texts: Triac dimmer makes audible noise (hum or buzz)

texts:
I have some triac dimmer from IKEA (bought several years ago).
This dimmer makes audible noise (hum or buzz), very notable during night when it is placed on a bedside table. I failed to find the culprit.

I reverse engineered this circuit. This is the schematic:

I tried this:

Firstly I have accused the inductor (L1 in my schematic) that it is vibrating. So I glued it with hot glue. Didn't help. Then I shorted it with a wire (that inductor is not really necessary for dimming). This didn't help either. The noise was still there. So I ruled this inductor out.
Next I accused the ceramic cap (C3). I replaced it with film capacitor. Didn't help.
Next I accused triac (Q1) and its heatsink (it is sort of flimsy, could be vibrating). I removed this triac completely and put new BT137-600E there (I have built several dimmers with this triac, never noticed any noise). This didn't help either. So I ruled out triac and its heatsink.
I was desperate at this point. Next I accused capacitor C1. I removed it (it is just for filtering). Didn't help. So I ruled out this cap.
Next I accused capacitor C2. I have replaced it by another film capacitor, and the noise is still there.

Did I miss anything? How to figure out what is making this annoying hum (or buzz) noise?

UPDATE:
I'm using it with incandescent lamp. I tried different ones.
My dimmer (I created) doesn't make any noise with none of those lamps. The noise is definitely going from dimmer itself, not the filament of the bulb.

The noise is loudest when dimmer is about in the midpoint (around half brightness), it is quieter when brightness is at the maximum, and quietest when brightness is at the minimum.


texts:
I'm trying to implement the following schematic of a simple analog computer

The inputs are x and y, according to the text where I found this diagram the circles represent voltage dividers or potentiometers.

There are some things I dont get, for instance the divider in the feedback loop is \$ \frac{1}{k}\$ and it also states that k is between 0 and 1, so that means that \$ \frac{1}{k}>1\$, that implies that the divider should actually be an amplifier instead?

This is how I implemented it:

simulate this circuit – Schematic created using CircuitLab

With the resistor values I selected for the circuit, a=b=0.5, and \$\frac{1}{k}=5\$, which means that the final equation is supposed to be \$-0.2(0.5x+5y) \$. However, if one analyzes the circuit using superposition, we have:

$$v_o=-(ax+10by+\frac{1}{k}v_o)$$

or

$$v_o=\frac{-k(ax+10by)}{k+1}$$

What am I doing wrong? how is the circuit supposed to be to in order to get the correct output \$v_o=-k(ax+10by)\$?


texts: Identifying a resistor with a weird band combination

texts:
I am currently in the process of trying to repair a power supply that has had one of its DC rails fail. A resistor in the PSU has exploded and I am trying to find what value it is.

Band 1: White
Band 2: Brown
Band 3: Silver (Possibly Grey?)
Band 4: Gold
Band 5: Green

The weird thing is that the middle band appears to be silver, which should be invalid as far as I can tell. If you assume the silver is grey (although this is unlikely, as there still needs to be a grey colour as well and the band is metallic), it produces a value of resistor which is incredibly uncommon to the point it does not exist (91.8 Ohms 0.5%).

Apologies for the noobie question, I'm just stumped after hours of trying to understand why this is and coming up short :).


texts:
I Have 2S 8000 mAh li-po battery I want to use as an external power source for my DSLR camera (Canon 7D Mark II). Previously, I failed to power it with power bank and DC-DC converter, most probably due to weak prior power source. I know the best way how to care of li-po battery to use a BMS. I found some cheap BMS also with balancing (aliexpress, ebay, ...), but there is lack of proper datasheets and every product has the same specifications... So I decided to keep it simple and directly for now. It will be charged with external charger/balancer. Over discharge should not ba an issue, as my camera will shut-off when the battery is drained. Camera internal battery is 2S li-ion.
I know that unprotected li-po can by dangerous, so I decided to at least use a fuse to protect it. But I need an advice on which fuse to choose. The requirements are:

protect the battery from destroying if short circuit happens,
reversible when short circuit no longer exists,
as low voltage drop, as possible.

Camera should draw at max. 3A @ 8V + small power devices, so with sufficient reserve, 4A @ 8V is the max. output power. I went trough some PolySwitch datasheets for example, but I can not decide on my own if this kind of fuse is fast enough to protect Li-po. Thank you.


texts: Wrong I²C signal for some bytes on Atmel microcontroller

texts:
In theory I want to start I2C communication as a master with a slave.
Then I need to read 5 bytes of data.

In practice when I use the ASF provided by ATMEL what it does is start the communication as a master with the slave sents a byte and then reads 5 bytes.

The microcontroller I use is in ARM Cortex-M4: ATSAM4LC2A

This is how I initialize:

I instert these arguments into the initialization routine

/* Initialize I2C Master */
const i2c_master_settings my_i2c_master_settings =
{
    .i2c_port   = TWIM2,
    .speed      = TWI_FAST_MODE_SPEED,
    .sda_pin    = IOPORT_CREATE_PIN( IOPORT_GPIOA , 21 ),
    .sda_mux    = IOPORT_MODE_MUX_E,
    .scl_pin    = IOPORT_CREATE_PIN( IOPORT_GPIOA , 22 ),
    .scl_mux    = IOPORT_MODE_MUX_E
};

Routine

/**
 * \brief Initialize I2C Master bus.
 *
 * \param[in]   settings    Bus settings.
 *
 * \retval      0           Success.
 * \retval      1           Failed.
 */
uint32_t i2c_master_initialize( const i2c_master_settings settings )
{
    /* Set TWIM options */
    struct twim_config opts =
    {
        .twim_clk = sysclk_get_peripheral_bus_hz( settings.i2c_port ),
        .speed = settings.speed,
        .hsmode_speed = 0,
        .data_setup_cycles = 0,
        .hsmode_data_setup_cycles = 0,
        .smbus = false,
        .clock_slew_limit = 0,
        .clock_drive_strength_low = 0,
        .data_slew_limit = 0,
        .data_drive_strength_low = 0,
        .hs_clock_slew_limit = 0,
        .hs_clock_drive_strength_high = 0,
        .hs_clock_drive_strength_low = 0,
        .hs_data_slew_limit = 0,
        .hs_data_drive_strength_low = 0,
    };
    /* GPIO pins */
    ioport_init();
    ioport_set_pin_mode( settings.sda_pin, settings.sda_mux);
    ioport_disable_pin( settings.sda_pin );
    ioport_set_pin_mode( settings.scl_pin, settings.scl_mux );
    ioport_disable_pin( settings.scl_pin );

    /* Initialize the TWIM Module */
    twim_set_callback( settings.i2c_port, 0, twim_default_callback, 1);
    if ( twim_set_config( settings.i2c_port, &opts ) == STATUS_OK )
    {
        return 0;
    }
    else
    {
        return 1;
    }
}

Here is my code:

/******************************************
* MY BUGGY FUNCTION
******************************************/
uint32_t test_read( Twim* p_port )
{
        /* Read mcp3421 */
        uint8_t data[5];//For debugging reasons I use 5. After debug 4 is sufficient. The 4th byte is configure register value.

        {
            /* Prepare packet */
            twi_package_t packet_rx;
            packet_rx.chip = (g_mcp3421_i2c_address>>1);    /* TWI chip address to communicate with */
            packet_rx.addr[0] = 0x00;                       /* TWI address/commands to issue to the other chip (node) */
            packet_rx.addr[1] = 0x00;
            packet_rx.addr[2] = 0x00;
            packet_rx.addr_length = 0;

            /* Length of the TWI data address segment (1-3 bytes) */
            packet_rx.buffer = (uint8_t*) data;             /* Where to find the data to be written */
            packet_rx.length = 5;                           /* How many bytes do we want to write */
            packet_rx.ten_bit = false;                      /* Indicate if it is 10-bit addressing */
            packet_rx.high_speed = false;                   /* Indicate if it is a high-speed transfer */

            /* Read data from TARGET */
            if ( twi_master_read( p_port, &packet_rx) != STATUS_OK )
            {
                /* Exit with i2c error */
                return 1;
            }
        }

        /* Exit with success */
        return 0;
}

And here is the logic analyser results

What am I doing wrong?


texts: TFT LCD Tear-down Silver Rectangle Question

texts:
I was tearing down a TFT LCD from a medical device (ultrasound bone healer) for fun and did not understand the function of a component. It's a silver rectangle that sits between the LCD and the ACF location for the FPC. When held up to the light it appears that all the signals flow into this device and then fan out to the rows and columns of the LCD. If I had to guess it looks like some kind of control chip. The aspect ratio of this chip seems terrible for manufacturing (long and skinny). Can someone tell me what this device might be and what it's function is? If it is an integrated circuit how do they manage something like this, it seems very easy to fracture.

Based on the markings I think it's one of these displays:
http://www.trulyamerica.com/products/tft-modules/


texts: Is it possible to make a complete analogy between electricity and something more graspable? (e.g. fluids)

texts:
A similar question has been asked here, but mine is more general.

Here is the background: it seems to me that electricity is not so intuitive as it may sound. For example, many (unskilled, as I am) people think an electric plug is like a (water) tap: it delivers what it can, and stop at a maximum flow. But it is not possible to stop the water from flowing, by putting too large a bucket under a tap, whereas if you plug a washing machine you could break the current!

Improving the understanding with analogy seems to be an efficient way to learn (not talking about scholar stuff) about electricity and "feel" it (not too intensely, though).

Water seems to be a good candidate for these analogies: current/water flow, electron/molecule, tension/height difference, resistance/decrease of the pipe section, capacitor/volume with membrane. I also heard about an analogy between electricity/water for transistor.

My question is: is it possible to define a global analogy, which would: (i) allow to better understand any electrical circuit [ideally, a complete transcription would be possible], (ii) be exhaustive (i.e. work for any electronic/electrical component). Other examples include allowing to understand what would happen if the frequency of the electricity changed, or if a power plant produced energy in excess, etc.

I insist: I'm not an electrical engineering. I'm just curious :)


texts: MOSFETs in charge circuit having different characteristics

texts:
A few of the products at work are suffering from a shortage of a particular PMOSFET (IRLML6402) and so I have been provided an alternative (DMP2305U) to use. I changed a few over on a few products to see if it would make any difference to the workings of the circuit, and all seemed fine.

I then came to one of the products that has a rechargeable NiMH battery. This works by having a microprocessor switching the MOSFET on and off to regulate current flow. A small snippet of that circuit can be seen here:

As this is a work product, I cannot show any more of it (I am aware the PFET says it is an SI2301, bit the one fitted is the IRLML, this version of the schematic wasn't updated). The source of the FET recieves power from a USB.

