texts: MCP604 op-amp output seems to jump to the positive rail

texts:
I'm hoping someone can give me some insight as to what's going wrong with this MCP604 op-amp.  I'm seeing this issue on about 150 of the ICs.  Below are some specs for the MCP604 and an image from my oscilloscope.

The yellow line is from the V+ of the op-amp, and the pink is Vout. It looks like the output is jumping up the positive rail.  Is this a defective part?

My input signal is 0 - 3.3 V and it's passing through a 10k resistor.  I have a 0.1 uF cap right next to the power connection.  Anyone have an idea of what's going on?


texts:
I'm sorry if this is the wrong use for stack exchange. I'm sure I will be notified by users if it is.
I have inherited a (female) DSUB9 to (female) DSUB9 cable from a very old project. The pinning perplexes me. What pinning is this? I mean, what is the name of this arrangement? I want to order at least one more. I could just deal with it and make an adapter for some female-to-male cable I have, but I want to understand.
EDIT: It's used to programmed a Cypress Semiconductor MCU CY90F543GSPFR-GE1
The cable is correct by the way, both pin 6 and 8 on one side go to pin 4 on the other. I figured it must be null-modem, but it does not match, as far as I can tell.


texts: Select a correct voltage controlled oscillator IC

texts:
I need to generate a sine signal using a VCO (voltage controlled oscillator) in order to feed a PLL (Phase-locked loop). I need the output to be 12.8MHz and 3.3Vp-p.

I bought at RS a VCO reference 7099357

Despite the datasheet says: "Output Level (CMOS) Output High (Logic “1”) - - 90% VDD" I can only have an output of 1.2Vp-p. Output frequency is 12.8 as expected. The IC is being feed with 3.3V DC.

What feature do I need to look at in order to select a componen that has the desired 3.3Vp-p output? Do you know any specific component I should use?

This is how I'm connecting the IC

VCO (RS-7099357) datasheet


texts: Is there an efficient way of recycling or reusing waste batteries and where am I supposed to throw it (Biodegradable, Non-Biodegradable, and Recyclables) ?


texts: During the check of pins on connector with a multi-meter, one of the pins that goes through the relay to provide ground signal, I am getting 8MOhm (8 megohm). I should not be getting anything on that pin as the relay should be de-energized. How should I interpret this reading? I was under the assumption since the readout in megohms should it be ignored as a possible issue?


texts:
We have a requirement, which is a normal self powered USB Hub, with individual power control of the ports, i.e in addition to a normal Hub, we want to remove the power to any of the downstream port on the fly using on-board micro controller.
I am not an expert of USB2.0 specification, so, if any thing wrong please correct me. i am learning.

USB hub circuit has basically a USB Hub controller like TUSB8040, Quad Powerdistribution switch
I have thought 3 possiblities.

1. I thouht to connect all OE# pins from Power distribution switch to On-board MC(Micron controlller) and connect I/O's of MC to TUSB8040's OC# pins. SO, that whenever we want to disable the Power to a perticular downstream port, that port OE# pin we will indicate Over Curretn condition from MC to TUSB8040. SO, that TUSB will disable that Port according to USB Spec. But, when i contacted manufacterur regarding he said this involves host communication also and it is not possible.

2. in USB Spec on these following sections
in section 11.5.1.2 states of Downstream ports "
11.5.1.2 Powered-off
This state is supported for all hubs.
A port transitions to this state in any of the following situations:
    • From any state except Not Configured when the hub receives a ClearPortFeature(PORT_POWER) request for this port"
One more section in USB2.0 spec, 11.11 Hub Port power control "A hub indicates whether or not it supports power switching by the setting of the Logical Power Switching Mode field in wHubCharacteristics. If a hub supports per-port power switching, then the power to a port is turned on when a SetPortFeature(PORT_POWER) request is received for the port. Port power is turned off when the port is in the Powered-off or Not Configured states."

Which indicates power to a particular port can be turned ON from Host if Hub supports the Per Port Power control.
for this i didn't get any reply from the Manufacturer yet.

3. we are planning to control the USB distribution switch using 2:1 mux ( one of the input from on board MC and another from TUSB8040, so, that when MC want to disable any port it can control ) When on board MC disconnects the Power to any Port it can be detected by Hub and reported to Host automatically.

I feeel 3rd approach is very good and works. Any body foresee any hiccups in this 3rd point method.


texts: How to know when you've reached enough resistance for a battery?

texts:
Let's say I have a 1.5 V AA battery. If I connect its terminals together, that creates a short circuit which could make the battery catch fire.

How do I know I've added enough resistance to the circuit so that the battery is safe to use?


texts: Purpose of the magnetics center tap in Ethernet

texts:
What how the magnetics center tap work in Ethernet HW configuration? I've read that it depends on the specification of the attached PHY, sometimes must be connected to the PHY's DC supply, but i can't understand why.

Thanks in advance


texts:
I have a problem with the NAK on the CAN bus. On STM32F303RE I wrote a code for communication via CAN bus with car dashboard (Instrument Panel Cluster). The communication works, I manage to receive frames from the device (e.g. below on the screen - a frame with ID:C194003) but each frame gets at the end of NAK.

I manage to send a signal on CAN bus (I send 0x700 frame) from which sometimes I get ACK and sometimes NAK. I don't know completely why the device doesn't expose the ACK bit. The Cluster Panel instrument has been taken out of the car so I don't think the CAN communication is badly done there. The transmission speed is about (50kbps)

code for clock initialization:

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Initializes the CPU, AHB and APB busses clocks
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
//  RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;
//  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB busses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART2;
  PeriphClkInit.Usart2ClockSelection = RCC_USART2CLKSOURCE_PCLK1;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
}

CAN parameters:

 hcan.Instance = CAN;
  hcan.Init.Prescaler = 45;
  hcan.Init.Mode = CAN_MODE_NORMAL;
  hcan.Init.SyncJumpWidth = CAN_SJW_1TQ;
  hcan.Init.TimeSeg1 = CAN_BS1_13TQ;
  hcan.Init.TimeSeg2 = CAN_BS2_2TQ;

  hcan.Init.TimeTriggeredMode = DISABLE;
  hcan.Init.AutoBusOff = DISABLE;
  hcan.Init.AutoWakeUp = DISABLE;
  hcan.Init.AutoRetransmission = DISABLE;
  hcan.Init.ReceiveFifoLocked = DISABLE; // New message will overwrite existing message in FIFO memory
  hcan.Init.TransmitFifoPriority = DISABLE; // Priority driven by the identifier of the message
  if (HAL_CAN_Init(&hcan) != HAL_OK)
  {
    Error_Handler();
  }

CAN Tx function:

void CAN_Tx(uint32_t CanID, uint8_t CanDLC, uint8_t CANmsg[])
{
    uint32_t pTxMailbox;
    CAN_TxHeaderTypeDef CanTxHeader;
    CanTxHeader.DLC = CanDLC;
    CanTxHeader.ExtId = CanID;
    CanTxHeader.IDE = CAN_ID_EXT;
    CanTxHeader.RTR = CAN_RTR_DATA;

    if ((HAL_CAN_AddTxMessage(&hcan, &CanTxHeader, CANmsg, &pTxMailbox)) != HAL_OK )
    {
        Error_Handler();
    }
    while(HAL_CAN_IsTxMessagePending(&hcan, pTxMailbox));
    Print_CAN_Frame("Tx",CanTxHeader.ExtId, CanTxHeader.DLC, CANmsg);

}


texts: What is reasoning behind the common wisdom of limiting the temperature rise of a PCB trace to 5/10/20°C?

texts:
When deciding on the trace thickness required to carry a certain amount of current on a PCB, the answer depends on how much temperature rise you are willing to accept. This leads the designer into the difficult situation of trying to decide how much temperature rise is reasonable. Common rules of thumb are to allow no more than 5°C, 10°C or 20°C of temperature rise, depending on how conservative you want to be. These figures seem remarkably small compared to the maximum temperature rises of power transistors, ICs, power resistors, or other heat-dissipating components, which may be 60+°C. What is the reasoning behind these numbers?

Possible reasons I've thought of:

Maximum temperature of PCB materials. For most FR4-type materials this is around 130°C. Even allowing for a very conservative ambient temperature (inside the chassic) of 65°C, this would still allow another 65°C temperature rise.
Allowing for further temperature rises of components. If an SMT MOSFET was going to see a temperature rise of 80°C for example, you wouldn't want to start it out 40°C above ambient because of the temperature of the surrounding PCB. However, this seems far too situation-specific to make for a rule of thumb. In the case of a heat-sunk through-hole MOSFET, for example, the heat flow up the leads is a fraction of the heat flow out through the heat sink, so the PCB temperature should not be a major concern. Even with SMT parts, I could have a thin trace which dissapates a lot of heat for the majority of its length, but then widen that trace before it reaches the component.
Thermal expansion of PCB materials. As the PCB heats up, the materials will expand. If different parts of the PCB are exposed to different amounts of heat, this could cause flexing of the board which could crack solder joints. However, given that PCBs are regularly exposed to higher temperature differentials than this due to power dissipation in the components mounted to them, this doesn't seem like the answer.
Outdated standards. Perhaps the 5/10/20°C limits were thought up years ago and no longer apply to modern PCB materials, but everyone has kept on following them without thinking about it. For example, perhaps old phenolic board materials were less tolerant of heat than modern fiberglass.

To put the question another way, say I find that a 20°C temperature rise is too limiting for my design. If I decide instead to allow a 40°C temperature rise, am I likely to run into either short-term or long-term reliability problems?

Bonus points to anybody who can cite standards that give a reasoning for the numbers, or who have historical evidence for why those numbers were picked.


texts: Why is there a limit on the number of inputs a logic gate can have?

texts:
We were told in class that although in theory we can have multiple-input logic gate and therefore can get a two level implementation of functions, it is practically not possible. I don't really understand why this is the case.
For example, if we take a 3 input AND gate (to implement F = xyz', say), it would have 3 MOSFETs in parallel and 3 in series, causing a delay of 3N (if N is the delay of each transistor.
Now instead, we only have 2 input gates available, and we implement w = xy' first and then F = zw, we would have a delay of 2N + 2N = 4N instead.
Clearly, the higher input AND gate is superior in terms of delay. What disadvantage do multi input gates possibly have that result in them not being used practically?
TIA


texts: SMD jumper / 0R resistor with long thin package?

texts:
I need 0R "resistor" with long and thin package for surface mount.

Is there something like "2405" (like 0805 but 3x longer) size package or something similar?

I just want to "jump" over few traces on 1-layer circuit board and avoid whole drilling process.


texts:
I am building a boost converter 12VDC-24VDC with output current of \$I_{out}=250\:\mathrm{mA}\$ and input current of around \$I_{in}=600\:\mathrm{mA}\$ and need to design an inductor for it. I've calculated that the inductance has to be \$L=125\:\mathrm{\mu H}\$, the switching frequency is 400kHz.

