texts: How do I make a 74LS170 or 74LS670 register file reliably clock in data on the rising edge?

texts:
I am getting a little desperate here. I thought I could replace a single 4-bit D-flip-flop register 74LS173 with the 4 x 4-bit register file 74LS170 or 74LS670. But the problem is that it is a level triggered latch, not an edge-triggered register. I absolutely rely on the ability of the register to clock the current state of the inputs on the rising edge, because soon hereafter the new state will appear on the data input lines and I do not want to latch that.

So, what I tried were various edge detection circuits. The inverter-and-trick that everyone talks about:

simulate this circuit – Schematic created using CircuitLab
this just didn't work for me, even if I used a chain of 3 or 5 inverters. I doubt anyone actually had done this for 74LS04 and 74LS08 chips. Maybe a generation earlier with the slower original 7404 and 7408 chips it could be done, but it simply doesn't work for me. If it works for anyone else, I'd love to see it demonstrated on YouTube or at least a scope photograph.
But the capacitor trick does work to generate a nice downward pulse, when my !LOAD control line is held low.

simulate this circuit
I have one place where this downward pulse on the rising edge of the clock is generated and then I distribute that to the various 74LS670 register chips where, because I don't have room for 74LS32 quad OR gate chips I just build the OR gate with diode-resistor logic.
The !G_w clock setup works, in slow-motion, by using a 100 pF capacitor, not the 22 pF that I'm showing here in the schematics. But my problem is that once the capacitor C1 is beyond the threshold that it works at all, the pulse appears to be already too long so that the register latches in the changed state of the input after the clock edge, not the state right on the clock edge.
So this is a real bummer. Here I show you on the scope how the signal looks at 650 kHz with the 22 pF:

and this here is what I get if I use the not-and gate trick. It's not the downward spike, I measured the upper line before the inverter, because after the inverter nothing happens at all. At least here we see the slight wiggle as the clock-and-not-clock-gate switches through.

Looking at the data sheet, I try to figure out what the minimum t_W and t_su(D) times should be, but I cannot find these numbers actually stated.

And I did consider that perhaps my downward strobe comes a little after the rising clock edge, so I also derived the CLK' through 2 inverters, but I suppose maybe that doesn't delay the clock enough. So perhaps I need to come up with a way to delay the clock just a tad bit longer to make it come up while the strobe is already solid low. How would I delay the clock just enough?
Is there any other trick? Anyone who has done this? I don't want to drag in a 74LS173 in front of that. There's got to be a way how these '670 can be made to work like normal registers!


texts: Where to find comprehensive motor control learning material?

texts:
I have ARM cortex-M/cortex-A software/hardware development team. My work involves many Linux drivers, BSPs and tuning for ARM hardware.

Recently, one of my friend has started BLDC motor manufacturing business. I would like to make control boards for his motors.

I am from software background, have limited prior knowledge to motors and motor controls, having looked into some Texas Instruments DSPs solutions, and planing to use them. But information for motors and motor control online are very scattered.(youtube, wiki). I would like to learn them systematically. What's a good place/way for me.


texts:
I use an ESP8266-12-E microcontroller as basis for an outdoor sensor measuring and sending temperature over wifi to a server. I soldered a DS18B20 temperature sensor (+resistor) onto the chip. The power is provided by 2AA 1.5V batteries (=3V). When outside temperature is above -4°C/25°F, everything works fine. However, when temperature drops below, the ESP8266 doesn't wake up from deep sleep anymore. The ESP is supposed to work with 3.3V.

My first idea why this fails at low temperatures is that the batteries (alkaline) won't work at those temperature. So I replaced them with Lithium batteries. However, that won't work either.

Now I think the problem is that -although using Lithium batteries- low temperatures causes the batteries to not supply enough voltage for the microcontroller.
Do you think there could be another reason (like faulty soldering points) why that won't work?


texts:
Have a rare case of an iPhone 6 with no display.

When I measure chest_pwr_en it's low at 1.1v should be 1.8v

I've removed the one cap on that line and even removed "chestnut" power display ic u1501 but still the voltage stays at 1.1v

Only other point that line goes to is to u1202 which is the main power management ic in the "AMUX" section which has to be what's pulling the voltage down from 1.8 to 1.1.

Anyone know what this section actually does? Is it sending or receiving the enable line?

Hope the pics are clear they're screenshots from the PDF on my phone


texts: I'm trying to calculate the internal resistance of my rechargeable batteries and haven't got a single battery holder so using I am having to using Banana plugs and Crocodile clips for holding my resistor. Then holding the banana clip on the negative end of my battery and reading the current. But could this be affecting my readings as I've tried different resistors and I'm still out in my calculation first time i got ~1000(with a 10k load) ohm now down to 10 ohm(with 68 ohm load). I have even smaller loads to test with now 1 ohm and 0.1 ohm. But this just popped in to my head as it might be problem. The leads I'm using are what we normally use for connecting our PCBs to the PSU, this is why I thought it could be ignored but maybe not when trying to calculate some thing very accurately.


texts: Altium: how to change document template font

texts:
I'm creating a custom documentation template and my project title always shows up in red italic font:

Is there a way to change the font?

Also  the sheet numbering shows up as "Sheet 1 * of 1" even though my Sheet Parameter is set to "1". Can I change it to show the number only? I verified the number does not contain any asterisks:


texts: KVL not satisfied during simple diode series

texts: A power diode in the reverse biased position is connected in series to a 2.5Mohm resistor.  The voltage source is connected in series to these two components and is set at 10V dc.  The voltage across the diode is 7.5V while the resistor is ~0V.  Where did the "missing" voltage go?


texts:
I'm trying to implement a half-duplex 1Mbps RS485 bus (1 master controlling ~8 motors). After facing occasional communication errors I've invested in a Saleae logic 4.

The RS485 A/B lines probed directly give this output.

(that framing error at the end doesn't seem to hurt, so I'll ignore it for now) and here is the TX line (GND referenced) of a single packet being sent from the master

I am noticing that the slew rates are quite slow (not to mention the ringing). I am using CAT5 cables, total length at the time of this test was ~5 feet, connecting master and 4 slaves.

I am using the SP3485EN transceiver (RX/TX connected directly to microcontroller USART pins). There is a 220 ohm termination resistor (between A and B) that is populated at the master at the moment, and I've tried adding and removing the 220ohm at the other end (on the last slave) but it doesn't seem to make any difference. (I tried to add a schematic but need 10 reputation to post more than 3 images)

Is there any advice on how to improve the slew rates? My guess at the moment is that my communication errors are caused by the digital signals being so non-square. I am using STM32F3 microcontrollers with the USART configured at 50MHz speed.

Are there passives that could be added before the transceiver? After the transceiver? Should I be using a different transceiver?

I just chose to answer to add an image of a scope readout of the TX transmission above, and as everyone suggested, these are very square looking, and the lower frequencies are because of the saleae's sampling. Thanks for the help! I will move on to debugging the firmware.


texts: Single Phase Full Bridge Inverter - I Can't figure out which PWM Control Technique is used

texts:
I have the following Single Phase Full Bridge Inverter and a PWM control method which in my language is called "asymmetric mode". I understand how it works but I can't find any documentation written in English language about exactly this technique.

In my college documentation "PWM with Bipolar Voltage Switching" is called "symmetric mode" while "PWM with Unipolar voltage switching" Technique is named "Doubling the Load Switching Frequency" Technique. For me the "asymmetric mode" looks more like "Multiple Pulse Width Modulation" but the triangular reference has the same dc offset over time (is not shifted down when the square reference is going negative).

http://www.myelectrical2015.com/2017/07/pulse-width-modulation-of-inverter.html

I have searched a lot for an English equivalent of the "asymmetric mode" but I can't find nothing similar with what I have in my documentation. Should I call it "Asymmetric Multiple Pulse With Modulation"?

I hope someone can give me some clues or post some useful links.


texts: Can I use an RC4558 as a voltage follower (buffer) for line level audio?

texts:
I've spent hours reading on buffers, non-inverting amplifiers and inverting amplifiers. I get the concept (though I don't understand all the formulas) and I can't make a simple voltage-follower out of a RC4558 Dual general-purpose op-amp.

Here's what I'm working with:

1V peak-to-peak sine wave @ 1kHz from a frequency generator output (50 ohms)

RC4558
Pin 1 - Output
Pin 2 - Inverting Input
Pin 3 - Non-inverting Input
Pin 4 - Ground
Pin 5 - NC
Pin 6 - NC
Pin 7 - NC
Pin 8 - +12 VDC

Signal directly connected to the Non-inverting Input.
Output feedback is connected to the Inverting Input.

The output wave is 300mV, squarish / pulsating wave.

What am I doing wrong?


texts: I am new to Stepper Motors, I am a mechanical Eng. Have a slight disadvantage with the electronic end. I need a stepper to run one direction, then reverse in sequence. Will a Stepper programmer do this operation //


texts:
Hi I am trying to run a slayer exciter using a MOSFET.

http://www.electroboom.com/wp-content/uploads/2015/01/High-Power-Slayer.jpg

Tells to use these parts

R1 = 2Ω
R2 >= 22kΩ
D2 = 1N4148, or 1N400x (x is a number)
U1 = MIC4452
Q1 = 2SK2542

Except I don't have a MIC4452 to drive the MOSFET.

I think I might be crazy - I have no idea what I am doing. Can a NE555 run a MOSFET?
How would I do that?
Maybe another way without using a gate driver?


texts: I have tried to extend the antenna of my router in order to increase its range. I added a wire few cm long. There was no modification however in the range. The power (-db/m) was the same. Why is that?


texts: Where to put Bootloader Key in Ram, what address is the last ram address?

texts:
I am programming a CDC Bootloader. What I want to do is to run the program, from there write a bootloader key to the ram at a specific address and watchdog reset the MCU. The Bootloader reads exactly the same address and checks if it has the bootloader key in it. If it is the bootloader key it will execute the bootloader protocol, otherwise start the sketch again.

Now the question is: What address to use? Ive heard that a few addresses of the ram pointer are reserved for some peripheral registers. Ive also heard about the stack management in ram. So what would be the best place to put such a magic bootloader key?

As an example on an Arduino Leonardo (32u4) with 2,5kb ram they save it at the 2kb address:
https://github.com/arduino/Arduino/blob/master/hardware/arduino/bootloaders/caterina/Caterina.c#L69

Any suggestions for a 16u2 and 32u2 with 500/1000 byte ram? Or maybe another way to pass the bootloader this information? Can anyone explain me why they used 0x0800 for a 32u4 or was this maybe just a 'random' place? I don't want to conflict with any program as less as possible and dont want to break programs with this kind of ram writing.

