texts: Old analog oscilloscope (Advance - Gould OS 240) front panel output

texts:
I can't find the exact manual for this pretty simple old oscilloscope (pretty good functionally) - I've found some pretty similar ones, for other models - so I have a couple of questions regarding  the front panel.

There is a small pin labeled Gate o/p. Is this something like a probe callibration output?
Next to it there is a "banana plug" socket input for external trigger (obvious) and ground. What is this ground used for (since there is a mains  ground similar socket at the back panel)?

Thanks in advance

PS. I found this info here https://www.electronicdesign.com/displays/cross-trigger-two-oscilloscopes-create-delayed-sweep-display                                                                     Does it give any help or clue?  Apparently it's a signal. It's a binding post that supplies a positive pulse for the duration of the timebase (according to the similar osc. tektronix's manual). Any idea how it can be used?


texts: Grounding considering signal return path

texts:
I wanted to ask if there is a difference between 2 scenarios on the illustration i've included. If we have 2 or more boards interfacing with each other should we connect every output with it's own signal return path or can we simply ground every board connecting it to a common point and carry the signal with single wires?

It's much more convenient to do it like in scenario B, but i've seen a lot of PCBs where every input/output was a pair of pads: "hot" pad and a grounding pad. Why can't we just use one pad to ground a pcb and use only "hot" wires?


texts: Is there any benefit of making lamps with high wattage LEDs but low wattage driver circuits other than cost?

texts:
Over the past few years I have bought a number of GU10 mains voltage LED bulbs and have generally been disappointed with their brightness. The 9W LED bulbs I bought (supposedly 460-590 Lumen) produce far less light than the 50W Halogen bulbs they replace (specified as 350 Lumen on the box, but I think 800 Lumen would be more typical give 16L/W).

Testing them with my Fluke I found that they draw far less current than I would expect from their "specification", so I have always assumed that the limiting factor was the mains power circuit and that if this circuit were permanently being driven at 100% it would be far more likely to fail than the LEDs themselves.

True to form, over the past few months, two of these 9w (3x3w) bulbs have died, the first almost 12 months to the day from when it was first fitted. I estimate that this bulb was used for approximately 2000 hours over that year, far less than I would expect from a LED bulb. In both cases, the failure manifested as the bulb pulsing light at between 1 and 3 Hz rather than providing continuous illumination.

Opening up one of the failed bulbs, I found that it contained a BP3102 High Precision PSR Constant Current LED Driver and from what I can see of the PCB, the circuit is the pretty much the reference circuit in the data sheet. Given that the data sheet says explicitly that "the output power of system should be less than 5W", I cannot see that it is honest to call this a 12W bulb.

Looking for datasheets for the LED itself, it looks like each of the three LEDs should be putting out 160-190 lm at 3W, so 480-570 lm is pretty close to the specified 460-590 lm), however the power draw suggests that the actual light output at 5W should be more like 266-300 lm, which seems about right.

Putting aside the dishonesty of sellers rating a bulb on the potential output of the LEDs rather than on the actual output of the bulb, I wonder if there might be a technical reason for overrating the LEDs but under rating the power circuit.

There is an obvious cost advantage to the manufacturer to using lower spec parts, but I would have thought that failing to meet the advertised specifications and reduced lifetime would not be considered a good tradeoff.

Similarly, I would have expected that the LEDs would only draw as much power as they need, so overrating the power supply would never be a problem, and the ideal would be for LEDs and power supply to be matched in their power requirement and output.

Is there something I am missing about how a circuit like this should be designed, or is my cynicism just realism?


texts: Is usb relay board safe for high powers?

texts:
I'd like to use this usb device:

https://www.aliexpress.com/item/32956365824.html?spm=a2g0s.8937460.0.0.64552e0ezng2GS

to control 220-240V/AC appliances, drawing around 5A. Specifically, to control my central heating unit, which is not programmable itself.

The device seems easy to program and to wire, however, I am concerned because I found this warning:

"The USB specification has clearly provided guidelines as to how power should be utilized from the USB port, and surging currents produced by high-current mechanical relays is strictly prohibited."

(https://ncd.io/choosing-the-right-usb-relay-controller/#document-5)

I am wondering whether that warning applies to the device above (whose relay's specs can be found here: http://www.circuitbasics.com/wp-content/uploads/2015/11/SRD-05VDC-SL-C-Datasheet.pdf).

Thanks!


texts:
I believe that capacitors are safe to discharge through a short, if

the voltage is not high enough to cause a dangerous spark; and
the energy stored in the capacitor (E = V × Q = V² × C, if I'm not mistaken) which becomes heat almost instantaneously, is not enough to damage the most sensitive parts of the circuit, which are probably the plates inside the capacitor.

What are ballpark figures for V, Q and/or E where it's still safe to short the component leads of electrolytic caps (the common variety, which I believe goes up to 4700µF 50V) saving the time to compute time constants and resistor values?


texts: Optoisolator, did I connected it right? (Arduino Uno)

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Here is my connection for optoisolator,

 2 wires, yellow and red are for AC current.
Other 3 in my arduino, orange pin 2, blue ground and red 5V power.

And diagram.

Datasheet for optoisolator:
http://www.vishay.com/docs/83608/h11aa1.pdf

I am using h11aa1 optoisolator.

Here is my code:

const uint8_t ledPin = 13;                          // Digital output pin that has the on board LED
const uint8_t zeroPin = 2;                          // Digital input pin to which the zero crossing detector is connected

uint8_t zeroCounter = 0;
bool zeroState = 0;
bool ledState = 0;

void setup() {
  Serial.begin(9600);
  pinMode( ledPin , OUTPUT );                       // Enable output driver for LED pin
  pinMode( zeroPin , INPUT );
}

void loop() {

 Serial.println(digitalRead(zeroPin));
  while ( digitalRead(zeroPin) == zeroState ) { // Wait for the state of the zero crossing detector to change
  zeroState != zeroState;
  zeroCounter++;
  if ( zeroCounter == 50 ) {         // Every 50 zero crossings change the LED state
  Serial.println(zeroState);
    digitalWrite( ledPin , ledState );
    zeroCounter = 0;
  }
  };
}

I get always 1 for digitalRead(zeroPin) and because of it Serial.println(zeroState) will never run...

Anyone can help me make this work?


texts: How to explain the behavior of a PNP transistor as a transimpedance amplifier?

texts:
Can anyone explain how Q3 behaves? I mean in a way that: If base of Q3 goes positive ... increases.. ect and if base of Q3 goes negative ... happens and so forth and so on. in that fashion.

I see this PNP in many audio amplifier circuits but hard to visualize its dynamic behavior.


texts: Purpose of voltage amplifier (VAS) in three stage amplifier design

texts: Can someone explain me benefits of this design (found in Douglas Self's book) in comparison with "classic" npn-based long-tailed pair? What second stage actually does?


texts: How to connect two headsets to one android mobile?

texts: How to connect two headsets to one android mobile ? Me and my brother want to hear some songs but we have different headset. Please tell any hardware which is required so that we can connect 2 headsets to same Android mobile.


texts: Reading Battery Voltage - Alternative to Divider + ADC vs. Gas Gauge IC?

texts:
I've been through a few design iterations of an 8 bit MCU, using a voltage divider and ADC to display the battery level of a system.  It works okay, but I've found reading battery voltages requires a bit of acrobatics in the software to average and clean and hide any gremlins from the end user as the batteries age and start acting funky.

I'm loosely aware of gas gauge ICs, and what they do -- also how much they cost... not cheap (well compared to a "free" ADC on your MCU + two resistors for the divider network).

Is anyone aware of any alternative ICs or approaches, that cost less than a gas gauge IC but require a bit less development time than an ADC + Voltage Divider? (I'm thinking like ~$0.10).  I'm seeing low cost gas gauge ICs reading voltages and calculating current, so looks like the most recent approach?

I haven't been around embedded systems very long, so maybe there are some older ICs prior to gas gauge ICs that can get the job done? Some different approach?


texts:
I just bought a cheap 3.5 x 2.8 mm  12 V waterproof white light LED strip. By waterproof I mean that it is covered with silicone all over. The suspicious part is that I cannot see a single SMD resistor in the whole led strip. The style is basic, the strip has cutouts after every three LEDs.
So for driving it with a 12 V 20 Amps power supply, do I need to add a current limiting resistor myself or is there some in-built resistance of the traces used or something that I don't know of?
P.S The small black markings are indeed markings and not SMD resistors soldered onto them.


texts: What is the purpose of diodes after RF power amplifier and before LPF?

texts:
I am planning to build an RF transmitter using an integrated PA module (RA30H1317M1). While studying schematics of similar transceivers, for example IC-2200H (that also has a PA module) I see all typical transmit chain components like the PA, filter, antenna connector, but I don't exactly know the purpose of diodes D27 and D12 (in the middle of the picture).

Are they perhaps to prevent "backward" energy flow reflected from the filter and antenna to prevent intermodulation in the PA? Are they necessary?


texts: Best Way to Get 5V, 2A from a 2-Cell LiPo Battery

texts:
Part of a circuit I'm designing needs to control servo motors rated for 5V. I've measured that they can draw over 1A when active.

The issue is that my circuit is powered by a 2-cell LiPo battery, which I've gathered has a 6V minimum, 8.4V maximum output.

Another part of the circuit uses 3.3V, so I used a switching regulator from 6-to-28V down to 3.3V, and it works perfectly. I thought that a similar component to regulate down to 5V would be about as expensive ($2-$3 ish), but I'm finding on DigiKey that I'm looking at at least $16 per regulator for even a 1A-output 5V regulator, and significantly more for a 2A output.

This is really way too expensive for me, especially since I will have 4+ servos to power. Is there a better way to power servos from a 2-cell LiPo? I would really like to power everything off of one battery, but it seems like I may just need to power the servos with a separate 5V battery (NiCd or other, not sure).

Edit: My search parameters earlier somehow caused me to miss the LM2596, for $2.5. Will this work how I want, if I adjust it to have a 5V output? It seems a little too cheap to be true. :)

Datasheet: http://www.onsemi.com/pub/Collateral/LM2596-D.PDF


texts: Battery Replacement - 3 pin Connector with 2 wire battery

texts:
I need help on using a 10k fixed resistor. I connected the red and black wire but I'm not sure what to do with the white wire. I know that this is for the thermistor. It is not charging if it is not connected. I know that i need to use a resistor but i dont know where exactly to connect it. If you can show a picture on how the wires should be connected, it would be very helpful. Please help! My battery is a 3.7v lipo battery by the way.