I have a ferrite core with 5mm diameter and 20mm length (I can cut it if necessary) and permeabillity of 12. I am also using 32 AWG wire (because of skin effect) which has a diameter of 0.2mm and \$R=538.3\:\Omega\$ for 1000m.

The equation of cylindrical coil is \$L=\frac{N^2\cdot\mu_o\cdot\mu\cdot A}{l}\$ where \$N\$ is number of turns, \$\mu_o\$ is permeabillity of free space \$\mu\$ is relative permeabillity of the core, \$A\$ is cross section area of coil and \$l\$ is length of the coil.

There are dozens of ways one can design an indutor based of number of turns and the length of coil, but increasing the length also increases the resistance of the inductor.

So what is the maximum resistance the inductor can have under these circumstances, how can I calculate it? So I know later on what length to take, and from this the number of turns.

EDIT:

I've calculated the inductance based on the equations found on this website, page 40.

Input ripple current: \$\Delta I=0.2*0.6=0.12A\$

Duty cycle: \$D=\frac{24-12}{24}=0.5\$

Inductance: \$L=\frac{12*0.5}{0.12*400000}=125\mu H\$


texts: How to build "two power sources" in a microcontroller circuit?

texts:
My circuit has a microcontroller, it uses power from a DC transformer (120V to 12V DC). My circuit also control an pneumatic valve which also use 12V DC. Almost every time when the pneumatic valve opens, the current becomes unstable. This makes the microcontroller restart.

Some guy suggested me to use two power sources. In my case, it is very rare for a microcontroller and a pneumatic valve to use two DC transformers. How can I build "two power sources" in a microntroller circuit?


texts:
Both the opamp terminal have tied to the same AC signal.
what is the exact behavior of this circuit, and what is configuration name for this circuit??


texts: How do you calculate the noise of an op-amp circuit?

texts:
I think I know how to do this, but you can find a lot of different instructions and calculators online that contradict each other.  I have yet to find a clear, concise procedure for calculating the self-noise of op-amp circuits (including thermal noise, shot noise, etc., but not including interference from external sources), and one of the sources many people cite apparently has a number of errors, so I'll ask it here and see who can explain it best.

For example, how would you calculate the output noise of this circuit?

Which noise sources do you include?

Op-amp internal input voltage noise
Op-amp internal input current noise
Resistor thermal noise
Op-amp output stage noise?

How do you calculate each component's contribution?  How do you combine the noise components together?  What gain do you use to get the output noise from the input equivalent noise?  How do you calculate the gain?  Is it the same as the signal gain?  What kind of simplifications and shortcuts can be made and how different will the result be from the real world?

etc. etc. etc.


texts: PCB Design for Rapid Charge/Discharge of Capacitor

texts:
I need your advice: I am very new to electrical engineering, and I would like to design a PCB that allows me to rapidly charge/discharge capacitors. I would like to use a PIC to control MOSFETS that open/close voltage inputs from an external power supply to capacitors.

I thought about using this scheme for the switch:

... but I am not sure if this is a good approach since I would need a high OHM resistor to charge up my capacitor quickly (reduce drainage as much as possible) and to avoid excessive currents, but then on the downside, it would also slow down the discharge rate of the capacitor.
Hence, I was wondering, if someone knows a better approach of how to deal with such switching?
EDIT
Based on the comments and an answer, I tried to implement the two-MOSFET switch, as suggested:

Unfortunately, I must have done something wrong with my setup. Have a look at the transient analysis plot: The capacitor does not seem to be completely discharging.

The TINA simulation file can be downloaded here
EDIT 2
Another switching scheme that seems to work this time:

Here is the result:


texts:
Is there such a thing as connectors that sit flush on a rounded surface? Like a crescent shape. Or a flexible connector that would adhere to a rounded shape?

For example, I have a pole with a sensor on the end, I'd like a connector that sits flush on the pole for easy removal instead of a fixed wire running along it.

If so what is the name of such connectors?

I've added a crude drawing, as per request, I'm terrible at anything visual like that.


texts:
I am modeling Digital Circuits using ICs in a software. I have worked with flip flops and counters, but I don't remember it well.
How do I model undefined or initial value of flip flop (SR or JK etc.)?
I have three options

'0' state for all uninitialized nodes
assign random value '0' or '1' to the new node
generate error message, & ask user to clear or preset the flip flop

Also consider a JK flip flop, if the user input is '0' & '0', the output is 'Q' & 'Q bar'. What value do I assign in this case? '0' & '1'? This is the initial case, i.e the circuit has been made & the console just powered up.

Please share your experience.


texts:
I have GNSS device that outputs

NMEA messages via RS232
PPS signal via a digital out (TTL)

I need to distribute both the RS232 and the PPS signal to more than 1 system (currently 3, but could be more in the future).

For one system (typical PC or embedded board) I need to even include the PPS also in the DB9 connector (PPS to the Carrier Detect pin). An indication of the architecture below:

Is there a cheap DIY solution for distributing (i.e. splitting) those two outputs and keeping signals "intact"?

E.g. for distributing (or splitting) the RS232 I think a solution like this would be more than enough, right?
What about the PPS signal? How should this one be distributed? I have found many commercial solutions (e.g. this) but those are expensive for our project.

Thank you!


texts:
I'm designing a light switch that will be controlled by a uC. The problem is that the uC will be connected to a coin battery cell (3,3v) and he can't waste energy in the switch circuit. So what would be a design that would have a low power consumption in the activation switch?

The light will be connected to the grid and it will draw a maximum of 10A.


texts:
I am considering implmenting an home automation system around my Raspberry Pi but I found the price and space requirement of inserting a Pi every place some control is required too much but the Cat5e cables required for this design is already installed during renovation. I have some PCF8574's, PCF8591's and SSRs lying around so is it possible to drive them using Cat5e cables?

All my Cat5e cables are already wired with TIA/EIA 568B pinout. They are part of my structural cabling and are not shielded, so higher line voltage is required. I am thinking sending power and I2C lines over the cable, with this pinout:

Pin 1 (Pair 1): SCL+
Pin 2 (Pair 1): SCL-
Pin 3 (Pair 2): SDA+
Pin 4 (Pair 3): +12V
Pin 5 (Pair 3): +12V
Pin 6 (Pair 2): SDA-
Pin 7 (Pair 4): GND
Pin 8 (Pair 4): GND

The power pin arrangement is same as 100BASE-TX PoE wiring so power rating will be the same too, and using of bidirectional differential signaling is found in 1000BASE-T which requires Cat5e.

Original I2C SCL and SDA lines are derived into two bidirectional differential pairs at TTL levels (the open-drain is not kept on the wire, but restored in the line termination/level shifting device that I am designing)

Any suggestion on that? Also, which chip should I use to convert I2C lines to the differential signalling? Please suggest chips with DIP through-hole option to me. I do not know how to handle SMT stuff.

EDIT

I found this chip, SN65LBC180, is it a good choice? How to wire it into a bidirectional unit? How to shift level (it is a BiCMOS part requiring TTL level but Pi drives at 3.3v CMOS levels) and make it open-drain-compatible?

EDIT 2

Commenters suggested RS-485 which appeared acceptable to me, but still the two differential pairs are required to be bidirectional and only two bidirectional differential pairs only. I am repurposing existing Ethernet cables.

EDIT 3

Since someone brought it up, I cannot use CAN. There is no way I can fit CAN onto RPi without sacrificing anything (SPI is occupied by a touchscreen, so no SPI to CAN converter)

I am aware of the limitation of I2C PHY so I am essentially trying to fit 1000BASE-T PHY to it - bidirectional differential signaling for SCL and SDA signals, but on top of that runs I2C protocol.

EDIT 4

A new chip came to me: NXP P82B96 which splits I2C into 4 unidirectional lines, which in turn can be used to feed into SN65LBC180 through opto-isolation (Pi-side only) to form a 8-pin long-distance-ready signaling. Now I just need to figure out how to get power through the wire, or how to determine if the bus is sending and make the pairs bidirectional.

EDIT 5

From the suggestions of answers, I think I need to change the power pinout a little:

Pin 1 (Pair 1): SCL+
Pin 2 (Pair 1): SCL-
Pin 3 (Pair 2): SDA+
Pin 4 (Pair 3): +5V
Pin 5 (Pair 3): GND
Pin 6 (Pair 2): SDA-
Pin 7 (Pair 4): GND
Pin 8 (Pair 4): +12V

I2C differential signaling voltage is TTL. The +5V over pair 3 comes from the Pi, unbuffered but fused. The +12V over pair 4 may not be present is only used to drive some high-power devices. If needed the device may use its own power supply and leave both rails hanging unconnected or supply its own higher voltage but use the 5V rail.

SCRATCH THAT

Pinout is still my original design, which is 802.1af compatible.


texts: Connecting a galvanometer directly to a microcontroller's PWM output

texts:
Is it a good idea to connect a galvanometer (100 µA panel meter) directly to a PWM output of a microcontroller (or any other digital device for that matter)? I set PWM frequency to approximately 10 kHz and duty cycle varies from 0 to 6% for full scale.

My worry is if the push pull output has a dead time, then the inductor will induce spikes on the driver pin. Does it require extra Schottky diodes to the power supply or are the internal protection diodes sufficient?

I have the diodes lying around, it is not a matter of cost, it is a matter of what is best / necessary practice?

Another option would be a 27k resistor in series and use full 0 - 100% duty cycle, but the question remains as the inductor acts as a current source and "doesn't care" about a series resistor.

®Stellaris LM4F120H5QR Microcontroller


texts: Output receiving GND by activating the transistor

texts:
The base of my transistor is activated with a positive signal 5v. I need that when this happens my output OUT receives GND, but I do not know if I should connect OUT on the collector and GND on the emitter or the opposite GND on the collector and OUT on the emitter. Usually my output is connected to a pull-up resistor.

simulate this circuit – Schematic created using CircuitLab


texts: Diodes, their use in mixers and taylor approximation

texts:
In https://en.wikipedia.org/wiki/Frequency_mixer#Diode, it talks about diode's current-input voltage relationship, and using Taylor approximation of e^x demonstrates frequency mixer abilities.

But this works only if input voltage is small. But I also heard that frequency mixers can operate for large-voltage signals. How is math being done there?


texts: Are transient suppression diodes necessary for a battery powered system?

texts:
I've seen on designs where there is a TVS transient suppression diode on the voltage supply. For example, when the voltage supply is say a wall plug.