Now, onto the results. I powered it up using an Agilent power analyser, with the power going in to the USB, and I monitored the current drawn by the circuit. With the original FET fitted (IRMLM6402), during the charging stage, there is a nice constant (average) 260mA. When I fitted the replacement (DMP2305U), this then changed to 280mA. I tried a few times, and the result was repeatable. I then changed the FET back over, just to be certain it was the FET responsible, and when the original was fitted back, 260mA was seen again.

I have scoured through the datasheet and have no idea why this would happen. There are a lot of factors I don't understand, as I am still learning electronics, so I cannot see why this change in current consumption would happen. Does anyone know any factors that could cause this?

This does not affect the working of the circuit in any way, I am just curious as to why this happens, so I know what sort of things to look out for in future when testing replacement components.


texts: D flip flop with asynchronous reset circuit design

texts:
I've been looking at the circuit for the D flip flop with asynchronous reset and I do understand how the overall circuit works, but I can't understand what  the point of connecting the wire in the red rectangle to the reset is.
The output will get reset if reset is set to 0 regardless of this connection.
Please correct me If I'm wrong.


texts: Fundamental difference between microcontroller and PLC

texts:
I am a teaching assistant for a sophomore mechanical engineering laboratory course. One of our lab modules is focused on PLCs, and another uses Arduino micro controllers. One of my students asked why they are different and I found myself without a good answer.

They both have input and output pins, perform logical operations, and are programmed via regular computers. They can be used to control the same equipment, read the same sensors, and make the same logical decisions. The differences in programming languages and the fact that they look and feel very different seems superficial. Is there a fundamental difference between the two, or is a PLC just a micro-controller designed to work in an industrial environment? How can I explain this difference to a sophomore college student with no background in electronics?

A good answer will either answer my question or offer a useful frame challenge; I may be asking the wrong question entirely.


texts:
I would like to build a battery charger with my UC3906 IC. I found a lot of data-sheets, application note, etc. but nothing that comprehensively explain how to choose the values of the resistors. I would expect a "few lines guide" of the form "for a n cells 12V battery, choose R1, R2, etc. such and such." But I found nothing like this. Can someone help?
In my case, I have a 6 cells 12V lead acid battery (cells in series apparently, capacity not specified), but it would be nice if the answer be general and valid for any type of lead acid battery.


texts: Are these two capacitors in series or parallel?

texts: Personally I feel they should be considered to be in series, as there is only one path for the current to flow. But my textbook claims they are in parallel. I'd like to hear an explanation as to why they are in parallel and not in series.


texts:
I am having trouble figuring out what is wrong with these nets?
"Design -> Netlist -> Clear all nets" will delete only the functional ones and these unconnected ones remain.
Can anyone tell me what happened and how to fix this?
Thank you.


texts: Displays used in clocks - use with Arduino/ESP32/PIC

texts:
I'm working on a project with a micrcontroller and I need a low-power display similar to something shown above. Does anyone know what these particular displays are called and whether or not there exists ESP32/Arduino compatible versions of these?

I thought of e-paper, but refreshing every minute and those things are expensive.


texts: Small batteries for use in cold (but not freezing) environments?

texts:
I'm building a small, low-power device that will be used inside a standard consumer refrigerator (approximately 2°C).  I've had trouble with Alkaline batteries at low temperatures, and was wondering if anyone has any recommendations for cells to use under these conditions.  How do Lithium coin cells hold up, for instance?  The datasheets I've found for them don't seem to take temperature into account.

Update: it looks like I'll have to source ~50mA for short bursts, so the low-end lithium manganese dioxide cells I've been using aren't going to cut it.  Any other suggestions?


texts: I need help reducing current in my motor driver. The chip is the L293D motor driver with output max 600mA. My stepper motors draw maximum 350mA per phase and operate at 12V, so I am concerned about overcurrent. Is this ok to do, or do I need to add resistors? I looked at some other questions similar in askings, but not the answer I was looking for. The power supply is switching between 8 AA batteries and a wall wart that supplies 5A @ 12V. I am concerned because I wonder if I would need to limit the current at all, and if needed, what do I do. I am also thinking about if I use the batteries, since they are rated in Amp-Hours, the circuit could draw only the needed current. I don't know. Please Help!


texts: How to drop voltage to give a constant DC output

texts:
I have a load that drives current 1.8A[Max] @26V DC.
It has to be supplied with a DC voltage of 30V[max].
I have a DC voltage 36V coming from another Power Supply Unit.
In order to supply a constant DC voltage of 30V to the load from 36V DC supply, would it be okay if I use a zener diode and a resistor as shown in the circuit or just a resistor would be sufficient?
If yes, how to choose their values to drive this load.
If not, what would be the best way to have a constant 30V DC?
I'm more concerned about the power rating.
Thanks in advance for the suggestions.


texts:
I am currently working on ECAD. Just to add more technical values to my work, I want to learn Signal Integrity and Thermal Analysis. What are the books,links you would suggest me to learn it?

I am equipped with both Cadence SPB 16.5 and PADS 9.3. I suppose SI can be done with the tool Allegro PCB SI GXL and XL. Is it the tool SI experts use commonly or will you suggest me something else?

Couple of years from now, what would be the advancements in ECAD and how should I be prepared for it?

Really looking for some help. Thanks in advance.


texts:
General stepper motor question:

Is it safe to manually turn a stepper motor that is energized (holding at a fixed position)?  Or could it damage the motor in some way?

I'm working on an old stage based system that uses stepper motors to move the axes.  Each of the axes has a knob on the end that I can use to move the stage position manually, but when the system is energized I'm afraid it will damage something if the knob is turned.  When the system is not energized it's very easy to turn the knob, so I'm assuming it might damage the motor to turn it while holding.

Thanks in advance.


texts: How to properly use STM32 flash memory as an EEPROM?

texts:
I have to save certain parameters to the flash memory and these values should be non-volatile. But my program will change these parameters and I want the changes updated to the flash.

I understand to overwrite a flash page, you have to erase it first. And the granularity of erase operation is a page. Considering all of this, how can I properly implement it in software? Whenever a parameter changes, should I erase the entire page? The page size is 1 kB, which is much space than all of my parameters put together.

Is this the only way to go?


texts:
We lay out the RF trace for below model.

GSM 900MHz

RF trace maintain at 50Ω impedance. As I know, the RF trace needs to be as short as possible for better signal. Do we need to bend RF trace when tuning component comes in between? See attached image for a better understanding of my question.

Do I need to follow curved traces at interaction of L3 and C67?


texts: BER vs SNR measurement in a Digital communication system

texts:
To analyse the performance of any communication system, BER vs SNR graphs are used.

For a digital system like this one (Assume there is only one signal, so mux & demux are not required)

SNR is measured before demodulating and BER is measured for the digital sequence after Source decoder.

Is this the right way of plotting BER vs SNR graphs?


texts: Mixing same brand batteries with similar voltage

texts:
Just about everyone has heard of the problem with mixing new and old batteries, but is it safe to mix various old batteries with each other, regarded that they are the same model and brands, and read with a similar voltage on a multimeter?

I have a number of batteries of the same type (voltage rating, brand and size) in storage. When measuring DC voltage output by the batteries straight from the positive and negative terminals, my multimeter gives readings ranging from ~ 1.30 V to ~ 1.57 for some used batteries, and it quite consistently gives 1.606 V as the reading for fresh batteries of the same type. Would it be fair to assume that in most cases the output voltage gives a general idea of the charge left, and would it be safe to mix all batteries of the same type (as explained above), as long as the voltage output measured was similar for the batteries to mix, and how much difference is recommended before you should be encouraged to not mix the batteries (if that is the case)?


texts: Lithium Ion Battery Capacity: Discharge Analysis

texts:
I have taken apart a battery module consisting A123 Systems ANR26650-M1A cells (they are technically Lithium-Iron-Phospate (LiFeo4) cells) that were used in a commercially controlled environment. After I charge them using a variable lab bench to the specified 3.6 volts, at a low amperage, below 0.5C, I have noticed a continual drop in voltage when measuring with a multi-meter.

Initially, each cell will read the voltage it was charged to, but over about a 6 hour timeframe, the voltage readings gradually drop and stabilize. I found this peculiar, since all of the batteries were doing this, and stabilizing a various voltages.

I later ran discharge tests using a battery analyzer, and I have documented that the voltage readings stabilize at the exact percentage of the remaining capacity. For example, in this case, with a 3.3v nominal rating, it is supposed to be charged to 3.6v. After performing a discharge test, the analysis will conclude that there is 2.202Ah, out of a potential 2.3Ah, resulting in 95.8% capacity. Interestingly, 95.8% of 3.6v, is ~3.49v, which is the exact voltage that this particular cell stabilized at. I've had identical results with over 20 cells now.

Also, if I take the exact same cell, and perform an analysis, almost immediately (within minutes), I obtain identical capacity readings as to when I allow the voltage to stabilize, say 6 hours later.

In conclusion, it appears there are two inferences that can be made.

After a battery is fully charged, the voltage that it stabilizes at (at room temperature ~70F) has a direct correlation to its capacity. If I had to derive a formula, it would be: $$ \frac{\text{Stablized_Full_Charge [V]}}{ \text{Maximum_Full_Charge [V]}} = \text{Capacity(Ah) [%]}$$.
In relation to a typical LiFeo4 discharge curve, the lost capacity of the battery is only relevant to the initial discharge voltages. Unless the capacity percentage drops below the nominal tolerance range, the nominal voltage is not affected. It's as if taking an image of the discharge curve, and cropping out a portion of it, beginning from the initial point of the test.

My question in general is this; is this normal? Has anybody else documented this as well?


texts: Paralleling switch mode dc/dc converters for redundancy

texts:
I have a use case with 6 converters, 1 primary and 5 redundant. At the moment the system is configured to enable the next converter in an error daisy chain in case the supply voltage of the previous converter drops below a threshold (with a comparator). They are all connected to a 3V3 volt bus through diodes, from which voltage sensing/feedback is derived for each converter.
I would like to avoid this and simply have the converters function independently of each other to reduce complexity and interconnectivity, preferably. I don't care about load balancing in particular. A single converter is sufficient to supply the system. I am, however, concerned with the stability of the system as well as efficiency to some degree, which should not be too low. Most likely it would be preferable in that sense to only have one converter running at any given time, though not a necessity.
Any ideas or have I already got the best solution?


texts: I am driving a MOSFET with AVR using PWM for controlling a motor. I have a 4K7 pull-up resistor on the gate. My question is, do I need a resistor in between the AVR pin and the gate? (The mosfet is NX2301P)


texts:
I used name tags (these little arrow tag forms) a while ago on this schematic, now coming back I haven't got the option to switch on name tags (or at least it doesn't work) and some names are not shown, they are just shown as a D with a strike through.

Any ideas?

When I rename the net it does show the correct name however in the renaming window. But even if I change it it does not show up in the schematic.

Here is a screenshot of a old document I have of the same schematic part.

