternatingly. It seems that the value of the resistor determines how much voltage is provided to the LEDs. I've never seen this circuit before and was wondering, is there no need for a current limiting resistor for these LEDs?

simulate this circuit – Schematic created using CircuitLab


texts: What happens when you slow charge a li-po?

texts:
Basically, what actually happens when you slow charge a li-po/li-ion battery? When I say slow, I mean C/50 or lower. Is there any place to get more detailed information regarding different (unusual) ways of charging batteries? I know you're supposed to do constant current then constant voltage, but is that just to minimise charging time, or does not doing that actually harm the battery?

I was looking at some chips like the LTC4070, and that seems to imply that charging them like that is ok? Also, what happens if you never really let it discharge, and basically keep it charged around 3.5V forever, sometimes drawing a few ma for a bit, sometimes charging a few ma for a bit?

Edit: Assuming you charge faster than the self discharge


texts: Why the current measured form the microcontroller(Stm64 Nucleo L433RC- LPSleep mode) differ from the current value written in the datasheet?

texts:
I am using STM32L433RC -p microcontroller for current measurement. The current in the microcontroller  is measured using X Nucleo LPM01A module.I was doing a current measurement for Low Power Mode (Low Power Sleep Mode).

The current value given in the datasheet is in the range of microampere but the value which i read form the microcontroller is in the the range of milliampere.

Actually I tried both ways, by configuring myself and also from the examples provided in the CubeMx Software. In both cases current measurement was in the range of milliampere.

Can anyone provide suggestions, what can be the possible reasons for the variation in current?


texts: Data rates for each user in ADSL with discrete multitone technique

texts:
I read about MODEM technology from Forouzan's 'Data Communications and Networking'. Under ADSL technology it was said- The modulation technique that has become standard for ADSL is called the discrete
multitone technique (DMT) which combines QAM and FDM. There is no set way
that the bandwidth of a system is divided. Each system can decide on its bandwidth
division. Typically, an available bandwidth of 1.104 MHz is divided into 256 channels.
Each channel uses a bandwidth of 4.312 kHz .
The practical downstream data rate was mentioned as 8 Mbps rather than the calculated 13.4 Mbps. When they say there are 256 channels, do each user (subsriber) get to use only one channel? In that case, each channel bandwidth is 4 kHz and baud rate is 15 bits/baud and data rate of each channel (and subsequently each user) is only 60 kbps. How does each user then avail a downstream rate of 8 Mbps?


texts: So I have this differential amplifier and I need to know what's the Av and the Zin seen from vin(t). And how would a current source replace RE while having the same current in IE?


texts:
I was given an unknown transformer that I need help with. It has three taps on one side and 5 taps on the other.
I was told that it was a 120 volt input transformer but when 120 volts is applied it trips the breaker in my building. I need help figuring out the input and output voltages.
I am new to all of this so please be patient.


texts: Will electrons be taken from a metal plate if a positive charge is applied to it?

texts:
If I have a single metal plate, a battery, and one wire. If I connect the wire to the positive on the battery to the metal plate, does that remove electrons from the metal plate?

I am attempting to understand capacitors better. I know what they do, and mostly what's going on at a lower level, but I lack fundamental knowledge. Do I understand this correct about the single, metal plate? No circuit here; no capacitor here (I think). Just a battery and positive via a wire touching a metal plate.

I could not draw just a metal plate, so I used a capacitor symbol.

I thinks this really answers it,
How does a capacitor block DC?

Same with the other way,


texts: What is the difference between an 230V/120V AC automatic voltage regulator and a step up / step down voltage transformer / converter?

texts:
There seem to be 2 kinds of devices to convert home mains AC power between 230V and 120V: some are named "automatic voltage regulator", and there are some labeled as voltage transformer or converter. Sometimes the same company makes both kinds, more or less at the same price and weight. Both seem to provide the same thing: both 230V and 120V outlets, regardless into which voltage they are plugged in (they have a switch to select which voltage you are plugging it in, or its automatic).

What are the technical differences between these, and which one should be used in which situation?


texts:
I need a bit of help. I have some Jtron RJ45 sockets (do a quick search, for a better picture), and they have LEDs integrated.
I want to connect these sockets to a PCB and get the internet in (added passive POE 24V), but I have no idea how to make the LEDs work (flickering if internet is connected and transferring data)!

Do I just connect them to RX and TX?
Is there any standard to do this?

Here is a very primitive scheme on how I plan to use this RJ45+LM2596 module:

The LEDs on the image are actually the LEDs integrated in RJ45.


texts: Why UART voltage level on ATMEGA64A-AU are different?

texts:
Coming from this question I tried to measure voltage on RX1 and TX1 on ATMEGA64A-AU (the second USART) the RX1 voltage is about 3 volt and TX1 is 5 volt(straight out of the chip) which I've provided for the chip and the module rx/tx voltage level is 5 volt. the USART0 both RX and RX voltage is 5 volt.
As of previous question, the problem is I can't send command to GSM module, I got confused the RX voltage which has a different voltage than the module shouldn't be working but it is vise versa.
Why this happens? Why USART1 has different voltages on this chip?


texts: What happens when the voltage drop does not equal voltage rise in a closed series circuit?

texts:
New to electronics. Can't get my head around so many basic things but the application of KVL is bugging me the most.

I want to know what happens when Kirchoff's voltage law is broken. If for example, I have a 6V battery and a 4V load in a closed circuit. What happens here? The 4V load will consume or result in a 4V voltage drop. There will be a 2V "spare" unused voltage remaining before the current hits the negative terminal of the battery. In this instance, KVL's law is broken (well, I know it can't be).

I think the right way would be to put a resistor with a 2V voltage drop before the current hits the 4V load? That way KVL is not broken.

Which brings me to my next point: how do I know how much voltage drop a certain resistor will cause? If I used a 10 ohm resistor as a load on a 30V power supply, it will draw 3 amp current. Would this resistor cause a 30V voltage drop? If so, would that mean if I put two 10 ohm resistors on the same circuit (instead of one), each resistor will cause a 15V voltage drop?


texts:
I’m wondering if I’m making the right approach when I’m trying to calculate the power consumed by the diode in the circuit.

Here is the problem:

So my approach is:

Power loss by diode
 $$V_f \times I_f$$
where

\$V_f\$ = Diode forward voltage drop.

\$I_f\$ = The current flowing through the diode.

So the first thing I did was to calculate the current

$$I = V/R = 5/1000 = 5 mA$$

And then I use
$$
V_f \times I_f= 2 \times 0.005 = 10 mW
$$

Is this correct?
I feel like there is more to the problem with the fact that it states ”red color light”. Should I check on a sheet or similar?


texts: Additional overvoltage protection after RBO 40-40 with Zener diode

texts:
I have an automotive application where I have this:

simulate this circuit – Schematic created using CircuitLab

Would the 20V 1W or 5W zener diode be enough together with a typical automotive fuse to protect the LCD drive in case there is a voltage spike. Fuse would be 2A as it should be enough for the normal operation of the driver and screen. The RBO40-40 clamps to 40V so there could be still some over voltage after it.

Edit: I have understood crowbar is useful for over voltage situations but in my case I am mostly worried about very short voltage spikes.


texts: How to remove Kapton polyimide film from Pyralux cupper sheet?

texts:
I want to etch Pyralux sheet and will follow this tutorial. The sheet I want to try is LF9120R and it is 1 oz of copper per square ft (or 305g/m^2). They describe the sheet as:

  copper-clad laminated composites are constructed of DuPont Kapton
  polyimide film with copper foil on one or both sides, bonded together
  with a  proprietary C-staged modified acrylic adhesive. All copper
  clad laminates are available with rolled, annealed copper or
  electro-deposited copper. In addition, both types are available with
  double-treated copper (nodules of electro-deposited copper on both
  sides of the copper foil). Double-treated copper, if used, eliminates
  surface preparation steps prior to resist or coverlay lamination.

After etching out the copper off, removing the vinyl from the sheet, I want to remove the Kapton polymide film as well. Any suggestions what I can use to remove it?

UPDATE
Yes, it is exactly what I want. I know it is going to be fragile, and will have no support.


texts: Use One Solar Panel to Charge Two Small, Identical Batteries

texts:
I purchased the following solar security light kit a few weeks ago:

Harbor Freight #69643

Mounted system, worked great.  FYI, the lamp uses a 6V, 900mAh, NiCd battery pack that is recharged with the included solar panel.  I'm presuming that the controller is integral to the lamp assy, but I could be wrong (i.e. said controller may be integrated into the solar panel assy).

Well, we had a hail storm last week that totally destroyed the solar panel.

I have verified that it is NOT possible to purchase the solar panel separately, so I am considering the following scheme:

Purchase another security light kit - same model as the original purchase.  I'd now have one solar panel assy and two lamp assy's.  Next, I'd attach the two lamp assy's to the solar panel assy using a dc power splitter cord.  Now, I'd have both lamp assy's wired in parallel.

My questions: Would this charge both batteries?  I'm presuming that a larger recharging current would be routed to the battery with the lowest open circuit voltage.  If the controller is mounted in the lamp, I'll have two controllers downstream of the cable split.  If the controller is mounted in the solar panel component, I'll have one controller upstream of the cable split.  Does it matter where the controller is mounted (see above)?


texts: Protecting diode bridge from higher current

texts:
I have designed a battery charger circuit. The circuit is simple AC to DC power supply circuit, it is composed of a 220 Volt to 16 Volt stepdown transformer, a diode bridge and a capacitor.