However, are such diodes really necessary in a battery powered system? I can't think of any way where the battery supply could "overshoot" the rated voltage.


texts: I want to power up bluetooth receiver module (input voltage 3.7) and audio amplifier module which accepts only 2.4 - 3.7 voltage, exceeding which already burnt the IC. So i got new one. I'm having 2 x 4300mAh 18650 battery which gives 3.7 voltage each. When i connected both batteries in series and connected both modules in series, (i thought the voltage will split up, but as i already mentioned, it burnt the amplifier(PAM8403) IC). Since i'm very new to electronics, i somehow figured out resistor (V=IR) will do the job but i don't know how to calculate the required resistance.


texts:
I am trying to wire this rotary cam switch to spin a DC motor forward and backwards based on the UP and DOWN setting. I am having a really hard time trying to figure out how to wire it. Can someone please give me some advice?  I have a power supply, DC pos and neg. And a motor. Which terminals should I plug the motor in, and which terminals should I plug the power supply in?

I have been trying to test with a multimeter, but the cam is spring-loaded so it is making things difficult.


texts: Why did this Sealed Lead Acid battery blow its vent?

texts:
So I plugged in my new nearly full charge SLA battery (12 Ah) into a new charger designed for 12V batteries and within about 30 seconds the bottom blew out a corner, which I assume was the vent, out came about 15 drops worth of liquid which I assume is battery acid. This is an AGM Deep Cycle by the way.

This is my charger: Amstron 12V / 3A SLA Battery Charger - LC1-12-3A

I read online that the charger gave it too much power, but this charger is rated for this battery. What went wrong? I measured the battery the day before, brand new with no charging done at almost exactly 12 V.


texts:
I'm helping a friend make a 48 inch hot-wire foam cutter. He would like it to be as economical as possible, so I'm giving him two 15V 1.1A wall wart power supplies that I have sitting around.

I don't think the voltage will be enough to heat such a long wire.

Is there any problem with wiring the output of the two wall warts in series to obtain a 30V output?


texts: Why are these traces shaped in such way?

texts:
Please look at this image(see the PCB traces within the circles).

This circuit belongs to a laptop adaptor.

What are those parallel soldered-traces on the PCB traces?
Why aren't they soldered to the soldered legs of the components?


texts: Is this LED slow, or am I measuring it incorrectly?

texts:
I am attempting to turn white light LEDs on and off at a very high speed. Here is a link to the LED being used.

https://www.superbrightleds.com/moreinfo/through-hole/5mm-white-led-75-degree-viewing-angle-4500-mcd-rl5-w4575/253/#tab/Specifications

To measure the rise time of the signal, I am using a New Focus Model 2001 photodiode connected to an oscilloscope. The photodiode is supposed to be able to adequately receive signals of up to 100 KHz+. However, when using a square wave function generator (HP 33120A) on my LED, the signal "shark fins" and takes 30 to 50 microseconds to reach peak value. At about 10 KHz. the signal begins to flatten out, seemingly indicating that the rise and fall time of the LED are possibly slow.

My question is three-fold:

1) Is this LED exhibiting a slow rise / fall time?

2) Do you have any suggestion for a fast (low rise / fall time) LED?

3) Is there a better way to measure the rise time of an LED?

Thank you in advance!

Edit: Some additional info.

Function Generator: HP 33120A

Oscilloscope: Tektronix TDS 210


texts: 2N2222A Mismatch between emitter and collector

texts:
I am trying to figure out what is going on here.

I have a simple circuit to send current to a brushless fan running at 12V on the high side, using a NPN transistor 2N2222A:

This is the picture of the datasheet for the pins:

If I set up the circuit for a quick test, it seems that the datasheet (or the transistor) has the pins swapped.

When I apply a voltage between the pin 1 to 3, as soon as the voltage rises over about 8V, the current starts to flow, even when the base has no voltage (pulled down or floating), and the transistors gets pretty hot. It looks like a "diode".

If I rotate the transistor 180°, everything works as I would expect, current flows, and the fan power is proportional to the base voltage.

This is the pic of the transistor, as I understand that it should work, but it doesn't (it is always 'on' with 12V between the collector and the emitter with the base floating).

What do you think? Am I missing something here?


texts: Why are NAND gates used to make AND gates in computers?

texts:
Why is this a standard for AND gates

when it could be made with two FETs and a resistor instead?


texts: I am building a battery powered trike. My battery is 72v. I have a three position key switch ( off, on, accessory) I have purchased a 72v contactor coil to operate my dc controller, the controller is rated for 0v to 100v. My confusion is in the switch, the switch is rated at 28vdc. My question is:Can I use a voltage divider to drop to 12 volts, and then go through my key switch using the 12 volts to turn on the contactor to supply the 72 volts to my controller? My knowledge is limited on the types of components needed to achieve this and I did not want to burn up the switch with 72 volts. I also failed to mention that my battery does go through a  30 amp breaker on my positive line, before the contactor. Any help would be appreciated.


texts: Accelerometer acquisition, filtering and treatment on Pic

texts:
I've been asked to experiment with dynamic testing.
Using accelerometer and strain gage bolted onto a metallic pipe,and hammering it ( the pipe ) I need to show out force of the impact, and displacement of the pipe, in fact sinking in the ground.

There are already systems doing that but it's out of budget and for big pipes.

Strain gage is used to get force of impact and can deal with that.

But for accelerometer, I'm a bit lost.
One full impact recording seems to be close to 50ms.

So I'd need help to point me in the right direction in order to get displacement from accelerometer recordings.

I know how to condition sensors and record data... but next I'm lost :)
I should integrate 2 times the accelerometer data in order to get displacement.
That's the hard part for me, as I have never done that using pics, only analog OP AMPs long time ago.

So what kind of integration works best for that type of job ?

Thanks a lot


texts: Turn on a microcontroller using a high-side Mosfet switch

texts:
I am using a P-Channel Mosfet to control the power of an STM32F103VETE ARM microcontroller (MCU1). The source of the Mosfet is connected to 3.3 V and the drain goes to the MCU1 Vdd pins. The gate of the Mosfet is controlled by another microcontroller (STM32F030RET (MCU2)) which is directly connected to 3.3 V net.

Now the problem is that I can't turn off MCU1:

When I put a Logic 1 on the gate of the Mosfet, that makes its Vgs = 0 but I still get 2.4 V at the drain of the Mosfet which is enough to turn on MCU1.
When I put a Logic 0 on the gate of the Mosfet, its Vgs = -3.3 V, it turns on properly and I can read 3.3 V at the drain.

Can anyone please help me to solve this? What can cause such a problem?

Here is the schematic of the circuit I have used:

"POWER_ON" is the signal from MCU2. The Mosfet is STS3DPF20V.


texts:
Possible Duplicate:
  How can I use a 12 V input on a digital Arduino pin?

I want to measure a car battery voltage (range is between 10-13v). But my AVR accepts analog inputs from 0-5v. How can I make the input voltage lower so I can measure the 3v voltage difference (10-13v) in around 1024 steps (0-5v from the microcontroller).

Basically I need a voltage step down converter that works linear, the ones I know only give out a fixed voltage (5-20v converts to 5v always like the 7805).

I don't want to use a voltage divider because then I can never get that 3v resolution I think.


texts: Help with analysis of a signal that generates high frequency

texts:
I am trying to understand this circuit:

In circle 1: I don't know why we make two capacitor in noise circuit, we can't do just one?
In circle 2: The tuned circuit consists of capacitor C1 and inductor L1. This tuned circuit will act as an oscillator with zero resistance. Why we do the capacity and the inductance with transistor Q1 and how we generate frequency because we have just DC voltage?


texts: Is this a transformer, a choke or something else?

texts:
I thought that the component which is shown in the following picture is a transformer. But when I opened it I saw that the end of the coil on top (with thicker wire) was soldered to the beginning of the coil beneath it (with thinner wire). The three pins on one side were from to the coil on top, and the other two pins came out from the second coil near the end of it (both pins).

Its size is approximately 3 cm x 3 cm x 3 cm. It's from a circuit which turns on a 60 cm long 20 Watts tubular fluorescent lamp by a 6 V battery. Both of those two pins on one side are directly connected to one side of the lamp (apparently for preheating).

So what is this component and what does it basically do?


texts:
I'm trying to measure the voltage of a powerbank. When I connect the multimeter to its output it displays 5.26V. But after around ten seconds the voltage drops to 1.12V. When I disconnect the multimeter and connect it back again, the sequence repeats itself.

Why is it happening? And more importantly, is it possible to make the powerbank always provide 5.26V?

Perhaps the powerbank senses that the multitool does not represent a proper load and issues some kind of power saving mode?


texts: Using a DC-DC step up converter with small solar panel

texts:
I have a small solar panel that I would like to use for charging phones or other small devices.

Goal: 5v output

The panel has an Open circuit voltage of 1.8V, Short circuit amperage is 4A. (The amperage is closer to 4.5 but I don't remember the exact measurement)

Most of the off shelf converters I have found only get to 500 milliamps. I'd like to get, or make, a converter that could output 1000ma continuously.

Any thoughts are welcome.


texts: How to measure very low current by amplifying it?

texts:
I am trying to measure current from a DC circuit. So it basically I am trying to make an ammeter. I am using ACS712 20A current sensor and Arduino UNO. Theoretically, I can measure a minimum of 50 mA current using ACS712 20A and a 10-bit ADC (built-in with Arduino UNO). In practice, however, it may be 150~200 mA due to noise. My problem is that I want to plot a characteristic curve of a transistor for that I need to measure current in the microampere range.
My idea is to somehow amplify the current and then measure it using the existing setup. For example, if there is a 10 micro ampere current in my circuit, then I will place a black box in front of the ammeter that multiply the current into a factor of 10k. So, the ammeter would measure .1A or 100mA. Likewise, a 12 microA current would be amplified to .12A or 120 mA.
Now, is it possible to build such a black box? The black box can contain its own power source or anything! I heard that transistors can amplify current. How can I connect the transistor so that I gain such current?
I do not have prior experience with electronics. I only took freshman-level physics courses. So, if some parts are unclear, I apologize. I will try to provide clarity in the comments in case you ask.


texts:
LEDs are known to have a very low, unnoticeable power-cycling latency, but how fast are they when measured? (nanoseconds?)

In other words, how long does it take for an LED which is entirely off to get to its optimum brightness, and how long does it take to go from full brightness to off? I assume that the current applied makes a difference?

I ask this since modern LED-backlit monitors use PWM to achieve different brightness levels, and even in backlights which flicker at thousands of Hertz, LEDs seem to respond almost instantly (unlike CFLs, which are rather slow in power cycling).


texts:
Howcome when I try to find Rthevenin for Part A, the resistors in the loop L1 are completely ignored? Does current not flow in L1 in this case?