Even with the bad resolution you can clearly see that there are labels with arrows here but they vanished now.


texts: Converting variable capacitance value to variable DC voltage level

texts:
I need a simple method to convert a small variable capacitance value into considerable variable DC voltage.

Capacitance value range  = 0nF ~ 14nF
DC value range needed =  0V ~ 6V

What I've tried is shown below. However final output should be a pure DC level without any ripples for a fixed Cx. But the following circuit seems to be still have ripples or noises.

Is there any improvements to be made for this circuit to get a pure
DC output?
Are there any other methods/circuits to do this task?

Ro=100k
Oscillator frequency is about 71.78 Hz (t1=7mS, t2=6.93mS)
Cx is the variable capacitor (Range 0nF~14nF)


texts: Reducing parasitic capacitance in momentary latching circuit

texts:
I'm using this circuit (http://www.edn.com/design/power-management/4427218/Latching-power-switch-uses-momentary-pushbutton) to get latching on/off behavior from a standard momentary switch (an Omron B3S-1000P). We have the momentary switch on a separate PCB and wired to the switching circuitry on the main PCB. The whole system is a microprocessor running off of regulated 3.3V from a li-ion battery.

We've been turning the circuit on and off over and over to see if the RC constant is going to work for our debouncing needs. In doing that, we run in to a problem where we can turn it on fine, but it's really spotty in turning off.

Recently, I think I found the solution: if I monitor the voltage on the 330nF cap it will reach a threshold voltage below which it won't turn the circuit off, and above which it will work fine.

If I then place my hand on or near the PCB containing the momentary switch, the voltage at the positive terminal of the capacitor will start to drop below the threshold and then the circuit won't turn off.

It seems like there's some capacitance from my hand/body that's getting in to the circuit and causing the 330nF to discharge a little bit. It makes sense now that holding my hand on the button PCB, turning it on and off over and over would cause the circuit to work starting working poorly. Wrapping my hand in something insulating (like a plastic bag or piece of rubber) and then turning the button on/off works flawlessly.

My question is: how can I counter my body's capacitance? My first thought was to add a ground plane to the PCB with the switch, but initial tests of holding a grounded lead while pressing the button don't seem to improve anything. Adding another capacitor seems like it would mess up the RC constant of the circuit and change the debounce behavior.


texts: How do I use this part TPS3805H33QDCKREP?

texts:
I'm fairly new to electronics. Please explain briefly why/why not.

What I got from the datasheet:

I can use SENSE AND/OR VDD.
VDD threshold voltage is 3.05V

Now my questions:

Could I leave SENSE unconnected if I would only want to use VDD or should I connect VDD and SENSE to the same wire?
Would I have to use a voltage divider as in the diagram or could I just connect the power supply and it would it activate at 3.05V threshold?

Link to datasheet: TPS3805H33QDCKREP


texts: Send a single pulse low/high pulse then stay high

texts:
I have a small OLED display that I'd like to drive with an ATtiny85 micro controller. The OLED is the 4 wire SPI type, with no CS. It has a Reset pin that is required to be pulsed low-high at power on and then kept high for normal operation.

This seems like a waste of a pin - I want to be able to do other things with the MC.

simulate this circuit – Schematic created using CircuitLab

Is there a way I can generate the required pulse without using a MC pin?

Power On sequence, as stated in the data sheet:

with RES# being the one I want to avoid using a pin for.

Thanks


texts: Why can't the equivalent capacitance be calculated like the method 2?

texts:
Question

Three capacitor with \$C=100\mu F\$ and \$50V\$ are series connected,and connected with the \$10V\$ voltage source,what is the equivalent capacitance of this circuit?

Method 1

\$C_{eq}=100\mu//100\mu//100\mu=\frac{100\mu}{3}=33.3\mu F\$

Method 2

The question circuit is as below

simulate this circuit – Schematic created using CircuitLab

\$C_{eq}=\frac{Q_t}{V}\$,and \$Q_t=\sum\limits^3_{i=1}C_iV_i\$,

\$V_1:V_2:V_3=\frac{1}{C_1}:\frac{1}{C_2}:\frac{1}{C_2}=1:1:1,so V_1=V_2=V_3=3.33V\$

So \$Q_t=\sum\limits^3_{i=1}C_iV_i=3\times 100\mu \times 3.33=1000\mu=1m\$,

so \$C_{eq}=\frac{Q_t}{V}=\frac{1m}{10V}=0.1mF\$

However,obviously we can know the answer from the method 2 is wrong,but i don't know which step is the main reason that let me calculate to the wrong answer,where am i wrong in the method 2??Can anyone tell me??


texts:
I am trying to build a transimpedance amplifier (shown below) using the LT1077 Op Amp IC to amplifier a signal from the BPW34B photodiode by OSRAM. My feedback resistor is a value of 2.2k. From what I know from Transimpedance amps, the op-amp output voltage is the product of the constant current source and feedback resistor b.c. the current flowing into the op-amp terminal near zero. Also, the voltage at the two op amp terminals should be the same. However, I am getting 2.4 V at the negative terminal instead of the expected virtual ground. I thought maybe this has to do with the Op amp characteristics and the inability to pull current through the output but I have no way to prove this.
What could be causing such a big voltage difference in the two terminals of the op amp


texts: what resistor i should use for programming pickit3?

texts: I'm trying to program a 16f877a pic with the pickit3 and I'm be able to find what resistor i should use for MCLR to Vdd Pull-Up because it doesn't say clearly and i don't either what compiler either 8x,16x, or 32x please tell me this please because in my tutorial that I'm following doesn't say anything about this


texts: Can someone help me identify what the value of this capacitor is?

texts:
I have an older computer and as I was pulling the graphics card my fingers slipped and I pulled this off the board... Problem is I can't find one with the same markings so I need to find a replacement... Any help that won't involve me spending a horrible amount of money on a new board (as everything else is still good) would be amazing.

Markings are:
361
100
2 5z (there is a space here between the 2 and the five)
Thanks


texts: Question regarding inductor peak voltage

texts:
I am trying to modulate an LED to simultaneously power a circuit and communicate with a small solar cell, but I have a question regarding a specific part of the circuit. I have simpified the problem to contain only the part that confuses me, so it is not directly related to my application, but I hope the question is still valid.
In the set-up, I have a solar cell (SM111K10L) illuminated by a modulated LED. The driver controlling the LED is sending a sequence of (10101010....) with frequency from 200 Hz to 2kHz with 100Hz steps, and 2kHz to 30kHz with 1 kHz steps for every fixed x second.

And then on the receiver side, I run an FFT of the received signal and look at the signal strength (voltage measured across the resistor).

At this point I would say the result matches what I would expect, as the modulation freuquency increases, I cannot reach the full contrast of the LED (because of the LED/driver I use is not optimized for that), so I see a graduate declination of the signal (voltage) intensity.
Now in my circuit I need to use inductor for some filtering, as my signal frequency is low, I use a very large inductor (100 mH, B82144A2107J000), but there is something puzzling happening with the peak voltage. In order to be able to demontraste the behaviour better, I simplified it to the following

Everything else is kept the same as the first figure, and only an inductor is added. When I measure the voltages across both the inductor and the resistor and repeat the steps above, I get

and across the resistor only

I don't understand why the signal magnitude at around 20 kHz looks like it has been amplified? If I replace the solar cell with a wave generator directly connecting to the inductor and the resistor, I don't observe this behaviour, so it seems to indicate that it's something related to the characteristics of the solar cell. The peak voltage with the inductor is even higher than the measured open circuit voltage at the terminals of the solar cell with no circuit attached. Any pointer would be greatly appreciated, thanks!


texts:
I am porting the USB driver from the STM32F4 device to STM32L4 device. It almost works. During the enumeration it sends and receives the information, but the data is not exactly the same as from the "plain" STM Cube generated project. II have the same settings in both project but get the strange results.

I lost a week trying to find the solution, maybe someone here had a similar problem and can help me out. Sorry for the images but there is no other of posting some informations on the SO

As you can see the packets are almost the same, but not identical. After 25th transmition the board stalls and accepts only very limited number of the requests

The both files form the wireshark (in the wireshark and text formats) are here:

https://gitlab.com/diymat/usb-problem/tree/master

The ep* files are form my port, stmcdc* - STM Cube generated one. Both were running using the same hardware.


texts:
I'm quite new to EE. I'm trying to design a wrist-based Pulse Oximeter. I have looked through a lot of literature and short listed these:

PhD thesis using 6 LEDs
A Single-Chip Pulsoximeter Design Using the MSP430
Pulse Oximeter (PO or SpO2) Analog Front End Module for the C5505 PO or SpO2 Medical Development Kit
Pulse Oximeter Implementation on the TMS320C5515 DSP
Medical Development Kit (MDK)

But I'm unable to decide which one to try out. Some of the requirements I have are:

Fairly cheap components
Miniaturized circuit must be able to fit within a watch
Reliable results produced

It would be great if someone who has experience in this field could help me weight he pros and cons of the 4 options.


texts: Measure AC magnetic field strength between 100kHz and 300 kHz

texts:
I have tried to find in the webpage some answers about measuring AC magnetic field strength in the range above 50 kHz and more with no luck. Sorry, but if someone could help me will be great.

I need to measure intensity or strength of the magnetic field  (1 to 50 mT) between 50khz to 300khz aprox. I have some like "induction heater", with different LC ! L= workcoil., Radius = 2 cm copper tube.

I have used a sensing coil in the middle and i have a strong signal, but iI don't know how to calculate the mT i have. The small sensing coil is 10 turn of awg32 cooper wire with radius = 2,5mm. The voltage is about 0.5 volt, and I can see the out put in the osciloscope(sine wave), I cannot measure the currrent of the sensing coil, and at this frequency my ammeter does not work.


texts: Which generates more heat in a brushless motor winding's: 36V @100% duty cycle or 48V @75% and how significant is it?

texts: Are the heat losses (in the windings) equivalent for a 36V brushless motor driven by 36V at 100% duty cycle compared to 48V at 75%? While my limited knowledge suggests since the same total power is delivered in either case it should be a white wash (assuming a high enough switching frequency) - my intuition is that the constantly fluctuating voltage of the switching option would create additional heat.


texts: What kind of battery can I use to power a 3v DC gearbox, which can provide power for a longer duration? I have used AA batteries but they get depleted very fast. This is for a mechanical walking robot which uses a Tamiya gearbox.Thanks.


texts: Purpose of T flip-flop in this circuit (LED)

texts:
In this circuit I try to toggle a LED on and off when a switch is pressed.

Given the nature of the T flip-flop, when the switch is triggered, it toggles the clock and since T=1 always, it essentially reverses the state of Q, so in other words, it toggles the LED on and off.

OK, the LED has its connection to the power supply, that means it has to connect to GND in order to toggle ON.

Now what does this mean?
When the TFF output is 1, the LED will turn ON? Or OFF?
When TFF output is 0, the LED is OFF? Or maybe a 0 potential is like Ground, that means when TFF Q=0, the LED is ON?


texts:
I just wonder if there is a way to share my 5v pin between two or more components?