Now the problem is that whenever I connect the charger to the battery the battery starts taking high current up to 19 A and the diode bridge is burnt because the diode bridge can't withstand current higher than 10 A.

How can I limit the current to 10 A so that the current is kept in 10 A safe range for the diode bridge. Note that  I can't find a high current diode bridge in market here.


texts: Correcting non-linear response of 5050 RGBW LED strips

texts:
I'm a non-engineer asking this question. I'm using a so-called 5050 RGBW LED stips for a project. The level of each colour is controlled by a mosfet transistor (IRLZ34N) which is in turn modulated by values sent from GPIO pins of a computer. The values sent to the mosfets range between 0 (for off) to 255 (for the brightest value). I am using a computer program to control the LEDs and which has colour gradients that can be configured in time to produce transitions between specified colours. The output is in RGB values scaled to between 0 and 255. The problem is that the LEDs (I assume and not the mosfets) have a very non-linear response. For example the values of 1, 2 and 3 jump in brightness quite noticeably whereas in the higher ranges the differences in brightness are less apparent. Consequently the colours generated by the gradients are not well reproduced by the LEDs.
What I'd like to know is if there are any standard curves or formulas to make the response linear for these strips and if not, to ask how I might go about evaluating my own array of corrected values?
I have photographic light meters and a darkroom that might possibly be of use here. I have no technical details on my LED strips, but the model I am using is here:
https://produto.mercadolivre.com.br/MLB-1747103834-fita-led-rgbw-5050-rolo-300-leds-ip65-com-controle-5mt-_JM?searchVariation=71202900380#searchVariation=71202900380&position=5&type=item&tracking_id=a01e81a5-f325-4c6f-9cf3-4ce2780882ae
This strip also has "white" LEDs (the W in the RGBW) which I will likely use independently of the coloured ones.


texts: What is the charge-discharge watt hour (Wh) efficiency for lead acid batteries at different SoC and charge current 10-35A/100Ah C10?

texts:
There is a 1996 Sandia study with the title "A study of lead-acid battery efficiency near top-of-charge and the impact on PV system design" for charge and discharge lead-acid battery amp hour [Ah] efficiency at different states of charge (SoC) for a Trojan 30XHS low-antimony flood lead acid battery.
Current variation
However these results are measured using a charge current of only 3.3 amps per 100Ah of rated battery capacity. Real world PV/solar charge current are much more varying and at least have high peaks. That is one of the reasons why AGM is chosen, the ability to charge with up to 40 amps per 100Ah of rated capacity. Manufacturers for solar OPzS (flooded lead acid batteries) do allow charge current of 35 amps per 100Ah of rated C10 capacity.
Watt hour efficiency
There are battery manufacturers that even specify the Ah charge/discharge efficiency at different charging rates and different states of charge (page 21):

Due to the fact that charging voltage is higher then discharging voltage, the nett effective Wh power efficiency is always lower then the Ah efficiency. And that Wh-efficiency is the only (real world) efficiency statistic I am interested in.
The only numbers I could find are in this "Electrolyte mixing for VLA cells" document from Hoppecke at page 10, with 10 amps per 100Ah charge current  and from 50 to 106% SoC resulting in a watt hour [Wh] efficiency of 71.6%.
Is there any study know for flooded lead acid charge/discharge watt hour efficiencies at higher then 0.033C charge currents?


texts: Are special terminals required for connecting thermocouple wires to a PCB?

texts:
I'm currently trying to integrate a type K thermocouple into an electronics project. I intend on interfacing this thermocouple with the MAX31855 cold-junction compensated thermocouple-to-digital converter IC.

I am not an expert on thermocouples and the Seebeck effect, so I'm somewhat curious as to how I should actually land the thermocouple onto the PCB. Assume I'm using loose thermocouple wires.

Questions:

Can I use any type of terminal (say a simple through hole screw terminal) to land the wires onto the PCB? Or will these new junctions introduce errors?
Is the termination method dependent on the thermocouple type? E.g. use this terminal for type K, use this other terminal for type J, etc.


texts: Demultiplexor logic table simplification

texts:
I need to implement simple demux in HDL:

Demultiplexer logic would be:

  {a, b} = {in, 0} if sel == 0

  {a, b} = {0, in} if sel == 1

I've started from basic logic table and first of all I wrote all posible combinations of all pins and in result i got:

/**
*   in | sel | a | b
*   ----------------
*   0  |  0  | 0 | 0
*   1  |  0  | 0 | 0
*   0  |  1  | 0 | 0
*   1  |  1  | 0 | 0
*   0  |  0  | 1 | 0
*   1  |  0  | 1 | 0
*   0  |  1  | 1 | 0
*   1  |  1  | 1 | 0
*   0  |  0  | 0 | 1
*   1  |  0  | 0 | 1
*   0  |  1  | 0 | 1
*   1  |  1  | 0 | 1
*   0  |  0  | 1 | 1
*   1  |  0  | 1 | 1
*   0  |  1  | 1 | 1
*   1  |  1  | 1 | 1
*/

Working on gate with single output i would need to build logical expression where output is equal to 1.
Now I'm bit confused how to simplify this logic table even if I know how final result should look like:

/**
*   in | sel | a | b
*   -----------------
*   0  |  0  | 0 | 0
*   1  |  0  | 1 | 0
*   0  |  1  | 0 | 0
*   1  |  1  | 0 | 1
*/

It would be great to get an idea how it is simplified, thanks.


texts: Switch off power when 0v is sensed / Short to ground

texts:
I have already posted this question but I made a mess of the diagram so deleted it and am posting again, apologies to anyone to answered the original question.

I'm fairly new to electronics and am stuck at how to get a circuit working. I have 2 peripherals connected in the circuit, a smoke detector and a relay, both operates at 12v DC and are continuously energized (ie always powered on). When the smoke detector is triggered an internal switch is operated and the detectors output shorts to ground.

What I would like to do is when the smoke detector is triggered, use the output of the detector (which is a short a to ground) to turn the relay off (ie no current is flowing through the relay) and when the detector returns to normal operation (its internal switch is off and there is no short to ground from the output) the relay returns back to normal and be energized.

I have looked at NPN transistors but they need a positive supply to operate the transistor and my detector outputs a ground. I have also looked at PNP transistors however they operate the transistor with a ground signal. I am wanting the opposite effect, ie to switch off when a short to ground signal is output from the detector. I’ve included a diagram which should hopefully explain the circuit a bit better.

Thanks in advance for any help.

NOTE:

The detector also has a +12v output as a fail safe, if the detector is working properly it outputs +12v which is used to power the relay, and hence you know there isn't a fault with the detector as shown below:


texts: How to make your own ps/2 to usb convertor for old keyboards

texts:
I am quite aware you can get ready made off the shelf adaptors to connect old ps/2 keyboards to USB. But I am curious as how would one do it themselves? I have tried just rewiring an old keyboard to a USB cable as they both have 5V and ground and 2 data connections. Though USB has a differential DATA +- and ps/2 has a data and clock wire.

So after trying a basic rewiring it didn't work so there has to be some conversion going on but what? The puzzling thing is going from USB to PS/2 works but going the other way doesn't work. Why?

Edit: Ok so in some more research, I think I understand the why now. As USB devices need to be registered and be able to give data to the OS about what it is when requested by the OS. ie. report back a VID and HID code. Although all the 'scan codes' that the keyboard sends to the system should still work with modern systems. As this was based on the original IBM PS/2 (AT) keyboards and this protocol has been carried though to today.

Edit 2: More info found on the electrical interface needed here. It seems its a not that easy but doable task to create your interface with the use of a cheap microcontroller. The connection between the microcontroller and the ps/2 keyboard seems straight forward enough but then from the microcontroller to USB is another story...

Edit 3: After a bit more searching I discovered that Microchip released a Technical Brief with quite a complete guide on how to do exactly what I was after! Its TB055 and includes the source code for PIC uC.


texts: Using RJ10 connectors for other data than intended

texts:
I'm in the process of building a device for measuring various things, for instance humidity, temperature, soil moisture, etc.

Until now I've been using GX16 connectors to connect the sensors to the PCB. The GX16 connectors are a bit overkill for the purpose (3.3v , max 1A), they require a bit more soldering than I like and are a bit expensive.

I was wondering if there are any other 3pin / 4pin connectors that would be suitable for this purpose. I was thinking about using RJ10 connectors, since they are widely available, can be soldered directly onto the pcb and are relatively cheap. Now I know that these connectors are originally intended for telecommunication / phones, so it feels a bit "wrong" to use them for a different purpose.

Are there any other 4pin/3pin connectors available on the market that would be suitable for this purpose?

Currently I will just be using the device as a hobby project in my own house, but if I ever would want to bring the product to the market, would the misuse of the RJ10 connector be a issue?


texts: What's wrong with this RC Phase Shift Oscillator?

texts:
I am trying to design a phase shift oscillator, using a CE Amplifier. I have a Vc of approximately 12V, gain of approximately 250 I aim for an oscillation frequency of  60 Hz.

But whenever I start the simulation, no oscillations take place. Can anyone tell me what is wrong with the circuit?
When I convert into hardware it works perfectly, but not in simulation. I am using NI Multisim circuit design suite 14.


texts: Why can't I vary the speed of a dc motor with only a potentiometer?

texts: I made a simple circuit with a 9 volt battery, a dc motor, and a potentiometer. The positive of the battery is connected to one side of the potentiometer and the negative to the other. One side of the motor is connected to the negative battery side and the other side is connected to the middle pin of the potentiometer. When I turn it, the motor is either off or on. How come the speed doesn't change since I am varying the voltage? Why do I have to use a transistor in this case with an Arduino?


texts:
I apologize ahead of time for this elementary, and quite possibly poorly posed, question, but I am a coward and want to make sure that I am understanding everything correctly, and not blow four motors...