Req = 60||30 ohms is the answer btw, giving us a time constant of 120uS.


texts:
The polygon tool can be used to create power planes. This is the common use of it and I am not aware of any other application of it.

When power plane is created, we name the plane to have same signal name as the ground signal. Once the plane is drawn and we click rat's nest, the signal paths are made distinct from the plane by removing the copper around edges of the signal trace. The copper plane swamps any signals with same name as the plane itself.

I have 1 question:

If I create two small planes and then a big plan that then overlaps both of them, how do I keep them seperate? What I want to achieve is below. The blue color is copper. There are two small planes inside a big plane. I don't know how to achieve the white seperation. It seems that pressing rat's nest does make signal trace distinct from power but not overlapping planes.


texts: Tradeoffs and design considerations when choosing a crystal + PLL combo for MCU timing

texts:
I am in the process of doing more work on ARM platforms (specifically for this example the Atmel SAMD10 Cortex M0+ line). The clock flexibility and lack of ridiculous fuse settings feels like a (very much overdue) breath of fresh air.

However, I am completely ignorant as to the design compromises at play when considering which crystal frequency to choose and how much to then use the PLL to achieve my target instruction clock.

As an example, let's suppose that my main instruction cycle limitation is that I want to implement a 5Mbps UART using the SAMD10. I want to ensure that instruction cycles are ideally an integer subdivision of the UART bitclock. So I might choose a 20MHz crystal with no PLL multipler - 4 instruction cycles per UART bit and 0 error (theoretically).  This all seems fine - 20MHz is a very common crystal value, which should mean good availability and low cost.

But then again 32.768kHz is pretty common - and it seems logical that the crystal oscillator might draw less current at a lower frequency - but I would then need a 1525.9x PLL multiplier to get a 50MHz instruction clock (the fractional PLL outputs only between 48MHz and 96MHz on this MCU). Would this give me worse timing jitter? Is a 1525.9x PLL multiplier big, or well within what you should expect to work for a modern MCU?

How do others choose their crystal / PLL multiplier values in a situation like this?


texts: Difference between 2-way and 4-way caches?

texts:
I don't fully understand this picture:

If the data and instruction caches are separated, doesn't that mean that this CPU is not von Neumann model but Harvard model?

And what does it mean that one cache is 2-way and one cache is 4-way?


texts: Driving a 50W LED from 10 rechargable batteries (XL6009 converter @25% efficinecy)

texts:
I want to power up for a few minutes a 50W LED (37V at 1.5A) from batteries. I have a bank of 10 NiMH rechargeable batteries (total of 12.9V), each in the 2.1-2.5Ah range.
I use a DC-DC step up convertor with XL6009 to increase the voltage (made in China, 5euro, Amazon).

I KNOW that I need constant current not constant voltage! This is just an experiment to see if the batteries can keep up for 15 minutes or so.

The convertor is sucking about 2A from the battery bank but it only outputs 0.22A 24V. Why? I was hoping for an output of at least 0.5A. The LED is bright but the radiator is not even getting warm.

The batteries can deliver OVER 4A in shortcut, for a short while.

Summary: the converter draws 10V*2A and outputs 24V*0.22A. Efficiency: 25%!


texts: 18650 Samsung SDI cell to replace smartphone battery

texts:
I've bought a cheap phone (5$) to be a WiFi hotspot and nothing else. Now, the battery is dead. It's a Li-Ion unit, 3.7V nominal (Sony BA900).

Since I do not want to spend any more money I was thinking to crack the phone open, solder some wires on and use a 18650 cell instead of the phone battery.

What worries me is the charging circuit. Does the circuit have current sensing and current limiting to charge a 18650 nicely and keep the magic smoke inside the charging IC? Does battery capacity affect charging?

The 18650's are Samsung SDI branded cells.

Would such a contraption work? Anyone tried such a thing?


texts: Disable RC oscillator in ATmega328 for FCC compliance

texts:
With respect to the topic below, I was trying to find where in the AVR documentation does it say the 8 MHz RC internal oscillator is "disabled" when CKSEL is selected to a different source? I am working with a Atmega328p.

FCC Low Oscilation

Specifically, if CKSEL only changes the MUX input (figure 6 of atmega328 datashset), but the 8 MHz interncal oscillator is still going (just not being used) then any AVR chip in that family is not exempt under the FCC part 15 exception h. (for digital devices with clocks that produce/use frequency under 1.705 MHz powered by a battery.)


texts: The I²C protocol allows, in theory and with 7-bit addressing, up to 127 devices to be connected to the master. This is a large number, so why would any low-cost microcontroller (e.g. this PIC24), have more than one I²C port? Why is it needed?


texts: What do the capacitors on IN and OUT of an LM7805 voltage regulator?

texts:
Please understand that i am actually a really beginner in electronics.

I found a really nice topic on how to create a 5V DC from a 9v power supply. All is ok. But in order to smooth out ripple, the author use two capacitors in order to smooth values before the voltage regulator, and add another after the voltage output pin.

What I don't understand is that the capacitor seems to be placed in parallel with the voltage regulator. Not in serial manner like I was expecting to see. So I really don't understand how you can use the smoothed output values, since in the circuit diagram, it seems that the direct output goes to the ground.

I know that when capacitors are in series, you add their values. But the input pin of the voltage regulator seems to be on one terminal while the capacitor is on another. How can the voltage regulator benefit of the capacitor?

I know that what I say is plenty wrong, and the circuit diagram is correct. But I can figure out how this circuit is working?

Here is the schematic.

By the way, do you know where can I find tutorial explaining how to read schematics? There is lot of topic explaining electronics but I haven't found any valuable link for electronic circuit explanation.


texts:
Yamaha InfoSound and ShopKick application use technologies that allow to transfer data using ultrasound. That is playing an inaudible signal (>18kHz) that can be picked up by modern mobile phones (iOS, Android).

What is the approach used in such technologies? What kind of modulation they use?


texts: Calculating Voltage Drop over a transistor

texts:
I have the circuit below with a Bipolar NPN transistor

I have a whole bunch of currents measured with the Amp Meters for various different resistances. How do I calculate the drop in voltage across the transistor eg Vbe Vce and Vbc?

Fundamentally I dont understand how to apply circuit laws to a transistor? Is it in series or parallel to the resistor?

Feel free to just ignore the LED.

Thanks everyone for your help. I have a data sheet, my transistor was 2N3904 https://www.sparkfun.com/datasheets/Components/2N3904.pdf which gives me some rough approximations of the values, at various currents. My LED was red.Is there really no way to look at the circuit and write the Transistor voltage drops in terms of each other with circuit laws? I  What I don't quite get is if I look up Vbe in a data sheet how will I get a variation in current and be able to put it into any equations?  Basically I wanna is graph the Ebers-Moll relationship and compare it to my empirical data, but the Ebers molls equation is in terms of Vbe and Vce. So if I just have some constant value Vbe= 0.7 I will get a flat line.

I know the relationships

Ib + Ic = Ie which if we want to approximate Ie = Ic
Beta * Ib = Ic  but none of this gives me anything about the voltage.

My best guess is that Vr + Vbe = Vce + Vled = 5 where Vr is is voltage across resistor.

So I have Vbe = 5 - R * Ib?

Does this sort of logic work?

The approximated Eber Molls gives Ie = A(e^(Vbe/kt) -1)= A(e^((5 - R * Ib)/kt) -1) so Ie should be exponentially related to Ib. But this isnt getting me anything close to my actual values.

This is what my data looks like. I am looking for some explanation as to why beta stops being linear and some formula to compare this to.


texts: What could cause a sin input to turn into a square wave across a non-inverting amplifier?

texts:
I've been working on a small non-inverting OPamp circuit with a single supply and have run into a problem. The circuit uses the LT1022 OPamp and is setup like in the image below:

The goal is to amplify a small 20mV signal to about 2 Volts. Ideally more, but the maximum gain I can get out of this circuit is about 20, giving me a 400mV resulting square wave.

Yellow is U1-, Purple is U1+ and Blue is U1 Out. Supply voltage doesn't seem to be the problem here. Dropping PWR down to 10V or bumping it up doesn't have any effect on the waveforms. What strikes me is that U1 Out seems to be limited to a very small gain and quickly bumps against some sort of ceiling. I've tried a few different values for R4 but with very little effect.

What could be causing this behavior?


texts:
I'm working on a project involving a bunch of daisy-chained WS2811 lights and I'm noticing significant flickering on the ones at the end (lights #16-30 in a chain of 30).

Right now, the circuit is a 3.7V lithium ion battery connected to both a 3.3V Gemma Arduino and also in parallel to the lights. I'm using thick 16 AWG stranded wire to run big "central lines" for power and ground and then soldering smaller 22 AWG wire from those central lines to the individual LEDs. At peak, the longest cable run is about 4 feet from the battery to an LED.

The data lines are obviously daisy chained to each other, and I have a 330 Ohm resistor between the data line and the first LED as recommended by Adafruit.

Here's a video of the flickering.

Any idea what might be going on or how I should debug this?

Thanks!


texts: It's possible power a small calculator with a small power extracted from the EM Atmosoherical Noise?

texts:
I'm building for a physics exhibition a small circuit able to extract from a
very long cable antenna (10 meter, 20 if necessary) a tiny amount of energy sufficient to power a tiny calculator.

The circuit i've seen on the web is:

The compoments are:

C1 and C2 200nF 50V ceramic capacitors (x2)
1N34 germanium diodes (x4)
C3 and C4 100μF 50V electrolytic capacitors (x2)
and obviously a very long antenna.

Also a extra RLC on the output as "Joule thief" is a possible additions.

My question is, this method and circuit have the potential with a single cable antenna long in the order of 10-20 meter to power a small calculator?

If yes, there are some ways for increase the efficiency of the circuit (obviously within the scope of the experiment)? For example a way to focus the system on high power frequencies as radio freq.
If no, there are some ways, even alternative, to power a small calculator without direct alimentation? I accept every suggestion.

PS: No conspiracy theory thanks


texts: How can I control many LEDs with just a few pins on my micro?

texts: I am using an Atmel ATtiny13 which has a 6-pin I/O. I'd like to control about 15 LEDs but am unsure how to connect everything. Without multiplexing of any sort, it seems I'd only be able to control 6 LEDs at a time. Am I limited to only 6 LEDs because of the size of the microcontroller?


texts:
Most of the circuit I understand but there's a few things which I don't get.

First, at the bottom corners of the page, theres an open circle connected to ground. What does that mean?

Second, near the third op amp from the left, there's a wire that points back at itself. Does this mean it is in a loop? What does that achieve?

Third, near the top left corner, there seems to be a little bump where V(a) intersects with the wire. Does this mean anything?

