texts: Protect Jack plug circuit against transients and constant voltage

texts:
I have a question regarding input protection of a circuit. I have been looking all over the internet for awnsers, but can't seem to synthesize the right solution for my problem.
To make my question as clear as possible I simplefied my circuit to the following:

I am building a modular system that uses a jack connection to pass through a voltage signal. This signal will pass through the middle of the jack plug (A_1). The sense pin leading to S_1 will detect whether the jack is fully inserted. The voltage singal being send through is the voltage over a potentiometer.
Now there are two thing I want to protect the analog signal (A_1) and sense signal (S_1) against. This being ESD (Electrostatic discharge), and a constant too high voltage. My system operates within a voltage range of 0 to 5V. The solution for ESD seems rather obvious, I want to use a LittelFuse TVS diode for that. But there is a possiblitity of a wrong jack connector being inserted and a constant 12V signal passing into my circuit. From research I found out that this TVS diode won't be able to handle this constant higher voltage and I need additional protection. I thought about using a TVS diode and Zener diode in parralel but according to the internet this was not ideal either, since my capacitance will increase and I could have more current leakage.
So I was wondering if any of you guys had a solution or case related to this problem, that can send me in the right direction. Hopefully I explained my question clearly, if not, make sure to shoot me a message.
Thanks in advance.

Edit: since it was unclear how the remainder of the circuit looked I wanted to elaborate a bit futher.

I want to have  32 of these jack connections on my controller (it will become a modular midi controller) The 2 signals lead to two 4051BE multiplexers, from these multiplexers signals lead back to the ATmega32U4 where I read the voltage over the modular parts inserted (A_1) and I read whether jack plugs have been fully inserted (S_1). The modular parts that will be inserted on the midi controller will contain potentiometers. I want to add protection near every of the 32 inputs on my modular midi controller since it is prone to wrong inserts or external disruptions in usage. Hopefully this makes my problem a bit more clear.


texts: Strange ringing/oscillation in guitar tube amp

texts:
So I finally finished building my guitar amp.
It sounds great, except for one thing that occurs when gain is too high.
What happens is that when I turn one of the preamp volume pots high enough strange ringing occurs. The funny thing is that on the other channel (which is identical, because it is a stereo amp with switchable guitar add-on, so you have two totally independent and identical guitar channels), no such thing happens.
So I made a quick analysis with sine wave as input.

Isn't I a beautiful slightly overdriven sine wave?
And now look what happens when I turn my preamp volume pot just slightly more:

And even more:

Switching tube doesn't help, so I would rule out bad tube.
Here's the part of the circuit that most likely causes the problem (deduced by checking what pots change this weird effect):

(yes I use power tube in preamp, because I like power tube distortion and I don't like playing very loud for most of the time).
I am pretty sure that oscillation must come from this part, because the 'preamp volume' pot has certain position, beyond which the oscillation occurs regardless of position of other pots (actually even regardless of the volume from previous preamp stage), and increasing master volume doesn't change anything, it just makes the singnal louder.
At first I thought that amp is osciallating in 200khz region or something like that (and I'm unfortunately unable to check for sure because I don't have oscilloscope), so I added capacitor in negative feedback loop to fix phase shift for large frequencies, but nothing changed. And I think if it was RF oscillation, master volume would change somethinhg and it doesn't.
Anyone has any idea what could it be? Perhaps it is a known issue?
Please tell me if you need more information about the amp.
Here are some photos:


texts:
I'm working on a Video processing project with Vivado 2015.2 on a Zynq device.

My block design starts to get huge and hard to read. As I have several times the same pipline implemented, I would like to make some kind of submodule (take some IP and connect them together in a separate block diagram). Is it possible to do that? Can I use a (sub-) block diagram several times in the main diagram?


texts:
I've just finished to solder this little circuit on perfboard and now I realize that the board is bent:

I am pretty sure that the board was flat when I purchased it. What may cause this bending ?

excessive heat ?
there are some long solder bridges in that part of the board; is it possible that the solder shrinks when getting solid/cold ?

Edit: Those boards are sold as "bakelite" boards at a local shop. I'd say they are low quality boards (eg. the solder pads tend to come off easily)


texts: How to make a simple negative power supply

texts:
I want to experiment with amplifiers but I need a negative power voltage source.
I looked for some circuits but as far as I found they either are not simple & reliable or  require an IC.
Is there any simple way to get negative power supply without using a railsplitter IC or AC power source?
Also I read about these 'virtual grounds' but I couldn't figure it out. Is it like ; we choose a positive voltage point as ground so technically the real ground is more negative relative to positive point we chose?

