texts: Which suppresor device will be use for 2pole AC contactor 240v coil voltage in coil as well as contact side?

texts:
I need an AC contactor for a 1 hp motor. For the contactor safety I'm goint to use the suppression device on the both coil and contact side. Please suggest me which suppressor device will be use!

I have read all question and answer about suppressor for contactor from your forum, that was a good understandable.

Which would have a good suppresor nature for both side (contact & coil) like diodes, RC snubber or Varistor Coil Suppressor?
If Yes of these once (diodes, RC snubber or Varistor Coil Suppressor), please explain why?

My desired AC contactor details are given below:
Coil voltage :240v
Pole         :2
Contact type  :DPST

Any suggestions would be greatly appreciated?
Kindly clear and explain above question, share your suggestion.


texts: How does cache coherency and DMA work together?

texts:
I am currently reading about caches and how they are used in Computer Science. The explanation of how the cache is always up to date with the actual memory is understandable as long writing and reading can only be performed through the processor.
But modern architectures use DMA, which means data can be written to the memory, without being transported to the processor.
So how cache coherency is ensured, when the cached memory block is used through DMA in modern architectures?


texts: Polarised capacitor vs. unpolarised capacitor. Which to use when?

texts:
Polarised capacitor has polarity (+ and -). Is it also called electrolytic capacitor? (Question 1)
Unpolarised capacitor does not have polarity (there is no + and -). Unpolarised capacitor can be connected in any direction, but this is not so with polarised capacitor.
Under what circumstances should one use polarised capacitor and similarly unpolarised capacitor? (Question 2)


texts:
When observing SPI communication with an oscilloscope, I see that there is some time between 'words' sent over the network. Red signal is SPI clk, and the blue is MISO.

My question is: What exactly happens in this time? As can be seen in my case this lasts about 500 ns. Is this duration dependent on the frequency of the SPI clock or on the CPU frequency?

I know that the number of bits that can be sent without this 'interruption' is dependent on the microcontroller. I have found microcontollers with 8 bit and 16 bit mode of operation. Are there also some with 32 bit mode of operation?


texts:
I need default close button, but many smd-buttons is default open. How create mosfet-button? It is for LCD display backlight switch off. When button is pressed the output must be 0 volts or disconnected. When button is not pressed the output must be 3v.  I created an experimental circuit. It is working OK.

Many old notebooks contain NDS9435. I also added a capacitor parallel to the switch to avoid bouncing. I don't know capacitor value- smd do not have a signature.
I think that switch-off current I = 3/3000 = 1mA is not optimal.
What values of resistor is optimal for this circut?


texts: Building a skin resistance meter (not unlike Scientology type e-meter)

texts:
I am trying to build a scientology type e-meter which is based on a Wheatstone bridge with a quad opamp. It is designed to measure the electrical resistance of the skin of a person holding the electrodes (labelled PC) on the diagram. ( i.e. the changes in resistance unbalance the bridge ). It has 2 x pots for basic adjustment to set the needle in the centre of the meter dial.

My electronic experience and knowledge is very limited.
I got the schematic off the internet and have attempted a board layout and have built one from this.
It is not working properly as I am getting full power on the meter and no adjustment is working.

Perhaps someone who is interested could look over my plan to see if there are any gross errors in my interpretation of the schematic?
Any suggestions would be appreciated.

originally posted here: http://stephenbennington.comoj.com/meter

Thank you for your detailed response to my question. I will endeavour to add the information you are missing.
I cannot take any responsibility for the design - it is not mine but by a man called Ralph Hilton who has worked professionally on the original meters and has endeavoured to make improvements which he has built and tested and made publicly available.
The schematic drawing is his and the coloured drawing below is my attempt at a board plan.

I am just trying to build one with limited experience and  unfortunately he is not longer available for consultation.
Please don't be hard on me - I have no electronics training and I am learning as I go.

This is the original web page where I got the design from. It lists all the parts and has a VERY rough sketch of a board plan - perhaps this will explain more than I can:

http://www.cs.cmu.edu/~dst/E-Meter/Ralph_Hilton/bmeter.htm

The OpAmp suggested is a LM324. I have include the + and - inputs on my drawing as I understand is correct for this type.
I too was puzzled why there is only one shown for amp 3 on the schematic but there are three connections on the board plan - the output and minus to two of the pot terminals.
This is a grey area and maybe where the problem lies.

I look forward to your responses.


texts:
I need two serial ports for this Atmega328 Arduino project, but this processor has only one hardware UART.  The processor, hardware design, and programming environment are already set, and I cannot change the hardware or processor at all, so a software solution is required.

The included Arduino libraries provide a SoftwareSerial library which I have discovered is only half duplex - during the send routine, interrupts are disabled, which of course means that the interrupt driven receive routine is shut down.

Before I implement my own full-duplex library, I wanted to find out if others have found a simple solution for this, or if there are libraries out there that implement it correctly.


texts: LM13700: voltage controlled ampllifier on breadboard not working while OK in Multisim - whats wrong?

texts:
I've designed this Voltage Controlled Amplitude circuit and I've simulated it in Multisim.

When simulating I get a waveform like this:

The green waveform is the modulator signal and the red is the output of the circuit. This seems to work OK.

But building it on a breadboard, I get this on my oscilloscope:

The green signal is a square wave that is the input signal. This is modulated by a low frequency sine wave. The yellow signal is the output signal, that is obviously not the expected square waveform.

I can't find the error on the breadboard. Any advice on how to fix this?


texts: how to really secure a pcb when photo-developing it

texts:
I just wasted about $30 in trying to create a large PCB. I made two attempts of removing the photo-resist correctly from the exact same circuit image but failed.

In the first attempt, the board was slightly bigger than the container with developer solution (sodium hydroxide) and water. I did each side one half at a time. The attempt looked wonderful until I noticed that in the dead center, all the tracks were missing and mostly faded.

I then made one more attempt. This time, I emptied the old solution and measured one part of developer to 11 parts of water (even though the bottle indicated 10) and as I was developing, things appeared normal at first as the image slowly appeared (which is what I want). As I examined the board, I noticed the exact same spot had the tracks missing AGAIN!

So both attempts produced exactly the same results.

Normally I do boards smaller than 11cm, but this one contained 3 circuits on it and is 15cm by 12cm. I was trying to save myself time by doing multiple circuits on one board.

Now what I used to hold the board together is a picture frame with clips on all sides and nothing blocked the light from reaching any spot on the board.

for the light, I used a UV blacklight and (call me crazy) but in the past I had success with smaller boards when exposing them for one hour, so I gave these large boards an hour exposure as well.

When I think about it I'm guessing the glass from the picture frame wasn't able to hold the board down 100%. Maybe I need to put heavy glass on top of the glass I got to force it down, but then again, will the light shine through?

I also attempted to make things better by adjusting the position of the board every 20 minutes so light can reach all of the board. My homemade exposure unit contains only one 7 inch blacklight and the roof of the unit has an aluminum pie plate covering the top so light that shines to the top can bounce back down (am I stupid to move the board during exposure?)

Can someone suggest the best solution? I feel I only have two options.

buy multiple sheets of glass to force the picture frame glass down so that the artwork literally sticks to the PCB 100%

or

waste time, lose mega dollars and buy a professional exposure unit

or

be forced to break down my larger circuits and connect the smaller circuits together via wires.

but if someone else has a better idea on how I can make a PCB with the photographic method, I'd like to know.

The minimum track width I'm using is 0.25mm and I never had problems like this before with a 0.25mm track width, and in both tests, when I print my artwork out, I print two copies on transparency and line them up to get super dark black traces and the transparency image is what I expected to see on the board when its developed, not a patch on the board where it appears over-developed.


texts: Negative effects of using underrated chargers

texts:
I was wondering what the effects of using a lower rating power rated supply for device would be. For example using a 1.52A supply at 19V to power a device where the charger that comes with the device is 4.74A at 19V.
Is doing this likely to damage the device or will it just take longer to charge.


texts: Signal Flow Graph for electrical circuits

texts:
I am a student and my question is about finding the signal flow graph for a simple circuit.

I found the above formula for a \$k\$ node having \$U_k\$ potential. In the book it is said that this is a base for building the signal flow graph using nodes potentials.

\$k\$ is the number of the node,

\$U_k\$ it’s potential,

\$S_k\$ the sum of the admittances from node \$k\$

\$Y_{jk}\$ is the admittance between \$j\$ node having \$U_j\$ potential and \$k\$ node

\$I_{gk}\$ is the algebraic sum of currents in the \$k\$ node  (positive sign if he current enters in the node, negative sign if the current exits from the node)

Next , an example for this circuit for which we need to find the transfer function \$H(s)= \frac{U_2(s)}{E(s)}\$:

They write in the book the next linear system:

$$U_1S_1 = GE + GU_2$$

$$U_2S_2 = GU_1 + sCU_3$$

$$U_3S_3 = sCE + sCU_2$$

where:

$$\require {cancel} \cancel{S_1 = 2(sC + G)}$$

$$S_1 = 2G + sC$$

$$S_2 = sC + G$$

$$S_3 = 2(sC + G)$$

\$G\$ is the real part of the admittance \$Y_{jk}\$ or \$G = \frac {1}{R}\$.

From the above equations they find the equation of the potential in each node as:

$$U_1 = \frac{G}{S_1}E + \frac{G}{S_1}U_2$$

$$U_2 = \frac {G}{S_2}U_1 + \frac {sC}{S_2}U_3$$

$$U_3 = \frac{sC}{S_3}E + \frac{sC}{S_3}U_2$$

The resulting signal flow graph is:

If the \$S_k\$ is the sum of the admittances from \$k\$ node, how they calculated \$ S_1 = 2(sC + G) \$

I understand for node 2: \$S_2 = sC + G \$ (because I have one resistor from node 1 to node 2 and one capacitor from node 3 to node 2).

Why for the node 1: \$S_1\$ expression is not \$S_1 = 2G + sC\$? It is wrong in the book?

Later edit: the correct expression for \$S_1\$ is indeed \$S_1 = 2G + sC\$.

Where are the currents from the first formula?

Later edit: that term is equal to zero.

I need to understand because I have to find the signal flow graph for this circuit and based on the graph to find the transfer function using Mason rule:

Hope someone can help me!
Thanks in advance!

Best regards,
Daniel


texts: Simulation of blocking assignments in always @ blocks

texts:
Tracking down some weird simulation results, I found that the use of blocking assignments at clock edges was the culprit. More specifically, different simulators seem to treat them differently.

