texts: Switching Micro-controller from Adapter power to Battery

texts:
Currently I am running my micro-controller boards with power adapter(AC to DC).

Now I am developing a system which senses AC power and sends me some signal when AC power is gone.

The problem is I am running my board with the AC power(through adapter) which I am sensing. So, I need to switch to battery power( as backup ) instantly when AC power is gone making sure my board doesn't turn off while switching.

I am not sure how it should be done.


texts: TP4056 with DW01, can I use a diode to create an "UPS"? Design review

texts:
I'm studying lithium cells and their related mainstream modules.

One of the most common -yet wrong- use of the TP4056 module is to use it with the USB 5V input and an active load on the output (at the same time). AFAIK this will screw up the charge ending trigger current.

What if I add a diode, from the USB +5V to the load's positive, and a Schottky diode from output+ to the load's positive? I'll lose efficiency due to the (small) diodes' voltage drop but this is acceptable to me.

When the USB is connected the load will see the USB 5V, minus the diode's voltage drop, and, provided that the USB source is big enough, it will also charge the cell. Without the USB connected the load will be powered by the TP4056 in its standard configuration, except for the small Schottky voltage drop.

With the USB connected there isn't power consumption from the cell to the load during the charge process, because of the diode, and therefore also the terminating current can be properly trigger and stop the charge.

Am I missing something? Provided that I'll add a dc-dc step up converter, it's within the TP4056 specs to be used in this contraption as a 5V UPS for a device that only consume a few (3) watts?


texts: Qualitative explaination of Output Characteristic of Transistor (BJT) using Depletion layer between Collector and Base

texts:
From my understanding,
The diffusion layer at a p-n junction is an equilibrium of two opposing forces on charge carriers due to 2 forces - Concentration Gradient and Electric Field caused by Bias and inturn by diffusion caused by Concentration. In steady-state (with or without bias) forces are perfectly balanced at an attained equilibrium (which is dynamic and changes with bias). Now the forces are all balanced, all that causes this dynamic resistance effect is the change in the size of the depletion layer thus resistance, not these forces since they've been balanced now.
Hopefully, that's the right picture of it. I'm trying to see how the depletion layer between Collector and Base changes with \$v_i\$ at Base (Common Emitter connection). I can see that depletion later EB is decided solely by the biasing 0 to \$v_i\$. What I cant explain is how this affects the depletion later BC.
What I'm trying to do is roughly get what happens to the resistance(\$\frac VI\$ rather than \$\frac {dV}{dI} \$) between Base and Collector, use \$I_e \approx I_c\$ and ohm's law to get graph between \$v_i\$ and \$v_o = v_C\$
Skip if needed: I searched up, all explanations have a "Current simply accelerates into Collector" which I clearly get from \$I_e \approx I_c\$ but don't get how that leads any relation between base current and collector current obtained or the output characteristics. I found this book in an internet archive by Millman & Halkias, read through chapter 5 where it reaches Output characteristics, didn't get it yet. Read other related questions like Why is Ib proporional to Ic in a bipolar transistor? , still don't get a qualititive picture other than the "Current is attracted by Forces" explaination or a "it gets into Semiconductor Physics and complex Math". The former explaination does not appeal to me because the forces are now balanced right? Isn't resistance by depletion layer causing this and not the forces? So what happens to this depletion layer?
Or more appropriately,
The Question: Can someone give a qualitative explanation of Output characteristics of a BJT using depletion layers instead of the regular "Current is attracted by Forces" one?
Thank you


texts: SD card speed class specifies "minimum sequential write speed" but not the "maximum sequential write speed", why?

texts:
A speed rating for any memory device is usually how fast it can work. However, the speed class of SD cards actually specifies the "minimum sequential write speed". Please see here for evidence under "SD Speed Class".

Shouldn't speed rating be about the maximum rate at which we can write to a memory?
Also, since the SD card speed class is about the lower bound, does that mean that if we write to it at a slower rate, the card will not function and the data shall become corrupt?

Finally, what exactly is the minimum data rate for SPI mode? The "SD Specifications Part 1 Physical Layer Simplified Specification Version 2.00 September 25, 2006" section 7.2.15 "Speed Class Specification" states:

  As opposed to SD mode, the card cannot guarantee its Speed Class. In
  SPI mode, host shall treat the card as Class 0 no matter what Class is
  indicated in SD Status.

This implies that the minimum rate at which we need to read/write the card in SPI mode is actually 0 MB/sec? This implies that when using the SPI bus, the actual speed class of the card does not matter? But is this really the case?
As far as I am aware, after SD card power up, when we want to enter the SPI mode, we communicate with the card using a very low clock frequency which is in range of a few 100KHz at most. Is this true for SD card of any speed class?


texts: Do PCB printed fractal antennas have nulls orthogonal to PCB?

texts: I know the printed strip antenna I am using now (on a NRF52DK) has two nulls along the axis of the antenna, parallel to the PCB.  I know a whip antenna sticking out of the PCB has nulls in the direction of the whip (orthogonal to the PCB.)  What is the direction of the nulls of a fractal antenna printed on a PCB?  Because I want a printed antenna, and to install my PCB flat, and have uniform reception in the plane of the earth's surface.


texts: How to interface optical M-bus on heat meter

texts:
I have Landys Gyr heat meter 2WR6, which has optical port for M-bus communication. I would like to periodically read its values via Arduino / RPi / NodeMCU / whatever.

From the technical manual (p. 7), it has:

Optical interface   Standard, EN 1434-3
Communication       Optional: M-Bus or pulse output
Protocol            IEC 870, 300 baud in Nb

and this datasheet says:

  ULTRAHEAT 2WR6 heat meters are all equipped with an
   optical interface to IEC 870  as a
  standard, e.g. for connecting the tool PappaWin for
   parameter setting and diagnostics.
  Note: for the optical communication with the 2WR6 a
  n optohead with echo suppression is
  necessary

My model does not have any wire output. So I'm not sure if the optical interface is in fact M-Bus or not and if that IEC 870 protocol applies also to the optical interface. All references I have googled about EN 1434-3 are about wire physical layer, not optical. For optical I have googled EN 62056-21.

So the question is how this optical interface works. Will simple IR diode + IR photodetector connected to serial port work as the physical layer or more is needed? Can this be bought ready-made for a reasonable price?

Which protocol does it use? For EN 62056-21 there is openHAB binding, which I could use probably. I guess I must first send some request to the meter and it will then reply with all the data.

The optical port is on the following picture (which is Tx and which Rx?):


texts:
I am trying to use a current source for applying current pulses (0-20mA and 10-20ms width) to a resistive load inside an MRI scanner room. Pulses are applied when an optic trigger is detected by the MCU. The MCU also controls the selection of the source/sink channels of the multiplexer. A diagram is given below.

The RF signal of the MR system appears at the output of the optic to voltage converter, and thus MCU receives false triggers. This issue was solved by disabling the interrupt of the MCU for a while after the first trigger pulse is detected.

The RF noise appears also at the address selection lines and at the current channels. I tried using Faraday cage by putting the entire circuit inside an aluminum box, using coaxial cables for current channels and grounding their  shielding at the near endings. However, RF signal still observed.

Any suggestions to eliminate this RF signal?
Do LP filters will help here? if yes, what are your recommendations for the filter design?

Notes:
1- Current channels are passing to the MRI room through a hole in the wall.

2- The output of the optic2voltage circuit is (0-3V).

3- All the circuit components are fed by a single power supply (+15/-15v).

A view of the detected RF signal between the terminals of a current channel is shown below


texts:
I've come into an electric bike that currently has a NiMH, 24v, 20cell battery pack. On the pack as well it says 8000mah. The previuos owner has misplaced the original charger :(

The bike has been unused for over a year so would it be safe to assume the batteries are dead or going and won't last long? They were probably never discharged before going into storage in a tropical climate. If I hook it up to a multimeter, what voltage would mean empty and what would mean full? What settings should the multimeter be set to?

Main question is, can I create my own battery pack that uses say only 15 cells max (so I can use my current NiMH charger/discharger) that can give me the same if not a bit more power? I assume I can't test or fully charge/cycle the current 24v/20cell battery on a NiMH charger/discharger rated for only 1-15 cells?


texts:
I'm trying to read and write data to a LIN Bus, which is a single wire bus. As such, only one "module" (my PIC is a module in a network) is allowed to talk at a time. I'm using an MCP2004 LIN transceiver, and my device is a slave on the network. I'm unsure what hardware the master and other slaves utilize.

The problem I'm running into is that sometimes, a byte is pushed onto the Bus at the same time I'm pushing one out, which results in a frame error.

In my firmware, I have an interrupt service routine for RX from that Bus, and it has the highest ISR priority set (7). The problem is that as the program continues to execute, it's not always possible for me to tell if there's data thats been received.

Right now, I check my RX buffer size prior to transmission, but sometimes the byte is received after that conditional, but right before I actually write data to the bus. I'm also checking UxSTA, but I doubt that helps, since if there's data on the hardware buffer, the program would be in the ISR, and not my main code.

It may be worthy to note that I'm not transmitting in an ISR.

What's the best way for me to handle this contention? Is it advisable to keep the program in the ISR for the entirety of the data reception? The protocol does contain a message length byte and a checksum.


texts: Off resistance of analog switch 4066 pretty low?

texts:
I am trying to use an analog switch to switch signals between my end nodes. Before I tried in the actual circuit, I wanted to try it in a test circuit. As 4066 can act as a switch for both analog and digital signals, I tried it with a very simple circuit as below.

However, the impedance between pin_1 and pin_2 is as follows.

#Vdd | Vss | Vctr | R12
------------------------------
0    | 0   | 0    | 1000 kohm
6    | 0   | 6    |  100  ohm

Now, why is the off impedance R12 so low? I expected it to be in the order of 109 ohm.

Note:

Vctr --> Control voltage at pin 13.
R12  --> Impedance between pin_1 and pin_2.


texts: Audio jack detection to turn on device without power loss

texts:
I'm trying to make simple headphones amp and I wonder - is there any way to use stereo jack connector with N-C switches like this:
to turn on the amp so the battery is mechanically disconnected?

I mean that, if my connectors had N-O switches, it would be easy, but with N-C I have no idea, whether it's even possible to make such "smart" power on, without any power loss (i.e. powering some transistors/logic gates that detect open circuit etc.) or maybe should I seek for female connector with N-O switches?