We have a hydronics heating system, and we are adding a fourth heating zone.  Each zone is controlled by a motorized zone valve (https://forwardthinking.honeywell.com/related_links/water/5000_series/install/95c_10932.pdf).

The (above) manual says that the motors have, as

Actuator Electrical Rating:
24Vac 60 Hz, 0.30 A Current Draw,
5 W, 7.2 VA maximum

[The label on the actual device says 0.32 A; in any case, I note that 0.3 X 24 = 7.2 above]

Now, these are on the 'secondary' side of a transformer; the relevant  portion of the transformer label says

40 VA
PRI 120 V
SEC 24 V

My practical question is:

Since
$$ 40 > 4 \times  7.2, $$
am I reading things correctly, and it is safe to add the fourth motor?

I also have an 'enquiring minds want to know' question:

Are the numbers above enough to know what is the power draw on the 120 Vac side, when no motors are running, and when the 4 motors are running?

Thank you very much...

Peter


texts:
I mada a circuit using a 433 Mhz transmitter (to transmit a byte stream, continuously for 20 sec, after which transmission stops). I then connected it to a 5V power supply and the transmitter did transmit the required data to the receiver, however I noticed during transmission I could not use my garage door remote to open the garage door (the garage door receiver runs at 403 Mhz). I do have my 433 Mhz transmitter about 4 m away from the garage door receiver. Why is this happening, and most importantly, what can I do the resolve this kind of interference.

I am using these RF chips as my transmitter (Left pic) and receiver (Right pic). Has anyone used these chips before, if so what problems did you encounter, if any


texts:
I have a TB6660 Stepper driver and I gave pulse from an Arduino board.
According to the TB6660 datasheet, drier should out a sine wave that created by using give square wave from Arduino.

But, when I connect the 2 channel oscilloscope to A+ and A- separately, it outputs only inverted square wave.

I used several Microstep modes. But, same result(only change the frequency)

Please describe the reason for that.


texts: Remove DC offset from differential output, rotary encoder

texts:
Op-amp in my circuit is accepting differential sinusoidal signal, that swings around 0 V with 1 Vpp. It is configured as a comparator - swings to upper rail when the signal is positive and swing to lower rail when negative, effectively converting sine to square. Square wave pulses are then counted by uC.

However, differential output from my incremental rotary encoder swings around 2.5V.

What is a good way to solve this problem? Note that there is one unused channel in an op-amp, but I am not sure if it can help.
Thank you


texts:
I'm studying the following circuit with a MOSFET

Now for analyzing this circuit, my book came out with various equations (which I totally understand and have no doubts about it).

Because the gate current is zero we have:

(1) $$V_G=V_{DD} \frac{R_2}{R_1+R_2}$$

Assuming the MOSFET is working on saturation we also have:

(2) $$I_D=k(V_{GS}-V_t)^2$$

And applying KVL:

(3) $$V_{GS}=V_G-R_SI_D$$

Substituting equation (3) on equation (2) we have:

(4) $$I_D=k(V_G-R_SI_D -V_t)^2$$

Now comes to the point I'm not understanding. To show us the dependence of the drain current over the threshold voltage, the book takes the derivative of the expression:

(5) $$\frac{dI_D}{dV_t}=\frac{d}{dV_t}k(V_G-R_SI_D -V_t)^2$$

and then it writes:

(6) $$\frac{dI_D}{dV_t}=\frac{-2\sqrt{kI_D}}{1+2R_S\sqrt{kI_D}}$$

How on earth did they go from equation (5) to equation (6) by taking the derivative? What kind of substitution are they making?


texts:
I know what a ws2812b chip does, but how does it work internally?
How can it control the led?
Is there a datasheet that goes into detail?


texts: What are my options for detecting the position of a small moving metal object?

texts:
This is an airgun pellet trap:

I fire small metal pellets at it (4.5mm = .177" in diameter) at up to 120 m/s = 390 fps.

What are my options for detecting the X / Y position at which it enters the target?

Does it make it easier if I only need to know the distance from the center? (the score)

Right now my pellets are lead-free, but not ferromagnetic (they don't stick to a magnet.) If I were to get ferromagnetic pellets, would I have more options? Some inductive or otherwise electromagnetic effect maybe?

Right now I can think of:

A camera mounted on a tripod, that would compare successive pictures and detect any differences on the target paper. Downsides: it would need decent computing power (at least a Raspberry Pi) and it would probably miss a pellet passing right through a hole carved by the previous pellet. It would also not work as well against the black bands.
Two laser or CCD scanners, such as repurposed barcode scanners, mounted along the target edges at 90° to each other. Downsides: the optics would have to be tweaked in the case of CCD; they would probably need a white reference background on the other side; and they would have to be very fast, because the pellets are moving very fast.

Any other ideas?

Can I use antennas mounted along the edge, to detect some kind of electromagnetic effect? What if produce an electromagnetic field? Would the metal pellet interact with it in any noticeable way? Would a ferromagnetic pellet do so?

Can I use two supersonic distance detectors, mounted at 90° to each other? Can they detect such a small object, traveling fast?


texts: Designing a current sense circuit to measure a wide range of resistances and noise considerations

texts:
I have an application in which I have to design a current sense circuit in order to measures the resistance of a load resistor that can have values between 200kohms and 60ohms. The input voltage of the resistor would be a single 200mV pulse (5us width, 50ns each rise/fall time) with which I have to measure the current (and hence determine the resistance) of the load. The current converted voltage pulse would then be put through a peak detector (which can accept inputs peak pulses between 1mV-3.8V, so ADC can only receive values in b/w this range) which stores the peak voltage for some time which is then sampled by an ADC(18-bit, 0-5V input, LSB:19uV).
Given 200mV, the current would vary between 1uA to 3.3mA. I would prefer at least a resolution of 1uA. So below is my current implementation. I am going for a low-side current measurement approach. It is a simple voltage divider circuit with a sense resistor of 330ohms and a non-inverting amplifier with a gain of 21 which gives me acceptable results. The opamp is an ultra-low input bias current opamp LTC6268

I am aware that the measurement resolution of resistance decreases when going from very low resistance values to very high values and the following slope of decrease is acceptable for me. Here, the resistance measurement resolution decreases from around 30mV/4ohm [a change of 4 ohms at the load gives a change of 30mV at output](from 60ohms) to around 6.92mV/100kohm (till 200kohms), and the output changes from 3.5537V (at 60ohm load) to 6.92mV (at 200kohm load).
Now before I convert this into a PCB, I have some questions:

Is this an acceptable approach to the problem? Does this circuit/approach have some obvious errors? (If required) What changes do I need to do in order to optimize this circuit?
Will the gain of 21 cause major issues (such as amplifying input noise and giving garbage output)? What type of considerations do I need to take when designing the PCB in order to have good input noise immunity for the above circuit?
Continuation of 2., at 200kohm the voltage divider circuit attenuates the 200mV to 329.433uV (which is then amplified by 21), so is this (329.433uV) too low of a voltage that can get easily disturbed by background noise no matter how good the PCB design is? or can this voltage be measured properly using the gain amplifier?
Would a Transimpedance Amplifier (with a feedback resistance of 1kohm) followed by a unity gain inverting amplifier be a better candidate when considering immunity to noise? Measurement resolution slope of the TIA decreases more drastically (compared to the above circuit, which is why I am not considering this yet but the slope is still acceptable) from around 210mV/4ohm (from 60ohms) to around 1mV/100kohm (till 200kohms) and the output changes from 3.33V (at 60ohm load) to 1mV (at 200kohm load)
Excluding the given circuits, is there a better way to achieve my goal?

Edit: For now, I am fine with the resolution reduction at high resistance values (in the worst case I would go with multi-shunt) but I am more worried about the noise that can cause problems with the attenuated signal(as mentioned in questions 2 and 3).


texts: Controlling the "amount" of regenerative braking (variable back torque?)

texts:
I have a question I have been wondering about for a while regarding regenerative braking on electric vehicles.

If my understanding of electrical motors is correct

In a perfect world with no friction or noise, the amount of power put into a motor should equal the amount of power that can then be taken from the motor. That is to say, if you accelerate to 60 mph in an electric vehicle, and then take your foot off the gas and come to a complete stop, the amount of power generated should be the same as the power spent (again assuming no loss in this perfect world).

Does this concept work the same with torque? Would the maximum amount of torque that a motor can output, be equal to the max amount of torque that the motor can generate?

If this is the case, how can electric vehicles brake "more" with regenerative braking? What is the electrical system that controls how much power is allowed to be generated by the motor?

I would imagine that taking your foot completely off the gas would be the maximum back torque and maximum regenerative braking (obviously putting negative charge through the motor to slow it down makes no sense for regenerative braking!). And yet, electric vehicles allow you to brake harder or softer, charging the battery more or less.

Any insight on this is greatly appreciated! This is a difficult question to word given my limited knowledge, please ask for clarification if I have not articulated enough.


texts:
I have this transistor and cannot find its reference/datasheet. I've tried some variations of the name but nothing showed up. I know it is not an unusual model because here where I live we only find most used types.

It is marked N 842 00-000, here is a picture of it:


texts: Is the voltage on the resistor always low when the zener diode is not in reverse operating region?

texts:
I´ve read that the zener diodes are used for voltage regulation, and the resistor in this circuit limits the current through the diode and drops the excess voltage when the diode is conducting.