Also, the switch near the bottom right corner, is it necessary for this circuit to work (as an ecg amplifier)?


texts: How to provide power to Arduino after a remote button is pressed

texts:
I have one of these IC 2262/2272 Wireless controller and receiver. If managed to connect it in such way that the Arduino blinks a LED after a button is pressed, it works fine.

My question is, is it possible to power up the Arduino - allow for power go to it, after I've pressed a button ?

The final product I'm aiming to build is a remote controlled car alarm, that will check for pressure changes and text/call me if such are detected, when armed.
Ideally I wouldn't want to have the circuit run constantly as when it's checking only once every 10 seconds for pressure change and tehre's no GSM shield connected yet, it went trough a 2000-2600 mAh (Not original and a bit used so not sure the exact number) portable battery in 20 hours, so letting it run isn't great for my car battery.

I'm pretty sure this question is more for this Stack as I'm asking how to essentially power the Arduino on demand, and not anything else Arduino related.


texts:
When dealing with carry-look-ahead adders, the following expressions are commonly used:
$$P=A \oplus B$$
or
$$P = A + B$$
I understand that using the second expression takes less gates for calculating the propagate signal. When computing the final sum
$$S=A \oplus B \oplus C$$
where C is the carry from the previous stage, the sum expression contains the first expression. Doesn't this mean that using the first expression saves gates without causing extra delay (because that expression has to be calculated anyway for calculating the final sum)?

Therefore, why is the second operation sometimes used as well?


texts:
In my circuit I need to discharge a capacitor into an inductive load using SCR. In order to make the circuit oscillate there'll be a diode antiparallel with the SCR, as you can see in the picture.

My plan is to let the circuit oscillate only one sine wave cycle and then stop (I'll turn off the SCR as soon the current stops flowing through the SCR and starts flowing through the diode).
My question is: do I need to use a snubber circuit parallel with the SCR/Diode to protect it from voltage peaks?
I know that snubber circuits are needed for switching, mainly when the load is inductive, but in this case there's a diode that can conduct when there's reverse voltage peaks, as far as I understand.
I've tried to simulate it but the results doesn't make much sense to me.
Consider the capacitor is charged when the SCR is triggered.

Thanks!


texts: I'm having difficulty interpreting the dimensions on TI's mechanical datasheet. The part below has 16 pins spaced .5mm apart. However, I cannot determine what the length and width of the pins are. Width is written as "16X 0,30/0,18" and length as "16X 0,50/0,30". I don't know what the dimensions in the numerators and denominators represent. I thought they might be uncertainties, but the values seem too large. I haven't been able to find a guide to reading the mechanical data on TI's website.


texts:
I am new to the STM32 world. I am using [STM32F407VG]1 (100 Pins pkg). I have to select an 8-bit port for connecting 8 digital inputs to the MCU.. but the datasheet shows so many alternate as well as additional functions on each pin that I am confused as to which pins i should select. Is there any SOP about how to select appropriate pins when multiple options are available for pin assignment?

edit:

Regarding Alternate Functions on port pins.. for example TIM1/2 alternate functions can be assigned on Port A, B or E.. Are all assignments of Alternate Functions equal or is there any more preferable port for peripheral alternate functions.. as in the case of TIM1 are all the Port A, B or E assignments would be same in all respects or will there be any difference from one case to the other?


texts: Why radiowave cannot pass through steel mesh？

texts:
I cannot understand the reason for cutting off radio waves with metal mesh.

I do not understand the theory that holes are small enough for wavelengths .

I think the wavelength is vertical to the hole, but is it related to the size of the hole in the horizontal direction?

The amplitude of the wave of the radio wave is also a story in the electromagnetic field, so I can not tell if it can be passed with the physical size of the hole or not, so I can not understand it well.


texts:
...and a few other things. I am working my way through Geoffrey Brown's book Discovering the STM32 Microcontroller and it's largely been smooth so far. I've come across an exercise where the reader can try to read/write to an EEPROM over SPI. I've had the SPI interface working in loopback, although last night when I was testing it, I noticed that on the logic analyzer I was seeing the NSS pushing high before the message was complete. Then in the morning, no changes, everything is working fine again. OK.

I set up everything to read/write the ROM (Micro 25LC256) but the signal I see on the analyzer isn't what I am expecting. I see the NSS pushing high from time to time in the middle of communicating. Further, the clock looks inconsistent and the data looks wrong, and the analyzer is giving me a ton of errors.

I thought, OK, I will take off the NSS altogether as the ROM is the only thing hooked up anyway, then it will stay low and I can check it out. But still the clock looks wonky... I'm just getting started with this stuff, but I don't have anything adjusting clock frequency at all, so not sure how thats changing? The code can be found here, and I think it's quite simple. most of the important logic looks like

  // Drop select level low then send the write enable flag
  GPIO_WriteBit(EEPROM_PORT, EEPROM_CS, 0);
  spiReadWrite(EEPROM_SPI, res, cmd, 2, EEPROM_SPEED);
  GPIO_WriteBit(EEPROM_PORT, EEPROM_CS, 1);
  Delay(1); // Debugging aid, Wait 1 ms to make analyzer easier to read

I have all the speeds set low (the SPI CLK/MOSI/MISO are 72 / 64 = 1.125 < 10Mhz = 25LC256 max speed and the GPIO I'm using for NSS is 2MHz), and I put in a delay of 1ms between operations just to make it easier to read on the analyzer, it doesn't seem to affect the output.

Here is a capture of the analyzer data with the NSS forced low (unplugged):

Zooming in on the first pulses I see that the clock width is all over the place, doesn't look like CPOL/CPHA = 0/0 to me, and doesn't look like it's sending the write enable value WREN = 0x06 = 0b0000 0110...

...and it doesn't seem to get better...

And one last one that shows the NSS pushing high for no reason

How do I debug from here? Is there something obvious that I'm overlooking?  Is it common to have such bad looking timing problems?  Thanks!


texts: What is the purpose of clamping the gate and source of a mosfet

texts:
Is clamping the gate and source of a MOSFET really important? I have seen this in some articles and some datasheets of MOSFETs where they have built in clamping.

As far as i know they are used for ESD. Asuming that the gate is just a trace to a controller device I don't see potential danger of an ESD especially when the cicuit you are going to build on has a case.

So do I need them? Are they critical?


texts: Difference between HF Communication and VHF Communication

texts: I am new to Radio Communication. I don't understand what was the challenge in establishing VHF Communication system w.r.to HF Communication System that made the former one to arrive later. (Talking as per the order of development of Aeronautical Communication System)


texts: Can I in any way connect +ve side of my led to uln2083a output pin?If no can I do it with M54562 transistor array?

texts: I had conneced my digital pin of arduino to the uln2803a to drive LED.  I want to configure my uln2803a such that i can connect +ve side of the led to the output pin of uln2803a IC.


texts:
I have attached my current state of VCC routing of ATmega32u4.
I think I am seeking for some general advice on how to tie the VCC pins together.
Is this an acceptable way to route the pins? Sorry for such a vague question.
Routing was done with little background. I am sure there is room for improvement.


texts: What is the maximum magnetic flux density a HDD can tolerate before data is corrupted?

texts:
Does anyone have hard numbers explaining the maximum number of Teslas a hard disk drive can tolerate before data will be corrupted.

This forum says "a lot", which isn't super helpful.

This one claims you need magnets that only governments have access to in order to erase data, but I'm concerned with what it takes to corrupt data, not completely erase it.


texts:
I have a keyboard from an old Silent 700 TTY that I'm trying to bring to life.  The problem is that each individual keyswitch appears to be a hall effect sensor.  There are no part numbers; the chip dies are individually bonded to the carrier boards.

Here's the switch.  The carrier board fits into a slot in the back of the switch in the orientation shown:

And here's the die:

Does anyone have any thoughts on how to drive a switch like this?


texts:
I am building a basic relay driver circuit using ULN2803A. I have attached the basic circuit diagram, i would like to know if i am missing anything. I am Planning to use it with HLKPM01 5V Power supply with this circuit.

After quite a bit of reading on the internet, it seems ULN2803A drops a  large voltage across and thus using it with 5V power supply, the relay will be fed only 3.5V. How to overcome this issue ?, i am quite new to electronics engineering, thus request some assistance from fellow makers.


texts: Gas discharge tube and IEC class II device

texts:
I'm looking at a design for a IEC class II device, and can see that there is a Gas Discharge Tube being used for suppressing high voltage transients/surges. Since the device doesn't have an earth return, my gut reaction is that this is not a good idea (or wonders exactly what benefit it brings), and that if this is done then everything sharing the ground the GDT shorts to needs to have appropriate isolation from any conducting part or chassis.
Is this the proper use of a GDT when there is no earth return? What benefit does it bring in this case?

simulate this circuit – Schematic created using CircuitLab


texts: Definition of quality factor as function of frequency

texts:
I have seen that some electrical components (which contain R,L,C elements) datasheets shows the curve of the quality factor Q with respect to frequency, and not simply its value at the resonance frequency. For instance, this is the curve we find on this inductor datasheet of an high frequency inductor:

Now, the definition of the quality factor is this one:

At resonance the energy stored in the equivalent RLC circuit of the component may be evaluated as the maximum energy stored in the inductance or also as the maximum energy stored in the capacitance during a period, since at resonance both quantities are equal. But how we evaluate the energy stored for a generic frequency? I'd say that in general, the energy stored in the magnetic field is different from that stored in the electric field, if we are not working at resonance.


texts: What is the purpose of the SCR in this circuit?

texts:
I am trying to repair an old SMPS. The first step is to reconstruct the schematic and work from there on. The schematic on the low voltage side is completed for the +12V and the +5V circuits. However what is the functionality of the SCR and Zener in the circuit.

Since VR4 is a zener I have been thinking of the +5 going up over the
threshold of 6.2V but that would not trigger the SCR.
If the +5V is going down the zener would act as a diode and the SCR would
trigger if the +5V line comes below GND. But in that case the zener functions
as a diode.


texts: Is UL approval at all possible for low voltage USB and network LAN Cat6 patch cables

texts: I am from a European distributor. Some of our customers, who export to the US are asking for UL approved Cat6 and USB patch cables. Is it even possible to UL approve these low volatage cables? i.e is it only mains attached products that qualify for UL?


texts: Physics/chemistry understanding of PMOS and NMOS to form CMOS

texts: Can anyone provide me explanations or links that provide a clear explanation of what atoms/molecules are in p-type and n-type (PMOS/NMOS) and how they interact to create actions?


texts: How does an ARM MCU run faster than the external crystal?

texts:
So before this I only worked with simple 8 bit Atmel MCUs and I realized on my development board schematics it has only a 12Mhz crystal, yet the MCU operates at  up to 100MHz. (I think the default is 80MHz. I only made it higher once for fun. It's just a simple line in the code.)

