texts:
I am trying to use PCA9539 as an IOexpander for my project. I have a STM32F103 connected to PCA9539 via I2C.
The problem I have is to write into PCA9539. Based on the datasheet I should to send (1) address (2) command byte (3 and 4) data bytes via I2C. When I check the I2C bus lines with oscilloscope, I see the micro only sends 2 bytes after address byte. i.e. the last byte wont be send.
The PCA9539 sends the ACK.

I use atollic and stm32cubeMX

Here is my code:

HAL_GPIO_WritePin(GPIOF,I2C2_RST_Pin,'1');
unsigned char I2C_2_buffer[8];
I2C_2_buffer[0]=0x00; //command byte
I2C_2_buffer[1]=0x50;
I2C_2_buffer[2]=0x55;
I2C_2_buffer[3]=0x00;
  /* USER CODE BEGIN WHILE */
  while (1)
  {
        /* USER CODE END WHILE */
          HAL_Delay(4000);
          HAL_GPIO_TogglePin(GPIOD,LED0_Pin);
              HAL_I2C_Master_Transmit(&hi2c2,0x76<<1,I2C_2_buffer,4,1000);
              HAL_Delay(1000);
  }
.......
.......
.......
.......
.......
.......
static void MX_I2C2_Init(void)
{
  /* USER CODE BEGIN I2C2_Init 0 */
  /* USER CODE END I2C2_Init 0 */
  /* USER CODE BEGIN I2C2_Init 1 */
  /* USER CODE END I2C2_Init 1 */
  hi2c2.Instance = I2C2;
  hi2c2.Init.ClockSpeed = 100000;
  hi2c2.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c2.Init.OwnAddress1 = 0;
  hi2c2.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c2.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c2.Init.OwnAddress2 = 0;
  hi2c2.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c2.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2C2_Init 2 */
  /* USER CODE END I2C2_Init 2 */
}


texts:
I have a three phase 750 kVA and a 132 kV generator in my factory. I need to buy the lead acid batteries for generator starter. I know that the generator starter needs 24V DC supply.
What ampere hour (Ah) battery do I need for the starters respectively. What are the calculations or thumb rule for its sizing, and what factors need to be considered for sizing batteries?


texts:
I have been reading about the Delta-Wye and Wye-Delta transforms for resistors, and I was curious as to how the equations for the Delta-Wye and Wye-Delta transforms are formed. I managed to isolate the variables for \$R_a\$, \$R_b\$, and \$R_c\$ (for here, in terms of \$R_{ab}\$, \$R_{ac}\$, \$R_{bc}\$, but I am unable isolate \$R_{ab}\$, \$R_{bc}\$, and \$R_{ac}\$ in terms of \$R_a\$, \$R_b\$, and \$R_c\$. I guess my question is how, without looking at the answer, one is able to derive the equations for the Wye-Delta transform.
Thanks.

EDIT: I guess this is more of a math question than a EE question, but I was also wondering if I'm looking at the problem incorrectly. For Delta-Wye transforms, I calculated resistance from A to B and formulated the equation

\$R_a+R_b=R_{ab}\dfrac{R_{ac}+R_{bc}}{R_{ab}+R_{bc}+R_{ac}}\$

Similarily I calculated resistance from B to C as

\$R_b+R_c=R_{bc}\dfrac{R_{ab}+R_{ac}}{R_{ab}+R_{bc}+R_{ac}} \$,

and resistance from A to C as

\$R_a+R_c=R_{ac}\dfrac{R_{ab}+R_{bc}}{R_{ab}+R_{bc}+R_{ac}} \$

I then added up all three equations and divided by two.
\$R_a+R_b+R_c=\dfrac{R_{ab}R_{bc}+R_{ab}R_{ac}+R_{ac}R_{bc}}{R_{ab}+R_{bc}+R_{ac}} \$

To find the individual \$R_a\$, \$R_b\$, and \$R_c\$, I just subtracted the last equation with the first three one at a time.
The problem is I can't easily isolate \$R_{ab}\$, \$R_{bc}\$, and \$R_{ac}\$ - The Wye-Delta transform equations seem a lot harder to derive.


texts: L298N shield gives relatively low ouput voltage and current

texts:
I am using a L298N shield together with an Arduino to drive a 42mm 2 phases bipolar stepper motor. The driving voltage for the motor is 12V and the logic voltage for Arduino and the L298N shield is 5V.

Everything seems work fine, the stepper motor moves under control without losing steps. However, when I try to measure the voltage across and current through one phase of the stepper motor, I find that the voltage is just about 2.4V and the current is just about 0.075A, which is far from the specified phase voltage and current rating (12V, 0.4A / phase) of the motor.

I want to know that is this a normal case for a L298N shield? Does the L298N have a relatively low efficiency?

If I increase the driving voltage for the motor to 24V / 36V, would this help to increase the output voltage of the L298N shield? But would this put the L298N to a even lower efficiency?

Are there better ways to put higher voltage and current to a stepper motor?


texts:
I am designing motherboard for my preamplifier project and I want to setup PCB as follows:

1st layer will contain digital and analog power supply
2nd layer will be used for digital connections
3rd layer will be used for analog (audio) connections
4th layer will be used for digital and analog ground plane

What is the Eagle Design Rule Setup for such a board?


texts: Use ancient Altera MAX II board in modern environment

texts:
Years ago (in 2004) my university got an Altera MAX-II devboard, but nobody used it. Now it's me who must teach students FPGA programming, but I still cannot get the board programmed. I faced the following issues, in order:

The board comes with ByteBlaster LPT programmer, but I have no LPT on my laptop. Is there a way I can make USB Blaster working with this board?
Okay, I found a computer with LPT, and installed modern Quartuas II 14.1 software on it. I was able to examine firmware from FPGA using ByteBlaster cable, but not to program it. Unfortunately, 14.1  supports EMP1270F256C5 chip only while my board has EMP1270F256C5ES (that stands for "engineering sample" which is kind of beta-version of the production chip); POF files for these chips are incompatible. Can I somehow install support for my old chip in modern Quartus?


texts: LM35 max input current - I have a wrong output from the sensor

texts:
I’m currently doing a small project. I’m trying to make my first pcb.

That’s for a light I made.

But the LM35DZ outputs a wrong voltage.

My LM35 puts out 4.6V instead of 380mV.

With a 12V - 2A power supply.

With the datasheet I can’t find the maximum input current.

Do you have an idea?

This is my circuit:

Datasheet : https://www.mouser.fr/ProductDetail/Texas-Instruments/LM35DZ-NOPB?qs=QbsRYf82W3F5RpWTxhXHxA%3D%3D

The component is wired to the CN1 jst

R6 : 47 ohm
R5 : 330 ohm

With a 3,3V linear regulator.


texts: What are the "blind spots" of the Ebers-Moll bipolar junction transistor model?

texts:
I saw this sentence from one of @Dave's excellent answers:

  If the collector is open-circuit, all of this current flows out the
  base connection. But as long as there's at least a small positive bias
  on the collector-base junction, most of the current is diverted to the
  collector and only a small fraction remains to flow out of the base.

Although I can understand why it's happening, it seems that the Ebers-Moll equations can't predict this, which really concerns me. I want to know what else can't the EM model explain, so that I won't fall into the pit when facing such situations.

As I know so far, "such situations" include

High frequency
\$V_{bc}=0\$
Early effect

Any supplements?


texts: LED bulb can not start properly (BP2832 based)

texts:
I bought several LED bulbs about 2 years ago, and now before turn LEDs steady on, some of them flash for some time. Frequency of flashing may differ from bulb to bulb. After some time flashing, they turn LEDs steady.

Here's the device it (supposed) to use: BP2832, but datasheet shows BP2832A chip, while my bulbs use chip without A code.

Interestingly, I opened one of bulbs, and drew its circuit diagram, and it differs with datasheet. I hardly believe that adding A code will change pin assignment, and think there's mistake in datasheet. Edit: datasheet in Chinese language shows correct pin assignment!

So here's the actual circuit:

(sorry for childish drawing, I want to show differences with typical circuit shown in datasheet). "+" means two resistors in series, "|" means two resistors in parallel.

Here's the board from both sides:

Nothing really damaged, the only green plastic coating torn off one of the capacitors, and big resistors (15R+15R) become kind of grayish because of heating of the bulb.

If you came across this "blinking" issue, or even had been dealing with this buck LED driver, please share what do you think is the cause of issue and what is possible order of replacement.

Thank you!

Update: here're caps

400 V caps are 105 degrees C rated, 50 V is 125 C rated.
As Spehro reasonably noticed, I did mistake in 50 V cap value - it is 22 uF.

I do not have equipment to measure capacitance or ESR, I will just look for replacement.

To be continued...

Update: Here's the follow up question with the bulb redesign.


texts: Why do some toggle switches have terminals of different color?

texts:
I sometimes see three terminal rocker/toggle switches, and one terminal is a different color than the other two.

Here is an example:

(Image from ebay.com)

What does the colored terminal indicate?


texts:
I recently built a HV power supply, as per the link (using a pencil ignition coil).  However, I used a capacitor of around 5nf, which meant the supply did not work.  The capacitor reduced the amps too much, and I did not get a plasma stream as a result.  My questions are,

would this have damaged the ignition coil in any way?

Maybe the open secondary which resulted from no plasma stream caused internal carbon tracing?


texts: Can I safely operate a PLL below it's "minimum" RF frequency?

texts:
I was wondering if anyone has had luck operating a PLL below the spec'd minimum RF frequency. For example, Analog's ADF4107 PLL specs 1-7GHz RF input frequency, but I don't immediately see why it can only operate in that range.

For PLLs with external oscillators, what is really constraining the RF frequency range? Having an upper bound makes sense, but it seems like you should be able to run them (almost) as slowly as you'd like.


texts: Advantages of parallel over serial connections

texts:
As far as my understanding goes, parallel data connections are faster than serial at the same frequency. However, when you increase the frequency in parallel you start getting bits 'cross-talking' and getting transferred onto the next bus. Serial however, since it's only a single bus line, can have the frequency increased to make it faster than parallel without a problem. Also, surely parallel is more expensive as it uses more lines.

So my question is, what actually is the benefit of using a parallel data connection over a serial one? Are there any? If not, why do we still use parallel connections?


texts: Responsible Battery Reserve Capacity and Low voltage?

texts:
It's been asked here, but looking for clarity.  How bad is it to undervoltage a 12-volt lead-acid battery?

SLI automotive starter batteries list RC (reserve capacity), but I think this a usable amperage that does not take battery life into account.

Since Starter batteries are not intended for deep cycle, what's a safe low voltage disconnect that preserves my batteries full life?

12v, 11v or 10v?