I found a similar question and i believe what the person did to resolve the issue should be the one that I need to do. However, i have no idea on how to add the resistor. Link below.

replace 3 wires tablet battery with 2 wires one


texts: ESP32-cam or another camera for shooting at short distances

texts:
I am trying to automate my mechanical water meters. It looks like this:

They are in a place that is difficult to get to, so I thought to place cameras, but distance between the meters and the wall is about 5-7 centimeters (2-2.5 inch). So, camera should be located at this distance in front of meter.
I tried to make a picture with an ESP32-cam with 1600x1200 resolution, placed camera in front of the counter/meter, but I see only circle on photo, the photo is completely blurred, unreadable. It's because of short distance between the camera and the meter.
I also tried to make a photo with my smartphone with 24MP camera, in the same distance. The smartphone blurred photo too, if to don't use it's focus. With manually focused (by tapping on the smartphone screen) camera it's blurred too, but more readable.
So, the question is:
Is it possible to make photos at short distances with ESP32-cam or should I use some other camera for it?
The solution can't be more expensive than $15-20 for each camera, because it's only for hobby, not a commercial project.


texts:
I have a footprint file for a component (.mod). There doesn't seem to be an option to import it though. How to do it?

Also the left-hand menu here doesn't seem to do anything.


texts: I would like to supply two devices from a single power supply.  The devices are connected to the power supply in parallel. Device1 uses a much higher current than device2. The power supply can safely handle the combined current draw.  My question is if say device1 starts to draw a current (i1, which is larger than device2 can handle), will that current i1 be 'pushed' to device2 and damage it?


texts: Big voltage drop on output of voltage regulator on adding load

texts:
I have a voltage regulator that takes in 12V and outputs 5V. However whenever I add a load at the output, the voltage drops from 5V to 2.4V. This is not even a high current load and either way the input voltage is sufficient to handle higher currents and the regulator is rated for 5A output.

The voltage regulator I'm using is the Richtek RT7235GQW. The schematic is based off their eval board here - https://www.richtek.com/assets/evb_file/UG7235GQW-00.pdf

This is my schematic

This is my PCB layout

I can't seem to figure out why this drop is occurring. I have the same voltage regulator and the same circuit on a different board(different design) where this drop doesn't happen on adding a load.

Is there anything wrong with this circuit or layout that could be causing this issue?


texts: Proportional control of 0-12 V DC power source with 0-5 V DC analog signal

texts:
I am taking an instrumentation class and for our final project we are modeling a ventilated barn, to do this we want to vary the speed of a 12 V DC 0.35 Amp fan. To control the fan we are sending a 0-5 VDC analog signal from a DAC (1408 FS PLUS).

Everything that I have found is saying to use a manually controlled potentiometer, i.e variable resistance. But we would like to control the fan's speed with the analog signal since we can control that with our programming.

Our professor has been leading us towards using a power transistor and this seems like it could work for us but my question is when you send the control signal to the transistor is the output proportional to the input signal or do you need to send the full 5 V DC to the transistor to "enable" it.

In the lab we were using a 2N6346 NPN Transistor with a 133 Ohm resistor and it was "sort of" working but we aren't sure if the output is reliable. Any help is appreciated.

Thanks,

Our professor wants us to use the basics to make it work, if it is possible


texts:
This circuit diagram was taken from one of the TI application notes for testing PSRR of LDO.
My question is about configuration of summing op-amp:

What's the need of resistor in between the terminals ?

What's the purpose of ferrite bead at the output of the amplifier ?

Why 100 uF at the input of inverting terminal?
My assumption: Is it to make sure we are feeding only AC signal and no DC offset through this terminal ?

What's the advantage of using current-feedback summing amplifier as opposed to conventional voltage feedback amplifier for testing PSRR.


texts: How to find TPH equivalence to SMD parts

texts: I'm trying to reproduce the following schematic but it's designed with SMD components, I want to build it with the TPH equivalents, the problem is with diodes, I have found S1A is equivalent to 1N4001 diode but what about SS24?


texts: How to calculate wattage required to heat up air inside an enclosure to 50°C?

texts:
I've got a polycarbonate enclosure and I'm going to place a heating element inside it to increase the air temperature in it from room to 50°C, plus a fan to maintain temperature. I need to find out how many watts the heating element needs to provide to heat up the air inside the enclosure so I can buy the right heating element.
The enclosure dimensions are: Length: 160 mm, Width: 120 mm and Height: 140 mm. The calculated wattage does not have to be very accurate as I will get something with slightly higher wattage to compensate if needed. I've found some formulas but they all vary and the answers are different. Ideally I want the air inside the enclosure to reach 50°C in less than a minute but I'd like to know how I can calculate the wattage so can I vary the time and find the most suitable one. Thanks.


texts: Attempting to determine power consumption

texts:
So I am attempting to determine if the battery I choose can power the devices I need. This is my first day doing anything with ohms and current and such. So go easy.

I have:

2000mAh battery

45mA    Bluetooth card

3.9mA   GPS card

2.0mA   IR Thermometer

Now the arduino mini only says that it has a max output of 150mA so I don't know how much it consumes. For this example I am disregarding it because if I am right then I have a ton to spare.

So based on my thought process I think I get 2000mAh/51mA = 39.2 hours?


texts:
The image of the circuit is shown below and it required to find \$V_0\$,

My first attempt at solving this problem is by changing the current source into a voltage source with 1-V and 2k\$\Omega\$ resistance. The fact that the inverting and non-inverting terminals aren't grounded make this problem look difficult.To the point which, I don't know how to proceed with this question or where to start. I would appreciate any help.
Following some thought and another schematic from a hint suggested by Alfred, I produced a schematic representing our work.

And  my solution for the problem is below,
Using node equation at nodes A and B we have,
$$\frac{V_A-V_B}{1k}=-0.5 \text{mA}$$
$$\frac{V_B-(2+V_A)}{1k}=-0.5-x$$
where x is the current that is sent in the output of the op-amp. Using KCL, at the bottom node near the current source we see that the same current that goes through the op-amp also goes through the \$2\text{k}\Omega\$ resistor. Hence, we have,
$$\frac{-V_A}{2k}=x$$
Replacing this in the second equation,
$$\frac{V_B-(2+V_A)}{1k}=-0.5+\frac{V_A}{2k}$$
And and solving the equations yields \$V_A=-2 \text{-V}\$ and \$V_B=-1.5 \text{-V}\$


texts: What happens to ESP32 module IO pins when it is connected to ground but not to power?

texts:
I have a circuit with several modules that share a common ground. One of them is a common ESP32 dev board. It looks that if I connect something to an IO pin of the ESP32 then it pulls it down significantly (from 3V to about 1V) when the ESP is not powered. If I also disconnect the ESP from the common ground then the issue disappears.
I tested with a DMM and there is very high (Mohm) resistance between ground and the pin of the ESP.
Is this normal? What inside the ESP32 causes it?

simulate this circuit – Schematic created using CircuitLab


texts: Where would be the best place to start looking for information on developing a bootloader using 2 microcontrollers for a CubeSat?

texts:
I am an engineering student who has just begun working on a CubeSat project for my design class. We are working on the OBC, specifically looking at developing a bootloader at this time. The OBC components have been selected by previous teams and an outside resource we are having trouble reaching. We have been provided with a prototype board that contains 2 microcontrollers.
Primary MCU: STM32F429ZIT6U
Secondary MCU: STM32F103CBT6
Updates will be sent by UHF and received by the secondary MCU which is supposed to then update the primary, as long as the transmission was successful.  As I mentioned earlier, the resource that previous teams had to help select the components and layout of the board is no longer reachable, so I was hoping I could get some advice/documents to move forward with bootloader development here.  I would also like to note that I am a 3rd year engineering student with limited exposure to programming, as most of our classes use Arduino as an education tool. What I am wondering is:

Is this two-MCU set up necessary? From what I have read both MCU's have an internal bootloader.
Are the internal bootloaders capable of reverting to a previous version of the software if the update is unsuccessful? This is required since we won't have much time for communication with the CubeSat based on our location.
Any advice or resources related to accomplishing this task would be greatly appreciated!

All of my online searches so far have led me to the internal bootloaders being activated through a pushbutton and programs being updated by a computer.
Here are some of the documents I have found regarding the ST internal bootloaders:
STM32 microcontroller system memory boot mode: https://www.st.com/resource/en/application_note/cd00167594-stm32-microcontroller-system-memory-boot-mode-stmicroelectronics.pdf
Secondary MCU starts on page 65, Primary MCU starts on page 153
On-the-fly firmware update for dual bank STM32 microcontrollers:
https://www.st.com/resource/en/application_note/dm00230416-onthefly-firmware-update-for-dual-bank-stm32-microcontrollers-stmicroelectronics.pdf
STM32™ and STM8™ Flash loader demonstrator:
https://www.st.com/resource/en/user_manual/cd00171488-stm32-and-stm8-flash-loader-demonstrator-stmicroelectronics.pdf
Windows API for STMicroelectronics microcontroller bootloaders:
https://docplayer.net/161763432-Um0516-user-manual-windows-api-for-stmicroelectronics-microcontroller-bootloaders-introduction.html
I have pictures of the prototype board and an old block diagram of the OBC if that would be any help to anyone.
Thank you in advance for your time!


texts: Does software exists that will give you the possible schematics of an analog circuit?

texts: Does software, and/or perhaps an actual device, exist that will give you the possible schematics of an analog circuit from measurements of the circuit?


texts:
Now I know in order to have an I2C address reserved for yourself you have to pay the I2C people some money. But I don't want to do this.

I'm asking for advice on what address I should choose for my slave and master MCUs on my project. There will also be an EEPROM on the board. So I will avoid using the address of the EEPROM. I plan for the master to connect to a wide range of sensors, including gyros and accelerometers, and perhaps additional memory devices. Are there any blocks of addresses I should stay clear of? I was thinking of just using 0x00 for the master and 0x01 for the slave, because those seem to be rarely used.

Another question: would it be a bad idea to mix 10-bit devices and 7-bit devices on the same bus? I was considering the possibility of having my MCUs communicate with 10-bit addressing, but only using 7-bit addresses for sensors.


texts: What is the best practice to generate positive and negative voltages to power an OpAmp

texts:
I would like to supply +4.5V & -4.5V to OpAmp using a 9V battery. I have tried using voltage divider which works.
Please suggest if this is the best practice, are there any better ways of doing this.

