texts:
I designed a PCB with the following schematics.

simulate this circuit – Schematic created using CircuitLab

The circuit uses a MAX6369 external watchdog timer which has an open-drain output(WDO) which is pulled low at a fixed interval. When the output is pulled low, the reset pin will be pulled low as well and light up an LED through a PNP transistor. However, this circuit does not work well as it lights up the LED at the fixed interval but does not pull the reset pin low. After debugging I noticed that when the transistor is removed the circuit works fine. I concluded that I forgot to put a base resistor which causes the transistor to be saturated and draws too much current from the watchdog. This prevents the reset pin to be pulled low properly.

So my questions are, Is my conclusion right? Is there anyway to save this circuit without adding additional components and just replacing existing components such as replacing the transistor with a low base current transistor?


texts:
As part of my university project I am trying to read NFC data (13.56MHz) at a longer range (~60 cm). I have already developed code that reads data from the card at close proximity, using libnfc and a standard USB based NFC reader.

I am facing the challenge to read data from distance. All the information I have seen out there seems to be a few years old with unsupported hardware.

My initial thoughts were to try to find a NFC reader that I could just plugged a bigger antenna, as you can do with 802.11 wireless technology...

I would appreciate some tips on how to achieve my goal, what type of hardware would I need? And could I still use libnfc and my code?

Cheers


texts: When to use slots instead of barriers in high voltage design?

texts:
I have read a lot of information about the clearance and creepage strategies, distances, materials, etc..

I am designing my first HV PCB, main LV circuit will be on TOP and HV (6KV) on the bottom. But I can' t avoid some low voltage points on the same side. Here I will be using insulation barriers to increase creepage and clearance at the same time. But I would like to use slots in order to separate and give some air gap between "hot" points. But when you put slots, the only factor that increase will be creepage. Clearance stills being the same with or without the slot.

So, here are my questions:

When to use slots instead of barriers?
When can be the clearence shortest than creepage?
Is it the same to put a 3cm slot between two points and to simply put a distance of 3cm without slot between 2 points?
How can it helps to avoid breakdown if clearance is the same at two both cases?


texts: Raspberry Pi : White/Blank screen with new shielded cable

texts:
I'm currently passing EMC tests at a test lab. For the purpose of the tests, I made a custom DSI cable for the official Raspberry Pi 7" screen with shield against EMI as the PCB of the official RPF screen is a big source of noise.
I've just received my custom made cable but I can't get an image on the screen with it. I've checked :

Pinout : OK
Continuity between Raspberry and screen : OK
Shorts between pins on the cable : OK

But still the screen only shows a blank/white screen and nothing else. When I switch back to the standard cable, the screen works as expected.
Here's a picture of the standard cable (up) and my custom made cable (down) :

Do you have any idea why my cable is not working ? I'm thinking about reflection inside the shield. Because of the shield, my cable could be self-poisoning. But, to be honest, I don't really know what's happening.
EDIT : I've tried something new. I removed the shield completely and the cable works fine. I took another cable and removed the shield only partially (but removed all connections to GND) and the screen works but I have a lot of black lines on it (like during conducted EFT/Burst tests).


texts: Help with designing negative part of Dual-Sided SMPS

texts:
For a project of mine, I'm trying to make a dual-sided SMPS that has independently variable positive and negative supply rails, current limiting, short circuit protection, etc etc...

My current plan of attack would to use a center-tapped transformer to convert wall power to about +/- 40VAC. I can easily rectify both and get about +/-28VDC. For the positive side supply I can easily use a voltage-controlled buck regulator.

My issue is that i don't know how to step down negative voltage for the minus side! i feel like a topology similar to a buck should work, but I'm not sure how to keep the transistors operating in the right modes.

I am considering using a buck-boost to get the negative output, but the controls for it are a lot higher :(

My question is basically, how could i create the variable, regulated negative voltage supply?

thanks


texts: Why is my dark activated circuit not working?

texts:
When I turn my circuit on the LED turns on but even in the dark the LED is still on.

Can someone help me?


texts: Strange Behaviour Using LM358 Op-Amp as Wheatstone Bridge Difference Ampliflier

texts:
I've been working on building a circuit which uses a wheatstone bridge to find the value of a resistance temperature sensor (Danfoss AKS 21) and then passes that to a differential amplifier the output of which is to be read by an ADC.

When I read the voltage across the bridge with a multimeter without the op-amp circuit connected, I get values that I expect (at room temp around 0.87V). However, when I connect the circuit to the op amp, the voltage across the bridge drops to around 0.5 V.

I've included a schematic I made of the circuit below. Would really appreciate some help figuring out where I'm going wrong.

I'm using the same 3.3 VCC to power the op-amp as the rest of the circuit.

Thanks in advance everyone,
Al


texts:
I have an old laptop that uses a SLA Battery and I'm wondering what sort of circuit would be need to convert the charging circuit for NiMH Cells.

Many manufacturers were able to do some time ago but that information has been lost. The Replacement NiMH Battery had two 6v banks and the computer will output 7.5v to the battery when charging. So I assume I'd need two 45C temperature cutoffs (one for each bank) and also a boost converter to a voltage regulator and then a NiMH charging circuit but I can't find a circuit that will allow the same input and output since the battery only has 2 terminals.


texts: Boosting current on Genuino MKR1000 digital pin output

texts:
I am trying to switch on a G5Q Relay on a Genuino MKR1000.
I am able to do it using VCC (3.3v) but not with Digital I/O pin (Also 3.3v) this is because the current from digital pin is lower(7mA). I am new to electronics. How can I boost the current to the relay without damaging my board?


texts: How to control the non-isolated bidirectional buck-boost converter?

texts:
I have been working on a control software for below given bidirectional buck-boost converter.

The planned usage is for charging and discharging of a traction battery in electrical vehicle.
I am not sure how to control this type of dc-dc converter.
From my perspective there four operating modes:
a) battery charging in buck mode     (S1: pwm, S2: off, S3: off, S4: off)
b) battery charging in boost mode    (S1: on,  S2: off, S3: off, S4: pwm)
c) battery discharging in boost mode (S1: off, S2: pwm, S3: on,  S4: off)
d) battery discharging in buck mode  (S1: off, S2: off, S3: pwm, S4: off)
As far as the operating mode selection I think that
a) selection between battery charging and discharging takes place based on commands comming from
higher layer which is able to made a decision whether there is enough energy in the system or
there is a lack of energy
b) selection between buck mode and boost mode takes place based on relation between Vbus1 and Vbus2
voltages
As far as measurement both Vbus1 and Vbus2 are measured along with the inductor current. Only for clarification. The bus1 consists of capacitor C1, the bus2 consists of capacitor C2 in parallel to the traction battery.
As far as the control algorithm I think that there should be two cascaded PI loops (external voltage
loop and internal current loop). At the output of the internal PI loop there is the duty cycle for
the transistors switching. One set of cascaded PI loops is for battery charging (battery voltage - Vbus2 - is regulated) and one set of cascaded PI loops is for battery discharging (dc bus voltage - Vbus1 - is regulated).
Please can anybody tell me wheter my understanding how to cotrol the bidirectional buck-boost converter
is correct? If not so can anybody recommend me some information source? Thanks in advance for any suggestions.


texts: How to listen to beacons(broadcaster) using the simple_observer example?

texts:
I am using the TICC2640 for this purpose.

I am trying to use the simple_observer example from the SDK to listen to beacons. I am able to scan the devices and print their MAC addresses. I am broadcasting the beacon via an Android app called the "locate beacon". The example scans up to 8 devices while printing their MAC addresses. I have slightly modified it to now print the event type and address type as well as shown below.

// Display the indexed scanned device.
Display_print1(dispHandle, 2, 0, "Device %d", (scanIdx + 1));
Display_print0(dispHandle, 3, 0,
Util_convertBdAddr2Str(devList[scanIdx].addr));
Display_print1(dispHandle, 4, 0,"addrType: %d",devList[scanIdx].addrType);
Display_print1(dispHandle, 5, 0,"eventType: %d",devList[scanIdx].eventType);

Issue-1: Among the scanned 8 devices, none of them is the device(my phone) that is broadcasting the beacon. This I have cross-checked with the displayed MAC address. How do I get this example to scan for the device that is broadcasting (beacon)?

Issue-2: I need to listen to the beacon packet and parse it for some purpose. However, from the above, I am not able to get the beacon to do anything with it.

There also seems to be no example or any such starting point when it comes to seeing beacons using this example. Is there any piece of code or specific configuration that can help me achieve the this?

Any support with the above would be appreciated.


texts: If two components on same net both require capacitor do I need to put it twice?

texts:
This is a pretty simple question, I'm guessing its a not so simple answer.

Basically I want to know if I have two chips on my board, and on each of their data sheets it calls for a 0.1uF capacitor to be connected to the Vdd and Vss, do I need to add two 0.1uF capacitors?

what if they are far apart on the board?

Also what if one calls for a 4.7uF and the other calls for a 0.1uF on VDD then what do I do?

UPDATE:
I feel I need to include more information to help guide the answers.
I have several components all connected to either AVDD or DVDD and they all call for various capacitors, such as several needing 0.1uF, several needing a 10uF, another needing a 4.6uF and a few needing a 0.1uF and a 1uF all connected to AVDD.  all within an inch or two of each other.

What approach should I take?


texts: MCP6002 op amp without Vss Vdd connected?

texts:
I'm building a circuit from a schematic - K6BEZ Antenna analyser

Note there is no connection to pin 8 or 4 (Vss and Vdd) on the uppermost op-amp - as there is in the bottom one.

The circuit is not working - there is never any voltage at A0 - leading me to think there is something wrong with the top "half" of the circuit.

I have not used op amps before. It strikes me as odd there is no ground connection and no voltage supply to the op amp in this half of the circuit.

Is it likely just an omission in the schematic (i.e. should I connect up pin 4 and 8 as in the bottom op-amp), or is this a valid application for an op-amp, and I have some other issue?

Cheers in advance.


texts: Random display temperature reader LM34 and 7107

texts: I am a beginner. I have been stuck on this for quite a long time. I am following this schematic. In replace of LM35, I'm using LM34. I am getting random flashes from the 7 segment - gibberish. My suspect is that I am not providing the right current to LM34 but I have no idea how I would go about calculating this.


texts:
I see these PCB material types often: FR4 epoxy resin, FR4 epoxy glass. I see epoxy resin is cheaper than epoxy glass (at least the price that I see from couple suppliers).

I wonder if there is a major difference between epoxy resin and epoxy glass, e.g. the way they are etched and transfer toner, or do they need different treatment on the manufacturing process? What are the main advantage or disadvantage to use epoxy resin?


texts:
I'm doing an assignment where I want create a setup to test wire connections in X-ray detector sensors. There are about 250 wires between this sensor and the control PCB. I want to test the connection in each of these 250 wires.

The ultimate goal is to put them for a temperature cycling test, and display on which cycles the wires are broken.