Edit:
It is important to find a normally not used ram address since you can revert this bootloader watchdog reset. See this:
https://github.com/arduino/Arduino/blob/master/hardware/arduino/cores/arduino/CDC.cpp#L96-L98


texts: Can I drive nitinol wire with an LED driver?

texts:
I am using 0.010" nitinol shape memory alloy wire (Datasheet) to actuate a lock.  The wire needs to be resistively heated to actuate, and I have empirically measured the cool resistance to be 0.83 Ω (~3").

When using a lab power supply with a constant current limit of 700 mA, the system works wonderfully, but for production we are looking to use a single 12VDC 2A supply for the system.  As this supply is expected to heat the wire and while still powering the control circuitry I need something to limit current.  The device does not have forced cooling or room for large heatsinks, so we do need to stay fairly efficient.

How can I embed a simple ~700 mA supply?  Would a buck converter intended for driving LEDs work?  (1, 2, 3)

These are niche devices – if it is not possible to do this efficiently with a low part count, a <$30 prebuilt module is within budget.


texts:
What is the best way to implement a non blocking delay for a state machine for each state?
So far, the best I found is something like that:

static uint8_t state = STATE_ONE;
if (state == STATE_ONE)
{
   static uint64_t time_value_ms = (uint64_t)0;
   if (time_value_ms == (uint64_t)0)
   {
      time_value_ms = system_get_ms() + delay_ms;
   }
   else
   {
      if (system_get_ms() > time_value_ms)
      {
         time_value_ms = (uint64_t)0;
         state = STATE_TWO;
      }
   }
}
else if (state == STATE_TWO)
{
       static uint64_t time_value_ms = (uint64_t)0;
       if (time_value_ms == (uint64_t)0)
       {
          time_value_ms = system_get_ms() + delay_ms;
       }
       else
       {
          if (system_get_ms() > time_value_ms)
          {
             time_value_ms = (uint64_t)0;
             state = STATE_ONE;
          }
       }
}
.
.
.
else
{
   return;
}

But the problem in the code above is that when the state changes, the time_value_ms variable has to be set at 0 in order to be available to count a delay again when the state return in the STATE_ONE afterwards.

Therefore when you need a non blocking delay in every state in a big state machine with too many states (10 states for example) the code becomes complex with very bad readability.

The delay is used as timeout timer for deadlock or an event timer.


texts: What battery should i use for a bluetooth boombox?

texts: I've been searching for 3 days now to find an answer to this problem. I have a TDA7492p amplifier(8v-24v input) and I am looking for a battery that is safe to be charged while using the amplifier. The VRLA 12v 7Ah seems perfect but they say it's very dangerous and hard to recharge(needs very exact volts and amps). Another solution would be laptop cells, but they seem hard and expensive to recharge. Theoretically both are designed to charge while being used but I don't know what is the best way. Do I need a special circuit/device for that? And how should I power the boom box to also charge and use it?


texts:
Further to the SEPIC design I asked about in LTSpice SEPIC simulation current spikes, I have a new problem. The output voltage is OK and the inductor current waveform looks much better but the inductor current has a low frequency ringing component. (Ringing might not be quite the right term?).

The blue trace is the inductor current and the red trace is the load current toggling between 100mA and 1 Amp.

The detailed waveform of the inductor current looks OK I think.

I have tried adjusting just about every value (inductors, C4, C6 & R8) without success.

The large ringing at power on is also a worry.

I am not sure how to tune the slope compensation components (C6 R8).  What should I be looking at?


texts: How to display character on multiplexed seven segment?

texts:
I am designing a system which I want to display a message on a seven segment display.

I have the source code for displaying a number but how to display a character ??

`void UpdateDisplay(void)
{
     unsigned int SendVal;
     unsigned char Digit;
     if (flg2ms)
     {
        SEGMENT++;
        if (SEGMENT > 3) SEGMENT = 1;
        C1 = 0; C2 = 0; C3 = 0;
        switch (SEGMENT)
        {
               case 1:
                    Digit = (unsigned char) (Voltage_INT / 100);
                    break;
               case 2:
                    Digit = (unsigned char) ((Voltage_INT / 10) % 10);
                    break;
               case 3:
                    Digit = (unsigned char) (Voltage_INT % 10);
                    break;
        }
        SendVal = DriveSegment[Digit] & 0x7F; // Make bit 7 zero
        PORTB = SendVal;
        switch (SEGMENT)
        {
               case 1:
                    C1 = 1;
                    break;
               case 2:
                    C2 = 1;
                    break;
               case 3:
                    C3 = 1;
                    break;
        }
        flg2ms = 0;              // Clear flag
     }
}`


texts: Controlling Solenoids using Relay vs Transistor

texts:
In several examples, relays were used to control solenoids, others use the transistor. In my question, I'm looking at controlling 24VDC solenoid pneumatic valves.

What are the advantages and disadvantages of using relay boards vs transistors with muultiple outputs?


texts:
I'm using the following tutorial http://langster1980.blogspot.co.at/2015/08/driving-vga-port-using-elbert-v2-and_7.html
To generate a VGA signal. I'm beginner in FPGA and VHDL. I would like to create a framebuffer to render to it then read it back. I would like also a function to setpixel at specified position. I don't know what to modify in code, to generate that pixel at specified position.

Would someone recommend books, or anything to complete that project ? That is not a homework or anything, it's a project for fun!.


texts: Looking for a micro slide switch On/Off guard that will work on a vintage RC transmitter

texts:
I have a very old New in the Box RC transmitter but some of the plastic items are a bit brittle.

Any ideas?


texts: Query on capacitor, one large or more in parallel

texts:
There is a power line, I need to put decap of 1 \$\mu\$F.
Is it better to use a single 1 \$\mu\$F or three 300 nF capacitors?
Is there any advantage of using three 300nF capacitors?
There is no space or price constraint


texts: How do phosporus atoms affect the conductivity of a doped semiconductor?

texts: Free electrons come from electrons in the Phosphorus atom when it excites to the conduction band. This leave an ion, what effect does this positive ion have on the flow of electrons?


texts:
I want my layout will include female headers to connect CP2102 MICRO USB to UART TTL Module 6Pin so I could just 'stick' it to my PCB while uploading the code. The 5V for the ESP will be supply from external source during operation.

The thing is the CP2102 has the following pins: 5V, 3.3V, GND, TX, RX, DTR:

I looked in the schematic of ESP32, micro USB 5V&USB-UART section and I saw that for upload the code properly I need RTS pin from CP2102, which is not accessible:

So it's seems that there is a missing pin out (RTS) for uploading the code. I didn't find any module for micro USB&UART that contain all the desired pins.

Is there any solution for it? Or should I implement the micro USB 5V&USB-UART section on my layout?

Thanks.

Update:

So I got the board and the USB to UART section looks like:

I tried to upload a sketch to the board and got the following message:

Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____

I pushed the BOOT push-button as always do with ESP32 and nothing happen! I also measured voltages across IO0: 3.3v and 0V when I push the button.

Finally I got the message:

A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header
A fatal error occurred: Failed to connect to ESP32: Timed out waiting for packet header

My design looks the same as the reference suggest, but still I failed in uploading a sketch.


texts: Bridging 3G/LTE from cellphone to IOT device

texts: I have an IOT device that needs to function as an access point, even without close by wifi signals, and then publish a wifi network. I know that I can achieve this with a 3G/LTE/GSM module but given this particular IOT device is essentially a wearable (housed in a backpack so weight isn't chief of my concerns) I was hoping there would be a way to bridge the connection of my 3g device over bluetooth or another protocol, connecting my device to the internet that way instead of giving it its own module and sim card.


texts:
I am trying to find out specifications of a thermister on which "10P" is printed. Its resistance at room temp. is 18 Ohms when the circuit is power off. How can I find out its specifications?

This is the approx. circuit where this PTC thermister is used. What is the purpose of using a thermister in this circuit?


texts:
I am trying to do a project which requires me to control about 100 LEDs individually. I want to make a clock that has 6 columns of 10 LEDs that as the number in the time goes up, more LEDs will turn on. I would prefer just doing it with wires connected directly to the lights. I have looked into using an arduino, but they don’t have enough ports. Is there any way to do this? Maybe using USB?

Thanks,
djtravz


texts: What is this flat pin battery connector on my quadrocopter called?

texts:
Has somebody seen this type of connector before and can tell me what it is called?

It has flat pins, a 2 mm pitch, and "wings" on the side to prevent reversing it. Copious amounts of searching the internet only told my that the Syma X5C obviously features the same type of connector but with only two pins, but not the name of this type of connector.

A bit of context: I've got a new quadrocopter from UDI R/C, Model "Discovery FPV" or "U818FPV". I'd like to upgrade the battery, to a larger one, but that is difficult to do without knowing what the connector on the drone is called. Of course I could replace the connectors on the drone and the original battery and the charger, but I'd rather not.


texts: Passive Attenuator + Voltage divider to level shift input signal without violating KCL

texts: I have a 7vpp voltage input signal centered at 0V, so +/-3.5V. I wish to turn this into a 2Vpp signal centered at 1.65V, so 0.65V to 2.65V. To start with I have a passive attenuator to give an attenuation of 1/3.5, changing my +/-3.5V signal to +/-1V signal. My plan is to then add a level shift stage with an op amp to shift +1.65V, this will move +/-1V to 0.65 to 2.65 range. My problem is that my original circuit design had the passive attenuator, which is just a voltage divider, feed into another voltage divider with an offset value of +1.65V for the level shift, but I went over it with my professor and he showed me how it violates Kirchhoff's Current Law since the current at that node will not be 0. So I am wondering if I can maybe use an op amp in between the passive attenuator and the level shift voltage divider like in my attached picture. My VDD is 3.3V also.  After the level shift the 0.65V - 2.65V signal will be fed into a differential op amp to convert from single ended to differential.


texts: SIM card used as secure storage with AVR

texts:
I would like to use a regular SIM card to store an AES key to be used by an AVR micro-controller. I think that a SIM is secure enough (isn't it?).

My problem is that I can find nothing about interfacing a SIM card with Arduino (for prototyping) as secure storage and not as GSM. Do I have to flash a custom OS to the SIM card? Or should I just buy an ordinary smart card and just cut it in SIM card dimensions?


texts: Finding load resistance to achieve max power transfer

texts:
1) So, to find Thenevin equivalent resistance, R-Th,
   I disconnect R_L and disable the voltage source
   by shorting it out.