Note: Output current required is below 100mA.


texts: Is it possible to detect high impedance at FPGA input?

texts:
I am using a FPGA development board which have neither pull-up nor pull-down resister at the input side.

VHDL code that I am developing has to detect either logic zero or logic one and to do respective tasks. But when input is not connected (high impedance state) circuit is behaving abnormally.

Is there is any way by which I can rectify this problem by VHDL programing ?


texts: Having difficulties using a darlington (BD681) to drive a 12V fan from an Arduino

texts:
I'm trying to power a 12v fan using a darlington so I can control the speed from an Arduino. When I wire up as below nothing happens, even though I'm sending a PWM signal:

Circuit diagram http://img809.imageshack.us/img809/5261/wireissue.png

Have I wired up the transistor incorrectly?

Transistor: http://www.bitsbox.co.uk/data/transistor/BD681.pdf


texts: Noise from solid state rectifier in tube amp

texts:
Recently I was talking to a friend about solid state rectifiers in tube amps. He told me that solid state rectifiers induces noise in the power supply, because the breakdown current of the silicon diodes, something like switching spikes.

Is this noise a really concern? How could I reduce, or even eliminate that problem?


texts: Why can't you use a coil to transform 5 volts DC to 12 volts DC?

texts: Why can't you just use a coil transformer, like when you want to get 240 volts out of a car battery instead of a boost converter? I found a thread that sparked my interest - How to transform 5V into 12V?. I want to do a similar thing so I can charge things like a laptop from a portable 5V phone battery pack.


texts: variable inverting op-amp Schmidt trigger

texts: I need to have variable high and low thresholds. Where do I put a variable resistor to get better results?(R1,R2 or R3)


texts:
I have a few differant AC to DC converters and wanted to know a good way to use them to power my breadboard and projects once they make it to strip/protoboard.

One adapter is used for laptops (Part No 608428-003). One is a 6V 500mA that will fit in a 2.1MM jack and another is a 12v 500mA that will fit into a 2.1MM jack. The final one is 6v at 2A and I can't figure out what jack I could use. (Model: DSA-0151A-06A)

So, I obviously can't hook them up straight to the breadboard or project board and get the magic 3.3v, 5v or any other value of volts I need. How would y'all suggest I lower the voltage and power my board?


texts: Can I connect 4 wire and 2 wire RS485 devices on the same network?

texts: If so, how? I have 4 wire and 2 wire devices I would like to connect on the same data line. I know you can convert 4 wire to 2 wire easily at the master, but is it possible farther down the line, say after a string of 4 wire devices?


texts: Implementing a total sum with logic gates

texts:
I'm trying to implement a total sum that looks like this.

TOTAL = TOTAL + INPUT

I'm using binary adders to add and D flip flops to store TOTAL. However, whenever the TOTAL updates, it again updates because the equation is recursive. How can i make it so that whenever i get an INPUT, it only updates TOTAL once. TOTAL and INPUT are both 6 bits and INPUT returns to 0 after any value is passed to it.

Edit: REF are just outputs. The D flip flops are level triggered and are set to 0 at the start.


texts: How can i make a frequency dependent switch?

texts:
Is it possible to make a circuit/switch that turns a relay ON whenever there is a certain RF frequency applied and keeps it OFF for all other frequencies.
The RF signal should not carry any information, just a sine wave.
i have this FreqModulated signal in the order of a few hundred kHz, its more like an FSK signal comprising only two frequencies, and i have two relays, i want to make a circuit in such a way that when the upper freq is being radiated one relay should turn ON, and when the lower frequency comes the other one should turn ON
If it is possible please give a sample circuit diagram


texts:
I am a normal mom who needs to figure out how electricity works. We all know light bulbs create heat and we need that heat to melt a very thin plastic string to move our machine along. The problem that I am having is the rules state "No electric device may have or use an electric potential difference of more than 9 volts. I am pretty sure (if youtube has explained it to me) that I can only use a 9 volt battery to power any electrical currents. I am finding that this is not enough power to heat a light bulb hot enough to melt my string.

So I need help figuring this out. How do I melt a thin plastic string only being able to use a 9 volt battery. I was thinking of making a heating coil, but I don't know how to do that and I don't know how to incorporate that into my rube goldberg machine. Because I don't know how I could activate the coil properly.

So ANY ideas or assistance with this problem would be awesome. Thanks!


texts:
I want to use the sx1276 LORA ic as a node that can transmit and receive at 868MHz. In order to use that band of frequency one has to use Higher frequency rf pins of the chip (rfo_hf and rfi_hf). The image i have attached is from the manufactures design reference. For my purpose I don't need the lower frequency thus I will not be connecting the rfo_lf and rfi_lf. In the image i have attached I have marked on schematic according to my knowledge (I maybe wrong please correct me) what the functions are of each section of the passive components. In order to simplify the design I have choose to use an off the shelf SAW filter rather than building one out of passive components. The off the shelf SAW filter i have choosen has an input and output impedance of 50 ohm. My question is regarding the balun and matching network aspect of the schematic. Are components I have highlighted for the balun and matching network all I need in the design before the SAW filter or will L7 fall away as I will not be using the lower frequency? Do i fit L3? I would like to have the PA_boost connected so I can have a higher transmit power (20dBm).

Any help will be appreciated.


texts: How can an ADC measure below its resolution?

texts:
An ADC's resolution is set by the maximum input voltage divided by 2b where b is the number of bits. In that way, a 16-bit ADC with 20V input can measure a voltage of 20/65536 = 0.3mV (corresponding to the ADC level 0000000000000001). However, I know an ADC can be used to measure voltages down to the ADC's own quantisation noise, which is typically a number more like 5uV.

I guess you could measure a very noisy signal with mean value lower than 0.3mV, as long as you averaged many measurements. Is this true? Does the noise have to be large enough to tip the signal above 0.3mV (in this case) so that the ADC can register a non-zero signal? Does this relate to dithering?


texts: Will having two antennae at the receiver give better reception?

texts: I have a 300mbps router with two antennae (tp-link td-wd8968). I'm building a PC and looking for a wireless network card. I have seen seen cards with a single antenna (150mbps) and cards with two antennae (300mbps); I understand the latter is for 802.11n which has higher data rates, but does it have any affect on the signal range?


texts:
I didn't like this question since it can't be easily answered but perhaps I can rephrase:
"What keeps Embedded from changing languages?"

For instance, we pretty much see C/C++ for embedded (I think i've heard ADA mentioned before too? correct me if Im wrong)

But what exactly keeps the Embedded world from changing languages? Is it just that C is too easy to use or there just isn't really a "need" for a change since C does everything fine?

This has always kinda baffled me, not that im complaining. Since keeping it to a few languages keeps things standardized. But still the question remains.

I realize this is sort of a Subjective question, however My main Question is "Why" and not "IF/WHEN"


texts:
I am working on an audio filter, and my goal is to filter out noise below 90Hz and 20kHz (the range of my speakers). I will have some nearby circuits running at 25 to 30kHz, so I have decided to go with a second order high pass filter to avoid the noise from these circuits. So far, so good. However, when looking at schematics for active, low pass second order filters, I can only find this circuit (and similar variations):

(Source of schematic diagram)

This would be great, except I have read in several places (such as here) that my audio signal would be better if this were inverting. Unfortunately, after playing around with this for awhile and scouring the web, I could not come up with an inverting variation.

So here is my question: Is there a single op amp inverting second order filter, or do I need to choose between this one and cascading two first order filters (and if so, does anyone have opinions on which of the two may be better for audio)?


texts: SIMULINK: The spectrum of the modulated signal remains unchanged despite modification of the modulation index

texts:
I try to implement a frequency modulator.
From what I know, the more I vary the modulation index (which is set by the gain block here,) the more the spectral lines should increase in number.
When I increase the modulation index, the spectrum of my modulated signal does not change. Can someone explain to me why?
My signal (signal modulant) : \$m(t) = 3cos(2 \pi*f_m t ) + 6\$ ,  where \$f_m\$ = 500Hz
Carrier signal (porteuse) : \$p(t) = cos(2\pi*f_c t )\$ , where \$f_c\$ = 6kHz
Sample time  of every signal = 1/1000
Here my schematic diagram:

With a modulation index of 0.2, the spectrum schema gives:

With a modulation index of 0.5, the spectrum schema gives:

Here is the design I have:
Narrow band FM modulation:

The output signal (signal modulé) in the scope gave me :


texts: How to find whether a vehicle turned left or right or didnt turn using gyroscope data

texts:
We are trying trace a vehicle movement when the GPS goes down. We are using accelerometer and gyroscope sensors. And also get the vehicle speed from the OBD (dashboard.) The data will be collected for every second and uploaded to the server for post processing. So it need not be real time. I can calculate the distance covered by the vehicle. And I will try to match the result to the road map that we have already stored in the database for the region we are interested in.

Now I have to determine whether the vehicle made a turn or not at the intersections. I am planning to use the gyroscope reading for this. Can someone point me in the right direction to determine the vehicle turning from Gyroscope (X, Y and Z) values. And also what are the other readings I might need to get this working?


texts: Both describe EOR(XOR) gate - but according to the textbook, it says that Figure 2.17 has two gates in series, while Figure 2.19 has three gates in series. But to my eye, it seems that both have three gates in series! Can anyone explain this? Thanks. Or is textbook's figure somehow wrong? (I heard that the textbook Principles of Computer Hardware has few figure errors in digital logic areas.


texts: Difference between two gain +1 op-amp topologies

texts:
I've got two differential driver circuit designs that take a single ended input and provide as output a buffered pair of +1 and -1 times the input and I'm struggling to understand the difference between the two.
In Circuit A, the inverting input to the bottom op-amp (U104B, configured to have gain +1) is attached to ground via R117. This is the "standard" topology as far as I can tell, and I understand how it works. (Note that the labels appear to be wrong, so the upper op-amp output labelled "Diff Out+" has gain -1 and the lower labelled "Diff Out-" has gain +1.)

In Circuit B on the other hand, the equivalent gain +1 op-amp, U12A (the upper one), has its inverting input connected to the input signal via R41. The non-inverting input is also connected to the input signal directly.

Why might someone connect the inverting input of a gain +1 op-amp to the input signal and not to ground like in the "standard" non-inverting op-amp topology? Lower noise perhaps? Better common mode rejection? (I'm not concerned about the op-amp types nor the extra resistors and capacitors at the output and feedback - just the differences between the inputs in the two circuits).


texts:
I have been looking at AND gates and noticed there are a couple different ways to build them.  I am wonder when each of the circuits is better than the other:

or

Also with the first circuit I am a little confused about how it works.  If x and y are 5v then q3 will turn off.  Why is this?