This one works well but needs an AC power supply and high capacity and voltage capacitors and they take a lot of space but so far best I could find.

This one looks simpler and doesn't need an AC source or big capacitors but either I can't understand how it works or it doesn't work that well.
Edit: If what I want is not possible, can you recommend some ICs for it? I can order them from abroad because they're not common in my country and this why I asked about circuits that don't involve them in the first place.
Edit I think I was not clear about what I want:
I specifically don't want a circuit which requires an AC power supply because yes I know it's so easy to make a circuit like that.


texts: In a DC circuit with one battery and one resistor, why does the voltage drop remain the same irrespective of the value of the resistor?

texts:
DC Circuit#1: I have a 10V battery connected to a 10 Ohm Resistor. Therefore, the current will be 10/10 = 1 Amps

DC Circuit#2: I have the same 10V battery connected to a 5 Ohm Resistor. Therefore, the current will be 10/5 = 2 Amps

(Assume the conductor wire does not have any resistance at all)

What I do know:
The negative terminal of the battery produces a repulsive force on the electrons. This force travels at near the speed of light. When the electrons enter the resistor, they start colliding with the lattice. The kinetic energy of the electrons are converted to heat energy which is dissipated. The drift velocity of the electrons slow down inside the resistor. Now this slowing down effect is propagated backwards because of which the entire drift velocity through the whole of the circuit attains a steady state. In Circuit#1, this steady state drift causes a charge flow per unit time, of 1A. In Circuit#2, the resistance is less, so the steady state drift is more, so the charge flow per unit time is 2A. Because the whole of the circuit has the same steady state, an ammeter connected anywhere in the circuit shows the same Ampere reading. I completely get this 'same current everywhere thing'. My question is more about the potential drop.

My question:
In Circuit#1, the resistance is more (10Ohm). This means that the electrons encounter more collisions while travelling through the resistor. So the electrons lose much energy by the time they come out of the resistor. Compare this to Circuit#2, the resistance is less. This means that the electrons collide less. Agreed that the electrons lose energy while travelling through the resistor, in Circuit#2 also. But my point is that if you compare the electrons at the point of exit point of the resistors, between Circuit#1 and Circuit#2, the electrons in Circuit#1 have lost much more of their ability to do work because they were slowed down more by the collisions, than the electrons in Circuit#2. Then why ,in the whole world, is the potential difference measured across the resistor the same(10V), in both the circuits?

If you keep on increasing the resistance, I understand that the current will keep on decreasing. But why doesn't the potential difference between both ends of the resistor change? The energy difference of the electrons at the entry point of the resistor, and the electrons existing the resistor will definitely depend on what was the amount of collisions that happened in the journey through the resistor. So why doesn't the potential difference also depend on this?


texts: How do I wire a TMC2130 stepper motor driver to an Arduino UNO in order to control it?

texts:
I simply want to control a stepper motor with an Arduino and I need the TMC2130 to ensure it runs very quiet. I've done a lot of searching and somehow can't find how to actually wire it to an Arduino and a power source.

I can find Arduino libraries and sample code galore though. I have seen wiring diagrams but they only use the TMC eval kit which I don't want to buy.

Is a TMC2130 and Arduino all I need as far as ICs or boards go? Anyone have experience with this?


texts: Question about a point made in Art of Electronics

texts:
In the Art of Electronics (Second edition), Section 2.02 (Transistor Switch), the book gives a circuit diagram

with a bulb rated 10V, 0.1 A, connected to the collector of a NPN transistor. The other end of the bulb is connected to constant voltage +10V. Then when current flows into the base, it says that we cannot blindly multiply \$I_B\$ by \$\beta\$, as a current of 0.1A would drive the voltage through the bulb to 10V, making collector voltage 0V. It also says that the collector voltage goes as low as possible, but still stays something
around 0.05 - 0.2V above ground.

But then it comments that the bulb would glow in this case. But how? The voltage drop across the bulb is 9.95V at max, which is less than the rated 10V. Why does the bulb glow up?