How does it do that? Why does an Atmega328, for example, run at the used crystal speed?


texts: Please help identify this Siemens TO-92 NEMOS

texts:
This Siemens device, marked "k4 S S 98" is used in place of a 2N4401 NPN.
The 2N4401 NPN is EBC from front, so it must be wired E-S, B-G, C-D.
I spotted this because it was inserted backwards from the silk. Testing it out-of-circuit, sure enough, it is a functional NEMOS.  But what are it's parameters?


texts: How to achive Rser in a voltage in ngspice like in LTspice

texts:
I'd like to add Rser into my V1 like in the image below, but I couldn't find how to do it. I checked the internet, looked at ngspice's manual. I tried adding resistance next to V1 but PP value of out1 reading is 10 although it should be ~9.98 which was measured in LTspice

I appreciate any help. Thanks!


texts: 3.3V UART over 20cm ribbon cable inside an enclosure - EMC considerations

texts:
I am currently designing a device which internally consists of two circuit boards inside a fairly large, grounded metal enclosure. I'm designing one of the boards myself, the other is a bought part which communicates via UART over a pin header connector (ideal for connecting ribbon cable). I'd like to be able to use the 115200 baud speed, but that's not an absolute requirement.

The bought part is available in two versions - one with 3.3V UART and one with proper RS232 voltage levels. Using the 3.3V version would simplify my own board a bit (no need for a MAX(3)232), but I am wondering whether that might have a negative impact on the robustness of the transmission, especially since the device will have to pass an EMC test.

Since I'm a novice electronics designer, I don't have a good intuition for this yet. Do you think the 3.3V level is sufficiently robust over a ~20cm ribbon cable, provided I don't run it right next to the power supply?

Would you recommend putting a ferrite around both ends of the cable? The supply for the secondary board is over the same cable, so I'd expect the sum of currents over that cable to be 0 for all "good" signals, except for high frequency signals, which can run directly to the chassis ground via a 1nF capacitor.


texts:
I am trying to build an audio system . I have a speaker which is rated 10 W and 8 Ohms . I am using a circuit from datasheet of TDA2040 with a pre-amplifier circuit with the microphone . when I connected it on a breadboard it seem to work fine at low volume but when I raise the volume the speaker starts to beep and sounds becomes unclear.

instead of variable 100Kohm ~ 1Mohm variable pot I am using a 100Kohm fixed resistor.I am using a variable pot between the the two circuits to control the volume.I am powered the TDA2040 circuit with 12V 1A adapter and pass the same source through a regulator to the Pre-amp circuit.Are there possible reasons makes the speaker beeps at high volume ?


texts:
The image shows a buffer register as part of an SPI module
Why exactly is a buffer connected to the FIFO registers?


texts:
simulate this circuit – Schematic created using CircuitLab

This is the circuit schematic of an astable multivibrator. I have to chose the resistance value of R3 in order to limit the output current of the OpAmp. The OpAmp model is TL081 Texas Instruments, and this is the link  to its datasheet . I am not able to find any information about the maximum output current in it. Can anyone help me?
I have another question: is there any other reason why the resistor R3 is necessary in this circuit ?


texts: How to conclude if logic circuit with feedback is combinational or sequential?

texts:
In the below figure, the the inputs are a,b,c and d and the outputs are Zo and  Z1.There is a loop in the circuit.

How can i tell if the circuit is combinational or sequential?

edit:
The outputs of interest here are z1 and z2 which are given by:

z1 = (a.b'.d) + (c.b.d) + (b.c.d)

z2 = c + a.b'd .

I have the outputs depending on inputs but can i conclude that it's a combinational ckt ? Is there any concept i am missing to understand?

at the extreme left is the inputs a,b and c in order.The output of 1st level OR gate is z0 and "d" is the input to the 4th level AND in centre. The output of the same AND gate is taken as z1. The 5 th level lower AND gate has inputs "b and c".


texts:
In a circuit I'm designing I want the user to be able to switch the power off and on (with an SPST style switch), as well as depress a push-button (push-to-break) that will temporarily disable the power - effectively a reset button. Ideally I would like to combine these actions into the same physical switch. Does anyone know if such switches exist? What would I search for to find them?

Edit: I would like to combine SW1 and SW2 in the below circuit.

simulate this circuit – Schematic created using CircuitLab


texts: Relation between voltage drop across incremental resistance and VD of diode

texts:
In small signal analysis of diode (silicon) we take voltage drop across diode (VD ) is 0.7 volt. using other data we calculate current through diode " I " and then incremental resistance \$r_d = \frac{nV_t}{I}\$ . As it is a resistance there must be a voltage drop across it which is \$nV_t\$ (constant for a certain temperature).
What is the significance of this voltage drop ?
Does it add up with 0.7 voltage drop ?
Is there any other noticeable effect of this voltage drop ?


texts:
Is it typically advisable to use a voltage divider when trying to achieve a specific voltage in a power supply? I have a 15W +/-12V power supply and I need 10V, so what are the drawbacks of using a voltage divider with, say, 68K ohms and 340K ohms?

And yes, I could get by with a 7810 regulator, but I can't find a regulator such as a 7910 for negative voltage. So I'm looking for other options.


texts: Why JFET is called a voltage controlled device while BJT is called a current controlled device?

texts:
Why are JFET/FET called voltage controlled devices while BJTs are called current controlled devices. Both require a voltage to operate properly. In both an electric field is produced so what is the difference?

Now the question is that current is also generated due to voltage and still BJT is current controlled and FET voltage controlled.


texts:
I came across a problem which I cannot calculate by theory.
How does this circuit with diodes and resistors work?

In the above diahram, I can calculate the current simply by subtracting the voltage drop of the diode from the source voltage which gives 11.4V (the green value in picture.)  11.4 divided by 2k (the total of the resistors) gives 5.7 mA that is drawn and we can work out the voltage drop over each resistor.
The next circuit confuses me.

Can someone please explain how we get the current through every component and the voltage drops? The other thing a normal voltage divider of 1k and 1k, 2k in total on a 12V supply will draw 6mA but in the diode circuit R3 only draws 4.2 mA.


texts: RT6224D-based step down circuit yields 0V - why?

texts:
We received a set of prototype boards. They have a DC power supply input feeding into a step-down converter, which is built around an RT6224D. It is supposed to deliver 5.0V. The circuit is almost exactly straight from the datasheet, just that the designer chose a 3.3 uH inductivity.

Here is what we have:

This is the Typical Application Circuit from the datasheet:

The problem is, I get exactly 0V at the output. And I can not figure out why. Even on a quick breadboard reproduction of the same circuit, I still get 0 output. I have this feeling there must be something very obvious.

Do you have any idea what is going on here? I greatly appreciate your help!

Edit to answer SamGibson's questions:

(a) PCB layout:

(b) The populated PCB, sorry I don't have an unpopulated board:

(c) Someone else did the design and the layout, I am just trying to make it work. The boards came from a domestic manufacturer. I talked with the designer about the issue, he said U6 it must be a faulty chip. On all 5 boards. So I replaced it with a new one, same result.

(d) I don't know where the board manufacturer got the components initially, my replacement was from Digikey.

(e) I can't find any usable signal to scope, VIN and EN are at 12V, all other pins show a flat lines at 0V.

(f) The inductor is an ASPI-4030S-3R3M-T.

Thanks!

Edit 2:

This is my "hotfix" based on the feedback by Randy Nuss and Spehro Pefhany. The originial RT6224D did not work any more, but with a new chip and the 100k resistor, I get the desired 12V:


texts: How do i solve this circuit with Thevenin's?

texts: I am not sure how to place my voltage source after i combine the 2 parallel resistors R1 and R2. Can someone please help me with this?


texts:
I am making a solid wood clock using minimal components. So far, I thought of using 21 LEDs to make 7 segment displays (3 LEDs for each segment (overall 63 LEDs for the displays)), 6 LEDs for the 1 in the ten hours place (it's going to be a 12-hour clock), 2 LED's For the seconds indicator between the minutes and hours, 2 LED's each for PM and AM, 2 Buttons to change time, a PIC16F628A, 3 4094 Shift registers for the displays, a Crystal obtained from an old digital watch, and a couple of extra things.

The first question is: What is the frequency of the clock I obtained from the watch? And will it work well with the microcontroller? What caps should I use along with it? Is there anyway to test to see if it still works?

  The Crystal doesn't have any text printed on it, it's 3mm wide and 8mm high without the leads.

The 4094's datasheet isn't exactly clear to me how to use it, BTW I'm programming using CCS, is there any easy tutorial for beginners on the 4094?

Lastly, what batteries should I use to power it, and how long will the battery last?

Thanks in advance.


texts: Powering Raspberry Pi from multiple DC voltage sources

texts:
I'd like to have some method of powering a Raspberry PI 3b project from a variety of sources, whilst being backed up by a battery:

Internal battery
Car cigarette lighter
Mains (via a DC adapter, like a laptop PSU ~19V)

This is what I've come up with. A buck converter drops the voltage to 5V. It's powered either directly from the input, or from a 12V SLA battery. The battery in turn can be kept charged using a controller.
I've added the on-off-on switch as I don't think the 12V power from a car will actually charge the battery. The diodes are for when the input voltage is different from 12V.

Questions:

Will this work?
Are there better methods (almost certainly)?
Will it make an E-Eng cry (possibly)?
What happens if the input voltage is very different the 12V battery?

Parts:

6-60V Battery Charge Control Module
5V Step-Down Voltage Regulator


texts:
I have read a lot about capacitive loads on the output of an op-amp and the possibility of unwanted oscillations and instability. my knowledge on phase margin and frequency domain analysis is a little weak and I can't figure out if my circuit bellow is gonna be unstable or not:

The Op-amp supply is connected to 5vdc and GND. and here is it's datasheet:
http://www.st.com/content/ccc/resource/technical/document/datasheet/bd/fc/46/43/26/8f/40/7f/CD00001046.pdf/files/CD00001046.pdf/jcr:content/translations/en.CD00001046.pdf

I read in some application note that placing R19 would help the stability issue by increasing phase margin or something like that and fortunately I already had that in my circuit. but as you can see C10 capacitor also has a very high capacitance value. is there an analysis or rule of thumb which would determine if this circuit is safe? should I change my op-amp IC? or should I use other methods as well to insure my circuit's safe operation?

I can provide additional information if you need it. Thanks.


texts: How to Protect an ADC Input from Overvoltage

texts:
I have a module with an ADC with a maximum input voltage of 2V.  I would like to monitor the battery voltage of 15V with this input.  I have successfully used a trimpot as a voltage divider to effectively divide by 10 to get 1.5V at the input.

The trimpot is to calibrate the reading because fixed resistors will never be exact.  Is there something I can add to this in order to protect the ADC input against overvoltage if the trimpot is turned too far?