Also, if X and Y are 0v what prevents the current from just flowing directly from the power source into Z making it 5v?


texts: Is a boot-loader needed to dump the flash memory to RAM? Why?

texts:
When a micro-controller is booting, does it fetch the instructions directly from the flash memory? But sometimes a boot-loader is used.

If so why do we use a boot-loader to dump the flash memory data into RAM?

How can I know whether the micro controller fetches the first boot instructions directly from the flash memory or through RAM?

Edit: My question is about bootloader! This is not duplicate at all.


texts: Plan a circuit to convert a 4 digits binary number to two's complement

texts:
I need to plan a circuit that will convert $$-\{Y_3,Y_2,Y_1,Y_0\}$$
To it's two's complement show
$$\{S_3,S_2,S_1,S_0\}$$

I think the question is undefined well since 0 is not unique and since converting a 4 bits negative number to two's complement requires 5 bits and I only have room for 4 bits.

Is there a way to solve this?


texts:
Very new to audio hardware so please bear with me :) What I wanted to do was make a simple unit that takes a mic input, mixes it with audio playing from the headphone jack of an iPod/iPad/etc and spits it out to a self-amplified speaker.

Modified a circuit I found online to mix the mic with the left channel and have what's in the attached image. I'm just using basic electrolytic caps and 1% resistors.

The issue is that there's a high pitched noise coming out the speaker at all times, and seems to depend on the pot value from the mic preamp. The higher the mic volume, the worse the noise. Cranking the volume down to 0 causes the noise to reduce considerably, but not disappear.

I assume there's some noise being generated somewhere in the preamp stage and being forwarded on. It happens even with the mic disconnected and the closed circuit jack dropping the input to ground.

The OP Amps are RC4580. I started out powering it from a 9V cell running through a MAX1044 to generate the -9V. Figuring power supply noise was a potential culprit, I pulled the MAX1044 out of the equation and used a second 9V cell to generate the -9V rail, with no improvement. In fact, the two new cells I used had slightly higher voltage than the original, so it was even worse to listen to

Sound quality isn't of much concern to me. If I could get something basically tolerable, it would be just fine, but the hiss makes it pretty difficult. Aside from the hiss, though, it does indeed amplify the mic and mix with the audio at appropriate levels.

Any pointers would be much appreciated!

NOTE: Missing feedback resistor on the preamp is 100k, same as the others.

EDIT: Added 0.1uF ceramic bypass caps to + and - inputs on op amps and switched the MAX1044 to another 9V cell and it's reduced the noise a fair bit, but it's still there.


texts: Minimum Switching Frequencies in Boost Converters

texts:
Why are switching frequencies for boost converters above the 100kHz range?

If I understand correctly, as the frequency increases from 100kHz upwards, the ripple current that is created from the inductor decreases, the current change over time decreases in the inductor, and components can be smaller because they don't have to deal with larger (relative) currents. However, they're countered by decreased efficiency from switching losses in the MOSFET, as well as losses from the core of the inductor.

So, given that you can increase efficiency by decreasing frequency, why don't switching frequencies occur in lower ranges; the 100Hz-10kHz range, for example? Is it that the current changes that the inductor has to deal with are too high and the inductor wiring resistive losses starts to dominate as the main source of power loss?


texts: While dealing with my notes on 8255A operation mode (Interfacing) in Mode 0. I came across the statement 'Each port can be programmed in either input mode or output mode where outputs are latched and inputs are not latched.' Which seems confusing. What do  latching mean,  in general language if i were to teach non technical person. Microprocessor: 8255A


texts: Compare three voltages by using comparator

texts:
I am working on a circuit which compares three voltages V(a), V(b) and V(c) by using only op-amps.
To result

If V(a)>V(b)>V(c) , V(output) should be 15v
If V(a)>V(c)>V(b) , V(output) should be 15v

If V(b)>V(a)>V(c) , V(output) should be 10v
If V(b)>V(c)>V(a) , V(output) should be 10v

If V(c)>V(a)>V(b) , V(output) should be 5v
If V(c)>V(b)>V(a) , V(output) should be 5v

This can be done by using transistor and op amps to get lower or higher voltage together but is there solution for that by using just op amps?

edited

With this I can compare three voltages and get the higher or lower voltage.


texts:
I am designing a dirigible, robotic drone. It is basically a polyurethane airship, approx 3.6 m length and 2.1 m diameter.

I am worried about lightnings: as far as I know, a Faraday Cage should be able to protect its interior from external electrostatic fields. Now my question is: a lightning is much more likely to strike on a conductive material mid-air rather than on its surroundings, right? Now, even if the Faraday Cage could protect it from the electrostatic field, there should be a huge amount of energy released in the Faraday Cage due to the Joule effect of the lightning streaming through it, enough energy to melt the structure. A lightning can bring a current up to 100 kA: say I have a wire in copper 5mm in radius and 2 m long to protect it: that lightning could release up to 4.3 MW on that lightning rod!

So I was wondering: is there any other strategy to protect the drone? On example, could it be possible to cover it with some dielectric (is there anything stronger than air?) so that lightning would rather strike somewhere else?


texts:
Background

To kick-start my longstanding ambition of getting back into electronics, I decided to try and make a device that measures the soil moisture of potted plants to determine whether they need to be watered. The aim for the first incarnation is to have a led that shows the plant's current water level (add water is red!), but of course I have wild plans for self-watering plants down the road.

My first stab was based on the Garduino instructable, specifically this circuit here:

It is a simple voltage divider using a known resistor and two copper wire electrodes stuck in the soil as measuring device. The voltage measured at A0 using the ADC on my Teensy++ is proportional to the ratio of the resistances, and I can work back to the actual soil resistance.

However, in practice the soil resistance turned out to be subject to a very large drift. Almost immediately after turning on the device, the measured soil resistance started dropping. (This also happens if you stick a multimeter in the plant.) After a few days of measurement, I could find no usable connection between the measurements and the moisture level. Removing the probe and inspecting it revealed considerable tarnish on the anode. To me, this indicates that some sort of chemical reaction is taking place (electrolysis?). A multimeter measures a voltage differential of a few tens of millivolts: I have turned my plant into a battery!

To avoid this problem I moved to a probe constructed out of stainless steel screws. As they are considerably less reactive than copper, the oxidation should be less of a problem. Also, to avoid "charging" the soil, i have put the voltage divider between two digital output pins of the Teensy. The measurement happens as follows:

Both pins are kept low when no measurement is taking place.
I drive one pin high. I wait one millisecond and I measure the voltage at the center of the divider.
I invert the pin voltages (high<->low), wait one millisecond and measure again. I should now measure the complement of the first measurement.
Both pins are brought low again and the device sleeps until the next measurement.

This does reduce the oxidation problem, but the measured soil resistance still seems to start dropping as soon as I start measuring.

Question

Can anyone recommend a robust method to measure soil moisture?
Can anyone explain what is really going on here?


texts: High voltage power supply and shunt regulator design

texts:
I'm building a high voltage power supply for a tube amplifier preamp and I need some advice.

I need a power supply with a shunt regulator that is rock solid stable and dead quiet and outputs 600v with a maximum of 100ma current draw that will be adjustable down to 2ma.
The next stage of the design requires a stable voltage and the stage will amplify any noise so I need a good design.

This is what I have right now

I don't trust the stability or noise of that series regulator design. After building it in real life it seems to droop a few volts and I'm not sure what to think about the noise.

The resistor in the RC filter is underlined with question marks because I don't know the shunt design or overhead voltage that I will need for it.

Does anyone have any advice on a quality shunt regulator with as low noise as possible?


texts: Connecting RS232 GPS Board to Raspberry Pi

texts:
I purchased a NEO-6M GPS board to connect to my Raspberry Pi, and when I bought it I didn't realize that it was meant for RS-232 communication instead of UART TTL (which I believe is what the Raspberry Pi uses). I found an adapter which I think would work for connecting this. It is a USB to RS232/TTL cable which utilizes a PL2303HX chip. Looking at the datasheet for this chip though, it says it supports "RS232-like" communication, and it looks like it only lists 1.8v-3.3v as the supported I/O voltage range (however I may be reading the wrong value in the datasheet for this). The GPS board that I bought outputs -5.5v to +5.5v though for its I/O. I am confused because it seems like this adapter should work for RS232 communication but the voltages don't seem to match. Would it work or should I find another?
Edit: Here is the PL2303HX datasheet (which is inside the USB to RS232/TTL adapter): https://cdn-shop.adafruit.com/datasheets/PL2303HX.pdf


texts: Choice of material for a cylindrical potentiometer

texts:
I want to sense position along a slightly curved metal rod (length 100mm, diameter 5mm) for a project. For the wiper element, I'll be using steel wire of diameter 0.3mm, the length of which runs perpendicularly along the rod's length. I've tried wire-wound techniques, but they pose issues for my project such as durability and a lack of surface smoothness. I'm thinking of creating a new rod with the same dimensions made out of a material that would be durable enough to withstand heavy usage. I was looking at carbon based plastic materials since they offer high resistance, but am open for advice. I want to be able to mould the material into the shape of the rod in question.

Is this a good way to go, and if yes, what material would suit best?


texts: Using a LM311n in a class D amplifier as comparator

texts:
I'm making a class D amplifier as a school project, and we are currently at a stage where we simply need to add the comparator. But the comparator (LM311n) does not seem to run as intended.

My triangle and audio wave are both lifted above ground and referenced to an artificial ground at 5 V.