My battery is rated 70AH, 900CCA, 120RC.


texts: How to control a parallel OLED graphics display

texts:
I'm thinking of using a matrix OLED display like this one. This display uses a parallel interface very similar to those I've seen on text LCD displays, so I assume I'd control it in a similar way. However, the more I think about it, the less sense it makes.

Essentially my question is this: How would I set certain pixels on this display? And does anyone know of a reference for the various instructions I can send to it?

Thanks!

By the way, I noticed in the data sheet it has a built in controller called "OLED-0010". Is this of any relevance?


texts: Is accelerometer taking as much power (current) as it needs?

texts:
I want to connect accelerometer to an oscilloscope. I have 3x AA rechargable batteries (2550mAh).

I was told that e.g. microcontroller knows how much amps should it take and it wont burn if I connect it to those batteries.

But e.g. LED would burn. What about accelerometer? Is it able to take as much amps as it needs or should I use resistor?

Any other advices and tutorials provided regarding accelerometer+microcontroller or accelerometer+oscilloscope are appreciated.

This is my accelerometer (ebay title): GY-521 6 DOF MPU-6050 Module 3 Axis Accelerometer Gyroscope Module for Arduino

Will it work also with Atmega32 even though it's written there for Arduino?


texts: Is it possible (feasible) to use a synchronous buck regulator for balancing batteries?

texts:
I need to build for a hobby project, a active balancing circuit for large number of LiIon series cells (90 cells). So it needs to be cheap but efficient :)  (ie. not resistive dup). After lot of research, I found this circuit on internet

with the schematic as follows

Now the explanation of the author is quite poor, saying that the buck will "track" the VBAT/2 which is VCOM. I really don't fully understand the principle, so I can scale for my needs. Also, I'm puzzled about efficiency.
If buck's FB is feed by VBAT/2, then the buck will (try to) regulate VCOM (middle) to VBAT/2 which can happen only when (after) batteries will have the same voltage.
This can work only if bottom BATT has lower voltage, so BUCK, absorbing energy from both, will charge it until become equal.
But what if this bottom BATT has higher voltage? The BUCK will try to equalize the same, but as far as I see, will discharge it through buck SW itself (synchronous, lower side mosfet). So BUCK needs to be synchronous one for sure.
Am I missing something?
What does the 2'nd OPAMP denoted LPF filter?
Thank you in advance for further clarifications.


texts: Are normally open contactors virtually safe from failing closed?

texts:
Quick question: are normally-open contactors (which I assume are simply high breaking capacity relays) virtually safe from failing closed?

I want to cut off a 400V 3-phase supply using an emergency stop, and I have 2 options:

Use a 3-pole emergency stop, and wire the three phases to that button. I don't like the idea of 400V being so close to the user's hands.
Wire the contacts of a 3-pole normally-open contactor on the supply line, and wire the emergency stop on the 230V coil.

Three phase is used for heating, not for a giant chainsaw, but the emergency button should still do its job should it be pressed. So is option 2 commonly accepted, and safe enough for an end product? Any norms stating this on which I could rely?

Edit implementing the answer

I am quite keen on the idea of forcing the user to fix a failure in the redundant system, but I'm trying to limit the number of components as well. Is this a good comromise? I found this contactor, which has 1NC and 1NO auxiliary contacts that we can use.

Since the current in the coils is already very small compared to the switches capability, I made them single pole, if that is acceptable.

In particular, I'm not sure whether there is a possibility that the auxiliary contacts do not follow the main contacts (meaning the main contacts may fail closed or welded without the auxiliary contacts staying open when normally closed), could you confirm?


texts:
I am new to KiCad but have extensive experience with Allegro:
The goal create a rectangular board outline that is 55 x 30 mm with the top left corner at x,y 0,0.
This is possible in OrCad through the command line prompt. Is there a similar way to type in the dimension in KiCad versus moving around the cursor till you get to the right spots?


texts: Best circuit to turn on a (5v heating pad) switch during the day?

texts:
Most of the circuit examples I'm finding online for LDR or other light-detecting circuits appear to be for turning things on at night. I'm trying to rig up a small heating pad under a birdbath using a 5v heating pad (about 3ohms/8W) tied to a 2C thermal switch.

I plan on powering it from a 5v power pack with a small solar charger. But since birds don't really come at night (and since it is colder at night), I'm wondering if there's a way to build a simple off-at-night switch using something like a mosfet. I'm EE challenged, haven't worked a lot with LDRs and don't want to resort to an Arduino solution if I don't have to.

Any help is greatly appreciated.

FYI, in my parts bin I have a mix of mosfets available such as IRF520, IRF530, IRF540 and a few smaller types like 2n7000 and BS250. Healthy assortment of xsistors (2n3904, 2n3906, 2n2222, and an assortment of B*)
I even have some relays, but would prefer as simple a circuit as possible and can buy more parts if needed.
I found some gl5537 ldrs, but can get something else if need be also.


texts: Is it safe to power a monitor without grounding?

texts:
After viewing https://superuser.com/questions/461898/earthing-is-it-important-for-laptops and learning about double insulation, it seems that an appliance is safe as long as there is no way that the chassis can become live if a wire becomes disconnected internally. My computer monitor has a plastic case, why then does it have a 3-prong grounded plug? Is there is a risk that the screen itself could conduct electricity or that the plastic is not insulating enough?

I ask because I am looking to make a MagicMirror style display with probably a wood frame and would like to use a less bulky cord to power it but naturally I don't want to kill anyone.


texts:
The purpose of an optocoupler is to provide isolation. How can it provide isolation if Vcc is connected at both sides as shown below ?

Also, I assume I connect the GND of VCC only at the right side, is that correct ?

So connect it like this ?:


texts: Trying to figure out what kind of input signal this loudspeaker amp circuit needs

texts:
I'm still trying to figure out how this door intercom module works. It's a 18y old siedle TLM 611-0 module, I figured out the mic part, there the audio signal is modulated onto the current the mic amp draws. But the loudspeaker part baffles me. This is the circuit diagram of the speaker amp I reverse engineered from the PCB. I don't really know how it works. It's quite a strange design and I'm not really good with analog electronics. Help is very much appreciated.

Apparently some people can't see the embedded image of the schematic, here is a link to it: https://i.imgur.com/rj3Cwcc.png

EDIT: Updated the schematic to a conventionally drawn one. Old hand drawn version of the schematic: https://i.imgur.com/Evuv3Wm.png


texts: Does magnetic coupling cause common mode or differential noise in this case?

texts:
Below are straight and twisted pair transmission lines:

From the above illustration the induced noise current due to the magnetic coupling are opposite direction in each lines.

It seems like magnetic coupling causes differential noise rather than common mode noise. Because the currents above are not flowing the same direction.

On the other hand, I read many places that STP wiring minimizes the induced  noise and differential ended inputs are used to subtract the same noise on both lines.

But this illustration contradicts that. For diff-input amplifier to cancel out equal noises the currents due to the magnetic coupling must flow in same direction.

Where am I thinking wrong here?

EDIT:

In below diagrams there are two independent scenarios where the only source of noise around is assumed to be magnetic field such as 60/50Hz or so. In both scenarios the transmission line is perfectly balanced and twisted pair is used.

The only difference is that in Scenario I single-ended inputs used; and in the Scenario II differential-inputs used.

simulate this circuit – Schematic created using CircuitLab

In this case, would the noise due to magnetic coupling be differential? And would using single ended or diff-ended inputs will not make any difference?


texts:
Can anyone assist me with correcting this circuit?
I'm trying to build a 12 V lead acid battery charger that would have a green LED indicator when charging and a red LED indicator when fully charged.

I feel the collector should send enough voltage only to allow a flow of current through the emitter if the battery voltage is less than 13.5 V and once it get to 13.5 V (when the battery is full), that should be able to trigger the base which would let the red LED go on.

I thought the capacitor should act as a filter.

I go the charge indicator circuit from Google but missed the site. But I designed the charging circuit from my little like no knowledge of electronics.

And also how can I test if the battery is charging?

I'm an amateur in circuitry. I just love electronics


texts: How strong is the electrical field inside a microwave oven?

texts:
I'm interested in figuring out the approximate peak electrical field strength inside a microwave oven.  The question is not so much about the exact number, but rather what reasoning to use to work it out approximately.   I'm interested in getting the rough order of magnitude without doing a full physics simulation.

Scenario 1: Microwave oven with output of 1kW, running with nothing inside, 1 cu ft chamber.  I assume in this case most of the 1kW (except for very small amount absorbed in walls or lost as leakage) is reflected back into the magnetron where it must be dissipated as heat.  There will be an oscillating electrical and magnetic field inside the chamber, possibly with some standing waves (peaks and nulls).  What determines the height of the peaks?

Scenario 2: Same, but with an object inside (let's say a cup of water, 1 pint).  What fraction of power is absorbed in the object?  What is the electrical field inside the object now, and what is it in the rest of the chamber?  I assume now most of the power would be absorbed in the object, because (essentially) the waves bounce around until they are absorbed; the entry aperture is relatively small so the fraction hitting that and going back to the magnetron is much less than hitting the object (thinking of the waves as rays as an approximation).  The electrical field in the object would seem to be related to dielectric constant, dielectric loss factor, etc.

What simplifying assumptions can be made here?  For example, is it possible to model the chamber as a waveguide?  Etc.


texts: Trouble understanding a given circuit for an LDR pulse sensor

texts:
I'm a second year physics student, part of a group, and we're trying to build a pulse monitor following this guide. This is the schematic I'm having trouble to understand:

I have basic knowledge of working with Kirchoff Laws, but this is my first time working with transistors.

I assume the transistors are there to amplify the signal variation of the LDR. How do they do that?

From what I understood from my research about these transistors, there is a 0.7V drop between base and emitter, and base current is multiplied by a constant to determine collector current. I tried using these to calculate an expression for the voltage measured in the analog pin in function of the LDR resistance, to understand the effect, but I did not get anywhere decent. I want to understand why the circuit was designed like this (unfortunately the guide does not explain that), so that we can troubleshoot easily and change things up if needed.
Thanks in advance!


texts:
I'm a Computer Engineering student, and my full knowledge of RFIDs is limited to the research I have conducted thus far (mainly using this site).  As such, there are still some general concerns I have that I could not find direct answers to.

My current intent is to use an RFID reader module (possibly the MFRC522) connected to a microcontroller (I currently use a TM4C123GH6PM, but would switch to Arduino if it would be easier) to read in ~60 RFID tags stacked directly on top of each other.

As I have understood thus far, to do so would require the use of a reader which supports anti-collision.  After discovering the MFRC522 supports this, my new question has become - is there a limit to the number of tags the reader can handle?  I understand that the reader's range could be problematic, but this aside, would it be able to handle that many tags?  I suspect that this will not be the case, and if not, what kind of things should I be looking for in a reader in order to handle such a scenario?