Take the following example:

module test;

reg clk, foo, bar;

initial
begin
  clk = 0;
  foo = 0;
  bar = 0;
  #10 $finish;
end

always
  #1 clk = ~clk;

always @(posedge clk)
  foo = ~foo;

always @(posedge clk)
  bar <= foo;

endmodule

Running this in Xilinx' ISim gives the following waveform:

This seems reasonable although I do find it a bit strange that a change in foo at a clock edge gets picked up by bar at the same clock edge.

The following waveform is produced by running the same example using Icarus Verilog:

This seems completely wrong to me. A change in foo from 0 to 1 is not picked up by bar at the same clock edge. However, a change in foo from 1 to 0 does get picked up by bar at the same clock edge (otherwise bar would change to 1 at the second positive clock edge I suppose).

So, I have two questions:

Which, if any, of these simulators is correct? In other words, how should the above code behave?
Are differences between simulators something we should always be aware of? If so, are there any guidelines on writing code that is deterministic across different simulators?

Note: I'm aware of the fact that using blocking assignments in always @ blocks is not a good idea and that using a non-blocking assignment in my example gives logical and consistent results. I'm asking this question because I'm currently debugging some third-party simulation code.


texts: Multi master SPI mode? Or any intelligent way to switch only time between two masters?

texts:
I have an LCD display which is powered from a pretty powerful micro, with GPU and all sorts of stuff. However, it turns out that it will take it over 5 seconds to boot the core. From a user experience perspective 5 seconds to see any boot up image/animation on screen after turn on is unacceptable.

So i was thinking of including a separate very cheap micro which can hold the master line for the first couple of seconds and provide the boot up image. It would then hand over the SPI bus to the main micro.

This of course is not the only use case of the smaller micro. I would also use it for all the backlight control. The larger micro might go into a sleep state and i would like for the smaller micro to still keep the display on. (So basically the main micro will simply tell the small micro what brightness to keep things on and a default brightness in case the main micro sleeps).

Is there any way i could hold the small micro as master for first 5 seconds and then let go to the main micro for the rest of the time (and as a bonus, hand it back to the small micro when the main micro goes into sleep)?

Thanks!


texts: How to calculate gain of opamp with Max446 chip?

texts:
I just wondering how do you calculate the gain of the amplifier in a circuit like this:

I am familiar with gain calculation on non-inverting and inverting opamp but am having trouble with this.

Any help would be appreciated.


texts: How do I determine how much battery and resistance is required to wire a series of LEDs?

texts:
I need to wire 5 led's in series with a switch and variable resistor to control brightness.

These I think

I think the circuit will need to look something like this (Ignoring the values the editor added!) but it's been a very long time since I've done anything like this.

simulate this circuit – Schematic created using CircuitLab

I don't know how to calculate how much battery power will be required, or if it will need additional resistence.

How do you go about solving these kinds of equations?


texts: BLE (blue tooth low energy) : what is the max length of a packet? (encrypted and unencrypted)

texts:
According to BLUETOOTH SPECIFICATION:
"The Length field of the Header indicates the length of the Payload and MIC if
included. The length field has the range of 0 to 255 octets. The Payload field
shall be less than or equal to 251 octets in length. The MIC is 4 octets in length."

Thus, what is not clear for me is : What is the max payload size?

it could be wether:

1) 251 for both

max payload size is 251 for both encrypted and unecrypted packet
max length for encrypted packet is max size + 4 (MIC) => 255
max length for unencrypted packet is max size : 251

2) 251 / 255

max payload size is 251 for encrypted packet, max length is 251 + 4 (MIC) => 255,
max payload size is 255 for unencrypted packet, max length is 255

User cannot send a unencrypted packet with a size > 255 because length field is a byte. So, when encryption is not enabled, there is nothing to do, buffer overflow is avoided by design.

But, I guess when coding an LL BLE API, we should check before sending a packet if its size is > 251, and warn user if necessary.
(case 1 for unencrypted and encrypted packets, case 2 for encrypted packet)


texts: Detecting Open Circuit, Short Circuit and Battery Reversal

texts:
I am facing various design challenges with a project that I am currently working on.

I've been trying to figure out a way to build a circuit that detects open circuit, short circuit, and battery reversal. I am dealing with a battery assembly of six nickel-metal hydride battery cells in series which has a binder connector consisting of 7 pins (battery baton).

When the batteries are fully charged, the voltage is a maximum of 9V, however, in the event of the batteries being fully discharged, the voltage is 5V. I have found a way to eliminate reverse polarity as I can use a P-Channel MOSFET.

I am using an Arduino microcontroller to carry out pin checks between pins that may be short-circuited. In order to detect an open circuit (pins that are floating), I can possibly build a current monitor circuit that uses a shunt resistor and the current flowing through the voltage being dropped across the shunt resistor can be measured.

I have attached the wiring configuration for the battery baton binder connector ends for two different battery batons and also a circuit that I have thought of that may do the trick for now.

Any ideas?


texts: How to increment OCR1A value in ATmega16 through hardware?

texts:
For my project I am controlling servo motors through ATmega16 micro controller. The OCR1A determines the position of motor.

I want to increment the OCR1A value through a hardware switch. I tried doing it through interrupt but it did not work.

Is there any other way?


texts: Panel mount micro USB extension cables: how do they work?

texts:
I need to expose the usb port on an arduino pro micro to the outside of a project box. I've been looking for some sort of panel mount extension cable, and all I've been able to find are ones that look like this:

I'm confused about why the middle of the plug is recessed like that; isn't that going to result in the usb port itself sitting behind the panel, rather than flush with the panel? I haven't been able to find a picture of one of these in use anywhere to verify.
If it matters, the case to which I'll be mounting this is a thin tin (formally it held pirate not-actually-band-aids; think an altoids tin, but slightly bigger).


texts:
Similar kinds of questions have been asked before it but they don't clarify how one can use this aspect in circuit.

I'm aware that a MOSFET is a bidirectional device and in one direction current can flow from Drain to Source upon giving a gate pulse of sufficient amplitude & through body diode in reverse direction.

Now, Lets say I have connected Drain to higher than Source and current is flowing through the body diode, But at the same time I want to turn on the MOSFET Source to Drain channel to allow current to flow from the channel from source to drain parallel with body diode. Is it possible ? In this case what should be the Gate potential will it be higher with reference to drain or source? I'm new to this domain & confused. Please Help!


texts: Making a binary counter for my breadboard

texts:
I have this component called a breadboard friend. It has a 9V battery that is lowered to 5v so we can power most AOI logic chips. It has a built in 555 timer and a potentiometer. It  has 4 leds to link outputs from our logic circuits to - and it has 4 spst switches that are used to simulate binary values:  0000 or 1000 etc.

What I want to do is make another part of this circuit that can simulate counting in binary for me up to X values. This way I can plug in the switches to the digital output and maybe press a switch to increment through the truth table.

I was thinking I could use the onboard 555 timer and use that somehow but I am lost.


texts:
I have a circuit I did in Altium.  I did auto trace; everything looks good but when it's converted to Gerber it shows a lot of weird marks and traces.  So I went back and undid all the traces and made a Gerber of just the plain ICs on the board. Like this image:

But the Gerber moves things around like this:

How can I fix this issue?


texts:
The AT32UC3C ADC can be set up using either internal or external references as seen in Table 36-8. For any type of voltage reference used, the datasheet suggests that the ADC is capable of converting negative and positive voltage levels. However, Table 40-30 mentions that the ADC input voltage range is 0V to VDDANA, and the absolute maximum rating in section 40.1 mentions that the absolute minimum on ANY pin should be -0.3V. It appears I shouldn't really be feeding in a negative voltage.

So my question is, how does one read a negative ADC value given the electrical ratings on the pins? Wouldn't the pin just blow up because it can't accept negative voltage values?

EDIT: I realized I phrased the question more as how to measure negative ADC values in general. However, my real question is really about why UC3C specifies negative voltage for its ADC conversion range, so Spehro's answer is the one I am looking for.


texts: Can I use a 25 meter LED stripe with a single power adapter?

texts:
I have 5 stripes of 5m length and 300 RGB LEDs (type 5050) each. One LED consumes about 20 mA at 12 V. Therefore, my whole 25m setup would use about 30 A.

Is it safe to connect the 5 stripes series and powering one end with a 30 A power adapter? I wonder whether the small traces on the PCBs can handle that. If that's not possible, what would be a safe setup?


texts:
I am designing a device around the STM32L476. My device is primarily battery-powered, but has a USB port that, when plugged, I want to use as an alternative power source (through a 3.3V regulator) to limit battery drain. It is also possible that the user connects the USB port while there is no batteries.

I want to be able to sense when the USB port is connected, so I'm using PA9 as OTF_FS_VBUS.

The good news: the datasheet says that the PA9 pin is 5V tolerant.

The bad news: 5V tolerant pins seems to actually be 5V tolerant only when power is applied. Datasheet §6.2 table 18 says:

  Max input voltage on FT_xxx pins: min(VDD, VDDA, VDDIO2, VDDUSB, VLCD)+4.0V

In my case, if there is no batteries and the user connects the USB port, there is a time, before the regulator starts, during which the voltage on PA9 will be 5V while no power is applied at all on the CPU supply pins.

The even more bad news: current injection is not allowed: datasheet §6.2, table 19, says:

  Injected current on FT_xxx: -5/+0 (see note 4)

  Note 4: A positive injection is induced by VIN > VDDIOx while a negative injection is induced by VIN < VSS. IINJ(PIN) must never be exceeded.

So it seems I can't use a simple resistor to limit excess current on PA9 during the time the regulator starts. Any amount of current that would flow from VBUS to PA9 before VDD ramps up is apparently forbidden.

What did the others do ?

I had a look at numerous designs around STM32 chips, looking at their VBUS connections, and they don't seem to care. They connect VBUS directly to PA9, or eventually through a resistor, but I never saw anything more complicated. But they mostly are development boards, so I guess the ruggedity (is that a word ?) is not very important. And they are usually not powered through the USB port, and certainly assume the user won't connect USB port before powering the board.

What is my plan ?

Putting this between VBUS on the USB port and the PA9 pin of the MCU:

I really tried to keep it simple. Basically, it ensures that VUSB_CPU (which is the PA9 pin) can never be above VCPU + 4V (Vz+Vbe), without consuming any power if it is OK.

My main questions are: Am I right in my analysis ? Is this circuit a good solution ? Am I worrying about things that are irrelevant ? Why nobody else seems to care about this potential problem ?

Additional question: I plan to use USB OTG. Is that a problem if there is a 4.7k resistor between the connector and the PA9 pin ? I guess it would be if I had to use VBUS pulsing during SRP, but this method is apparently deprecated. So am I good, whatever the role (device/host) of my device ?