The signal we get from the comparator is weird looking:

The triangle wave is running at 250 kHz and the audio is running at around 10 kHz.
Both audio and triangle is running as intended so I figure my problem is with the comparator as the signal is kind of messed up.
Anyone know how I can use the LM311n as a normal comparator to make the PWM signal that drives a speaker? If so I could really use input on how to do so.


texts: Would a charged capacitor react differently to a continuity test than a discharged?

texts: I'm testing my non-reacting circuit with a multimeter, but I don't know if I have to discharge my capacitors first or not. I use two capacitors: 0,1 uF and 560 pF.


texts: How critical is it to declare the manufacturer part number for a component within the BOM?

texts:
I've never seen a BOM that explicitly declares manufacturer part numbers for the components (except the obvious ones, like a microcontroller) in any kind of circuit schematics. According to my knowledge, "if part numbers exactly matches, then datasheet of the parts should exactly match and practical performances might match to datasheet or should perform better."
Lately I'm informed that this is not the case and we should provide a manufacturer part number for every part in the circuit, including resistors, capacitors and such.
I do understand that 555-X would have differences from 555, but shouldn't the exact same component codes be compatible between brands?
If not, how would I declare the minimum requirements for the components? How would a client know which parameters were important during the 555 variant selection? How would that client know why I choose for example TI-555 over the rest of the variants, so how would he or she decide if ST-555 would satisfy the circuit's requirements or not?


texts: Arduino and Display in different rooms, possible?

texts: I only wondering which four pins I have to connect for the LCD4884 from SainSmart, because I want to have Arduino and the LCD in different rooms. Is it possible?


texts: How does a large electric switch different from small?

texts: Why do some electric appliances require to have a large electric switch to turn them on or off? If I use a small switch where a large switch is required, would there be potential possibility of getting a shock? Why?


texts: How to make a dummy load of 1000W - 2000W?

texts:
I need to check a 48V battery with dummy loads of 1000-2000 watts for 5-10 minutes.

Perhaps using Nichrome wire, i can wrap some around a fire brick submerged in plenty of water and adjust the load by changing the length used?


texts: Can an FPGA connected to a CPU via PCIE access peripheral devices?

texts:
Is it possible for an FPGA connected via PCIE to a CPU, to directly access peripherals (USB Ports, data, Ethernet, etc) connected to the same CPU via a chipset? I had an Intel based system in mind, with a x99 motherboard or something equivalent.

If it is possible how would the process be performed (Just rough steps.)?


texts: A simple buffer for a piezoelectric pickup to mixer connection

texts:
so my question is pretty straightforward: what are the ways in which this circuit is likely to fail, and how can I protect against that?

I play music (mandolin and viola) and my instruments have piezoelectric pickups, which sound kind of crap connected directly to a mixer.

I've built this buffer circuit (see image) and it works - my instruments sound significantly better. I intend to build it into a module for my instruments for use while performing live.

It is my impression that, because this circuit is so basic there shouldn't be much that can go wrong. Feel free to disabuse me of this notion - but please explain why as I wish to get a clear understanding of what I'm missing.

EDIT 1: I also attempted to measure the current draw, but it's so low (well under 10mA) that my cheap multimeter couldn't measure it, and the 5V USB power bank I was using to power the circuit kept powering down. For this reason, I presume that the voltage levels will generally remain stable during use ... is that a safe assumption?

EDIT 2: Updated circuit design based on suggestions from @richardthespacecat and @analogsystemsrf

simulate this circuit – Schematic created using CircuitLab


texts:
I'm going to use my Raspberry Pi and Wifi router on my terrace (roof covered, no direct rain, but low temperatures, down to -15 celsius in winter and high humidity are possible) and I need to power the equipment.

I have already one wall socket on terrace, but power supplies I have are designed for indoor-only usage (according to the warning labels.)

Could it be dangerous to use it outside on my terrace?  Can they begin to burn or get shot circuit? Is there any way to protect against this?


texts: Connecting a (small) load cell to Arduino using INA125P

texts:
I want to connect the load cell of my (micro) scale to my Arduino. The scale itself is able to weigh max. 800 grams with an accuracy of 0.1 grams - what I want to weigh are loads up to max. 100 grams, with the same accuracy of 0.1 grams.

I've de-soldered the load cell and attached it to the INA125P amplifier using this setup: http://cdn.instructables.com/FNY/02KS/HFSH4TQO/FNY02KSHFSH4TQO.MEDIUM.jpg

When I try to read values using analogRead(), the scale seems to work - however, the first value that I get from analogRead without any weight on the load cell is around ~480 - when I put 100g weight on it, the value goes up to 866 - and won't go any further, even if I put more than 100g weight on it.

I've tried to replace the 10 Ohm Resistor with a 47 Ohm Resistor. analogRead then returned ~106 as "start value" without a weight on it, and a value of 270 with the 100gram weight on. However, since I want to be able to weigh loads with an accuracy of 0.1 gram, the 47 Ohm resistor doesn't seem a solution to me.

Basically, my question is: Is there a way to get the accuracy that I want? Is there a way to reduce the "start value" of 480 to a value around 10? Since I've nearly no knowledge about electrical engineering, I'd be glad if somebody could help me with a newbie-friendly answer.

Thank you very much in advance.


texts: How to import a library into a Arduino program?

texts:
I have a Arduino program wich make use of the processing library.

The program code starts with

import processing.serial.*;

When I try to compile it with the Arduino compiler it crashes with

'import' does not name a file

The code I want to execute is http://www.instructables.com/id/Controlling-an-RGB-Led-with-Arduino-and-Processing/

I pasted the serial library folder from processing into the same folder as my code. But it still crashes.

Update:
My assumptions were wrong! The code I tried to use was designed for Java and to be used with the Processing IDE not the Arduino IDE. It works fine now with Processing! And the other part of the code works fine with the Arduino IDE :)


texts:
I have a question about the high side driver VN7016AJ for automotive applications, during ISO pulse1 -150 V will be applied at its VCC pin,  I found from the User manual (UM1922) that when -150 V is applied the voltage at different pins of the device but I couldn't quite understand the voltages at (-144 v) at SEn and Faultreset pins
Could someone please explain?

Also I found in the same manual that it says in reverse battery condition, ( pages 18,19 of UM1922) , due to the clamping voltage of internal ESD diodes on logic pins SEn, SEL,IN,Faultreset the voltage is dropping to -10V , I didn't quite exactly what they are taking about , will the diodes clamp any voltage above -10 V to -10V or is it that in the case that they are describing the voltage across the diode be 6v and hence -16+6 = -10V ?


texts: Can I monitor 25A peak to peak sinusoidal current wave precisely with this Hall-Effect Sensor?

texts:
I need to monitor a current on a PCB trace. The current is in sine form and its peak to peak 25A. I need to monitor it very precisely (+/- 50 mA) because I have to issue an interrupt output when the wave is at its peaks (maxima and minima points). Also I need to detect the frequency and issue another interrupt on 50 degree phase. I want to be sure because these chips are very expensive.

I fear of this propagation delay and dynamic response issue:

Sine wave frequency will be varying between 500 Hz and 1 KHz. Can this chip keep up with the trace current in those frequencie and can it tell me real time current level precisely?


texts:
I'm new to electronics and I don't understand why you subtract source voltage by the components recommended voltage, but you just divide by the recommended amps...
Why don't you subtract source amps by recommended amps also?
I may have something totally wrong - like I said im new, but I cannot find this anywhere online... thank you!


texts:
I have drawn a circuit diagram of a power supply for a SIM800C-DS IC from the datasheet but is it right or wrong?

I am confused as it's my first time.

I also want to know where to connect the VDD_EXT pin.


texts: Looking for a 14 pin FFC, FPC connector for 1.8" display with unused space on the sides

texts:
Good evening,

I'm looking for a connector that can house 14-pin connector display.
Problem is that it has some extra space on the side which would not fit into regular connector.

Does anyone knows of the model of this specific connector ?

See images below for the display schematic and image.

Thank you.


texts:
Assume a simple short circuit with the probes on a multimeter at any point along the circuit:

Can we assume that the voltage read will be 0v, as all points along the wire have the same voltage?

If we then add a resistor:

And measure the voltage across the resistor, at which resistance would you register 5v?

How does Ohm's law verify this?


texts:
I would like to measure the amount of power that is delivered by the Sun during the day. I have a nice housing (a waterproof glass hemisphere with aluminium base) from an outdoor IP camera and have been thinking about putting small solar cell in it.

I know I can calculate DC power in Watts as P = UI and knowing the area of the panel, calculate the amount of immediate power that is being delivered to a square meter. (And I would need to know the panel's efficiency.)

Sure enough there are devices to measure power yield of a solar panel, could anyone explain how these operate so that I can build myself one?

Thanks!


texts: What are the differences between Greinacher and Bridge voltage doublers?

texts:
I was reading a wiki article on Voltage doublers, and wondered - what are principal diffirences between two following schemes:

They all share same amount of components, but when and why should be one variant chosen over another?


texts: I have a string of 20 mini Christmas lights (not LED) and I would like to reduce the string of 20 to a string of 2.  Can I put a resistor(s) in the string to avoid the bulbs burning out?


texts: FTDI-based programmer works with ATmega but not ATtiny?

texts:
I'm using an FTDI-based bit-bang programmer for my AVR MCUs with AVRDUDE. It works perfectly with ATmega32A, but does not work with ATtiny45.

The command that I use to try if it works is:

avrdude.exe -c pinb -P ft0 -B 4800 -U lfuse:r:-:h -F

The -c pinb stands for the following config:

miso  = 6;  # DCD
sck   = 5;  # DSR
mosi  = 3;  # CTS
reset = 7;  # RI

For ATmega32A (-p m32) I get:

 ft245r:  bitclk 4800 -> ft baud 2400
avrdude.exe: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude.exe: Device signature = 0x1e9502
avrdude.exe: reading lfuse memory:

Reading | ################################################## | 100% 0.02s

avrdude.exe: writing output file "<stdout>"
0xe4

For ATtiny45 (-p t45) I get:

 ft245r:  bitclk 4800 -> ft baud 2400
avrdude.exe: ft245r_program_enable: failed
avrdude.exe: initialization failed, rc=-1
avrdude.exe: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude.exe: Device signature = 0xffffff
avrdude.exe: Yikes!  Invalid device signature.
avrdude.exe: Expected signature for ATtiny45 is 1E 92 06
avrdude.exe: safemode: lfuse reads as FF
avrdude.exe: safemode: hfuse reads as FF
avrdude.exe: safemode: efuse reads as FF
avrdude.exe: reading lfuse memory:

Reading | ################################################## | 100% 0.02s

avrdude.exe: writing output file "<stdout>"
0xff

avrdude.exe: safemode: lfuse reads as FF
avrdude.exe: safemode: hfuse reads as FF
avrdude.exe: safemode: efuse reads as FF
avrdude.exe: safemode: Fuses OK

avrdude.exe done.  Thank you.

Note that everything is read as 0xFF.

I've already check the wiring multiple times. The MCU is in its stock state, without any firmware or fuse changes. Why doesn't it work?