I'll reiterate - I only have a very basic understanding of RFIDs.  I am much more educated in handling the microcontroller, and for my current project I would like to utilize a reader module to handle a scenario of ~60 stacked tags.  Thanks in advance for any feedback on this situation!


texts: Use of DC source in Zener clamping circuit

texts:
A question in my engineering degree asked me to design a clamp circuit that gives a 10V 50Hz AC signal a +5V DC bias. I designed the following circuit as my answer:

I assumed 0.6V forward drop for the regular diode, but otherwise I assumed ideal operation. (The capacitance and resistance were chosen so that the capacitor didn't discharge too quickly between cycles). I tried it in a circuit simulator and it worked, however the solution included a DC source:

According to our textbook,

  "If the desired clamp voltage requires the diode to be reverse biased,
  it is necessary to return the discharge resistor to a suitable dc
  supply voltage to ensure that the diode conducts and performs the
  clamping operation." ~ Electrical Engineering: Principles & Applications
  (5th Edition), Allan R. Hambley

This explanation doesn't really help me understand why the source is needed. Assuming the diode branch is ideal except for the 0.6V forward drop, it should have an I-V characteristic that conducts whenever the voltage across it dips below -5V. This should achieve the desired outcome, no? The capacitor would become charged to have 5V across it, as needed. Why do we need the DC source? And why was it 15V? (We were told we only had +/-15V available as a DC source.)


texts: identify this connector - faston housing

texts:
need MFG of this connector. It is not tyco event though there are tyco fastons installed (confirmed by Tyco).
2 position faston housing. tab locks are on facing outwards.

no markings on connector

color is light gray, some sort of plastic


texts:
I'm building a power supply for old Schoeps CMT30F microphones. Standard condenser mic are 48V-powered nowadays, but these are 60s/70s Schoeps mic from RadioFrance/ORTF, customized at that time to be -9V or -10V powered.

I need to add capacitors to avoid the 9V to go in the preamp / audio interface.

I was told to buy "audio capacitors polarized 100 µF, 50V, preferably Vishay" (formerly Philips?). These are more than 3€ per unit, and these Vishay are 11.89€ per unit!

Question: what kind of difference is there between such a capacitor, for audio applications, and a bog-standard 100 µF / 50V, that costs 0.20€, i.e. 15 times less/60 times less?

Will the difference be hearable in the audio frequency spectrum?

By the way, here is the ... hum ... sche ... schematics of the power supply I'm about to build. The capacitors are the 2 things in pink near the audio interface (bottom of the drawing). Do you think it's more or less correct?


texts:
I was reading an article that explains the Infrared sensor until I came to the wavelength region's section, which has been mentioned as the following:

The infrared waves typically have wavelengths between 0.75 and 1000µm.
a- The wavelength region from 0.75 to 3µm is known as the near infrared
region.
b- The region between 3 and 6µm is known as the mid-infrared
region, and
c- infrared radiation which has a wavelength greater higher than 6µm
is known as far infrared.

I have searched for an image that shows those numbers, and I found this one:

I have transformed the µm's values to m, but they didn't fit to the numbers shown in the image. So, what's wrong?
The article: https://www.azosensors.com/article.aspx?ArticleID=339
A side-note: I took into consideration that that image is wrong, and I found this one, but I don't think it is right either.

My calculations:
0.75µm and 1000µm = 750nm and 1000000nm = 0.75x10^-6m (= 7.5x10^-7m) and 1x10^-3m (= 0.001m)
3µm = 3000nm = 3x10^-6m
6µm = 6000nm = 6x10^-6m


texts: Should I calculate a resistor value for driving indicator LEDs from TTL outputs?

texts:
Traditionally I have always used a \$1\:\mathrm{k\Omega}\$ resistor as a current limiting resistor for driving an LED direct from a TTL (or 5V CMOS) output.  I can't remember how I came by this value - it is lost in the annals of history.

Is this OK, or a Bad Habit™ I have got myself into that I should break?

Should I be calculating a more precise resistance to use from the voltage and current draw of the LED I am using?


texts: Regulated +5V drops when relays are switched on

texts:
A regulated power supply RAC02-055C/277 provides 5V to an Arduino driving 2 relays. The power supply is rated to provide 2W of power.

Connecting a multimeter between one of the leads of the power supply to the +5V bus (which connects to Arduino 5V pin and the +5V pins of the relays), and another multimeter across the +5V and GND rails, the current reads 98.6 mA and the voltage is 4.969 V.

When one of the relay is turned on, the readings are 209.4 mA and 4.911 V.

When both relays are turned on, the readings are 301.9 mA and 4.869 V.

How can we prevent the voltage output from the supply from dropping/changing whenever the relays are turned on and off? The +5V rail is used to bias a input signal, so a constantly changing +Vcc will give inaccurate readings.


texts: Proteus BJT Astable Multivibrator Simulation Error

texts:
I am pretty new in Proteus and made a simple flip flop circuit as shown below.

When I run the simulation, the circuit does not work as intended. Both of the LEDs light up at the same time. (LEDs should light up one by one)

Also, after I stop the simulation I get this error code.

Why am I having this issue? Is it about the circuit itself that I am doing wrong or is it about the error code I am getting?


texts:
I have this table fan which wasn't working one day. So I took it apart and found the resistor near the power supply exploded. The colour bands are completely messed up. Only the top and the bottom ones can be seen.

Is there any way to find what value it is without using an ohmmeter as I don't own one? Maybe by knowing the wattage consumption of the fan or something like that?


texts: I don't know what this component is. It's found on an adblue ECU for Citroen. I suspect it's faulty and need to order it.


texts: Confusion with input type of ADCs in datasheets

texts:
I'm very much confused with the ADC terminology. I know what a differential amplifier is. And a differential amplifier can take a single-ended(unipolar) source as an input. It can of course better take bipolar inputs. There is also single-ended input amplifier where one end of the differential input is connected to the analog ground. This can only work with unipolar source.

But when it comes to datasheets of the ADCs, what does the following terminology mean?:

-Differential input channel ADCs

-Fully differential input channel ADCs

-Pseudo differential input channel ADCs

-Single ended ADCs

Is the above category about the source types(unipolar or bipolar), or is it about type of the amplifier itself?

For example if you go to this site: http://www.analog.com/en/products/analog-to-digital-converters/precision-adc-20msps/single-channel-ad-converters.html

There is a section called "Input types".

Edit:


texts: avrdude error - stk500_paged_write() protocol error

texts:
I am using my Arduino Uno as a programmer to program my ATtiny85. I uploaded the ArduinoISP sketch to my Uno. I double checked my wiring, did some googling, but I still can't figure out why I get this error ...

avrdude: stk500_paged_write(): (a) protocol error, expect=0x14, resp=0x11
avrdude: stk500_cmd(): programmer is out of sync

... when I run this command:

sudo avrdude -p t85 -c arduino -P /dev/ttyACM0 -b 19200 -U flash:w:src.hex\

Then I checked to see if the ATtiny was responding, I ran this command:

sudo avrdude -P /dev/ttyACM0 -p t85 -b 19200 -c avrisp -v

The results were successful.

EDIT:

Here are the time stamps (just in case):

15:24:29.502445729 E:
15:24:29.623628385 E: avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny85
15:24:29.761744829 E: avrdude: AVR device initialized and ready to accept instructions
15:24:29.766251405 E:
15:24:29.812810614 E: Reading | ################################################## | 100% 0.05s
15:24:29.821187588 E:
15:24:29.825324777 E: avrdude: Device signature = 0x1e930b
15:24:30.171341329 E: avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed
15:24:30.180631410 E: To disable this feature, specify the -D option.
15:24:30.334997131 E: avrdude: erasing chip
15:24:30.495926604 E: avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny85
15:24:30.632387526 E: avrdude: reading input file "src.hex"
15:24:30.637210000 E: avrdude: input file src.hex auto detected as Intel Hex
15:24:30.641710226 E: avrdude: writing flash (98 bytes):
15:24:30.645806835 E:
15:24:30.712364458 E: Writing |
15:24:30.718291473 E: avrdude: stk500_paged_write(): (a) protocol error, expect=0x14, resp=0x11
15:24:30.752474103 E: avrdude: stk500_cmd(): programmer is out of sync
15:24:30.827210626 I: Finished with exitcode 1

I can't seem to figure out what is wrong. Any suggestions?


texts: What actually causes gyroscope drift in IMU?

texts:
I've been researching online to understand how to get gyroscope data from the MPU-6050 which is probably one of the most popular IMU's out there. But i am confused over the reason why the gyroscope drifts, as i found two sources which give different reasons...

http://www.pieter-jan.com/node/7

"Because we can't take a perfectly continuous integral, we have to take the sum of a finite number of samples taken at a constant interval Ts. Ts is called the sampling period. Of course this approximation will introduce errors. When gyrosocope data changes faster than the sampling frequency, we will not detect it, and the integral approximation will be incorrect. This error is called drift, as it increases in time."

So, this source claims that the drift is due to the non-ideal sampling frequency when using a microcontroller like Arduino to sample the output of the gyro.

https://www.w3.org/TR/motion-sensors/#complementary-filters

"In order to get rotation (angle) from a gyroscope, which senses angular velocity, you need to perform a single integration.
f ≡ frequency
∫cos(2π×ft)) = (1/(2π×f)) × sin(2π×ft)
But be aware that integration turns noise into drift. As we see above, the integration gets a 1/f outside, meaning that high frequency (f) noise disappears with integration, i.e. a noise of frequency will drop by a factor of a 100, but a very low frequency will be amplified, meaning the gyroscope will drift over time."

And this source claims that integration itself gives the reciprocal of frequency which would cause this drift, and that's without even going to the digital sampling.
So, which one is correct? Or maybe none of them??


texts: Subwoofer LEDS - RGB, brightness controlled by amp

texts:
I'm trying to build a subwoofer with integrated LEDs which will pulse to the beat. I've seen a few projects for this around the net, but everybody seems to be 'winging it' and not necessarily creating a circuit that will last.

So, if it's possible I'd like to do this the 'right' way. The extra twist I've got going on is I'm using RGBW strip lights with a controller.

The intent is to have the strip color (and initial brightness) controlled by the LED controller.  For this portion the controller has a dedicated 12v DC input.  The complicated part that I'm trying to achieve is to have the strip intensity driven by the amplifier output, such that the LEDs would 'pulse' with the subwoofer output.  What I presume is that the output from the controller needs to be regulated, and the most promising solution so far seems to be a transistor, controlling the power sent to the leds based on the input from the audio amplifier.  In my limited electronics experience the common wire in the 4-conductor output from the LED controller was the candidate for this regulation.

The amp would be putting out ~0-18v AC for this application.

I plan to use this controller.

And these LEDs.

A helpful user on another forum submitted this sketch for a possible circuit, with amp power coming from the left and the LED controller on the right.