I am practicing my Arduino skills and I have a button which when pushed I want to activate my ultrasonic sensor - then I realized each one requires the 5v pin of which I have exactly one.


texts: Digital signal interfering with analog signal and creating false triggers

texts:
I am in need of some help/advice.

To start the problem.

I am trying to install a sound player on a model train table.  I currently have 8 sound triggers, the switches on four are within 12 inches and seem to have no problem. On the other four, the switches are about 8 feet away. The player uses 5Vdc (analog I presume) for power, when the buttons are pushed the sound plays.

There is also a 16Vdc digital signal power bus that runs around the table as well. On the side paralleling it is about 2.5 inches away (from the switch leads) Also there is a control cable for the digital system using a flat cable rj85 plug cord which runs parallel for 4 feet about one inch away.

The problem I am having is that when both systems are on the 4 sounds all trigger constantly for (approx) half a second on, half second off.

Turning the power off to the DCC (digital) stops the problem. If the DCC is powered but the signal and BOTH the poss AND Neg bus wires are disconnected, No triggering occurs. Connect any one of the three and it starts again.

I do not want to move the switches as they are mounted in the control panel, Removing the DCC is not possible as it is the operating control for the trains.

I do have the possibility to reroute the digital wires in toward the middle of the table and then around to the end. There would be a perpendicular crossing with both cable/bus still. Or, I could try to move the trigger wires in toward the middle.

Would this (hopefully) solve my problem or is there another way to solve this problem? (hopefully with no wires being moved?)


texts: Using 2 different LDO with the same voltage in the same application

texts:
I'm using a Raspberry Pi and have designed an extension board (Like the Pi-face) but I have a question about the power supply. I need 3V3 on my board, but the 3V3 from the Raspberry is not strong enough for my application. So I've used the 5V supply from the USB and I have the 3V3 from a LDO. My question is:

Can I supply an IC on my board with my 3V3 (from the LDO) and connect the IO pins from this IC to the Raspberry Pi GPIO port? Also can I use 2 different power supplies? The Raspberry Pi is supplied by its own LDO and my board has its own LDO and I would like to connect IO. Here is the block diagram:


texts: How to drive a BC547 using a 0-5V sensor output?

texts:
I have an i-Snail-VC-50 sensor with an output of 0-5V. I'd like to connect this output to the base of a BC547 transistor, which powers an LED with an external 5V power source. What I want to achieve, is that the LED lights up as soon as the sensor output voltage rises above 0V (most of the time, the output will be either 0V or within the 0-1V range).

How could I achieve this, making sure that no components get damaged if the sensors output is at its maximum (6.5V)?

I know transistors are current driven, so perhaps a voltage driven mosfet (I have some IRFZ48N's at my disposal) would be better suited for this task?


texts: Do hall effect-based current sensors (clamps) always use a semiconductor as the material through which we apply the initial voltage difference and why?


texts:
Can anyone explain to me how this circuit works?
I am familiar with the traditional Zener diode as voltage regulator (with a resistor,) but I couldn't tell what the fuse does here and why the 10K resistor is in parallel not in series.


texts:
I was thinking to make a simple oscilloscope which can measure at least 2MHz signals, that would be enough, and it will be connected to a PC, or Android device.
First, I tought to use USB to connect the "oscilloscope" to the PC or Android USB Host capable device that would give me about 12Mbps transfer speed but I would like to do it whit bluetooth or on another RF way.
I say some Bluetooth-UART modules and they are capable of 2Mbps transfer speed and Wi-Fi modules only about 300Kbps. I have a 512K RAM memory for buffering the samples from my 12MSPS ADC, so at 2Mbps it will take:

$$\frac{512000\ Kbytes}{2000000\ Mbps/8bits} = 2.048 seconds$$

So I will lose 2 seconds of samples until I send all the 512K buffer over bluetooth. Over USB it is about 330mS and it is too much I think.
Is there any way to avoid this ? How does USB oscilloscope do it ?


texts:
I am trying to use below circuit for convert 24VDC high speed pulse to 5VDC pulse that can interface to a stepper driver IC.
I have used 6N136 opto-coupler and according to its datasheet it can handle 1Mbit/s.
PLC_Y000 terminal connected to a 24V square wave out (open collector out of a PLC) and the frequency can change. STEP_OUT for get 5V square wave out.

I was unable to get proper square wave out at high frequency input. I have observed waveform using a oscilloscope and results as below. (for 60kHz and 10kHz input/green is input at PLC_Y000 yellow is output at STEP_OUT)
While increasing the input frequency the rise time also increased. Couldn't reach 1MHz as datasheet.
What are the reason for this? How can I get proper square wave out without distortion?


texts:
I'm using an LED that is rated at (0.06W) current is 20mA and voltage is at 3V. I did some wrong calculations, and the resistors I'm using are not enough to limit the current to the diodes.

simulate this circuit – Schematic created using CircuitLab

The current is 0.024A now, can the LED work without blowing up?
I'm maxing it with higher power would it manage?


texts: AC Light Bulb Fade Circuit - Resistors Getting Hot!

texts:
I'm building a circuit to slowly fade in (when switched on) and slowly fade out (when turned off) two LED bulbs.

The circuit works, but the two 100 Ohm resistors (see picture) are getting very hot (too hot to touch, but not smoking)

I've had a bit of trouble going about his circuit. I'm rubbish with AC analysis, and not that great with DC. I know the hazards I'm presenting, so besides that, I was hoping someone could point me towards a solution.

I would use the proper sized caps, instead of the series/parallel config, but these were laying around. Also, 100 Ohm 10W resistors were the best I could find at the local Radio Shack.

Basically, I approached this as a DC circuit, since everything past the half-bridge rectifier diode is DC with the smoothing capacitors. Each capacitor is rated at 63V. I'm well within each capacitors voltage handling. I started by assuming (wrongly perhaps) that the bulbs in parallel would be equivalent to around  1029 Ohms, given these are off the shelf, household bulbs rated at 7W, using Ohm's Law at 120V DC. Then calculated the voltage drop for the two 100 Ohm resistors, which should be around 19.5V with a total power dissipation of 1.9W with .1A through the circuit. The fact that the two 10W resistors are so hot, leads me to believe I'm missing something here. I figured they would exceed their power handling during the initial charge of the caps, but would cool off once the caps were charged. What am I missing?

Also, I should add: Once voltage reaches ~40V across the caps, the bulbs start dim and get brighter until voltage level is ~90V across the caps. It takes about 10 seconds to fully charge. My question, is what should the power dissipation be across the two 100 Ohm resistors before the diode?

The bulbs are represented with resistors here. I didn't see a basic LED on Partsim....

Any help would be much appreciated. Thanks!


texts: Need help with a circuit diagram where the motor does not seem to have any connection to ground. Error with diagram? Or am i missing something?

texts:
I'm following a really simple electronics instructable found in this link: https://www.instructables.com/id/Vibrating-Timekeeper/.

I've been studying the circuit provided but can't figure out why the circuit is the way it is.

Here's the circuit:

Just a brief explanation of what the circuit does. Every few seconds the ATTiny85 a signal out of PWM0 so that it can make the motor (Denoted by M) run. I understand most of the circuit except the one on the upper right. I understand how transistors work, why a diode is added there. But the right side of the motor does not seem to have any connection with ground because it just loops through the transistor through the diode and back again. Shouldn't there be a connection to ground somewhere in this general area?

I tried mocking this upper right part of the circuit and it no current flows if I follow the circuit (As shown below):

But if I tried to connect a line to the ground then current flows, just that the area with the diode is not used:

I understand my mock up is not exactly like the diagram (Not sure how to add an ATTiny to CircuitJs simulator), but i think I have the gist of it. I just need help figuring out if I'm missing something or if there is an error in the circuit.

Any help would be great. Thanks!


texts: Implement MicroController Power Switch and re-use the button for other features

texts:
This is similar to other questions, but I feel it is different because of the reuse of the "power" button.

I want a "latching" Momentary Power button.

Behavior:

User Pushes momentary button, holds down as long as necessary and the device powers up.
Between Power On and Off the same button will be re-used for other functions
When it is held down for 5 +/- seconds the MicroController will turn itself off.

Design Constraints:

Battery provides between 3.7V to 2.9V during it's usable life
The Voltage regulator requires Vin +/- 0.3V on the Enable Pin, 3.1V output.
MicroController operates at 3.1V
MicroController Output Pin High state is 2.7V Max

Debouncing: In this case I'm not concerned about debouncing the switch, if the user doesn't hold it down long enough for the MicroController to set it's Digital Output pin  High the device doesn't power on.

I've worked up the following schematic, which kind of works.

Falstad Circuit Simulator of my schematic

It assumes 3.7V from the battery.
Uses an Analog Input for the Power button, which then uses the variation in voltage to determine if the button has been pressed. In the current design the difference is 0.12 V (from 3.4 to 3.52), but the MicroController has a 12 bit ADC so that shouldn't be a problem, in addition I can adjust the sensitivity range of the ADC.

Questions:

What is the difference between reality and the simulator?

Is there a better way?

How can I get a greater voltage difference on the button input? I've tried many different combinations but they increase the voltage range above the 3.6V Input High Maximum specified in the datasheet.

I'm not excited about the "Leakage current" when the uC Controlled Power Pin is Low, any suggestions?

Thank you for any ideas/suggestions/answers.


texts:
Can I use 3V (2*AA or 2*C batteries in series) as power for  10/20 leds connected in parallel?

LED specs:
Diameter: 3mm / 0.1"
Emitting color: Red/Green/Blue/White/Yellow
Material: GaP
Forward voltage: 1.8-3.4V
Forward current: 20mA
Backward voltage: 5V
Wavelength: 460-630nm
Frequency characteristic: Low frequency

I will connect only 1 collor lets say 20 red or 20 green leds... need them to work at 70-100% of intensity... the batteries model and number is not a limit I am just searching now...and yes I can make a  connection of 3*C batteries in series


texts: Two Mifare cards: could one be readable and the other not?

texts:
I have an RFID keyfob which is used to access my building. The access is not otherwise authenticated (everybody just touches the door with the keyfob and enters) so I was wondering whether I could use generic RFID cards to enter.

The assumption is that each keyfob has one common code which is presented to the reader. (that code would be written to the keyfob when adding it).

There can be other solutions (the ID of the keyfob is added to the building system upon the addition of a keyfob) in which case my approach will not work but it is worth a try taken into account the prehistoric computerization of the set of buildings.

Based on Miguel Balboa's RFID library and a RFID-RC522 reader I wanted to read the data on the card.