Edit 1: specifying bitclock/baudrate. As suggested in the comments, I've tried to reduce the communication speed. Unfortunately, the windows version of AVRDUDE 5.3.1 didn't correctly recognize the -B and -b options. So I've compiled the latest AVRDUDE 5.11.1 with ft245r.patch from bug #30559: Ft232 bit-bang support on Ubuntu. Now I'm able to get for example baudrate = 200, but still no success.

Edit 2: voltmetering the wires. As I run AVRDUDE on low speed, I monitor the 4 outputs (MOSI, MISO, SCK, RESET) with a voltmeter. All of them change, except for the MISO wire - it seems to stay on the high level. Probably I have two broken chips?


texts: Safe discharge cut off point for 12v SLI calcium lead acid battery

texts:
I want to make a circuit that cuts off a mains power inverter connected to a vehicle's battery.

I have found, however, SLI batteries come with very sparse specifications. For example, the Varta E43 72Ah.

I wanted to cut off the inverter when the battery approached 40-50% state of charge. Firstly to avoid damaging the battery, and hopefully to leave enough juice for the starter.

I was going to determine the approximate state of charge a point in time by measuring the current draw by the inverter, the voltage across the battery, and the temperature in its vicinity.

But given the lack of battery specs, this is a problem. Given this, I don't even know how to determine the state of charge manually. (So I could then therefore take the battery down to 40% and then profile the battery for V/I characteristics at different temperatures while at this 40% state of charge).

AFAIK, the cells can't be accessed, so I can't even use a hydrometer, not that the specs even give the specific gravity for any state of charge.

Any advice would be great.

Edit: Note to self: calculating the SoC would need to incorporate hysteresis - see image - for example, it is often said that open-circuit voltage is best only used for calculation of SoC if the battery has been at rest for 6-8 hours - "polarisation".


texts:
I have an FPGA (Lattice ICE40UP5K) at hand and need to do some SD card I/O with it. There are tutorials about interfacing with an SD card with an FPGA, but they typically concern with the case where the card is connected directly to FPGA via some soldering work. However, I want to use an SD card adapter (like this one) for more flexibility, and I'm not sure if these tutorials apply to my use case.
In particular, I wonder what do the adapters do besides exposing the pads of SD cards to jumpers? I have tried hunting for the specification for them, but despite their ubiquitousness, I cannot find any spec for these little adapters :(
Here is a photo of my adapter. From the silk print I can tell they probably speak SPI, but can I just treat the adapted SD card like an SPI flash, without worrying about all the nasty details of the SD card specification? While I have learned that SD cards typically support the so-called SPI mode, the linked article also suggested that "The SPI mode is often used in microcontroller systems. With an FPGA, we might be better served with the SD modes". Which mode should I use with an adapter, then?

For your information, the smaller chip labeled U1 has silk print
LVC125A
WA15508
  TXD19
  05D

the larger chip labeled U (which looks like an analog IC judging from its huge pins) has silk print
AMS1117
3.3 XJS68


texts: Issues with PCB exports to Gerber and no/incorrect trace width

texts:
I've been trying to make a double layered PCB for a robotics project for a while now using Autodesk Fusion 360.
It's going to be the control board for the project, containing an ESP32 together with some connectors, voltage regulators and sensors.
I've had a recurring issue that seems to pop up from time to time, and I am trying to understand what is going on, and how to fix it.
From time to time, when making a prototype export for my PCB, I get a message from the manufacturing company (switching between PCBWay and JLCPCB) saying that the trace width is zero/incorrect, usually accompanied with a screenshot from what they see on their end, with all traces showing zero width, or an arbitrary maximum width. Both are obviously incorrect, but I fail to understand what I did wrong.
Things that I have tried:

Check for errors with CRC/ERC and solve them (only 7 accepted errors left, and those are unconnected GND pads for soldering/heat dissipation)
Check for weird bends/shapes in traces and clean them up
Used the Gerber export template provided by both JLCPCB and PCBWay (which can be found on their website)
Tried several custom export formats on my own, of which some worked from time to time (apparently when I left some layers out, it worked all of a sudden)
Check if I comply with manufacturer specifications (min hole side, trace width, trace spacing etc.)

This PCB has had several versions that I could succesfully fabricate, and were completely fine. Then in a next iteration, I would get the same error again, and both JLCPCB and PCBWay could not let me know what was wrong (which is completely valid for the low price they ask for such low volume projects).
I was hoping that someone could help me understand and/or pinpoint a bit more what I am doing wrong, so that I can improve and prevent this from happening in the future.
Some images of the PCB, and what JLCPCB returned on the last image (zero trace width)


texts: What kind of protections are needed to control an AC motor (230 V) using a microcontroller?

texts:
I need some guidance with surge-protection of the SSR and also how to safely bring the motor to stop (since it's an RL load, the inductive current has to die out). I found a schematic online, but have some difficulties understanding it. Please help me understand the 2 points below.

In above figure, input ports are 2 and 3 for the SSR. Ports 6 and 8 are for output, so when SSR is on, there's a short between 6 and 8. When SSR is off, there's an open circuit between 6 and 8.

What I don't understand is the Zs, the surge protection circuit.
When SSR is off, the mains, the motor and Zs are in series. Zs is an
RC circuit in series (this I got from another site where they were talking
of the same circuit). So basically, when SSR is off, we have RLC in
series across mains. How does the motor switch off then? Wouldn't
the mains keep driving the motor?
A motor is an RL load, so once the relay is off there will need to
be an alternative path for the current to die out. I believe
there should be a Resistor in parallel across the motor, for the
inductive energy to dissipate, once the SSR is off.


texts:
I need to sample an analog voltage from a sensor (0-12v) in an environment where large voltage spikes may be induced in the transmission line, what's the best (simple and cheap) method of protecting the ADC input pin of a PICAXE?

FYI: I'm thinking of using a simple voltage divider to reduce voltage range of the sensor, and a TVS to protect the ADC input.


texts: Buffer to have ( 5V-->15V) with DAC conversion

texts:
I'm working on a project of a digital control of a DC/DC converter (DC/DC converter which I need to control with an FPGA). My DC/DC(IGBT) is wired to an ARCAL 2610 driver.

My question is:

My FPGA(DE2 board) has a 5V output but the driver has a 15V input, I know that I need to put a buffer between them (I chose a hex buffer for the simultaneous DAC conversion) but do I need to add an amplifier to get a 15V output for the driver or will the buffer do it in the same time?

Buffer: Texas Instrument CD4049UB


texts:
I need to dimension an SCR crowbar circuit to reach a certain level of protection against overvoltage, without increasing much the complexity of the circuit of my control card. The need is to protect a control card, which is powered through a standard AC/DC power adapter, from the risk of connecting the wrong power supply with higher voltage. The control card runs at 12V and draws circa 12A. The power adapter has several inbuilt protection features such as overcurrent, overload and overvoltage.
The SCR crowbar circuit looks like this

simulate this circuit – Schematic created using CircuitLab

I need to choose the right components in order to make the circuit trigger at a voltage larger than 12V but smaller than 15V. The idea is that the circuit should always trigger when an improper 15V power adapter is connected.

The capacitor C2 is selected to reduce small voltage spikes or noise which may trigger the circuit.

The Zener diode D1 (NEXPERIA BZX384-B13.115) has a Zener voltage of 13V with a tolerance of 2%. Thus, it should be activated at a voltage range of 12,7 - 13,3V

The thrystor SCR1 (WEEN SEMICONDUCTORS BT145-800R.127) has a gate threshold voltage of max 1V and an average load current of 16A (more than enough, 15V PSU can supply 9.6A maximum)

The diode D1 has a load current of 200mA, and this is enough for the gate trigger current of the SCR1 which requires an hold current of 60mA.

The resistor R1 is used to limit the diode D1 current and low enough to limit the risk for improper trigger of SCR1 in case of leakage current from the D1.

When SCR1 triggers, it will short circuit the power supply V1 that will enter in overcurrent mode and will shut down. We do not need any fuse, since the current of the V1 is internally limited at maximum 9.6A for the 15V version.
Do you see any faults or possible problems with this circuit? I would like to keep the cost, complexity and number of components at a minimum, since this will be integrated in an already existing control card.


texts: Converting +/- 10 V sine to 0...3.3 V sine

texts:
I need to convert +/- 10 V sine to 0...3.3 V sine.
I made a circuit from this topic How to change -10;10V sine wave to 0;3.3V dor ADC

The one with two MCP6021's.

The problem is that at some point some irregularities happen

In this spot when I checked with oscilloscope it looked like it's cutting off bottom half of the sine instead of raising it with 1.65 V.

Could anyone explain the issue to me please?

In simulations it works fine, but in reality it doesn't.


texts: What would be the simplest way without using a microcontroller to make a stop light circuit. All it must do is go from Green -> Yellow -> Red.


texts: I'm creating a Nerf gun target with Arduino for my little brother. To detect the impact I was thinking about using piezo's. They would be located on the back of the targets (alimunium plates that do not bend). I'd like to know if it's possible to detect an impact, despite the fact that the material doesn't look like it's vibrating (and assuming that the target can't move freely on impact).


texts: Battery charger output power higher than input?

texts:
i would like to ask about battery charger i saw at work :) the plate on charger says:

Input voltage 3 phase ac

Min 400v
Nominal 400-415v
Max 456v

Input current

20A

Output

110v DC 9kW
28v DC 3kW

Now if we do simple math with no losses input is 9012W. How can be output 12kW?

Or the manufacturer gives these readings as separate? When we charge only one kind of battery?


texts:
I am designing a four layer board in Kicad. The layer stack up is as follows:

SIGNAL
GROUND
POWER (3.3V)
SIGNAL

Now, i want to connect decoupling capacitor to SMD IC's. The decoupling capacitor is placed at the opposite side of the board. So, i am looking to get a via which connects TOP layer (where IC is soldered), POWER Layer and BOTTOM Layer. If it is not possible or it is not a good technique, then how can i connect decoupling caps and IC's Vcc when they are at opposite side of the board.