What would be the best way to inspect if there's connection in each of these 250 wires? Simply put, I want to know if every wires are still working.


texts:
Hello folks,

I've got some douts about how can finding the \$R_{th}\$ seen between \$V_{out}\$:

A: is a amplifier gain

The possible answer are:

A) \$ R_{th} = (A.R_s)\$
B) \$ R_{th} = (R_s + A)\$
C) \$ R_{th} = \frac{1}{R_s + A}\$
D) \$ R_{th} = (1+A).R_s\$
E) \$ R_{th} = (R_s + R_L).A\$

The correct answer is D.

My attempt:

Seems \$V_i\$ is a short circuit and the inputs amplifier are HiZ the \$R_{th}\$ will be:

\$ R_{th} = R_s + R(amplifier)\$

\$ R(\text{amplifier}) = 1V/I_N\$

\$I_N = A.1/(R_s+R_L) = A/(R_s+R_L)\$

\$R_{th} = R_s + (R_s+R_L)/2 = R_s(A+1) + R_L\$


texts:
I'm playing around with this op amp: https://www.st.com/resource/en/datasheet/ua741.pdf. My circuit looks like this:

It is hooked up to an Arduino Uno. I used analog read on the Arduino to read voltages at 2, 3, and 6. The pot allows me to vary the voltage at 3 from 0 to 5 V.
With R1 = R2 = 10K, I should have a gain of 2. I should be able to vary the voltage at 3 from 0 to 2.5 V and the output of the op amp should go from 0 to 5 V, right? I know I probably wont get quite to 0 or 5 V but pretty close.
However, the plot below is what I measure with the Arduino. As far as I can tell, the analog read value of 0 is 0 V and 1000 is about 5 V.

So the op amp appears to work but only in a vary narrow range. It looks like its pretty close to the upper limit, but doesn't get anywhere close to outputting 0 V.
Also, if I replace R1 with a higher resistance or R2 with a lower resistance, giving me higher gain, I get no response at all at the output. A3 remains at a constant value of around 800 no matter what the input is.
I'm new to op amps so I'm probably missing something obvious... Thanks!


texts: Resistor needed for: Arduino Micro + 12V Pump + HF3FA/005-ZTF relay

texts:
I am using an Arduino Micro to turn On/Off a 12 V Water Pump.
I am using a HF3FA/005-ZTF relay --> Link

Here's how I connected everything:

I control it with this code:

const int GO = 12;
void setup() {
pinMode(GO,OUTPUT);
}
void loop() {
digitalWrite(GO,HIGH); //WaterPumpON --> ON
delay(60000);
digitalWrite(GO,LOW); //WaterPumpOFF --> OFF
delay(60000);
}

Everything is working as it is supposed to:

QUESTION: Since I'm new electronics I would like to know if I need any kind of resistor somewhere within that circuit? I did not find similar circuits while googling and the only useful info was in this video: YouTubeLink_german and he does not use any resistors but he uses a different relay.


texts: How to make a piezoelectric transducer buzz louder?

texts:
I am trying to make a piezoelectric transducer buzz loudly, but have so far only been able to make it create a quiet hum. I have tried using a basic amplification circuit with an NPN, but this made very little difference.

I am working with microcontroller that words at 3.3v. How would I get a loud buzz even for a short period of time, from a piezoelectric transducer similar to the below image.


texts: Differences Between Smoothed DC & Not Smoothed DC With Respect to Heating

texts:
Are there any significant differences with respect to heat generation of a bridge rectified circuit with smoothed DC by use of a capacitor vs one that just uses the raw absolute value of the sine wave? I'm having a bit of trouble with my bridge overheating and I was wondering if smoothing the output would help. (Aside for putting a heat sink on it, which I'm in the process of doing) The bridge runs at 30A typically (rated for 100A) and starts getting hot kind of fast, but I only really use it for less than a minute anyway since the system I use it for is very efficient.

Edit 0: The load is used for various electrochemical reactions done at low voltage (9V DC) and high current (30A DC). The reaction doesn't really care whether the DC is smoothed or not. The question refers to how much heat the bridge is building up, not that I'm running a heater. I'll admit, when I first saw the comment on someone thinking I was running a heater I had quite the laugh (As I suppose with how much heat the bridge builds up if not monitered or used for more than 4 minutes I probably would be!).

Edit 1: Yes (Before anyone tells me), I know that it's a small spot welder essentially, and the proper fuses are in place.


texts: How to make a re-programmable microcontroller

texts:
I am looking to create a platform similar to Arduino for a side project using an ARM Cortex M4 based microcontroller.  The device essentially will communicate with a bunch of sensors on the board and relay that information through a USB Serial Connection to a connected USB host (similar to the Arduino Serial Monitor).  I am not using an Arduino because I would like to learn about how to practically prototype a circuit like this.

My question is, what do I have to do to make my microcontroller reprogrammable via a USB connection to a computer like how the Arduino is.  I am looking for a hardware explanation like what I need to include in my circuit to accomplish this goal.

Thank you and hopefully my question makes sense.

EDIT:
I am looking for possible components that I have to include in my board to allow for native USB programming.


texts: Ceramic (MLCC) versus Tantalum capacitors

texts:
From the perspective of an electronics designer, but also taking into account price/cost and social considerations (see Coltan mining and ethics link below), I tend to avoid Tantalum capacitors under many circumstances, while favouring Multi-Layer Ceramic Capacitors (MLCCs).

My question, bluntly stated is: In which specific cases should I be careful and continue using tantalum capacitors? All sorts of answers and technical approaches to this matter will be very useful to me (and surely for other designers).

Some specific aspects to look into:

Series equivalent circuit.
Microphonics. How bad are MLCC really are in this respect?
Capacitance dependence with voltage and temperature.
Overvoltage and failure modes.
Life expectancy and reliability.

Additional context:

I address specifically Surface Mount Technology (SMT), assuming more than 90% of all tantalum electrolytic capacitors are manufactured in SMD style.
I am focusing here on high-volume consumer electronics products, discarding specifically high power electronics applications, where other considerations may apply. I am not ruling out power conversion/management circuits, where the above considerations are key for capacitors.
You can read more about the Coltan social impact at the Wikipedia: https://en.wikipedia.org/wiki/Coltan_mining_and_ethics


texts: Is it safe to daisy chain extensions cords?

texts:
I recently set up a soldering station on my old desk in the corner of my room. However there are no power sockets near there so I had to daisy chain two extensions cords to deliver power to my solder station and fan. Is it a safe solution?
I read online that it is dangerous because you can overload the socket but I doubt that. I live in the UK and in every electrical appliance it is legally required to have a fuse, and just in case I made sure to check that every single appliance plugged in to the extension cords have a fuse. On every block of the power extension there is an additional fuse. I am also not exceeding the 13 amp limit of the plug, (double checked with a calculator). There is one more thing though, I am using the first power extension to power my desk (two monitors and pc) but that adding the current draw of that to my total current draw still does not exceed 13 amps. I live in the UK and the electrical system is pretty safe. A fuse for every plug, a fuse for every wall, safest plug in Europe (potentially the world) and an RCD that protects every socket in the house. Is it safe to do so?


texts: How to rotate 3D body around X axis in Altium Designer

texts:
I have a simple question about Altium Designer 13.1, to what I could not find the answer so far. How can I rotate a 3D body object around the X axis? I have checked at here and on Google without any success.

I have a triangular based prism:

I want to rotate this with 90 degrees around X axis to get this:

This prism is the only object I want to rotate on the mechanical 1 layer, anyone knows the way to do this?

Also, how can I draw shapes in the Z-X or Z-Y plane like I do in the X-Y plane?


texts: Does the avr 32 bit have similar instruction set from 8bit or atleast borrowed some? Is it a completely different microcontroller...I was thinking of learning arm if this was the case.I really want to know so atleast I would get to know if I will continue with avr 32 bit and learn arm later.


texts:
I understand this has been asked before, but I've never been able to find a satisfactory answer to the question I have, which is: in general, how do we treat the dependent sources in the small signal models when calculating the short-circuit time constants?

Case in point:
I ended up with the following circuit (in part) when doing the low-frequency analysis of a CS-CB circuit, for one of the capacitors:

From the example given in this question, I guessed that the equivalent resistance would be R1||R2. Or, as my lecturer said about a similar circuit, the right-half of the circuit is "completely separate" from the left-half.

However, I thought the way to compute equivalent resistance was to replace the capacitor with a voltage source, and to calculate the current? In that case, G would have a non-zero potential, and then wouldn't the dependent current source add current from the right-half of the circuit to the left-half...?

Am I understanding "equivalent resistance" incorrectly? When can we "ignore" the dependent source when finding the resistance "seen" by the capacitor?


texts: Can't receive CAN frame on STM32 because of unexpected collision

texts:
I’m trying to receive CAN frames on a STM32F412G-DISCOVERY with a SN65HVD233 transceiver, transmitted from a USB2CAN device. Both are connected on a bus of about 15 cm long with two 120 Ω resistors on each end.

I connected an oscilloscope to read the RX and TX pins on the STM32 board before they are transformed by the transceiver. When I configure the CAN controller in silent mode and send a CAN frame from the USB2CAN using:

$ cansend can0 '144#25'

I see on the oscilloscope on the RX pin the full frame (yellow is the board’s RX, blue its TX):

NB: the cursor indicate the time interval of one bit (2 µs, bitrate is 500 kb/s).

(The HAL_CAN_Receive call still timeout, but that is another problem.) But when I put the controller in normal mode, here is what I measure:

And here is the code:

hcan1.pTxMsg = &g_out_msg;
hcan1.pRxMsg = &g_in_msg;
hcan1.Instance = CAN1;
hcan1.Init.Prescaler = 12;
hcan1.Init.Mode = CAN_MODE_NORMAL;
hcan1.Init.SJW = CAN_SJW_1TQ;
hcan1.Init.BS1 = CAN_BS1_1TQ;
hcan1.Init.BS2 = CAN_BS2_1TQ;
hcan1.Init.TTCM = DISABLE;
hcan1.Init.ABOM = DISABLE;
hcan1.Init.AWUM = DISABLE;
hcan1.Init.NART = DISABLE;
hcan1.Init.RFLM = DISABLE;
hcan1.Init.TXFP = DISABLE;

if (HAL_CAN_Init(&hcan1) != HAL_OK)
    fatal_error("failed to init HAL CAN.");

CAN_FilterConfTypeDef sFilterConfig;
sFilterConfig.FilterNumber         = 0;
sFilterConfig.FilterMode           = CAN_FILTERMODE_IDMASK;
sFilterConfig.FilterScale          = CAN_FILTERSCALE_32BIT;
sFilterConfig.FilterIdHigh         = 0x0000;
sFilterConfig.FilterIdLow          = 0x0000;
sFilterConfig.FilterMaskIdHigh     = 0x0000;
sFilterConfig.FilterMaskIdLow      = 0x0000;
sFilterConfig.FilterFIFOAssignment = 0;
sFilterConfig.FilterActivation     = ENABLE;
sFilterConfig.BankNumber           = 14;
if (HAL_CAN_ConfigFilter(&hcan1, &sFilterConfig) != HAL_OK)
    fatal_error("failed to setup CAN filter.");

HAL_StatusTypeDef can_status;
if ((can_status = HAL_CAN_Receive(&hcan1, CAN_FIFO0, 20000)) != HAL_OK)
    fatal_error("failed to receive frame: %d", can_status);

It seems that the emitter (USB2CAN) tried to write a recessive (1) for the 2nd bit of the ID while the receiver (STM32) sent a dominant (0): the emitter detected that collision and stopped emitting.