A last one: What is the max current drawn by the VDDUSB supply pin ? The datasheet specifies, for the USB peripheral: 16.4µA/MHz for AHB clock domain + 23.2µA/MHz for independant clock domain, but we don't know from where it is drawn (VDD or VDDUSB).


texts: Bi-Directional Step up and Step down (3.3v  5, etc)

texts:
So I've been reading a few threads here and on other forums.  I understand there are various solutions for stepping down or up a voltage.  What I have found are the LVC series shift regs that give a constant ouput, MCP1825 which will step down 5 to 3.3 (and other versions which have different increments) the 74LCX245 which will step 2.5 or 3.3 to 5v and perhaps some others I am forgetting. Then there are ready made boards such as the Sparkfun converters or this 8 pin to 8 pin converter. But all of these are one direction only, or bi-direction switched by a jumper.

How would I convert voltages down or up in both directions without requiring a pin select.

5--3.3

5--2.5

5--1.8

thanks


texts:
I'm putting together a circuit to supply power to a step down buck converter from a battery 12-15V. I would like my circuit to be "on" when a separate 12-15V circuit has power, or when a 3.3V signal from a Raspberry Pi is high.

I drew the circuit below. To my very beginner mind, it seems like it should work. Is there anything I'm missing? The diodes are there just in case the 12-15V inputs spike for some reason. Do you think I need resistors to limit current anywhere? Would some capacitance somewhere help if the inputs are noisy? (There are a bunch of capacitors in the regulator circuit.)

Datasheet for Q2: https://assets.nexperia.com/documents/data-sheet/PSMN017-30PL.pdf

Datasheet for Q3: http://www.vishay.com/docs/91310/sihld120.pdf


texts: How to measure the angle of a rope on a moving airplane?

texts:
I've got a simple rc plane which I want to fly on a tether. The tether is attached to the bottom of the plane like this:

I now want to know what the orientation of the rope on the bottom of the plane is relative to the plane.

Some idea's I had:

1: IMU

I've got an IMU which I'm building into the plane (together with a raspberry pi). I guess I could also attach an IMU on the rope and calculate the differences between the two, but since the plane will be moving a lot I guess this wouldn't be the easiest/best option.

2: radar

I thought of attaching some kind of sensor on the rope about a meter below the plane and 4 sensors on the plane; one at the end of each wing, one in the front and on at the rear of the plane. If needed by the technology I could move the sensor on the rope closer or further away from the plane. It could be anywhere between 10 cm and 5 meters.
I then need to measure the distance between the sensors on the plane and the sensor on the rope. Combining that information with the position of the sensors on the rope and the plane I can calculate the orientation of the plane on the rope. I wonder what kind of sensors I could use though. As far as I understand Lidar is not a good idea because measuring distance using light is difficult at such a small distance. That means maybe radar is a better idea, but I don't really know if this is feasible.

3: infrared

Another idea I had was attaching an infrared light on the rope and using an infrared camera on the bottom of the plane with blob detection to find the location and calculate the angles of the rope using that location. I'm not sure whether this would work by day though, and it might have some other disadvantages that I'm unaware of.

4: rotary encoders

I could also attach two rotary encoders on the plane and attached two very light wires on the rope. It would enable me to measure the distance/angle relatively precisely, but it would also make it quite fragile when landing the plane.

Precision

I don't need very high precision. If the sensor on the rope would be a meter away a precision of 10cm would be fine. Also, I could average the measurements of the four sensors and I guess that would make it more trustworthy.

All tips and ideas are welcome!

[EDIT]

@DaveTweed said this was an XY-problem (which I had never heard of, so I looked it up). So let me explain what I want to do. A company called AmpyxPower is flying RC-planes on a tether to make it create a pull on the tether. That way they can generate energy with a generator on the ground. I'm curious if I could build such a system. I know I'm really far from reaching that point, but the first part would be flying the plane on the tether in the wind. After this, I want to make it be able to fly in an eight-figure autonomously. I'm currently writing a first version of the code that should do this. It's in very early stage, but I'm just trying to collect the data that it needs. As said I now have an IMU, GPS (although I'm not sure how much that is going to help me) and I also want to know how the tether pulls on the plane. For that reason I want this information.


texts:
I am using a LDO with a SOT-223 footprint and since it might get hot, I wanted to make a nice thermal pad under it to dissipate that heat.
I googled and I only found thermal pads, but i wanted some guidelines on thermal vias to dissipate the heat to other layers. Could some one please give me some reading material?
I want to know how far to place the vias from each other, how many vias to use and the size of them.

EDIT:
The part is the MCP1703 but I think this question is more related to the footprint than the part itself


texts: Random clock Generation with unequal 1s and 0s distribution?

texts:
We need a pseudo-random clock with a length N, in such a way that out of every N clock pulses, M of them should randomly made zero (M<<N). What we want to do is to sample a signal in a random fashion. Meaning that, out of every N sample points (from Nyquist grid) we need to take M samples. Then through some processing and assumptions about signal structure, other un-sampled (N-M samples) points are recovered.
Now I am using Linear Shift Registers, something like below:

simulate this circuit – Schematic created using CircuitLab

It works good, however, I do not want equal distribution for 1s and 0s, I mean I want something like 20% of clock cycles to be 1 and 80% to be zero.
To achieve that, I made to AND output of two circuits like above to change probability from 50% for both 1s and zeros to 25% for 1s and 75% for zeros (in figure below, with different seeds).

simulate this circuit

It is good at the cost of doubling the power and chip area:( . I am seeking a way to make the system work with only 1 random clock generator circuit, not two.

Is possible through implanting some special initial seed change probability distribution of 1s and 0s in output sequence ?
Is there any power-area efficient method to accomplish this?

I was thinking to store a random binary sequence (with length of N) in a ROM and then And its output  with the clock to make a random clock.


texts: Using register retiming to pipeline a module

texts:
From my reading I understand that modern synthesis tools are able to perform register retiming where registers are moved between combinational logic to meet timing constraints.

So for example in your HDL you would describe comb -> reg1 -> reg2 -> reg3 and the tools would move those registers to get comb1 -> reg1 -> comb2 -> reg2 -> comb3 -> reg3.

When would one manually pipeline logic rather than depending on register retiming?


texts: Why do fans keep running after power-off

texts:
What is the reason why the fan of many electronic devices, such as video projectors, laser printers or kitchen ovens (have to) continue running after the device has been powered off?

It is my understanding that fans are required to bring fresh air for cooling to the device. Without it, the device might overheat. But once the device is powered off, there is no more source for the heat, and therefore no more risk to overheat.


texts: Deriving Transfer function from position block diagram

texts:
For the system shown below I am trying to get the system function.

I tried putting it into the equation:

$$T(s) = \frac{C_G(s)}{1+C_G(s)\cdot H(s)}$$

where $$ C_G(s) = \frac{K}{s(s+3)(s+4)}$$ and $$H(s) = \frac{8}{(s+7)}$$.

But this didn't give me the correct answer which is apparently: $$T(s) = \frac{K}{s^3 + 8s^2 + 15s + K}$$

Any help with this will be greatly appreciated!


texts:
Can someone explain me the difference between USB and ULPI?
I know they are closely related but how they are related that not clear to me.

First time I came to know when I was looking at this board (See at the bottom middle):
Xilinx Zynq-7000 All Programmable SoC ZC702 Evaluation Kit


texts:
I'm programming an ATtiny2313, with some hex for an infrared remote IgorPlug with AVR via USB, I'm new to AVR and need to confirm please that what he refers to the fuse configuration:

Q: Is possible to use ATtiny2313 instead AT90S2313?
A: The device is compiled for AT90S2313 but works also on ATtiny2313 - same HEX file (binary compatible). For correct operation on ATtiny2313 you must set fuses during programming: disable division the external clock by 4 and enable high speed XTALL.

So is this correct?
low: Oxff
High: 0xff
Extended: 0xff

I need to use a 12 MHz xtal


texts: How would I measure distance with a transmitter/receiver pair?

texts:
I am looking to build a a device that can transmit/receive its distance from another device, with the other device doing the same up to 50 meters. Will using a fm transmitter and receiver with a microprocessor be able to do this?

I just started in Engineering at university so I don't have a broad background in electronics.


texts: Voltage Regulator: how to compensate for voltage drop in cable?

texts:
USB devices reduce their current consumption with decreasing voltage. This is because the maximum current ability of a dumb USB charger is unknown to the device and the charger signals reaching the current limit by lowering the voltage.

As a side effect the current consumption of the device (and therefore the charge speed) also decreases with increasing cable length. This is the problem I'd like to solve.

Since the USB cable has 4 wires it would be easy to modify it, so that I can sense the voltage at the end of the cable, just a few mm before the connector.

Searching for a solution I found LDOs (example: LP3856) that have an additional sense pin.

Q1: Would such an LDO solve my problem?

I guess that it would only compensate 50% of the voltage drop since half of the drop happens on the GND wire? (Q2)

Q3: Most adjustable linear regulators have an V_adj input. Could I "misuse" that input as sense pin simply by connecting one end of the voltage divider to my sense wire?

Q4: Many boost/buck converters also have some external circutry for feedback. Would the trick from Q3 work there also?

Q5: Any other suggestions to solve my problem?


texts: Button is giving me the same voltage when pressed or released

texts:
I am doing a simple program with my PIC (PIC24FJ1024GB610).
When a button is pressed the LED is turned on, when it is released LED is turned off.
I presumed that the input pins have a pullup resistor connected to it inside the microcontroller by default, because when I measured the voltage across the pin when it was floating, it was 3.3V

simulate this circuit – Schematic created using CircuitLab
In a pull-up configuration, Vinput is 3.3V when the button is released, and 0V when the button is pressed.
However, when the button is pressed or released I measured the same value which is 3.3V
I am using a breadboard to design the circuit, and a pic development board: Explorer16/32
I added the code FYI.
#include "System.h"
#include <xc.h>

/*

 P44 is input RB15
 P88 is output RF1 5V tolerant

 */

#define ANALOG  1
#define DIGITAL 0

#define INPUT   1
#define OUTPUT  0

//BTN RB15
#define BTN_ANS     ANSBbits.ANSB15
#define BTN_TRIS    TRISBbits.TRISB15
#define _INPUT      PORTBbits.RB15

//LED RF1
#define LED_TRIS    TRISFbits.TRISF1
#define _OUTPUT     _LATF1

int main (void)
{
    //LED_ANS = DIGITAL;
    LED_TRIS = OUTPUT;

    _OUTPUT = 0;

    BTN_ANS = DIGITAL;
    BTN_TRIS = INPUT;

    while(1)
    {
        if(_INPUT == 1)
            _OUTPUT = 1;
        else
            _OUTPUT = 0;
    }

    return 0;
}


texts: Where would I find or how would I build a laser driver for a 2W laser diode?

texts:
I have two laser diodes but I have no idea where to begin building my own laser driver. I would prefer to make my own but I will buy one if that isn't a good idea.