Best regards!


texts: What permanent magnet motor is the best for the bike generator? How to decide about wattage?

texts:
I am new here.. I would like to build my bicycle generator with permanent magnet motor similar to this one Bicycle Power Basics

Basically, I want to run my pedal cinema with a bike generator. I am not sure about the load I will need but I will try to reduce it as much as I can because I am aware that I will not be able to produce more than 100W anyway..

I made some research about permanent magnet motors and I found some here
http://www.fireworksandscootersdirect.co.uk/category.php?CID=52 They mainly differ in watts.

My question:
- is the wattage of the PM motor important in making the decision about single bike generator? If I buy a motor with 24V 350W RPM2750 will I be able to run appliances which consume more power rather then I would purchase a motor 24V 250W RPM2750? Does it mean that the motor with higher wattage will be more effective in running appliances which consume more power?

As I understand, the adult person is able to run the bicycle with more or less RPM 60, so it means that in an hour I will be able to do RPM 360, which is 7 times smaller then RPM2750. So if I use a motor with 350W, will it give me 50W and if I use a motor with 250W it gives me only 35W? Is this correct or I am completely wrong?

How can I choose a permanent magnet motor?


texts: Is this slide wrong about the differential signal waveform?

texts:
While learning about the differential signals I saw this youtube video. It looks like this slide does not correctly shows the voltage levels of the complementary differential signals, as I have marked in the following image.

My understanding is that the 'Blue' colored complementary signal should be -2V to 0V signal. So when we take the difference of the two signals (Black colored and Blue colored) then we get the original 'Single Ended Signal'. Please correct me if my understanding is wrong here.


texts:
This started with my question here there is no need to read it, I
  put it here for additional info.

I'm trying to drive two MOSFETs in Half-Bridge topology and I finally could get the pulse transformer working correctly using a IR2110 working as a two low-side driver. Here is the schematic:

simulate this circuit – Schematic created using CircuitLab

Probe 1 and Probe 2 are my oscilloscopes probes and here are the resulting waveforms when driving the IR2110 through a microcontroller generating a 200KHz Half-Bridge PWM:

There is some ringing but I assume that's because I'm testing in a protoboard and there is a lot of distributed capacitance. My real concern is about the waveform. The transformer in the schematic has only one secondary but my transformer has two secondaries in opposite directions for each MOSFET.

The yellow waveform is Probe 1 as you can see I get the expected waveform with a dead-time at the reference level (the small '1' yellow mark on the left of the screen) but on the secondary side (the blue signal, Probe 2) this dead-time is at about 10V and it should be at reference level otherwise MOSFET is active at 10V.

Am I right or I'm missing something?


texts:
We're working on a battery charger for an electric bicycle at the moment, but prototyping with a PIC32MX695F512H kit board and an MCP4706 DAC soldered onto a breakout board, programmed using a PICKIT3.  We've got a few other peripherals all working so far, including a 20x4 LCD also over I2C, so at least that is working.  Our issue is that our DAC operates on and outputs 5V, regardless of whether or not we have a Vref connected.  (the chip defaults to short Vref to Vdd if nothing is connected to the pins)

The output from the DAC goes to a voltage follower that controls a power MOSFET, allowing a variable amount of current to flow to the battery based upon readings from a current sensor (in-line) and voltage sensor across the battery terminals.

Relevant code snippets are attached below:

#define DAC 0x60
.
.
.
// Configure I2C registers
void ConfigI2C()
{
    //1 USES RD10 AS SCL1 AND RD 9 AS SDA1
    /// I2CxCON I2CxSTAT I2CxADD I2CxMSK I2CxTRN I2CxRCV
    I2C1BRG=0x186;                  //390 for 80MHz to 100KHz
    I2C1CONbits.A10M=0;             //Use 7-bit addresses
    I2C1CONbits.DISSLW=1;           //disable slew control for standard
    I2C1CONbits.ACKDT=0;            //Use and ACK not NACK
    I2C1ADD=22;                     //Sets slave address for PIC32
    TRISD=0;                        //Sets Port D to output
    I2C1CONbits.ON=1;               //turn on I2C
}
.
.
.
// Start
void I2C_start(void)
{
    I2C1CONbits.SEN=1;          //send start
    while(I2C1CONbits.SEN){}  //waits till start bit detected
}

void I2C_stop(void)
{
    I2C1CONbits.PEN=1;          //send stop
    while(I2C1CONbits.PEN){}    //waits till stop bit detected
}
.
.
.
void SendI2C3(char addrs,char regis, char data)
{
    char ack;
    I2C_start();
    ack=I2C_write(addrs); //Address for LED is 0x50
    ack=I2C_write(regis); //0xFE for LED
    ack=I2C_write(data);  //0x20to0x7F standard
    I2C_stop();
}

We just get Vref out.  We've tried all 8 address the board can have, and no dice.

Anybody have any advice on how to help us?  we've been stuck on this problem for a couple of days.  Thanks.


texts: Looking for the name of this optical sensor detecting beam interruption

texts:
I'm trying to find a sensor that is similar to the ones used in floppy drives to determine the track 0.

It's an optical sensor with about 3-4mm of space between the emitter and the receiver so that it can detect if the beam is interrupted.

All parts I can find are pretty large elements but I am looking for something small and I don't know what name they may have

An example of such sensor is on the photo here, the black part:

Additional question: I have a box moving on rails and it has 5 positions; the range is about 1m, precision about 0.5cm. Are these sensors the best way to go?


texts: What is the difference between a potential divider and a potentiometer?

texts: It would be nice if I could get an elaborate answer which highlights the difference between their functional aspects.


texts:
I am making a system which accepts signals (UART) from an external board. These signals are received by my MIcrocontrollers and further processed. Now, as part of the initial documentation I asked the client for the voltage levels of his boards as I did not know what voltage levels he would be sending (it could be coming 5V,3.3V or even very low voltage 1.8V based MCUs). As I did not know his MCUs I asked for a straightforward specifications of voltage(mainly the Voh,Vol, Vih and Vil). He sent me a document stating that my UART(in other words the UARTs in MCUs) should be TIA/EIA-422-b compliant.
The screenshot is as shown below -

Now, this is quite bizzare as TIA/EIA-422-b is a RS422 standard specification and RS422 is differential. So, I will need a UART to RS422 level shifter in between, right ?
Also, from the specs of RS422 I understand that they are +-10V signalling. Right ?


texts: Are there Atmel and PIC libraries for Eagle?

texts:
I am using CadSoft's Eagle library with added libraries from Adafruit. However, I still see an overwhelming lack of modern Atmel products in the component list.

I'm relatively new to Eagle so I haven't the expertise to add my own components and I've searched and added some Atmel libraries from CadSoft's user library repository. This still hasn't helped.

So my question is, where can I find a fairly complete Atmel (and PIC) library for Eagle? Of course Atmel themselves are no help since articles found during a Google search of their site state they don't produce libraries for 3rd party software packages.

Your help is appreciated!


texts:
I have built some circuit and it doesn't work.
Can I ask if my interpretation of datasheet is correct?
There is no hole, no proper dot on my package, but there is a symbol with 2 concentric circles and I interpreted that as pin 1 location.
This is how I I have done:

And this is image from datasheet:

And another one:


texts: What component does the 'coupon' label refer to in terms of PCBs?

texts: I was looking at a motherboard recently and I found a couple interestingly labelled component footprints. They're two through-hole mounted components right next to the CPU, and they seem to be called COUPON1 and COUPON2. The problem is, the two components were never put into the board, so I have no way of knowing what the holes are really for. I did some Google searching, but all I could find were links to cheap motherboards and PCB.


texts: How do I determine eye safety limits for IR LEDs?

texts:
IR LEDs typically report wavelength and radiant intensity (mW/sr). There are many warnings abound on the internet and from other local engineers to be careful of eye damage, but I find it difficult to pin down what threshold of safety exists for our eyes. In particular, I use 950nm IREDs for communication and am wondering about my safety.

According to one source I found (from Vishay), this working limit is 10 mW/cm2. This seems low compared to the output of off-the-shelf IR TX/RX pairs.

Obviously the IR intensity striking your eye varies based on distance from a diverging LED source, so how do safety limits work for existing IR emitting products (such as remote controls) and what should a reasonable safety limit on output optical power look like?

EDIT: I am interested in using the LED VSLY5940 in an open outdoor space with potentially other people working in the area and only intermittent use of the IRED. At peak driving, the datasheet states 5100 mW/sr. Should I be worried about potential eye damage?


texts: STM32 RTC alarm not configuring for the second time

texts:
I am using STM32l151vbt6 MCU and I am trying to configure RTC Alarm for every 15th minute. (That is 0, 15, 30 and 45th minute of the every hour.)

I can configure the alarm and it will work for the first time, if I try to set it again after the alarm occurs, it would set to previous alarm state. If I reset the MCU I can set the alarm and it will wake the controller from the stop mode when the alarm occurs. Please let me know how can I set the next alarm without resetting the MCU.

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
    /* 8(hour) and 19(day) are masked and there is no effect on the alarm */
    RTC_AlarmTypeDef    RTC_AlarmStructure =
    {
        0,
        0,
        0,
        RTC_H12_AM,
        (RTC_AlarmMask_DateWeekDay | RTC_AlarmMask_Hours),
        RTC_AlarmDateWeekDaySel_Date,
        19
    };
    const uint8_t       alarm_interval[4] = { 15, 30, 45, 0 };
    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

    RTC_AlarmStructure.RTC_AlarmTime.RTC_Minutes =  alarm_interval[RTC_current_time.minute/15];
/*Alarm A will be configured*/
    RTC_Alarm_Config(&RTC_AlarmStructure);

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void RTC_Alarm_Config(RTC_AlarmTypeDef *RTC_AlarmStructure)
{
    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
    EXTI_InitTypeDef    EXTI_InitStructure;
    NVIC_InitTypeDef    NVIC_InitStructure;
    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

    RTC_AlarmCmd(RTC_Alarm_A, DISABLE);
    RTC_AlarmCmd(RTC_Alarm_B, DISABLE);//Not using this

    /* EXTI configuration */
    EXTI_ClearITPendingBit(EXTI_Line17);
    EXTI_InitStructure.EXTI_Line = EXTI_Line17;
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);

    /* Enable the RTC Alarm Interrupt */
    NVIC_InitStructure.NVIC_IRQChannel = RTC_Alarm_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    RTC_SetAlarm(RTC_Format_BIN, RTC_Alarm_A, RTC_AlarmStructure);

    /* Clear RTC AlarmA Flags */
    RTC_ClearITPendingBit(RTC_IT_ALRA);

    /* Enable AlarmA interrupt */
    RTC_ITConfig(RTC_IT_ALRA, ENABLE);

    /* Enable the alarmA */
    RTC_AlarmCmd(RTC_Alarm_A, ENABLE);
}


texts: I've been playing around with logic gates and RAM chips and stuff the past week or so, but I can't figure out how to get a DIP switch to represent a digital '0' while still being able to represent '1' when turned on. Having no current running through doesn't work, and the switch only has one input for each bit. How would I do this?


texts: Attiny13 affects USBtiny programmer logic voltage levels

texts:
I wanted to port a simple program from an Attiny85 to the cheaper Attiny13. To make sure everything would work properly I started trying to upload a simple blink program to the MCU but could not get the USBtiny to communicate with the MCU, I would always get the initialization failed, rc=-1 message.
Since my issue was with establishing connection with the MCU I ditched the hex file and just ran avrdude -c usbtiny -p t13. I had everything set up so that I could just switch an Attiny85 for the Attiny13 since their pinouts are identical. The tiny85 worked exactly as expected, having no issues answering back and being programmed.
Researching online I tried the -B option for AVRdude with different values thinking it could have something to to with the clock speed, but always got the same initialization error.
After messing around some time I decided to probe the serial lines with an oscilloscope, and to my surprise I found that when running the avrdude command with the Attiny13 in place, the logic levels became really weird, having a high voltage of 5V and low voltage of approximately 4V instead of 0V. Under the EXACT same conditions tha Attiny85 didn't yield these strange voltages. You can check the scope trace images, first one is with the Attiny85 and the second with the Attiny13.