2) Now I just look back into the network and
   calculate R_Th, which I know R_L will
   have to equal to since max. power transfer
   is achieved when R_L == R_Th.

3) Now this is where I'm having trouble.  I see:

   [(2k + 2k) || 2k] + 2k
   (4k || 2k) + 2k
   8/6k + 2k
   10/3 k = 3.333k ohms

   But my book says it's:

   [(2k || 2k) + 2k ] || 2k
   (1k + 2k) || 2k
   3k || 2k
   6/5 k = 1.2k ohms

So, can someone explain to me why my equivalent resistance is incorrect?  Starting at the right I see 2k in series with 2k, making 4k.  Now, I see that 4k in parallel with the 2k in the middle branch, making 4/3k.  And now since I'm left with a single loop, I see the 4/3k and remaining 2k (top left) in series, as they would carry the same current.


texts:
I am about to develop a portable device to be interfaced with a computer (so, consumer electronics). I only have experiences with Microchip and Texas Instruments and I would like to have some hint to choose the right MCU.

Key requirements should be low power (it's a portable device), 16 bit, RAM>10KB, hw multiplier, large program memory (128KB) and available in development kit form or something.

Is there any with the possibility of interfacing a on-chip Flash memory (such as the ones in USB keys)? Otherwise, I'll just use an SD card.

Very important, is there any chance I could find one with 3Mbps (3250000bps) UART? (need to interface with a Bluetooth module for high speed communication).

What kind of MCU do you think would be a nice compromise?

Thank you for your help,


texts: Whence this difference in supply current?

texts:
When I need a MAX809 I prefer the OnSemi part over those from Maxim or NXP because the former has a much lower supply current. But I was looking at the NXP datasheet again recently, and I noticed that there's a big difference in supply current depending on package:

  SOT-23
  Typical: 24\$\mu\$A
  Maximum: 60\$\mu\$A
  SC-70
  Typical: 24\$\mu\$A
  Maximum: 35\$\mu\$A

  Compare with the OnSemi (both packages)
  Typical: 0.8\$\mu\$A
  Maximum: 1.8\$\mu\$A

So for the SOT-23 that's nearly double the SC-70's value. I realize that a SOT-23 can dissipate a bit more power than an SC-70, but these values are under the same temperature conditions. The Maxim datasheet gives exactly the same figures, while OnSemi doesn't differentiate between packages.
How can this difference be explained?


texts: Enable grid-tied solar array power output during grid outage

texts:
I am getting close to investing in a micro-inverter (Enphase M250) based grid-tie solar array for my home, but am concerned I won't be able to use the solar power during grid outages.  I found a similar post here that hints towards spoofing the solar array to power on.

First, is this actually possible?  I understand I would need to disconnect from the grid before enabling the solar array and would turn all but the necessary circuits off at the panel.

In my mind, I'm thinking a pure sine wave split phase inverter, like this, hooked to my truck battery and fed in through my 220v, 50A welding outlet would enable the micro-inverters to start producing power again.  I would then charge the battery with a float charger.  Is it that simple?

Second, if that would work in theory, how much load would be on the inverter?  Let's say I am producing 10kW from the solar system and have a load of 7kW.  I'd like to think the 4kW inverter wouldn't have any load on it, but I have no idea.  I'm concerned it would try to pull from both (or possibly only the inverter?) and fry the split phase inverter or destroy my truck battery.

Third, if I am producing 10kW from the solar array and only using 7kw, is that going to be an issue?  Normally the grid would consume the remaining power.

Lastly, I do realize there are plenty of options, such as a battery backup system, or a hybrid inverter, or a string-array with a SunnyBoy inverter, which has a usable outlet during grid outtage.  I'd like to enable the solar array with very little extra cost then what I'm already prepared for and without modifying the system, since it's all under warranty unless I modify it (as in tapping into the DC lines from the panels).  Also, a very similar question was asked here, but I'm hoping to answer the technical aspects of 'is it possible', not as much of the 'is it advisable' question mostly addressed in other post.

EDIT: I also found a document from enphase about AC coupling their micro-inverters here, but it doesn't spell out specifics.  I'm convinced it's possible...

EDIT: I've contacted my installer, who agrees that it should be possible, and is contacting the manufacturer for more details.  I still have my fingers crossed.

FINAL EDIT: For anyone else looking for a similar setup, I received a response from my installer.  The Enphase microinverters absolutely will work with any "clean" power source.  As the accepted answer points out, the microinverters are already designed for this very purpose.  They don't care what the source is, they'll match it as long as it's a stable power source.  My installer did say if I don't use a clean power source and fry the microinverters, they won't be covered under warranty, so be careful of the selected power source.


texts: How can I connect a thin relay to a 220V wire?

texts:
Im almost an absolute beginner in the electrical field. I have bought a relay and wires (for a 60W light), however once unpacked I see that the relay is very thin.

I have tried to use a crocodile clamp but it seems too big. I have a breadboard but Im afraid the current will be too much (it is a 60W light, not an LED)

I think that soldering them together will be too weak. Any idea ?

EDIT : 220VAV / 2A for the relay, this is for a small light (220V / 60W)


texts:
According to the solution, it says it's because the phase shift is wrong. The gain network is non-inverting, so I assume that means that the LC feedback network was not 0 degrees for that particular frequency.

So I tried to work it out by hand but I am stuck here. Is my knowledge that the LC feedback not being 0 degrees for f = 1/root(2LC) the reason why it doesn't work? If so, what is the shift exactly, and how can I calculate the phase shift from the equations below


texts: Altium net has only one pin in hierarchical design despite port connection

texts:
I am working on a multi channel hierarchical design in Altium 19 and getting an error 'net has only one pin' for all signals contained in buses routed between two sheets.

Below is my top level schematic. I've circled the bus SENSE as an example to trace.

In the MCU sheet below, I connect the SENSE[1..17] port to a bus with label 'SENSE[1..17]', then break out individual signals in the bus to pins on the MCU.

In the Switches sheet, I have duplicated sheets for two different types of switches, and I group their SENSE nets together into one large bus going to a port as shown below.

I've seen it suggested in other posts that net identifier scope set to 'global' will fix the issue, however I don't see why the error is occurring at all since I've followed the rules and used ports to make connections between sheets.

Below are the errors, for reference:


texts: doubt on application of stability criteria

texts:
I have only seen systems with this transfer function treated in stability criteria with this general form:$$\frac{KG(s)}{1\pm KG(s)}$$ so the $$\lvert H(s)\rvert =1$$
is it possible to apply criteria with H(s) distinct of 1? or must do some transformation before? thanks.


texts: What is the reason my ULN2003A overheats?

texts:
I'm driving some 12v fan motors from a microcontroller using ULN2003A Darlington array. Both total wattage and per-channel wattage are way below ULN2003a limits. Still, I found that when PWM duty cycle is below 20%, ULN2003a starts to get really hot (can't touch with a finger). At higher PWM duty cycle temperature is much lower.

Update: Fans draw around 0.2A each, and the PWM frequency is 32 kHz currently. The capacitors are there to reduce the audible noise (I was using lower PWM frequency initially).

Am I correct in suspecting that the heat source is the flyback diodes, and not the darlingtons?

I'm thinking of adding some external flyback diodes across the motor coil. Is this the corect thing to do in this situation? I have some 1N5818DICT on hand (Schottky diode 30V 1A, Recovery < 500ns). Will such diode be ok, or I I need something special?


texts: Do 12V MR16 LED bulbs contain active components?

texts:
I was wondering if, unlike GU10 (230V AC) LEDs, GU5.3/MR16 (12V DC) LED bulbs typically contain any active voltage regulating components?

Or do they directly connect the LEDs to the 12V line so there is no chance for harmonics/flicker/etc. (aside from the 12V supply itself of course)?


texts: Solar Panel Not Charging Batteries in Series

texts:
I live in a remote part of Tanzania with no mains electricity. We have had solar power for some time, but on purchasing a new inverter, battery and extra solar panels have run into problems.

The problem can be simply stated.

We have two N200 lead acid batteries both yielding 12-13V each. Connected in series we get 25v from the system.

The inverter (Shiv Solar Comercial UPS 2000-24V) requires that the batteries be connected in series. If they are connected in parallel the inverter quickly triggers a ‘low battery warning’.

But the batteries will not charge when connected in series.

Each will charge on its own. So there does not appear to be a problem with any of the connections.

Moreover both will charge together when connected in parallel.

Nor does it make any difference which way around we connect the batteries in series.

When I say that they do not charge I mean that the charging sign on the controller indicates that the batteries are not charging. Also the Amp level reads ‘0’ for both the solar panels and the batteries. The volts show a positive reading (batteries on 25, solar panels vary according to the sunlight).

We know that single batteries charge on their own because the charging sign on the charge controller indicates that they are and the ampage is positive both for the panels and the battery (varying according to the sunlight).

What would cause this problem?


texts:
I have to route this signal for a distance of ~70mm† through a dense (mostly digital) 2-sided board.
The signal is generated externally and I have no control over its shape, it's basically a pulse train at around 30 Hz, where each pulse is 10µs long, 200V in amplitude, and the front is particularly strong, it attains the 200V within a µs.

This signal is either measured via a high-value resistive divider, or shorted to ground through a relay:

simulate this circuit – Schematic created using CircuitLab

The current when shorted is ~1.5A. The signal is at ground potential in the other 99.97% of the time, and I'm taking care to switch the relay during that quiet times, to prevent sparking.

The red-shaded part is what worries me (btw I don't actually have a fuse, I inserted it so I could separate the nets, otherwise Circuit Lab paints all in red).

How can I route this signal so that it doesn't cause excessive EMI?

On the PCB, coplanar waveguide style (sandwiched with GND in every direction),
On the PCB, just as far away from other signals as possible,
On a separate wire (probably shielded), physically separated away from the board,
Something else?

EDIT:
† - shortening this distance is not very feasible.


texts:
I am currently working on some improvements on my motorbike, and one of them requires something I have never done before.

I am adding 2 12v LED strips (well, they're built in a piece I am mounting, but that doesn't change anything for the electronics), with the idea that they will normally go on when I power the motorbike and serve as DRL. But I want them to also blink as warning lights when I turn on a switch when I am lane splitting. This of course means that when they blink, the continuous power should be turned off.

So the idea is to make 2 circuits with the same LED strips, one that simply runs the power through it, the other one with a blinking relay in line, and have a relay make the switch from the one to the other.
Now I have never worked with a relay before. I think I grasp the concept, there is one circuit (NC) that is closed when the relay is not powered (that would be my DRL circuit) and one circuit (NO) that will close when the relay is powered.
As I understand, the COM is basically the power "input" that wil be directed either towards NC or towards NO depending on the state of the relay.
The DC+ and DC- seem rather transparent as well although I don't know how things would work inside the relay.