Also, even if I assume that such low voltage differences do not affect the temperature of the filament, how does the book say that 0.1A would cause a 10V drop? I take the rating of the bulb to mean that when the bulb is glowing, a 10V drop would cause 0.1A (as resistance is almost fixed by the fixed temperature at that time). But how can this be stated even before the bulb is glowing?


texts: Closing two circuits from one button press, with a delay?

texts:
From one button press, I want to momentarily close two circuits with a small (< 1s) tuneable delay in between.

What term should I google for to find a schematic?

(For clarity, I want to press the normally-open momentary pushbutton once, which will close one circuit momentarily, then after a delay—the length of which is adjustable via a trimpot, for example, up to about 1s—momentarily close another circuit.)


texts: Why can't I successfully send messages over RS232?

texts:
So the past week I have been working on getting UART messages sent from a STM32F407 and reading it on my laptop through a ugreen RS232 to USB cable using termite.
I have used STMCube to generate code and add to it by reading the relevant instructions at the top of the "stm32f4xx_hal_uart.c" file (and watching plenty of videos and reading online).
I have checked the transmitted message on an oscilloscope and it matches its ASCII representation.
For example I send 'Q' which is 0101 0001, I receive 'W' which is 0101 0111. The reading on the scope shows:

Termite output for the same signal as displayed on the oscilloscope.

I have confirmed baud rates/parity/HWcontrol are matching on termite and in my code.
To receive correct character I have tried lowering and increasing baud rates.
I've tried different character sets to try to find a pattern which causes wrong characters to be displayed.
Additionally I have tried different terminal such as on Putty or Teraterm.


texts:
How can a frequency divider for high voltages be implemented? Is it possible to make it cheap and compact?

An application would be to mount it between the output of fluorescent lamp ballasts (delivering 20kHz at a high voltage above 500 volts) and the input of the lamp and change that frequency to control the flickering frequency of the lamp.


texts:
I would like to sniff data on an SPI bus running at a clock rate of 6 MHz. I would like to use the Bus Pirate V4 for this task. The sniffing itself is supported up to 10 MHz, the problem is getting the data on a PC in real time.

The BP page for the USB connection (V4!) says:

  Max speed is 12 Mbps, but a realistic limit is 1 Mbps.

Can I just set the UART speed to 6 Mbps in Windows/Linux?

I have used a 1 Mbit baudrate before, using a 5€ China UART<>USB converter without problems. Since the BP has the USB hardware built-in, I don't see why the realistic limit would be 1 Mbit/s...


texts:
I was going to use the LY330 or the LY530 from ST Microelectronics and they should do the job very well. However, due to the stupid US Export Restrictions, Digikey won't sell any to me (I live in Australia).

Are there any recommended gyroscopes that I can buy (Z-axis) that are easily sourced (no export restrictions from digikey), offer ranges of at least 300 deg/sec (don't care if it is digital or analogue), and are highly accurate?

Thanks.


texts:
I was wanting to use the MK-R for a project of mine but after consulting the datasheet I  burned up my first 10$ LED and wasn't sure why.

I had an LDO providing 11.5V anode to cathode via gator clips. I ran the anode line through my multi-meter and verified it was pushing 450mA before the LED smoked and burned out (stayed lit for about 15 sec).I was trying to disconnect the clips real quick as I saw the smoke it was indeed burning extremely hot. I'm wondering what I am missing here from the data sheet as these LED's should take 1250mA with a Vf of up to 14V and dissipate 15W of power. Am I not understanding something in datasheet correct?


texts: How to assign peripherals to physical pins for STM32 MCUs?

texts:
I'm using STM32F series MCUs with a RTOS. Since the OS provides API to configure the peripherals and their physical output assignment, I didn't pay much attention in the past. Now I want to have full control of this type of hardware configurations.

The point I've confused is that, according to datasheet, a physical pin might be in one of 3 different modes (for STM32F103, in this case):

Main function (after reset)
Primary alternate function (Alternate function/Default)
Remapped alternate function

"Main function" is easy to understand. However, for example, one primary alternate function can be assigned to 3 different peripherals for the same physical pin:

Question

Where are we configuring if PA2 is used for whether USART2_TX or ADC12_IN2 or TIM2_CH3?


texts: How can I demonstrate magnetic and capacitive coupling on an STP cable in SPICE?

texts:
Below is a floating source is coupled to a instrumentation amplifier via a twisted shielded cable:

For the sake of showing effects to some people by simulation, I want to add a common mode voltage, a magnetic coupling effect and capacitive coupling effect to the cable to mimic the real scenario. So far I tried to add a common mode as below:

How can the final circuit be modified so that magnetic and capacities coupling also demonstrated?