My set up/toolchain consists of a fresh WinAVR install and Sparkfun Pocket AVR programmer (USBtinyISP). Both the Attiny13 and Attiny85 are new from the same supplier, in SOIC packages so I'm using them on a breakout board. Tried a second Attiny13 chip but results were the same.


texts: What is USB overhead and why does it reduce the theoretical transfer rate so much?

texts:
I've been reading a lot about the topic USB/FireWire recently and stumbled upon the fact that, despite USB 2.0 having a rate of 480MBit/s, it often does not reach the actual transfer rate of 60MB/s. Often there is some sort of overhead mentioned, but I really don't understand what it means and there doesn't seem to be any sort of comprehendable explanation for someone who's not really tech-savvy like me.

I've also read that FireWire has this overhead too, but it doesn't seem to be as severe as for USB. Why is that?

EDIT: I guess I'm talking about MBit. Also, so you could say it's because of extra data being sent too, like these overhead bits for error checking, that my data that I want to transfer, for example, is being sent far below the theoretical rate?


texts: Will I be able to use this Electric Imp set up to measure temperature & current and report it via wifi?

texts:
I'm new to electric imp but it looks really cool! I want to get one to measure temperature of an air-conditioned room, and check the power usage of the a/c unit.

It looks like if I got the impExplorer kit that should cover the temperature sensing, and then I was thinking of the SCT-013-020 ([more info] to measure power usage. It looks like the cable on that goes to a 3.5mm connector - what would I need to connect that to my impExplorer?

Also, do I need to get anything else to achieve my aims?


texts: Purpose of divide-by-2 (or CLK/2) on a video pixel clock generator ICs

texts:
I've been looking into some video clock generator chips and almost all of them have a divide-by-2 or CLK/2 output pin (in addition to the normal CLK out).  What would be the purpose or application for such a pin?  I would think a multiplier would be more handy, especially for up-scaling video designs.

Sample from Datasheet:

Another chip sample:


texts:
In my Circuit Analysis book, I am tasked with finding \$v_x\$ and \$v_y\$.  So \$v_y\$: easy enough.  It's - 6 volts.  But I encounter a problem when trying to find \$v_x\$ - I can't develop enough independent equations to solve for all of the elements in a given loop.

Of the components in series, I called the topmost one \$v_c\$ and the lower one \$v_b\$.  I called the rightmost component \$v_a\$.

$$
-21+7+v_x+v_a=0\\
v_x-14+v_c+v_b=0\\
-v_b-v_c+v_a=0\\
-21+7+v_x+v_c+v_b=0\\
$$

Sadly, I can show at least to of these to be the same equation (they are not indepenet of each other!) so I have literally no idea how to solve this.

This is only the second problem of this type I have ever tried to solve, that I remember.

I would really appreciate it if someone could get me out of this jam!

The book gives the answer to be 9 volts.


texts: I bought a couple of clips like this . Does anyone know how to connect them?


texts: How to generate board plot/image in Eagle

texts:
I designed my own PCB in Eagle so I have both the schematics and the board files.

I would like to generate a figure like this one made for Arduino board in order to include it in the user manual that I'm writing.

Do you think it is possible to do that in Eagle?
If not, it is possible to do this by using my Eagle files as input for another software?

I tried to disable the displaying of top and bottom layers, but what I obtain is a black/white board with the components enclosure and it is not as good as the figure above.

Thank you a lot,


texts: Best way to connect a coil to a source with 50Ohm impedance?

texts:
I have a 50Ohm impedance source at 800Mhz and a coil with complex impedance Z = 0.0028 + j3973.9121 Ohms at 800Mhz.

I would like to maximize the current through the coil and protect the source. I cannot change the properties of the coil.

What is the best way to connect the source and coil? From my understanding impedance matching network will not be a good choice because the load impedance is mostly reactive. Should I just add some resistors either side of the coil to increase the resistance (maybe 25Ohms total?) and then use an impedance matching network with that or would that impact my requirement to maximize current too much?

Should I not impedance match and use a circulator with a terminator between the source and coil load?


texts: What happens to the electrons of semiconductors?

texts:
Take for instance, a diode. It has a region of n type material and a region of p type material. The p type material has a lack of electrons, the n type has an excess of electrons. When it's forward polarized, current will flow through the junction, etc...

This is a trick question so I will propose an scenario which best describes what I'm asking. In this scenario I will be using the electron current flow, and I want you to focus on a single specific electron, lets call it electron A.

Lets say electron A is on the n material of a diode. When I connect a power source to the diode, in such way that the diode is forward polarized (consider an ideal diode), the voltage source will displace the electrons from the n side to the p side, thus electron A will go from the n material through the p material all the way to the power source.

Now lets say that after electron A was displaced from its original position, I take the diode out of circuit. Does that mean that the place in the n type material where electron A was before, has been substituted by the electron injected by the voltage source? Or, in layman words: does it mean that electron A which was once in my diode, will now be "living" in my voltage source, and one of the electrons from my power source will now be "living" in my diode?

In which case it could be applied not only to the semiconductors, but any conductor, a cable will now have different electrons than the ones it originally had once a current passed through it.

I know however that all electrons are the same particle, no matter where they come from, what I'm asking is from an individual specific electron perspective.


texts:
I have a project I am building for my Kids Church Room.  I have a bunch of LEDs being lit by an arduino Uno, but at one point in the light pattern, I want to have a bell ring. I bought a doorbell that comes with a 24v A/C transformer.  I have a few MOC3010 TRIAC chips from a previous build (that did not work..) from a few years back, so I thought I might use them.  If I use the arduino to trigger the Triac, which would activate the 24v, and have it turn off very quickly as part of the sketch, I think it would create the proper feel.
My question is does the output pin on an arduino uno put out enough power to make the TRIAC work.  My previous failed project LOOKED good, but the 7474 IC chips did not put out enough power to activate the TRIAC.  Anyone know???


texts: Can a current source have a voltage across it?

texts:
I'm reviewing material from a lower div circuits class in preparation for the upper div class by redoing problems, and this is one of them.

Does it make sense for the branch with the dependent current source to have a voltage Va(t) across it? Wouldn't the voltage measured across it be zero assuming the current source is ideal and the wire has no resistance (since it's not modeled in the problem.)

Can someone explain why these dependent sources make sense, please?


texts: Protecting microcontroller from inductive loads

texts: I'm working on a project where I will be controlling a variety of loads (relay, solenoid, motor) from an Arduino and I'd like to make sure I build in enough protection for the microcontroller and other components. I've see a variety of solutions using transistors and adding decoupling capacitors, flyback diodes, and zener diodes. I'm wondering how one would choose between one or a combination of these options?


texts: Vacuum tubes versus solid state in specialist audio

texts:
There is obviously a large body of opinion that believes the use of vacuum tube amplifiers enhances some types of music.

My question is simple: Given that modern DSP techniques can mimic just about any response, why are vacuum tubes still used rather than the far more reliable solid state DSP programmed to emulate a tube's response?


texts: What are the required parts for an 8-bit computer?

texts:
I've decided that I want to build my own 8-bit computer with the WDC 65C02 CPU. The only problem I have, is that I don't know what the requirements to build one is in terms of other chips and components. With a modern computer, you get a motherboard, your CPU, RAM, GPU and storage disks and assemble it.

However with an 8-bit, I know that I need a CPU, EEPROM, SRAM, and thats it. I keep seeing Address Decoders, Asynchronous Communications Interface Adapters, and Versatile Interface Adapters. Each tutorial and design I see seems to incorporate a few or all of these things and I can't really find any documentation for them.

I know how I'm going to program it, what RAM and ROM I'll need and how I'll map it all, but apart from that,

What are the most basic requirements for a functional 65C02 computer with a PS/2 or alike keyboard, (hell, any keyboard for that matter), text and graphical video capabilities (such as VGA) and some form of sound?

Also, is there a certain model of compatibility for the 65C02 or will virtually anything work?


texts:
For all the other stupid things I often do, I've found ways to boobytrap myself.  For example keeping my wallet on the floor where the door opens - I can't help but stumble on it when I leave the house.  But here's an electronics parts problem that has me stumped.

I sometimes accidently throw out IR LEDs as "nonworking" since they don't visibly glow when tested.   How can I prevent myself from doing that, at least to force myself to reconsider and remember there's such a thing as IR?


texts: I am thoroughly confused on this topic. How does "common base" even make sense? If the base is grounded then the transistor is turned off, so how does the input reach the output?


texts:
I would like to do a buck-boost using H-bridge topology. I found the LT8705. I have two questions I don't understand.

How to choose the inductor of H-bridge buck-boost? The datasheet is using boost mode to calculate, but I don't know why.