Why did the STM32 CAN controller sent that dominant bit which stopped the communication?


texts:
I'm designing a battery charger, and I need to discharge every cell of a LiPo battery on its own at some point using a discharge resistor ( cell balancing ) by controlling switches from a uC, one way would be using a relay or an optocoupler that would be completely isolated from the signal side, but optocouplers usually dont handle much current and i would need to add another transistor stage to handle that, same applies to a relay but in the other way, a uC cant source/sink enough current to switch the relay which again means an extra transistor stage is needed ( plus the diode )

But what about a transistor on its own ? would it work like that ?

There has to be a current path for the signal to go through which is normally done by connecting both grounds, but doing that here would short the cells since every cell would have a transistor on it controlled by the same uC ( every neg cell lead would be connected to the same uC control gnd thus shorting everything )

Can the control signal find a return path through the cells assuming the transistor can handle the volatge of the cells combined ?

not sure if this is the right title for the question.


texts:
I'm trying to communicate with a PIC32MX795F512H using UART but I get scrambled signs in my terminal.

I know it's a timing/clock issue but I have no idea where and how to fix it.
I am not using an external crystal and nothing is connected to the PIC (except the necessary minimum (caps, wires and a resistor)).

The code:

#include <p32xxxx.h>
#include <plib.h>

#pragma config FPLLMUL = MUL_20, FPLLIDIV = DIV_2, FPLLODIV = DIV_1, FWDTEN = OFF
#pragma config POSCMOD = HS, FNOSC = PRIPLL, FPBDIV = DIV_1

#define DESIRED_BAUDRATE    (9600)
#define SYSCLK          (80000000L)

#define CONFIG1 (ADC_MODULE_ON | ADC_FORMAT_INTG32 | ADC_CLK_AUTO |      ADC_AUTO_SAMPLING_ON)
#define CONFIG2 (ADC_VREF_AVDD_AVSS | ADC_OFFSET_CAL_DISABLE | ADC_SCAN_ON | ADC_SAMPLES_PER_INT_1 | ADC_ALT_BUF_OFF | ADC_ALT_INPUT_OFF)
#define CONFIG3 (ADC_CONV_CLK_INTERNAL_RC | ADC_SAMPLE_TIME_15)
#define CONFIGPORT (ENABLE_AN15_ANA)
#define CONFIGSCAN (SKIP_SCAN_AN0 | SKIP_SCAN_AN1 | SKIP_SCAN_AN2 | SKIP_SCAN_AN3 | SKIP_SCAN_AN4 | SKIP_SCAN_AN5 | SKIP_SCAN_AN6 | SKIP_SCAN_AN7 | SKIP_SCAN_AN8 | SKIP_SCAN_AN9 | SKIP_SCAN_AN10 | SKIP_SCAN_AN11 | SKIP_SCAN_AN12 |  SKIP_SCAN_AN13 |  SKIP_SCAN_AN14)

unsigned char data;
int pbClk;

void initializeADC(){
    CloseADC10();       // Generally, you should disable the ADC before setup.

    SetChanADC10( ADC_CH0_NEG_SAMPLEA_NVREF);
    OpenADC10( CONFIG1, CONFIG2, CONFIG3, CONFIGPORT, CONFIGSCAN);
                // Setup for the ADC10.
    EnableADC10();      // Enables the ADC10.
    while(!mAD1GetIntFlag() ) {}; // mAD1GetIntFlag() checks the interrupt flag for the AD10.
                      // Waits till a conversion is finished so that there's
                      // values in the ADC result registers.
}

void initializeLEDBar(){
    TRISDCLR = 0xFF;    // Sets pins RD0 to RD7 as digital outputs.
}

void initializeUART()
{
    // Optimize PIC32 performance and return peripheral bus frequency
    pbClk=SYSTEMConfig(SYSCLK, SYS_CFG_WAIT_STATES | SYS_CFG_PCACHE);

    // Enable UART1 and set baud rate to DESIRED_BAUDRATE=9600
    OpenUART1(UART_EN, UART_RX_ENABLE | UART_TX_ENABLE, pbClk/16/DESIRED_BAUDRATE-1);

    while(BusyUART1()); // Wait until the UART module is free
    putsUART1("Turning the potentiometer will change characters on screen!");
}

//     ==============================================================================================

int main(){
    initializeUART();   // Initialize the UART module
    initializeADC();    // Initialize the ADC10
    initializeLEDBar(); // Initialize pins RD0 - RD7 as digital outputs

    while(1){

        // Map the 10 bit analog value to a value between 33 and 126, and bit-mask it to 8-bits
        data = ((ReadADC10(0)/11) + 33) & 0xFF;
        LATD = data;                // Latch the data to the port D pins

        while(BusyUART1());         // Wait until UART2 module is not busy
        putcUART1(data);            // Transmit 'data' through UART
        putcUART1('13');            // Transmit '13' (carriage return)
    }
    return 1;
}


texts: 15MHz photodiode PCB, feedback requested

texts:
I've developed a 2-layer 15MHz photodiode amplifier board. The first stage is a transimpedance amplifier using AD8065. The second stage is using a current-feedback amplifier, THS3091. Power is +/-12V fed off-board, into J2, from a semi-regulated source, which is then made 'pure' using some LDOs.

Using the formula from the Ad8065 datasheet, I should be able to get at least 15MHz bandwidth using the feedback loop shown. The PCB:

I've done a few unusual things with this PCB, and I have some questions;

1) I've cut away the ground plane at the suggestion of the datasheet; the high-impedance input nodes of these op-amps is particularly susceptible to stray capacitance. A similar design can be found from TI, where they also cut away the ground away from the input nodes of the op-amp. This seems to be standard practice with current-feedback op-amps as well, so I've done the same cutting for the THS3091.

Note that I've cut the ground such  that there is no 'loop' made by the ground plane. Is this correct to do? Would it be wise to stitch them with a capacitor?

2) I've added a guard trace around the inverting input of the TIA to protect it from stray surface currents. I've done this because my photodiode's short-circuit current is 1uA, so I figure I'll be using it around the 10-100nA level. Since I'm using OSH-park I'll have to manually remove the solder-mask on it, but that is fine?

3) I am not sure that R7 should be there at all (I've inherited part of this design from a colleague). R4/R9 balance the admittedly minimal input bias current, but I don't know what R7 is doing at all. It seems to be for impedance matching, but the traces here are so short I don't think it matters?

4) Regarding C3 and C4, which don't have specified values, I think these should be equal to the capacitance seen on the - input of the op-amp? Again something I've inherited.. Otherwise the design makes sense to me.

Any feedback on the design and PCB would be appreciated!!

Edit: one more thing, my placement of the bypass capacitor's was somewhat arbitrary; when routing I didn't really keep track of which capacitor is which. I am planning on placing the smallest bypass caps closest to the chip.


texts: Is SystemVerilog string manipulation synthesisable?

texts:
I learnt that SystemVerilog provides a string datatype, which allows for many string operations, such as comparison, concatenation, length, etc.

Are those string operations synthesisable?


texts:
I'm implementing DMX on Arduino. DMX uses the RS485 standard to communicate.

In the specifications of RS485 it notes that there is a positive line, a negative line and a ground line. If the positive line is at higher potential than the negative line, a 1 is given. Vice versa for a 0. Now apparently the protocol doesn't measure the difference between each line and the ground, but only the difference in potential between the positive and negative line ( which has to be at least 200 mV).

This makes me assume it would be possible to easily drive DMX directly from Arduino, putting one line high (5V) and one low. However looking at the Arduino website with some information about DMX implementations, all information I can find is using some shield over the Arduino.

Is it necessary to use a shield, or will a direct connection work as well? I currently don't have any DMX components yet so I can't test it right away.


texts: Electronic hobbyist project-short circuit detector

texts:
I am doing this circuit which I took from from the internet for my project. I have 3 questions:
The circuit show glow 2 leds one if there is a short circuit if there is one in J1 and the other if there is no short circuit.
Consider the transistors as general purpose NPN and PNP transistors.
1. Will this circuit work?
2. If so,what is the logic behind the working of the circuit.
3. Does anyone have an idea of how the resistance values are calculated.

Thanks!


texts: In this common source stage, the inductor acts as a current source and capacitor act as a voltage source. What happens if the inductor and capacitor are replaced by current and voltage sources respectively? How will it affect the circuit performance?


texts: Excessive current in this inverter design

texts:
I made this inverter with Proteus.
The phases have no load at all, but the input current is very high (red arrow.)
This happens only when capacitors marked by the green arrows are connected.
They filter the signal to an almost perfect sine wave.
Without them and with inductor on one phase I get a very ugly sine waves - with noises.
Here's a picture:

So I think those two capacitors are necessary to smooth the signal, but how can that high current be possible? Is this some kind of bug?

Here's an improved version. I used 7812.50 Hz PWM:

This is slightly zoomed output:

More zoom:

And even more


texts: Altium bus connections with sheet hierarchy

texts:
I am using a bus to connect a repeating module to an MCU in Altium. I've tried numerous variations and can't find an example the same as this. I'm not sure which should have labels and which shouldn't or if they can be the same name.

What is the correct way to do this?

The actual circuit has many other connections but I have simplified the circuit down to figure out the problem.

Errors:

Sheet Hierarchy:

Top Sheet:

MCU: (Don't mind mess, just there to suppress driving force errors)

Module:

Edit:

I made a mistake when creating the example circuit which @Daniel pointed out. I fixed the mistake but the original naming problem still exists.

Old errors and top sheet:


texts: General approach to solving base resistor for a CE amplifier circuit that has no voltage divider at the base

texts:
Here's the general DC equivalent for the CE amplifier I am working on:

I have looked at different CE amplifier circuit problems to help me solve this one and almost all of them have the voltage divider configuration at the base side of the transistor circuit. With this circuit, RC, Vcc, Beta, and RE have been given. RB is the resistor I need to solve for. My approach at the moment is using load line analysis. However, I am not sure if it is the correct way to solving this circuit.