All the generic cards I tried dump information such as

Card UID: 94 5D 85 1E
Card SAK: 08
PICC type: MIFARE 1KB
Sector Block   0  1  2  3   4  5  6  7   8  9 10 11  12 13 14 15  AccessBits
  15     63   00 00 00 00  00 00 FF 07  80 69 FF FF  FF FF FF FF  [ 0 0 1 ]
         62   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00  [ 0 0 0 ]
         61   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00  [ 0 0 0 ]
         60   00 00 00 00  00 00 00 00  00 00 00 00  00 00 00 00  [ 0 0 0 ]
  14     59  PCD_Authenticate() failed: Error in communication.
  13     55  PCD_Authenticate() failed: Timeout in communication.
  12     51  PCD_Authenticate() failed: Timeout in communication.
  11     47  PCD_Authenticate() failed: Timeout in communication.
  10     43  PCD_Authenticate() failed: Timeout in communication.

I do not know how to make sense of the data yet but at least it is there.

When trying my building entrance keyfob, I get

Card UID: 25 C7 EB 48
Card SAK: 88
PICC type: MIFARE 1KB
Sector Block   0  1  2  3   4  5  6  7   8  9 10 11  12 13 14 15  AccessBits
  15     63  PCD_Authenticate() failed: Timeout in communication.
  14     59  PCD_Authenticate() failed: Timeout in communication.
  13     55  PCD_Authenticate() failed: Timeout in communication.
  12     51  PCD_Authenticate() failed: Timeout in communication.

So the card is read, its UID and other information are recognized but there us no further data read. This is the same case with another keyfob.

One thing is clear: both the building keyfobs and my generic ones are Mifare ones.

My question: does this failure to read the keyfob contents (beside the metadata ones) mean that noting is encoded? Or that for some reasons the way this Mifare card needs to be accessed is different?

If this the former, I am done - the access is based on the ID of the card and there is nothing I can do (as the ID of the card cannot be changed (?)). (there are cards with changeable UIDs, I happen to have found and tried one but the access was refused - see edit and Lior Bilia's answer)

EDIT: Lior Bilia's answer gave a third possibility: the fact that the access to the data is behind a challenge and therefore not available (and then used to authenticate the card).


texts: How do I size an isolation transformer I'm using to emulate a variable reluctance sensor?

texts:
I'm attempting to emulate a variable reluctance sensor on an engine. I know I need to produce a 600hz-6000hz zero-crossing +/-12volt waveform. The engine management controller's input measures 20okhm.

My first attempt used a Bourns SM-LP-5001 1:1 audio transformer for isolation. My LM2904 went into current limiting mode when I fed it any waveform on CKP1/CKP2. My assumption is that I mismatched something causing the current to exceed the LM2904's capacity. VIN is nominal automotive 12VDC, I am using 13.9VDC for my bench supply.

Here's what I'm thinking for my next attempt, but I need some understanding how to specify what transformer I need.

I found a Xicon 42TM018-RC audio transformer that has 1:1 10k CT winding and 550 ohms DCR on it's primary.

Since the ECM measured 20kohm at it's inputs with my DMM, does my transformer need to match 20kohm primary impedance?
Or will this circuit fail for a different reason?
Is there another approach that would work better?


texts:
In a school project we will try to implement a control system for a boost power factor correction (PFC) converter. The converter circuit can be seen below (http://www.ti.com/lit/an/slyt517/slyt517.pdf).

The control system works as follows: An outer loop controls the output DC voltage of the boost, and an inner loop controls the current into the converter such that it has the same shape as the input voltage Vs.

Our problem right now is that we don't really know how to create a transfer function for the boost converter. And we need a transfer function in order to tune our PI and PID regulators.

Does anybody know of a simple way to get a transfer function for an interleaved boost? All of the papers that we have read have very advanced derivations that are hard to follow, and the end result is usually very complex and difficult to use. Any guidance would be appreciated.


texts: What's the benefit of Upcounting or Downcounting or Center-aligned mode of timer/counter?

texts:
I have done several project (3-4 project) via Timers/Counters but I'm curious to know Why do they have three mode for counting?

Also I know that in Upcounting mode it count from zero to 0xff... or in Downcounting mode it count from 0xff... to zero and so on for center-aligned as you can see.

What was your experience to use these three mode?

What is the advantage and disadvantage of each mode?


texts: Running an electric boiler from grid-connected PV solar panels

texts:
I am planning to replace my (broken) gas boiler with a 10 kW electric boiler to supply the central heating radiators. I am also planning to replace the existing gas hob with an induction hob (say 4 kW). Hot water for shower and taps is currently supplied from a 3 kW unvented electric cylinder.
Once the electric boiler is installed, I then plan to install grid-connected solar PV panels on my roof.  But I have been told by one boiler supplier that theirs is incompatible with solar power, by another that they are unsure and I should consult with the PV installer.
None of this makes sense to me.  I had understood that the grid seamlessly takes over from the PV inverter when needed.  So the boiler does not experience interference?
Any comments would be most welcome.
UPDATE
Many thanks for all your reassuring comments.  It may be that there was some concern regarding harmonic or other interference from the output of the inverter. I will find out from the PV supplier.


texts: Is it possible to create a 22 stage synchronous counter using multiple 4-bit synchronous counter?

texts: Is it possible to create a 22 stage synchronous counter by linking together multiple 4-bit synchronous counter, like SN74F163AN?


texts: What is the receiver component in Snap Circuits part U24 (Infrared Receiver)?

texts:
I'm trying to find a datasheet for the receiver component in Snap Circuits part U24, which is an infrared light detector/receiver. It looks exactly like a TSOP382 sensor (picture below) but doesn't seem to work like one.

Here's my understanding of how the component works:

Similar to an NPN transistor
Connect pin 1 to Vcc (5V)
Connect pin 2 to GND (0V) (similar to Emitter)
Connect load to pin 3 (LED in my case) (similar to Collector)
When infrared light is detected, pin 3 and pin 2 are connected, like in an NPN transistor

Again, I'm specifically looking for the datasheet or the exact name of the component.


texts: Arduino Uno reading a logic 0 signal as 1

texts:
I have a program on my Arduino Uno that needs to execute quickly, so I'm trying to carry it out by dealing directly with registers. I made a few recent changes to my code, which was originally working fine (unfortunately a change in some of the hardware that's going into this project means I can't revert to the earlier version).

Since the changes, the Uno has developed an issue that I've isolated to one specific problem: I am using an external device to write 0V to the Uno's pin D4 (pinout diagram linked at the bottom of this post), but Serial.print() tells me that pin is getting a 1. I've confirmed the voltage with a multimeter, so either the Arduino is broken or I'm missing something.

const uint8_t pinO = 4; // Register D
void setup() {
     DDRD &= ~(1<<pinO); // sets pin as input
     PORTD &= ~(1<<pinO); // I wasn't sure I needed this line. Is this what I'm doing wrong?
     Serial.begin(9600);
 }

 void loop() {
      Serial.print((PIND >> daqpinO) && 1);
 }

There's more to the code, but this is everything that should be relevant to the issue. What I see is that writing 3.3V to a different pin on register D seems to be what's causes this pin to start reading high. That shouldn't be happening though, right? All the GPIO pins should be toggled independently?

https://www.google.com/search?q=arduino+uno+pinout&client=firefox-b-1-d&tbm=isch&source=iu&ictx=1&fir=fbbDkYhiQfV2sM%252CFkhuyc9ufXPLnM%252C_&vet=1&usg=AI4_-kR696oFGr1iYjvDWQkqpvcdtaQOGg&sa=X&ved=2ahUKEwi13dL9oNHhAhWtIjQIHftuCXkQ_h0wFnoECAsQBA&biw=1536&bih=750#imgrc=fbbDkYhiQfV2sM:&vet=1


texts: Need Basic component/circuit that if given the input volatage [-2,-1,0,1,2] will output, [-1,0,0,0,1]

texts:
as a hobby I'm working on a ternary computer, using very basic building block.
in order to implement an half adder, I need a very basic component/circuit, that take the following input voltage, [-2,-1,0,1,2] and outputs this voltage [-1,0,0,0,1]. I don't want something that return -0.5 volts if given -1v, it has to be close to 0v.

does anyone know of any basic component that does this?

Input | output
==============
-2    |  -1
-1    |   0
0     |   0
1     |   0
2     |   1


texts: Can a Tesla coil's secondary wiring overlap?

texts:
I am building a small tesla coil just as a proof-of-concept using a bug-zapper circuit. I unwound some enamel copper wire off a transformer and put it on my 12 cm length x 2 cm diameter PVC pipe and realized that after winding the first time, I still have lots of wire left over, so I just wound a second and third layer of secondary wire over the first layer.

Is this okay to do? Every other Tesla coil I've seen doesn't do this, but why not? As I understand it, a Tesla coil is just a transformer and it shouldn't matter wether the coils overlap, and only the number of coils should matter, right?


texts: Through-hole footprints: pad size from technical drawings

texts:
I'm creating some footprints for through-hole components in KiCad, and I've got some issues determining the correct pad dimensions from manufacturer's technical drawings.

As an example, here's the drawing for a Fairchild BC547 - TO-92 package (line spacing lead form - dimensions in millimetres):

First of all, having two values for the same dimension should in my understanding indicate min/max values.

I don't want the drills to be too large, as I like when the component somehow stick to the board when soldering from the bottom side.

So in such a case, what would the ideal drill size and pad size for 0.56/0.36 and spacing for 2.80/2.40?


texts:
Could anyone explains to me how to interpret the table of IEC 61000-3-2 standard given in wikipedia through the following link:
https://en.wikipedia.org/wiki/IEC_61000-3-2
For example:

Harmonic order
Limits class A (A)

2
1.08

3
2.30

4
0.43

What is the relationship of the class limit to the Harmonic order? What is the link between 2 as a harmonic order and 1.08 as a class A limits?


texts:
simulate this circuit – Schematic created using CircuitLab

I'm attempting to make a circuit that flashes each LED sequentially. So far my 555 timer works just fine and gives me a pulse about 3x/second for the clock on the CD4017. However the LED's flash in random orders.

For the split second that the timer supplies voltage to the 4017, a random LED is lit up. For the split second that it stops supplying voltage all the LEDs dimly flash on.

Note that for the sake of simplicity, I only included 5 LED's in the schematic. There's ten LEDs for the 10 outputs of the CD4017.

Any idea what's going wrong here? I'm a first year student of E.E. so I'm still learning a lot. Thanks!

EDIT: This is essentially what I'm trying to create:


texts: Problem with arduino controlled constant current supply with MOSFET/NPN

texts:
I am building a lamp using 5 1-Watt LEDs, an 18V DC power supply and an Arduino for dimming/controlling it. Im using a simple design (below) for the constant current driver (as was used here for example). The MOSFET I have is not logic level (it's a FQP50N06) but it opens enough at 5V to pass the 350mA that feed the series of 5 LEDs.