Does this look like something that will do what I'm looking for?  Any suggestions or ideas for improvement?


texts:
I am working on turning on a board of mine on which I am attempting to use a TI TPS563208 switching regulator. I believe I have followed the typical application in implementing this regulator in my conversion of 12V to 3.3V (see schematic below), but I have now damaged two parts in the exact same manor and I'm struggling to understand why. During my initial testing I had powered it with my bench top supply set to 12V with a low current limit. As soon as I power up the 12V supply I noticed the current reading shoot up and then the output regulation of the TPS563208 dropped out to nearly zero. At this point measured as much as I could and found that the SW output now had a reading of only about 3 Ohms to ground. Before powering the system up I was reading 70 Ohms (this seems reasonable for the load on my supply).

At this point I pulled the dead TPS563208 and made sure I didn't have any shorts on my board (either from assembly or manufacturing defects). I walked through the entire design checking for anything that didn't match my schematic and found none. I do not believe the problem lies with the 12V side as without U5 in the schematic my 12V draws basically no current, and I can manually supply 3.3V to the downstream circuitry from the bench supply without issues. Once I confirmed that nothing was physically wrong, I put a spare part back on the board, added an electrolytic cap to the input (in attempts to possibly reduce overvoltage spikes on power up (as described in linear's AN88 app note), and this time set my bench supply to 6V. Powering this up appeared to work! I did notice I was getting some drift on my output voltage, but it was regulating and drawing approximately the amount of current I expected for my load. From here I increased the input voltage to 9V and it again appeared to work. Unfortunately though, once I set it back to my desired 12V, the output voltage came up at 3.3V, quickly increased, and then dropped out and the impedance to ground on the SW output again read nearly zero. It was toast.

I've looked over the recommended layout and compared it to mine and see I could make some serious improvements, but what I want to understand is if this is something that could be caused simply by bad layout? I'm going to do another revision of the board, so I can cleanup the layout but if I have some other problem I'd like to understand now to reduce the chance of having to do a third rev of the board.

Hopefully you guys can help! I've put down a few other buck converters in the past and didn't have any issues then, but I'm admittedly a bit rusty.


texts: How can a tunnel diode be used as a memory element?

texts: I read in applications of tunnel diodes that it can be used as a memory element. I am not able to justify or verify this statement. It would be very helpful if a circuit showing logic storage using a tunnel diode is included in the answer.


texts: Enable port RA0 as input and retrieve value LDR from led

texts:
I'm using the picdem 18F4550 with microchip v8.63 with the C18 compiler.

I will enable PortA to set as input, I will connect a LDR on port RA0. Which is as following (I think):

TRISAbits.TRISA0 = 1; //<= set RA0 as input.

Now I want the value of the LDR (voltage/value if a led is on), can I say:

int colorLed = PortAbits.RA0;

And now in the variable of type int there is the value/voltage of my Led.

Correct me if I'm wrong.


texts: The Ohm's law calculations of the parts do not agree with the whole

texts:
In the circuit below, the Ohm's law calculations of the parts do not agree with the whole:

the voltage drops of the parts do not add up to the total voltage, and
the current does not calculate to be the same throughout the entire circuit.

Why? Actual VOM readings are in red and done with a digital VOM.


texts: Control toy car transmitter with Arduino Uno

texts:
Could someone suggest how I would go about soldering the necessary wires to a toy car transmitter so it can be connected to the pins of an Arduino Uno to allow the Arduino to  control the car - forward, backwards, left, right. Could I solder wires to the pushbuttons connections? If so where?

Here is how the board of the transmitter looks.


texts: What are an amateur's options to put a high-end IC on a board?

texts:
I'm actually an experimental physicist who does software-development for a living. So my knowledge basically stops at writing micro-controller programs and putting them on a breadboard, and hooking the wires the simple way.

Back then in my student days, I also managed to get a PCB with holes, and solder electronic parts on it to create an RCD programmer for a PIC16F84 microcontroller, and it worked (that was like 10 years ago).

Now, I would like to make a high-resolution ADC with Arduino, but it has to be reliable and eventually I'd like to put it in a case/box. The ADC chip I have my eye on is ADS1256.

I'm targeting 24-bit with about 10 kHz sample rate, and this chip seems to be perfect. However, I have absolutely zero knowledge on how to get such a relatively small chip on a board, so that I could interface with it.

I'm wondering whether there's a simple way to do this myself (e.g., with a PCB with holes, like the one in the picture), or whether there are services that would do this for money without having to make 10k pieces. One challenging part when thinking about this as DIY is that if I screw this up, everything will act like an antenna and I'll have lots of noise in my digitized signals.

What are my options? Please advise.

PS: If it's relevant, I live in Germany.


texts: Is this HD-44780 compatible display damaged?

texts:
I am developing an assembly application that includes a HD-44780 compatible 20x4 display over the I2C bus. After several attempts, I have finally managed to initialize the display in 4-bit mode and show a message, but after a few seconds the display seems to go crazy.
To eliminate the possibility of a bad initialization, I have tested the display with the Arduino example sketch I2C_Hello_World.ino, with the same result.
This 15 second video shows the behavior of the display
This is the sketch:
#include "Wire.h" // For I2C
#include "LCD.h" // For LCD
#include "LiquidCrystal_I2C.h" // Added library*
//Set the pins on the I2C chip used for LCD connections
//ADDR,EN,R/W,RS,D4,D5,D6,D7
LiquidCrystal_I2C lcd(0x27,2,1,0,4,5,6,7,3,POSITIVE); // 0x27 is the default I2C bus address of the backpack-see article
void setup()
{
   // Set off LCD module
   lcd.begin (20,4); // 16 x 2 LCD module
   lcd.setBacklight(HIGH);
//   lcd.clear();
   lcd.setCursor(0,1);
   lcd.print("LEDMedia art digital");
   lcd.setCursor(0,2);
   lcd.print("Traverser v.0.0.1");
}
void loop()
{
}

Is this display damaged? Has anyone else come across this behavior? If the display is not damaged, is there a hardware or software reason to explain it?
Thanks for your help.


texts:
Is there any disadvantage to running a Linear Regulator under the minimum voltage stated in the datasheet? For instance, In the datasheet of the LM7812C2T, it says the minimuim voltage in order to to get 12v out, is 14.5v in. However, if i run it at 12V, the actual output is around 11V.

Is there any reason this is a bad idea?

Edit: Datasheet added as suggested
ST L78 Regulator Datasheet.


texts: In logical progression, what things does a person need to know to design a robust opamp from BJTs

texts:
Opamps contain things like current mirrors, differential stage, push-pull pair and much more. Once a person starts from learning that BJT has 3 terminals for which Ic≈Ie≈βIb, what topics must a person master until they are able to design their own OpAmp. A target would be to atleast design a the "741" opamp. As we go into depth there are more complex devices that have ultra low noise or work with only a +ve rail voltage e.t.c. Lets ignore that for now.

So what topics must a person master, in logical order, to be able to understand the design of and design their own 741 opamp?


texts: How can i determine the Path-Loss Exponent

texts:
For my school project we have to calculate te relative posistion between chair using rssi in a large office building, right now have it gotten to work that the chairs can see each other posistion in rssi value, but we them to see each other in meters.

So after some researche I came to this link:  Calculate distance from RSSI

In this link I found the formula: RSSI (dBm )=−10n log10(d)+A

So the problem is I can determine the other variables but I have trouble determining the n variable which is the Path-Loss Exponent. In the link they speak of that the value is somewhere between 2.7 and 4.3 but how can I choose which is best for my case.


texts: Help for identifying pinout of unknown mp3 chip

texts:
I'm trying to use a cheap mp3 player to play song using Arduino, I couldn't find the datasheet of the main chip but I made some progress identifying some pins.

                 Pin
                1  16  Busy
Play/Stop IO1   2  15  GND
Prev/Vol- IO2   3  14
Next/Vol+ IO3   4  13
                5  12
                6  11 SPK -
                7  10 SPK Right
                8   9 SPK Left

This looks very similar to the picaxe by8001 and the WT5001

I will need some ideas to find the datasheet or at least find RX/TX/ADC KEY pins.

More pics here

Note: Why not use mp3 module for arduino? I try the WTV020 with no luck, I could buy a dfplayer or the WT5001, but this mp3 player cost 1/5 of
those modules.


texts: Why is one lightbulb in a string illuminated?

texts: I noticed that in various strings of lights only one was illuminated. It seems implausible that all but one out of several hundred blew. What caused this and why did this particular light turn on?


texts:
I am writing one microbasic codes for atmega 32 ,the program works on Proteus simulation but when i want to program it the programmer got this error:

file hex address overlapped problem

So the Codes are:

    program MyProject
' Lcd module connections
dim LCD_RS as sbit at PORTb0_bit
dim LCD_EN as sbit at PORTb2_bit
dim LCD_D4 as sbit at PORTb4_bit
dim LCD_D5 as sbit at PORTb5_bit
dim LCD_D6 as sbit at PORTb6_bit
dim LCD_D7 as sbit at PORTb7_bit

dim LCD_RS_Direction as sbit at DDb0_bit
dim LCD_EN_Direction as sbit at DDb2_bit
dim LCD_D4_Direction as sbit at DDb4_bit
dim LCD_D5_Direction as sbit at DDb5_bit
dim LCD_D6_Direction as sbit at DDb6_bit
dim LCD_D7_Direction as sbit at DDb7_bit

dim on_a_0 as integer
 dim hours, minutes, seconds, day, week, month, year as byte
' Declarations section

dim txt,txt_inin as string[6]
dim kp,ok,k_set,chanel,Pwm_Percent,Pwm_chanel ,on_off as  integer

sub procedure Lcd_0()
              Lcd_Init()
              Lcd_Cmd(_LCD_CLEAR)               ' Clear display
              Lcd_Cmd(_LCD_CURSOR_OFF)          ' Cursor off

end sub
main:
'   Main program
for chanel =1 to 1
'     for week =1to 7
     for Pwm_chanel=1 to 1
     on_a_0  =0
     on_a_0 =0
     on_a_0  =0
     on_a_0 =0
      Delay_mS(1000)
      next pwm_chanel
'      next week
      next chanel

 while True

 for chanel =1 to 2
'     for week =1to 7
     for Pwm_chanel=1 to 2
     if  (on_a_0 >= hours ) and (on_a_0 ) then
         if    (on_a_0 >= minutes)  and (on_a_0)then
           Lcd_0()
           Lcd_Out(1,1,"on pwm mode")
           inttostr(chanel,txt)                     ' ??? ????? ???? ? ?????? ????? ? ????
           LCD_Out(1,13, txt)
           inttostr(on_off,txt)                     ' ??? ????? ???? ? ?????? ????? ? ????
           LCD_Out(2,1, txt)
           inttostr(pwm_chanel,txt)                     ' ??? ????? ???? ? ?????? ????? ? ????
           LCD_Out(2,4, txt)
         end if
      else
        Lcd_0()
        inttostr(on_a_0 ,txt)                     ' ??? ????? ???? ? ?????? ????? ? ????
           LCD_Out(1,11, txt)
            inttostr(week,txt)
            LCD_Out(2,11, txt)
           Lcd_Out(1,1,"offfff")
            Delay_mS(100)
      end if
'      Delay_mS(1000)
      next pwm_chanel
'      next week
      next chanel

 wend
end.

and the file files (codes and Proteus ) are accessible by this link:

http://filepi.com/i/ep8bQ7y

Thanks a lot for your attention.


texts: Salvaged touch pad from old laptop projects

texts:
I salvaged this touchpad from an old laptop and I would like some ideas for using it,
I thought about using it as a light dimmer for two sets of lights.
Does anyone know how it works? I'm sort of a newbie but I'm willing to learn.