As an aside, I am planning to also add an op-amp voltage follower at the input to isolate the voltage divider from the ADC input.


texts:
I have an older Seymour Duncan vintage rails pickup. Part number SVR-1N-0309.  This model only has two wires, red and white, compared to the new versions. Unfortunately, Seymour Duncan doesn’t seem to have the old wiring diagrams anymore. I’ve contacted them and I’m still waiting for a more senior employee (who remembers their older color codes) to get back to me.

Is there a way to test a coil to determine the intended start and finish compared to another pickup?  I’m trying to avoid phase issues when two are pared together.  I do have a basic scope.

Known pickup is blue channel. Test pickup is yellow.

With red signal and white to ground:

With white signal and red to ground:


texts: Do chained I2C address translators also act as buffers?

texts:
I'm working on a data collection/testing setup for multiple pogo pin test PCBs (~10 max per master) connected over I2C, daisy chained together. The design is based around the AD5593R ADC/DAC/GPIO chip, which unfortunately has only one bit to change the I2C address.

Therefore, each board will have an AD5593R and a LTC4316 I2C address translator, plus some unique resistor value for modifying the I2C address.

Is it correct that I won't have to worry about capacitance on the I2C line since the signal will be passing through each translator? Should I choose my I2C pullups based on just the capacitance between each board?

I am using 1 meter long shielded cables to connect each board. Does this design warrant a differential transceiver?

I understand this design is a bit convoluted, but this is a specific one-off test setup where cost/number of chips isn't really important.


texts: Why do some PCBs have the courtyard in the silkscreen layer?

texts:
I've seen quite a lot of PCBs which have the passive components outlined all the way in their silkscreen.

Something like this:

Here there is an outline around each passive which goes (almost) all the way around, and seems to be sized exactly the same as the courtyard - the lines for components placed side by side overlap.

This style is apparently very common in high-volume stuff designed and mass produced in China - in this case a Bluetooth module, but I've seen lots of other boards which are the same.

Why is the silkscreen done in this way?

Is there a functional reason for it? Is there some way it makes assembly or inspection easier at volume?


texts: How to enable auto detect AV inputs using dummy signal instead of actual video?

texts: I got a TV with a cracked screen that otherwise works fine, which I managed to change the inputs to "AV" (3 RCA jacks). So I amputated the screen and now have a mini stereo with remote. The only problem is that I can only hear the L & R line inputs when a video signal is fed into the (yellow) composite video jack. Right now, I use a video camera to provide the necessary signal, but I'm looking for other (cheaper) ways to trick the circuit into producing sound. I'm hoping for easy. Wild guess: use a 555 to produce blips at some frequency, amplitude, and duty cycle?


texts: What is actually sent/loaded to a microcontroller / STM32?

texts:
I see in all tutorials or sources, everybody creates a project in some IDEs and then loads code to the MCU again via those IDEs.

What is sent to the MCU? Is it a sequence of binary numbers or some different file?

Is there one file that I can just send it to the MCU without using any third-party application (IDEs)?

For example, I am using STMicroelectronics's STM32CubeIDE, and as I understood, it generates a .elf file. What is the role of this .elf file? In which step does it stand during loading code to MCU?

I think I found a better way to express myself.

I am essentially looking for something identical to a .exe file. Through the development of a .exe file, there are lots of parts .c , .h , .cpp for example. But an end user only needs an .exe file to run the code. Then I wonder if there is an equivalent of this .exe file (or any executable file format from other operating systems) in embedded platforms.

The comments below the approved answer may be helpful to understand in detail.


texts: State Variable Filter - Unexpected High Frequency Behavior

texts:
I am designing a voltage-controlled state variable filter for use in a modular synthesizer. Its function is to produce low-pass, band-pass, and high-pass responses for a given audio input signal. Corner frequency and resonance (Q) are determined by LM13700 amplifier bias currents, which are controlled by external voltages.

Here is the circuit I'm simulating and breadboarding. Resonance control is simplified in this schematic, and signal ac-coupling and output buffering is not shown.

Behavior of the simulation and breadboard prototype is as-expected for normal control voltage and signal input frequencies in the range of <1Hz to 20KHz.

Out of curiosity I simulated the circuit to 100MHz and found that, in the 50KHz-200KHz range, gain starts increasing. This is most visible in the low-pass output. The frequency at which gain increases is independent of Q and corner frequency, and seems to be determined entirely by the op amps used for U6 and U7. Responses for TL072 and LT1022 show a 180-degree phase shift at different frequencies, leading me to believe this is non-ideal op amp behavior.

I am not too concerned since the circuit functions properly in its intended application, but would like to understand why this is happening.

Question:

Is non-ideal op amp behavior the cause of this high frequency behavior? If so, what parameters are relevant?


texts:
This feels like a silly question, but I don't know the answer.  How do I find an appropriate LED strip?  I am looking for a flexible strip of LEDs that can be driven with apprx 65 VDC at 350mA and is  550-600mm long and no more than about 9.5mm high.

To be clear, I am not looking for a product recommendation.  I am looking for a "how to find it" recommendation.  Tomorrow I will likely want a completely different LED strip and I hope today's answer will still be applicable then.

This is to replace an LED strip that just burned out (the lights are very dim and some do not light at all).  The strip is a flexible strip with an adhesive backing.  I like the fixture and would like to replace the LED part.  It is verified that the driver is okay; I have several of these light fixtures and putting a fresh one on the driver lights nicely.

There are numbers on the existing LED strip:  2835-90D (I assume this refers to 2835 type SMD LED and there are 90 of them on this strip), 591-6mm (I assume this is length-height), and 5B18C (no idea what this means but an internet search with this brings up many Alibaba pages of LED fixtures).

Anyhow, searching Digikey/Mouser/Allied/Newark/Arrow/Google has been an exercise in frustration.  Maybe I am using the wrong keywords ("LED strip", "LED tape", "LED", "2835" to name a few) or maybe I am just looking in the wrong places.  I suspect there is a more appropriate keyword and perhaps a more appropriate search engine.

I believe these things exist.  I was able to find a model 12V-MB-CW-12M unit (Inspired LED, LLC) but of course it does not match the power supply I want to use.

It is an option to just throw all of this out and buy a new one.  They are certainly cheap enough; probably less expensive to replace than to repair.  But I think I can do a little bit better than the original manufacturer and I think I can find a slightly better component and I think the final assembly will be a little bit better if I do it myself.  Like I said earlier, I like the fixture a lot even though I know everything else is mostly cheap junk.


texts: A basic buck converter circuit to power 3W LEDs from PC power supply?

texts:
I'm just finishing up my first electronics course (edx.org), and I want to build some LED grow lights for starting seedlings in the winter.  I have high power LEDs, like this one here, and I have a PC power supply, which I think will be easier than trying to build my own AC to DC converter, at least for now.

But now I need to take the 5V input and do something to feed 1A to these LEDs.  I asked a previous question here, before I realized that a transistor as a current source is a waste of energy.  One of the answers to that question suggested a "buck converter with feedback and a current sense resistor".  I don't know what this means. I just read about the buck converter, and I understand the basic idea.  I drew a circuit at circuitlab

Now, how do I use feedback to control SW1 so that a desired current is flowing through the LED?  In class we have learned about op amp feedback, and I think I could create a square wave pulse with an op amp, or 555 timer, or arduino, but I'm still lost.  The only "current sensor" I know is a simple resistor, but if I put one in the path of that LED, I'm wasting energy again.

I will edit the circuit drawing and update the question if I get suggestions.


texts:
I am designing a small device powered by a lithium cell and I'd like to use the Microchip's MCP73871 battery charger to enable charging it from an USB port. The charger IC has three status indicator outputs: /PG, STAT1 and STAT2. In the datasheet, all are claimed to be open collector outputs capable of driving a LED directly (see typical application schematic). I'd like to use these outputs to indicate the status of the battery on the device's LCD display via the controlling PIC microcontroller.

Provided the outputs are just plain open collectors, there is no problem to use a pull-up resistor (say 50 kOhm) tied to the MCU's VDD and all should work. A problem might come, if there is a CMOS-style diode protection network on the outputs (especially the upper diode tied to VIn) - the pull-ups would power the charger IC from battery via this diode when no USB power cord is present. I know the current would be negligible if the pull-up resistor were sufficiently small. But a plain BJT in Common-Base configuration could effectively separate the "power domains".

I have used such circuit before in a similar situation (FT232R that would short the communication bus to ground when not connected to the host) and it worked fine. However, if this is not needed there, I'd prefer not to make mess and "keep it simple and stupid". I've gone through some ANs, but I have found no actual schematic of MCP73871 connected to a MCU (there are always just indicator LEDs).

So, my question is: May I rely on the assumption that these outputs have no protection circuits or anything else that would sink current when no voltage is present on the wall outlet side?


texts:
The following circuit contains an Uninteruptable Backup System (UPS).  So if the main battery fails, the UPS auto-switches on to power the essential instruments. (The UPS senses the voltage drop.)

The dual-pole switch connects the UPS to the main battery, and switches it on at the same time.  When switched off, this dual-pole switch by-passes the UPS, via the bypass line, and powers the essential instruments from the main battery.  This is in case of UPS failure, so the essential instruments can still get power.

The diode protects the UPS from reverse current, when the UPS is switched off.

This is all very logical (my circuit design).

However, what should I do with the negative cable on the bypass line?  Will that need a diode in it too, or can I connect it direct to the main battery?

I would be grateful for any advice.


texts: To avoid ESD when you are working on computers, what should you attach your wristband to?

texts:
When I'm working on computers, I want to avoid eletrostatic discharge. I have a wristband, but I'm not sure that I'm attaching it to the right thing. Usually, I'll clip it to the case of the computer. However, there are two cases in which I'm not quite sure what the proper procedure is. First, sometimes laptops seem to have a all plastic case until you take them apart enough. Second, things like harddrives are ESD sensitive, but when you get them they aren't in any computer, so what should you attach to? That got me to wondering if it would work for it to be attached to a ground (like the third prong in a US outlet, which is attached to a grounding rod or water pipe).
Could someone clear up for me what will work to avoid ESD and what will not?


texts:
May I please ask why my phase shift oscillator as shown is not oscillating?
My R1=R2=R3, and C1=C2=C3.
I am trying to get around 1kHz of oscillation, so using the simple equation of fr=1/(2*piRC*sqrt(6)), I get all the values as shown in the pictures.

But why is it not oscillating?
I tried at both Multisim and LTSpice, but it just doesn't simulate.
I am using ideal opamp at both simulators (gain is very high, 200x let say).
I put Rf(feedback resistor of opamp) to be 220k to have Rf>29*R, which will make the loop gain >1 (to fulfill the Berkhausen criteria), but it is still not oscillating. I thought the circuit fulfills both of the criterion for oscillating to happen?