The full circuit looks similar to this:

Please note that I have presented this in a general form because I just want to be steered to the right path of doing the calculations for this particular setup. I am not seeking a full answer, just a guide :)


texts:
I have an inverter opamp with the next data :

\$A=-25\$
\$A_{ol}=20\frac{mV}{V}\$
Unity Gain Bandwith\$=10^{6}\$

Then asks for the cutt off frequency, so the open loop its passed to db
\$20\,\frac{V}{mV}=20log\frac{20}{0.001}=86.02059\,db\$
\$86.020=20log(\frac{Vo}{Vi})\$
\$\frac{86.020}{20}=log(\frac{Vo}{Vi})\$
\$4.301=log(\frac{Vo}{Vi})\$
So the \$A_{ol}=10^{4.301}\$
Usint the GBWP \$10^{4.301}f_{3db}=10^{6}\$
\$f_{3db}=\frac{10^{6}}{10^{4.301}}=50.0034\,Hz\$
Later its asked the values of output voltage if the frequencies are \$0.25f_{3db}\$ and \$5f_{3db}\$
so calculating the gains
\$0.25f_{3db}=(0.25)50=12.5\$
\$Af_{3db}=GBWP\$
\$A=\frac{GBWP}{f_{3db}}=\frac{10^{6}}{12.5}=80000\$
\$V_{o}=80000V_{in}\$
\$5f_{3db}=5(50)=250\$
and
\$A=\frac{GBWP}{f_{3db}}=\frac{10^{6}}{250}=4000\$
\$V_{o}=4000V_{in}\$
Is this the way to go? the results make me sense since its stated that before the cuttoff frequency the gains are very high but the bandwith its too narrow and over the cuttoff the gain
is less but the band its wider. But then why Im supplyed with the closed loop gain?


texts:
I have to find the Resistances R1 & R2 in order to have 0 - 3.3 V input on the ADC. What I cannot find is the Rth on the "Network" part of the circuit.
The text of the original question is:

A sensor produces a voltage between -5 and 3 V. The output resistance of the sensor is 470 Ω. The sensor must be interfaced to an ADC with an input range of 0 to +3.3 V and an input resistance of 3300 Ω. Determine the values of R1 & R2 for the interface network show. Check your work by analyzing the resulting network.

The answer supplied is:

R1 = 9300 930 Ω. R2 = 1400 Ω.


texts: Why is my constant current source (LED driver) pulsing?

texts:
I bought a current source to try to power some high brightness LEDs.  The LEDs take 350mA so I found a current source on digikey that matches that and ordered it:

http://www.phihong.com/assets/pdf/PDA012A-S.pdf

I just hooked it up to LED, and it is pulsing - flashing the LED about 3 times a second.  I put a 10 ohm resistor in series and put a scope on that.  I can see the spikes/pulses.  Why is it doing this?  I thought this source would deliver a constant current with nothing else in the circuit.  Do I need more parts?

Thank you.


texts:
In the documentation for a radio chip, I keep seeing the term 2-FSK, which seems to be a modulation scheme.

My understanding is that in FSK, data is encoded by emitting a carrier wave on a number of different frequencies. Is this right? How does this differ to 2-FSK?


texts: Simple Question: Connecting Mac with 3.3V FTDI USB Cable to 5V Breadboard

texts: I'd like to connect my iMac to a breadboard with a 3.3V TTL FTDI USB cable. The breadboard has an Atmega328 AVR microcontroller powered by a 5V regulated power supply. Sorry, if this is a naive question, but is it okay to have the cable powered by the iMac (I guess) at 3.3V and the breadboard running at 5V? Is that going to fry something? Do I have to have the breadboard running at 3.3V, too?


texts: How would I build a data acquisition system for SiPMs?

texts:
I try to build a radiation detector using of an arrangement of silicon photomultipliers (SiPMs) coupled to a scintillator and I want to read out the number of photons recorded by each SiPM sensor. I need to build a data acquisition system to store the recorded SiPM signals on disk, so that I can analyze them on my PC later. I expect event rates of around 10³ - 10⁴ events per second, where each true event generates a signal in several sensors at the same time. The rate per sensor is probably an order of magnitude smaller.
There are many academic publications dealing with the simultaneous readout of many individual SiPMs. However, these are mostly state-of-the-art experiments using high-end customized ASICs and VME crates, which are out of my reach. This is more of a hobby project and I do not have advanced equipment at my disposal. Therefore, I would like to build the readout chain with parts I can buy off the shelf. But I am unsure how to do this exactly and have some questions:

Is it realistic to attempt to create a multichannel SiPM readout at home with off-the-shelf components or is this too ambitious? Ideally, I would like to use parts I can either plug into a prototype board or solder manually, but especially some of the high-performance components (like a multi-channel high-speed ADC) mainly come in compact packages. Is it feasible to use evaluation boards to use such components?

Does the following readout chain seem like a reasonable approach or am I missing something important?

A simple bias voltage supply for the SiPMs
A shaping and amplification stage for each of the SiPMs to extract and form the signals
Digitization of the signals with a high-speed ADC
Feeding the digitized signals into an FPGA, where discriminator and trigger conditions are defined
Sending the accepted events to a PC, where they are stored for later evaluation

I'll probably start with a small number of SiPM sensors, but the goal is to use a large number of sensors simultaneously (I am envisaging 64 or more). I think this will be challenging and the above steps will become more complicated. I guess this would require a number of FPGAs working in parallel and then some coordination between them. Are there established ways how to handle a very large number of inputs?

Thank you in advance for your suggestions!

Note: This is an edited version of my original question to be more specific


texts: FMCW Radar Signal Processing based on MIT Open Course

texts:
I am working on a self-made FMCW radar - for the signal processing, I am using the MIT open course (https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/projects/) to model my code as a starting point. More specifically, I cannot understand how the range-time-intensity plot works. The code is posted below, but an FFT is never taken on the data, so I cannot understand how this algorithm works at all and I was hoping someone would be able to explain it. Thanks in advance!
%MIT IAP Radar Course 2011
%Resource: Build a Small Radar System Capable of Sensing Range, Doppler,
%and Synthetic Aperture Radar Imaging
%
%Gregory L. Charvat

%Process Range vs. Time Intensity (RTI) plot

%NOTE: set up-ramp sweep from 2-3.2V to stay within ISM band
%change fstart and fstop bellow when in ISM band

clear all;
close all;

%read the raw data .wave file here
[Y,FS] = audioread('running_outside_20ms.wav');

%constants
c = 3E8; %(m/s) speed of light

%radar parameters
Tp = 20E-3; %(s) pulse time
N = Tp*FS; %# of samples per pulse
fstart = 2260E6; %(Hz) LFM start frequency for example
fstop = 2590E6; %(Hz) LFM stop frequency for example
%fstart = 2402E6; %(Hz) LFM start frequency for ISM band
%fstop = 2495E6; %(Hz) LFM stop frequency for ISM band
BW = fstop-fstart; %(Hz) transmti bandwidth
f = linspace(fstart, fstop, N/2); %instantaneous transmit frequency

%range resolution
rr = c/(2*BW);
max_range = rr*N/2;

%the input appears to be inverted
trig = -1*Y(:,1);
s = -1*Y(:,2);
%clear Y;

%parse the data here by triggering off rising edge of sync pulse
count = 0;
thresh = 0;
start = (trig > thresh);
for ii = 100:(size(start,1)-N)
    if start(ii) == 1 & mean(start(ii-11:ii-1)) == 0
        %start2(ii) = 1;
        count = count + 1;
        sif(count,:) = s(ii:ii+N-1);
        time(count) = ii*1/FS;
    end
end
%check to see if triggering works
plot(trig,'.b');
hold on;
plot(start,'.r');
hold off;
grid on;

%subtract the average
ave = mean(sif,1);
for ii = 1:size(sif,1);
    sif(ii,:) = sif(ii,:) - ave;
end

zpad = 8*N/2;

%RTI plot
figure(10);
v = dbv(ifft(sif,zpad,2));
S = v(:,1:size(v,2)/2);
m = max(max(v));
imagesc(linspace(0,max_range,zpad),time,S-m,[-80, 0]);
colorbar;
ylabel('time (s)');
xlabel('range (m)');
title('RTI without clutter rejection');

%2 pulse cancelor RTI plot
figure(20);
sif2 = sif(2:size(sif,1),:)-sif(1:size(sif,1)-1,:);
v = ifft(sif2,zpad,2);
S=v;
R = linspace(0,max_range,zpad);
for ii = 1:size(S,1)
    %S(ii,:) = S(ii,:).*R.^(3/2); %Optional: magnitude scale to range
end
S = dbv(S(:,1:size(v,2)/2));
m = max(max(S));
imagesc(R,time,S-m,[-80, 0]);
colorbar;
ylabel('time (s)');
xlabel('range (m)');
title('RTI with 2-pulse cancelor clutter rejection');


texts: Does Vs+ and Vs- need to be connected on a TRS232E?

texts: I have a TRS232 RS-232 Driver(max232 equivalent). On the data sheet, it shows a capacitor on Vs+ and Vs- (1uF)and they just have arrows saying they go somewhere. Can I omit these connections and capacitors and if I do what are the side effects or issues that may arise from this omission?


texts: In the follwing, if the power dissipated between a and b is 210 watts, what is the value of Vb?


texts: How to avoid LDR controlled light self-latching?

texts:
I am planning on using an LDR to turn on a LED light (700 lunes warm white fixtures), when the main light in the room gets turned on. But this LED light is pretty bright on its own. I think I will end up latching the circuit with the light. What's the best way to avoid this? My planned circuit, resistor values are only representative.

simulate this circuit – Schematic created using CircuitLab

The room has a 100w led residential bulb, semi reflective tiling. The lights I want to control have some unknown pwm (555 circuit to a constant current switching circuit from what I can tell).


texts: what is the difference between ambient temperature and object temperature in MLX90614 sensor

texts: So, that i have read a source code of MLX90614 sensor. In the source code they have mentioned that ambient temperature and object temperature.as well the sensor which is used for measure the temperature temperature.Can any body explain that what is  meant by ambient temperature and object temperature?


texts:
I am having a trouble understanding the concept of line to ground faults,and ground in general.

In this simple single phase circuit, does current reach the load and the circuit operates normally? Line touches ground, and neutral is not earthed.

According to what I understand, the voltage in line wire will be zero and voltage source will make neutral wire voltage oscillate between +220 v and -220 v relative to voltage of line wire, and so, the circuit will operate normally.

Does this mean that line to ground fault does not happen in case of unearthed neutral?

In my understanding, when line to ground fault happens, huge short circuit current flows, and that only makes sense if the neutral is earthed because then the line wire and neutral wire will have equal voltages and that,somehow, equates a short circuit across the load, like this:

However is the ground really considered a single node, circuits wise, for us to say that circuits 2 and 3 are the same?

And according to what I researched, line to ground fault can happen even if the neutral is not earthed, how so?

So, in summary, my question(s):

1- Will circuit 1 operate normally? if no, why not?

2- Are circuits 2 and 3 equivalent? how?

3- Can line to ground fault occur in unearthed neutral? if yes, how?


texts:
Recently, the Curiosity rover experienced an internal short in its RTG - which, according to a bunch of sources, was mitigated due to the rover having a 'floating bus' between its wiring and its chassis. When answering this Space.SE question, I ran accross a problem: I have no idea what a floating bus is.