Does anyone have a schematic of a basic driver with the required functionality to keep me from burning the diodes or does anyone have any suggestions on where to get one?

I have seen the basics for schematics on the internet but I have no idea what I need to do to adjust for a 2W laser.

Specs:

2W 808nm (2.8 to 3v at 1.5A)


texts: Converting 0-5 volts (linear) to +2.5 -- 0 -- +2.5 volts ("vee")

texts:
I'm trying to find a simple way to convert a 0-5 V output from a joystick hall effect sensor to +2.5 -- 0 -- +2.5 V. Here's how I want the response to look:

The output voltage will be sent to a frequency converter and on to a stepper motor driver. I want to have the same voltage at both extremes so the frequency (motor speed) is the same regardless of the positive or negative direction of the joystick. I intend to use a comparator at the zero point (with an appropriate deadband) to reverse the direction of the stepper driver.

I've thought of a few ways to accomplish this, but none seem to be particularly straightforward:

Create a second, inverted output from the sensor and switch the input source (via comparator and mux) to the frequency converter at the 2.5 V midpoint. This would provide 2.5-0 V from the inverted output and 0-2.5 V from the original output.
Shift the 0-5 V range to -2.5-2.5 V and then use an absolute value circuit to invert the negative portion of the output.
Generate a bias voltage, based on joystick position, and add/subtract it from the sensor output.

Ideally, I'd like to have a single input to the frequency converter instead of trying to switch it to another source, such as an inverted output. The second idea above would satisfy that preference, but it would require a negative voltage source. Also, I'm trying to use discrete components in this design, so a microprocessor isn't an option for me.

Is there an easier way to accomplish this task? The problem seems fairly straightforward, but I'm having trouble coming up with a simpler solution. I appreciate the help.


texts: Would a digital compass work reliably when installed in a car?

texts:
I'm working on a project that needs dead reckoning sensors to combine to GPS readings, and is to be installed under the dashboard of a car. Currently I have an accelerometer and a gyroscope for that.

I'm thinking of getting rid of the gyroscope, since - given it's almost (or completely?) impossible to make sure it is at the axis of the car turns - its readings improve little over what the accelerometer gives. A digital compass would be much more useful, but I'm not sure it'll work OK inside such a big metal body; not to mention the many sources of EM that can interfere with it. And there's no point in shielding it, I'd be shielding away the earth EM field too.

I'm especially worried about making something that appears to work initially, only to have field problems later.

Anyone had similar experiences or information to help me decide?


texts: AP9211 Battery Protection Circuit, Datasheet suggests shorting the negative terminal of the Battery to ground

texts:
Question
I used to use the Chinese DW01A as a protection circuit for prototyping. The initial prototype worked and I have to switch to a western chip now.
For this I have chosen AP9211 because it is very similar to the DW01A. It even has the P and N Channel MOSFETS inside the IC so that is another advantage.
However something about the typical application circuit of AP9211 bothers me. It shorts the negative terminal of the battery to ground. This was not the case in the DW01A and I don't really understand the reason for this. Wouldn't this defeat the purpose of the protection IC? I would appreciate any explanation, as this leaves me scratching my head.
Here are the typical application circuits and the block diagrams:
DW01A:

AP9211:

Links to datasheets:
https://www.diodes.com/assets/Datasheets/AP9211.pdf
http://hmsemi.com/downfile/DW01A.PDF


texts: I was doing this circuit which I found on the Internet. My question is what is the logic behind the functioning of this circuit? Thanks!


texts:
I am designing a custom board using HMC833LP6GE. I am taking schematic reference from the Evaluation module. There will be onboard DS-PIC MCU for controlling the PLL. The reference input can be fed external or through an on board crystal.
I am designing it on 4 layer card with following stackup.
TOP - SIGNAL
LAYER1 - GND
LAYER2 - PWR AND GND
BOTTOM - SIGNAL
I am unable to find the layout guidelines for designing.
I need some critical and important points while designing a PLL.
For example:-
Loop filter is the heart of the PLL design. What care should i take with respect its placement?
Can I place few components on top and few on bottom layer?


texts:
In my schematic, I found that the base of transistor Q7 (2n2222) was damaged. I tried to replace it with a BS170 MOSFET, and the same thing happened where the gate was damaged.

The microcontroller has a simple operation where it activates Q7 with a cycle of 0.8 seconds on, 0.2 seconds off, driving 24 MOSFETs in parallel. The MOSFET controls an external source of 100V, 100A.

There's also an overcurrent protection circuit that is not pictured. When overcurrent is detected, a signal is sent to my microcontroller and this cause Q9 to be activated.


texts:
Is there a way to produce Gerber files from command line in KiCAD (Linux/Unix) or a tool which can do it for me? The same question for SPICE netlist and BOM xml?
I need it to automate this process within a CI-pipelie. GUI is not useable here.


texts: How to process energy (kWh) meter reading data of half-hour interval

texts:
If I am to process time series of energy data (point estimate every half-hour interval), and fit it into the following formula for dimension reduction:

Haben's paper

I was advised to use power, not energy. Yet power is the rate at which the energy is formed. I still don't see how other than to use the values as it is. If I convert it into hourly value, it would remain the same. Must I divide by 2 to indicate that they are half-hour interval values? Then isnt it the same not applying? Since you would be normalizing with the entire year's data.

Aside from the energy/power concepts, (or maybe relevant) I actually was a bit confused how to process it to sample the time period from 6.30 am to 10.30 am for instance. If it is a point estimate, how can it be in unit of kWh?

Should perceive that the reading at 6.30 am is the electricity consumed from 6 - 6.30 am or now that I think if it is 5.30 - 6.30 am...

May I ask for clarification from anyone with solid experience in this matter? Thanks


texts: Contradictory information in LM339 datasheet

texts:
I am inspecting the LM339 datasheet (link) and I find contradictory information regarding the operation principle.
Page 10 states:

  The output consists of an open-drain NPN (pulldown or low-side) transistor. The output NPN sinks current when the positive input voltage is higher than the negative input voltage and the offset voltage.

But page 12 says:

  If IN– is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking
  current.

Which one should be considered?


texts: Capacitor after Voltage Reference "for stability"

texts:
I've got a lot of experience with rather "low-level" electronics (resistor networks, passive filters, basic op-amp circuits) and some experience with higher-level stuff like micro-controllers, but I am currently struggling with learning the bits in between. As such, apologies if this question is daft or an obvious duplicate but here goes.

I have been working on a circuit which a colleague of mine designed which includes an LTC6655 2.5V voltage reference. In the circuit, and on the datasheet, the device calls for a 10uF cap to be placed on its outputs, but it doesn't say why. Since I was waiting for a delivery of 10uF caps and only had smaller ones, I foolishly assumed it was just there for line smoothing/filtering and decided that it wouldn't make a difference to the testing if I just left that part out until the delivery arrived.

Of course when I powered up the circuit, the reference was only putting out 1.75V instead of 2.5V. After checking all the inputs and outputs thoroughly, and the load parameters, I was stumped and went back to my colleague who pointed out the missing capacitor as being needed "for stability". I skeptically installed the needed part (which just arrived) and immediately the thing worked as expected.

Would anyone be willing to point me to a text to explain what that capacitor is doing, or even to explain it to me themselves? I would greatly appreciate it.


texts: Getting Raspberry Pi or Arduino to control three clock hands separately

texts:
I want to make an analog subway countdown clock. The idea is to have an ordinary clock with three hands. These hands will point to the number of minutes before the next, second next, and third next train arrives at my local subway station (one of the L stations in Brooklyn, NYC).

I was thinking to implement this using a Raspberry Pi. The software part is easy; however I have no idea how to get started on the hardware part. Is it possible to get a motor which can control three clock hands completely separately but on the same shaft? Or is there another mechanism that could address this problem?

I did some research, and you can buy hardware to control an hours-minute-second clock, but the problem is that you can't decouple the hands and get separate control on each of them.


texts:
This question is in regards to a configuration where I want to setup a half-duplex SPI bus, with a master outputting a clock at 1MHz.

Does the slave need to know that the clock coming in will be 1MHz?


texts: Understanding Noise Figure of LNA (HP 461A amplifier)

texts:
I have recently got a HP 461A linear amplifier (from the 60's) which works from 1Khz to 150Mhz.
I have checked that:

it's input gives a SWR <1.1 across all spectrum (i.e., the input impedance is very close to the nominal 50ohm).
The 40db Gain is very flat across the spectrum, with +/- 1db deviation at most.

Now I am trying to calculate it's noise values (Factor, Figure, Noise Density, etc), and I want to understand all calculations mostly for educational purposes.
I have a HP 8591E spectrum analyzer so I did the following:

Connected a 50ohm terminator at the input of the amplifier
Connected the output of the amplifier to my SA.
Configured the SA to take into consideration the 40db external amp.
Used the "Noise Marker" functionality to measure the noise density power in dBm/Hz.

The result is a reading of about -160dBm/Hz (at the moment, summer, room temperature is 300K) See: https://www.dropbox.com/s/udp72vmsg0yqlfh/dbm1.png
I am still a bit surprised by my measurements. They seem too good to be true for this >50years old unit. Doing some calculations,

-160dBm/Hz is equivalent to 1e-19 Watts/Hz(https://www.wolframalpha.com/input/?i=-160+%3D+10*log_10%28p%2F0.001%29)
From this I can (using the formula from https://en.wikipedia.org/wiki/Noise_temperature) calculate the Noise Temperature T=24.1  (https://www.wolframalpha.com/input/?i=1e-19+%3D+t*300*k%2C+k%3D1.381*10%5E%28%E2%88%9223%29)
From this (again using the equation in https://www.wolframalpha.com/input/?i=-160+%3D+10*log_10%28p%2F0.001%29) I obtain a Noise Factor of 1.08 (https://www.wolframalpha.com/input/?i=%28300%2B24.1%29%2F300).
Taking 10*log_10 of the Noise Factor, I obtain a Noise Figure of 0.33.