Should i have copper pour on TOP and BOTTOM layer of the board and should i connect them with GND or Power?


texts: Calculate dead time in synchronous buck converter

texts: How much dead time is required for the switches in synchronous buck converter at a switching frequency let's say 1 kHz. Is there any thumb rule for choosing dead time with respect to the switching frequency?


texts: What is the Effective Resolution of 7135 ADC

texts:
What is the effective resolution of Intersil 7135 based 4.5Digit ADC

when we use a Microcontroller based measurement using the BUSY and STROBE Signals?

datasheet

Data Sheet


texts:
Something really weird happened while working out soundcard issues on my rockmite tonight. While holding two unconnected ends of a 3.5mm cable in each of my hands, the audio signal passed through my body. Is this a thing?

simulate this circuit – Schematic created using CircuitLab

More context:

Something in my mic input was fading all the morse code antenna signals away over ~1s each time I plugged the cable into the soundcard. So I was thinking about how I should attenuate the headphone jack before sending it to my mic port. Then discovered I could use... my body? Each time the rockmite powers on, it sends a welcome message in morse code over the headphone jack. Imagine my surprise when I heard the welcome message coming through my speakers while holding two ends of unconnected wire.

I wanted to eliminate my unshielded wires acting as antennas. I placed the ends close, parallel, and not touching. I could hear the welcome message very faintly. Next, I wrapped my fingers around each of the TRS connectors and powered on the radio. The sound was much louder. Plugging the two wires in together allows louder sound. Also note that the computer is hooked up to mains, but the rockmite is running on batteries an unconnected by wire to any part of the PC.

I can hold two "unconnected" wires in each hand and become part of the circuit just that easily? Why isn't my body insulating the audio signal like it does when working with DC? Or is DC actually passing through me too? Is my whole understanding that the human body insulates <24v wrong?


texts: How to make prototype circuits that include microcontrollers, and avoid breadboard annoyances at high frequencies?

texts:
From my searches of the web ( as well as this question ), I have found that breadboards - like the one on picture - aren't a good idea when your application involves high frequencies.

I am going to start making simple projects using STM32F407VG microcontroller, that can operate at frequency of 168 MHz. Although pin switching won't take place at this maximum frequency, it will still be very high, in orders of tens of MHz I assume. I have STM32F4 Discovery evaluation board, but will connect external circuitry to it as well.

My questions is : how should I build prototype circuits to avoid problems with parasite capacitance / inductance, if using breadboard is a bad idea ? Thank you.


texts: How can I get I1? I tried combining the two 10 ohms resistors on the right and up in parallel but I always end up getting 2A which is a wrong answer.


texts: Good equipments to measure current consumption for IoT devices

texts:
I was asked to bought some equipment to measure the current consumption for the IoT devices. The company is a startup and has a limited budget for this (let's say less than 5k$).

I'm looking for an instrument that can:

Capture the sleep current (around a few uA)
Capture the active current (around a few mA)
Capture the transmiting current (around a few hundred mA)
Can store the recorded samples in file (about 100 millions samples or more). Testing time can last for 1-2 days to estimate the battery life.
Sample rate >= 1 KSamples/s

Would you please suggest me some names (DMM or oscilloscope)? Do I need a current probe for this purpose?


texts:
Question: In the circuit D1 is a large-area, high-current diode whose reverse leakage is independent of applied voltage, while D2 is a much smaller, lower-current diode for which n = 1. At an ambient temperature of 20C, resistor R1 is adjusted to make VR1 = V2 = 520mV. Subsequent measurement indicates that R1 = 520kohms. What do you expect the voltages VR1 and V2 to be at 0C and 40C?

simulate this circuit – Schematic created using CircuitLab

I have some conceptual queries related to the numerical.

The diodes are both OFF. So a reverse leakage current flows through them. My question is what is the implication of providing that D1 is independent of applied voltage?

Another question is that in forward bias the voltage decreases by 2mV per degree rise in temperature. Is this applicable in reverse bias? I haven't found any confirmation nor any denial. The answer however considers a drop, even for reverse bias.

(Note: I solved the question with and without the drop due to temperature increase/decrease and the answer was correct in the first case while it varied from the correct one in the without clause.)

Another question is that does, area difference between diode bring any change other than in its saturation current?

Disclaimer: I know it might feel that these questions (especially the last one) should be asked differently. But to me they seem to be related to the problem at hand. So please excuse that.


texts: How are multiple power sources synchronized in a grid that uses a distribution ring?

texts:
A large distribution grid can work like this. There're several power station each outputting 50 Hz AC. Each power station feeds energy into a substation next to it which raises the voltage and then feeds energy into a powerline and that powerline goes to a substation close to the customers. The deal is customers don't really want to depend on a single station and that single powerline so they've crafted a distribution ring - there's a chain of high voltage substations connected to each other and each power station feeds energy into that ring - each substation in the ring is connected to two of its neighbors and also to the power station. The more advanced design is to have each power station connected to two of those substations via a separate powerline.

Now electricity "moves" at the speed of light which is high but still finite and over the distance of dozens and even hundreds of kilometers the phase difference between the different power stations will be notable and because of that phase difference different power stations should partially cancel each other out.

If several power stations were connected to a single point they could have been synchronized appropriately but in the described setup there's no single point - there're multiple substations separated by long powerlines forming a closed ring and so it looks like something will always be out of phase with something else.

How is synchronization possible in such conditions?


texts: LED matrix dimming: How to control the current in a 12V LED lamp for video lighting?

texts:
I'm trying to dim a 12V LED lamp  (LEDs specification here however schematics have the real values...) I've build for a video lighting application. My initial thought was to use a potentiometer but it seems that the power consumption of the lamp (7.56 W measured with a multimeter)  is to high for a standard potentiometer. Unfortunately I can't found the specification of my Omeg 470 Ohm LIN.A potentiometer so I've tried it and now I think is burnt.

simulate this circuit – Schematic created using CircuitLab

The lamp is for video lighting, I'm using a camera with a 30-60 fps so I don't know if a can use a Pulse-width modulation because I think it can cause a flickering effect in the video. Further more is for a radiometric experiment and I would like to have a stable output but answer for decent result are however welcome. What are the possible alternatives? Is true that:

  LED’s cannot be dimmed using resistive dimming; it will slowly damage the LED’s.

?

Please note:I'm not interested in power consumption, because is not for standard lighting...EDIT: Answers involving Pulse-Width modulation are welcome if they works for this application


texts: Connecting varaible DC to PV input of Solar MPPT inverter

texts:
I have a synchronous alternator with output of 170~220 VAC and 40~60 Hz (1200-1800 RPM). I am designing a system to stabilize my output to 220 VAC and 50 Hz. So I am working on AC-DC converter that can handle my output, but my question: Can I take the converted DC (70 VDC~120 VDC) and connect it to the PV input of solar inverter? Will the inverter accept this?
Here is the inverter I intend to use https://goo.gl/Vb2ybG
My load will be 4 KW max.
Thank you.

Summary of Specs:

Inputs:

Alternator 170~220 VAC and 40~60 Hz, hydraulic oil motor control input, response time and power out (12 KW).
AC-DC  Converter output 70 VDC~120 VDC, Max power ( 5KW )

Outputs:

Load 4kW max for Converter, Current, max( unknown), Pulse load max( unknown),  kVAR load max ( unknown )
%load regulation (unknown)
% speed and phase regulation of alternator ( unknown)
Power factor ( 0.85 )


texts: Does a rail-to-rail input fully-differential amplifier need Common mode feedback at Output nodes?

texts:
I am designing an Op-amp with rail-to-rail inputs and the operation being fully differential in nature. I am trying to understand whether I will still need a CMFB (common-mode feedback) circuit to fix the output nodes to a certain voltage as done generally? I had a perception that I might not need it given the changing ICMR, which should change the natural output node voltages. I am not very clear about it; looking for some inputs on this.
TIA


texts: Accelerometer first-order Markov chain model

texts:
I am trying to implement the algorithm for altitude estimation presented here. In the beginning of section 2.1 the authors present the mathematical model they will be using for the accelerometer. The accelerometer signal is modeled as follows (equation 1.b):

$$s_A = {}^{s}g + {}^{s}a + n_A$$

Where, as far as I understand, it says that the accelerometer signal is the sum of the gravity plus the vehicle acceleration plus noise and that all of these values are expressed in the sensor's frame (left superscript). I think this makes perfect sense

However, just after it they present the actual acceleration model, for which they use a first order Markov chain (equation 2):

$${}^{s}a_t = c_a{}^{s}a_{t-1} + \epsilon_{a, t}$$

I had never before seen the acceleration modeled in this way and my question is: How can I determine the value of the constant \$c_a\$? Is there a standard procedure to do so?

P.S: I don't really know if this is the proper place to ask this question. If it is not I will gladly move it to where it corresponds.


texts: How to measure temporary drop in voltage with meter

texts:
What's the easiest way to measure the period of time between the "peaks" when a 5V DC signal goes from high to low to high?

I'm trying to debug a power-loss problem, and one of the solutions I'm considering is decoupling the power input by adding a capacitor across the VCC and Gnd pins, but I need to know how long the power drop lasts in order to choose an appropriate capacitance.

I have a Fluke multimeter and a DS202 DSO, but I'm not familiar with using either for this type of measurement, nor can I find anything in their manuals that explicitly tell me how to make this type of measurement.


texts: Bandwidth of voltage divider with PMOS switch

texts:
Planning to measure (varying under switching e-bike load) voltage from a battery.

To step down the voltage panning to use a voltage divider and buffer the output to an ADC via an op-amp.

To completely switch off the device when the e-bike controller is off will need to switch off the current through the voltage divider (maybe this is an overkill considering how small the current is (~2mA), the controller's quiescent current is probably greater).

Planning to switch the divider with a PMOS.

How do I calculate the bandwidth of the divider + PMOS?

I suppose I should use Rds_on of the PMOS and Cin and Cout of the PMOS to get an equivalent circuit?

I first thought I would represent the PMOS as Rds_on in parallel with Cgs but I'm looking at PMOS datasheets and they only give Cin and Cout.

simulate this circuit – Schematic created using CircuitLab


texts:
I had a board with ATMEGA16 (SMD package) micro controller and I had to program through ICSP and it was working fine. Later I needed to make some changes on the board. So I designed a new board and transferred all the components to the new board. Now I am using the same ICSP programming technique but it does not read micro controller.

Could soldering and desoldering the IC with Hot blower be the problem? I soldered, de-soldered, soldered again.


texts:
From specs of MCP23008:

Maximum output current sunk by any output pin is 25 mA.
Output High-Voltage is VDD-0.7, which is 4.3 V in my case.

From specs of G6K-2F-Y:

Rated current (mA) is 21.1 mA
Must operate voltage (V) 80% of max, which is 4 V.
Coil resistance (Ω) is 237 Ohm (measured actual is 245 Ohm).

I am planning to use 1 relay connected from GPIO to GND.