Where can I find its data sheet?
Here's the print on the back

ALPS 94v-0
JCI-S1S H
56AAA1865C

(in case the images aren't clear)

There is a small IC under the tape : 1CA017A 0B/U234

The touchpad came from an old Acer laptop,  I don't remember the specific model anymore -- very old, AMD Athlon and 1 GB RAM and a floppy drive old.


texts:
I am starting on designing a sort of HAT (like used on the RPi) for the Nvidia Jetson Nano.  As I am on my third year of electrical engineering I know little to nothing about EMI and shielding. Should I (and in what degree) be concerned about EMI/RFI shielding?
A little info about the project:

The casing will be containing the Jetson Nano (+HAT), a Raspberry Pi, a HomePlug adapter to interface and power a device outside of the case with a coax cable, and a power converter to power the external device.
The HAT will provide a connection between the HomePlug device and the Nano, as well as use some AD-converters to read analog input by the user, by means of an analog stick. (0-5V)
The casing will be about the size of a small office-PC
The Jetson Nano will drive a monitor attached to the casing


texts: Effect of negative feedback on Amplifier

texts:
The above problem was asked in a test. I got the wrong answer because I solved it in the following way.

BW without FB = 1000 - 100 = 900

BW with FB = BW without FB * (1+A*beta) = 900 * 100 = 90kHz

I understand that both both the formulae are different and both can't be right at the same time. But my book mentions below 3 formulae bcz of which I got confused in the test.

BW with FB = BW without FB * (1+A*beta)

fH with FB = fH without FB * (1+A*beta)

fL with FB = fL without FB / (1+A*beta)

Please guide me on this, which formulae to use ?


texts:
I am trying to study/learn mathematical modelling of a DC motor
 i came across an equation which is known as the mechanical equation for an armature-controlled DC motor

I have understood other parameters in this equation but i am confused by the highlighted "b" term , what is meant by it?


texts:
I am trying to figure out how to drive a solenoid/voice coil at 3V and 400-1000mA with a reciprocating output (forwards and reverse current) at around 50Hz as cheaply as possible. I have built some test coils and they work fine in terms of force at that wattage. I have considered a number of options for the driver, but am looking for some fresh, unbiased input. Let me know what you guys think!

EDIT: I am looking to use AA or AAA batteries to power the device. Thanks!


texts: Current transformer energy harvesting from a mid-voltage line

texts: I'm planning on harvesting energy from a 33kV line which has an average 10rms A  current. The main conductor (N1) has a overall diameter of about 13mm.In the beginning I tried to harvest around 3-4 W of energy but it seemed impractical with a core of 10^4 relative permeability and 1.8 T of flux density. To increase the harvesting energy we need to increase the core area (increasing r) while reducing the major diameter of the core (X0). So at some point it comes to a limit of energy harvesting as I understand. There's no possibility to put more than one turn of the primary conductor around the core and the average current of the primary conductor is limited to the above value 10rms A most of the time. Can you tell me is there anyway to harvest that much of energy from a current transformer for above specifications or do I have to reduce the expected harvesting energy amount. Does increasing the number of secondary turns (N2) increase the harvested energy amount. I went through the theories so many times but I still feel confused about this. I'm expecting a descriptive answer and I will provide all the details if you need prior answering the question.


texts: What is the distortion introduced by a multiplexer?

texts:
Question in short:

If I have a multiplexer, and my selected input is X volts, I suppose that the multiplexer's output will be X+-ΔX volts. How can I calculate ΔX ?

Question with more details:

I have four Wheatstone bridges composed by loadcells liks this one, its output is a differential signal S- and S+ that I need to amplify with a differential amplifier.

I was thinking about using just one amplifier and multiplex its input signals with a multiplexer like the CD4052B.

The excitation voltage of the bridge is 5V thus the difference between S+ and S- is in the range of 0mV to 5mV. The amplification gain is 1000.

If the ΔX introduced by the multiplexer is bigger than 0.005mV, it is not good for me, than I would like to know how can I calculate the ΔX so I choose the best multiplexer or go to another solution.


texts: Amplifier design: feedback with unclear poles

texts:
When designing a closed loop amplifier for audio the poles of the open-loop transfer function are usually only vaguely known.

\$\frac{1}{(s-p_1)(s-p_2)...}\$

These poles can be modeled as \$RC\$ low-passes which attenuate the signal from their break frequency and, more importantly, add phase shift to the signal.

To avoid to much phase shift before gain reaches the 0-dB limit usually a pole is deliberately  added at a very low frequency so the open loop gain falls below 0 dB before the other poles kick in.

So far so good. But how can the second, third etc pole be estimated to get a clue where the first pole has to be?

What does the notion of "so much dB feedback is ok to be applied without threatening the stability" mean? How is the applicable amount of dB feedback defined?

An example: I want an amplifier to amplify a signal 30 times and have an open loop gain of say 10000. What does it mean when I say "I apply ...dB of feedback"? Usually I would make a voltage divider of 29/1  and therefore get a gain of 30 (factor, not dB). I don't know how to put this any simpler, but doesn't the applicable amount of feedback depend on how my closed loop gain of the amplifier should be? It's often said that the more feedback the better but when I make a unity gain buffer It is useless since I want to amplify my music, right?

Long story short:

What is meant by the applicable amount of feedback?

How do I estimate the other poles?


texts: basic p-type mosfet circuit, breaks mosfet?

texts:
So I've made this basic circuit to drive Vout between ~0V and ~1.65V.
The default state should be ~0V, hence I use a p-type mosfet:
https://docs.rs-online.com/d95a/0900766b800ae907.pdf
Now, for some reason it looks like the fet has broken down after applying a voltage to the gate the first time by closing the switch (s1). I'm having quite a hard time in fet-based circuit design so maybe somebody could help me a bit in what I'm doing wrong or how I'm mis-understanding the situation?
The source is driven by a 5V supply. R1 = 20k, R2 and R3 are 10k.
Q1 is an FDV304P P-channel mosfet as given in the link above.
The circuit:

The purpose of this circuit is to drive an IC's enable pin. By default this enable should be turned low but when the switch is closed, the enable should be high. The switch simulates a IO pin from another IC.


texts: how to implement several large state machines in hardware?

texts:
There are several ways to encode state machines. However, since a circuit is required to decode the next state and output, implementing a bigger state machine would possibly reduce fmax of a design anyway.
One way to deal with such an issue is to use a soft core to implement the state machine in software. However, having multiple softcore processors e.g Nios II may not be practical as well.
Now if it becomes clear that the design requires multiple state machines where each has maybe 10s of states, does this mean that the design must be simply implemented fully in software and not in hardware or techniques exist to implement multiple large state machines which also ensure that we get large fmax? How about one designing a very basic processor that can only do basic arithmetic logic operations and write a short program that goes into a hard memory block? This adds the complexity in that debugging the assembly type code will be another new issue to deal with.


texts: How do LoRa end-devices configure their upstream and downstream communication?

texts:
I'm in the process of building a LoRa end device, and am also designing protocol. I plan on using the channels specified in the AUS915 ISM Band as outlined in the LoRaWAN regional parameters (though i'm not using LoRaWAN):

Upstream Channels 0 to 63,125KHz, DR0 to DR5, 915.2MHz-927.8MHz, 200kHz inc.
Upstream Channels 64 to 71,500KHz, DR6, 915.9MHz-927.1MHz, 1.6MHz inc.
Downstream Channels 0 to 7,500KHz, DR8 to DR13, 923.3MHz-927.5MHz, 600KHz inc.

I'm confused about the typical operation of an end device. Does this channel plan suggest that to use an end device effectively and this channel plan, I will need to send data from it on any of the 72 upstream channels, but have to switch configuration entirely to then recieve packets in one of the 8 downstream frequencies?

EDIT:

From the Radiocommunications (Low Interference Potential Devices) Class Licence 2015:

All transmitters, 915–928MHz, 3 mW max EIRP
Frequency hopping transmitters, 915–928MHz, 1 W max EIRP, A minimum of 20 hopping frequencies must be used
Digital modulation transmitters, 915–928MHz, 1 W max EIRP, The radiated peak power spectral density in any 3 kHz must not exceed 25 mW per 3 kHz


texts: Effect of length on a thermocouple's accuracy

texts:
I'm a mechanical engineer working on acquiring some temperature data using thermocouples.
Q. I wanted to know the effect of wire length on a thermocouple's accuracy.
I don't have much of electrical engineering knowledge. I did some amount of search and people have mentioned that thermocouples don't experience much of voltage drop even when they are really long (100-150m, infact long thermocouples are used in powerplants for temperature measurements. I wasn't able to figure out the physical reason behind it. I want to particularly understand effect of voltage drop in particular,  I'm not interested noise due to interference. Any leads would be really helpful!


texts: How to calculate a current being drawn by a full wave rectifier diode bridge?

texts:
I've been studying power supplies and diodes, all books I've read discuss a great deal of things, but there's something I haven't found, and that is how to calculate how much current a bridge rectifier draws when it has its output filtered by a capacitor (and connected to a load).

Sedra/Smith's book mentions that since the filtering capacitor will work as a reservoir tank, the diodes will only conduct during a certain part of the input signal needed to fill back up the capacitor, the portion that the diode is conducting is referred to as "conduction angle" , dividing that conduction angle by 2 times pi, you get cycle percentage, or in other words what percentage of the cycle the diode is conducting.

This helps to determine what the text refers to Idmax and Idavg, which are the maximum and average currents through the diode during the period of time that the diode is conducting to charge up the capacitor.

So it basically means that the bigger the capacitor (the smaller the ripple voltage) the diode will conduct during a shorter period of time, and in that shorter period of time it will have to conduct more current (since it has less time to charge up the capacitor).