All these numbers seem quite impressive. Are they really possible? Granted this HP 461A amplifier did cost >300 USD in 1964 (more than 2k of todays USD, accordingly with https://www.usinflationcalculator.com/)... but is it possible that it is really so good, even compared to today's amplifiers?
Regarding noise, it's original Manual/Datasheet only says "less than 40uV of equivalent wideband (150Mhz) input noise".
Perhaps, rather than focusing on the specific measurements of my amplifier, I'd just like to know if my calculations are correct/sensible. So:
GENERAL QUESTION: If I read in a datasheet that a LNA has noise figure of 0.33, how much should I expect (from purely mathematical calculations) when I plug a 50ohm resistor at the amplifier's input, and measure the noise power density (in dBm/Hz) of its output with a modern spectrum analyzer?
NOTE: I have also asked this question on the EEVBlog forum (see: https://www.eevblog.com/forum/rf-microwave/help-understanding-noise-figure-of-amplifier/msg3134954/#msg3134954 )


texts:
I am working on a hobby design and thinking of using the CC1120 for my RF transceiver.  One thing that has me confused, however, is the matching circuitry on the RF input and output of the CC1120.  I'd like to focus on the RF output of the device for the time being as it is single-ended and thus appears the easiest to tackle first.

The image below shows the RF output, pin 17 "PA", being fed into a SAW filter integrated circuit and then to an antenna or SMA connector output. However, in parallel is a passive component network between Vdd and ground. I'd like to better understand the purpose of this passive network, and I've yet to find anything describing the purpose of the network in the datasheet or user guides.

The datasheet mentions that pin 17 "PA" needs to have a DC path to the supply voltage.  When I look at the passive network, the inductor L171 will be a short at DC, the capacitor C173 will be open, and the caps C171 and C172 will be open. So the DC path is through L171 and R171 to Vdd. Makes sense, but I'm not sure why that is important...but the vendor says make it so.

At RF though, it is my understanding that the inductor L171 would act as a choke, blocking any noise/interference from the Vdd or ground rails on the RF output (pin 17 "PA"). At f=915 MHz, then

$$Z_{L171} = j \cdot w \cdot L171 = j57.49 \Omega$$

That seems like a rather small value for an RF choke though.

Also, my guess is that C171 and C172 are decoupling capacitors?

What is the purpose of the parallel RC circuit (R171 and C173), and what about C171 and C172?  I would greatly appreciate any ideas or insight into the reasoning behind this passive network on the RF output.


texts: Anti-static bags - safe to support powered circuit boards?

texts:
Is it generally safe to rest a low voltage powered up circuit board on an anti-static bag when debugging? A simple meter reading suggests it is a good insulator, but it must conduct to some extent?

Ditto on anti-static mat on the workbench


texts: What's the name for a dual-coil SPDT latching relay that doesn't latch?

texts:
A while back, I ran across an intriguing relay variant. It's a single pole double throw relay with two coils, where the contactor normally sits in the middle between the two contacts. In other words, it's normally open, and by triggering one coil or the other you can get it to contact one side or the other.

It's like a single-pole double-throw latching relay (the type with a separate set coil and reset coil), except that it doesn't actually latch - when power is released neither contact is contacted by the contactor.

Is there a common name for this?


texts: Serial stacking Linear regulars to increase Vin range

texts:
So I can buy a Positive Linear Regulator rated for -60V input (LM317HV). But the Negative Linear Regulators are -35v (LM7909) range. Yes there are a few odd parts that are -40v or -50v, but none I've found are -60v.

My question is, can Linear Regulators be serial connected to increase the operating range? or is there are simpler way to increase the Input rang I've missed?

My thought was having the first regulator inline with a Zenor Diode (25V) to get it to handle the raw 60V and feed its output (under -35v) to a second to produce -9v. It would have to scale or the first NLR would drop out as the voltage sags to -12V so that the circuit and still produce the -9v.

Specifically I'm looking for -9v from an input of range -12 to -60.  And in the 10mA range, which would dissipate 500mW


texts:
This is the circuit of a basic RC differentiator, with the input/output voltage waveforms.

First of all, I don't understand why there is decrease in the output voltage (discharging of charge from capacitor) as long as the supply is still on.
Secondly, I don't get why the voltage across the resistor falls to a negative level.

I know it is a simple question but please help me to understand this basic circuit - thanks.


texts: Could these ICs from Alibaba be counterfeit?

texts:
I'm trying to source some parts for a kit and the most expensive part I have by far is the DS1307+ RTC chip. They run about $4 in single buys and $1.96 in larger quantity.

But then there's this: http://www.aliexpress.com/item/100-PCS-lot-DS1307-DIP-8-1307-64-x-8-Serial-I2C-Real-Time-Clock-Free/552264214.html

They are selling the same (supposedly) chip for $0.12!

What I worry here is that these are just counterfeits and will have a high failure rate.

The numbers below DS1307 on the chip in the picture is a little different than the chips I bought from Mouser, but I'm not sure what they mean. Anyone know?

Is there anyway to tell if these are legit?


texts: PCI device address actually means slot address? And when does PCIe slot get its' address?

texts:
I'd like to clarify how the configuration address space in PCI and PCIe works.
Namely, a PCI peripheral on a bus is addressed with device:function pair (the bus or domain:bus are not included, since only 1 bus is considered).
How is device address determined? What sets it?

According to the answer in this question on superuser and other texts the device address is actually address of the PCI slot, and thus it should be wired in the hardware during manufacturing. Is it correct?

Then, how is this address defined in PCIe case?

From the same answer:

  each device has its own individual point-to-point serial connection to its upstream device

-- thus, in PCIe each slot is connected to upstream switch device in star topology. And addresses of the slots are re-assigned by the switch on reset? (So, on power-up the switch calls for devices in each slot and if there is a response the switch assigns device address to the slot?) As in  the same answer:

  (hence each bridge, including the top-level "root complex", tells each device what its device ID will be)

Or they are also resolved in hardware/firmware of the switch? (And the switch always has a device address assigned to those wires going to a slot.)

It seems for easier hot-plug-ability each slot should have permanent address on the bus (on the "network" of the PCIe switch).


texts: MPU 6050 accelerometer generating gaussian noise with strange gaps

texts:
I was using an GY-521 accelerometer/gyroscope module in order to provide inertial tracking. The GY-521 interfaces with an Arduino which sends data over a serial connection. I convert these values into physical values (simply multiplying by a calibration constant) in a python script and then append all values to an array which I have plot into a histogram shown.

I left the sensor stationary on a table top for approximately 10 minutes to try and work out the nature of the noise.

As you can see from the histogram certain values of acceleration never had a single observation and these values appear at regular intervals. Some values also seem to be much more common than the rest of the noise.

(Main question) Is there a physical explanation for this?

(Sub-Question) What type of filtering/smoothing would you suggest to improve this? We first implemented box smoothing which worked well at preventing drift when stationary but made the system less responsive to sudden changes in rotation. I explored heavily the use of kalman filters but without a magnetometer to give measurements for attitude I could not work out how to use accelerator data for both correction of orientation and displacement tracking (since moving around with acceleration in the order of g makes the gravity vector ambiguous). Without proper smoothing of the angular velocity data the reference frame is rotated with sensor noise making drift significant after only a few seconds of running.

[EDIT]: The code running on the Arduino is from this github repository. The python script is shown below. To my knowledge the histogram is plotting raw data (multiplied by a constant).

import serial
import time
import matplotlib.pyplot as plt

#establish serial connection to Arduino/GY521
ser = serial.Serial('COM3', 38400) #Baud rate 38400 Hz, COM port must match.
ser.flushInput()
for i in range(0,3):
    print(ser.readline(100).decode("utf-8","ignore").replace('\r\n',''))

res = 2**16;
# sensitivity setting
a_sen = 2* 9.81; #m/s^2
g_sen = 250 ; #deg/s

ax = []
ay = []
az = []
gx = []
gy = []
gz = []
t  = []

#main loop
try:
    print("Capturing data, press ctrl+C to finish")

    #obtain data
    while 1:
        s = ser.readline(100)
        #print(s)
        ss = s.decode("utf-8","ignore").replace('\r\n','').split('\t')
        ss = ss[1:]
        ax.append(ss[0])
        ay.append(ss[1])
        az.append(ss[2])
        gx.append(ss[3])
        gy.append(ss[4])
        gz.append(ss[5])
        t.append(ss[6])

except KeyboardInterrupt:
    print('Stopping...')

    #convert the read values into physical values
    ax = [int(i)*a_sen*2 / res for i in ax]
    ay = [int(i)*a_sen*2 / res for i in ay]
    az = [int(i)*a_sen*2 / res for i in az]
    gx = [int(i)*g_sen*2 / res for i in gx]
    gy = [int(i)*g_sen*2 / res for i in gy]
    gz = [int(i)*g_sen*2 / res for i in gz]
    t = [int(tm)/1000 for tm in t]

    plt.figure(1)
    plt.subplot(211)
    plt.hist(ax,"auto")
    plt.xlabel('Accel (m/s^2)')
    plt.legend(loc = 'center left',bbox_to_anchor=(0.975, 0.5))

    print('Done')
    plt.show()


texts: MicroSD card SPI initialization irregularities

texts:
I've implemented the start-up sequence for SPI mode on MicroSD v2 cards (using the specifications), and I've found that the SD card fails initialization at different points in the process. It often fails sending the first CMD8, but then sometimes fails later at the ACMD41 or even after that. By fail, I mean it'll return 0x00 or an incorrect response.

Are there any ideas on why the initialization process can fail at different steps? It appears I'm supplying the correct power, and there are no pullup or pulldown resistors needed for SPI. I'm bare-metal coding, so there's no OS to interfere with it. Posting code here is non-trivial as every step uses callbacks (no choice, due to timing requirements). I'm coding for the nRF52840, and ARM chip.


texts: Is there an adapter for a TO-220 part to go into a TO-3

texts:
We have an old board that we do not want to redesign because it is near end of life. However, there is a TO-3 5V regulator that we can not source and when I do find it, it is for $13.

I am wondering if someone makes an adapter to solder a TO-220 5V regulator to a TO-3 adapter as that would be the easiest solution. The next easiest is to just make a small pcb that does this which we may end up doing.


texts: Finding matching male / female connectors

texts:
I've been having trouble finding pairs of connectors. I need a set up exactly like https://www.artekit.eu/products/prototyping/wires/jst-ph-4-pin-cable-with-male-female-connector/

However, I need to buy the male and female parts separately. So, I'm looking at male connectors like https://www.digikey.com/product-detail/en/jst-sales-america-inc/S4B-ZR-LF-SN/455-1671-ND/926578

But then how, having just the male connector, do I go about finding a female connector which I know will fit into the male connector?

I'm having a lot of trouble figuring out how to verify my connectors will fit correctly. I would think the male and females would be linked in some manner that I'm missing?


texts:
What happens if an induction motor given with 3 phase supply is forced to rotate with synchronous speed in

a) same direction

b) opposite direction

Please help me with the above problem.
I think in the first case, the current induced in rotor will be 0. So, no losses in rotor.