So my calculations gave me 18.1 mA using +4.3 V as described per datasheet which is more than 25% max current from the specs.

Is it safe to use that design?
If it is not is there anything else with 5V power supply and I2C interface?

Updated schematic:

I am planning to use internal pull-up resistor to keep p-channel mosfet closed.


texts:
I have two questions.

Firstly, I am trying to make a 4 bit counter on Vivado 2014.3. I have realized that when i tried to simulate the VHDL code, the "Run Post-Synthesis Functional Simulation" and "Run Post-Synthesis Timing Simulation" options are disabled. Do you have any idea to enable them or is this a normal situation? I have shown below.

My second question is related to that when i am trying to add source, the "Next" button is disabled also. Do you have an idea about this or is it a normal situation. I have shown below.

Thank you.


texts: With shielded twisted pair cable, do you ground one end, both ends, or neither ends of the shield

texts:
I've got a project coming up that's to be doing RS-485 communications over shielded twisted pair cable.  The project will involve cable length runs of many 10s of ft and the cables will probably have to be laid in a single conduit containing 36VDC wiring to motors.  It is unlikely the motor power cable will have a shield.

Regarding the shield in the twisted pair cable, should it be tied to ground at one end, both ends or not at all?  What practical difference with this make?

Then if tied to ground, should it be to the board's electrical ground or the chassis earth?


texts:
How are IR thermal-vision devices able to present us with "invisible" imagery in such a way that we can actually interpret it?

What I'm really trying to wrap my head around is:

How a sensor can "see" colours that I can't. (I understand it's probably like trying to explain colour to somebody born without sight).
How it can "pitch-shift" to a visible wavelength/frequency. (I understand that terminology is probably incorrect when talking about light as opposed to sound, but you get the idea).
Not to mention, in some situations, it seems to have this uncanny ability to "see through" solid, opaque materials & detect objects obscured by obstacles etc. (Like military & DEA aerial surveillance, for example).


texts:
Apologies for what is a probably an easy question but I can't wrap my head around calculating the battery size that I need. I have a circuit with total power of 2.754W and current of 1.32A.

I am interested in calculating how much capacity (in mAh I assume) a battery would need to have to power this circuit for an hour.


texts: How has this Daikin control signal been encoded?

texts:
I just installed a Daikin split system (AC/Heat Pump) and would like to control it remotely. There are similar units available which can be controlled with an IR remote, but mine does not support this option. The only way to control it is to use their thermostat device which uses an unknown protocol to send commands to the indoor and outdoor units.

Here are the model numbers for the components in the system:
Indoor Unit - FCQ18PAVJU
Outdoor Unit - RZQ18PVJU9
Remote Control - BRC1E72

The remote controller is powered and transmits data over the two wire cable that connects it to the indoor unit.

The system supports a second controller as a slave, so the ultimate goal is to create a circuit to act as the secondary controller which will interface with a home automation system.

I have sampled the signal with an oscilloscope to see what's going on, but I'm not sure how to proceed with decoding the format.

Partial Zoom (One Wire)

The signal has a DC offset which is mirrored by the voltage on the other wire. The sum of the voltages on the two wires is always exactly zero. On the small scale, it is sinusoidal. There are regular fluctuations in amplitude, but I'm not seeing a bit pattern. Maybe it is frequency encoded.

See the full 2.4 second capture here in .csv format:


texts: CAN Bus: Nodes powered by different Potential Sources

texts:
There was one similar question asked in 2018 but there was detail lacking. So here goes:
I have an engine running J1919 CAN bus about 15m away from an Engine Info display that receives CAN-bus data. Both use J1939. The CAN lines are 'CAN_H', 'CAN_L', and 'CAN_SHIELD'
The engine is powered from a different battery than the display. These two batteries aren't always connected, hence the question asking about nodes being on a different potential source. The batteries are both 24V
The 0V rail however is common between all devices and negative battery terminals.
The only useful info I could find is from Wikipedia - there is a paragraph on ISO 11898-2: That the transceivers are isolated from the node hosts (I assume both are in the 'node' device) and a node has its own linear regulator that draws from the 'universal supply bus'.
Essentially I'm asking whether the transceiver at a node is completely isolated from the rest of the node, so the supply voltage source to the actual node device (e.g. engine display or engine) does not matter.
Or is there a direct electrical connection when the bus is driven and I have to galvanically isolate two can-bus segments with a suitable repeater.
Thank you
Edit 1: Display model is the Murcal PV101-C from Murphy. It doesn't mention anything on requiring/omitting isolation.


texts: Mixing 2v and 3V LED's and calculating resistors

texts:
Are series groups in parallel better than strictly parallel with a resister on each leg? And for parallel do I calculate Ω just for each voltage LED or do I need to somehow do a calculation that takes into account the total number of LED's and their different voltage? But then what do I do for groups in series in parallel?

So I have 8x 2v LED's each with a 360Ω resistor and 3x 3v LED's each with a 300Ω resistor, all in parallel, powered by a 9v battery. Is this the best way to do this to get the most brightness out of all the LED's, or is there a better way? See diagram directly below.

simulate this circuit – Schematic created using CircuitLab

Or would it better to wire them in series groups, in parallel. For instance the 3x 3v with a 1Ω resistor in one series group, in parallel with 2 more series groups each with 4x 2v LED, and a 56Ω resistor in both series groups?   So that would make 3 series groups wired together in parallel. Does this math add up for my resistors? See diagram below.

simulate this circuit

Which makes the most sense? Is this resistor math correct? And which is best for brightness? Thank you!


texts: Can I overwrite a single byte in AT26DF081A Flash / SST25VF080B Flash?

texts:
Is there any method to rewrite a single byte memory without erasing 4KB block?
I am keeping address table in one 4KB block.I need to update adresses occasionally.
Do I have to copy all addresses to RAM for modifying one address?


texts: How to remove energy from inductor using semiconductors?

texts:
So I have this coil and I'm driving dc current through it. This coil has inductance and thus stores energy from the dc current.

I have to remove this energy before I can change the polarity of my h-bridge to prevent dangerous voltage rises.
How can I efficiently remove this stored energy from the coil immediately after it has been disconnected from the current source?
Would just using a bipolar capacitor in series with small resistor and paraller with the coil like this?

simulate this circuit – Schematic created using CircuitLab


texts: Does "USB FS PHY / USB HS ULPI" imply double usb capabilities when using an external USB PHY?

texts:
Some microcontrollers, for example the common STM32 line, claim USB capabilities along these lines:

USB 2.0 OTG HS, that is, USB 2.0 FS/HS device/host/OTG controller, integrating the transceivers for full-speed operation, and featuring an ULPI for high-speed operation: an external PHY device connected to the device is required.

From: Part 2, https://www.st.com/resource/en/application_note/dm00296349-usb-hardware-and-pcb-guidelines-using-stm32-mcus-stmicroelectronics.pdf
Does that mean there is one USB controller, connected to a FS PHY and with the capabilities(/pins, ULPI) to connect to a HS PHY (one or the other), or does that mean there's one standalone controller+PHY couple capped at full speed and something else entirely that would manage an external PHY, which would mean double USB capabilities when using an external PHY ?
The wording of that resource makes me believe the former, but datasheet feature summaries have me believe the latter:

Advanced connectivity

USB 2.0 full-speed device/host/OTG controller with on-chip PHY
USB 2.0 high-speed/full-speed device/host/OTG controller with dedicated DMA, on-chip full-speed PHY and on-chip Hi-speed PHY or ULPI depending on the part number

This question Connecting two USB DP/DM also leaves me unsure: "The only time the FS port will be used is during dfu where the ulpi won't be working." ?
I'd love a clarification. Hopefully the underlying concepts aren't STM32 specific.


texts: NO Relay Triggered By a Proximity Switch. I'm ignorant, don't know what to look for

texts:
I'm asking for help after spending a couple of hours trying to learn the proper vocabulary. Bottom line is a KISS 24v dc powered NO switch triggered closed by a 3 wire proximity switch. Or do I need a four wire? I don't think PNP or NPN matters for this application.

I'm setting up a Variable Frequency Drive for a small engine lathe. The stop circuit is closed fail-safe. I have a simple series circuit through two emergency stop NC SPST switches. I want to add a proximity switch so the circuit is open unless the chuck key is in the holder.

I know how to use a SPST NO micro switch, but that brings on other design challenges I'd rather avoid. I have 24v DC available to power a relay of "some type." But I have no idea what to look for. As KISS as possible, trying to avoid having to create some kind of an Arduino board etc.

TIA. I volunteer teach bicycle maintenance at a local co-op, was trained in the late 70's as an aircraft mechanic. I generally don't have much trouble with simple circuits. But I don't think I'll ever be much good at electronics.

Ron


texts: Programming external ATmega328 with an Arduino SMD edition?

texts:
I have an Arduino SMD board and an external ATmega328 chip (with the Arduino Bootloader installed, from Sparkfun). I was wondering if I could program the external 328 with my SMD board as the instructions usually say to remove the processor from the Arduino board if there is one.

I've noticed if there were cables attached to the Serial pins in the SMD board, that the SMD would not program... Could I connect those right on over to the 328?

Thanks.


texts: Position components in KiCad for a test rig

texts:
I'm designing a test rig for a product. There's a number of test pads and a power connector on the PCB, which I want to match up with a tester device, i.e. the tester PCB should have pogo pins and the mating power connector in matching places.
The question: given the PCB of the product, how do I export from KiCad, for example, a .dxf such that it has only a few of the components? I could simply export the whole PCB as .dxf and import that to the user.dwgs layer in the tester PCB, but this will have a lot of visual noise as all components are visible. Is there a way I could export only the few selected components (test pads and power connector), or perhaps some other easy way to guarantee that the tester PCB will match with the testee.


texts: Correct way to add High Side transistor to circuit with higher VCC than MCU?

texts:
I want to replace a physical N.O. switch with a microcontroller controlled transistor. The MCU is a ~3.3v MSP430. Since this is high side, I know I need a PNP transistor, and since the voltages are different, I need a way to connect the two.

simulate this circuit – Schematic created using CircuitLab

I thought of using either a Sziklai Pair or a modified inverting npn/pnp pair.

simulate this circuit

Is there a practical difference between the two? And is there any significant (Greater than 1mA) current draw?

As a note, if it is important, the point marked "?" at the PNP's collector, can be tied to the 12v source. Would this be an issue? And I will only need to enable the pair for under 0.5 Seconds, long enough to turn the relay on (typically 10mS??).