Does that mean the voltage across R2 will be very close to 0 when the zener is not in breakdown region with the appropiate load, like in this picture??

If the load conected in parallel with the zener diode is more complex, like on this other circuit, will the combination of the resistor and zener diode behave the same way?


texts: Short-term data storage in between wake cycles

texts:
I've been working on making a gardening system using an Arduino or an ESP32. To conserve energy, I will have the MCU sleep for long periods of time (I was planning on using pin-change interrupts to wake it up). It would be very useful to log sunlight and soil moisture data over time, but without having to wake up the MCU every 10 minutes or so to log it. So, I thought about storing or accumulating this data in a temporary storage area until the MCU woke up and logged the data (probably on a webserver).

I was thinking about using a simple solution, like analog electricity meters in houses, but I'm not sure if this is feasible. EEPROM also seems like an option, but that might be overkill.

So, is there a good method of simple short term storage I could use to lengthen the amount of time between when the MCU needs to log the data? Thank you for your help.


texts: I have a 24 volt 6.5 amp power supply which I am using to power a stepper motor driver which is rated to 3.5 amps max. Will directly connecting the two cause a problem or will the motor driver only pull the required amps?


texts:
I initially designed a circuit that would take a 12V battery as its power supply and power up a comparator circuit that would turn on/off a 12V fan based on temperature. This 12V battery could have been anywhere between 11.58-14.4V due to dis/charge so I regulated it with an LM7812, no worries. Comparator circuit uses LM358, NTC thermistor and a BJT for turning fan on/off.

Now my requirements have changed: The circuit will be supplied from a 48V battery that will have a voltage range of 43.2-67.2V. The load is now 48V (x4 12V computer fans in series). I have no idea how to regulate the power supply that is this high. Everything I look at, e.g. LM2576HV only goes up to 63V and Vout possibility is only ~15V.

I'm thinking of powering the comparator circuit with a 9V battery so that I don't have to drastically change all my components.

My questions are:
1. Do you know of an IC that can take this kind of Vin (43.2-67.2V) to have a Vout of 48V? Is there a simple alternative solution to this?
2. Is the 9V to power the comparator circuit a good idea? Will have to adjust the resistors so the LM358 opamp can turn on/off at values I want and pretty sure it can be supplied by 9V.
3. With the increased supply and load, will my current BJT be able to handle the change. It's a BDX53C and the load will be 1.11A.

Thank you.


texts: Will a diode burn out gradually over time when exposed to high rated current surges frequently.  We use a fr607 diode for freewheeling. Which comes inside a relay box assembly for a inductive load which is completely closed. After some months we get reports of relay box failures. When we open we find the diodes burnt. We want to know whether diode burn out happens instantly or will it keep working and gradually burn out over time


texts: DC current source into capacitor - does capacitor voltage rise infinitely?

texts:
I would like to check my understanding.
Scenario 1 : Constant Current Source with no parallel resistance
Consider the following circuit,

I = C (dv/dt)
Since, I is constant, dv/dt should be a constant slope and capacitor voltage should continue to rise to infinity with this constant slope.
Scenario 2 : Constant Current Source with parallel resistance

In reality, the current source will have a parallel shunt resistance and as the capacitor voltage rises now due to the 1mA DC current source and through the resistor path, the voltage on the capacitor should not exceed 1.8V due to the voltage drop across the resistor? But won't the ideal current source still be driving 1mA into the capacitor and so the capacitor voltage should still be rising?


texts: N-MOSFET switching an H-bridge: problems with PWM

texts:
In this circuit an Arduino digital pin drives the Gate of a N-MOSFET. When the pin is HIGH, current can flow from the H-Bridge GND to board GND. When it's LOW, current can't flow. What I need is to switch the H-Bridge ON/OFF in order to stop its quiescent power.

Everything works fine except when I use PWM signals in the H-Bridge INPUT pins. In this case, when the MCU suddenly sets the Gate pin LOW, the motors still move a little bit or they make a noise just like they are receiving power but not enough to move.

The MCU is working at 16 MHz speed, and the PWM instruction used is analog.Write(pin, 180); (range values 0-255)
(*I name the instruction only to help calculate the switching frequency)

I'm quite sure I should have put a pull-down resistor in parallel from the Arduino digital pin to GND. In other words, pulling down the Gate to 0V. I tried to stick manually a through-hole resistor but it didn't solve the problem.

The N-MOSFET is: AOD2922


texts: Transistor to control 4 L298N motor drivers

texts:
I'm trying to control 4 L298N motor drivers from 1 pin.
The 4 motors obviously need to run at the same time and speed.
I was worried that splitting the IN1, IN2 and ENA signal among the four would draw too much current from this one pin. That's why I'm looking into using a 2N2222 NPN transistor to control the signals.
Am I correct, is this the way to go?
Below is the circuit I use. (Only for the ENA signal, I'd do the same for the IN1 and IN2 signal.)
Although, when the ENA is LOW, I can hear the motor making very silent sounds.
Thanks in advance!
t.


texts: How much do lithium polymer batteries expand in volume?

texts:
I'm designing a device with a small lithium polymer battery (4x12x30 mm, 120 mA-h).  Looks like this:

I've heard that there is a rule of thumb that the space left for the battery in a case should be around 10% larger (I suppose primarily in thickness) than the nominal dimensions to allow for expansion.  Extra 10% seems quite large.

Where does this rule of thumb come from?  Is there any official recommendation for how large a compartment to put lithium polymer cells in?
How much do these batteries expand and shrink in normal use?  For example during charging/discharging cycles, temperature cycles over normal temperature range (-20C to 60C), etc.
What happens if the battery is in a rigid compartment in the case of malfunction?  It's pretty common to have batteries "puff out" if they get shorted internally, but what happens if the battery is in a compartment that prevents expansion?  (Assume the compartment is strong enough to withstand the pressure build up)  Does the pressure/walls make the short worse, or better?


texts: Oscillating sense current in overcurrent protection

texts:
I'm stuck at overcurrent protection for SCT3160KL using UCC21732 (or UCC21750, trying to see differences in Desat and Overcurrent protection). This is my circuit

Waveforms

I see that there is a lot of oscillation in the sense current. I put an RC filter with minimum cutoff frequency = 10 times switching frequency (500 kHz), and keeping R53 within 100 ohms, It does not seem to work. What can I do further??
(I chose R54 (sense resistor) as 120 mOhms since the drain current maximum is 17 A).
EDIT 1:-
I changed V32 to two voltage sources in series so that it resembles a double pulse test. After reading DKNguyen's answer I changed my circuit a little. Here it is:-

Now I tried to change my RC filter values so that the phase lag between sense voltage and OC voltage is reduced. Here is the waveform:-

Originally I had kept L1 as 1 mH, but I understood that it was too big and changed it to 1 or 2 uH.
My problem is that the OC voltage is going above 800mV (the tripping voltage) when detecting overcurrent. How can I rectify this?
Also, supposing here in this waveform we assume OC trip voltage is correct, and so the FLT_N pin is going low. Then I wouldn't be able to see the other pulse right? I had given a gap of 100 microseconds between the 2 pulses, and I've simulated it for 120 microseconds.


texts: How to inflate/deflate to create artificial lungs

texts:
I'm trying to create lungs for a project I'm working on that can inflate and deflate. I'm quite new to EE and using the Arduino, so I don't have much experience to know what would be the best way to mimick lungs.

I saw this video and wanted to do something almost identical to create the lungs. (Weird video, I know.) Around 1:34 he shows how he created it. I did some searching to figure out how he did it, and I found something called "pneumatic actuated muscles". I'm not really sure how this is done though, I just saw what it looks like once it's done.

I'll be using a Lilypad Arduino to control the lungs since I'll be sewing it onto a shirt. That said, it would be great if the hardware to inflate/deflate the lungs could be light so as not to stretch the shirt when one is wearing it.

Suggestions? It could be a really small amount of air, too. I don't mind as long as it can slightly mimic a pair of lungs.


texts: why is my differential amps error related to load impedence?

texts:
So ive built up this circuit, as a simple current limiter. After making sure the output is null when the differential is 0, i get different errors depending on the load impedance even when the both loads have the same current flowing through them.

When i connect a 100 Ohm resistor to the output i get a 10mV error at 100mA so the Op Amp outputs 90mV. When i connect a 10 Ohm resistor to the output at 100mA the op amps output reads 80mV.

I have tried two different Opamps, the one on the schematic and a Lm741. I have tested them with both single and split supply but the error pattern still persists. What is happening?


texts: g/LSB meaning in accelerometer measurements

texts:
I am not sure about the phrase I found here:
https://www.engineersgarage.com/tutorials/adxl345-accelerometer-sensor-how-to-use/

Sensitivity – With the default resolution of 10-bit, the ADXL345 has
typical sensitivity of 3.9 mg/LSB for default measurement range (i.e.
+/- 2g), 7.8 mg/LSB for +/- 4g, 15.6 mg/LSB for +/- 8g and 31.2 mg/LSB for +/- 16g measurement range. This means that ADXL345 with default
10-bit resolution selected can detect minimum change of acceleration
of 3.822 cm/s2 (3.9 * 9.8/1000 * 100) for +/- 2g, 7.64 cm/s2 for +/-
4g, 15.28 cm/s2 for +/- 8g, and 30.57 cm/s2 for +/- 16g range.