In second case, slip will be 2.


texts: How to calculate the current rating of different metal part (copper and brass) used inside a switch/socket/plug?

texts:
How to calculate the current ration of different metal parts normally used in household electrical appliance product like switch, socket, plug etc. How do i know that, the parts i have chosen that is suitable for particular current rating.I need to know the below topics

Effect of copper or brass metal parts
Relation between thickness of metal parts and current rating of those parts


texts:
I'm trying to find a small supercap for an energy harvesting application, but I can't seem to find one after hours of googling. Loads of pdfs say "Capacitance, 1mF to 100F" or something, but I can never find anything under 5mF. I actually only need about 600uF, but the more the better.

The constraint is that it has to be as small as possible, preferably a coin cell type thing no taller than 2mm, although I imagine that might be pushing it, although maybe not because this one (http://www.farnell.com/datasheets/2024570.pdf) is a good diameter, but is 5mm and 10mF. Non-radial ones are fine, they just have to fit inside a 20mm diameter circle. Thanks for any ideas!


texts:
I'm trying to drive a capacitive load with P and N mosfets in a half H bridge. The problem is that my control voltage is 1.8V, and the H bridge is switching 20V. My original plan was to use npn's to switch the drive to the mosfets:

simulate this circuit – Schematic created using CircuitLab

The problem is that in this configuration, the Vgs will be 20V at times, far exceeding the 12V max listed for many mosfets. Is there a solution for this?

Edit:

Now that I think about it, will this work?

simulate this circuit

Are there any major problems, except slower turn on/off?


texts:
I have a script that convert Eagle PCB to Altium PCB. It creates the components, tracks, pads, etc. Everything works ok. I can click on "component" like the resistor footprint, and move it, etc.

Now, I would like to include those components onto my own footprint library, but I cannot find how to do it.


texts: Arduino Uno SoftwareSerial and Serial conflict

texts:
I have a very simple setup with an Arduino Uno R3 connected to my Windows 7 x64 with Arduino 1.0.1.

I have a RF receiver connected to the Arduino on the DI10 port using the SoftwareSerial library. I am using a AM-RRQ3-433 module. See rfsolutions.co.uk/acatalog/AM_Super-heterodyne_Receiver.html

When I receive a byte from the RF receiver, I am simply writing it to the Serial (so that I can see it on my PC in the serial monitor). Doing so seems to conflict between SoftwareSerial and Serial, since the available() function rapidly increases and thus I have a lot of 0's printed (given no data was actually transmitted, but available() returned 63 - the maximum of the receive buffer).

The Arduino code is as follows:

#include <SoftwareSerial.h>
#define rxPin 10
#define txPin 11

SoftwareSerial rf(rxPin, txPin);
int incomingByte = 0;

void setup() {
  pinMode(rxPin, INPUT);
  Serial.begin(57600);
  rf.begin(2400);
}

void loop() {
  if (rf.available() > 0) {
    incomingByte = rf.read();
    Serial.println(incomingByte, DEC);
  }
}

As a side note, if I remove the pinMode(rxPin, INPUT) line then nothing is ever received (and rf.available() is always 0).


texts: Designing an SMPS circuit on eagle (finding the right transformer and parts) 230VAC to 5VDC

texts:
I'm very new to the world of electrical design. I'm trying to create a SMPS circuit on eagle and am struggling to find the right transformer. I'm currently following this circuit (page 7):
https://www.power.com/sites/default/files/PDFFiles/rdr158.pdf

I'm having trouble finding a transformer like this. The one listed in parts is the have bias windings on opposite side (might be a stupid question). Does this not matter as they are used for control? Also is there anything I should watch out for in terms of the specific capacitors, diodes, and resistors I pick. Any help would be greatly appreciated!


texts: TPS63070 Buck-boost not bucking or boosting correctly

texts:
Can some check my layout since I am using TPS63070 buck-boost regulator and I would like to get 4.7V output at TP12 but I am getting 11.5Vwhich is wrong and don't know why?

Base on the Datasheet R1=R2(Vo/Vref-1)  => R1=34k(4.7/0.8-1)=> R1=165K ,R2=34K

Could someone let me know why?
FB 1.9mv  Vin:4.7 Vout:5.28


texts: Why mosfet doesn't turn off when battery voltage is low?

texts:
I would like to protect the batteries from over discharge, so I want to make a protection ciruit.

I made this:

I want the following: 2x 9V battery in series, so total voltage is 18V. The regulator is 8V, the mosfet is N-channel. If the first battery voltage is greater than 8V, the op-amp output will high, so the N-channel mosfet gate voltage will be high and the mosfet will open.

If the first battery voltage drop below 8V, the op-amp lower the output, so the mosfet is off, and no more power consuption from the battery.

The problem is the following:

The mosfet doesn't turn off when the battery voltage drops below 5V. (in this example only, I didn't find 8V regulator in LTSpice)

The opamp output not 0V else its ~2v output so the mosfet doens't turn off.


texts: Bed-of-nails testing of ethernet signals

texts:
I'm designing a BON testing fixture for a complex board (multiple processors, fpga, memory, etc).
One of the items to test is an external ethernet connection (1Gb). In the current design, the ethernet PHY is internal to the processors SOC. This board is connected to an I/O board that houses the RJ45 connector and magnetics. The two boards are connected via a FFC cable.
We were thinking about exposing the ethernet signals on pads so we can access and test with BON, but we are concerned with piping high speed signals through a nail and wires to the testing board...
Any advice?


texts: Should I twist DC power and ground wires from a power supply?

texts:
Is it beneficial to twist the red/green power/ground wires from a low-voltage (~5V), relatively low current (1 to 5 A) switching, desktop power supply?

This makes my wire bundle on a desk less chaotic, but will it reduce noise or provide any other benefit?  Is there any reason why I should specifically avoid doing this?


texts: What is the diffrences between Bitwise operations in terms of memory consumption, performance?

texts:
If I have two input, for example:
a= 0110
b = 1010
which one is better (in terms of memory consumption, performance):

x = a (XOR) b

x = a (AND) b

x = a (OR) b

And why?


texts:
First time poster and electrical newbie here. First off I just want to thank everyone for helping create such a great and helpful forum!  I've been lurking for years and have learned a lot here!

I have a solenoid valve that is only available in 120VAC/60Hz and for a number of reasons I have to use this exact component in a 220VAC/50Hz application.  I have already spec'ed out a transformer to drop the voltage down from 220VAC to 120VAC.

After reading this post: 50Hz vs 60Hz, I learned that running at 50Hz compared to 60Hz will cause in increase in current - which I'm worried will damage the solenoid coil or lead to premature failure.  I ran through the calculation and spec'ed out a power resistor to put in series with the coil to reduce the current, however this also causes a 20V drop. So with the power resistor, the solenoid will only see 100VAC instead of 120VAC. So now, I'm worried that the lower voltage may prevent the solenoid from actuating properly especially during inrush.  The nominal steady-state current of the coil is 0.5A but peak inrush is 6.5A.

My question is this, is there any component or approach that I can use to limit current during steady-state only without dropping voltage?  Ideally, I would have 120VAC, 0.5A (steady-state) going through the coil while still allowing the peak inrush into the coil of 6.5A.  Outside of investing in a very expensive frequency convertor, is there any other way to achieve what I'm trying to do?  Maybe it's impossible, but you never know unless you try!

Thanks for all the help!

Edit 1: To answer Joren's question below, the spec sheet and the manufacturer say that this solenoid is designed only for 60Hz.


texts: What are these round pads on the bottom of a PCB?

texts:
What are these round pads on the bottom of a PCB marked ScX?

I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.

My best guess is that they're termination pads, but googling it didn't turn up many results so I can't verify that.


texts: Altium how to remove 'ghost' ActiveBoM manufacturer link

texts:
While creating manufacturer links for a part in ActiveBoM I added the wrong part to the entry.

Normally it's straight forward to remove either with right click or from the Create/Edit Manufacturer Links menu. However one DigiKey link always remains and I can't remove the entry. It also doesn't appear in the Create/Edit Manufacturer Links menu.

I've tried adding the manufacturer link again which places an entry in Create/Edit Manufacturer Links menu but after removing the unwanted entry the ghost one still shows up.

Removing the part and placing it again doesn't solve it either. Is Altium linking to the entry on another level which isn't obvious?


texts:
I bought a new ATMEGA328P U with Arduino bootloader incorporated.
I put it in the board but the upload is failing. I don't know which bootloader it has...
Any idea how to solve it?
Should I re-flash the bootloader? Or is it possible to check if it actually has the bootloader and which one?
Thanks
EDIT: I solved it flashing a new bootloader...as I thought it seems they sell chips claiming that they have the bootloader when instead they don't...
Log error below:
    Arduino: 1.8.13 (Windows 10), Board: "Arduino Uno"

Sketch uses 924 bytes (2%) of program storage space. Maximum is 32256 bytes.

Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.

D:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CD:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM3 -b115200 -D -Uflash:w:C:\Users\****\AppData\Local\Temp\arduino_build_613612/Blink.ino.hex:i

avrdude: Version 6.3-20190619

         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/

         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "D:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM3

         Using Programmer              : arduino

         Overriding Baud Rate          : 115200

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xb0

avrdude: stk500_recv(): programmer is not responding

avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xb0

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.


texts: Why does my board start smoking when I put in a higher battery same voltage?

texts:
I just got my custom PCB in the post from PCBWAY.

Plugged in small battery I got with adafruit only 2000mah at 3.7V (PKCELL LP803860)
and showed the LED light to show it was being powered so I thought great its working.

However upon then connecting a battery I ordered off of alibaba.
(EWT LP10048166) same voltage at 3.7V and larger size at 20AH (20000mah)

My JST 2-PH connector starts smoking.

Anyone know why this is happening as I would of thought this of worked out fine with same voltage and larger battery size.

The first part of the board which is dealing with the battery is in simple terms adafruit's 1000C Powerboost which I've added into my design. So its designed to take in 3.7V and then convert that to 5V which is the majority voltage that the components on my board require. The purpose of the PCB in conjunction with a Pi camera v2 module, Compute module 3, 3 ultrasonic sensors & a cree LED is to act as a visual awareness system for the visually impaired so the reason I'm using a 20Ah battery is I require the system have enough power to maintain up to 10 hours of use per day.

Didn't realise the JST connector is rated up to 2 Amps perhaps that might be the reason for some smoking if a 20 amp battery is connected directly to it. Was speaking to a friend of mine and she suggested it could be some of the components on the board might have their resistance change due to the higher amp current. Didn't need to worry about + & - as the connector only allows one way for the pins to meet.