How to use only one compensator to compensate all the modes? (Buck mode, boost mode, buck boost.)


texts: Which wire gauge for a 250 ampere source?

texts:
I have two 6V 220Ah DC golf cart batteries that I want to put in series to make a 12V 220Ah output that I will connect to a 3000W power inverter.  My problem is finding the proper connecting wires for the series hookup between the batteries.  This website says I would need a 250 gauge wire:
http://www.cerrowire.com/ampacity-charts
but I haven't got a clue where to buy it since, when I went to Home Depot and another local electronics store, their wires were mostly from 10 to 50 amperes which makes sense for the normal 120V AC home wiring systems, but not for my situation.
A thought I had was to use two 2 gauge wires in parallel between the two batteries, but I literally have no experience so I need help.


texts: Is it possibile to manually wire a displayport cable?

texts:
I have to pass such a cable trought a small hole in a wall.
Since that the connector is to big to pass trough, the only way to do so is to cut the cable, pass it and than wire it manually.

Do I have any hope to do it successfully with a small loss of the cable quality?

Any suggestion on how to proceed?

I could always make another bigger hole in the wall, but I prefer to wire the cable, if that was possible.


texts: Is it hard to do 2 sided SMD PCB in oven?

texts:
As far as I am aware, and please correct me. If we have a 2-sided PCB with SMD components on the top and also bottom, first we shall put components on the top side and solder them and then on the bottom side and solder them. It could be done the other way around but the thing is that, it will be done on one side at a time. The soldering could be done by hand if the component side allows or we could use solder paste with hot air gun.
If we are to do a complex board then we would be using a reflow oven. For prototype board the components would be placed by hand and then the board would be put into the oven. For manufacturing at industrial scale the component placement would be done by a machine.
Now the question in my mind is, is it true that if we have to do 2-sided soldering of such a PCB it would be that once the one side has been soldered in the oven and we place components on the opposite side and put into oven again, the components would fall off from the first side due to heat in the oven? If this is true, how is this mitigated?


texts:
This is what is required by my motor: 176VDC and 6A (10A for security)
I think this will be complicated to find one on second hand market.
My house is powered with 230VAC single phase and 380V 3-phase
Maybe I should built it from scratch?
What are my options and what is your advice?

build my own transformer and add a rectifier bridge ?
Other one maybe easier?


texts: Monitor if TX+/- ethernet pins are sending data

texts:
I want to 'monitor' in a 'cheap way' if one device connected to Ethernet(100M-BaseT) is 'sending' packets or not. I only need a binary answer, I don't want to know the data that DUT transmits, only know if it is transmitting data or not.
I think that the best way is to monitor the TX+ and TX- pins of the DUT, but how?
I know that I cannot break the impedance of the cable, so it's correct to add another magnetics/transformer in the red square?
Ethernet is like a RS-485, so, theoretically, I can add another transformer while it has the same input impedance, right?
Thanks!


texts:
I recently replaced the battery in my APC Back-UPS CS 650 and of course I didn't opt for an original APC battery, but just bought a similar one from the corner electronics shop.

Apart from the label both batteries looked exactly the same, but still the old one used to provide 20 minutes of backup time and the new one only 10 minutes. The label on the original battery only states 'original APC replacement' and things like 'wash your hands when spoiling the acid contained in it'. Nothing indicated exact specs, so I just bought one that looks exactly the same and has similar voltage (12V).

So what is different, does APC really manage to put 14Ah in their original battery and still only have a 12V/7Ah form factor? Did I buy a bad battery? Is it a difference between deep cycle vs. non-deep cycle battery? Are there different types of batteries that I should have been aware of before buying one?


texts: Why does I2S have extra clock cycle in SCLK that is wasted i.e no data transferred?

texts:
I am getting different waveforms for I2S in different places, in one I found that the LSb is transferred after LRCK has toggled. In this device that is not the case.

It seems that there is normal I2S, left justified I2S and right justified I2S. The left and right justified make sense. However, the normal I2S has something peculiar about it.

Q: Once the LRCK changes polarity, the value of SDATA on the first rising edge of SCLK seems to be ignored. Is this a mistake in the datasheet? Why is this done? The image is below with the questioned part circled red.

Is this a mistake in the datasheet of CS4334? I looked into the "TAS3004 Digital Audio Processor with Codec" data manual page 2-6 and it showed an X for the first bit.


texts: How to setup Arduino on secure wifi network?

texts:
I'm thinking about an Arduino project that involves having an Arduino host a basic web server and then connect to a wifi network using a wifi shield or something along those lines. You could then connect to the Arduino via the network and control it.

Most of that sounds very feasible, however, how do you initially setup an Arduino on the wifi network? How does the Arduino determine which wifi network to connect to, if there are more than one? And what happens if its a protected network? And once the Arduino is on, how would one determine it's IP address.

I know, a lot of this stuff could be hard coded into the Arduino's code, but what I'm theorizing it that this could actually be a product that could be sold on shelves. So it would have to be easy to use and flexible for the average joe at home.

It seems like the Arduino device would HAVE to have some sort of LCD screen and basic controls/buttons on it so you could connect to the network and input the secure password, etc... Is there any other way to do this?


texts: Trying to understand Battery Chargers vol.2

texts:
The answer by Bill dubuque was very helpful and got me to read the complete datasheet of MCP73831/2, but there is one thing from the datasheet that I don't fully understand and is the cause of lots of confusion I've been having with my circuit (see below).

Assume that the switch is in position 3, closed circuit, for everything I'm discussing below.

For a long time I was wondering why the MCP73833 wouldn't provide 4.2 V at its output, when I apply 5V from a USB cable, if the battery is not connected. Instead, when powered with 5V at the input, the output of the battery charger is ~3.3V and the output of the regulators drops to ~2.8 V from the expected 3.3 V. Why couldn't I just remove the battery and let the Ireg current from the MCP73833 power the rest of the circuit? (Ireg defined by 1000(V)/Rprog(kOhm), in my case 1000/3.3k= 303mA ).

Well, after reading the datasheet (page 13, section 4.2) I believe I got closer to the truth. There is a feature called battery detection where a small 6uA current is sourced from the Vbat pin (output of the battery charger) and depending on whether the voltage rises to a certain threshold or falls below it, the IC will either not start the charge cycle or detect that a battery is there and begin charging.
A few lines below, the datasheet also mentions: "For a charge cycle to begin, all UVLO conditions must be met and a battery or output load must be present"

First question

Why isn't the rest of the circuit (the two LDOs) enough of a load so that even without the battery charging can begin, meaning current can be sourced?

Second question

Say Rprog is 3k and allows for a current of 1000/3k= 333 mA. That is almost exactly 1C, with the battery being 330 mAh.

a) How can simultaneous power and charging be achieved if there is no more current allowed by MCP73833 to power the rest of the circuit? Should I reduce Rprog to allow more current but exceed the recommended 1C, or can I assume that powering the circuit will take precedence over charging the cell? Nothing like that is stated in the datasheet of MCP73833.

b) If for whatever reason the IC is "smart" enough to power the rest of the circuit with some of the 333 mA, while the rest of the current charges the battery, how come then it can identify the two LDOs as this extra load that requires powering but earlier, without the battery connected, it coudn't detect it at all due to the battery detection feature?


texts: Why am I getting non-sinusoidal output for sinusoidal input in a mass-spring system?

texts:
A mass-spring system is represented by the following transfer function

$$ H(s) = \frac{s^{2} + 0.1s + 10}{s^{4} + 0.2s^{3} + 20s^{2}} $$

For a sinusoidal input I am getting a non-sinusoidal output, as shown below (input in gray, output in blue):

I am using the following MATLAB code to generate the plot:

t = 0:0.1:20;
u = sin(1*t);
lsim(sys_x1, u,t)


texts: Catch both sides of a clock change PIC interrupt

texts: I am trying to build an IR remote receiver using a PIC16F628A. To do that, I need to catch both the falling and rising edge of the external interrupt pin. From the datasheet it appears you can only receive an interrupt on one or the other edges. How would you recommend going about this problem?


texts: Resonant frequency and maximum signal width

texts:
I've seen resonant frequency being defined as the point where the input signal is in phase with the output signal (So reactance/susceptance is 0).
However conceptually, teaching material seems to link it mostly with maximized output signal width (It's never explicitly stated, just heavily implied: See band-pass filters).
In short, is there any actual link between the resonant frequency and the signal width? Or is the link only there for the special case of RLC circuits?
EDIT:
I'm trying to get a general intuition, hence the lack of specifics - but here is the example that got me on this train of thought for context:
  I
x=>-x--x
+   |  |
    R1 R2
V   |  |
    C  L
-   |  |
x---x--x

Excuse the ascii art for now, I'll look for something better.
(Input: V, Ouput: I)
I was trying to computer the resonance frequency on the above (I have no concrete values), and was wandering if the maximization of the output width (|I|) happens when I and V are in phase; same as a parallel RLC circuit.


texts:
I am totally new to electronics so I would like to have your help.
The project I would like to build is very simple but yet I don't know the name of the parts that I have to use.
So, I would like to have a relay that will activate a buzzer powered from a 3,6 lithium battery only when the 220 volt of the wall outlet goes off.A reset button would be perfect but not so necessary.
Please help me with the circuit and the part names.
Thank you.


texts: Can I get 9 V out with a 12 V input from the attached regulator?

texts: The 9V regulator in this datasheet has a 2V dropout voltage. However, in the electrical characteristics on Page 9, the datasheet says that you need 15V input to get a  9V output. Does that mean I can't get 9V out with a 12V input? Or am I interpreting the datasheet wrong?


texts:
While working on a schematic for a small development board, I was curious how much work it would be to support an external voltage source (ie. bench-top power supply) in addition to the ICSP header and USB port.

For two sources this is pretty straightforward - I would normally run VBUS from the USB port to the emitter on a BC807 PNP transistor with the base driven by the ICSP power pin (self-power dominant configuration).

I've never worked with more than two sources, so this is a bit of a puzzler to me. Ideally the user would be able to (mistakenly) wire VDD to multiple sources without damaging the board.

(Be kind, first post!)


texts: Audio amplifier with strange open loop, is it an oscillator?

texts:
straight to the problem. Here is a picture of frequency response of my amplifier in the simulator (LTspice or Pspice both give same results).

Normally, in the open loop i see a phase of 90° which normally tends to increase. In this simulation I see a phase that starts at 180°.

Generally, an amplifier that does not oscillate, when the band touches zero, the phase is not more than 180 °. So, is this amplifier an oscillator, or is it the other way around?