Those figures obtained by Idmax and Idavg, only tell you the current through the diode during the conduction intervals, which are useful to determine if certain diode will be able to withstand brief outbursts of current. What I need to know is how much total average current is going through the diodes, or in other words:

How can I calculate the current being drawn by the bridge rectifier (entire circuit) as it would be shown on  a conventional DMM when measuring the current being drawn by the bridge, when its output is being filtered by a capacitor (and connected to a load)?

I've simulated several circuits and when measuring the current being drawn by the diode bridge is not equal to the current being drawn by the load, and that's to be expected since the diodes are not conducting all the time, but not being able to know how much current is being drawn at that point (between transformer secondaries and bridge rectifier) is keeping me from being able to determine the total current draw of the circuit, thus I'm not able to calculate the transformer's power rating needed to feed the circuit.


texts: What type of zener diode is this? The thin band is blue.


texts: Is there a specific preferred order of operation of signals?

texts:
Basic Signal Operations Performed on Dependent Variables--
The periodicity of the signal is varied by modifying the horizontal axis values, while the amplitude or the strength remains constant. These are:-

Time scaling of signals

Reflection of signals

Time-shifting of signals.

Is there a specific preffered order in which we should operate?


texts: Fan cooling is common for power electronic devices like rectifiers and inverters. Brushless DC fans have been cheap and readily available for at least 2 decades. Open frame construction is common so it is inevatable that the fan sucks dust and debris into delicate high voltage electronics causing failure. How feasable would it be to bathe a power electronics module in transformer oil? The oil is good at mains frequencies like on power distribution transformers but how would it be at say 50KHz? Would this relatively inert oil attack standard electronic components like say TO247 IGBTs, metal film caps, ceramic caps, metal film resisters?


texts:
Looking at an ATMEL SAM4E and I'm looking at the schematic checklist published by Atmel for the SAM4E and the schematic for the SAM4E-EK developer board.

SAM4E checklist
SAM4E-EK Design files (including PDF)

The checklist uses 10uH, 1R and 4.7uF for VDDPLL
And the developer board uses 56uH, 2.2R and 22uF for VDDPLL.

It would seem clear that checklist is a recommendation and the the developer board is a working example, but how does one select these values ?

Will the developer version work for all situations ?
When would it not work ?
For an arbitary board, what information is needed before hand in order to select the values for these components ?
Is it just experimentation ?(ie, during the prototype stage, just try different things until you get good results and then go into production with those?)


texts:
In this curve that shows the operating regions of the mosfet

What is Ve that is written Vgs +Ve ??


texts:
Over 485-interface slaves are connected as multi drop, physically daisy chain.

Those have built-in termination resistor, and the value is 120 ohm and no select switch for termination on/off.

So it makes termination value as 120hm if I connect 10 slaves.

If I want to make it as properly, just put 60 ohm resistor on each data Line(D+, D-)?

Master A(D+) -----(60 ohm)-----~~~

Master B(D-) -----(60 ohm)-----~~~

My guess is it can affect as like below:

60 ohm + 12 ohm(parallel connection from 10 slaves) + 60 ohm = 132 ohm

Surely, the best way is changing termination resistor, but I want to make it work simply.

Regards,
Jiwon


texts:
In my senior engineering design class for high school, my teacher bought a toaster oven and microcontroller and tasked my group to make surface mount digital dice kit for him to teach surface mount soldering to his digital electronics classes. He bought a couple kits from Beta Layout, but since the parts are discontinued, it is rather hard to reverse engineer.

I found a through hole soldering dice kit on spark fun (https://www.sparkfun.com/products/10212) and found that I could easily convert this to a surface mount kit, especially because the design is open source. However, I ran into an issue, the sparkfun dice rolls using a piezo assembly which is not practical for our kit. I was wondering if there were any professional electrical engineers that would be willing to help my group understand the circuitry behind a piezo, and how I might go about replacing it with a push button. (SPST?, SPDT?)


texts: How are molded-case circuit breaker trip ratings determined?

texts: Circuit breakers and fuses have trip curves which describe how quickly they interrupt various currents. How does the manufacturer of a molded-case circuit breaker choose one value of current to represent the product? In other words, how would you determine the trip rating of this molded-case breaker given its trip curve?


texts: How does a cube sat communicate with ground station with a 1w antenna

texts:
I heard that cubesat signals can be received with a hand held radio. Its confusing me that how a 1 metre antenna radiating 1watt energy can simply be received using hand held radios. I am designing a pico sat. I don't which antenna to be chosen to connect with rf transmitter section. And which antenna to be chosen for ground station.
Assume that my satellite is 250kms above ground level.


texts: How well does a Variac work for fan speed control?

texts:
I would like to run a standard multi-speed desk fan at a lower speed than its minimum setting. On Amazon, one reviewer recommended a variac for fan control, saying that it could adjust the fan from barely-on up to full speed, without introducing the hum that sometimes occurs with triac-based controls. As I understand it, variacs are simply adjustable transformers, which reduce the voltage fed to the fan (and triacs working in phase-controlled manner have a similar effect).

However, most fans are induction motors, and I always thought these had a weak response to voltage. For example, Figure 27 here shows that peak torque occurs around 70% of synchronous speed regardless of the applied voltage. I believe the operating speed must always be somewhere above this speed. If this is true, then the only effect you could get by adjusting the voltage would be to reduce the operating speed from ~90% of synchronous speed to ~70% of synchronous speed, at which point the fan would stall. This doesn't sound like enough variation to be useful (and is at odds with the variac reviews on Amazon).

Does this sound correct? If this is the case, then it sounds like my best option is to find a fan speed controller that uses a triac to cut the voltage for whole AC cycles, along the lines described in an earlier question. But that is a challenge, since most fan controllers that I've found don't include descriptions of their mode of operation.


texts: What is the use of transistor in the input side in TTL logic family?

texts: Second transistor will turn ON and OFF if input voltage is directly connected to its base terminal. Then why a coupling transistor is used at the input side of a TTL logic gate?


texts:
Novice, built a model for a popular wargame.
I built a modular tank using magnets for multiple variants from 1 kit.
I hope to add some LEDs (max of 20 3V)  & fibre optic lights on the vehicle and fibre optics for laser sights or panel lights etc.
For the fiber optics, I plan to make sealed boxes/packets with a grommet in each to allow a 3mm LED to be fitted, 1 for RGBW colours with the fiber optic cables for each colour ending inside the box/ packet.
All sealed up and blacked out to stop light leakage to the main body. Probably heat shink or acrylic resin seal. I'll need 2 of these 1 for main hull lights and one for the turret for the sights.
Been looking at a 4056 USB charging board to be hidden behind a panel as a way to charge the battery pack in the main body of the vehicle battery pack.
For the battery pack, I hope to be able recycle 18650 batteries from an old laptop battery pack for the project.
I don't know where to start, how to work out what battery power I'll need, if I can step it up if needs be. I've read a badly fitted LED can burn a system out.  Should I find something to protect the circuit?
Is it worthwhile buying pre soldered LEDs with resistors and leads already done?
I read that LEDs are best wired in series, I'll hope to use the magnets to transfer power between modules either to charge individual battry set ups (enough room depending on the size of the battery required, I have several batteries from rechargeable pocket items e.g. ear buds battery pack/storage) or simply to continue power to the lights running through the section (1 mag + ve, 1 mag -ve )
The space is approx 30mm x 70mm x 160mm of the top of my head, may vary 5 mm in some cases, I'll clarify if required. The LEDs are going to be fitted about the body.
The battery pack, charger, a fiber optics box, and power transfer (hopefully magnets where possible to maintain the modular set up of the model) will be in the base, the rest will involve wiring the LEDs to the various modules. Anyway thats the brief outline, please ask if I'm unclear.


texts: Safely build an earth to audio ground cable

texts:
I have a mixer that use a two poles connection to the mains (double shielded so it doesn't need earth).

If I connect my guitar (with the signal boosted by a battery operated amp) to the mixer I'll get the typical 60Hz noise. My guitar is grounded to my body but the battery operated preamp might lift the ground.

If I touch the mixer audio ground (touching the metal of any audio connector) while I play the guitar I solve the problem.

I also noticed that if at the same time I connect to the mixer other instruments that are not battery operated and that have their power supply connected to the earth I don't need to touch the mixer.

So I concluded that I need at least one connection to earth in my signal circuit. But using those additional instruments sounds like an overkill.

I was wondering whether I could build a cable that connects the mains earth to the audio ground of the mixer. Is it safe? Basically I would disconnect the live and ground of a normal male mains cable, and connect the other side to the ground of an audio cable. Is it safe?


texts:
I have 4 strain gauge load cell to calaculate actual weight.I want to use summing method for 4 output signals. I searched at internet for summing box schematic I found this pic
Now if V1 , V2 , V3 , V4 are the output signals for each load cell Why connecting them in parallel like that will make the resulting volt = (V1+V2+V3+V4)/4. ?


texts:
I'm analysing a particular schematic, an audio compressor: https://www.soundskulptor.com/en/proddetail.php?prod=LA502
The schematic is here: https://www.soundskulptor.com/docs/la502-schematic-03.pdf
My goal is not a specific issue with a product (I'd just ask the creator), but rather finding out how it works and learning in the process of doing so. Because it wouldn't make sense to just ask about explanation in one go, I decided to analyse it on my own and just try to ask specific questions whenever I feel blocked.
My first question is on the stage where input signal (line level, balanced) is transformed to the unbalanced one:

What I understand of it:

IN+ and IN- are the voltages carried by the input. They're essentially the same signal (sans noise) with opposite phases. That's just what balanced input is.

The transformer T1 is used to go from balanced to unbalanced. Because the left coil is connected to both sources, this means the changes of the voltage across it are twice as big as the original signal (either IN+ or IN-) so the output of the transformer is double the voltage of the input (and here is where noise-cancellation happens).

My questions:

What is the role of the capacitors C1, C2 and C5?
What is the difference of the ground connected to C5 and the "empty" (unlabelled) triangle under right coil? If that's just some schematic peculiarity and not general knowledge then it's fine, I  might reach author, but I think this has to do something with the fact the transformer isolates those grounds, so they're not common.
What's the role of the R1 and R2 resistors? I'm only intereste in the "output" of the transformer stage, so the unbalanced signal - would that be a signal denoted by the voltage across R1 ? And then R2 would be just part of the further stages which are not the part of this question?

Hope this is fine to ask questions in such manner here!


texts: The accurate time latency for 'lw' instruction in a single-cycle datapath

texts:
I want to calculate the cycle time of a single-cycle datapath. Then from the course, I know the time should be the execution time of the longest instruction, which is 'lw' in MIPS.
So I try to calculate the time latency for 'lw'.