Now the big question: is the IN the key contact that will determine whether the relay is powered or not?

And in my case, is this how I should wire the whole thing?


texts: I have noticed that some buck boost converters say "led driver", some have step down/up control and what looks like a display voltameter and ammeter, they are adjustable to 5 Amps/32v. Obviously these devices are not stand-alone LED drivers as they need a constant current, so how are boost/step down with adjustable control incorporated into powering a high powered LED?. Do they act as the driver when powered by a power supply?, or can they be used alongside a constant current or constant voltage driver?.


texts:
So I am designing a power supply, got everything calculated, and decided to simulate it for a second to see if the smoothing caps keep the voltage above the regulator limit at max current draw. What I noticed, that the current through the transformer peaks to nearly 2.5 amps when the cap is charging in the transformer.

Will it destroy my 300mA transformer?


texts: FPGA Frequency divider with linear regulation

texts:
I'm currently developing an FPGA gateware requiring a regulated frequency divider and I wonder if there is any tricky way to get a linear output frequency regulation?

What I mean is that if I use a simple preloaded counter I get a f~1/x relevance, where x is a counter initial value. As I need to regulate frequency in a relatively wide range (say 0.5Hz-10kHz) I'd like it to be a linear function of some argument (of course, not necessarily a counter value-it can be something more complex ;-) ).


texts:
I am looking to use a Texas Instruments MC33063 Buck/Boost regulator. I have never used a switching regulator before so this may be a conceptual issue.
My input voltage will probably be anywhere from 6 to 12V and I would like to use the regulator to buck down to 5V. However, I get confused when I read through the data sheet. Here's the layout for a step down from the sheet:

So the data sheet shows that if I were to input 25V, given this setup, I can get 5V. However what about 6 to 12V for a Vin?
Also, the optional filter is shown that \$V_{out} = 1.25(1 + R_2/R_1)\$. Is this independent of the input voltage? If so, what is the advantages of varying input voltages or is it simply flexibility?
Here's the link to the datasheet:
http://www.ti.com/lit/ds/symlink/mc33063a.pdf


texts: Collision detection on ethernet coaxial cable

texts:
On ethernet coaxial cable, how collision is detected by the sending device? I was told by someone that it is related to high electrical current and the difference between the sent frame and the received frame.

However, I am unable to understand at all of either two. For the high electrical current, I don't understand at all. For the difference between the sent frame and the received frame, will the sending device receive back the frame it has sent? If yes, then how?


texts:
I am currently working on a direction finder project for rf signals. I am attempting to use a phase detector chip to compare phases and calculate the direction. The main problem I am experiencing atm is getting the signals into the chip. I was hoping to find a reciever chip for the 433.75Mhz range. However all the ones I found included a demodulator which would mean the loss of the carrier signal (needed to compare phases). Has anyone come across an IC that can recieve the signal, amplify and filter it without demodulating it?

My other thought was that a using two basic rf reciever (not sure if it is fm or am) with an audio would work as the phase detector chip can work at low frequencies. I am not sure this is correct though as would the rf reciever mix with crystal meaning that the two signals would end up being forced into the same phase?

Many Thanks


texts: Why do CPU's typically connect to only one bus?

texts:
I found a motherboard architecture here:

This looks to be the typical layout of motherboards. EDIT: Well, apparently it's not so typical anymore.

Why does the CPU connect to only 1 bus? That front-side bus looks like a major bottleneck. Wouldn't it be better to give 2 or 3 buses straight into the CPU?

I imagine one bus for the RAM, one for graphics card, and one for some kind of bridge to the harddrive, usb ports, and everything else. The reason I split it up this way is because harddrive data rates are slow compared to memory.

Is there something very hard about doing it this way? I don't see how cost could come into it, because the existing diagrams already have no less than seven buses. In fact, by using more direct buses, we could reduce the total number of buses and maybe even one of the bridges.

So anything wrong with this? Is there a major disadvantage somewhere? The only thing I can think of is perhaps more complexity in the CPU and kernel, which makes me think this bottleneck bus architecture is how it was done in the old days when things were less sophisticated, and the design stays the same for standardization.

EDIT: I forgot to mention the Watchdog Monitor. I know I've seen it in some diagrams. Presumably a bottleneck bus would make it easier for the watchdog to monitor everything. Could that have something to do with it?


texts:
I went to the store and asked for a FTDI cable however, I need a bit of assistance, apparently I didn't properly do my homework before shopping and I ended up with upper pic.

I need an FTDI cable to configure my Xbee modules so I could transmit wireless voice, however, upon double checking after buying it, I found out that the FTDI cable is supposed to have 6 pins not 4, so I'm getting confused. Also the cable I bought does not have a label saying it's the CA 42, so I end up with two questions that I haven't been able to answer using Google:

Which is the standard FTDI cable, 4 or 6 pin?
Could I still use the 4 pin cable to configure my Xbees?
I opened the plastic case to see the circuit, I can see the missing RTS CTS pins, however I'm still wondering if I should solder them and use them.


texts:
I have been trying to make a watch circuit, but have ran into the issue of how to setup the crystal. I believe it is the crystal that is the problem because when I messed with the crystal contacts the microcontroller starting completing the blink program I had put in it. It made me believe that the crystal was not oscillating and I don't know why. I am totally confused on how to fix it because all the circuits look like they just have the resonator and the capacitors. Thanks in advance!

Wiring for the Crystal


texts:
Working on a PCB layout and just did some ground plane pour.

From working with tube amplifier designs I know that a good star shaped ground design helps a lot to keep hum out of the circuit. Ground loops should be avoided at all costs.

Now here is one of the ground planes of a design I'm working on. Only the ground signal is shown, other signals are hidden.

If you look closely you'll see that there is in fact a huge ground loop (shown in yellow) along with some smaller ones (not marked):

I could break the ground pour where impedance matters least and strategically place a bunch of vias to the second ground layer to get a nice star shaped ground design.

On the other hand it's very tempting to just keep the copper pour as it is and sprinkle a bunch of vias to lower the overall impedance.

What is the better way to deal with the loops? Or are such loops okay in practice?

And some additional info: The circuit itself is pure analog and contains almost entirely low impedance signals below 1kOhm. Highest signal frequency is around 10Mhz. I have very fast rise/fall times in the range of 1000V/µS though.

The circuit will likely operate in the vicinity of a 13.56Mhz RFID reader, so I expect quite a bit of RF noise.

Screenshot of the bottom layer (ground pour only):


texts: Finding value of feedback capacitor in a photodiode amplifier

texts:
I am tasked with the objective to design a photoelectric sensor. Being very weak on amplifiers & control theory, I am working on the basics of op-amps. Following this reference design by TI, I learned that feedback capacitors are important for stability of photodiode amplifiers.

However, the calculation of capacitor value is ambiguous (Section 2.3):

  The feedback capacitor, in combination with the feedback resistor,
  forms a pole in the frequency response of the amplifier:

  =1/(211)(4)

  Above this pole frequency, the amplification of the circuit will
  decline. The maximum feedback capacitor value can be determined from
  the feedback resistor value and the desired bandwidth:

So it uses the intended bandwidth to calculate the max. value of capacitor, but what about the minimum value? This calculation doesn't tell me if the calculated value is enough for stability. What is the method of calculating minimum feedback capacitor for stability?


texts:
I have a PWM bridge driving a higher than 1k load from 200V supply. The simplified, equivalent schematic is this:

The drivers I'm using are slow turn-on/fast turn-off and, in the schematic, it's a 50% duty-rati.,The parasitics modeled here also involve some capacitance across the filtering inductor. These will cause some spikes, sure, but they pale compared to the switching problem and, while I can get away with 100-200mA peak, what I have here is a bit scary:

The driving, as seen here, is a much nicer version to what will be in reality. The problem is that the mid-point voltage, V(mid), doesn't fall with the ending of the commanding pulse, only with the rising of the complementary pulse, which makes it overlap a bit and cause a spike, in addition to the inevitable parasitic. Here's a zoomed-in portion:

You can see that the upper drive, V(gh,mid), is turned off fast and has plenty of dead-time, while V(mid) keeps on going until V(gl) starts.

I know there are circuits trying to circumvent the parasitic capacity, but they only affect the response (slow zero as opposed to a notch), because the current as seen from the bridge is still there, which is what is the problem.

My question(s): is there any way of making V(mid) fall with the end of the command pulse, actually having a dead-time in there? Another winding with a forced current, maybe? Some clever snubbers? Anything? Or is this "unobtainium"?

Update: This is a close-up with Id(M3):

The dead-time is 25n but the rise time is imposed to be 25n, too. Tfall=1n but, apparently it doesn't affect the response as I'd want. Increasing the dead-time to 50n (keeping tr) results in this:


texts:
I'm entirely new to electrical engineering. This is for a hardware/software project I have in mind, where I need electricity without having to plug the device into a power source.

My intention is to make a bluetooth "controlled" door lock. For that I need to be able to charge a tiny battery to at least a level of 2V (the minimum voltage the device needs to run) to power a small bluetooth 4.0 device.

The device I intend to power is the ConnectBlue OLP425.

Is there any way you can generate electricity by moving something up/down or forward/backward?


texts: Activating BJT with an isolated current source

texts:
simulate this circuit – Schematic created using CircuitLab
This circuit represents a very elementary variation of a BJT as an inverter amplifier, where ON/OFF is the input and Vo is the inverse amplified output. However, the presence of Q1 means the grounds of the two batteries are not directly tied together.
Based on my understanding of the behavior of a BJT, it shouldn't matter that the two batteries are pseudo-isolated like this. But I'm not 100% confident it doesn't make some difference. What I keep getting tripped up on is the B-E current flow doesn't return to the same ground as the C-E current flow. Does that actually matter in this circuit?
For context: BAT1 and Q1 are part of a black box device I need to interface with. The device was originally designed to energize an external burn wire, so it just needed to provide a lot of current for a short period of time. Only the + side of the battery and the collector of Q1 are exposed as connection points outside of the device. For my project, there's no burn wire, but I need to detect when the device would have energized the burn wire. I plan to use an optoisolator in my real hardware, so this question is purely academic.


texts: Zero Cross TRIAC circuit for regulator fails on voltage spike

texts:
I am using a ZC TRIAC circuit to switch and regulate an electric appliance e.g. a table fan, a electric drill etc.