What is it?


texts: What use is the reference node in nodal analysis?

texts:
Rules for identifying  a reference node in a nodal analysis of a circuit include;
Node with largest # of elements
Max # of voltage sources
Node of symmetry

My question is, whats the point?


texts: Will this 4069-based CMOS low frequency oscillator schematic work?

texts:
I'm into building synthesizers from scratch. I've recently built a low frequency oscillator as part of an instrument which works well, based on a TL074 quad op amp. However, it uses a heck of a lot of components and is rather 'clunky' as it requires a great deal of switching to allow 4 different waveforms (rising saw, falling saw, triangle and square).

I've been trying to improve this circuit by cutting down the components required so it can fit on a smaller piece of stripboard.

I found this image on google, with no context or explanation. Caption says it's just 'an idea'.

I have several 4069 chips and would like to try it. Before I commit it to perfboard, can anyone tell me if this schematic will actually work? And if so, what will the P-P amplitude of the waveforms be?


texts: Altium Designer 16: Baked symbols in schematic templates

texts:
I have a small number of template projects, including project file, schematic file, PCB file and Array file. These were created in AD 14, updated to 15 and now 16.

The schematic contains a number of parts that have been dictated for use by our design standard, such as fiducials, template, badmark, BOM entry for PCB, etc. The PCB has the corresponding footprints for these components.

Since moving to AD16, the new project "bakes in" these parts to the template so they are basically pictures. This tricks the difference engine into believing they don't exist, and wipes the parts from the PCB.

Has anyone else experienced this, and is there a new way of making templates, or some setting for shutting off this behaviour?


texts: STM32L MCU - SWD pin on board not matching processor pinout

texts:
I was doing my hardware hack project on an air quality monitoring device which uses STM32L476 processor.

My only experiences with hardware hacking are IPcams or wifi routers with UART consoles available. But, after some probing and trying, I was not able to find a way to interact with my air box. (The USART pins just print out a UUID on boot and then nothing more happens.)

So I reckon my next best bet is those SWD pins. I then proceed to get the datasheet of STM32L476 and encountered this problem.

According to the datasheet, SWDIO and SWCLK corresponds to pin PA13 and PA14 and no other pins has alternative functions to work as SWDIO or SWCLK.

But looking carefully, PA13 and PA14 aren't even connected to those pins marked SWD1 on board.

SWD1 and USART are the only ones that has pinouts so I think they have very high probabilities to be used by developers as debugging ports.  But as far as I know, STM32 chips only need two pins to debug with SWD, and there are 8 pins on board! This circuit just makes no sense to me :((
I'm very new to hardware so I'm not familiar with what hardware developers usually do. Is it common for some pins on board to be marked as A but really worked as B ? Or was it just me making some very stupid mistakes when doing my research ?

Edit:

So after reading all of the comments and answers, I did some test and listed some characteristics of those pins:

I guess I'm good to go and proceed to next step? There's just so much to learn while waiting for my ST link V2 to arrive. Thanks a lot to every one who provided me with utmost kind and help


texts: Identification of filter component in sewing machine foot pedal

texts:
My sewing machine foot pedal appears to short circuit intermittently, causing the sewing machine to be at full power randomly. Given the limited number of components on the PCB, I suspect the component labeled VT1.

On component VT1 it says "50k".

There are three pins for this component. Top and bottom-right are connected to neutral, bottom-left is connected to the wire marked 'L'.

What part is VT1 and what is its purpose in this foot pedal?


texts: Can I use GPIOs to bit-bang in SENT protocol

texts: I want to use a STM8 controller for a project(as I am familiar with micro).This controller gets the data from sensor and process it and sends data to another controller through the SENT/SPC protocol. But issue here is, STM8 doesnot support SENT protocol. I thought to adopt bit bang method and use the GPIO pins to transmit the data, but I am in little confusion whether my decision is right or wrong. Can anyone suggest/help me in this issue? By using bit-bang method may I face any other issues?


texts:
I just used Ohm's law and I was puzzled by this. I am quite new to resistors, and I am only going to use it for an Ionocraft project to reduce the flow of current to ground.

So if I have a 9v battery, and had an impossible LED that could get 1 amp. Which means it would be 9v divided by 1 amp which would ask for 9 ohms of resistance. The problem is, a nine volt battery doesn't have 1 amp of current.

How would this work??? This question has really been distracting me and it would be nice if someone could explain it to me.


texts: Convert momentary button to toggle switch?

texts:
I have this simple circuit (existing, not mine) that you toggle on and off with a simple push button and when you power it off and back on it stays off unless the button is pressed. I want to set this device on a timer but in doing so it never comes back on once the power has been cut. Is there a way to easily change the push button to a switch instead so if the power is killed it comes back on? Maybe another way to accomplish the same end goal?

I can't just hardwire the power as it's powering a PWM pump so I need to power up the circuit.

It's a kids toy, basically a little garden and the power turns on the light/pump.


texts: State machine correct? 4b'1001 sequence detector

texts:
[![enter image description here][1]][1]
Is this a correct state machine correct for detecting the 4 bit sequence 4b'1001? If any bit is out of sequence reset to the initial state. Once the last bit of the sequence is received the output should be set to 1 and return to looking for the first bit and wait for the next "1." *Not using the last 1 as the first 1. If not I need an explanation


texts: What kind of battery to choose for my electrical car project

texts:
I hope that this is the right place to ask this.

I have a small RC car that I opened and added a raspberry pi in.

Now I want to pick a battery. First of all I heard that Lipo batteries are really good. But I can find lipo batteries only with 11.1V, 7.4V and 3.7V.

My driver motor (l298n) can only take 5v to power up my motors, so the 3.7V is too small but the 7.4V is too big.

Out of that I want to power up my raspberry pi board with the same battery. I don't want something too expensive. I want to drive the car on house with a decent speed. Not like that competition cars.

And the last problem is the charging, and protection. I saw that if you are not careful you can damage the battery if you discharge too much or overcharge.

I am not sure if this is a noob question and I need to have physics knowledge but I want some help because I can't spend all my money just to test batteries.


texts:
I don't know if I'm missing a step or a (mathematical) concept is unclear but when I apply time-invariance property:
1) delay original output y(t) by t0, check resulting expression y(t - t0)
2) delay original input x(t) by t0 i.e. x(t - t0), check resulting expression y'(t)

If y(t - t0) = y'(t), then the system is time invariant. Upon performing these operations, I came down the conclusion that the system is time invariant which is not the right answer.


texts:
I plan on making 2 battery packs from rechargeable AA batteries.  Each pack will have 15 AA batteries which will put out 20 Volts to power a meter.

Since I plan on soldering tabs on the batteries, I can not use a standard charger that charges individually.  I will need to make or get a charger that will charge the 20 Volt packs.

How do I go about this?  How many Volts and Amps should the charger put out to charge 15 AA's in series?

And is Over-Charging an issue?  Should there be a controller that cuts power when they are charged?

Thanks!


texts: How to modify zeros and poles in a delta-sigma modulator loop?

texts:
In this specific case, I am modelling a delta-sigma analog-to-digital converter with a basic loop in which the output V is fed back with unity gain to be subtracted from the previously sampled input U (discrete time) and this difference is fed to an integrator modelled with the transfer function:
$$G(z) = \frac{z^{-1}}{1- z^{-1}}$$

Quantization noise is added in form of error E to the output of the integrator, giving the output V. It follows:
$$V(z)=\frac{G(z)}{1+G(z)}U(z)+\frac{1}{1+G(z)}E(z)$$
The complete model, however, should be a third-order system in which the output V is fed back with unity gain twice more so that it is once subtracted from the sampled input in the outer loop, this difference is then integrated and fed to the next loop, in which the fed-back output is subtracted again. This new delta enters the second integrator and the same process repeats once more in the inner loop, where the quantization error is added as described in the first lines above.
In total there will be 2 identical outer loops and a third inner loop where the quantization is added. In total there will be 3 integrators with transfer function G.

Now I'm interested in the Noise Transfer Function: NTF = V / E. According to my computations:

NTF with gain unity in all three feedback paths (alpha, beta and gamma are 1) should be equal to:
$$\text{NTF}(z)=\frac{V(z)}{E(z)}=\frac{1}{G(z)^3+3G(z)^2+3G(z)+1}$$
It follows:
$$\text{NTF}(z)=\frac{(z-1)^3}{(z-1)^3+3(z-1)^2+3(z-1)+1}$$
From here, I would like to do two things:

Replace the poles z1 = 1, z2 = 1 and z3 = 1 of the NTF with different values. In order to do so, I simply introduced a gain factor in the feedback path of each of the three loops (alpha, beta and gamma as above). This will add three coefficients in the denominator that I can play with.

However:

I would also like to replace two of the zeros of the NTF, which are now all equal to 1, with a pair of complex conjugate zeros. This should provide "lower noise around the zeros, at the expense of a less effective shaping at z = 1, thus increasing the usable frequency range".

If I understand correctly, the numerator N(z) of the NTF should be something like this in the end:
$$N(z)=(z-1)(z-e^{jω})(z-e^{-jω})$$
My question is: how do I achieve this? What should I add in the model to shift the zeros slightly away from DC?
Just for information: once I have also obtained a pair of complex conjugate zeros, I should solve an optimization problem to find the optimal position of poles and zeros in the NTF for a determinate quantization noise power. So my humble guess is that ideally I should add something as simple as a gain in the model for the zeros, too, so that can adjust the numerator of the NTF, too, and solve for the optimal zeros within certain boundaries.


texts:
I have heard that applying a strong magnetic field to diesel fuel can positively affect the filtering out of microbial contamination.  Assuming that is true:
I thought it would be simple to wrap a steel pipe with insulated copper wire (I used a 1" pipe, 4" long, with 1 mm2 copper wire, maybe 30 feet.).
I applied a 24 V, 5 A current to it, but did not observe any magnetization whatsoever.
The goal is to apply a strong magnetic field to the liquid in the pipe. So ultimately what is the best way to do that?
But also if MY method is flawed  (which it clearly is.) what variable(s) should I change? I can increase the current, but past 5 amperes makes it a bit too much of a power suck to be practical in my application.


texts: What is the purpose of range gating in a tracking mode of a Radar?

texts:
I am trying to understand what happened in the famous incident where the Patriot failed to intercept a Scud missle because of a software bug.
The reprot can be found here.
Why does the radar need to use range gates during the tracking mode (when it predicts where the target will be).
Why can't the whole beam be processed? I doubt it is processing power limitation since during the search mode the whole beam is processed.


texts: Driving a Strange 12-Pin, 7-Segment, 4-Digit LCD display

texts:
I am putting together a project that requires a 4-digit numeric display and wound up ordering this. Unfortunately, something I completely failed to notice when ordering the LCD was that its pin assignments seem to be... incredibly bizarre. At least to my relative lack of experience.