I tried changing Rf to even higher value, and even play with the RC values. I also tried to use LM741 op amp and rise the supply voltage slowly, but I never get oscillation.
May someone please give me enlightenment on what is wrong/lacking?
Thank you very much.


texts: What is difference between natural response and zero-input response of a system and how to find natural response?

texts: In most books it is said that natural response is another name to zero-input response while in some resources is is mentioned that the classification is based on poles of transfer function and input.As the second definition is more theoretical then mathematical I'am having difficulty in finding natural response of certain systems where system function and input have same poles.


texts:
Given voltage, measured current draw, and RPMs of an AC motor, and an estimated efficiency rating, is it possible to calculate the actual instantaneous output torque? Or is other information required?

I can also measure its physical dimensions; shaft diameter, etc. With some effort I should be able to measure the time it takes to spin up to full speed as well.

Here is the motor I have and the only label on it. I don't know where it came from:


texts: bi-directional flyback diode for relay spike protection

texts:
A flyback diode is used to protect circuits against the reverse voltage generated by removing power from a relay coil.
Like this:

simulate this circuit – Schematic created using CircuitLab

But what to do if the polarity of my power supply isn't known?
placing two diodes in parallel in opposite won't work (short circuit)
Any idea for bi-directional flyback diode?


texts: How do I work out the pin configuration of this crossfader with a multimeter?

texts:
I got this crossfader out of an old DJ mixer.  I want to use it in an electronics project of my own design.

It's got 4 pins - which I presume are 2 x input, 1 x output and 1 x ground.

Using my Fluke 179 multimeter, how do I figure out which pins are which, specifically which is the ground pin?

Thanks in advance,

Ryan


texts: Small signal model for Mosfet...unsure as to whether its common drain, gate or source

texts:
I am looking to solve for the input/output resistance in the small signal model for the below circuit. But, I am unsure as to how to set up the model as I can't tell if it is common gate/source/or drain. I know in small signal the capacitors will act as shorts.. but from there I am pretty lost in the schematic. I've solved for Vgs, Idrain and Vds already in the DC bias model.
Will Vin be 0 since its shorted to ground?


texts: EAGLE - changing only one PAD's radius and not affecting the library part

texts:
I have a PORTC and PORTD which use a same library part (IDC connector). But because some of the pins on PORTC and PORTD are not connected (NC) I would like to strengthen them by increasing the radius of some pads which are different between PORTC and PORTD.

How can I do this in EAGLE if I don't wan't to create a new library parts or modify existing ones?


texts:
I'm using a TI TPA6017A2 as a pre-amp for an in-car audio application and it's getting excessively hot, to the point where the IC burns my finger when touched if I set the input volume to max. Beyond that, I can hear the music being emitted from the IC which is extremely disconcerting.

My design has a thermal pad with thermal vias and the IC has been soldered down to that pad per the datasheet recommendations.

If I lower the input gain, I can alleviate the issue, but this isn't a bug I want in my final design.

As far as the layout, I have duplicated the design of the evaluation module, which also gets hot, but not the extent that my design does.

The only deviation from the reference/EVM design that I have is that I have tied the negative output channels together directly, since the wiring harness expects a single negative line being fed in. Could this be the cause of my issues? What exactly is causing the IC to resonate?

It should be noted that the output audio has no distortion, but the thermal threshold is being hit and the IC is shutting itself down at times.


texts: I have a 12V DC power supply and have a digital guitar pedal that needs 15V DC. There are a few other 9V/5V power circuits that I created using voltage regulators and a couple of capacitors, but I'm not familiar with how to go UP in voltage.


texts: PSPICE graphs work separately for subcircuits, wrong when combined?

texts:
I'm working on a pulse generation circuit that will be used to drive an ultrasonic transducer. The following circuit is giving an unexpected output.

It might look complicated, but really it can be divided up into smaller parts. Also, despite the wierd names for the GNDs, they are all 0/CAPSYMs. The P-type MOSFET is the pspice model SiHFU9214 provided by Vishay.

1st Part on Right: 220V DC Power Source

Verified Output at 220V DC:

2nd Part: Pulse Controller (100ns pulse at 800sps/1250us)

The Vpulse does have a 40ns PW parameter, but that is simply due to the delays of the rest of the gates.

Verified Output of 100ns pulses at the desired frequency:

Of course, the problems always arise when trying to combine different subcircuits. The probed node (1st pic) should be reading around 220V, instead I simply get this sloped line when running the simulation for 3750us.

When running the simulation for 0.200s, it gets even better.

In my understanding, this entire node should slowly be raised to 220V when the pulse signal is not activated.

But that doesn't seem to be happening. Measuring from these next nodes for current and voltage I get a little bit of information.

I'm wondering if the 60Hz frequency of the DC source, and my pulse frequency of 800Hz might be causing the 10nF capacitor to not charge correctly.


texts: Can the small voltage output from a dc hobby motor (used as a generator) be amplified to light an led or flashlight bulb?

texts: I built a small windmill and connected it to a small dc hobby motor, using the motor as a generator. I want to light a small led or flashlight bulb. Is there some kind of simple capacitor/diode/resistor combo I can use to boost the voltage enough to.do this?


texts:
I have a bit of a problem figuring out how harmony i2c driver works.
Trying to establish connection between PIC32 and a barometric sensor MS5637 have been a bit of a nightmare for me.

From sensor's datasheet on page 9 we can see that there is a reset sequence and after that a simple prom read.
Below you can see what am i trying to do, but I am not quite shure what should I do to make this communication work.

Using MHC the i2c driver is initialized inside System Initialize and then there is my app code.

void send(uint8_t cmd){

    //Start i2c
    DRV_I2C0_MasterStart();

    //Write address write
    DRV_I2C0_ByteWrite(0xEC);
    DRV_I2C0_WaitForByteWriteToComplete();

    //Write command
    DRV_I2C0_ByteWrite(cmd);
    DRV_I2C0_WaitForByteWriteToComplete();

    //Stop i2c
    DRV_I2C0_MasterStop();

}

uint16_t readPROM(uint8_t cmd){
    uint16_t value;

    //Send Prom address
    send(cmd);

    //Start i2c
    DRV_I2C0_MasterStart();

    //Write address read
    DRV_I2C0_ByteWrite(0xED);
    DRV_I2C0_WaitForByteWriteToComplete();

    //Byte read MSB
    DRV_I2C0_WaitForReadByteAvailable();
    value = 256 * DRV_I2C0_ByteRead ();
    DRV_I2C0_MasterACKSend();

    //Byte read LSB
    DRV_I2C0_WaitForReadByteAvailable();
    value = DRV_I2C0_ByteRead();
    DRV_I2C0_MasterNACKSend();

    //Stop i2c
    DRV_I2C0_MasterStop();

    return value;
}

void APP_Tasks ( void ){
    //Reset command
    send(0x1E);
    ShortDelay( 3000 ); //3 ms

    //Read prom
    uint8_t i;
    for (i=0;i<8;i++){
        readPROM(0xA0 + i * 2 );
    }
}

Response is always 0x00, but should be something different than that.

I forgot to mention when sending any kind of command on the i2c lines the current rises on sensor. Does this mean the sensor is responding?

If there might be anything obvious I am missing, please warn me, because this is the first time for me using the i2c.


texts: Floating EEPROM (28c64A) pins an option?

texts: I am building an eeprom programmer for the 28C64A (dip package) with my old basic stamp ii "homework" board (lost my arduino in the move). I have the first four address and data pins, as well as W E and G connected from P0 to P10. I am working with what I already have, so buying shift registers and friends is not an option. My question is that I read over the eeproms datasheet and it said nothing about leaving unconnected pins floating, so is it okay to do that, or must they be grounded?


texts: What does "1000 VRMS CAT II, 2500 Vpk" on a voltage probe label mean?

texts:
Our Tektronics voltage probe P5100A has a label of "1000 VRMS CAT II, 2500 Vpk". Could you please tell me exactly what does it mean?

I'm trying to measure an RF generator output voltage which is expected to be about 2 kV in amplitude in maximum at 13.56 MHz. I interpreted this label that P5100A can withstand 1000 VRMS ~ 1.414 kV in AC voltage amplitude and 2.5 kV transient spike, so I thought I couldn't use this probe for my measurement.

However, the local company engineer said that I can use this for the measurement I want to make. He said a current flowing the probe should be very low so I don't need to be overly concerned. Is what he said really true? I tested this probe and at least the probe looks working at the voltage amplitude of 1.7 kV. Can I go further so 2 kV is reached?

And in terms of "CAT II", What does it try to tell me? Wikipedia said CAT II is associated with low voltage installations such as household appliances, portable tools. It is a rather broad concept. So, Should I consider this seriously?


texts: Frequency Domain Analysis with Transistors

texts:
I have some doubts about how some circuits with transistors are described in electronics textbooks. Let's see an example (taken from Thomas H.Lee, The Design of
CMOS Radio-Frequency Circuits).

This books (and all other books I have read about circuits with transistors) uses a convention in which signals in time domain are indicated with small letters. So for instance iout = iout(t).

Let's consider this example with a Small Signal Mosfet model with parasitic capacitances:

The book considers the situation in which a current source iin is put at the input of the Mosfet, and tries to evaluate the current gain. The result of the analysis is this one:

You may see there is the variable ω, which is due to the presence of the capacitances. My question is: how can be this analysis correct? It is a time domain analysis, so it is not correct to say that the voltage drop on a capacitance is 1/jωC * current: we should use integrals.

I think the previous relationship is true only if we indicate with \$i_d\$ and \$i_{in}\$ the fourier transforms of the drain current and input current. But they have been defined as time domain signals.

The book goes on and uses also equations like that of the drain current of a MOSFET in saturation (\$i_d = k(v
{gs} - v_t)^2)\$ and always in time domain. How can this analysis be correct? I'll replace all these signals with their Fourier transform: is it true?


texts:
I'm working on a quadcopter and have some questions about the receiver and transmitter. I'm going to be milling the boards myself and wanted to know what would be a good carrier frequency to use. I was planning on 10 MHz but I'm not sure if it's better to go higher or lower? I also have the basic block diagram laid out and was hoping if someone could give it a once over and let me know if I'm missing anything. For the modulator block I was going to use the SA605 chip.

Thanks a lot for the help!


texts: How much amps (maximum) are flowing through 1000Base-T Ethernet?

texts: How much amps (maximum) would be flowing through a 5 meter Cat 5/6 Ethernet cable with 1000Base-T speed (IEEE 802.3ab, 5-PAM coding, so voltage levels vary between +- 2V, 1V, 0V)?