I must confirm that proper SNUBBER circuit is used and everything works fine. I have created a switch board with switch and regulate buttons with the triac underneath , controlled by an ARDUINO. I just have to plug it in a socket of a switch board on the wall and plug in the appliance in the socket in my triac switch board and everything works fine.

Now the problem starts when an appliance in my wall switch board ( e.g. tubelight ) is turned off ( no problem while turning on ). Whenever another appliance is turned off, the ZC circuit restarts the ARDUINO. If the ZC circuit is taken out, everything is ok.

So the problem is definitely with the ZC circuit, but I have no clue what the problem is. Any help will be greatly appreciated


texts:
I just purchased an RV-3028-C7 RTC module and tried to get it working. I2C seems to work, so I can read some registers:
Device ID = 0x33
Status    = 0x81
clk_out   = 0xc0
eepwe   = 0xff
user_ram = 0x00
seconds = 0x00
seconds = 0x00
seconds = 0x00
seconds = 0x00

The behavior seems to differ from what the datasheet suggests for a part in factory configuration. The CLKOUT pin is not toggling (even though clk_out has the correct value, 0xc0), EEPROM password protection is on (eepwe==0xff and I can't write user RAM, for instance), and SECONDS is stuck at 0. In other words, it's not in a usable configuration.
I also noticed that Status.EEbusy is set. According to the datasheet, hardware should automatically clear this bit within 66ms after POR, when it completes an EEPROM refresh. Yet the bit is still set after 12 hours. This seems like a major problem, since the datasheet mentions many functions that require the POR EEPROM refresh be completed before they can start working properly. (I don't know if SECONDS and CLKOUT are included in that category, but it seems plausible.)
I have 3.3V on the primary supply and 2.7V (via battery) on the backup supply. And I have a separate bypass cap on each supply as recommended in the manual. I have no floating signals (EVI=nINT=GND). I tried power cycling many times, with both possible bringup orders. Always same result.
This part is decently stocked, unlike many other RTC modules out there. So I assumed it was being used in products already. Am I doing something wrong?


texts: How to check the PCB design for manufacturing(DFM)

texts: I am interest in PCB design. As to design for manufacturing, can somebody share some guidelines or links to learn? Can the PB fab house be help with this job?


texts: What do you call four 'connected' potentiometers?

texts: I know we have mono potentiometers and stereo potentiometers, when there are two potentiometers connected mechanically. What do you call a potentiometer consisting of four mechanically connected potentiometers? Do we have a name for it?


texts: ON/OFF pulses to rear brake light of sportbike

texts:
New member here.  I am a mechanical engineer by education and training, but electronics has been a hobby of mine since childhood.  I have a little project that I have been thinking of making, but am having some trouble with the circuit design.  In a nutshell, here is what I am envisioning:

Objective: Create an electronic solution to improve following driver's awareness that motorcycle is braking.

Background: I know that there are some taillights on the market that can already deliver brake light pulses, but I want to make my own controller since the bike already has an aftermarket LED integrated taillight (an integrated tail simply means that the running light, brake light, and turn signal functions are contained in one enclosure - people usually install these over the OEM setup because they look nicer on the bike). My current solution to this is to manually pulse the brake lever a few times when I start braking, but obviously an electronic solution would be more ideal.

Flow Chart: Below is a flow chart for the decision making that the device must perform.  I included this to give you a better idea of what I am thinking about.

Main Questions: One of my requirements is that this be a "drop-in" solution.  By this I mean that the device should be in series with the wires controlling the running light/brake light.  There is space under the rear seat which is just above the taillight to house the device, but consideration must be given to the fact that there is heat, vibration, etc.  There is a fair amount of heat (not too excessive) because the motorcycle has an under-tail exhaust.

Ideally this device should perform its functions without producing adverse effects on the circuitry upstream from it.  Before prototyping anything on a solder-less breadboard I have, I plan to take current and voltage measurements on the wires that presently control the running/brake LEDs.

FYI, the running light is ON whenever the ignition is ON.  The brake light is simply the running light LEDs but 2-3X brighter and the brake light is activated if either front brake lever or rear brake pedal are activated (Or both).

Note also that "OFF" in the chart below refers to LED brightness corresponding to the running light and that "ON" refers to LED brightness of the brake light.

Basically my questions regarding all of this are:

Can this be implemented with low level components? (resistors, diodes, transistors, caps, etc.)
I have some experience with microcontrollers (Basic Stamp) and to make something using one of them such as an Arduino or Basic stamp seems straightforward.  But I would prefer something a little more rugged to be able to survive inside the tail area of the bike!
I have looked at some multivibrator circuits and think that what I need is some combination of a 3 shot multivibrator and an R-S flip flop, but I can't seem to figure it out...
With either solution type (low level components or microcontroller), it would seem that the device needs to be triggered by the increase in current (and or change in voltage) associated with the taillight going from the running light mode to the brake light mode.

Thanks for reading this and I hope it wasn't too much text!  I have some more info that I can post as followup too if there is discussion in this thread.


texts:
I have a PCB with a mechanical relay and traces rated for 20A at 120V.  I noticed the traces are heavy but also have solder on the actual surface of the board.
I am interested in doing something like this for a project with similar power requirements.
Did the PCB designer just remove the solder mask?  Is adding lead/silver solder on the face of a PCB good practice for high current requirements?


texts: Controlling brushed motor speed with variable load with a PWM

texts:
I am considering driving a brushed motor driver with an H-bridge and PWM. I'd like to roughly control the motor speed regardless of the motor's load (envision a small robot climbing/descending hills).

Since I know that if you power a brushed motor with a constant-voltage power  supply, it will always rotate at about the same speed, with the current drawn reflecting the load (conversely, drive it with a constant-current power supply, and the motor speed and voltage will vary according to load).

Knowing the above, it seems simple to get feedback via an A/D to read the voltage being applied to the motor and have software tweak the PWM, to keep the voltage on the motor set according to the speed demanded.

I would need an LC in the circuit, because I would not be able to read the voltage that's got PWM noise on it.

Does the above make sense?


texts: Problem controlling common cathode 12V RGB LED

texts:
I want to be able to control an RGB LED with common cathode and I've used the circuit below for each colour. For some reason there is 12V on the output all the time and I can't control the LED as it's switched on all the time.

Any help will be greatly appreciated.


texts:
I dont know what is happening here.
Both PMOS and NMOS have

W=100*270nm
L=180nm
Vgs=1.8v
vds=1.8v

while NMOS is carrying only 14.19mA current, How can PMOS carry 15.97mA for the same size and Voltages ?


texts: What calculations determine the choice of the overload relay trip class to protect a motor

texts:
I know that the motor trip current determines the choice of the trip class, but I do not know what are the range values for each one.
Lets say that I have an engine with a trip current of 190. Somehow somebody said that the trip class should be 20, which is the standard among the other( 10, 30...), but could not account for the choice.

Regards


texts: What is the diode used for in this circuit?

texts:
In this schematic (it is of a board from Adafruit, I included the link below) what is the diode's purpose?  Originally, I thought it was to only allow for an logic signal from the Reset Pin, but then, wouldn't the diode be placed in the opposite direction?  I am not really an Electrical Engineer, just curious.

Thanks.

Full Schematic:

https://cdn-learn.adafruit.com/assets/assets/000/024/546/original/sensors_BNO055_REV-C.png?1429569060

Image:


texts:
I've been working with some PIR sensors from Panasonic, and I was wondering if there are any types of female headers/connectors that I could use to wire the three pins of the sensor without directly soldering wires to the connector. I've been looking, but I haven't been able to find any types of connectors which would fit.

Off the top of your head, are there any types of connectors which could be used to easily wire this?

If it helps, the sensor fits into a standard breadboard as in the image below:

For some more information, here's a link to the digikey part (MFG P/N:)
http://www.digikey.com/product-detail/en/AMN41121/255-1808-ND/735391

And here is a link to the datasheet. All sensors have the same pins at the bottom:
http://www3.panasonic.biz/ac/e_download/control/sensor/human/catalog/bltn_eng_mp.pdf

Thanks!


texts:
I am trying to modify an old 350W PC PSU in order to run some 12v and 9.6v cordless tools.
I put 2 10Ω 5W resistors in parallel between 5V and ground and I shorted the green wire with ground. I can easily run a 5V screwdriver directly from the molex. I can also run a 12V motor with no load directly from the molex.
But when I try to run my 9.6V drill from the 12V rail the PSU turns off. I can run this drill from a 12V wall adapter and it runs fine but the adapter doesn't provide enough amps so the drill is weak.
What could be the problem with the power supply? Thanks a lot.


texts: Battery systems for 440v industrial motors

texts: Are there systems utilizing batteries to start large (25hp - 50hp) 440v 3-phase electric motors, thereby eliminating spikes to the supply grid?


texts: What's a single-ended single duplex buffer with 5V drive strength?

texts:
I'm interfacing to the "Dynamixel TTL" bus, which is a simple TTL serial bus with multiple talkers. Thus, while I'm not talking, I need to tri-state the output, and be prepared to read input. There is a single coordinating master, so collision detection is not necessary.

The bus is specified at 5V, and my microcontroller is 3.3V, but it's 5V tolerant so as long as I can drive 5V and 3V counts as "high" for the inputs of the buffer, I'm fine.

I've been using 74HCT125 chips for interfacing, using two of the elements. This is annoying, because I need to invert one of the "enables" in the buffer to get output-vs-input to be decided by a single pin.

There are a number of RS-485 drivers that have the right "shape -- OE, !RE, driver, and receiver. They can even translate voltages. But they output differential signals (A/B.) I just need a single-ended signal.

I'm considering using a RS-485 buffer chip, and just tying the "B" wire to a resistor divider to decide the high/low detection point of the "A" wire, but I'd hope there's something more elegant -- something not requiring more external resistors, for example. It should also be an active surface mount part, not something I can only find in '70s basement clean-out sales :-)

The 74AUP1T45 from Nexperia is almost right, except it only goes to 3.6V. (I don't control the bus specification; I need to drive at 5V and be tolerant to at least 5.5V.)

Parametric searches at Mouser and Digi-Key don't show something obviously better than the re-wired 485 driver option, so I'm turning to this bigger brain: What's a great part for these requirements?

SN74ABT245 has the right topology and function, but it has way too many pins because its an 8-channel device, and it's also TTL and thus has low output impedance (only guarantees 3V output with 5V VCC.)


texts: Memory backup capacitors: why a capacitor?

texts:
Why would an engineer choose a memory backup capacitor instead of any of the types of rechargeable batteries available?

Their energy density seems far poorer, and they can't hold their charge very long.