I understand that the value i take from my registers is measured in LSB (least significant bit). So, the minimum i can take is 1 LSB (0x00000001). Which in case of +-2g is: 1 LSB * 3.9 mg/LSB = 3.9 mg = 0.0039 g = 0.0039* 9.8m/s2 = 0.03822 m/s2 = 3.822 cm/s2
Am i correct?
LSB i guess is the smallest value you can measure because its the first (the rightmost bit) of your register
How the 10bit resolution affect my readings?


texts: How to determine temperature grade for automotive electronic components?

texts:
When developing a new automotive electronic component, the component needs to be certified to withstand certain temperatures. There are several standards that list methods of testing, such as ISO 16750-4 and AEC-Q100. However, these standards list a number of 'grades' or 'temperature ranges', and it seems to be up to the reader of the standard to determine which grade applies.

In ISO 16750-3, which deals with mechanical loads, each requirement states the purpose, such as "These tests are applicable to equipment to be mounted directly on the engine" or "This test is applicable to devices under test intended for mounting on sprung masses". For temperature ranges, I can find no such guidance.

One might say that it is up to the customer to specify the required range, but how is the customer to know? Googling the problem doesn't help, as all web pages do mention 'extended ranges' such as -40°C to +125°C, but omit how they arrived at that number.

How do I determine what the temperature range should be for a new component to be developed?


texts: n bit shift register (Serial Out) in VHDL

texts:
I'm creating an n bit shift register. When the enable signal is high, I want the shift register to shift n times, irrespective of whether enable continues to be high or low.
I've put a for loop to shift n times inside a process. My code is given below.

I don't think the for loop is working, as the shifting is not restricted to n times.
Where am I going wrong?

library ieee;
use ieee.std_logic_1164.all;

entity SReg is

  generic (
     n  : integer := 4
    );

  port(
    clk:              in std_logic;
    reset:            in std_logic;
    enable:           in std_logic;    --enables shifting
    parallel_in:      in std_logic_vector(n-1 downto 0);
    s_in:             in std_logic;    --serial input
    s_out:            out std_logic   --serial output
    );
end SReg;

architecture behavioral of SReg is
  signal temp_reg: std_logic_vector(n-1 downto 0) := (Others => '0');
begin
  process (clk,reset)
  begin
    if (reset = '1') then
      temp_reg <= parallel_in;
    elsif (clk'event and clk='1') then
      if (enable ='1') then
        --shifting n number of bits
        for i in 0 to n-1 loop
          s_out <= temp_reg(0);
          temp_reg <= s_in & temp_reg(n-1 downto 1);
        end loop;
      end if;
    end if;
  end process;
end behavioral;


texts:
I am trying to come up with a circuit using logic gates to drive a seven segment display.

I have a circuit with a BCD output (A, B, C, D) and need to convert this so that when any one of nine buttons are pushed, they produce a number.

The circuit needs to display a 0 when nothing is pressed. However, when buttons 1 - 9 are presesed it needs to display 7, 4, 8, 0, 5, 6, 8, 8, 9, respectively.

I have produced truth tables and k-maps, which all seem to be correct. But, it does not seem to be working at all. I get random numbers and a couple of odd displays of random elements on the display (not numbers or letters).

If anyone can point me in the right direction, or give me some advice, I would be eternally grateful!


texts: Parallel Termination in a Transmission Line

texts:
Suppose we have a parallel termination like this on a high-speed trace:

If the line impedance \$ Z_o \$ and \$R \$ are matched, then there are no reflections from load to cause any ringing at the driver output or at the receiver input.
But if the source impedance \$R_s\$ of the driver doesn't match with the line impedance \$ Z_o \$, shouldn't there be reflections still at the driver output from the line? So isn't that impedance matching necessary as well?
I am asking this because, in serial termination scheme, we match the source impedance to the line impedance. But in parallel termination scheme, I just can't see this concept. So, does that mean we have to mix both the schemes to ensure signal integrity on a high-speed trace?


texts: Power supply fluctuations. Bypass capacitor needed?

texts:
I am powering up a 5V device using a 12v DC 1A SMPS power supply. The 12V supply is connected to the 5V device through a 7805 voltage regulator. The device draws about 30mA when idle, but when it transmits a signal it draws about 100mA to 115mA.

When the device is about to transmit the signal, the input voltage of the device drops below the minimum voltage required for the device to function (3V DC). This is caying the device to restart. I am guessing this is because the 12V power supply is unable to keep up with the sudden power requirement.

Do I need a bypass capacitor? If so what rating capacitor should I use and where do I place it (near the input of the 5Vdc device, near the output of the 12Vdc power supply, or at the input of the 7805 voltage regulator?)


texts: Help with a simple two bit Arithmatic Logic Unit?

texts:
I'm creating a 2-bit alu. It has 8 defined functions (the functions are defined by a 3bit code), AND XOR etc, and these functions act on two, 2-bit binary numbers and produce a 2-bit answer.

From what I have done so far, I have a decoder that decodes what the function is, and the output of that powers/activates the corresponding purpose of that function.

for example the function code '000' activates the XOR terminal on the decoder and the XOR box spits out its answer, likewise '001' activates the AND box.

The problem I'm having is, the outputs of the two functions XOR and AND have to go into LSB,MSB and carryOut to indicate the answer, however since the outputs are tied together it causes an error. And I can't have 3 separate LED's defined for each function. I must only use that 3 (LSB,MSB and carryOut).

So my question is how do I not tie the outputs of the AND and XOR and produce a result depending on which function is active?.

*note on the image*

a - LSB of binary number 1  {these are controlled by switches}

b - MSB of binary number 1

c - LSB of binary number 2

d - MSB of binary number 2

cin - carry in.

Also everything inside the boxes are made using the basic gates and not from simulated blocks.


texts:
I have tried searching multiple sites such as digikey, google, bing, even wikipedia for the data sheets of the following Items but can not find them
these components are from a seagate barracuda.

Diodes (Most likely TVS Diodes)

Capacitor (I think)


texts:
I would like to know what is the usual range of a color sensor ? Can it detect a light source from a few meters away ?

for example, if I want to use a color sensor to detect a particular LED 1 meter away, would a color sensor detect that ?

I hope someone might know an answer to this based on expertise. Thanks !


texts:
Can you please tell me how to find part number of the particular chip.

I was trying to find max232 chip locally, and I have been told that I need to provide NTE part number.    I searched google, but could not find proper part number for chip

Thank you


texts: Designing a deterministic-startup precise oscillator

texts:
The problem

I need to reliably generate a sequence of events based on a digital input trigger signal. With minimal jitter and a predictable deterministic delay.

2 to 5 events
The events will be from 10µs to 10ms apart. Better than 5% timing precision, preferably +-2us.
Jitter of <100ns
Jitter must be randomly distributed, no deterministic patterns
The trigger can be as fast as 50kHz or as slow as 0.1Hz
Digital configuration interface (via SPI)

Due to regulatory complexity this design will have to be as analog as possible, with perhaps some fixed (non-programmable) logic.

Possible solution path

The solution path that I currently envision is with purely analog monostable multivibrators driven by DACs that set the oscillator currents and some configuration logic. Being analog, any imperfections will be influenced by gaussian noise, thus solving the random distribution of jitter.

But this clearly presents some difficulties  due to the three decades of required timing adjustability. Which led me to this question.

The question

Is it possible to design a crystal (or similarly precise) oscillator that has a deterministic and predictable startup transient?

Clearly a crystal oscillator would considerably simplify timings, as it would make possible replacing the monostables with counters. However a fixed oscillator would make the jitter deterministic, as it will be determined by the beat frequency between the trigger source (a processor) and the oscillator. This will cause problems with the averaging of captured evoked signals.

A crystal oscillator that can be deterministically and repeatably started on demand would greatly simplify the problem.

The basic idea

The first idea that came to mind is something as simple as this circuit:

simulate this circuit – Schematic created using CircuitLab

However, crystal oscillators have rather chaotic and unpredictable startup transients that last a long time (which I would assume is due to slow mechanical effects). So this won't work.

Is there a way to achieve this?


texts: Questions about connecting a JTAG ARM 10-pin connector to a TM412x board

texts:
I have a TM4C12x board which I want to debug over JTAG. This board does not come with a pin header attached to the JTAG pins, so I need to solder it myself. I have a couple of questions about this:
Debug probe: I want to use the SEGGER tools (JLinkExe, JLinkGDBServer) so I'm going to buy a SEGGER JLink EDU mini plus an ARM-JTAG-20-10. My intention is to use an ARM 10-pin JTAG interface only, I want the adaptor just in case.
Soldering and connecting: I'm following the TI guidelines about how to connect the JTAG interface. However, it's not clear to me what to do with the RST_N pin, let me explain:
This is a schematics about how to perform the connections:

However, below this schematics I find this:

In the schematics, there is no connection from EXTDBG to GND and the RST_N pin is connected to the ARM JTAG interface. In addition, there are several resistors.
On the other hand, the steps in the second image don't mention anything about resistors, however the do mentiong that EXTDBG must be connected to GND. In addition, it mentions that RST_N must be connected to the RESET on the debug probe, however the RESET pin on the board (which I'm assuming is RST_N, see more details below) is not wired in the picture.
Questions:

Then, do I need to connect the resistors in the schematics myself?
It seems that connecting the RST_N pin is required even though the guide doesn't mention it, correct? I need to be able to reset the MCU from gdb by executing monitor reset when ttached to JLinkGDBServer. I guess this pin is required to do this, right? (I mean, the RST_N pin probably resets the MCU)
In my board (TM4C123GXL), there are no pins called RST_N, there is a RESET pin near the JTAG ones though. Are these two pins the same one? (see below)

TM4C123GXL top view
The RESET pin I mentioned above is in the top right. Is it RST_N?