This circuit works fine when the Arduino is On; my problem is when the MC is turned Off, and the PWM pin is (I guess) floating, the LEDs are still powered (though slightly dimmer). I am looking for a way to modify this circuit so that M1 shuts down when the MC is Off. (Assuming that the power supply V1 is still On.)

Any idea? thanks!

simulate this circuit – Schematic created using CircuitLab


texts: Why is graph of speed against current linear in DC shunt motor, but hyperbolic in series motor

texts: I noticed that for the speed control of DC motors, the graph of speed against current for shunt motor is always linear, while that of series motor is always hyperbolic. Why is this so? Does this apply for every speed control methods?


texts:
Let say its connected Y1-Y2-delta

how to find the equivalent load value for Y1

one of the slide said

Zy = (1/3) Zdelta ??? so im confused how to find for first picture .


texts: supercapacitor regenerative braking question

texts:
I am doing a heavy vehicle project and putting a regenerative braking system into the vehicle. It also has a supercapacitor module in parallel with the battery (which has the same voltage), and the goal is to

Share the current during acceleration (s1 and s2 closed)
Charge the supercapacitor (only) during braking (s1 open and s2 closed)

Because I am a student and have limited money, I don't want to blow up anything. Will this circuit have a voltage spike? Also, does this circuit need a dc-dc converter? (emf of the motor will be close to 12 volts during braking)

Materials

Battery: 12 V 10 ah

Supercapacitor: 15 V (only using up to 12 V) 55 Farad

Switch: 30 V 10 A relay with diodes

Motor: 775 DC Motor

H bridge: DROK L298 Dual H Bridge

I want to feed the supercapacitor constant 12 volts from the motor, but I don't know if I can build a bidirectional DC-DC motor. Is there any alternative solution?


texts: How do I calculate if two power adapters will output the same energy if they have different voltages?

texts:
I often face this question. A friend gives me a lot of used modems and routers, but they usually don't come with a power adapter.

Currently, I'm trying to use a router that is specified to work with a 12VDC/0.5A, but the only power supply I have that fits it is 5VDC/0.85A.
And of course I could look for an appropriate adapter, but since I got a lot of 5V adapters, I'd like to try.

Thanks


texts: What is the effect of capacitors at OpAmp input -frequency response?

texts:
I want to filter noise at opamp inputs. For this purpose I am planning to place \$C_p\$ and \$C_n\$ capacitors near opamp input pins as you see in the image.

What happens if
1. \$V_{IN}\$ is fixed DC voltage? Does the basic inverting and non-inverting amplifier formulas differ?
2. \$V_{IN}\$ is sinusiodal? What is the formula of \$V_{OUT}\$ in terms of resistor and capacitor values in both circuits?


texts:
I am currently designing a MOSFET common source amplifier for my electronics lab class. My issues is that currently I am unable to obtain a gain out of my current circuit design.
I am using a 2N7002 MOSFET in my simulated design
My input signal is 1v/100hz with a 12v power supply.
What could be the issue here?
My current desgin

Red is my input signal
Green is my output


texts: Was my circuit victim of capacitor self-resonance?

texts:
In order to generate a short pulse off a permanent constant current signal, I made this circuit.
It works well except that it created a very high frequency ripple which wreaked havoc all over the prototype board, not just the output, and brought the voltage of the entire board from 5V to 3V, sometimes less.

The frequency was so high that my 200Mhz oscilloscope couldn't see the wave but I could see that the line was very thick.

I solved the problem by adding a 15pF cap (C2) between the output and ground. Now the signal is perfect.
Before, when my circuit had problems, it was the same, just without this cap. There was already a 330K resistor to ground and I thought that would be enough to avoid this type of interference.

I think that the voltage drop was due to other ICs being pulsed extremely fast albeit at undefined levels.
Before finding out where the problem came from, the symptoms were not clear: The board worked as expected. Then the next day I changed something apparently not related and it started working unpredictably.

Is this phenomenon common? Should I be concerned about other flaws in my circuits which could be the cause of this? Or was it what is called "capacitor self-resonance"?

simulate this circuit – Schematic created using CircuitLab

The triangle on the left is a Schmidtt trigger. I can't confirm if the same effect would appear if the signal source came from another ic or a power supply directly.

The board is a composition of three 595 shift registers, schmidtt triggers, a 557 clock, 2 or 3 mosfets and a bunch of schottky diodes. It's powered by a linear regulator, itself powered by a 15V power supply. Changing the power supply to a completely different one didn't change anything. All the ICs have decoupling caps, which I think have also no effect as far as this board is concerned. Adding them didn't produce anything visible.


texts:
I am tasked with a situation where I have to analyse different ADC for a medical instrument (abstracted on purpose just to emphasize that the input is sensitive and results can endanger someone's life if incorrect).

I am to analyze the reliability and simplicity of different ADC in order to suggest the best one for the situation. I was a bit confused on the parameter of dynamic range and how that affects these two design goals. Is having a wide dynamic range preferred to provide reliable results from an ADC? Does it add much in the way of circuitry to the ADC's design?

Are there other components of an ADC that can be analysed for reliability? For example the resolution can be looked upon as the higher the resolution the more reliable the output (i.e. closer to the analog input).


texts: Solutions for holding oscilloscope probes (and freeing up hands)

texts:
I have a problem, I only have two hands and the newer oscilloscopes come with four probes. This leaves me with zero hands to press the trigger button (even if I hold three probes with one hand I still can't use four). I usually have to ask a colleague to press the trigger button, in a cubicle this can get awkward.

What is a specific way I can hold the probes and press the trigger button,
Without biological modification?


texts:
So I saw a post talking about the commercial feasibility of an Arduino (http://electronics.stackexchange.com/questions/11333/commercial-use-of-arduino-is-it-suitable) . From this it said a great idea would be writing your own AVR Program i believe.

What does it mean to:

1) Write an AVR Program? What is an AVR Program?
2) Program your own microcontroller?

Is it possible to make your own microcontroller and how would you do this? Would you still use something such as an ATMEGA? What would this change and how would you "upload" an AVR to this?

Edit (after Comment #1): My questions is would i still use the Arduino or would it be better for me to buy ... a different? microcontroller and program that? To refine my other question, how would you program ... a microcontroller? what interface would be used to upload code?


texts: Raspberry Pi Connected to CH340 on STM32F103. Broken Pi and USB interface

texts:
I have a 3D printer that's running based on a STM32 chip. Included on the mainboard is a CH340 serial to USB converter.
I connected this board with to my Raspberry pi 3 which I powered using the 24v PSU from the printer and steped it down to 5v using a cheap buck converter.(you might know where this is heading)
The buck converter is rated for 3A so it ran very hot when powering the Raspberry pi and I realized it when the hot glue I applied on the back of it started to drip. I immediately cut the power but It did quite some damage. So my first question is, what happens when a buck converter gets overheated, will it output a higher voltage?
My Pi still runs but the LAN9514 Ethernet and USB hub chip runs extremely hot instantly, so I plan on de-soldering it and see how it goes, but as of now, the system seems to boot alright.
The STM32 board also still runs but the data lines of the USB from the CH340 are broken. I am sure that it's only the data lines because I used masking take to cover the 5v and GND connections on the USB cable, it was to prevent the GND from the USB powering the 3d printer since they were running off of the same PSU.
I am not sure what happened and I was wondering if replacing the CH304 and LAN9514 chips alone could revive these two boards?
Thanks in advance.


texts: How are positive and negative feedback of opamps so different? How to analyse a circuit where both are present?

texts:
In an opamp, feedback on the positive input places it in saturation mode and the output is of the same sign as V+ - V-; feedback on the negative input places it in "regulator mode" and ideally Vout is such that V+ = V-.

How does the opamp change its behaviour depending on the feedback? Is it part of a more general "behavioral law"? [Edit: Isn't it something in the lines of the voltage added increases the error instead of reducing it in the case of + feedback?]
How can we analyse circuits where both are present?

Whoever answers both at the same time in a coherent manner wins a pot of votes.


texts: Are electret microphones frequency mixers?

texts: I wonder if common electret microphones are frequency mixers. That is, say, when two signals pass through the diaphragm, will two new signals f1 + f2 and f1 - f2 be produced if the sound pressure is around 70-80dB-spl? If they are, how significant are the two signals - will the power levels be roughly the same as the input?


texts: Is it possible to protect against ANY overvoltage?

texts:
Inspired by this question.
Suppose I'm making something like a security system and I'm worried about a malicious person trying to knock it out with high voltage on some of the incoming wires. Let's say my adversary has time to prepare and can rig up a device that provides a brief high voltage pulse. I'm not sure how high would be realistic, I'm guessing something on the order of 10-50kV.
Another scenario is mother nature - an unfortunate lightning strike directly into the power supply cable.
Ideally the protection system should be undamaged and can reset when the threat is over, but it would also be acceptable to have replaceable burnt out parts, as long as the rest of the system stays safe and operational and can raise an alarm.
Is this realistic? How would it be done?
I'll admit that this is a purely theoretical question born out of my own curiosity and I don't have a real project behind it. :)


texts:
I would like to compute maximum speed (RPM) of my bipolar stepper motor 42BYGHM809 -- rated voltage 2.7 V, rated current 1.78 A, phase resistance 1.6Ohm, phase inductance 2.5 mH.

I know how to compute speed if I use maximum rated voltage for this motor (cca 6.6 ms per step -> 0.38 rotate per second).

But how to compute speed if I am using A4988 stepper driver and voltage is 12 V?


texts: I understand that the NE5532 is an evergreen in audio applications. Which other op-amps would you consider for preamp, filter and other high fidelity audio applications?


texts: Does Cortex m3 parse a firmware code from -code D-code bus?

texts:
I'm trying to understand the reason of I-code and D-code bus in Cortex M3 and how simple arbiter into single slave(Flash/ROM/RAM) can make an improvement performance of device.
(https://community.arm.com/developer/ip-products/system/f/soc-design-forum/2045/arm-cortex-icode-dcode-system-buses/6884#6884)
In the Cortex M3 TRM document, Cortex M3 core consists with a Bus matrix by 3 bus of I,D and S.
As far as I know, generally, these 3 bus connect to a simple AHB bus(CODE AHBM) with memories like this.
https://imgur.com/a/6gbtxki
Why I-code and D-code bus separated in Cortex M3? and how single arbiter such as AHB bus (CODE AHBM) will help for performance?


texts: Replacing 18650 batteries for AA batteries

texts:
I bought a robot that requires batteries. I did not realize it needed two 18650 batteries. In the docs it says it requires at least 7.2V. How can I use AA batteries to power it? I am thinking 5 batteries would suffice but I am not sure there are battery cases for 5 AAs
Any suggestion?


texts:
I've made simple schematic for a UPS for Raspberry  Pi. It contains a 12V Lead Acid Battery (40Ah), 5V LM7805 regulator and some capacitors. I'm supposing max 1.2A load from Raspi.
Should I add something? I'm totally noob at designing that type of circuits.


texts: Differences in using c user-defined functions on PC and on ARM

texts:
I am new to programming in c and to ARM also, so forgive me silly question. I would like to find answer on the net rather than to bother you, but there is not many materials in the web.
I am using Arduino Due board with Atmel SAM3X8E, ARM Cortex M3 and Atmel Studio 6 instead of Arduino IDE.