I think the longest path/time for 'lw' woud be:

PC -> I-Mem -> Read-Reg -> ALU -> Data-Mem -> Mux(to select Mem to Register) -> Write-Reg

(In the path, I think the mux to choose read-register1 or write-register, sing-extend for immediate value and mux to choose read-data 2 or immediate value are all ignored, since the circuits are in parallel, they would take less time than other parts in parallel.)

But when I tried to find some solutions, there are some different answers, but none are identical to mine.

Someone said, the time/path should be:

PC -> I-Mem -> Read-Reg -> Mux(choose the input of ALU) -> ALU -> Data Memory -> Mux(select Mem to Register) -> Write-Reg

And some other versions:

PC -> I-Mem -> Read-Reg -> ALU -> Data Memory -> Mux(select Mem to Register)

But without Write-Reg

I really don't know which is really the right answer. Can anyone help me to solve this problem?


texts:
I have very little electrical knowledge. So here is my question. I need to test some wiring harnesses if they grouped like it should be.

There is 70-80 points. differencing on the harness, these points are connecting together.

For example:

red cable left side point number 20, right side point number 32. So I will check if these two points connecting properly.

I want to use a Tablet PC for this purpose. So I need a converter that can send these 70 points' signals through USB to Tablet.

I do not ask for designing whole process. If you can point me to some direction, I will research it.

I forgot to mention. The converting have to be for both sides. I mean Tablet will tell which points it must check and then tablet will check the response signals.


texts:
Our compliance agency believes that it is all too likely that a 50 V power adapter is used instead of our 5 V power adapter. Regulation wants a fuse which can protect from 50+ V, and not allow 15 W dissipation in any case.

I am aiming for an IEC/UL approved 500mA fuse, but for overvoltage protection the zener diodes are a bit iffy. The idea is to short circuit any overvoltage to blow the fuse. However the zener diodes will be subjected to a very high power say 5.6 V*1 amp=5.6 W for at least some milliseconds. The power rating of these SOD323 is 300-400mW. One datasheet showed 40W for 100us.

Does anybody have experience with this kind of passive protection? The equipment is solely expected to break and not be repaired and needs to meet IEC/UL standards. I have no room for crowbar solutions.


texts:
I need to control 3 devices, via three relays. I wish to use a 4-relay/usb controller to do this.

I currently use this device but I now need three relays:

http://www.barix.com/Barionet_100/511/

My Power supply is operating at 24 VDC, with the ability to supply 2A and 120W. This device powers the three devices without any problems.

The devices draw less than 8 Watts each as far as I can ascertain.

What should I look out for when choosing suitable relays?

Any tips on suitable devices? I need to control the device from my Python code.


texts: Which is the best way to produce electricity?

texts:
To generate electricity from a DC type motor generator which of the following is the best way?

1) rotating coil wire in fixed magnetic field

2) rotating magnets in fixed coils setup

Which produce more electricity. This is for a simple science project.

Considering same rpm in both cases and same type of coils and same strength of magnets used.

Thanks in advance...!


texts: run BLDC motor WD-1465FD of LG washing machine with frequency inverter Sunfar E300-2S0022L

texts:
I have a BLDC motor WD-1465FD of washing machine LG . My question is can I drive the  bldc motor (directly) with inverter Sunfar E300-2S0022L.

I tried all VFD parameters but no good results.
 It only starts on 200v but after 30 sec. starts burning.


texts: Can you make a waveform asymmetrical with the 555 timer?

texts: Using a 555 timer how do we output a biphasic square wave instead of a monophasic? Is there any way to make it asymmetrical? If not are there any other devices or circuits to use to make an asymmetric biphasic output waveforms?


texts: Charge a 12V marine/boat battery with AC

texts:
need to build a diode bridge to recharge a battery (car/boat type) from a boat engine that gives 12V AC.
I thought of doing something like this:

simulate this circuit – Schematic created using CircuitLab

Only I can't know which diode I have to buy and which capacitor to take.

Can you help me?


texts: Understanding how a NPN transistor works

texts:
I have been trying to understand how an NPN transistor works, specifically in the case of a photo-transistor.
As far as I can tell, it should be something like this:

I don’t understand how current can flow between the Base and the Collector since the Collector is n type and is connected to positive terminal, which would surely make the BC reverse biased?
The base in the diagram would be connected to a photo-diode, allowing current to flow when light levels reached a certain intensity.


texts: What will be the output voltage when 9 volt given to LM7812

texts:
I'm thinking of using 9 - 25 volt, 1750mA constant current DC input. In the circuit, there is LM7812 after A  component in order to decrease voltage to 12V . My tests shown that when Voltage Is above 12V up to 28V, things look not bad. Output Voltage Is ~12V

But I was wondering that what will be the output voltage if input voltage is less than 12, Ie, 9.9 Volt.

My another question: What will happe if I give voltage from output to input to LM7812? Will it work? will there be flowing current? or will It behave like A  diode?


texts: Type bit does not match with the integer literal while converting integer into bit_vector

texts:
In VHDL, is there any way to convert an integer into bit_vector of length of 14?

Currently, I am first converting the integer into std_logic_vector and then into bit_vector.

for i in 0 to 5 loop
    x_std(i) <= conv_std_logic_vector(x_int(i),14);
    x_bit(i) <= to_bitvector(x_std(i),14);   --here comes error
end loop;

In behavioral check syntax, following error comes while converting std_logic into bit:

Type bit does not match with the integer literal

I am using following libraries, ieee.std_logic_1164, std_logic_arith and std_logic_unsigned.

How can I do this conversion without an error?


texts: Electronic load, Problem turning MOSFET on

texts:
I am trying to make an adjustable dummy load to test a 12V supply, I’m having trouble with the op-amp feedback circuit.
Attached is a simplified schematic. I have tried lots of things and stripped it down to this.

Basically when +In of the op-amp is 0V, the output of the op-amp goes to the negative rail. In this case the negative rail is 0V, but when powered with a +/-5V supply, the output goes to -5V. In this state the MOSFET is fully off

When I add just a tiny bit of positive voltage to the +In of the op-amp, The output shoots straight into positive saturation and goes as close to the positive rail as it can get (about 3.7V) and stays there no matter how much voltage I give to the +In. At this point the MOSFET is on, and allows approximately 250mA to flow through though.

Any ideas on what this could be?

Things I have tried:
- removing R6 and Q1 and connecting R8 to -In. At this stage I get a normal voltage follower.
- Changing the FET
- Raising the resistance of R6

On a side note, there is one way that I can get the load to be variable, and that is by removing the heat sink from the MOSFET. I have only done this for short periods of time.


texts:
This schematic triggers the relay when current exceeds 1-3A:

I want to do some modification in this circuit;

How can i reverse the circuit working to trigger the relay when power connected to INPUT and disconnect it when current exceed the set point?

How can i decrease the minimum current set point from 1A to 500ma or lower?

Also i couldn't find IC CA3140 but the seller said CA3130 should work, appreciate it if someone confirm this.

CA3140 datasheet

CA3130 datasheet


texts:
I think of buying an AVR Dragon or an AVR JTAG ICE MKIII. But before I do this, I need to know what side effects the reduced debug frequency has on an ATMEGA328P while debugging. I make heavy use of UART, Timer0 and Timer1 at a frequency of 16 MHz.

In particular the UART should work while debugging. Is this ensured?

Which debug device do you prefer? Does it work with Atmel Studio 6? I am fimiliar with the PicKit2 as a debugger.


texts: XBee wireless module not responding any more

texts:
I bought an XBee-PRO S1 .. I built its  serial explorer to be able to configure it through the PC, I’m using X-CTU to  configure and test it at first it worked well,I made test/query successfully  many times I tried to write a modem configuration to it .. but each time ended  with a failed message, through this the chip was still responding to the  test/query, and the terminal command "+++", but trying to configure it 3 or 4  more times it stopped responding, well, I figured I was wrongly configuring it,  as I didn't use the reset to reset the chip before writing the new configuration  to it .. then i fixed my explorer circuit, and tried using a reset button, it  worked one or two times, and a progress bar appeared, but the process failed too  .. now the XBee isn't responding any more for any of what I did before .. I searched, and found many people facing the same problem ..

This problem happened with two modules in row .....

In short “I write +++ it responds OK , If started to  configure say AT..anything , It stops & no respond , if I tried “+++” again  .. no respond , it’s even not recognized by the X-CTU” ...

I hope  I can find help about what should I do to recover this XBee, and what mistakes  did I do so I can avoid them in future .........

Update #1:-

I contacted the manufacture digi(dot).com

Support:
In order to change the  firmware on the radio, the DTR and RTS lines are required. To resolve your  issue, I would recommend either acquire one of our XBIB interface boars or you  follow the steps outlined at http://www.youtube.com/watch?v=fxOqQZD-oaM  once the DTR and RTS lines are connected using the proper level  shifting.

As described in the  product manual, the radio is a 3V device and is NOT 5V or RS232 level tolerant.  You need to use a level shifter between the radio and the PC or some other Non  3V CMOS level device. Otherwise you will damage the  module.

You  can see a sample schematic of our XBIB interface boards buy going to http://www.digi.com/support/kbase/kbaseresultdetl?id=2118.  However if you are not familiar with level shifting, I would strongly recommend  acquiring one of our XBIB development boards as it will give you a known  starting point to work from.

Me after the update :

Of course nothing worked from the support !

The behavior I noticed that :-

When I press the reset for a while (4 ~5 ) seconds , the CTS line in XCTU is lighted up(Green) ..... So ?


texts: I am trying to connect the 47 ohm line from the 555 timer (refer to first picture) to either A1 to turn the motors forward or A2 to reverse the motors. Problem is I don't know how to, with two inputs, have 3 states. Power to A1, A2, or neither. The provided diagram I have tried works if I have 0 resistance on the io pin and doesn't work if I have any resistance but will short it.


texts: Differences between Cortex-M4 Cortex-M7 and Cortex-A5

texts:
I want to make a simple IOT project for my home and I'm searching for a mcu to start with. I was raffling through the web site of a few popular distributors and I found that some Cortex-M4 are much more expensive than Cortex-M7 which are more powerful though. Also I saw that some Cortex-A5 are cheaper than some Cortex-M7.

I can understand the differences in terms of performance and architecture, but if someone wants to start developing a board based on some of the MCUs that mentioned above for building its own projects, what statements must be considered to match our demands?

To be exact, why not choosing a Cortex-A5 if it's more cheaper and powerful instead of a Cortex-M7?


texts: How to interface a passive inductance sensor output (audio-level signal) with Arduino?

texts:
Would like to interface two passive magnetic-inductance sensors output (audio-level signal) with Arduino.  The sensor circuit comprises of two wire-wound sensors and has no power.  It generates it's own voltage when eddy currents are created by a nearby object passing by.  The two sensors have a stereo audio jack with a common ground. When connected to a laptop mic-port (3.7V power) and read by Audacity the signal is centered at zero volts resting.  When an object creates eddy-currents the signal is a nice AC sinus wave from 0V to 1V peak and down to -0.75V peak and back up to the zero volt line.  (actually two sinus waves one after another, but illustrated here only one)

I would like to make a digital HIGH and LOW signal from the AC audio level (-1V to 1V centered at 0V) sensor output that Arduino can read on a digital pin.