Here's a picture of the larger battery

In Response to Daniel Tork here is the schematic for the affected section of the board.

And here is from board view in Eagle

Followed exactly what MartinF posted in his new edit and that fixed the problem.
Turns out the polarity was reversed on the battery's JST connector. With care managed to pop them out and switch them around. Inserted into the board and the LED on the board went on and no smoke.


texts:
I'm using a pololu step-up voltage regulator (http://www.pololu.com/catalog/product/2117) to go from an unregulated battery (VIN line from an Arduino, powered by a 3.7v LiPo cell) to 12V.

No matter what I do, I can't get a voltage to show across the VOUT. There's definitely a voltage applied to VIN, and it's within spec (above the 2.5V minimum for the regulator). The VOUT line just falls rapidly to 0 when I put a meter on it.

Seems like a simple enough circuit. What could I be doing wrong?

EDIT: The circuit below is for the final application. I tried simply supplying 5V on the VIN line to the regulator, and measuring voltage between VOUT and GND, with the same 0 value.

simulate this circuit – Schematic created using CircuitLab

Here's another way I tried to wire it, with the same effect

simulate this circuit


texts:
A function generator with an internal resistance of $$50\Omega$$ is set to produce a 1kHz square wave with $$20v_{p-p}$$
The duty cycle is 80%. The signal is run through a $$50\Omega$$ resistor.

I need to determine the peak power that is output.

Now,
$$\frac{\Delta t}{T}= 0.8$$
so $$\Delta t=0.8T=0.8\left ( \frac{1}{f} \right )=0.0008s$$

But this is as far as I can go.

A useful hint is appreciated. Thanks in advance.


texts: Magnetic buzzer causes interference in the circuit

texts:
I have the following circuit:

The models in the circuit are:

Buzzer - SMT-0931-S-R
Transistor - ZXTN2018F
Diode - BAT54WS

When the buzzer turns on (beeps every about 500ms) I'm getting serious noise on the 5v voltage - It drops from 5v to about 3v while the PWM is on.

What could cause such an effect? Am I pulling too much current?

What should I change in the design?

Thanks


texts:
I have a project where I will control a 3 or 6 watt UV lamp DC with a microcontroller.

I want to power my lamps with a AC/DC circuit and switch them on and off with a optocoupler, mainly because optocoupler uses very low current and is physically separated from the high voltage circuit. My only worry is that my optocoupler is not going to handle the 3W or 6W lamp.

What optocoupler do you think would do the best job for this project?

I was looking at 4N35 optocoupler and in Its datasheet I was having trouble finding the max power that can go through the transistor of this optocoupler.

Another question that I have is Do I need to use relay istead of optocoupler for dealing with this kind of power ( 3W 6W )?


texts:
If I am connecting ICs to both sides of a led matrix, the ICs need to be able to source and sink enough current to light the LEDs? Or just sink?

Let me explain my question with an example:

In this diagram, I select which row is illuminated on LED1 through IC12 (a shift register). The column is selected through a demux (IC14). The LED matrix current is sunk through IC13, a ULN2803 transistor array.

I know that the ULN2803 (IC13) can sink enough current to light all LEDs. However, IC12 can only source 25mA, and lighting all the leds in a row would take around 100mA. Do I also need to put transistors in the source side of the LED matrix? If not, then what is the recommended setup for what I'm trying to do?

Please bear with me that I'm a beginner. If my question is not clear, please indicate so that I can edit it.


texts: Do I need trivial resistor or not if V/I = zero or almost zero

texts:
As the title says, do I need trivial resistor or not if V/I = zero or almost zero?

For instance:

Assume I'm using 3V buzzer and 2V LED in series with an Arduino 5V pin.

$$R = \frac{(3 + 2 - 5)V}{15mA} = 0 \Omega$$

Should I add a trivial resistance just in case, or not, and why?


texts: Connecting a supercapacitor to a supply with voltage lesser than capacitor's rated voltage

texts:
I am connecting a 3V power supply (CR2032/CR2450 coin cell) to a 1.5F 5.5V rated supercap. Given that the supply voltage is lesser than rated voltage of supercap, chances of any damage become minimal. But my doubt is: whether this setup would increase the quiescent current drawn by supercap and hence decrease the battery capacity.

Theoretically, i suspect it shouldn't make any difference but in a test circuit I observed quiescent current was higher than what was provided in supercap datasheet (when battery and supercap had reached the same voltage).


texts:
i am using the GL850G in gang mode for a circuit without over current protection to extend my available USB ports.
on power up the crystal starts oscillating for around 40ms then stops.
then i using a external USB hub with a GL850G it is working correctly.
my guess would be what it has something to do with the overcurrent protection?
PWREN1# is always high, i also tried to pull-up/pull-down OVCUR1# but PWREN1# is not changing state. any ideas?


texts: Equivalent resistance with complicated net

texts:
I'm completely lost as to how to find the equivalent resistance of this circuit:

It's R6 that's causing me problems. I can't find an expression since a bunch of nodes connect to each other. Anyone got any pointers?


texts:
I am facing some problem with GPRS Project. I am sending request to server through GPRS and receiving responce from the server.
I have used AVR ATmega32 micro controller and SIM900 GSM/GPRS Module from simcom.
I can send HTTP Request Header Successfully to the server, but getting Bad Request response every time.
I have wrote program in AVR Studio 6.2.
here I have attached Response of Server received on GPRS.

  AT
OK
AT+CSMINS?
+CSMINS: 0,1

OK
AT+CREG?
+CREG: 0,1

OK
AT+CGATT?
+CGATT: 1

OK
AT+CIPSHUT
SHUT OK
AT+CIPSTATUS
OK

STATE:IP INITIAL
AT+CIPMUX=0
OK
AT+CSTT="idea gprs"
OK
AT+CIICR
OK
AT+CIFSR
10.112.37.103
AT+CIPSTART= "TCP","198.136.54.34","80"
OK

CONNECT OK
AT+CIPSEND
> GET /httptest.php?data1=value1 HTTP/1.1
 Host: http://exqure.com

SEND OK
HTTP/1.1 400 Bad Request
Date: Thu, 18 Jun 2015 12:19:34 GMT
Server: Apache
Content-Length: 226
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">

                                                              <title>400 Bad Request</title>

Bad Request

Your browser sent a request that this server could not understand.

I want to under stand that where I am going wrong? What is the correct format for HTTP header request?

Here is my Code :

//////////////////////////////////////////////////////////////////////////
//          SEND DATA
//////////////////////////////////////////////////////////////////////////
    LCD_ClearScreen();
    LCD_goto_XY(1,1);
    LCD_Print("Sending DATA");
    _delay_ms(1000);
    LCD_ClearScreen();
    r=SIM300SendDATA(0,"/httptest.php?data1=value1","http://exqure.com");
    if (r==SIM300_FAIL)
    {

    }

int8_t  SIM300SendDATA(uint8_t *Method,char *PATH,char *HOST)
{
    UFlushBuffer();
    //UWriteString(num);
    char cmd[25]="AT+CIPSEND",DataToSend[255];
    //char GET2[255]="";
    //char CRLF[4]="\r\n\r\n";
    //Send Command
    SIM300Cmd(cmd);

    _delay_ms(200);
    uint8_t len = SIM300GPRSWaitForResponse(1000);
    if(len)
    {
        if (!Method)
        {
            sprintf(DataToSend, "GET %s HTTP/1.1\r\n Host: %s\r\n\r\n", PATH, HOST);
        }
        else
        {
            sprintf(DataToSend, "POST %s HTTP/1.1\r\n Host: %s\r\n", PATH,HOST);
        }
    }
    else
    {
        return SIM300_TIMEOUT;
    }

    UWriteString(DataToSend);
    //UWriteString(GET2);
    //UWriteString(CRLF);
    UWriteData(0x1A);

    len=SIM300WaitForResponse(1000);

    if(len==0)
    return SIM300_TIMEOUT;

    sim300_buffer[len-1]='\0';

    if(strncasecmp(sim300_buffer+2,"CMGS:",5)==0)
    {
        UFlushBuffer();

        return SIM300_OK;
    }
    else
    {
        UFlushBuffer();
        return SIM300_FAIL;
    }
}


texts: In a pll loop is it required to have a non-inverting buffer (using op-amp) after the loop filter. Will it help to reduce the lock-in time of the pll in any way?


texts:
As part of a hobbyist construction of an Arduino Uno voltmeter, I used a potential divider of 10K ohms and 470K ohms to step down the voltage to a level which the Arduino Uno analog pin can sense (0-5V). Then, the limit of the permissible detectable voltage would be 0-240V, I want to know if there are any precautions that I should be wary of before implementing this.
Also, for an Arduino Uno Ammeter, I tried extending the above idea, of introducing a small series element of resistance into the path whose current is to be determined. Now, using the above idea, making two voltage measurements (using the same circuitry) on either side of the test resistor, we can calculate the current by

I = (V1/480K) + (V2/480K) + (V1-V2)/r

where r -> test resistance.

Lastly, for an AC Voltmeter, I was thinking to do the usual AC to DC conversion using bridge rectification followed by filtering it with a suitable capacitor, and then followed by stepping down the DC level (as in 1. above) and then feeding it to the Arduino. Could someone guide me as to any yardsticks/limitations of my idea?

Here, too, I would like to know any drawbacks of my idea, or any guidelines I should be following. Also, I am not bent on getting some specific specs, I would also be happy if I could get t detect some range of current as well. I am concerned whether the Arduino has enough resolution to detect such small voltage differences, especially when its (0-1023) corresponds strictly to (0-5V). I would also apologize for any wrong notions and would be glad to be corrected.


texts: Maximum number of pins/lands/balls on an IC package?

texts:
Background
I'm working on a free universal parts library tool. In an effort to optimize memory use and performance, I'm trying to work out the practical maximum number of pins you'd ever see on a part.
Goal
Right now, our limit is set at 4096. I'd like to bring that down substantially, but I don't want to compromise our ability to support high density interconnect components.
The Ask
What is the largest package you've ever used/seen?
Thanks for viewing/responding.


texts: Antenna gain, effective aperture and SNR

texts:
I'm trying to predict the SNR of different antenna. I have a good propagation model to calculate path loss/received power. My question is in the signal-to-noise ratio equation there are terms, Ae, for effective aperture and Gr for the receive antenna's gain.
$$SNR=\frac{P_{REC}G_RA_E}{kTB}$$
My question is when modeling an antenna from the manufacturer's data sheet does the gain they provide already include the effective aperture or does it need to be included explicitly as in the question?