I wanted to create simple program based on sleep function to blink diode. Sure, there is no point in using sleep function instead of timers. I was just about to check if that work and get familiar with interrupts. But it doesn't work...

Because as I found out here there is no delay functions for ARM, so I created my one.
When I put the for loop into main function (In the places I show in comments) everything is okay, diodes blinks alternately. When I use mySleep() they both blink continuously. I've generated similiar program in CodeBlocks on PC with stdio.h and printf instead of asf.h and PIO registers. That works as I wanted. Here is code below:

#include <asf.h>

void mySleep(void);

int main (void)
    {
    PIOB->PIO_PER = PIO_PB26;
    PIOB->PIO_OER = PIO_PB26;
    PIOB->PIO_PUDR = PIO_PB26;
    PIOA->PIO_PER = PIO_PA14;
    PIOA->PIO_OER = PIO_PA14;
    PIOA->PIO_PUDR = PIO_PA14;

    while(1)
    {
        PIOB->PIO_SODR = PIO_PB26;
        PIOA->PIO_CODR = PIO_PA14;
        mySleep();
        //for(unsigned long long i=0;i<1000000;i++);
        PIOB->PIO_CODR = PIO_PB26;
        PIOA->PIO_SODR = PIO_PA14;
        mySleep();
        //for(unsigned long long i=0;i<1000000;i++);
    }
}

void mySleep(void)
{
    for(unsigned long long i=0;i<1000000;i++);
}

Program is bulit with no error.
Here is my question. What is the difference between programming on PC and ARM? What should  I do to get user-defined funtion work? Is there any additional library needed?

Thanks in advance.


texts:
I'm building a power monitor (so I get notifications if the power is lost in one of the inputs). To monitor it safely, I used these 220/12 0.35VA transformers (http://www.hahn-trafo.com/english/pcb-transformers-bv20.php), I have them in a row one next to another. The transformers each are connected like this:

simulate this circuit – Schematic created using CircuitLab

The LED is for indication and the optocoupler is for connecting to Raspberry Pi.

The transformer is rated for 29mA and the actual load is lower (but not by much).

The transformers get quite hot (sticking a temperature probe between two transformers I get 70C). The manufacturers website says that the transformer is rated for "ta 70C/B". Am I still OK or do I need to add a fan?

EDIT: I connected both LEDs in series with total 2K series resistance. The temperature dropped to 58C.

EDIT2: Connected a 390R resistor in series with the diode (the PSU designer software showed that it would reduce the peak current), didn't help. Probably the 1.2W no-load dissipation as specified by the manufacturer adds quite a lot to the temperature. Added a fan to circuate the air (this is in a 1U case). Hopefully it will reduce the tempaerature.

What is a "normal temperature" for a transformer? I know that some bigger transformers get quite hot when working at specified load (no rectifier, just transformer and vacuum tube heater), don't know about the little ones - I do not have a lot of experience with very low power devices such as this.

EDIT3: With a fan the temperature is ~43C on the transformer that is furthest away from the fan. Is that considered good enough? The 58C with no fan looks to me too high, but should be below the 70C spec for the transformer (in case the fan fails).


texts: My USB D+ and D- signals have what looks like a clock signal embedded onto it. The chip is a ISP1362

texts:
I am trying to load a firmware up-rev to a device with a USB stick. It doesn't see the stick. My USB D+ and D- signals have what looks like a clock signal embedded onto them. The chip is an ISP1362 USB OTG controller see www.farnell.com/datasheets/1668574.pdf

I have not found any components that seem to be bad.
To see a picture of the D+ incoming signal that looks like it has the clock signal mixed into it, copy and paste the following into a separate window.

The scope is set at .5 usec/div.

Pin 48 is wrong on the schematic, it is pulled low.
Here are the readings I measured: on ISP1362.

Pin
20 3v
21 3v
22 3v
28 3v
29 3v
23 0v
59 0v
60 3v
48 0v
45 3v
30 3v
41 5v
46 signal shown when USB first inserted, otherwise 0v
47 inverted signal shown when USB first inserted, otherwise 3v
33 0v
34 0v
61 3v
62 3v
56 5v
4, 14, 26, 40, 52, 56   3v
1, 9, 19, 27, 57, 51     0v

Any guess as to what the problem might be?


texts: How would I delay a power on and power off

texts:
I need to delay power to the motors for my CNC driver project (using Toshiba TB6560 ICs, which require the motor power to be switched on after logic power and switched off before logic power).

I wanted to use a relay, which would be switched on by a RC delay circuit and enabled the motor power supply, and a big capacitor to supply the logic with power for a while after power off.

This is my current circuit:

Is this approach a good one? Would the circuit work?


texts: What is v in p=IV if I want to use p=IV to calculate power loss

texts:
I know that we generally use p=I^2R to calculate power loss and if we want to use p=V^2/R, the v is voltage drop. Is it true that the v in p=IV, when calculating power loss is also voltage drop?

Thanks for answering!


texts:
I have started a project in which I'm supposed to build some sort of a bluetooth headset. This bluetooth headset is suppose to be connected to any smart phone (basically android). I'm thinking about using some eval board like Arduino and also to use RN52 bluetooth breakout board.

The reason I'm using Arduino is that the bluetooth module should receive the sound signal from the main board (Arduino) and then stream it, as audio, to the smart phone. Same story about receiving audio from the smart phone and passing it back to the main board.

In other words I can not use the mic/speaker in/out pins of the bluetooth breakout board itself. I know to pass digital data between bluetooth breakout and the main module, I have to use PCM ports on the breakout.

So now here is my question: if I use the PCM pins on the breakout, when sending and receiving the data to/from the smartphone, will the smartphone be able to understand this is a sound signal? because if I use mic/speaker pins of the bluetooth breakout, the android device will recognize the bluetooth module as a true wireless headset and will communicate all the sound data to it.

But I'm not sure if this is the case when the bluetooth module is receiving/sending sound signal from/to the main board.

P.S: in case you are wondering why I want to generate/get the sound signal on the main board (e.g. Arduino) its because I want to do some sort of signal processing on the digitized sound signal.


texts: Clip a PCB against a 3 mm plastic protection

texts:
Is there a way to clip the PCB against the 3mm plastic protection surface? The image is below.
I need that it stays in the position shown in the image, with the connectors side sticking out.
That PCB is just for the example, it will be a new PCB so I can change its form or placement to solder some kind of clip to the PCB that would just clip into the 3mm plastic protection.


texts: Rpms required to generate electricity by means of cycling

texts:
I'm making a bicycle generator, and am trying to search for the right motor. I need to know at how many rpms a motor would need to be rated to generate a significant amount of electricity (like, to charge a laptop). Also, is there any type of motor from an old device that would work well for this (like an electric weed wacker motor).
Edit: I'm planning on using a 2750RPM scooter motor (24V, 250W)

Thanks


texts: Does resistance depend on shape of conductor?

texts: The area,length and material is same. Example a circular and square crosssection having same area


texts: Essential Prime Implicant with Don't Care

texts:
According to me, 3 is the number of Essential Prime Implicants.

  If a don't care is used in getting minimal solution, then the group
  with that don't care can also be considered as EPI(provided it is
  grouped only once). Here, don't care must be included to form a quad.
  That quad is necessary to form Minimal Expression.

This is how minimal expression is obtained.

Thus we have 5 Prime Implicants and 3 Essential Prime Implicants.

So, Am I correct?


texts:
I am looking for experimental data on the experimental strength of magnetic fields inside ferromagnetic materials. Here is what I mean.

If all of the magnetic moments of the molecules are aligned in the same direction in the material will act as a bar magnet with field straight \$H_0\$.

Theoretically one could just compute this field by adding up all of the of magnetic fields of the individual molecules.

Various real-world considerations makes me feel as this isn't likely to be too accurate of a measurement.  Is there a resource with experimental results for the strength of \$H_0\$ for various ferromagnetic materials?

Edit: To add to Phil's post below this can be computed from knowing the experimental saturation permeability \$\mu_{sat}\$ and the field strength at which it occurred \$H_{sat}\$.


texts:
I'm in need of an H-Bridge capable of driving moderate-high current for motors on a small car (7A peak, 2-3A nominal, 12-14 VDC), and I'm hoping to control it with two (2) digital pins (5 VDC).

I've come up with the following controlling circuit which, based on the 2 inputs (FWD, REV), I think/hope are capable of the 4 desired states:

Coast: FWD=Low, REV=Low
Forward: FWD=High, REV=Low
Reverse: FWD=Low, REV=High
Braking: FWD=High, REV=High

So my questions are:

Are there any actual op-amps that will work in the circuit?  I only have a few ICs in my stock (LM339N) and it doesn't work when prototyped (even with pull-ups since the outputs are OC).
I hope to be able to drive it using PWM (probably from an Arduino).  With one pin Low and PWM on the other it should alternate between states 1-2 or states 1-3.  Is this possible, and safe?  Or are there timing issues at the transitions that I should concern me?
Ultimately, am I deluding myself or can the circuit work as I describe above, either as-is or with some tweaks?

Schematic intents: R1-R4 limit current to the MOSFETs, R5-R6 give a ~2.5V reference voltage (Vref) for comparison with the input signals. R7-R9-D2 (R8-R10-D1) shift reference voltage on pin 5 (pin 8) so Q3 (Q4) cannot be on with Q1 (Q2) and short/drain the battery.  R11,R12 pull the inputs low to disable the motors when the digital inputs are disconnected.

Edit: This is for a single, hobby project at home that I expect to wire up on a simple proto-board, not even a small-run fabricated PCB.

I added emphasis on the 2nd half of the first sentence (2-wire control) - which was my primary purpose in posting: I wanted a 2-wire controller to make it impervious to software bugs.


texts:
Would it be possible to debug/program another PCB including an STM32 MCU with the debug connector provide on the Nucleo-G474RE? (I don't have an external programmer yet)
What would you recommend for future designs. add a JTAG connector on the PCB and always flash the STM via the JTAG or create a bootloader and do it over USB?
I guess if I want to want to flash a bootloader in the STM, I will need the JTAG connector anyway, so the USB connector will only cost me space on the PCB. Or is there another way to load a bootloader?


texts:
What is the difference between these parts? The datasheet shows completely different pinnings, but both are specified over the same range and both have the A, B and ungraded specifications for tolerance.

Just curious.


texts: Thevenin to Norton transformation question

texts:
I know that I can simplify the circuit below by finding a voltage source + resistor combination and transforming that into a Norton equivalent, but in this case, I can apparently combine the two circled resistors into one 6k resistor and create a Norton equivalent where the current sourse is outputting 2mA in parallel with a 6k resistor.