The other option is to have Arduino read the sensor value on one analog pin with the INTERNAL voltage reference set at 1.1V.

I know that Arduino cannot have more than 0.3V negative voltage going to it and cannot exceed 5V either.  What would be the best way to proceed? How can I condition/amplify the AC eddy-current audio-signal(s) into a reliable digital HIGH?  I do not need any audio, just want to detect the HIGH.  Or how can I condition the signal(s) into an analog value that the analog-in pin can read? Thank you for any advice.


texts: Designing a AC Snubber circuit for 2 hp using AC snubber

texts:
I am trying to control my 2 hp 240AC single phase motor with help of an arduino. Right now it is controlled via a contactor with 220-240 AC coil input voltage with help of NO and NC switches.

Following is what i am trying to achieve: Pardon my poor skills

Following is the 10A relay i am planning to use to control the contractor:

Following is the snubber circuit I have come to accept to the best of my abilities.

In the snubber circuit I am using 2000V 104J capacitor: Following is the image:

From what i could gather I am planning to use 20D271K as the varistor. Following one
Varistor

My question is will this work? I apologise for poor circuit diagrams. I will get an electrician to install these. The motor will be switched on 2 times a day for roughly 30 mins.

Help is highly appreciated.


texts: Suitable replacement for this big aluminium can capacitor?

texts:
In the picture you can see the type of capacitor im dealing with. The specific one is actually the third in the picture, but I took the picture of the easier to see one. The one that has failed is a 5000MFD segment, and smooths out the positive ripple from a 4 diode AC rectifier.

The whole thing is part of a electric organ.

Would this sort of thing be a suitable replacement ? (disregarding the capactance difference)
http://www.jaycar.com.au/Passive-Components/Capacitors/Electrolytic/4700uF-25V-RB-Electrolytic-Capacitor---105oC/p/RE6244

Or does it need to be big and chunky like in the picture? (or is the one in the picture like that because it is old?)


texts: Inform microcontroller that the analogue circuit is powered up

texts: Basically, I want to pull-down the microcontroller pin if some analogue circuit is powered up. The analogue circuit power is 9V, 1.6A. The idea I have is to use something like IRLZ24N MOSFET, connect gate to the analogue circuit via resistor, connect microcontroller pin to drain and source to the ground. When analogue circuit is powered, it will trigger MOSFET and pull down the microcontroller pin, configured as pulled-up input (microcontroller itself is powered via USB). The question is whether there is a better or more correct solution than I suggest above.


texts:
I'm using this chip antenna with a 868MHz radio (RFM12B): http://www.johansontechnology.com/datasheets/antennas/0868AT43A0020.pdf

According to the datasheet's mounting considerations there's a trace that's supposed to go out from the antenna. What is the reason for this? Due to tight space i'd have to drop this with a via to the bottom of the board and do this there, is this ok? I guess the via will have quite a big impact on the RF signals. If not, can i do something "similar" with a same length but slightly different shape? Or is it better to leave it out entirely? Are there other ways of doing this to achieve a "decent compromise"?

Related to this the feed line should have 50 ohm impedance. According to this: http://www.eeweb.com/toolbox/microstrip-impedance I've calculated the trace width to be about 115 mil. This seems very big.. I'm using a regular 1.6 mm FR4 board with 1 oz copper. Am I missing something?

Also I'm assuming this should definitely not have sharp corners so the trace is rounded
(cannot be perfectly straight as in the datasheet), right?


texts: Which transistor to drive 24V door strike with Raspberry Pi?

texts:
I want to drive a door strike at 24V with a Raspberry Pi. The door strike needs 150mA. I think the current that a Raspberry Pi can drive on one pin is significantly weaker than for example an Arduino, so I really don't want to pick the wrong transistor.

Transistor data sheets still often sound like black magic to me. I was previously planning on using a ULN2803A darlington array, but since I really only need the one output that would be overkill.

I'll add a flyback diode as well since I don't know exactly what the mechanism inside the door strike is, it could be a coil/solenoid of some sorts.


texts: How can I build hall sensor based PWM dimmer?

texts:
So there is a hall sensor on a scooter throttle and it's missing the speed controller. I tested the sensor and it does work. 5V in, and with full throttle it's about 4V and 0.9 when closed.

I want to make a pwm 'dimmer' (actually a motor speed controller which are similar) but I can't find a way except using arduino to measure the analog volts and calibrate it into a 0-255 value which I did last night.

But can someone tell me if this can be done with an op amp and 555, and tune it to have 0-100% duty cycle? The 0% is important as the motor shouldn't start without throttle, but also should be able to reach near 100%.

Thanks


texts: PWM signal not visible upon increasing the scope time base

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I am capturing 2 different PWM signals.

The frequency of first PWM signal is lower when compared to the second one.

Please check the waveforms.

All the waveforms are taken of the same two signals. But upon increasing the time base, the second high frequency PWM signal vanishes like shown below.

Why is this happening?

Do I need to change some settings on the scope?

Oscilloscope : HDO6054A Teledyne Lecroy

EDIT :
Issue solved if I use a different scope (Tektronix MDO3034)


texts: Understanding use of accelerometers to measure angular (rotational?) accelerataion

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Imagine this: A rod is attached at one end to a rotating shaft. So, as the shaft rotates from 0 to 90 degrees back-and-forth (in the xy plane), so does the rod. My goal is to measure the instantaneous acceleration of the rod while its moving. I have a few 3-axis accelerometers, but I feel like I'm really confused. I guess I'm not really understanding how accelerometers can work best in this scenario because it's not really a "linear" acceleration. I think its a rotational or angular acceleration (are those the same?). Also, even though the rod is only moving in the xy plane, since it rotating, doesn't that mean that it's rotating about the z-axis? Although I'm assuming I only need data in the x and y dimensions.

I guess here are my more specific questions: Should I use more than one accelerometer here? If so, where would be the best locations to mount them? How should I mathematically combine these data to give me an overall acceleration (perhaps just sum the squares, and then take the square root)? And lastly, let's say the rod ramps up from 0 degrees, stays at a constant velocity, and then ramps down. How should I expect the data to look like in this simple case?

I'm hoping someone can shed some light on the use of accelerometers in this particular scenario. It got to the point where doing more research online has only confused me more, so I'd really appreciate any help I can get here.


texts: Why does dropping my laptop's AC adapter in the floor make it work again?

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For several months now I've had trouble getting my AC adapter I use to charge my laptop to work. It's one of those typical looking things, with two ends and a big bulky rectangular thing in the middle.

No matter how much I've tried to fiddle with both ends to make the adapter work, like replugging it to the laptop back and forth, it never works. On the other hand, I've had a 100% success rate of getting the adapter work with the following method:

I plug it in to the laptop and to the electrical outlet, grab the rectangular bulky adapter thing and drop it straight down on the floor from about a 15 cm (5,9~ inch) height. As soon as the adapter slams against the floor, it works again until the next time I unplug it from the electrical outlet.

What's the science behind this, why does this work?


texts: Help me interpret this part of the USB + Power Standard

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It's the last two sentences of this section:

What does the last sentence mean exactly? And how do I apply it?

Basically I am building a USB + Power peripheral that will convert USB to RS-232 and drive a display that needs more than the 500mA you get from regular USB, hence we are using USB + Power. You can find the full standard here:

http://www.poweredusb.org/pdf/PoweredUSB_v08g.pdf


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In designing a Common-Source amplifier, why is the inclusion of a current source considered most popular method?

Consider a single stage CS amplifier where I bias the gate with an appropriate DC voltage and derive the Id through Vdd. Is it considered a good design? In doing so, I am replacing my current source circuit with a Vdd from which i can derive the drain current.


texts: Where can I get a high temperature humidity sensor for  temperatures up to 700 or 800 degree Fahrenheit (~ 370 or 425 °C)?


texts: Why does this dual monstable not function as such?

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I have wired up a simple circuit here to test the cmos one-shot multivibrator.
The top half of the chip seems to work but the bottom half does not. I even replaced the chip with a new one and I get the same results.

R1 is 27K, R2 is 10K, and the rest of the resistors are 1K each. All caps are 22uF, and I'm powering the device with 5VDC.

When I press the key (raising pin 12 to +5V), LED1 functions by lighting up for a brief moment correctly.

When I release the key, I expect LED2 to do the same but for a different amount of time, but instead, it stays on and never shuts off.

How do I fix this?


texts: What do you call a rotary switch that does not have a max turn degree?

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Exactly like on the Logitech G35 or Logitech F540; not a rotary switch because those have notches and a physical limit.

Instead of turning clockwise, or counter-clockwise, you rotate it 'up' or 'down'.

Or a switch that pretty much just triggers a digital HIGH when it hits a notch I guess and can keep going.


texts: Wheatstone gauge factor calculation?WII load cell

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Currently working with the WIIFIT or WIbalance load cell. For some reason everybody wants to work with these load cell. However, there are no actual datasheet of the load cell used in the device. There are datasheet of imitation load cell(MLC714N), replicas of the load cell of the WII. But they do not have the same sensitivity.
Wondering if anybody has ever accurately calculated it, or knows how to do this? I am thinking to put excitation voltage and use rated weights and calculate the gain(Vout/Vin). Should give me an idea of what the sensitivity of the wii load cell is. However. I am not sure.
MLC714N load cell spec(imitation load cell for the wii)


texts: Labeling terminals and junctions in a BJT

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The following schematic (sorry for the poor picture quality) was part of a question which asked to calculate \$\alpha\$, \$\beta\$ and \$V_C\$ for the given circuit.

simulate this circuit – Schematic created using CircuitLab
I assumed the base current to be the current through the \$100\text{k}\Omega\$ resistor and obtained the answer. However, why is this the base current? More specifically, what does the line with an empty circle (the terminal symbol) really represent? My understanding is, it is simply used to represent the label the voltage at junction/node. Is this correct? Or, is the terminal part of a bigger circuit. If so, shouldn't the base current be obtained by apply the current rule at that junction?
Thanks for the help.


texts: RC oscillator model in attiny microcontroller

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I was reading in the datasheet for the attiny85 that the internal RC oscillator can be callibrated to run at different frequencies based on the value in the OSCCAL register. (Page 194 graph: RC Oscillator Frequency vs. OSCCAL Value) I would like to learn more about how this type of oscillator works at a hardware level, so I was wondering if it could be ordered seperately from the attiny85 or if there is a similar one? Thanks!

Edit: If an exact model number isn't known, then some recommendations as to what to look for would be appreciated, too...