The full TI document is here


texts: How to wire the two AVcc pins on ATmega32u4 when only using some ADC pins

texts:
I am laying out a pcb with an  ATmega32U4, where I am using pins 26-30 as analog inputs. Pins 36-44 can also be used as analog inputs, but I'm using them for digital IO and JTAG. Both of these groups of pins have a nearby AVcc pin, which is used to power the analog part of the micro, and as a voltage reference for the ADC. The datasheet says that this pin should be separated from Vcc by a low pass filter, which makes sense, as that will reduce the ADC noise.  But there are two pins, so should I:

Use a low pass filter on each pin (adds parts where space is at a premium)
Use a single low pass filter and connect the two pins together (awkward, as they are on opposite corners).
Filter the one near the inputs I'm using and leave the other not connected.
Filter the one near the inputs I'm using and connect the other to something else.
Filter the one I'm using with a LC filter, and the one I'm not using with an L only.  I've seen this on someone else's design, but I don't understand the logic behind it.

Now, it seems to me that if the two pins are connected internally, I would get good results from option 3.  But although most of the datasheet refers to AVcc in the singular, there is a caption on figure 24-10 which suggests I need to filter both pins. Though maybe only if both sets are in use?

Any suggestions?


texts:
I'm using a low-frequency RFID IC that handles a bunch of the low-level signal decoding, but I'm hoping to get more range out of it.  It has two TX pins (diagram below) that it describes as a "full bridge" to oscillate the antenna at 125 kHz, 10 Vpp (when supplied with 5 V).
Unfortunately, I'm not getting the range I want out of the antenna, and I was thinking that upping the voltage might help get some more power into the whole thing, thus increasing transmit range.  My questions are, then:

Can I use these two TX output pins to drive an H-bridge - or another full bridge?  (A provided schematic would be really appreciated)

Will increasing the voltage help with the transmission range?

If this approach won't work, how else might I increase the range?  A different IC?  Etc.

The specs I'm using for the antenna are:
22" diameter, 20 gauge wire. 50-150 wrappings are what I've tested, but I'm fine with going outside that range.  DCR is around 6-7 ohms, and the coil is spread about 3-5 inches producing inductance in the 10-50mH range (again, depending on the exact configuration).


texts: Where can the detailed requirements for EU Low Voltage Directive compliance be found?

texts:
I'm designing an appliance that probably has to comply with the European Low Voltage Directive.

I've been searching for a guide on how to design a product complying with this directive, but I haven't found any.

I've found this document: http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=OJ:JOL_2014_096_R_0357_01&from=EN , but it is very general in its stipulations and doesn't contain any technical details.

Searching the internet I've found blogs etc where people talk about how to crimp ground leads to comply with safety requirements, so I believe there actually are detailed technical recommendations somewhere.

But where?


texts:
I am a bit confused with dont care condition.
I understand that in a system they are the positions that they dont affect they output when they are either High or Low.
How about this,
F=A'.D'+B'.C'+A'.B.C'.D( ' represents inverse)
If I am given the above expression how can I chose which positions in the Karnaugh map are the dont care?


texts: Do I need to consider RF power splitters for signal <1kHz?

texts:
I need to tap a signal on a BNC cord to record it with a Labjack ADC.  The signal is very low frequency, as the FFT shows.  I was planning on using an RF power splitter to add a line to the Labjack.  Would an RF power splitter even be necessary for this application?

Also, I realized that the way I'd connect the labjack might negate whatever effect the splitter might have.  I would probably just strip the cable and run the core to the Labjack's leads.  That seems like it would throw the impedance of the whole line off making the RF splitter useless.  Should I be concerned about this method of capturing my signal?  Is there a better way to connect a BNC cable to a Labjack screw terminal block?


texts: What FD, FE and FF hex values of chars represent in UART communication? For some time my UART won't work, and always returning me those three?


texts: Modifying land patterns generated with IPC-7351B wizard

texts:
I generated a 4x4mm 0.45mm pitch QFN28 according to the Atmega328P datasheet:

However, the pads on the corners (1+28, 21+22, 14+15, 7+8) are too close to each other, less than 0.2mm apart (when datasheet says the pins are 0.4mm apart because of the chamfer).

The solution that comes to mind is to make the pads on the corner shorter, as I did with pads 1 and 28:

Which gives about 0.3mm clearance:

Is this the proper way to do it? If I just leave the pattern as generated I will most likely get DRC errors depending on the process I pick (0.15mm vs 0.2mm).

I know the assistant is just a tool and not set in stone, but I'd just like some informed answers about the proposed solution. (Or alternatives)

Update after answers:

Thanks to DerStrom8 for the App note. Here follows a comparison of IPC generated and Atmel/Microchip recommended patterns:

Left is Atmel/Microchip App note (~0.266mm), Right is IPC wizard from Altium (~1.77mm)


texts: What buttons are used in the Stream Deck

texts:
Can anyone help or point me in the directions of what butons are used in the Elgato Stream Deck?
The buttons seem to have an intergrated LCD screen, which can be altered by the user.

Searching for 'LCD buttons/key' or 'TFT buttons/key' didn't yield any results except for these ones:

However, these are a much lower resolution then the Stream Deck buttons seem to be.
Looking for the buttons, or if they are proprietary, the closest matching ones.
Edit:
The only option I could think of would be to have a button where you can insert a tiny LCD and wire that up.


texts: Using net ties for star ground in Altium

texts:
I have been experiencing issues with net ties on altium. I am trying to join my separated analog and digital grounds at a single point (star ground) and I tried creating a net tie component to act as a large joining trace for my GND plane and my separated ground polygons

The green arrows show where I am trying to add the ties. I have a few problems however:

I create them with smd pads, so there is no solder mask on them. I tried messing around with the tie's properties but no luck, I cannot add solder mask to cover the copper!

The clearance between the pads is also an issue. I technically need to short the 2 pads to make the rectangle net tie I want in my pcb library component, so Altium will tell me there is a collision between the 2 pads from different nets once I place it.

How may I correct these 2 issues?


texts:
I was advised to clean PCBs using petrol if alcohol is not available.
I have tested doing it. Petrol and isopropyl alcohol both work good on PCBs.
I have also tried with acetone but it makes white spots on PCB.
I just wanted to ask can I use petrol as a PCB cleaner as it is easily available,or will petrol have any adverse effects on PCBs?


texts: Can a Bluetooth wireless connection bridge a USB Host and USB device?

texts:
Now that Bluetooth modules are dirt cheap, I'm wondering if I could make a pair of wirelessly connected objects that would act as a "virtual USB cable".  One would have a pig tail with a USB Male plug (USB-host side), and the other would have a USB-device end on its pig tail.  The goal would be for them to be able to wirelessly act like a wired USB cable, but wireless.

Requirements are simple:
1)  Commodity hardware.  If the cheap Bluetooth modules, plus a cheap MCU or two can do it, it's fair game.  I can code and design circuits, but this project doesn't warrant me designing PCBs from scratch and coding protocols from scratch.
2)  Does NOT need to support high speeds or charging port or anything fancy.  If it can do USB 1.0 reliably, great.  Primary usage would be for either USB printers or programming  MCUs  (Arduino, Launchpad, etc.)  Neither of which need huge bandwidth.

If this is doable, what would the basic data chain look like? (Example:  Host-side would be a generic PC USB dongle (just needs to support _____ protocol), and it would communicate via Bluetooth Serial (or other protocol) to the client that would be a generic Bluetooth module hooked to a ATMega32u4 board configured to use _______ protocol on it's USB out.)

I could swear I've seen online projects of guys doing this, but now that I'm interested in attempting it, I can't seem to find a similar project online to get a basic idea of how it would be done.  If anyone knew of one, and had a link, I'd appreciate it.

Just as valid of an answer would be to point out why something like this won't work.  (Obviously, such devices aren't being sold on E-bay en-masse, so their could be a real answer why USB signals can't be bridged across a wireless link due to latency or some-such.)


texts:
as mentioned in the question i am trying to implement a 4 bit comparator. The purpose of the comparator is to check if the 4 bit that are fed are equal to the code combination that is stored in the registers.
EDIT:
Essentially what we have is a lock system.
There are 3 registers holding 4 bits each.
The user feeds 4 bits at a time, there is a multiplexer that checks if the first second or third register depending on the state of the FSM, that value must be checked, then the comparator must check if the inputted value is equal to the one stored in the register.
If someone has an idea please let me know.
Thanks,


texts: Detecting phase between square wave and sine wave signals

texts:
I have a circuit that has a digital square wave input (generated by PLD, 1.8Vp) and a sine wave output (0.5 - 3.5 Vp). Both signals have 100kHz frequency, however the phase is different.

What is a good way to detect the phase difference between these two signals? Phase detectors I've seen so far are for either all digital or all analog signals? Is there one for the mixed signals circuit like the one I have?

Update

Knowing the phase difference with 1 degree is sufficient for my application. The frequencies are always locked relative to each other and never change. The square wave drives the analog electronics and analogs produce the sine wave which has AM modulated signal in it. The amplitude of the signal is, however, very low compared to the amplitude of the carrier. Due to the production variability the analogs (include some hand-winded inductors) have high unit to unit variability of the phase, and I am trying come up with an auto-tuning method for the DSP that processes the output sine wave.


texts:
I designing PCB for SIM7600CE with space constraint.Here, I placing filter matching and the antenna section through 135 degree angle traces (GREEN MARKING).Is it Okay?Can I have any PCB guidelines?
GSM  frequency:EGSM 900MHz/DCS1800MHz
GNSS frequency: 1575.42±1.023MHz


texts:
I am putting together a design for a custom Electrical panel. The panel consists of mainly DC powered components (Sensors, Controllers). Components are to be mechanically positioned using a DIN rail.