EDIT: This is the frequency response bypassing the input capacitor.


texts:
Given

Find:
“v” and “i” for t>0

I found init conditions:

i(0-)=i(0+)=0A

v(0-)=v(0+)=0V

i(infinite)=3A

v(infinite)=4*3A = 12V

To obtain transient response we need remove Current Source with shorted circuit and write KCL and KVL but I don’t understood is it right to short Current Source (as it for Voltage Source) and can’t write proper KCL and KVL for circuit! May you help?


texts: Any option to upgrade library in tinycad?

texts: I used tinycad to draw circuit schematics for my project. But CD 4017 IC was not there in its library. Is there is any possibility to upgrade tinycad library?


texts: How can a phone wire have multiple frequencies at once?

texts:
How can a phone wire have multiple frequencies?
In my Networks Textbook about DSL vs Dial Up it says the following:

The residential telephone line carries both data and traditional telephone signals simultaneously, which are encoded at different frequencies:
• A high-speed downstream channel, in the 50 kHz to 1 MHz band
• A medium-speed upstream channel, in the 4 kHz to 50 kHz band
• An ordinary two-way telephone channel, in the 0 to 4 kHz band

From my basic knowledge of physics, the frequency of a wire is the rate at which it reverses the polarity.  So if you have one wire, how can the electrons be simultaneously changing polarity 4,000 times/second (for talking on the phone) and also 50,000 times/second (for using DSL)?


texts: modulate a 555 pwm circuit based on an input voltage

texts:
I am trying to vary the duty cycle of a pwm signal based on an input voltage (higher voltage = higher duty cycle). I currently have a functional astable set at my desired freq (50Hz) and it is fed into a monostable. This was just my natural starting point. I am trying to use timer circuits to do this but am open to other non-microcontrolled options.
edit: I was not very clear. This is meant to drive a servo, similar to the needle of a speedometer in a way. The higher the input voltage goes the higher the servos duty cycle should go to advance the servo. As rough boundaries, 0 volts in should be min servo duty cycle of 5% pwm, and 2 volts in should result in a pwm out with 10% duty cycle for max servo deflection. I am at a loss when it comes to implementing a "voltage to duty cycle" controller and am in need of some guidance on an approach. Sorry about the clarity
Non-linearity is okay, probably up to 10% but less is better.
This is a one off so I can "make it work" by fiddling with r and c values to make it fit my needs.


texts:
I have a broken Kegerator and need some insight. I'm familiar with electronic circuitry, but far from an expert. Everything (temp display, internal fan, change set temp) appears to be working as it should, except the compressor never kicks in. I believe I narrowed down the issue to a relay on the circuit board (picture included) that tells the compressor to turn on. I verified this by shorting the relay and then the compressor kicks in as it should.

Few Questions:

Does it sound like this relay is indeed the issue? If not, what else should I be doing?
It appears the relay is a SANYOU SMI-S-112LM : http://www.sanyourelay.ca/public/products/product_list_new.php?series=34&listby=0

Where can I buy one of these? All I can find online is bulk items. Is there perhaps a different manufacturer that I could use?

With a new relay and a little soldering work, I imagine I can get this up and running again. Thanks for the help!


texts: Feasability of an Arduino indoor positioning system using BLE

texts:
Our project is to guide a blind person in a known environment (here it's an exposition hall), and we need to have a precise way of figuring out where the user is. Our current solution is to use something like WPS, but with bluetooth beacons.

This is however our first project with Arduino, and we're not quite sure if we're going the right way about this. So far, we're thinking of getting a compass module , a bluetooth shield, and 3+ BLE beacons.

For the compass, I saw the HMC6352 but it's not sold anymore I think? Then for the shield, there's the WRL-13019? I think? I have no idea if that's even what I'm looking for. And I'm not quite sure where I can find BLE beacons either; I was thinking iBeacons should do the trick but they're a bit more expensive than I had planned...

So my question is: Can it be done this way, with a good enough accuracy (~1 meter), and with a low budget (~$100)?

Additional information: The system is placed on the user, most probably strapped to the arm. The communication with the beacons will be done from there, as well as the calculations. The user will interact with the system through a 3-buttons pad placed on the cane.

The environment is supposed to be as complex as an exposition hall, but we can aim higher, although the prototype tests will be held in a smaller room (~60m², I think).

Budget range is around $100, Arduino itself excluded. A UNO is already provided to us.

Originally from Feasibility of a Wi-Fi Positioning System, but I figured Bluetooth might be a better idea (...right?).


texts:
I am a kind of software man, and I decided to learn how the computer works under the hood. So I have read a few computer architecture books, and now I have a decent understanding about how digital circuits work (at logic gates level). I want to design and build an 8-bit computer with a 16 bit address bus. I wanted to build it in a PCB with 74 series ICs, except RAM and ROM chips. I have been using a visual digital circuit simulator called LogicCircuit.
But while designing the ALU I have encountered the problem of testing, I cannot test that every works properly, I can only test it manully, but I wanted to have some kind of Unit Testing that I can program and run. For that purpose I discovered HDL (Hardware Description Language). But all the tutorials I have seen show how to build functionality coding and then a synthesizer compiled it to logic gates, so I think I wouldn't learn that much. (1) Should I design everything first visually and then port every logic gate to HDL and test it? (2) Do I simply have a misconception about what is HDL?  (3) Do you know a visual digital circuit simulator which supports testing (maybe a scripting language)? (4) Should I simply do everything in HDL?  (5) When should I use HDL and when should I use visual tools?
By the way, currently I am using Autodesk Eagle to build the PCB.
Thanks, Pedro


texts: How to change the frequency of AC supply?

texts: Im using an inverter to convert Dc into Ac from battery.  I want to control the frequency of the alternating current ie., increase and decrease gradually (eg: 1Hz 2Hz 3Hz... 60 Hz). Is it possible to control the frequency?


texts:
I have a PIC16F877A microcontroller with a 19.6608 MHz crystal, wired for 12V ICSP. I can reprogram the chip just fine, and it runs almost flawlessly (it's blinking an LED right now as I type). Only thing is, the PIC seems to latch up or stop its oscillator when I get up from my chair and touch the metal frame of the table it is sitting on. I sit back down, touch the metal frame again, and the PIC starts blinking the LED again. Sometimes it takes more than one "cycle" to get the PIC started again. Weird...

I made sure to select the right oscillator mode (HS), disable the watchdog timer, set unused pins to outputs, use decoupling capacitors, etc. I made sure I selected the correct capacitors for the crystal I'm using.

Any suggestions as to the cause of this flakiness?


texts: What is this symbol with a uF rating? Some type of capacitor?

texts: This circuit diagram has a symbol I've been unable to identify, which I've indicated with a stylish green arrow. I'm guessing some sort of capacitor based on the uF measurement, but I haven't been able to confirm that in my search through general circuit symbol lists or for capacitor symbols. Can someone clue me in?


texts: Concerns About Solar Charging Tree House Lights

texts:
I'm Building a lighting system for my tree house with 4 LED work lights I picked up at the hardware store. I want it to have solar charging and be operable via one switch. Theres alot of background so skip to the end for just the question.

simulate this circuit – Schematic created using CircuitLab

Here is my plan so far;
   I have made a schematic. The LED Lights are made to run on three AAA batteries in series. I wanted to be able to turn them on with one switch so I have them hooked up to 12 AAA batteries in series/parallel as shown. The ends of the battery holder(s) will run up to the celling where the lights will be hooked up in paralell.

For the solar aspect I found some cheep 4.5V 80mA Solar cells online and put 5 of them in parallel to give me 400mA charging, staying under/at a 10% recharge rate (1000mAh on per battery X 4 parallel groups of batteries).  Add a diode to prevent backdraw from the solar cells and a switch to turn the lights on and off and thats about it.

Heres as much specs as i can get from each component and a link to each.

Solar Cells-4.5V 80mA

Batterys-1.5v,1000mAh,NiMH

Lights-Run off 3 AAA batteries usually, 27 LEDs in parallel with a 0.25Ohm? Resistor(red,green,gold,gold). I know theres a way to calc. the current draw but I'm having real trouble with that.

Here's my two main questions that I'm concerned about:

-

1: Will the batteries charge and discharge correctly? Elaborations:Are the solar panels hooked up so that they will correctly charge the batteries? Can the batteries actually charge and discharge in series/parallel like that?

2: Will the lights being powered With the correct current and voltage? Elaborations: If each light is supposed to be powered with three AAA Batteries, will they each get about the same amount of current and volts in this setup?

-

Also here is a diagram of the Layout to solve any confusion (And cause diagrams are just cool).

This is an update from my previous question witch I left open ended without any specific questions. After a little more digging, I was able to ask the right questions and find out what I needed: Lesson Learned


texts: Representation of Photovoltaic cell and BESS in Microgrid by first order transfer function

texts:
I am working in the are of frequency control of Microgrid and have come across many publications (For example: https://www.sciencedirect.com/science/article/abs/pii/S0142061515005220 (Pg 3,5)), wherein the transfer function that relates power output and the solar insolation in a photovoltaic (PV) cell is represented as a first order lag transfer function. Also, the transfer function that relates the deviations in power output of the battery energy storage system (BESS) and the deviations in frequency by the first order transfer function with lag.  Like:
$$G_{bess} = \frac{\Delta P_{bess}}{\Delta f} =\frac{K_{bess}}{1 + sT_{bess}}$$
My question is:
How to mathematically prove starting from the physical equations that such relations can be represented by a first order transfer function? Is there a mathematical proof or mathematical justification using which we can obtain these transfer functions?


texts: Why is serial EEPROM preferred over parallel EEPROM?

texts: In the wikipedia page for EEPROM: http://en.wikipedia.org/wiki/EEPROM it is given that "Parallel EEPROM devices typically have an 8-bit data bus and an address bus wide enough to cover the complete memory" and also "Operation of a parallel EEPROM is simple and fast when compared to serial EEPROM". In that case why are serial EEPROMs becoming more popular than the parallel EEPROM?


texts: Decoding negative millivolts counts in ADS1241 24 bit ADC

texts:
I am using an ADS1241 to measure thermocouple signals.

I have applied a millivolt signal differentially to channel AIN4 and AIN5 using a stable and accurate millivolt source.

The thermocouple signal ranges from -8.9 mV to 70 mV. I want to cover the whole millivolt range using this ADC.

I have set the PGA to 1.

How can I measure the negative millivolts?

I applied -10mV to the input and getting counts FF47D3 in hex. The reference is 1.235V and the format is bipolar. I am not able to decode these ADC counts.

Datasheet for the ADS1241.


texts: How offset current and offset voltage affect output of single-ended diff amp?

texts:
The differential amplifier inside the OpAmp have offset current and offset voltage which is said to cause an output error when there is no input.