I don't understand why the two circled resistors can be combined though. Even though they have the same current, they're not in series, so they can't be combined, right?


texts:
In Altium Designer, how do I change the radius during interactive arc routing?
Here the radius is 100mil, but I need it tighter.


texts: How many different frequencies have or are being used, and what for? Also, what do they sound like? I have heard of 25, 16.66, and 400 to 500hz in planes. Are there others?


texts: How do image sensors output in different resolutions?

texts:
Say an image sensor has an array size of 1280 x 800 pixels.  Its specifications state that it has output support for the following resolutions: WXGA (1280 x 800) and VGA (640 x 480).

My question is the following:  If we choose to output images in the VGA format, which part of the original 1280 x 800 array is the 640 x 480 extracted from?  Is it taken from the middle?  Is it just a sub-sampled (or averaged) version of the original array?

[Optional follow-up: Note also that the aspect ratios of the two resolutions are different; could that have an effect on the camera's intrinsic parameters (i.e., pixel size, aspect ratio, principal point) when choosing the smaller resolution?]


texts: Can two batteries be connected both in series and parallel using an isolated 1:1 DC/DC converter?

texts:
I have two 7.4V batteries. I want to use the series 14.8V voltage to drive a load but I also want to use them paralleled to drive a lower-voltage load.
So would it be possible to connect an isolated 1:1 DC/DC converter to one of the batteries and connects its Vout+ and Vout- to the + and - of the other battery?
There's the additional requirement that the grounds of both loads have to be shared.


texts:
I want to simply assign (copy) a bit in the IO register from some other register bit (or flag, or as a result of some comparison). Now I am using following (PORTD[2] := r0[3]):

    sbrc r0, 3      ; Skip if Bit in Register is Cleared
    sbi  PORTD, 2   ; Set Bit in I/O Register
    sbrs r0, 3      ; Skip if Bit in Register is Set
    cbi  PORTD, 2   ; Clear Bit in I/O Register

But is it optimal? Is there better way? How to make it with other sources - some flag for example C or T?


texts:
I was wondering how many watts an AM radio station outputs, and if I can calculate the watts on a tuned antenna by this equation:

Where Win = the watts input for the antenna, Wout = the watts output for the radio station, r = distance from the transmitter, and Y = how much rf the antenna gets from that square metre (I'm expecting Y to be like 0.1% or something because it's a pretty small antenna).


texts:
Background:

My photo diode is here
Characteristics are PW 10ns-150ns, PRF - 1Hz-1Khz, current output 10nA-100mA

i have selected a TIA for processing the above signal to an extent, by using LT spice simulator i was able to simulate the IC and its behavior and checked the performance to an extent.

but i want to emulate the photo diode behavior so that i can feed a signal similar to photo diode to my read out circuit

Problem statement:

in short i want to know how can i create a current source, in fact a pulsating current source with above characteristics,

What i want to try :

to solve the problem i have decided to go with a voltage source like this, what if i place a series resistor between TIA input and voltage source, by tweaking the series resistor wont i be able to change the current to the TIA ? am in the right direction ?? is there any alternate approach to create a current source having above characteristics ?

EDIT:

Any way due to opamp saturation at maximum the current can only go to vcc/rf which is 2.5V / 1K= 2.5mA

Please observe that the circuit shown is meant only to showcase what am i trying.

simulate this circuit – Schematic created using CircuitLab

EDIT 2:

I want to generate a minimum current of 30uA and maximum 2.5mA with above pulse characteristics, The voltage source is a positive polarity one, while i have negative polarity supply also, link to source

As raised by the answers, to clear more on the circuit, the circuit involves a protection diode at opamp input to surge extra current and also protect opamp input from voltage greater than 2V, the TIA is followed by a inverter then a high speed comparator which is a LVDS output having a 100 Ohm termination, that is it !

Something like this :

simulate this circuit

I know few short comings of the circuit, i want measure as much is possible from the circuit,please throw your comments more on creating current source of characteristics discussed in background, if not the above circuit i can experiment with some other, but my main intention in this question is to discuss and come to a conclusion on  the best way to create a valid current source


texts: When I attach something sensitive like a analog camera and LCD screen to a car battery along with a switched high amp load like a power door lock actuator, I get video problems when the load is switched on AND switched off. Why is it that in a car, there is no problems with those same devices in the same scenario? What do they use to isolate these high amp devices from interfering with other electronics?


texts: VHDL how to make a process with sensitivity list wait?

texts:
I'd like a process to listen to changes in a signal, but not before 20 ns. How can I achieve that?
It doesn't seem possible to use wait statements in such a process, which makes sense since is has a sensitivity list.
What I'm really trying to achieve is a test bench that changes one signal indefinitely and another for like 5 ns after signal ready = '1'. But I don't know precisely when that will happen. I only know that before 20 ns the system is still resetting and hence I should not listen to changes in ready before 20 ns because then I'd get errors.
Alternatives to the approach in the question are welcome.


texts:
I am doing a PCB layout with one +12VDC input fused at 20A which breaks up into multiple fused branches that vary from 2 to 10A each. The input is a screw terminal barrier block and the fuses are vertical fuse holders for blade-style fuses.
I tried to lay it out so the main current path (running horizontally through the middle) has the shortest distance to all the branches. The scale here is that the board width (left to right) is about 2 inches.
Trace width calculators tell me that I need a 370mil trace if using 2oz copper, but how does this apply when the traces are short as shown? I can't really double it on the bottom layer because it would cut my ground plane. The width shown at the input is about 180mil.
Thanks :)


texts: Convert Astable Multivibrator square output waveform to sawtooth

texts: I designed an astable multivibrator by using BJT(necessary) to produce a square waveform, my question is how I convert the output signal from a square to a ramp waveform. Thank you


texts: what logic family does tri state logic fall into?

texts:
Here is a good Wikipedia on logic families.

This seemed like a particularly important line.

  Of these families, only ECL, TTL, NMOS, CMOS, and BiCMOS are
  currently still in widespread use.

I've been reading about tri-state logic, but I cannot seem to find the relationship to the logic families.  In this article, it says the logic families of circuits need to be compatible, so I just want to make sure I don't ruin the components that I buy.  See section #2.

  All circuits within a logic family are compatible with other circuits
  within that same family because they share the same characteristics.

How does tri-state fall into this?
What logic family would I have if I just had a HIGH/LOW, but not Undefined (open)?

Here's another reference to tri-state logic that I was reading.


texts: TM4C123, only one timer works at a time?

texts:
I am using TivaC TM4C123 MCU. I am trying to send data serially through one pin and a synchronized clock through another pin. Here is an illustration:

I used Timer0 module for the serial data and Timer1 for the clock. The frequency of the clock should be twice the data. Here is the important part of the code:

void DATA(long number, int iteration) //number: data to be send serially
{
    long x=0;                           // iteration: number of bits to send
    for(int y=0; y<iteration ; y++) {
        while((TIMER0->RIS & 0x00000001) != 1){}  //wait until Timer0 times out
        x= number & (0x1<<y);      //Get each bit individually
        if(x==(0X1<<y))            //If bit is 1
            GPIOF->DATA |= (1<<1); //Make PF1 High
        else if(x==0X0) //If bit is 0
            GPIOF->DATA &= 0XFD;   //Make PF1 Low
        TIMER0->ICR |= (1<<0);     //Reset Timer0 flag
        while((TIMER1->RIS & 0x00000001) != 1){}   //wait until Timer1 times out
        GPIOF->DATA ^= (1<<2);     //Toggle clock
        TIMER1->ICR |= (1<<0);     //Reset Timer1 flag
    }
}

int main()
{
    GPIO_INIT();   // Initiate GPIO
    TIMER_INIT();  // Initiate Timers with Timer0= 1/2 Timer1
    while (1) {
        DATA(0XAB01,16); // 0xAB01 16 bit data need to be send serially
    }
}

There is a problem in this code, which is both of the data and the clock have the same frequency, which means that Timer0 or Timer1 are disabled.

To make my problem more clear and easy to understand. I wrote two simple codes with a graph for each of them. Here is the first code: I am using While loop

int main()
{
    GPIO_INIT();
    TIMER_INIT();   //Timer0= 1/2 Timer1
    while (1) {
        while((TIMER0->RIS & 0x00000001) != 1){}   //Wait for TIMER0 to time out
        GPIOF->DATA ^= (1<<1);   //Toggle PF1
        TIMER0->ICR |= (1<<0);   //Reset TIMER0 flag

        while((TIMER1->RIS & 0x00000001) != 1){}    //Wait for TIMER1 to time out
        GPIOF->DATA ^= (1<<2);    // Toggle PF2
        TIMER1->ICR |= (1<<0);    //Reset TIMER1 flag
    }
}

Here is the output I got:

Here is the 2nd code: I am using If condition

int main()
{
    GPIO_INIT();
    TIMER_INIT();    //Timer0= 1/2 Timer1
    while (1) {
        if((TIMER0->RIS & 0x00000001) == 1) {    //If TIMER0 out timed out
            GPIOF->DATA ^= (1<<1);    //Toggle PF1
            TIMER0->ICR |= (1<<0);   //Reset TIMER0 flag
        }

        if((TIMER1->RIS & 0x00000001) == 1) {   //If TIMER1 timed out
            GPIOF->DATA ^= (1<<2); //Toggle PF2
            TIMER1->ICR |= (1<<0); //Reset TIMER1 flag
        }
    }
}

Here is the output:

Conclusion: When I used the if condition the two timers are working normally, but when I used While loop only one timer is working and the other timer is just using the same counts of the other.


texts: optical glow fiber for low-tech communication links?

texts: Can cheap "glow" optical fiber (or other inexpensive materials such as aquarium air tubing, etc.) be used for low-tech low-speed optical communications using just simple discrete components, such as ordinary LEDs and photo-transistors?  (and no fancy connectors). If so, over what distances and data rates (1 foot or 100M, 1 baud or 1 Mbit, etc.) might this work.


texts: Constraining a 7 segment display in VHDL

texts:
Right now I'm just trying to configure a single digit 7 segment display, and I'm pretty stuck.

All of the resources I can find say to use a 7 bit logic vector and just stop there.  So I understand how it works, the logic vector turns on (or in my case off, since the Nexys 3 apparently turns them off on logic high and on with logic low) with the position in the vector corresponding to a specific segment.

What I do not understand is how to constrain this 7 bit vector to the series of pins.  I know the basics of how constraints work (I would just put "LED" in the constraints file in the NET line in the UCF and this would turn it on when LED = 1 in the code) but I'm lost as to how to go about doing that.


texts: When to use a digital potentiometer vs PWM and mosfet?

texts: When would you use a digital potentiometer over PWM and a mosfet/transistor? I don't understand the advantages/disadvantages between the two.