Operating voltage of the DC circuit is 24V, and components in the circuit have maximum current ratings ranging from 1A to 3A

Adequate and proper protection is a major requirement in this project.
Digging around for circuit breakers, i realized that the more common AC circuit breakers out there (In my geographic location) are not recommended to be used in DC circuits.

Further digging also revealed that these DC Circuit breakers are about 2 to 3 times the cost of their AC counterparts which is bummer as this has affected my projected costing.

Alternatives i read about include the use of fuses. This has its advantages and disadvantages too.

My question is, in my scenario what is the industry recommended way of providing protection in DC circuits.


texts: How to calculate the value of load capacitor for designing an op amp for pipeline ADC?

texts:
I'm working on 12-bit 200 MS/s pipeline ADC design. this ADC has 5 stage. the structure of ADC is 2.5-2.5-2.5-2.5-4 bit. In the first step I want to design a fully differential folded cascode op amp for my first 2.5-bit stage and can not find any reference to calculate the load capacitor for op amp. This capacitor must show the load of next stage on designing op amp.
this figure show my ADC structure:


texts:
Anyone implemented synchro inside FPGA. I am stuck with theta/angle conversion. I am able to convert 3phase to 2 phase using Scott-T formula.  Any help is appreciated.

Thanks


texts:
In order to use my GLCD + Arduino as a display for LCD4Linux, using the LCD4Linux SimpleLCD Driver which sends out a subset of VT100 codes (CR and LF).

I have managed to isolate the VT100 codes from regular text using the following code:

// include the library code:
#include <glcd.h>

// include the Fonts

#include <fonts/allFonts.h>

void setup() {
  // Initialize the GLCD
  GLCD.Init();

  // Select the font for the default text area
  GLCD.SelectFont(System5x7);
  GLCD.ClearScreen();
  GLCD.println("Please wait:  "); // output using Print class
  GLCD.println("  System initializing"); // output using Print class

  // could also use gText string output routine
  // GLCD.Puts("Listening...\n");
  Serial.begin(9600);
}

void loop()
{
  char c;

  // when characters arrive over the serial port...
  if (Serial.available())
  {
    // read character from serial library buffer
    c = Serial.read();

    switch(c)
    {
    case 27:
      if(handleVT100Code())
      {
        GLCD.ClearScreen();
      }
      break;
    default:
      // display character on glcd
      GLCD.write(c); // use Print class for output
      break;
    }
  }
}

boolean handleVT100Code()
{
  char c;

  String vt100Code;

  while(Serial.available())
  {
    c = Serial.read();

    vt100Code.concat(c);
    if(c == 'H')
    {
      break;
    }
  }

  if(vt100Code != "")
  {
    return(true);
  }

}

So for now it should only clear the screen when a VT100 code is detected (nasty, but to test things out). What happens, however, is that the VT100 codes get printed out anyway, probably because GLCD.ClearScreen() takes up too much cpu time (?). When I don't use ClearScreen, but simple println the vt100Code variable (which I return from handleVT100Code()) the code gets printed (albeit with some false positives).

What would I have to do to make my program understand these two VT100 Codes (Carriage return and Line feed). I have done quite some searches for an out of the box implementation of a simple VT100 terminal, but there seem to be none. If there is some easier way of using the GLCD with LCD4Linux, you are more than welcome to tell me.


texts:
Please consider the following code:

for(;;)
{
 int i=0;
 TPM1C2VL  =~ (i<<1); // Channel Value(Lower)Register.
 TPM1C2VH +=TPM1C2VL;
}

ALTERED CODE

unsigned long duty[420] = {<from zero to 65535>}

for(i = 0; i != 420; i++ )
   {
  TPM1C2VL =~ duty[i];
  TPM1C2VH += TPM1C2VL;
}
for( ; i != 0; i-- )
{
  TPM1C2VL =~ duty[i];
  TPM1C2VH += TPM1C2VL;
}

After the alteration also, there is no effective change, as now the LED just blinks randomly

I just wanted to apply breathing effect on a LED. Just to test I wrote the code with basic intuition of how it is supposed to work, didnt expect it to work in one shot, but it does.

Now my question is, HOW TO REVERSE THIS EFFECT? i.e. Slowly the LED dies out to zero.
I am not able to induce a reversal of this effect. I am using PWM of MC9S08DZ60.
I have made the following settings:
Prescaler = 1.

Modulo Counter = 65535.

Period = 4.096ms.

Edge Aligned.

On Channel 1.

PWM:
Set OUtput on Compare.

Channel Duty = 4.095ms.


texts: Resistor value calculations for measure negative and positive voltages using Arduino ADC

texts:
In order to measure negative and positives voltages with Arduino I found this solution.

I need to understand how to calculate R1, R2 and R3 according to specifications below.
Specs are:
The impedance has to be < 10K according to arduino ADC specs.
VOutput min voltage 0v and max voltage 5v.
VMeasure voltage range goes from -25v to +25v
In the solution ground can be shared without problems.

I tried to simulate in LTspice after I chose some values, but I cannot get output values on a dc sweep.
It only gives me constant voltage in the output of R2 and R3.
Does anyone know the reason?


texts: Triac randomly triggers when there is noise in the supply

texts:
I am using BTA16-800CW (Snubberless version) to control AC appliances (LED lights) and it randomly turns on / flickers when I adjust the fan regulator in the same room (this may be creating some spikes in my mains).
I have already connected an MOV to my controller, however did not use snubber as the triac already have them inbuilt (http://www.st.com/en/thyristors-scr-and-ac-switches/standard-and-snubberless-triacs.html?querycriteria=productId=SC124)

The triac is driven by MOC3023 and it functions well otherwise.

Appreciate if you can guide me on any additional components required to avoid such random turn on.

Schematics

Edit
I suspect the MOC3023 causing the false trigger! Have anyone used other drivers for BTA16 (snubberless version) successfully without false triggers ?

Update on 18-May-2018
I have tried FOD4208 instead of MOC32023 and they did not stop the false trigger. Also if this is a duplicate question, then please help by giving the solution or the duplicate posts which has the solution.

Update on 26-June-2018
I tried another Triac with high dv/dt and the circuit works fine when the opto driver is removed (Keeping only the triac in the circuit). Also the tests shows that FOD4208 gives less false triggers than MOC3023 (FOD4208 seems to have high dv/dt).


texts:
One thing I do not understand in reading about doing Assembly with the Atmel AVR (or perhaps with Arduino platform) is the actual outputting to devices (like LEDS/motors) and such.
Most Assembly "tutorials" simply explain counting/numeric stuff with registers.

Can anyone explain how exactly you send an out signal to a motor or LED under AVR assembly?

I guess I dont exactly get what each "pin" does for the microcontroller, and which ones can send output signals. (to turn a motor or led)


texts: Trying to understand prescaling voltage for ADC with least error

texts:
I'm teaching myself EE while designing a 12V DC battery monitor. I'm using a pair of Hall-effect sensors to track charge & load current and looking for the best way to measure the voltage. [An ATmega32u4 will take successive reads with the ADC, compute a 1-second average, and pass that up over USB for logging and analysis.]

The issue of error with ADC really has me spooked. It is essential that I produce meaningful data. There's so many error sources—both in my circuit and in the ADC—that it feels like playing wack-a-mole in the dark. I'm reading lots about calibrating the ADC's reference, but the first step is to pick a method for scaling the input.

My voltage window is 10-15V, specifically a range from 10.5V to 14.4V (3.9V). I came up with two approaches that (hopefully) do what I want:

A 10V Zener diode on the inverting input of a differential op-amp. Rejecting 10V, my range becomes 0.5V to 4.4V (3.9V) and uses nearly the whole range of my ADC.
A 20k : 10k voltage divider. Scaled down 3x, my range becomes 3.5V to 4.8V (1.3V)

I wanted to prove to myself which method would render the best granularity. Since I can also obtain 12-bit accuracy by adding four reads and shifting the result, I compared four possibilities: (assuming ADC ref is 5.0V)

method 1, 0.5-4.4V @10-bit is 800 steps: 4.88mV/step [#3]
method 1, 0.5-4.4V @12-bit is 3606 steps: 1.22mV/step [#1]
method 2, 3.5-4.8V @10-bit is 266 steps: 14.65mV/step [#4]
method 2, 3.5-4.8V @12-bit is 1065 steps: 3.66mV/step [#2]

My question is, do my mV/step figures tell the whole story, or is there some kind of downside to #2 that I'm not seeing?


texts: Can a 485 network work if the DE (driver enable) pin of the transceiver is always on?

texts:
We are using a Beaglebone Black with the Osso Cape (https://github.com/nexlab/Osso) for comunicating with other equipment using a 485 connection and Modbus RTU.

The driver enable (DE) pin of the cape's DS485 chip is tied to the GPIO 2_24, while the RO and DI pins were tied to the UART1 RX and TX respectively.

We haven't write any code to act on the GPIO2_24 at all, other than a cape overlay that sets it as output and pin Mode GPIO.