The LCD provides four "COM" pins (COM0-COM3) and eight additional pins (two per digit). The way the segments are connected to the segments results in each of the COM pins selecting not a digit but rather a (for lack of a better term) row of segments: A and F, B and G, C and E, and D and the decimal point. The eight additional pins then allow you to select one or both of the segments in a row or rows for a given digit.

For instance, if COM1 is active, then I can make visible the E and/or C segments of as many digits as I wish.

The trade off for this is that it is utterly impossible to display any digit besides seven in a single cycle. So in order to use this LCD to display an arbitrary number, it seems that one must update it at four times the rate one otherwise would use.

Bluntly, this seems to me and my inexperienced eyes like a totally pointless convolution. Allocating one pin per anode and one pin per segment would have taken the same number of pins. Updating the LCD at a higher frequency seems like it would increase power usage and wear, if anything.

Perhaps someone more experienced with these sorts of items can shed some light on the matter. Is there any benefit whatsoever to allocating the pins like this?


texts:
I'm having an issue with a transistor.

I'm apply ~3.3v to the base, 4.7v to the collector, but only getting ~2.5v from the emitter. I need to be getting close to the full 4.7v I'm aware there is always some voltage drop across c/e, but 2.2 volts seems excessive. Have I missed something?


texts: I am running a differential pair over cat5 along with 3v3 and Gnd. I have tested the circuit with a 10m cat5 cable and noticed very little ripple looking at the 3v3 supply on a scope. I am unsure about protection for this circuit though. Currently I have a 1uF and 0.1uF filter cap on the 3v3 supply on each end. Is this sufficient? Should I add any other components such as protection diodes, bigger caps or an inductor?


texts: What would I need to open a circuit (a usb cable) for a few seconds, on a given time?

texts:
I have a USB cable connected to a USB modem.

On a specific time of day (say, at midnight - but it should be configurable) I would like to open the circuit for a few seconds.

The result should be equal to me unplugging the device, waiting a few seconds, and plugging it again.

What would I need to make such a circuit? Ideally, the timer should be easy to setup, have a display, and the circuit should be able to draw power from the USB cable, not requiring any form of external power.


texts: best high pass filter topology to extract low V kHz range pulse from noisy 60Hz line voltage before daq

texts:
I need to extract a 1 kHz-10kHz range voltage pulse created by a current pulse I inject on an harmonic rich 60 Hz network and that propagates on it.
The line voltage is 120V AC. harmonics 2 and 3 are significant
The amplitude of the pulsed voltage signal I need to measure is a few V at most. I need the best possible accuracy on the measured pulse voltage.
I am not sure of the best strategy to perform these measurements and seek advice on this.
As of now I plan to use a 24 bit +/- 10v 1MS/s acquisition module. In order not to loose the information contained in the pulse,  my current idea is to design an analog filter with fast transient response so that I don't distort the pulse and  that will remove enough of the line voltage to bring the total signal under 10V peak while amplifying the part above say 500 Hz by a few db so that I can use the full daq capabilities and then use digital processing.
I can calibrate the filter if necessary.
I am not a filter experts and I don't know how to select the best filter topology to achieve these goals.
Any ideas or suggestions will be needed.
Thank you
Regarding safety  and because I cannot use insulating transformer I will use very small fuse.


texts:
Can a TFT Resistive screen be made/used as a multitouch screen?

I have a Android 2.2 SuperPad III tablet which comes with a resistive screen and I am developing an app that needs a few features of a multitouch screen. When testing the tablet for multitouch it fails: it doesn't register 2 different points simultaneously. I know as a fact that Android OS has support for multitouch since I have performed the same tests on a capacitive screen and all tests were successful.

Would it be possible that Android OS disables the multitouch functionality on an resistive screen tablet or is it a hardware limitation? If needed, I don't mind modifying the Android kernel to reflect my needs however I would like to know that the hardware can handle it.


texts:
I'm designing a PCB right now and found out I can save a lot of space using the back of THT elements:

In the picture there's IC1 (ATMega) and LCD. I design only 1-sided PCB for now. IC1 and LCD are put "flipped", so the pins of them are on this side, and the big things (screen, IC1 main body) on the back (easier to solder).

My PCB has limited size and because of that I though of maybe of using the area between pins of IC1 and the whole empty area of the back of LCD. It's a lot of space to use and as you can see with C2 example - easier and shorter.
I know that maybe for ADC elements the problem may happen, because of same GND grid or something like that, but it's not the problem in this situation.

Is is legit to design like that? Are there any problems that might occur? Any opinion appreciated.


texts:
I am trying to design a circuit that measures a sensor that outputs 20nA to 2mA.  I only need to read a sample per second so slow. I need to know what should I look for when I search for opamp that is stable:
EX Specifications:
-Slew rate: 0.5V/µs is that enough or is too much how do find the value I need
-Gain Bandwidth: I know that opamp Band  >> =1/2pi*RFCF (CF=Csensor+Cfeedback+Copamp)
-Zero drift:  Minimizes input offset voltage or I can use any
-Current Input Bias: AS Low as possible
-Voltage Input Offset:  As Low as possible
What else should I look for when I look for the opamp. (Below circuit is for simulation only, actual circuit will have more filtering and gain stages)
I am planning to use different gain depend on the sensor output: 10M-628 ohm


texts: How would I create a voltage doubler and what parts would I need?

texts:
I'd like to make a voltage doubler, I've read up on wikipedia and also here. My issue is that I have DC input and I need DC output, first is this even possible, second, if so the problem I'm having, is that I think I'm in over my head. I don't really understand the diagrams or how to read them (what the symbols mean etc).

My experience with electronics is quite limited, suffice it to say I've put a capacitor over an electric motor to evan out the power on an RC car and used variable resisters to control the speed of a motor. And much of this was cargo-culted from forum posts where individuals made some suggestions and I tried them till something worked.


texts: Low Power SPI Module communication between Microcontrollers

texts:
I have 2 microcontrollers - one is S32K118 and other is S32K142. Both are 64 pins. S32K1xx datasheet
I need communication between the Microcontrollers in SPI Configuration.
Suppose the microcontroller supports 2 LPSPI modules, say LPSPI0, LPSPI1, LPSPI2.
For that, I need to connect the LPSPI0 module pins from one microcontroller to the LPSPI0 module pins in the other microcontroller, right?
Or it doesn't matter if the SPI communication between one microcontroller and the another microcontroller takes places on different SPI modules, like say LPSPI0 in 1st and LPSPI1 in another microcontroller? or LPSPI1 in 1st controller and LPSPI2 in the second controller?
And what about the chip select pin?
Which module should I select for the chip select in SPI communication between the microcontrollers? Why are they 2 modules for chip select? Like, which should I choose based on which will act as the master microcontroller initiating the SPI communication and which microcontroller will act as the slave.

This SPI Communcation is only between the 2 microcontrollers.
Please explain to clear this confusion. Stuck here.
Any recommendations?


texts: can arduino UNO be programmed to measure the analog voltages of 6 resistor ladder network without using switches

texts:
6ea 1k resistors connected in series to +3.3v and Gnd.
Q how can arduino UNO A to D be programmed to measure the analog voltages of  6 resistor ladder network without using switches ?


texts: Both AC and DC motor are inductors, and flyback diodes are used to dissipate residual current when power is disconnected from the motor. Flyback diodes are always present in DC motors, do you need a diode for each of the phases of an AC motor?


texts: FreeDSP (ADAU1701) isn't working - what is the issue?

texts:
I had FreeDSP PCB soldered recently and for the last two days I've been struggling to make it work. FreeDSP basically consists of ADAU1701 DSP, 24LC256 EEPROM, 12 MHz oscillator, IO circuits and Arduino Nano that transfers firmware from PC to EEPROM and vice versa.

The problem is, ADAU1701 seems to ignore the firmware located at the EEPROM and doesn't pass anything to the outputs. I have a multimeter and Hantek 6022be oscilloscope and I'd like to check if anything haven't been burnt during soldering and testing.

What's done so far:

All pins that should be driven to ground of 3.3v are fine.
Current consumption of powered ADAU1701 is 106 mA (quartz enabled) or 60 mA (quartz disabled). The numbers fall in normal range from datasheet.
Firmware can be written to EEPROM and can be read by Nano.

Questions:

Writing to EEPROM was accidentally done with 4V signals instead of 3.3V. 4V is an absolute maximum for IO as per ADAU1701 datasheet. Was it able to damage the DSP?
Pins 13 (1.8V digital supply) and 14 (general purpose IO) were short-circuited for some time. Was it able damage the DSP?
Should I be able to verify the quartz using the oscilloscope? Some signal is present, but it's pretty much random.


texts:
I know that the parasitic capacitance of a chip is pronounced Cdyn.
If I apply on some scenario one the chip which will toggle the all of its transistors with two different voltages, but the frequency is the same, does the Cdyn will be the same?


texts: Detect power outage and disconnect heavy loads from the UPS

texts:
I am looking for a simple system to detect power outage and disconnect heavy loads from the UPS backup to maximize the longevity of the power backup.
The UPS works on a 24-V battery.
The UPS switch over time is <15ms
UPS and main output voltages are 230V
Is there an off the shelf device that I can use to achieve this?
Any circuit diagrams of such a system will be helpful
Thanks in advance.


texts:
Design a state-variable feedback controller to yield a 20.8% overshoot and settling time of 4 seconds for a plant

$$G(s) = \frac{(s+4)}{(s+1)(s+2)(s+5)}$$

I am studying Design Project via State Space (Chapter 12 - Norman Nise - Control System Engineering) and I am very doubts about the specificity development that transfer function.

Flux-flow signal:

and the first state space equation:

when I look the E.E plant represented in cascade, I understand all above development, except for this expression:

$$y = \textbf{C}_z\textbf{z} = [-1\quad 1\quad 0]\textbf{z}$$

My question: Why the output variable y doesn't have the following expression, consider the derivative (s+4) like this:

$$y = z_1(s+4) = \dot{z}_1 + 4z_1 = 4z_1 + z_2$$

OBS.: \$ z_1 \$ and \$ z_2\$ are a variable of state.

$$y = \textbf{C}_z\textbf{z} = [4\quad 1\quad 0]\textbf{z}$$

I really really confused how can they find the -1 that vector row in the first place.

thanks for your help!


texts: Two circuits with different voltages - should I use a transistor or an optocoupler as a switch

texts:
I am doing a project using the output of a Raspberry Pi GPIO pin (3.3V) to power a 12V remote control.

If the two are on different circuits, can I use a transistor to switch on the 12V circuit or do I need to use an optocoupler?

I'm presuming the 3.3V would go into the base and the 12V would be across the optocoupler.