For example, I am interested in the calculating the SNR for a log periodic antenna which the manufacturer says has a gain of 6dBi over some band.

Do I need to modify this by $$A_e=\lambda^2/4\pi$$ Or is that inherently captured in the 6dBi given by the manufacturer?


texts:
I am working on a Project that require something very simple. Is actually so simple that I’m more worried about getting it the most efficient way (less price with better solution).

The project require a signal to turn ON a 24DCV solenoid valve for approximately 3 seconds and then shut it OFF for 15 seconds and then repeat indefinitely until the user shut the system down. I was also thinking on making this time 1 and time 2 adjustable with a potentiometer.

The first solution came to my mind was to use a LM555 but I’m not sure if I can get that big times in-between oscillations and also that difference between ON and OFF.

Another solution I thought about (and I’m sure will work) is to use an Arduino UNO to send the signal to a relay. Then I start to think in the cost of an additional power source for the Arduino (5 to 12 VCD I think) and also remembered that the LM555 doesn’t use 24VCD either.

I’m only a beginner in this electronic stuff but I’m also sure that there is some kind of a timer that does what a need, the problem is that I don’t know where to start looking for.

Thanks for your help and taking the time to read all this.


texts:
I am researching AC vs. DC hi-pot testing.

According to UL 508 and IEEE 421.3, a hi-pot test should, among other things, subject the unit under test to 1000 volts plus twice the rated voltage of the equipment for industrial control equipment rated 51 – 600 volts, for 1 minute at 60 Hz.

However, I have repeatedly seen references to multipliers that permit a manufacturer to hi-pot test a product at some multiple of the above calculation for a shorter or longer amount of time. For example, in this article, the author states, "A typical rule of thumb is 110 to 120% of 2U + 1000 V for 1–2 seconds."

What standard, if any, do these multipliers appear in? Or is this just an easy way to test a preliminary design to see if you're in the neighborhood, and not ever used for final testing?

Related question: I have read that Y caps can be removed for hi-pot tests (since the purpose is to test insulation suitability, not component ratings), but again I have not seen this spelled out in a standard. In which standard, if any, is this called out?


texts:
I have headphones with differential input and impedance of 8 ohms. I need to drive this headphone with some DAC with built in headphone driver (Currently I have chosen ADAU1772). DAC's datasheet mentions that the minimum impedance of headphones it supports is 16 ohms.
Can I increase impedance of my headphones so that I can drive them through this chip? What will happen if I drive this 8 ohm headphone through a chip supporting minimum impedance of 16 Ohms?


texts: Is connecting a generator to the line input of an audio amplifier OK?

texts:
Disclaimer: I'm computer scientist
I have a sinus wave generator (handyscope H3-5) from TiePie but the output power is insufficient for my application. The specification is here. I need at least 60W. I would like to know if it is OK to connect the generator to the input line of an audio amplifier. I need only a signal below 20kHz.
The amplifier is an SMSL SA 98E. I only have a french data sheet. The data sheet states that the input line is 400mV-2V.
I'm not sure what it means.
Also I know that the generator is 50Ohms. Do I have to care about that ?
I plan to buy an RCA<->BNC cable. These are sold for video connections. I think they are 70Ohms. Would it be OK ?


texts: Can a change in magnetic field change the impedance of a coil

texts:
I kept a coil in a linearly increasing magnetic field and calculated the impedance by measuring the induced current and voltage.

When the maximum value of magnetic field was reduced (while keeping the rate of increase of magnetic field with time constant) the impedance increased.

What might be the reason for this?


texts: lighting up a led with 30 millivolt-0.1 volt with joule thief?

texts: I want to light up a led with my hand heat by using a peltier cooler. how can I light up a led with 30 millivolt-0.1 volt with a joule thief? Should I connect more transistor in parallel or give more turns on toroid? I have made a joule thief which can light up a led with 0.7 volt.


texts: Difference between an RFID module and evaluation board?

texts: I get what a eval. board is, but what's a module? But also, why are HF RFIDs cheaper in eval. boards, but UHF RFIDs cheaper in modules? at least on Digikey.com


texts: It is feasible to use DC rather than AC in transmission lines?

texts:
I have read that in Mexico there is a project to build a network of distribution lines (over 1000 km), generators and substations using direct current rather than alternating current. These are rated to provide 3000 MW.

As far as I understand this would require too many substations to compensate for losses (due Joule effect) and the physical size of the lines would be too large.

Isn't this highly inefficient and too expensive?

Requeriments of the project, in spanish


texts: How do I model an LED with SPICE WITHOUT access to a Manufacturer's Datasheet

texts:
Looking to create a model of an LED (RL5-WW15030 from Superbrightleds.com):

https://www.superbrightleds.com/moreinfo/component-leds/5mm-warm-white-led-30-degree-viewing-angle-15000-mcd/263/1190/#/tab/Specifications

There is a Voltage/Current Diagram image on the page, but it is very imprecise, and doesn't show the voltage/current at peak forward current of the LED.

Apparently, the dealer is unable to obtain more precise info or a datasheet from the manufacturer.

I have already looked at the answer to the following post:

How do I model an LED with SPICE?

Many Thanks for ANY suggestions.

Tom


texts: Circuit resistances with activating switches

texts:
Electronics beginner here - My current project is an automotive project whereby I want to recreate a small circuit which uses resistors to feed the car's ECU with information as to what action to take.

It consists of four switches which when pressed change the resistance of the circuit. I have measured the resistances with all five different possible scenarios and the results are as follows

(Default) No switches pressed - 3.96 kohms
SW1 pressed - 658 ohms
SW2 Pressed - 248 ohms
SW3 Pressed - 1477 ohms
SW4 pressed - 0 ohms

My question is how would I in practice wire the circuit to have a resistance of 3.96 kohms when all buttons are depressed yet have the relevant resistance when all the rest are pressed? The car needs to register the default resistance to avoid throwing up an error straight off the bat


texts: Simple circuit to convert a toggle switch turning on into a short pulse

texts:
I need to convert a permanent high signal into a short high pulse.

I've got a design problem where I have a toggle switch that connects to a variable +11V to +17V power source, providing a signal to turn the system power on.  I need the ability for the system microcontroller to override this signal and turn the power back off.  There are lots of ways to achieve this of course, but in this application we need to retro fit some existing systems, so the ideal solution is a simple bit of circuitry that converts a 11V to 17V high level signal into a short high pulse of a few mS.  The signal then needs to go low and stay low until power/ the high input is lost.

I can do it with a low power voltage regulator and PIC10 microcontroller but it seems there should be a much simpler way with say a capacitor and bit of clever transistor trickery?

UPDATE

In response to the idea from vijay ingole and comment from  Chris Johnson below I've come up with this solution:

The series 1uF capacitor C1 lets through much more of the AC pulse from the switch turning on than a 10nF, and the 1uF capacitor to ground C2 stores a decent amount of charge.  Because the lowest input voltage is 11V, even though the voltage seen across C2 is much lower (it peeks at a bit over 5V), its plenty to stay above the transistors 0.7V base threshold for a decent amount of time. The large capacitor values also provide pretty good debouncing of the switch closure.
I think this is a great solution and thank you vijay for the idea.  Please anyone shout if you can see any problem with it but I don't think it breaks any transistor good practice rules.
Here's what it looks like on the scope (yellow=C1+C2 junction, blue=output with 1K pull up added)


texts:
I have a treadmill incline motor that is blowing its circuits fuse every time it starts to run. This is the motor that lifts the treadmill up and down.

The motor is labeled:
Output: 65W
Input 36VDC
Current: 3A
Speed: 3700 RPM
Torque: 1.7KG-CM

I tested the voltage off the board and it's correct per the manual. I have visually inspected the motor, taking the commutator out and it looks OK. I've performed the 3 tests (180 degree resistance, bar to bar resistance and bar to stack) here: http://www.groschopp.com/how-to-check-a-motor-armature/

Everything seems ok.

I did some other "cowboy" tests, which I doubt the validity:

I hooked the bell end (end with brushes, I think it's called bell
end) to the board by itself. It's still an open circuit and sure
enough the fuse stayed fine. No surprise. I left the bell end hooked
up and I put the commutator in, alone without the housing.
With the brushes contacting the commutator the fuse immediately blew when
voltage was applied.

The resistance across for the 180 degree test was 2.5 ohm. That resistance doesn't work with the watts and voltage.

Is this motor bad? Shorted out somewhere?  Or am I missing something?


texts:
I'm working on FSMC protocol of STM32 micro controller The formula for calculate FSMC timing is below, but I have a hard time understanding it.  From ST Application Note

Can someone walk be through the derivation of the values shown for Address Setup time, Address Hold time, and Data Setup time?


texts: Voltage detected across Micro USB cable shielding

texts:
I designed a Keyboard PCB using an ATmega32U4 with the data lines wired up to a Micro-USB B Receptacle. Brand: Molex; part number: 1050170001. The USB ground is directly connected to the Micro-USB B receptacle shielding as shown on the double layer PCB design below. I have a ground pour on the F.Cu side of the PCB represented in red, no ground pour on the B.Cu.

So, the issue here is that my keyboard only operates when using USB cables with dedicated shield wire (basically any cable that passes the continuity test on both ends of the USB metal housing). If I use a USB cable that doesn't pass the continuity test on the USB metal housing, the keyboard doesn't work due to insufficient voltage.

I did some probing with a multi-meter on the cable that doesn't work and here are my results:

PCB's VCC - GND: 1.4V

USB Cable voltage across USB cable metal housing: 3.6V

What I want to find out is:

What is causing this issue? Why is the 5V on the USB cable without a dedicated shield wire splitting across my PCB's Vcc and the shield?
Why does it only work when the USB cable has a dedicated shield wire? (If I short the metal housings of the cable, the keyboard gets detected)
How will this issue affect the board in the long run? Will it fail one day?

Notes:
I do have an ESD protection chip (USBLC6-2SC6) running across the data lines.

Thank you for your time.


texts: Voltage signal significantly drops when BNC cable is connected

texts:
I've built the following photodetecting circuit in photoconductive mode:

For Alligator-BNC RG58 coaxial cable, I use this product (the web site is in Korean, so you might not able to read it.)

When I probe a voltage across a resistor R3 with an oscilloscope while a switch S1 is open, I got the following yellow line:

Blue is the reference signal (HIGH: LED ON, LOW: LED OFF)

If I close the switch, the voltage drops significantly and I got the following:

I suspect that this is because of impedance mismatch.

However, I have no idea to solve the impedance mismatch problem since I have little knowledge about circuit.

In short,

Is this an impedance mismatch problem?
If it is, how can I solve it?
If it is not, what is a problem of it?
And how can I solve it?