The only advantage I can think of is it's slightly simpler to charge? (Just needs a resistor), but then again, the same can be said for trickle charging many batteries.


texts: How to lower volume on microphone input before outputting through headphones? (Using a DSP)

texts:
As part of a senior engineering course, my partner and I decided on tackling the problem of hearing loss in youth, and went with a more preventative approach, trying to reduce the amount of cases rather than cure hearing loss. In our efforts, we decided that it would be most appealing and effective to design a pair of headphones that are of decent quality while having an "Active listening" feature as well, but instead of using that feature to make low sounds louder, we wanted to do just the opposite to prevent volume from reaching a certain decibel level to prevent hearing loss from occuring. I have a post regarding this same type of question here (http://forum.arduino.cc/index.php?topic=386968.msg2676322#msg2676322) where I found out that an arduino would not be best suited for this type of project, but instead to use Digital Signal Processor.

This is where I am so far, not sure on how to proceed using said DSP to convert the analog signal to digital and then lower voltage before converting it back to analog signal. We would probably be using a raspberry pi as a hub for power and usb inputs.

Edit: We plan to use TI Code Compiler Studios as well as a programmable usb DSP if possible.

The main questions I need answered right now are these

Can this be accomplished in a reasonable time period? (<2 Months time?)
Would I need to create my own audio input and output devices, or could I use an existing pair of headphones to receive and play sound that is converted?
Where can I look for additional help regarding this type of problem?

Thanks to all who took the time to read through this, I know it was long, and thanks to anyone in advance for any reply I receive.


texts: When to process beam forming algorithms?

texts:
I am building a system that uses beam forming to locate noises at different spots. All of the spots will be in front of the microphones (180 degree range of spots).

My first question is if the beam forming algorithms have to be done when receiving the data from the microphones or is it possible to store the information raw and apply algorithms for beam forming after. I ask this because there is multiple locations at random times so we would have to modify the beam forming on the spot which would require faster, more expensive hardware. If we can store the data then apply algorithms we can save cost because we won't need as much speed.

Is identifying multiple noise locations at random even possible?

I am looking for specific sounds, so other sounds will need to be cancelled out or be able to be ignored. This is why I can't use a simple technique as where did the loudest sound came from.

Thank you in advance!


texts: Help understand a simple C code for an atmega16 project

texts:
I just got started with AVR , and I am building a Lan tester for a project

My hardware part is done, basically for the send pins I used port A , from A0 to A7 and for the Receiver port C when the cable is inserted in the RJ jack a signal should be sent and compared to some existing vectors , the result of the vector comparison is sent to port B and a led corresponding to the cable type should turn on

here is the code,I commented the parts that I cant understand, please help me with them
the most part the confused me is the ">>" i know it shifts but what exactly
why do we return 0 then 1 or the opposite
and why the status=0 ?

#define DSEND               DDRA
#define DRECEIVE            DDRC
#define DLED                DDRD
#define ISEND               PINA
#define IRECEIVE            PINC
#define ILED                PIND
#define OSEND               PORTA
#define ORECEIVE            PORTC
#define OLED                PORTD

// the cabels types vectors
int STRAIGHT[8]=        {1, 2, 3, 4, 5, 6, 7, 8 };
int CROSS_T568A[8]=     {3, 6, 1, 7, 8, 2, 4, 5 };
int CROSS_T568B[8]=     {3, 6, 1, 4, 5, 2, 7, 8 };
int ROLLOVER[8]=        {8, 7, 6, 5, 4, 3, 2, 1 };

// why do we need to start with zeros ? and why is the status 0 ?
 int TEST[8]=       {0, 0, 0, 0, 0, 0, 0, 0 };

 int status = 0;

//why retrun i+1?
 int getActiveBit(int x) {
int i;
for(i=0; i<8; i++)
    if(bit_is_set(x, i))
        return i + 1;
return 0;
  }

  // comparing the two vectors
  // but why return 0 this time ?
  int compare(int *a, int *b) {
  int i;
  for(i=0; i<8; i++)
    if(a[i]!=b[i])
        return 0;
return 1;
}

//setting the status, what status exactly
 void setStatus(int value) {
status = value;
}

 //get the status
int getStatus() {
return status;
}

   //display the cable type with a corresponding led each type with a led
  // what is this << I know it shift but what
   void displayMessage() {
if(compare(TEST, STRAIGHT))
    OLED |= 1<<1;
else if(compare(TEST, CROSS_T568A))
    OLED |= 1<<4;
else if(compare(TEST, CROSS_T568B))
    OLED |= 1<<5;
else if(compare(TEST, ROLLOVER))
    OLED |= 1<<6;
else
    OLED |= 1<<0;
}

//check if the cable is inserted
int isCableInserted() {
int i, r;
for(i=0; i<8; i++) {
    OSEND = 1<<i;
    r = IRECEIVE;

    if(getActiveBit(r) != 0) {
        OSEND=0x00;
        return 1;
    }
}
OSEND = 0x00;
return 0;
  }

  int main() {
  //why so many variables
    int i, r, k;

DSEND = 0xFF;
DRECEIVE = 0x00;
DLED = 0xFF;

do {
    if(isCableInserted()) {

        OLED = 0x00;
        OLED |= (1<<6);
        OLED |= (1<<5);
        OLED |= (1<<4);
        OLED |= (1<<1);

        for(i=0; i<8; i++) {

            OSEND = 1<<(7-i);
            for(k=0;k<10;k++)
                _delay_ms(100);
            //_delay_ms(1000);

            // what is this exactly ?
            r = IRECEIVE;

            // memorise
            TEST[i] = 8-getActiveBit(r)+1;

            if(TEST[i] != 0) {

                //if at least one wire is connected the cable is connected
                if(getStatus() == 0)
                    setStatus(1);
            }

            for(k=0;k<2;k++)
                _delay_ms(100);
            //_delay_ms(200);
        }

        OSEND=0x00;

        if(getStatus() == 1) {
            OLED=0x00;
            displayMessage();
            for(k=0;k<30;k++)
                _delay_ms(100);
            //_delay_ms(3000);
            setStatus(0);
        }

    }
    else{
        //the error led not insterted or defected
        OLED = 0x01;
        for(k=0;k<30;k++)
            _delay_ms(100);
        //_delay_ms(3000);
    }
} while(1);

return 0;

}


texts: Integrating third-party IP core using Xilinx command line tools

texts:
I am trying to integrate a third-party IP core, which is given in form of an .ngc netlist file and a corresponding .vhd file with only the entity declaration, into my design. The IP core was synthesized with Xilinx ISE.

I have instantiated the core in my design and connected all external signals.
However, I fail at finding the correct point in the command line tool flow of Xilinx, where I can include the netlist file such that it is used during translation(ngdbuild). At the moment I only pass the path where the .ngc file is located to ngdbuild via the -sd flag and do the same for the .vhd file when calling xst.
Up to now, in the final design, the IP core is missing. The synthesis report shows that there is a warning "WARNING:HDLCompiler:373 - "" Line 43: Entity  does not have an architecture", and the synthesis summary shows that no logic has been inferred for this module. (This is to be expected since the netlist file should be used instead of synthesising any logic).

Is there a naming convention that has to be met so ngdbuild can link the .ngc file to the correct entity (netlist file and entity have different names) or what is it that I am missing completely?


texts: Why input/output ground is different and connect them by 0.1 ohm resistor?

texts:
This is a sample schematic at On Semiconductor TL494 datasheet.

It's a buck converter using pnp BJT (Tip 32A) as a switch.
What I'm interested in is the 0.1 ohm resistor (in yellow circle).
I havn't seen this type of buck converter curcuit that has separate grounds and connected by a resistor.

What's the benefit of adding this resistor?


texts: Bipolar class-AB amplifier analysis questions

texts:
I am analyzing the following amplifier schematic: Bipolar amplifier

I'm wondering if there are any transistors that need to be cooled apart from  the 4281A and 4302A output stage transistors?

What is the function of R22 and C7 and how do these work?

https://sound-au.com/project68.htm


texts: Ways to observe clock signal of an STM32 MCU

texts: Is there a nice way to be able to observe the clock signal in an oscilloscope to validate my settings for clock speed? After setting it to 168 MHz with PLL for an STM32F407VGT6 MCU let's say.


texts: How do I program an Atmel SAM in the field?

texts:
We have designed some Atmel SAM based boards that we want to make upgradable in the field. We do not have a bootloader yet (planned in the  near future) but we need to make sure they are reprogrammable before the bootloader is ready.

How can I achieve the workflow that we can give our client a tool and binary, and they can flash it into the chips? We have SWD interface on the boards. Is there any SWD based software tools for programming flash?

If not, is SAM-BA over UART a viable option?

For development we use Atmel Studio and an Atmel-ICE.


texts: Calculation of collector resistance for maximum output swing

texts:
simulate this circuit – Schematic created using CircuitLab

Question from Sedra and Smith (7th Edition)

Question: The given bias arrangement is to be used for a common-base amplifier.  Design the circuit to establish a dc emitter current of 1 mA and provide the highest possible voltage gain while allowing for a maximum signal swing at the collector of ±2 V. Use +10 V and -5 V for power supplies.

So far, I have calculated Rb = 0 and Re = 4.3k ohms. But I am unable to proceed further, for Rc. I tried the following approach,

$$ I_{E} = I_{C} = 1 mA $$
$$ V_{E} = - 0.7 V $$

$$ V_{C} = V_{CC} - I_{C}*R_{C} $$
$$ R_{C} = \frac{V_{CC} - V_{C}}{I_{C}} $$
$$ R_{C} = \frac{10\pm2}{1 \times 10^{-3}} $$

Answer: $$ R_{C} = 8.4k \Omega $$
What am I doing wrong here?

Edit:

The text before the question is as follows: Note that if the transistor is used with the base grounded (i.e. the common base configuration), then Rb can be eliminated altogether. On the other hand, if the input signal is to be coupled to the base, then Rb is needed.

Also, my textbook considers that \$ V_{BE} = 0.7 V \$, and as \$ V_{B} = 0 \$, hence \$ V_{E} = -0.7 V \$.


texts: Diode in place of manual switch for HV application

texts:
I am building a HV experimental setup for energy harvesting, where I have some HV capacitors in series. I need to put diodes between the caps to act as switches. The maximum reverse voltage they need to withstand is about 5kV. They need to have as low forward voltage as possible. Their switching speed is not too important.
Anyone got suggestions on what diodes to use?
(I am a physicist/mechanical engineer, so please excuse my ignorance about electrical engineering).


texts: Impedance problem (polar to rectangular)

texts: Having a little problem understanding why this example converted polar to rectangular form to get Z. What is wrong with just leaving it in polar form and doing the algebra to get the value for Z


texts:
how exactly does glitch happen for rising-edge and falling-edge ICG ?
Why for the top version of rising-edge ICG, there is no X at the MSB of the latch output ?