I'm totally new to electronics and have been trying to understand various guides and tutorials and can't work this out.


texts: I am having issues with the emitter resistance during biasing of the transistor. Can someone explain me what's the point of using this resistor? It is getting very not intuitive for me.


texts: I am searching for the datasheet of the TA7634AP

texts:
I am unable to locate the datasheet for the Toshiba TA7634AP.
This is an IC from an Olivetti M24 monitor from 1986.
It should be a horizontal and vertical oscillator meaning that it generates pulses.
Without the datasheet it will be impossible to check if it is at fault.


texts: What can cause these strange AC current and power readings?

texts:
We are attempting to monitor the power usage for a customer using a commercial digital power meter and Rogowski coils.  In one of the panels (3 phase 208/120) the current measurements are very unstable and the a small reverse power is being measured.  The installer is sure that the coils are not reversed.  Using a clamp on meter also shows unstable currents on the three legs.  The currents range for 4A to 14A on L1, 2A to 12A on L2, and 11A to 30A on L3, over the range of seconds.
The panel is powering a kitchen and cafe within a commercial building.  Are there any types of loads that could cause such strange readings?
The wiring in the location could also be an issue.  Are there any wiring mistakes that could cause such strange readings?


texts: signal conditioning 0 to (-40) volt to 0-5 volt, arduino

texts:
I want to convert my 0 to (-40 )v signal to be 0-5 volt so that i can measure it using arduino,

i want to attenuate the signal first by the factor of 8 and then shift it up by the arduino 5 volt. lets say for example if the signal is -20 volt

-20/8 = -2.5 ,,, -2.5+5 =2.5 v

is that possible ?

but then this is how i emplemented it and the voltage is always fixated at 5 V

bellow is my circuit, tell me where did I go wrong


texts: What component can I use to control the brightness of an LED strip?

texts: I know that to adjust the brightness of a single LED, I can control the current using a resistor. What about for a strip of LEDs being fed by a 24V 1.8A power supply? I'd assume that the power being drawn would burn out a single resistor.


texts: Is there any tool to read/write EEPROM of STM32L from the host?

texts:
I'm using STM32L152RTC6 (link to similar MCU line) with a built-in EEPROM (8k).  I wonder if there's any tool that allows me to read/write the EEPROM from the host side, other than programming the MCU using ST library code, i.e.:

STM32L1xx_StdPeriph_Lib_V1.2.0\Project\STM32L1xx_StdPeriph_Examples\FLASH\Data_Program

I did some search online.  For Atmel MCUs, people use avrdude terminal to dump the EEPROM message, but I haven't found a good tool for STMicroelectronics MCU.


texts: Is there a double power switch that guarantees that whenever A is on then B is on too (with slight time margin for safety)?

texts:
I want to completely cut power to a solar charging setup sometimes, to prevent even the background power draw of the solar charge controller itself from consuming battery charge.

Charge controllers are apparently sensitive to when the solar panel is connected but the battery isn't, so I always have to be careful to disconnect the solar panel before the battery, and to always connect the battery before the solar panel.

It would be easier if there were one switch that for both off and on, the circuits are closed and opened in the right order.

Note that if there's some time, probably in milliseconds but preferably less than one second, between the steps that would be best, to let the solar charge controller boot up before the solar panel power comes in.

For my current use case I'm looking at being able to handle up to about 10A.

Is there a name for such a thing?


texts: Selecting a low cost, compact controller/processor for a custom sensor device

texts:
I'm a phd student in aeronautical engineering, and I'm designing a custom sensor device for my research. I've figured out the initial stage of the device, which involves converting the analog signal from my sensor to a digital signal using an ADC. At this stage, I've selected TI's ADS7047 for its compact size, differential input, and high sampling rate (2-3 MSPS). I've attached a very basic diagram of the device and what I am trying to accomplish.
At this stage, I'm trying to learn what to look for in selecting a device to drive the ADC and transmit my data to a wireless receiver. For my application, I am targeting the ability to write and transmit each data point individually, matching the sampling rate of the ADC. At this point, I'm hoping to learn: 1) what type of SoC device would be the best to use for driving the ADC and writing the data to transmit, 2) what parameters or capabilities should I be looking for to achieve the processing speeds that I am targeting (acquire, convert, write, and transmit 2-3 million samples/data points per second), and 3) how can I determine the bit rate required for my application (sending one data point file every 300-500 ns)?


texts:
Im drawing a schematics for a procedure. We are using an anemometer which both outputs current proportional to wind speed. It also has USB output and software to read the speed for users who want to use this way. I can draw the current loops ect. in schematics but I dont know how the current is converted to USB and I also cannot find USB component in LTspice for drawings.

I dont have the detailed data sheet unfortunately. But I only need the "generic name" of the component which converts current readings to USB.

Do you have any idea? Here is the only data they provide:
http://www.fttech.co.uk/ufiles/file/EN_Acu-Test%20Analogue%20Datasheet%202A4204EN.pdf


texts:
I have a One Shot Type Thermostat CS-7TA-35 195 6103 that i've removed from a laser printer's fuser unit.

There was a paper jam within the fuser unit which I assume tripped this "one shot" by metalic strip.

1) when the device reaches its operating temperature, does it act like a conventional fuse and go open circuit? It's open circuit now.

2) Is there a way to reset the device, or do I need a new one?

3) Am I correct that this device will operate at 180 degrees celsius?


texts:
The voltage generated by piezo materials varies but does ampere also vary? Are there any sources where I can find this out?

I might add that I’m not so much at home in the electrical world but I’m trying ;) I’ve got this piezoelectric component that generates up to a 1000 volts but as I understand it volts alone are not enough for measuring output, you need to multiply it with amperes so hence my question, I hope this clarifies a little.

https://www.piceramic.com/en/products/piezoceramic-actuators/patch-transducers/p-876-duraact-patch-transducer-101790/ .. I haven’t an exact requirement as the amount of output will be added to an existing source, the question is more, will the output be enough to be economically interesting.


texts:
Back in the day I built high power push-pull audio amplifiers using a few MOSFETs and a split-rail DC supply (12-0-12v, 16A) - and I fully understood the circuit.

What I’m tying to understand is how one can build an amplifier using only a single rail DC - say I only have Ground and +24v.

How is it possible to drive a speaker IN and OUT without both a positive and negative voltage from a common ground?


texts: VHDL - Quartus II inferring latches on circuit

texts:
My circuit is based on a state-machine. I checked it and it's working fine, the only issue is that it's inferring one latch per flip-flop (The state machine has 11 states and the circuit is one-hot so it has 11 flip-flops, but also 11 unwished latches)
I have checked everything but I cant find what it causing these unexpected latches. My code is in spanish, I think this shouldnt be a problem, but if you need me to translate it, I can do it. The only important note is that "estado" means "state" and "estaprox" means "next state".
Many thanks for your help

library IEEE;
use IEEE.std_logic_1164.all;

entity ej13 is

port (
        clk_i   :   in std_logic;
        y_i :   in std_logic;
        sr_i    :   in std_logic;
        z_o :   out std_logic);

end entity ej13;

architecture EstaNoAsig of ej13 is
    type tipo_estado is (a,b,c,d,e,f,g,h,i,j,k);
    signal estado, estaprox : tipo_estado;
begin

Secuencial:
process (clk_i)
begin
    if rising_edge (clk_i) then
        if  sr_i = '1' then
            estado <= a;
        else
            estado <= estaprox;
        end if;
    end if;
end process Secuencial;

Combinacional:
process (y_i, estado)
begin
    case estado is
        when a =>
            if y_i = '1' then
                estaprox <= c;
                z_o <= '1';
            else
                estaprox <= b;
                z_o <= '0';
            end if;

        when b =>
            if y_i = '1' then
                estaprox <= e;
                z_o <= '1';
            else
                estaprox <= d;
                z_o <= '0';
            end if;

        when c =>
            if y_i = '1' then
                estaprox <= e;
                z_o <= '0';
            else
                estaprox <= d;
                z_o <= '1';
            end if;

        when d =>
            if y_i = '1' then
                estaprox <= g;
                z_o <= '1';
            else
                estaprox <= f;
                z_o <= '0';
            end if;

        when e =>
            if y_i = '1' then
                estaprox <= g;
                z_o <= '0';
            else
                estaprox <= f;
                z_o <= '1';
            end if;

        when f =>
            if y_i = '1' then
                estaprox <= i;
                z_o <= '1';
            else
                estaprox <= h;
                z_o <= '0';
            end if;

        when g =>
            if y_i = '1' then
                estaprox <= i;
                z_o <= '0';
            else
                estaprox <= h;
                z_o <= '1';
            end if;

        when h =>
            if y_i = '1' then
                estaprox <= k;
                z_o <= '1';
            else
                estaprox <= j;
                z_o <= '0';
            end if;

        when i =>
            if y_i = '1' then
                estaprox <= k;
                z_o <= '0';
            else
                estaprox <= j;
                z_o <= '1';
            end if;

        when j =>
            if y_i = '1' then
                estaprox <= a;
                z_o <= '1';
            else
                estaprox <= a;
                z_o <= '0';
            end if;

        when k =>
            if y_i = '1' then
                estaprox <= a;
                z_o <= '0';
            else
                estaprox <= a;
                z_o <= '1';
            end if;

        when others =>
            z_o <= '0';
            estaprox <= a;

    end case;
end process Combinacional;
end architecture EstaNoAsig;


texts: What are some economical ways to get a remote analog video feed?

texts:
I am a computer programmer and I like playing with robots.

But I don't have access to tons of cool toys so I try to make do with what I've got.

The other day I was trying to navigate an R/C car remotely via Skype over Wifi after velcroing my iPhone onto it.

It works well enough indoors. Even then there was a good second or so of latency.

Once I headed outside, though, there were so many frames being dropped I ended up peeking out the windows and cheating.

I realized that sometimes digital technology just isn't the way to go. I would have had much better luck with an analog video feed. I'd get progressively more noise as my signal got weaker, but I wouldn't lose contact for seconds at a time. Yes, Skype probably uses TCP so I've got this entire network stack working against me. But i think the root of the problem goes deeper. I need more robust transmit technology. Packet switched networks ain't gonna cut it.

So I don't know where to start. My guess is it's probably a good idea to use a similar radio signal to the type that was used for television for several decades. But these days, a digital video camera is a lot more capable and compact than... analog video cameras. Is there any reasonably simple way to turn a modern video feed into an analog TV signal? Does such a thing exist? an accessory to plug into a camcorder that produces an analog signal?

I think what I need is a crash course on some slightly obsolete tech. Even HowStuffWorks' articles are too modernized, though it's possible they have a gem explaining how an analog UHF television signal works somewhere that I haven't been able to find.

edit: Okay, this is proving to be pretty informative. I gotta narrow down how to get myself an NTSC transmitter or something like that.

Could somebody help me out? Suggest some equipment I could try to use?

another update: Oooh I found something. Just gotta do a little bit of digging.