This makes sense to me if the output of the differential amplifier is a differential one (double-ended output) in which each output is referenced to one another. So that if one side is higher than the other, it will cause an offset voltage at output.(so output is not zero anymore)
But I don't get why that also applies to diff amp inside the OpAmp that has a single-ended output. The output of singled-ended diff amp is referenced to ground so that if one side of diff amp is in offset compared to the other side it won't matter since I'm getting the output in only one side (I think)
This is a simplified schematic diagram of the 741 OpAmp in which the diff amp is single ended:


texts: Is draining a Li-Ion to 2.5v harmful to the battery?

texts:
I am running one of my projects from two 2000mAh Lithium Ion batteries wired in parallel

I decided to let the battery run until it died, just once, to see how long it would last. It lasted 25.9 hours, and when I checked the voltage on them, they had gone down to 2.5V.

I've read in many places that Li-Ions should be 3.7V when full and 3.2V when empty, but I've never seen anything about 2.5V or anything lower than 3V for that matter. I have heard and seen people talk about "overdraining" a Li-Ion/Lipo, and that when it goes below 3V a microchip disconnects the battery to protect it from discharging too far.

In this case, my battery still works, and it is charging right now, I don't plan to run it down that low again, but if it were to happen again, is it a big problem? Could this effect the longevity/performance of the battery?


texts:
Working on some VHDL I for Xilinx virtex parts, I found that the code I inherited had attempted to implement user encoding for the state variables used in the various state machines in the design. The toplevel.syr file was found to contain listings of the state encodings for some of the state machines, but not others.

I'm curious whether the .syr file is the definitive place for such information, and it's simply that XST has somehow synthesized something other than the expected state machine in some cases, or if perhaps there's another report somewhere that would show the 'missing' state machines.


texts: How can I galvanically isolate 5V 1A DC power?

texts: I want a circuit to pass on ~5V DC at ~1-2A, but galvanically isolate it. Can somebody help? THX


texts:
You read the title and that's what I am trying to do.

Synopsis: I have a young son who is determined to catch Santa (to what ends I don't know). He even dreamed up using some kind of pressure plate and connecting it to a light that will turn on when Santa steps on it to get cookies. I would love to help him build this contraption. We have been down at RadioShack repeatedly.

More practically, I am not an EE and have minimal experience with (and time for) bread boards.

So, I was hoping some people here could give some guidance.

I have been evaluating Little Bits but not sure which way to proceed. I am thinking a pressure sensor under a carpet near the cookies that somehow trips a relay and turns on a light or something else clever.

Naturally, I don't want this to succeed just yet in capturing Santa; consider it a lesson in drafting better requirements and a more complete design. Next year we can drive a new design for catching Santa.

So, while the ultimate goal is a bit childish, is it a serious enough question and maybe I can jump start my son's interest in engineering.


texts: I need some component selection help with a nixie tube AVR speedometer

texts:
I know enough to be dangerous, i can build circuits and make minor changes but i am not an expert.  I put this together after looking at schematics i have found online and i need some help getting the right components.  The individual components i cant take credit for but i think the idea and final unit will be unique.

This is a speedometer for my 1950 Studebaker.  It is a modern charging/ battery system.  Should give between 11 and 14 volts.  Both power supplies i have, the avr i am familiar with and have, i used it to control a skeeball machine.  It uses a pulse generator on the transmission (new Dakota digital sen-01-1), i then modified the self powered sine to square wave circuit to run off of available power.  I am hoping this will make it more sensitive.  I am using the Russian equivalent to the Nixie drivers 74141.

1: i would like to control 2 of the elements without the need for a chip what should i do here? (mpsa42 and a 33k resistor? I have!)

2: Between the at mega avr and the 74141 (K155ID1)? do i need anything?

3: Do i need to do something special on the input voltage for these 74141 s?

4 and 5: I would also like to use ne2 lamps to replace my hi beam and left and right turn indicators.  These are roughly a 12v signal i have 5v and 170v what circuit should i use?  Hi beam may be on for long times.  (tip 102?)

6: (not numbered on schematic) Is my use of the sine to square appropriate.

MY hand drawn schematic: http://i871.photobucket.com/albums/ab280/FortyTwo-edo/nispedov1.jpg

Sorry this is long but i have been looking at this for awhile and finally need to get it prototyped before snow so i can test it before i build the case.

Thanks
Ed Owens


texts: Does the VU meter on audio amplifiers measure the input or output level?

texts: Does the VU meter on commercial audio amplifiers measure the level of the input signal or the level of the amplified signal?


texts: Identify this connector (external 12V christmas tree lights)

texts:
Can anyone help me identify this connector?

(image from Digitec/Galaxus here)
It appears to be a 3 pin external (some degree of waterproofing) connector marketed as for "Christmas lights" but in this case used for other exterior lights. What I actually want to buy is an extension cable, or more precisely this extension cable, to connect a set of lights I have just installed, but Digitec/Galaxus (same people) now tell me that the cable is out of stock indefinitely. The manufacturer of the lights is I believe STT AG but their web site is less than helpful. Searching for the type of lights "fascinating lights" is unhelpful. I suspect this cable can be bought from someone else for very little money if only I knew what the connector is called.
Note that the description in the digitec page of this being a 220V connector is incorrect. There is a transformer with the light set built into the plug, and the connection is low voltage. So don't get hang up on finding a mains voltage part.


texts: When I switch my oscillating floor fan on it turns the audio off on my PC

texts:
When I switch off (not on, or up - there are 3 settings - only down and off) my oscillating floor fan my PC audio drops out. My PC audio is running through a USB midi controller (novation switch.)
To get it back on I have to unplug the USB from the back of the controller and plug it back in again.
What is going on here?  What can I do about it?


texts:
I have a model of an address-decoder and problems understanding it.
The circuit shows 4 16 x 4 memory-chips that are connected to a 64 x 4 bit memory.
Could someone explain to me what address each block occupies?


texts: Does the density of the brushes used in a DC motor increase efficiency?

texts: I'm doing a science paper about DC motors and efficiency and I need to test one part to see whether or not the efficiency increases or decreases. I think I will do the brushes and I'm wondering if the density of the brush affects the power outage/efficiency of a dc motor at all.


texts: 74190 up/down decade counter starts from 5

texts:
I've been connected pins input A and C into VCC so the logical number is 1 and input B and input D with 0. The counter starts with 5, but it doesn't clock or change from number 5 into 0 (5,4,3,2,1,0,5,4,3,2,1,0) as I need.

What should I do for this 74190 so it will count down from 5 into 0 and so on?


texts:
Consider we have an array declared as  :
reg arr [n-1:0]

This array has n elements each of 1 bit and if I need to put a zero for example in all of its elements , do I need to do a for loop from 0 till n-1 or is there is a shorthand syntax for it in Verilog ?


texts:
I'm facing problem when reading data register. The SPI communication works perfect, all the registers can be write/read.
The data register show -1 (which in datasheet indicates that there is a problem in Vref, checked with setting REF_DET bit and reading STATUS register which shows 0x60).
I'm using adc in BIPOLAR MODE, the steps performed to initialize adc are:

send  0x000A to mode reg.( this sets adc in continuous mode with 16.7 Hz update rate).
send 0x0030 to conf. reg.( this sets adc in bipolar, Gain 1, reference detect ON, BUFFER ON, Channel to 1 ie AIN1+ and AIN1-.
send 0x60 to IO reg. to check p1 and p2 are working.

Please advice why is this happening am I giving wrong Vref, but the datasheet show Vref can be in between 0.1-AVdd and for this I can read upto +-AVdd-100mV (BUFF ON).
Please see attached image for reference.
I'm trying this CKT from a week now, monitoring Vdd mode works gives some integer value and STATUS reg. shows 4 in this case.


texts: Can all surge protectors wear out, and how would you know if this is the case with the surge protector you have?

texts:
This question follows from this other question where the OP mentions that:

  I know MOVs inside surge protectors degrade over time

Based on this it seems that surge protectors eventually deteriorate past a point where they do not provide (expected) protection against power surges.

The questions I wanted to ask about this:

Is it correct that surge protectors degrade, and if it is, what causes this?
Is there a rule of thumb for determining how long a surge protector can last before needing to be replaced?
Are there ways to determine if a surge protector is old (or otherwise faulty, for that matter)?


texts: Representing feedback circuitry as two-port networks

texts:
I'm taking an electrical engineering course and we are covering the effect of feedback on the bahaviour of amplifiers. I learnt the 4 basic topologies, and how with each configuration the feedback circuit can be replaced with a two-port network. It's summarised in this image I found on Wikipedia:

However, I can never figure out quite why these models are chosen. With the series-shunt connection on the bottom-right, for instance, my lecturer explained that the choice of hybrid parameters was because "the input is part of a series network and the output is part of a parallel network". Another source says something along the lines of "the feedback network and the main amplifier share the output voltage and input current".

Could you please try to get me to appreciate the choice of h, g, y and z parameters intuitively? Is it purely out of convenience or will it simply not work in any other way?


texts: Why are many IR receivers in metal cages?

texts:
I'm guessing it's a Faraday cage around the receiver, but don't know why they might need one. Is there some sort of common interference around 38kHz (their operating frequency)?

It's the only component I think I've used that gets this special treatment. A larger cage may be around one in a VCR,
and a little baby cage sometimes appears around the standalone PC mount component:

Thanks for your insight!


texts:
Simple question, i need to use 3 shift register to control 6 analog switches and 12 leds with only 6 digital outputs, nothing difficult BUT my IC provider doesnt have the clasic 595 in DIP package, so i was wondering to use a 594. Because i'm using analog switches for analog signals, it is very important that they all change at the same time, 595 has latch outputs with OE, wich is perfect, 594 just has a Rclk to pass with a pulse the data from Shift Registers to Out Registers, so my question exactly is :

Can i use ONLY this Rclk to control each IC (1 for analog switches and 2 for the leds) that way i put all the Shift Reg clk together so data goes thru all 3 IC and the Reg clr also together cause i need to have a LOW output everywhere at the power on of the system.
SO : 6 outs pins from microcontroller = 3xRclk, Serial data, Sr clk, Reg clr (Sr clr are put to high)

Thanks


texts: Capacitor and ferrite beads when to use which?

texts:
In this question Ferrite beads used to filter high frequency noise.
Capacitor also can be used to reduced noise and filter out high frequency noise.

Are they have the same effect on filtering high frequency noise or reducing EMI?

When to use ferrite beads and when to use capacitor?


texts: Need of self testabilty code inside embedded firmware modules?

texts:
I have a question to ask about the self-testability code inside a firmware module.
I have developed code, and it was in a shamble, and I was clueless about firmware architecture too. Later I found great articles about firmware architecture, for example, Developing a flexible firmware architecture, and they put emphasis on modularizing your firmware in to modules.