Note: TE signal is asynchronous to CLK, and see also the red 0 and 1 at the output


texts: Multiplexers used as a switch seem to "leak" when power is cut

texts:
Description

Attempting to build a device using the Arduino that will allow me to remotely restart a cluster of desktop computers that I have. The device works by momentarily connecting the RESET button jumpers on a desktop's motherboard. Two multiplexers are used so that 8 desktops can be connected to it at once. One multiplexer controls the reset button ground and the other controls the reset button positive terminal. Two multiplexers are needed to connect the same mother board ground to the same mother board positive.

Problem

The problem I am having is that the device works when connected to my laptop USB, but restarts the computer when I disconnect power. The device does not work at all when I connect it to the USB of my lunux server, instead seeming to send some kind of very weak signal to the mother board RESET leads that causes the mother board to freeze rather than reset.

I think the problem has to do with my limited understanding of the nuances of electrical flow through these devices. I feel like there must be some kind of backflow or small leakage that is causing disruptions for this use case. As you can see, I've added diodes connecting the power. This significantly lessens the chance of the motherboard restarting when I disconnect the power, but it still happens sometimes. Also, the device still only works when connected to my laptop USB and not my linux server USB. I feel like there is perhaps some configuration of diodes, capacitors or different types of switches that should be used. Such as a relay or MOSFET instead of the multiplexers?

I did try completely disconnecting the yellow wire before disconnecting the power, but this did not help. It seems that a signal is leaking from the mother board ground to the mother board positive through some other channel. The only thing that works is to physically disconnect one of the mother board leads from the board before disconnecting power. Connecting the mother board positive or ground to the arduino's positive or ground also does not reset the mother board. This implies to me that a signal is somehow leaking directly from one mother board lead to the other through the system.

Example

In the example below, only one desktop motherboard is connected for testing purposes (via the yellow and blue wires). The LEDs on the right side are for "debugging" purposes so I can see which control leads are actually delivering charge to the multiplexers. The green wires connect like control leads to each multiplexer (so A,B,C, and INHIBIT are the same for each one) and the yellow wire connecting the two multiplexers connects the "OUT" of the ground multiplexer to the "IN" of the positive jumper wire multiplexer.


texts:
Related to my last question, I decided to go with a step-down charge pump to convert 5V to 35V down to 3.3V at 10mA, due to the smaller required component size. However, I can't find a single charge pump IC rated to go up to 35V. Does anyone have any suggestions? If there are no ICs to do this, woudl there be any way of dropping 35V down to 18V with minimal loss and a small surface area?

I'd also be open to using a buck regulator, but it seems like a waste for only 10mA.


texts: Why does Modelsim say that VHDL shared variables must be protected?

texts:
So I created a shared variable in a purely non-synthesizeable code.

When compiling ModelSim generates a warning:

  (vcom-1236) Shared variables must be of a protected type.

Why is it a warning and not an error if the shared variable must be "protected"?
What does protected even mean in this case i.e protected from what?

The shared variable is just a std_logic.


texts:
I have a 5v infrared beam reflection circuit for capturing heart beat from fingertip. I am using LM324 low pass filter to filter out the noise and i have isolated the ir sensors by covering the sides with a black tape but the noise is not reducing.
My output is a blinking LED and the LED is not supposed to light until a finger is placed on the ir pair but the LED lights up whenever i power the circuit.
Below is my schematic


texts: How do I solder a ~20-pin USBc connector near heat-sensitive components?

texts:
I currently have an LG V20 and its charging port is deteriorating. Unfortunately, it is out of warranty and the best price that I can find to have it professionally repaired is US$60, which is about half the cost of the phone. As such, I would like to try to repair it myself, with this replacement part (I am open to advice on a better alternative, but I don't see anything wrong with this one.).

I have experience soldering for plumbing, through-hole PCBs, and just bare wires. I have not, however, ever worked with surface mount components or anything this small before. I found a YouTube video that goes through the motions of such a repair, but it doesn't have the kind of detail that I need to figure out how to do this properly. At best, I could mimic what I see the person in the video doing, but that isn't ideal for obvious reasons. It is also worth noting that, according to that video, there are several heat-sensitive components (such as a piezoelectric microphone) very close to the port, making hot air a bad idea.

As such, I ask: What is the best way to replace a component of this type (with plenty of keywords so I can go and learn the techniques that I need), given that hot air is a bad idea?

EDIT: I would like to note that I have access to a fully tooled electronics lab. Tools are not an issue.


texts:
I'm new to StackExchange.

I would like to know if it is possible to use a P2 connector to capture audio.

I already use it to play audio on headphones but I plan to pick up the audio from a smartphone and play it on a speaker I have.

Is it possible? If so, can you please tell me what could I do to achieve this?

Thanks in advance!


texts: Altium: Parameter from 'Sheet Symbol' in Schematic also displayed on PCB?

texts:
As image below, I have a 'Sheet Symbol' that I will use many times. I have defined a parameter for the 'Sheet Symbol' called 'name'. Is there a way of having this text shown on the overlay/silkscreen of the PCB 'automatically'. To prevent me from having to type out the text again? but also for tighter synchronism between PCB and SCH?.

The only thing I can think of is making a fake symbol called 'PCB_LABEL', where I just utilise say the comments parameter, to achieve the same result, albiet less elegantly.


texts: LiFePO4 16-cell stack precision dc volt measurement LTC2400 MUX

texts:
I would like to build a highly precise volt meter (5 digits; e.g. +/- 1mV) to measure each cell voltage in a LiFePO4 battery stack of 16 cells (<60V).
I am content with measuring the cell between 3 and 4 Volts (1V range) if possible / doable.

I selected an LTC2400 for the precision A/D conversion, and thought that a 16-channel MUX would allow me to measure one cell after the other; but it appears this would not work. I thought I could use 1 or 2 MUX to loop the pos/neg connection per cell to the Volt meter.
Another option would be 16 volt meters (one per cell) but it seems like a lot of duplication of gear, hence, a silly approach.
An Arduino would to some calculations and comms.

I did not want to use a high Voltage MUX due to accuracy/resolution constraints, but rather measure each cell (and am not interested in the total V).

It is sufficient to measure the 16 voltages within one second disregarding any Amp fluctuations -- as the battery system has pretty stable current flows.

Any hints / pointers are much appreciated; thanks.


texts: What are rubbery, conductive strips called on the sides of an LCD screen?

texts:
I found a component attached to a PCB inside one of my old $5 devices. There are pink, rubbery things attached to either side of the LCD that can bend and were firmly attached (glued?), and there are a lot of exposed conductive traces where the pink things were attached on the PCB.

I would like to know what these pink things are. Pictures are shown below.

The front side of the LCD ^

The back side of the LCD ^

The front side of the PCB. This is where the LCD is connected to. ^

The back side of the PCB ^

Again, I would like to know what the pink things are.


texts:
I am new at programming PIC24FJ1024GB610, and I just started reading the Manual.

On page 45/468, at Chapter 3.0 CPU. It is mentioned that:

  The lower 32 Kbytes of the Data Space (DS) can be
  accessed linearly. The upper 32 Kbytes of the Data
  Space are referred to as Extended Data Space (EDS),
  to which the extended data RAM, EPMP memory
  space or program memory can be mapped.

What do they mean by that paragraph?

Is the EDS inside the Program Memory (as in the picture below)? If so how come it have Extended Data RAM and EPMP, when they are 16 bit addressable, and Program Memory Space is 24 bit addressable?

Kindly help me on this question.


texts: Clarification on interrupt triggered DMA transfer in an STM32

texts:
I'm trying to learn about DMA and its use in the STM32L4S9VI platform. One thing I'm confused about is what binds the DMA transfer to any one specific interrupt? In the below example, I'm curious which UART interrupt triggers the transfer of the next byte into the transmit data register, as well as how the DMA determines which interrupt from UART was called. As I understand it, there is actually only 1 general USART2 interrupt line that goes to the DMA, so how does the DMA actually know that the interrupt is the one that signals that it's ready to have another byte put into the transmit data register? Does

HAL_UART_IRQHandler(&huart2);

take care of it?

Example:

/* Private variables ---------------------------------------------------------*/
extern UART_HandleTypeDef huart2;
DMA_HandleTypeDef hdma_usart2_tx;
char *msg = "Hello STM32 Lovers! This message is transferred in DMA Mode.\r\n";

/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void DMATransferComplete(DMA_HandleTypeDef *hdma);

/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/

/* USER CODE END PFP */

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

int main(void) {
  HAL_Init();

  Nucleo_BSP_Init();

  hdma_usart2_tx.Instance = DMA1_Channel7;
  hdma_usart2_tx.Init.Request = DMA_REQUEST_2;
  hdma_usart2_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
  hdma_usart2_tx.Init.PeriphInc = DMA_PINC_DISABLE;
  hdma_usart2_tx.Init.MemInc = DMA_MINC_ENABLE;
  hdma_usart2_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
  hdma_usart2_tx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
  hdma_usart2_tx.Init.Mode = DMA_NORMAL;
  hdma_usart2_tx.Init.Priority = DMA_PRIORITY_LOW;
  hdma_usart2_tx.XferCpltCallback = &DMATransferComplete;
  HAL_DMA_Init(&hdma_usart2_tx);

  /* DMA interrupt init */
  HAL_NVIC_SetPriority(DMA1_Channel7_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Channel7_IRQn);

  HAL_DMA_Start_IT(&hdma_usart2_tx,  (uint32_t)msg,  (uint32_t)&huart2.Instance->TDR, strlen(msg));
  //Enable UART in DMA mode
  huart2.Instance->CR3 |= USART_CR3_DMAT;

  /* Infinite loop */
  while (1);
}

void DMATransferComplete(DMA_HandleTypeDef *hdma) {
  if(hdma->Instance == DMA1_Channel7) {
    //Disable UART DMA mode
    huart2.Instance->CR3 &= ~USART_CR3_DMAT;
    //Turn LD2 ON
    HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
  }
}


texts: Could an analog TV signal be transmitted over broadcast RF from a composite cable somehow?

texts:
My understanding is that an analog video signal (PAL or NTSC) has a particular form/structure.

That signal can be transmitted over the airwaves at a particular frequency, & multiple analog TV signals can be transmitted at different frequencies.