We were troubleshooting some communication problems when we noticed something strange: Using an oscilloscope, we saw that the driver enable (DE) pin was always high, but somehow the Beaglebone was able to normally send requests and receive correctly responses from the other equipement.

Normally I would expect that the 485 comms only worked with the DE pin HIGH when transmitting and LOW when finished, to avoid driving the bus when other equipment respond.

In other capes we used, this was controlled using UART4 RTS, but I could not explain why it seems to work in this case.

Is there any explanation on why it works with the DE always on?

EDIT: The datasheet (http://www.ti.com/lit/ds/symlink/ds485.pdf) says:

  Due to the multipoint nature of the bus, contention between drivers may occur. This will not cause damage to the
  drivers since they feature short-circuit protection and also thermal shutdown protection. Thermal shutdown
  senses die temperature and puts the driver outputs into TRI-STATE if a fault condition occurs that causes
  excessive power dissipation which can elevate the junction temperature to +150°C.

Maybe the chip senses contention and goes to high-impedance state, then being able to receive the response from the other equipment?


texts:
I am working on a design which must drive an audio output into 600 ohm headphones (aviation headsets). Normally, I would just use an off-the-shelf class D amplifier but I can only find ICs designed to drive 4-8 ohm loads. This could still work with an audio transformer, but would require a 75:1 winding ratio. The highest ratio I can find is ~55:1.

Can someone recommend a different design approach?


texts: How to select value of resistor to dicharge a capacitor?

texts: How to set the value of bleeder resistor to dicharge 10kV capacitor, which has capacitance value of \$5\mu\$F?


texts: How does analog radar signals encode two dimensions?

texts:
I understand how (one of the) principle(s) of RADAR works: send a signal, record the received scattering copy off the target, and measure the elapsing time. You might need to consider Doppler effects, but let's not worry about this. But this signal only gives you a topography of a single point. How can an analog RADAR obtain a topography map (per pulse) that has finite 2D area?

I know the pulse spreads spherically as it propagates, and so is the scattering copy, but still the antenna will receive one signal -- how can it tell which is which?

EDIT: To be more specific: Suppose your radar is in an airplane and directed downwards. It sends a pulse. On ground, there are two objects -cars, for instance- separated by distance x, and each of diameter d. When the pulse reflects off the two cars and reach the RADAR, how is the x and y axis differentiated? I'd assume the antenna lump sums everything into one energy pulse, thus losing all spatial details. This should not be an issue, however, in case of one object only.


texts: Why do computers have only a few thousand instructions when they could have millions?

texts: Most computers contain only a couple thousand instructions, but the bit width(usually 64-bit) technically allows computers to have access to millions or even billions of instructions. Some could be extremely useful, like DIVIDE, EXPONENT or conditional operations. Plus, clock speeds are grinding to a halt, and quantum computing is a long way away. Why haven't they added extra instructions to microprocessors yet?


texts:
This question is based on another question submitted here: Is it possible to make illegal clones of an Intel Core i7?

More specifically, it's based around this quote:

  I've been led to believe it's something like a 60% yield (i.e. they produce 100 processors they only get 60 that actually work) and the rest have to be discarded.

I'm incredibly curious now. What's the usual yield like for AMD and Intel CPUs? Is this actually documented anywhere or is it something not often spoken about by either company? Are there any articles or external information AMD and Intel have released on the failure rate of the CPUs they produce?

Also, is there any documentation on exactly why AMD or Intel CPUs might fail during production? I understand today's CPUs are immensely complex beasts, but, given the environment they're manufactured in, is a 40% failure rate really that acceptable (assuming the poster's claim of a 40% failure rate is even accurate)?


texts:
I have got this old Casio fx-92B calculator I am not using any more. I opened it up and found this:

I am not an electrical engineer. Is there a possibility of tweaking this board to make it run custom code?


texts: Is my pin understanding correct on the 2N3904?

texts:
I have the following in my circuit:

Am I right in understanding that the pins top to bottom are:

1/Emitter
2/Base
3/Collector

where the top square pin is Emitter, middle pin with red trace is the Base and the bottom pin would be the collector?

The datasheet is here:
https://www.sparkfun.com/datasheets/Components/2N3904.pdf

Many thanks!


texts:
I am trying to incorporate a Buck-Boost DC-DC converter into my design using the LTC3534 and I cannot seem to get it working.

Below I will post images of the datasheet recommended design, my implementation and also my PCB design files (top and bottom layer) although it is pretty hard to read.

Testing the implemented design:

Input voltage = 4V;
Maximum current = 0.1A;
No load.

The result is that the device wants to draw as much current as it can (I have tested it up to 400mA and it is the same). The voltage supply drops to 2.3V because of the current limiting, the output goes to 1.33V. The feedback pin is at 0.4V. (which seems logical as (R1 / R1 + R2)*1.33V = 0.4V, but it should be 1V at an output of 3.3V).

Important things to note: PWM pin is directly hooked to Vin, R6 shorted and C22 removed.

I have prior tested the board without the output capacitor C22 mounted on the board. (I forgot to solder it) Could have this damaged the IC?

Lastly, is it possible that my inductor is saturating, as it is rated at 2.4A@100kHz and the circuit operates at 1MHz (In my opinion this does not matter as I used no load so the current through it is a minimum)? This is the inductor used.

I have also tried another board with no current limiting and it drew a lot of current until one of the pins connected to the inductor became shorted to ground and the IC became toast.

Datasheet recommended design:

My implementation:

PCB Top:

PCB Bottom:


texts:
Im electronic for beginner, I looked at different size of batteries, I am bit confused about volt and current in battery size,
AAA, A, C and D battery type has 1.5V and different currents,
I checked on internet and it said "more volt make more current", but battery has 1.5v stay same and more current because of battery physical size are different?
If there are two AAA batteries together that mean 1.5v x2 = 3V that make more current, but Battery D is single and bigger has 1.5v and it has more current.
I see most DC Adaptor has 12V with different amp, for example:
12V 1A, 12V 6A

Voltage stay same but more current that makes me confused, how does
it work?

I'm confused with "More Volt make more current" and "Same volt and
more current"?


texts: Can I use a transimpedance amplifier using current through a resistor?

texts:
I'm designing a lab exercise for 1st year circuits students.  They learn about current controlled voltage sources, but we never show them one.  I know that transimpedance amplifiers are used for this purpose, but I've only seen them used with devices that produce current, like a photodiode.

I'd like to have them choose a resistor and a voltage to generate a current through that resistor.  I want to tell them that the gain of the CCVS is X, and they are required to choose their resistor and voltage so that the output voltage of the CCVS is Y.

a) Can a transimpedance amplifier be used in this way?

b) If not, is there anything that can?


texts: How do I determine solar panel amperage?

texts:
Complete newbie here guys so please bear with my question.

I have bought 12W 6.6V solar panel that I will be using as phone charger. Beside that I have bought small USB solar controller which outputs 5V and max of 2A.

If I am understanding it right, 12W / 6.6V = 1.8 amps output by solar panel.

Now, this solar controller is limiting voltage to 5V, does that mean that I will get 12W / 5V = 2.4 amps that will get stabilized to 2A or 1.8A (solar panel - 12W / 6.6V).

Again, sorry for beginner question but I really don't know much about this, just starting to learn.

P.S. I am guessing I will get 1.8A because that is what panel outputs, but I just want to be sure.


texts: i want to charge two 25F Supercaps (in series) in two stages: while their total voltage is under 5v, i want to charge them slowly via a resistor R3 of around 100 Ohm. After they reach the desired Voltage (2.5v each) i want to bypass R3 with 1 Ohm, effectively shorting out R3. I thought i could use a Logic Level Mosfet (irlz34n) for that, creating the gate voltage (around 2.5V) with a Voltage divider (R1 and R2). However, this seems impossible. While the Vcc of 5v is present, the gate voltage is higher then the expected voltage for each Supercap (caused by the voltage dropped over R3). Only if i disconnect vcc, the circuit works as i intend... Is there any way to short out R3, when the caps have reached 5v? Thank you for your help.


texts: Is is feasible to build an audio recorder with SD card storage using ATmega 16 or 32?

texts:
Is is feasible to build an audio recorder with SD card storage using ATmega 16 or 32 running at say 16 MHz?

If yes, what would it need in components? I don't expect you to make a device for me, but a high level overview of needed parts would be welcome.

I'm thinking of using an electret microphone and use the integrated ADC to capture audio and then save the signal to a FAT formatted SD card in a popular sound format if possible but if needed I could make a custom format and convert the data once it reaches PC.

I know that I'd of course need a power supply, SD card reader, microphone, AVR itself, but would I need some sort of filter at microphone's input? I'm mostly targeting human speech and it appears that I need to mainly focus at frequencies from 60 Hz to 7 kHz. I also heard that most of useful data is below 3 kHz.

Also right now, I don't have the feel for amount of memory the device would need, so if ATmega 32 is overkill, which smaller AVR would fit? I hope to go for as low pin count as possible.


texts:
So I've been at this question for a few hours now and i can't seem to get the final answer for a). I know how to find the the resistance of a basic Wheatstone bridge, but i don't know how to find the resistance with the 7 and 8 ohms parallel to the 10 ohms.

hope i was clear and thanks.


texts: I have a bag of DAC7512N digital to analog converter from TI. They are still sealed in the original packing, however the caution notes denote "calculated shelf life in sealed bag: 24 months" and the sealed date on the packing dates back to 01/01/07. Now the question is the shelf life an absolute lifetime for the devices in other words after the 24 months are the component unusable? or does it mean that at this point further procedures must be applied to the component such as baking before they could be used in a circuit?