I have the firmware with the associated modules:

adc_module
EEPROM module
SPI module
Algorithm1 module
Algorithm module

I don't have an RTOS here, and I found the inclusion of testabilty code inside each firmware inside those articles :D.
Well, I'm working on 8-bit PIC microcontrollers, and I would like to know whether I'm shooting over the head or on the right path.

I would like your suggestions for the 'self test code inclusion'. And if I need to, what sort of functions do they perform inside the modules?


texts: I Have a simple question. I have a circuit that become 1 when it recognize a sequence 1, 2, 3 in a certain register. And it works great. But the second part of the problem asks that the output of the circuit remains to 1 until in the register comes 000 sequence. How can I do this with flip-flops etc.?


texts: I have been simulating analog circuits where the input resembles an OFDM signal, but with lower frequencies. Right now I am generating the input signal with MATLAB. I now want to have a physical implementation of the circuit. Can anyone please suggest which function generator will be suitable for this kind of operation? To be more specific, I would like to generate a signal which is the summation of sinusoidal waves with frequencies ranging from 2MHz to 100MHz and phase of pi or -pi. And the ideal scenario would be if I can generate an analog signal based on a given digital input.


texts: Can I use an 12v 6Ah drill battery to power an 8amp pump?

texts:
https://www.screwfix.com/p/milwaukee-m12-b6-12v-6-0ah-li-ion-redlithium-battery/674FJ?tc=VB8
Is it safe/possible to convert this to be used with an electric circuit to power an 12V 8A water pump?
They have 12V DC output adapters, but they are limited to around 2A output:
https://www.milwaukeetool.eu/en-eu/m12-compact-charger-and-power-source/m12-tc/
I've read electric drills draw between 4-8A, so would it be safe just to connect this battery directly to the circuit?
Would I have heat issues from drawing 8A continually until 100% of the battery is spent?
Thanks.


texts: When performing nodal analysis, should you simplify a circuit first?

texts:
Given an RLC circuit, should I simplify all components to their equivalent admittance/impedance before using nodal analysis?

The circuit in question is below:

Or should I perform nodal analysis on the circuit as is?

So far, I've attempted to simplify the parallel inductor/capacitor pair, the series inductor/capacitor pair, and the parallel inductor/capacitor/resistor so that I have a single node V1 (image below). The algebra is getting pretty tricky though so I think it might be wrong.


texts: Why there is a high inrush current when the microcontroller start-up(CC430f5137 from TI)?

texts:
simulate this circuit – Schematic created using CircuitLab

In my application, I need to measure the current consumption of the mcu (cc430f5137). To measure the current of the mcu. I insert a 10ohm resistor at the Vcc. Then, I connect the power supply to the Vcc and  observe the voltage across the resistor so that I =V/10.  I found that the current at start-up is around  80mA@1.8V  and 200mA @3.3V. It will last for a while and decrease gradually. Below is the picture of the waveform under 1.8V and the diagram of the board. The division of the waveform is 2 ms/div.

What may cause such a high current at start-up? Is this normal and how to solve this problem?


texts: PCB markings - What components might have component designators TB1, TB2 etc?

texts:
Looking at a PCB, there are 4 components marked TB1, TB2 etc.

I believe that the markings mean terminal board. What exactly is a terminal board?

Update: Unfortunately I cannot show a picture of the actual components. It looks very similar to a fuse like this. No markings on the component.


texts:
I want to build something that behaves like a regular magnetic compass, but using this electronic compass and some motor what will rotate the arrow pointing to the north.

So I think the motor must satisfy the following parameters:

360 degree continuous rotation
Rotation to the specified angle

Motor of what type should I choose?


texts: Driving a DC motor (in one direction) with a microcontroller pin and an opto-isolator

texts:
I'm supposed to design a circuit for driving a DC motor with an opto-isolator and a microcontroller pin.

The motor is supplied with 12V, and its power is 5W. The opto-isolator has to isolate the motor and the microcontroller. The working current of the opto-isolator diode is 6mA, which produces a current of 2.2mA in the collector of the opto-isolator transistor.

So, the motor needs a current of
$$ I_{M}=\frac{5W}{12V}.$$
The collector doesn't supply nearly enough current for the motor. So, I was thinking about adding another transistor to the existing one, making a Darlington pair. But, I have no idea how I should calculate it because I don't really have a base current to work with. I also don't know much about Darlington pairs or opto-isolators and I don't know how I can saturate the Darlington pair in this circuit.

Keep in mind that I'm not using any specific components. I'm only supposed to come up with an idea of how to accomplish the given task and calculate the values of the components I'm using. Here's a picture of what I've had in mind:

simulate this circuit – Schematic created using CircuitLab

Lets say the voltage drop across the opto-diode is 2V. R1 can be calculated as
$$ R_1=\frac{5V-3V}{6mA}=330 \Omega .$$
I could use some help with the rest of the circuit from you guys (if the idea of this circuit is even correct).


texts: Accelerating Graphics rendering in STM32F7

texts:
I have a framebuffer that is created on SRAM with LTDC that is everything is written to that buffer, images, icons,..etc. and get displayed to the LCD screen. That works fine.
but the screen size is 320*240, I overclocked the CPU, but still when the framebuffer is cleared, I see some slowness, it doesn't clear the buffer that fast.

I'm thinking about DMA2D, but how would that work in my case ? I have just a single buffer that I'm writing data to it, and I would like to copy it to LTDC hardware that fast.


texts: I am sending some values through a serial port from the dsPIC30F4011 to matlab. When the ICD3 is connected and I am working in debugger mode, the values are sent and received perfectly as expected. When I program the dsPIC and remove the ICD3, the serial is not working anymore. So I guess my question is, what changes between debugger mode and programmer?


texts:
I'm using some CMOS chips (4021 shift bit register, CD74HCT164E serial in parrallel out, 4066 quad billateral switch, etc...)

I'll have some parts of the circuit on or off, but to economize maximum of I/O I try to group a maximum of "common pins". For example the LATCH pin of the 4021 as I will always latch before reading and I only need to read one register at the time, will just ".

Some parts of the circuit will stay off for a long time. I would like to know if I can unpower them but continue to send bits like on the LATCH pin of the 4021 without damaging them ? (Like adding a transistor on the +5V)


texts: How does CLKOUT works on the LTC2323-12 ADC on "High-speed" speed mode?

texts:
http://www.farnell.com/datasheets/1833817.pdf

I was assigned a task where I have to connect an LTC2323-12 ADC (analogic to digital converter) to an FPGA.

Reading the LTC2323-12 datasheet seemingly it has two ways to be controlled. One way is through the SCK (clock-like) input that cycle by cycle shift the ADC results out of the ADC to SDO port.

The other way is described as a "high speed" that can "ease the timming requirements for the FPGA" (would you clarify this for me?) , this last one method is trough the CLKOUT signal, which is seemingly a Clock that comes out of the ADC that is matching (or latching) the ADC results out of the SDO port. Is that correct? Did I get it correctly?

So do I have to design the FPGA module in order to output the CNV signal of startup, then keep it for TCNVH nanoseconds, then release it, then just wait until ADC AUTOMATICALY send the first CLKOUT, so I can register it and count 11 more of these CLKOUT, while passing the SDO data out to my own registers on each of these CLKOUT cycles?

Then after the last 14 CLKOUT clocks, I must design a counter that trigger a valid signal that will start another counter of TDSCKLCNVH nano seconds, and at the same time porting out of this register register and a "Finishing" signal (so another top module with the same clock than my fpga module, can make use of these signals in another moment.

I would like you to correct me if I misunderstood something about the behavior of the LTC2323-12 ADC and the way to approach it. Thanks in advance.


texts: How to find Vthreshold and K (or beta) in Pspice/Orcad

texts:
Regarding M2n7000 transistor in OrCAD, I want to find its Vthreshold and Beta (or k) by its edit PSpice model.
This is what I get :

And by Vthresh and Beta (or k ) I mean the parameters of this formula :

By the way, regarding This Thread

I know the formula for K, but I cannot find all of its parameters in the model I mentioned above.
Thanks.


texts:
I'm a little unfamiliar with circuit breaker specs and confused by this circuit breaker datasheet:

https://www.waytekwire.com/datasheet/46974.pdf

On the second page, it says that it takes more than 1000 seconds for the circuit breaker to trip at the rated current (100%).

So does that mean that a 30A fuse breaker will trip more than 16 min after a 30A current runs through it?

I understand that current spikes are usually pretty high over a short period of time, but my application is a solar panel that might accidentally produce too much current gradually (like the clouds slowly clearing) for my MPPT charge controller to handle.

Is there a better option I could use?

Edit:
For those confused about why I would need a fuse on my MPPT, this is the source I used to understand the problem (but with fuses instead of circuit breakers):
https://www.windynation.com/jzv/inf/how-properly-fuse-solar-pv-system


texts:
I need a circuit or component which converts bipolar voltage to bipolar current. I have found the XTR111 from Texas Instruments and the 1B22 from Analog Devices. However, they only convert 0-10 V to 0-20 mA current.

I to need convert -10V-0V to -10mA-0mA too (the opposite polarity range). How can I do that? Or can I add a circuit to work with 1B22 or XTR111?


texts: Different conductors in the electical circuit

texts:
Recently my brother has decided to change conductors in the home's electrical circuit.

We had aluminium conductors and now we are going to replace it with copper conductors, but my friend told me that we'll pay more for electricity with copper conductors.

I can't understand whether is it true and, if so, why.

According to my opinion, the less energy loss is (due to heat dissipation), the more effective (cheaper) the circuit is; energy loss is proportional to material's resistivity.

My friend told me that with the resistivity loss i get increased electrical current and higher costs.

Please explain, will I get increased electrical current and higher price and why.

Thank you!


texts:
A couple years back in my Digital Electronics class we designed circuits in NI Multisim and then used Xilinx Impact to put it on a FPGA board via USB.

It has been a while since I dealt with that stuff and I am again interested in designing circuits doing more with it. I really have no clue what board I used in class other than it was the size of a computer motherboard and had a small breadboard for sensors and to light up led's, control motors, etc.

What kind of board do you recommend for this beginner use and future?

Also if you have any software/applications that would be helpful, please suggest.

Just found a great article: http://hamsterworks.co.nz/mediawiki/index.php/FPGA_course

Edit:
Here is a couple of questions I have created after some answers.

How do I know if a board can take PLD Logic from Multisim?