Composite video is where a single video signal goes down a cable with RCA connectors at each end and is displayed on an analog TV.

Analog televisions do not need to be "tuned in" to the composite cable signal.

So I have a few questions:

What is the real difference between the signal on a composite cable and the RF signal that comes over the air?

I understand that the composite cable signal does not have audio, but apart from that, what is different?

What frequency is the signal transmitted down the composite cable?

Would it be possible to transmit at a different frequency down the composite cable, say for example at a frequency range that an analog TV could pick up?

And if yes, would it be possible to just have that signal transmit into the air, effectively making the composite cable a transmitting antenna?

And could an analog TV sitting nearby then pick up that analog TV signal?


texts: What is the mechanism that causes two conductors to "stick together" when a current is passed?

texts:
If the positive and negative terminals of certain DC supplies are brought together under certain conditions, the wires will "stick together" with a slight force, feeling almost like they are magnetically attracted. The force is perhaps only slightly stronger than the weight of a paper clip, but it's obvious if the two wires are hanging freely when they are pulled apart.

This effect can be easily reproduced with a bench supply. 12V and a current limit of about 2A will do. I get good results with alligator or banana clips. Even 12V with a current limit of 100mA seems to be enough. The issue here is the response time of the supply, which is another variable. Perhaps 100mA is meaningless in this case, because upon contact, a much larger current has already passed? If I try 3V and 4A, the effect seems weaker.

I assume this is the same phenomenon that causes broken filaments in incandescent bulbs to re-stick once contact is made. When conventional car headlights "burn out", often the filament is left dangling and can be temporarily restored by banging on the headlight or slamming the hood. The headlight may then work until car shuts off, or even days after.

I also assume this is the same phenomenon that damages relays that close under high loads.

What is the mechanism behind this?

I am doubting magnetism. My guess is micro-arcing (welding).

My reasoning:

Once the two wires are connected, they are essentially one wire. I'm not keeping them running along each other in parallel. They are making a large, 1 meter circular loop to the supply. Keep in mind that the wires themselves do not appear to attract or repulse, it's just the ends.
If I make contact and then move the wires along each other (while keeping contact), I no longer notice an attractive force when separating them.


texts: I'm an electrical student in my second year and I'm using a breadboard for multiple lab classes. I'm thinking that my breadboard is starting to fail inside and I'm having a hard time troubleshooting circuits and getting some weird result.  Today I had a JK Flip Flop hooked up as a Frequency divider and output on the oscilloscope was coming out a extremely high frequencies and there was no amplitude.  One second the output would show up and then another second the output would disappear.  I'm wondering where to buy a high quality breadboard since the ones we used to get are not made anymore.  The breadboard I have has a hard plastic back so you can't push leads through the backing by accident very nice feature.  Now that my circuits are becoming more complicated I don't want to have a breadboard that fails me in lab class.  Any suggestions would be great, thanks.


texts: RF (2.4GHz) LNA board with multiple amplifier stages: Should I use multiple voltage regulators?

texts:
I'm working on a LNA board to work in the 2.4GHz band. I'm using broadcom/avago MGA-635P8 amplifiers. Since I need more gain than a single stage can give me, I'm using 3 stages in cascade (although not truly in cascade, since there is a filter in between the first and following 2 stages, on a different board).

Since my board space is defined by the RF signal paths, I have a lot of board space left. I was wondering if it was a good idea to look at giving each of the LNAs its own local voltage regulator. Currently I'm using one voltage regulator to go from 6.5 to 5V, and then using this to go to the biasing networks of each of the chips (with a good amount of decoupling capacitance to try and avoid signal coupling through).

Will going to a multi-regulator offer any significant improvement, or is it not really necessary with modern IC's such at these "low" frequencies?


texts:
I need to replace a 2-pin fan on my PSU unit. The fan is 40x40x20, DC12V, 0.15A. I am replacing the fan because the noise is unbearable, >75dB right next to it.

Can I simply buy a 3-pin fan and cut off the 3rd cable? I was unable to find any 2-pin cable in stores around me and I expect there will be even less choice if I want a silent fan.
What happens if the new 3-pin fan is not rated as 12V fan, but 5V? Do I just add a resistor to the positive cable?
Another issue is that the connector won't fit and I’ll need to use the existing connector or buy an 3-to-2-pin adapter, if I can find one.

Thanks for the help.


texts: What is the purpose of inserting resistors (diodes?) directly on the path of the VCC and GND lines powering a PCB?

texts:
I am trying to learn electronics by looking at simple circuits and see how engineers get the job done.

Looking at a PCB featuring only one Texas Instruments ADS1115 ADC, I see that:

They bridge VCC and GND with a capacitor as close as possible to the power lines arriving at the PCB. I guess it's 100µF (shown in the picture).
They do the same on the VCC and GND as close as possible to the chip (not shown in the picture).
They have pull-up 10K resistors on the SDA, SCL and ADDRESS lines. I guess it's because they wish those to be high when not driven (not shown in the picture).

However, I do not understand why they have two parts (black 0805) inserted in the VCC and GND lines arriving on the board (shown at the top of the picture). Are these resistors ? What would their purpose be ? The board can be powered from 1.8 to 5 V.

Maybe they are only diodes? In that case, the polarity should be marked. And there would be a voltage drop across.

I am also puzzled, because these parts are across the VCC as well as the GND. In my mind, there is never any part splitting the GND line.


texts: how to find Vout for this fourier transform , given Vin

texts:
I don't know how to deal with the summation form !!!
It's an old exercise from my friends notebook .


texts: When does a transistor act as a switch, and when as an amplifier?

texts:
I'm a beginner with electronics, anyway I'm experimenting a lot with it.
I still don't understand how you can use the same transistor for example to amplify an audio signal, or to act as a switch for turning on and off the current of a motor.
Do you use different types of transistor for different purposes?
Any help is appreciated, please be tolerant and try to explain it in a simple way, I'm new to electronics


texts: How to name SMD packages in my Pick&Place library

texts:
I have massive problem with finding a correct scheme to name the packages correctly in my Pick&Place machine's library.

For example: QFN-16
I have one QFN-16 with 6+6+2+2 leads
and another QFN-16 with 4+4+4+4 leads.
Both also have different outer dimensions.

One is 0.6mm thick and another one maybe 1.0mm
Since height is very important for the Pick&Place machine, I would have to distinguish these again... so I end up with toooo many QFN-16 entries...

However, both are named as "QFN-16" by vendor and manufacturer.

I started naming my parts "QFN-16_3x3_6+6+2+2" and so on, but this gets suuuper confusing and doesn't even include the height.

Any ideas? I'm not using Altium or anything like that. I just do a small production.


texts: Is it possible to add gain to a dipole antenna without changing its radiation pattern?

texts:
In every reference book I've seen, an electric dipole antenna has basically a donut pattern, and as things are added to increase the gain (directors, reflectors etc) the pattern changes.   I've always understood this as saying that the only way to get more gain out of an electric dipole is to change the antenna pattern, reducing the beamwidth in one or the other or both axis.
Correspondingly, it seems like this is saying that increasing the gain may keep the volume enclosed by the antenna pattern (in 3 dimensions) constant, and the gain modifiers change the shape of that space.
Obviously I'm speaking ONLY of the gain of the antenna itself, no amplifiers etc, and that the initial dipole is already optimal, not built out of wet string or other lossy material. :)
Am I understanding this correctly?
Is this more of a physics question than an EE question?


texts: Using a counter to reduce pin counts for SPI slave selection

texts:
I've got five SPI SRAM chips, which I want to control off a single Arduino. I've seen setups like this, which share SCLK, MOSI and MISO, with separate SS pins:

(image courtesty of Wikipedia)

However, I'd like to avoid using five pins for separate SS enables. I'm considering using a counter to select the different slaves, so I can cut the count down to 2 pins.

The idea is to use two pins for the counter's direction and clock. The code would look something like this:

int currentSlave = 1; // on setup I'll set the counter to 1

void SelectSlave(int id)
{
  // error checking
  if (id < 1 || id > 5) Serial.writeln("Invalid slave ID passed to SelectSlave.");

  // calculate the ID difference
  int diff = abs(id - currentSlave);
  if (diff == 0) return; // no need to do anything

  if (id > currentSlave) set(CTR_DIRECTION); // increment
  if (id < currentSlave) clear(CTR_DIRECTION); // decrement

  // calculate the number of clock pulses to send to the counter
  int pulses = 0;
  if (id > currentSlave) pulses = (1 << (id - 1)) - (1 << (currentSlave - 1));
  if (id < currentSlave) pulses = (1 << (currentSlave - 1)) - (1 << (id - 1));

  // send the clock pulses
  for(int i = 0; i < pulses; i++)
  {
    set(CTR_CLOCK);
    delay(1);
    clear(CTR_CLOCK);
    delay(1);
  }
}

I have a few questions:

Are there any issues related to turning multiple SS pins on and off during the interim counting period?
Can I rely on (most) counters being set to zero when it is first powered on?
Are there other/better ways to cut pin counts in this kind of setup?


texts: I apologize if this is a dumb question or answered elsewhere but I could not find a definitive answer.  What hardware do I need to upload code onto a PIC 10F200?


texts: How to perform analysis of Copper and carbon nanotube interconnects in CMOS using LTSpice?

texts: How is it possible to model interconnect as that of Copper or CNT in a CMOS inverter to analyze the delay and power using LTSpice?


texts: When create footprint in Altium, we can set the 'Electrical Type' of the pad, and have three choices: Load, Terminator and source. But what's their meaning and when they will take effect?


texts: 0.01mh-20H, Is that a good range for an inductance meter?

texts:
Inductance meters are relatively expensive for a student to afford,so, I decided to buy ECR-T4 tester which happens to test inductors and measude their inductance.
I have no idea about its accuracy but i don't need accuracy right now.
My main interest is switching power supply, can this thing be a good device to start with?


texts: How to detect the fundamental frequency of a human singing voice signal

texts:
I want to make a digital hardware chip that can input a human voice, (singing simple wordless long notes) and output a square wave that is the same frequency as the fundamental frequency of the voice. I want it to work in real time.

I would like to put the chip on my own PCB eventually. But I could start out by testing the concept on some kind of development environment that has the same chip that I would be using.

Can anyone tell me the best way to approach this problem? For example what type of algorithm would be best, and what chip would be good to use.

I read that autocorrelation and FFT are both used for this kind of thing, but I don't know which would be best.

I was thinking of using the STM32F427, because it seems to be very popular and is available in all sorts of hobby related development environments.

I don't expect anyone to tell me exactly how to do it in every detail. I just need pointing in the right direction.