So what sortsa hardware do they have in these things? I'd like to get into the guts of it so I can get at the signal so I can amplify it for a range I find suitable for my needs. What methods exist for video feed security? (thats one aspect digital systems have the upper hand on)


texts: Make two Arduinos communicate with electrical signals

texts:
So I need to make two Arduinos communicate. Though, I can't use any clock related system (so no Serial, no I2C...) and so my idea was basically to wire one from another so they could read electrical signals of the other.
So, I plugged a resistor to each (digital) pin from 2 to 6 (that makes five different signals, I don't want to use any signal combination to lower the number of pins needed, it's a thing i'll do later). And, on the other side, I plugged the wires to the same pins, but configured as inputs. To avoid short circuit, I added a 150 ohm resistor between each pin, so I don't destroy anything. Now, my question are :

Is a 150 ohm enough ? I think yeah, but I'm not so sure so I want to verify.
Will my second Arduino read the input as HIGH, since there is a resistor ? Once again, I'd say since the resistance is very low. I of course the Ohm's law (U = RI) but I don't know the amperage going out, so I can't calculate wether or not the voltage will be over 3 volts on the input (3 volts is the minimum to be considered as HIGH by the Arduino).

If anyone could help me on those questions, I'd be extremely recognising.
Thank you in advance, and have a good day


texts: PIC12LF1552 I2C; uC won't exit Start Condition

texts:
So I've been tackling this problem with integrating I2C functionality into my code, which is documented here on StackOverflow: https://stackoverflow.com/questions/25224541/receiving-undefined-symbols-error-with-xc8-concerning-plib-i2c-functions

TLDR: I2C plib didn't work because PIC12 is not a PIC18, I sorted it out by copying the sources and changing the relevant regs, hoping that it would work...

...and now I've run into another stumbling block. When the program tries to open an I2C connection, it seemingly remains stuck on the StartI2C() method which sets SSPCON2bits.SEN high and as it is so commented in the copied sources waits for it to "automatically be cleared by hardware". I'm running this in MPLABX's simulator and this is where its stuck, I have a PICkit3, but it tells me it can't breakpoint anywhere, so thats useless for actually debugging the part, so I'm assuming whats happening in the simulator is exactly whats happening on the part (which is a poor assumption, but I've got nothing else to really rely on right now).

So I'm guessing theres two questions here, should the ported code be compatible as written since it was written for the MSSP module that is probably copied around in many of their parts?

and

If the SSPCON2bits.SEN bit is supposed to be cleared by hardware automatically, why isn't it being cleared?

All of the relevant code concerning my wrappers and setup are in the linked StackOverflow question. All the relevant code concerning Microchip's I2C plib drivers are located in any install of MPLABX with XC8 under /path/to/xc8/install/directory/version/sources/pic18/plib/i2c/i2c_*.c with the header file being inside /path/to/xc8/install/directory/version/include/plib/i2c.h.

UPDATE: All the code

i2c.h - Microchip code modified for PIC12LF1552

pastebin.com/wLUJ0xpH

i2c.c - Microchip code modified for PIC12LF1552

pastebin.com/CTEyZETf

plur_i2c.h - My header file for wrapping Microchip's I2C functions

pastebin.com/HvphrFC8

plur_i2c.c - My source file for wrapping Microchip's I2C functions

pastebin.com/F95Kjrzj

main.c - Main body of code to be executed (not complete)

pastebin.com/NyTkP2pU


texts: How to build a relay switch that resets when power goes out?

texts:
I'm trying to build a kill switch in my car so that when I turn the ignition, a button also has to be held down. When the power goes through, the button can be let go and the system stays closed until the car shuts down, then you have to repeat the process. I came up with this diagram:

https://imgur.com/a/UOysWMc

What kind of parts does it take to build this? I drew logic gates but I have no idea how that translates to real components. Is a button and relay from an electronics store enough? I'm worried about 1) splitting the ignition wire like that and 2) how much power actually loops back, would things over heat?


texts: One single button to wake up a WeMos D1 and put it to sleep

texts:
I am hoping to use a WeMos D1 Mini to control a Raspberry Pi. To save battery, I want to put the microcontroller into deep sleep and wake it up by pressing a button. The same button should be used to activate a method that will put the controller into deep sleep after shutting down the Raspberry Pi.
The thing is that the WeMos wakes up by shortly shorting the RST pin with GND. No problem with a push button. But when the microcontroller is awake, I don't want it to reset if the button is pressed - I rather want to detect the button press. So I am hoping to use two transistors, one NPN and another PNP, so that when I am waiting to wake up, the NPN allows the RST to connect to the button, where the other end is connected to ground via another NPN transistor enabled by the same base signal. When I want to detect a button press, the PNP will then allow the flow between the pins used for button reading.
So all transistors are using the same controller.
Except that it's not working. Last time my WeMos was even getting a bit hot, so I think I am shorting something.
Do I need diodes, for example between the button and the collectors of the two first transistors? Is there a better way to achieve this? (colours mean the wires do not touch)., f


texts: I would like to design a PCB in order to charge a smartphone (1.5 Amps) and in parallel pass through data to a smartphone from an external PCB. This is applied to CDP specifications. I think that the best way it's to provide the appropriate power in the USB port through the Vbus and the smartphone will take the power that it needs. Do I have to use the data buses also or can I charge the phone only through the Vbus in order not to interrupt the pass through mode?


texts: Why doesn't linear resistance scale proportionally with the square of length?

texts: I have an in depth question about basic proportionality of resistance. Why doesn't it scale with the square of length? I ask this because what is causing the potential difference on two leads is charged electric fields at each lead, which decrease with the square of distance.


texts: Will cutting power to a CMOS chip effectively remove it from the circuit?

texts:
I have some designs that require several 4017 ICs to be switched in and out of the circuit intermittently, for counting circuits that require more than 10 outputs.
The way I am currently designing this is to have a master counter, with outputs connected to Vcc of the slave 4017s, to basically remove the chip from the circuit and activate the next one when the count advances.
Will this approach work, or will the chips suck power from another pin?
Also, is there a counter chip similar to the 4017s but with more than 10 outputs?
Thanks!


texts:
I'm wanting to add a battery powered toy to a mains powered pinball table.
The pinball lighting circuit is a 6V AC supply, while the toy is (2 x AAA 1.5V battery) a 3V DC supply - is my understanding.
Is this possible and if so, how do I go about doing it?
Likewise - should there be a similar thread elsewhere.....
Thank you


texts: Problem with Constant Current power supply

texts: I built this schematic recently. The Constant Voltage mode works as a treat, stable as it needs to be. When I insert the LM311 comparator, the circuit works fine for about 30 seconds, then something happens.The comparator switches to pull down the output, however, the positive input has higher voltage on it.It remains in the same state if I short out the input pins to each other. On the OPAmp, the voltage difference on the input pins is really small, but the output is fully on the positive supply level.I can recover the circuit from this state only if I remove the power. I can only think, that the IC-s are not in DC operation anymore, or one or two of them is latching somehow. Sadly, I dont have access to a scope to see what happens, and never had this sort of problem. Can anybody help me what to do with this problem?


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I often find the Arduino 10-bit A/Ds lacking in resolution for my needs.  I much prefer auto-ranging voltmeters.  Can I play the same game?

Can I divide my target voltage range into segments to increase resolution?  How do you protect the inputs from over-voltage?


texts: How to create variable power source circuit from a battery source?

texts:
Basically, I have a high drain battery at 3.7v and I want the output power to be controllable. The circuit I have designed so far is a boost DC-DC converter using a 555 timer to control the switching mosfet, and a homemade inductor, and all the necessary capacitors, resistors, etc.

My issue is determining the output current. The inductor is the component that generates the voltage boost, so how does the design of the inductor affect the current?

How does the total current to the load get determined? If for example, I have a load at 1ohm, and supply voltage (without boost) of 3.7v, then I get an output current of 3.7A. Now if I use the boost circuit, I can get an output of 10v, so is my output current 10A? Do I draw more current from the battery to generate the extra voltage since the battery is drained from both the 1ohm load and the inductor?

Will changing the switching frequency actually modify the output power?
As far as I know, this is how commercial circuits basically work (for ecigarettes/vape mods, etc), is there some other way?


texts: How to model the energy (heat) dissipating from a power resistor?

texts:
The issue I'm currently struggling with is: What is the mathematical relationship between power dissipation and temperature in a resistor?

The project I'm working on is a controller card for a [supercapacitor w/ resistive precharge] in a box.

simulate this circuit – Schematic created using CircuitLab

The resistance and capacitance are known parameters of the system and the voltages are measured.  With this information I can calculate the amount of energy I'm getting ready to dump into the resistors and then decide if I have the thermal overhead to complete that charge cycle:

  if(Predicted_Energy < MAX_ENERGY - Current_Energy)
  {
     charge=1;
     Current_Energy += Predicted_Energy;
  }

Once I finish charging and switch to RUN mode, those resistors are cut out of the circuit.  Now they're just sitting there cooling off... dissipating energy.  How can I take this cooling over time into account with my Current_Energy value?  Is it possible to estimate or assume how much energy is lost given time only? Or would I need to monitor the temperature of the resistor to determine this?


texts: How should I connect a braided shield 2-core cable with a headphone plug with three cores

texts:
I'm a beginner in Electronics.

The cable has two cores and a braided shield. What should I do about the ground?


texts: Appoximation of a transient response of a more complex circuit

texts:
I have a "complicated" circuit that I want to approximate as a simple harmonic oscillator. More info below.

I have a parallel LRC circuit, with some extra input and output load resistors and coupling capacitors. The inductor is really nonlinear (made up of a DC-SQUID). The input voltage consists of a cosine drive with a Gaussian envelope (so it's basically a "short" pulse). I can solve for the output ringdown voltage numerically by directly solving the corresponding differential equations, and everything works fine.

Next, I would like simplify this circuit by writing it in terms of a single degree of freedom. In the weak excitation regime (i.e. low input pulse amplitude), the inductance can be approximated as being linear.

What I've done is this:

assume initially circuit is driven with a drive of frequency \$\omega\$
interpreted all resistors and capacitors as complex frequency dependent impedances
reduced the circuit via standard (series/parallel) rules
arrived at a simple parallel LRC circuit, but now the effective resistance \$R_{\rm eff}\$ and capacitance \$C_{\rm eff}\$ are of course frequency dependent.

Next (and these are the step that may be a bit sketchy):

assumed that the input is no longer a drive of some frequency \$\omega\$, but instead my original "short" pulse.
I looked at the effective resistance \$R_{\rm eff}\$ and capacitance \$C_{\rm eff}\$ as a function of frequency and concluded that these quantities are almost "flat" over the frequency range of the input pulse (which I Fourier transformed to see it in frequency space)
next, set  \$R_{\rm eff}\$ and capacitance \$C_{\rm eff}\$ as constants (i.e. took their values at the central frequency of the input pulse)
Arrive at a harmonic oscillator with constant coefficients driven by a complex input pulse (also frequency dependent, so I also approximate \$\omega\$ to a constant).

The final note is that I am hoping that this simple harmonic oscillator form can be useful to study some other properties of the inductance (which i'm not getting into here).

Questions:

Do you see anything obviously wrong with this approach?
Are items 5-8 unreasonable?
Could I expect the transients of this reduced system to be representative of the full, unsimplified circuit?

thanks!