What can I use the ports on the board for (serial, expansion headers)?


texts:
Brief explanation: From the figure above, (B) is an electrical motor and (A) is a Dynamo, the red mark is a rotating rod connected to the dynamo. The dynamo is supplying power to the motor (B), hence the motor is getting more power which in turn makes the rod rotates faster.

Is the rod RPM going to keep increasing non stop or is it going to stop at a certain RPM and not increase any further?


texts:
MIC4605-2YM Datasheet

Given the circuit above what is the proper way to drive this H bridge in a manner where I can change the motor direction. the datasheet shows a sample circuit of a full H bridge driver scheme, however it uses a version of the half bridge driver that accepts 2 different PWM signals. The version that I have accepts one signal and it handles the inversion.

Do i necessarily need a second driver in this case? Cant I just pull up the top right mosfet and pull down the lower right mosfet and then ill get my direction change. Obviously adding some dead time.

Or do I need a second half bridge driver of the same configuration? In that case at 50% duty cycle which way will it spin?


texts: SystemVerilog - Enforcing prevention of inline initialization of logic/reg elements used as flip-flops

texts:
Given a SystemVerilog design modeling an ASIC, how can I enforce the rule that all logic/reg elements that are used in flip-flops should not be initialized to a certain value?  Is there a directive that I can use in my code that would prevent this?
Here's an example:
module asic (...);
    logic a;    // this is fine
    // logic a = 1;    // but this is not fine

    reg b = 1;  // this is fine since it is not a flip-flop

    always @(posedge clk, posedge rst)
    if (rst)
        a <= 0;
    else if (b)
        a <= ~a;
endmodule

I think a check like this would be really helpful in ensuring that all registers in the ASIC design have a reset.  The tools I use are Verilator (for linting and simulation) and Yosys (for synthesis), but I haven't been able to find a related option in their documentation.


texts: Do revived dead batteries become less effective?

texts:
There's a common belief that once a car battery dies, after it gets jump started, it will never be as good as before, and will likely die again. I'm curious whether this is a myth, or if not - what's the science behind this. I have noticed previously that when a car battery first died, it started having more issues starting up in cold winters, but am unsure whether this is just a coincidence.
From my understanding, which is a from rather introductory electromagnetism course, is that in a simple circuit, a capacitor can be discharged and charged without any harm to it's capacitance.
I currently have a completely dead/flat 12V 8.5A lead acid battery from a motorcycle that wasn't used for a year. It seems it's not as straight forward as charging it with a trickle charger, because if it's below 3V, this particular charger won't detect it, so will require jump starting it to atleast 3V+.
The manual for the trickle charger also had stated, "Unless the battery was rapidly discharged... most 12V lead acid batteries that are at a state of charge that is less than 9V is likely to be worn out or defective". I'm aware that lead acid batteries loses effectiveness over time (I'm assuming, that equates to losing capacitance?), so it can't be as good as a new one.
But disregarding the wear/tear time factor, does having a battery that went flat actually damaged the battery internally vs. if this battery was used consistently? I'm debating between trying to save this dead battery (if even possible) vs. buying a new one.


texts: What does O stand for in V_CBO and V_CEO?

texts:
I have just bought this transistor. In the absolute maximum ratings, the voltage names end in O, such as V_CBO, V_CEO and V_EBO.

What does the O stand for?


texts: If I use multiple heatsinks in the same enclosure, does the thermal resistance at airflow of each heatsink change?

texts:
I am designing an enclosure with 2 identical heatsinks. The thermal resistance is rated at 1.50°C/W @500LFM. If I use 1 fan in the enclosure that produces an airflow of 500 LFM, will each heatsink (theoretically) have a thermal resistance of 1.50°C/W? If so, can I go even further with the thermal calculations and estimate the case temperature rise of the packages fastened to each heatsink, using that 1.50°C/W value?
Thank you all, first time posting here.


texts:
In most cars and trucks, a thick cable connects the battery directly to the starter (solenoid). Why don't these circuits have have any kind of overcurrent protection?

It is an accepted practice throughout the motor vehicle industry. Here are two separate standards that specifically exempt starter circuits from overcurrent protection. (These are both for watercraft where the consequences are even greater; you can't walk away from a fire at sea.)

  Each ungrounded output conductor from a storage battery must have a manually reset, trip-free circuit breaker or fuse, unless the output conductor is in the main power feed circuit from the battery to an engine cranking motor.

These are just examples; I have no doubt that organizations such as SAE and ABYC have similar provisions in their standards. Millions of vehicles are wired this way.

  All circuits, except the main supply from the battery to the starter motor and
  electrically driven steering motors, should be provided with electrical protection
  against overload and short circuit, (i.e. fuses or circuit breakers should be
  installed).

I am asking for the engineering rationale behind these exemptions. Even though the cable is much thicker than the starter windings, a mechanical failure or impact could still create a short to ground. The resulting current can easily exceed 500A and is enough to weld thick steel.

I understand that the starter demands far more current than any other circuit, but surely a cost-effective solution could be found -- such as a fusible link. Or am I mistaken?

Here are some possible reasons that don't make sense to me:

The cable is so thick (relative to the size of the battery) that it doesn't need protection. The starter will burn or the battery will explode before the cable melts. While this may certainly be true from a "protect the wire" standpoint, I believe this an even stronger reason for overcurrent protection on the starter circuit... to protect the entire vehicle.
The risk of a fault in this circuit is extremely unlikely. It is true that starters are sturdy devices and thick cables have more mechanical strength. However failures are still possible, and do occur from time to time in the real world. Furthermore the impact of a failure in this circuit can be catastrophic, leading to total loss of the vehicle or death. Therefore I'd expect the severity of the problem to overwhelm the (admittedly) low likelihood in a failure mode analysis.

Edit for future readers:
Most of the answers focus on availability. That is very important, but a secondary reason coupled to the choice of a fuse as the protective device. A breaker would mitigate the risk of being stranded due to a nuisance fault. (Someone mentioned the possible loss of steering, but all production vehicles including the Infiniti Q50 still have mechanical backup.) Fortunately there is a concise answer that explains why even a breaker or fusible link wouldn't be suitable.


texts: dsPIC33E External Interrupts INT0,INT1,INT2 not firing

texts:
I have read every post I can find and still do not understand why external interrupts are not triggering, the following is my initialization, it is not clean, as I am in the process of trying everything I can think of to make this work.

To simplify the problem, consider only INT1.

Update: It appears the flag is getting triggered, but the ISR is never being executed. The flag is not being lowered

void __attribute__((__interrupt__, no_auto_psv)) _INT1Interrupt(void)
{
IFS1bits.INT1IF = 0;    //Clear the INT1 interrupt flag
//U1TXREG='0';

m_Capture1 = 1;

}

// Hall Sensor A                | Pin 31    RPI24       RA8

// Disable all other pin functionality.
TRISAbits.TRISA8 = 1 ;
//LATAbits.LATA8 = 0;
ODCAbits.ODCA8=0;
CNENAbits.CNIEA8=0;
CNPUAbits.CNPUA8=0;
CNPDAbits.CNPDA8=0;

//INTCON1bits.NSTDIS = 0; // interrupt nesting enabled.
//INTCON2bits.GIE = 1;    // Global Interrupt Enable.

INTCON2 = 0x0000;       // all interrupts on rising edge.

// Reset Interrupt flags.
IFS0bits.INT0IF = 0;      //Reset INT0 interrupt flag
IFS1bits.INT1IF = 0;    //Reset INT1 interrupt flag
IFS1bits.INT2IF = 0;    //Reset INT2 interrupt flag

INTCON2bits.INT0EP = 1 ;
INTCON2bits.INT1EP = 1 ;
INTCON2bits.INT2EP = 1 ;

// Enable Interrupts.
IEC0bits.INT0IE = 1;    // Enable INT0 Interrupt Service Routine.
IEC1bits.INT1IE = 1;    // Enable INT1 Interrupt Service Routine.
IEC1bits.INT2IE = 1;    // Enable INT2 Interrupt Service Routine.

// Set Interrupt Priority.
//IPC5bits.INT1IP = 5;  // If all the IPC bits associated with
                        // an interrupt source are cleared, the interrupt
                        // source is effectively disabled.
//IPC7bits.INT2IP = 2;  //set low priority
//IPC0bits.INT0IP = 2;  //set low priority
IPC5bits.INT1IP = 4;    /*set low priority*/

RPINR0bits.INT1R |= 24;//0x18; //001 1000;    // Set Hall A - RPI24/RA8 set                     INT1
RPINR1bits.INT2R |= 51;//0x33; //011 0011     // Set Hall B = RPI51/RC3 set INT2
// Hall C RP39/RB7 is INT0 (not mappable)

I have verified with 100% certainty that the voltage on the pin is changing from 0 to 3.3V. Any help is appreciated.

Thanks,
Gary


texts: Transient modelling of RC circuit in NGSpice

texts:
I'm just starting out with NGSpice, and so far I have been able to model simple DC circuits with only a voltage source and resistors and have gotten the expected currents and voltages.  Now I'm trying to model the transient response of an RC circuit and am having a lot of problems.

Here is my netlist, called test-transient.cir:

Test transient circuit file for NGSpice.  2/4/2017
* Testing transient modelling with a capacitor
* The RC time constant is 680ohms * 1 uF = 0.68ms

v1 1 0 dc 10V
r1 1 2 680ohm
c1 2 0 1u

.end

I start ngspice and type the following commands:

source test-transient.cir
tran 0.5us 2ms 0
let

and I get the following output:

Here are the vectors currently active:

Title: test transient circuit file for ngspice.  2/4/2017
Name: tran1 (Transient Analysis)
Date: Sun Feb  5 20:08:33  2017

V(1)                : voltage, real, 4008 long
V(2)                : voltage, real, 4008 long
time                : time, real, 4008 long [default scale]
v1#branch           : current, real, 4008 long

Then I type "print V(2)" and every one of the 4008 elements in the vector is 1.000000e+01, i.e. 10V.  This can't be right, I expected to see a charge-up curve of the capacitor from 0 to 10V.  I also get the same result from typing "print V(1)", which in this case is expected.

Then I typed

plot v1#branch xlimit 0 2ms

and got this display:

The current drops from 0 to -600 (mA??) in less than 0.1 ms, which also looks wrong.

For the record, I had no problem modelling this circuit using the applet at http://www.falstad.com/circuit/, I got a voltage ramp-up across the capacitor in the expected time of 680us to 6.3V.

Any help would be much appreciated.

TIA,
Carsten