Edit:

Is this model correct:

Edit2

Edit3

Edit4


texts: Help finding PWM IC with marking on device 'FA=606'. Package of device is SOT23 - 6

texts: I found this 6 pin PWM IC in one of the SMPS. I am unable to find any of its details on Google. I am requesting if anyone could help me finding the device name. The marking is something like FA=606 or 1FA=606.


texts: How to control the speed of rotation of a servo using a potentiometer?

texts:
I'm trying to write a program using BASIC to turn a servo 180 degrees back and forth, and to use a potentiometer to control the speed at which the servo turns. I have a code, but when I run it, the servo freaks out and starts twitching in one spot, and I don't know why it's doing that or what's causing it. Can someone explain to me why it's doing that, what's causing it, or a way to fix it?

' What's a Microcontroller - ControlServoWithPotUsingDirectives.bs2
' Read potentiometer in RC-time circuit using RCTIME command.
' Apply scale factor and offset, then send value to servo.
' {$STAMP BS2}
' {$PBASIC 2.5}

counter VAR Word

rcPin PIN 5                                       ' I/O Pin Definitions
servoPin PIN 14

scaleFactor CON 15                               ' Constant Declarations
offset CON 1
delay CON 10

time VAR Word                                     ' Variable Declaration

PAUSE 1000                                        ' Initialization

DO
                                                  ' Main Routine
 HIGH rcPin                                       ' RC decay measurement
 PAUSE 100
 RCTIME rcPin, 1, time
 'time = time * scaleFactor                       ' Scale scaleFactor.
 'time = time + offset                             ' Offset by offset.
 'PULSOUT servoPin, time                           ' Send pulse to servo.
 'DEBUG HOME, DEC5 time                            ' Display adjusted time value.

 FOR counter = 300 TO 1100 STEP time
   PULSOUT servoPin, counter
   PAUSE 7
   DEBUG DEC5 counter, CR
   DEBUG DEC5 time, CR
 NEXT

 PAUSE 10

 FOR counter = 1100 TO 300 STEP time
   PULSOUT servoPin, counter
   PAUSE 7
   DEBUG DEC5 counter, CR
   DEBUG DEC5 time, CR
 NEXT

LOOP


texts: Can this be anything other than a resistor?

texts:
I have been messing with an old valve amp and have replaced the filter caps and a couple of resistors that were a little out of tolerance. The component in the picture does not look the same as any of the others and, if it is a resistor, seems to be out of tolerance by a couple of orders of magnitude (my reading is 1.2M, whereas the colour bands seem to indicate 95R). The others were only a few percent out. I just wanted to check it really was a resistor before replacing it...

Thanks!


texts: A low cost method to perform Eye-Pattern Testing on 100 MBit and 1 Gigabit Ethernet Transceivers

texts: I'm looking for a low cost method to perform Eye Pattern Testing on 100MBit and 1 Gigabit Ethernet transceivers.  I do not own a BERT and I have a 4 channel 500MHz DSO available.


texts: Is it possible to have active low window comparator using open collector output opamps?

texts:
My textbook uses opamps with active pullup and  diodes:
\$A1\$ drives the load when \$v_{in}\lt LTP\$
\$A2\$ drives the load  when \$v_{in}\gt UTP\$
None drives the load when \$LTP\lt v_{in} \lt UTP\$

There is a serious limitation with this as it cannot drive loads with different supply like TTL.
So I'm wondering if this can be done using open collector opamps. Any help?

Btw I know how to work the active high output window comparator using open collector opamps. It is the active low output as shown in the diagram I'm not able to get..


texts: Using an analog voltmeter to display the changes in out put made by a dimmer switch for a light

texts: I'd like to preface by saying k know little to nothing about electrical engineer but would like help with making a lamp. I want to use a volt meter style gauge to display a different reading for a light based on how bright it is using a dimmer switch. I'm assuming it's not as easy as simply wiring the meter to always read the current after the switch and wanted to see if anyone could help me. Any input would be appreciated.


texts: Why is the conducting layer in resistive touchscreen placed perpendicularly?

texts:
I just learned that in analog resistive touchscreen, conducting layers (usually made of indium tin oxide) is placed perpendicular to each other. One on the top flexible film, and one on the bottom, rigid film. On when the end user presses the top film, the conductors touches and a circuit is thus formed.

I previously asked a related question, and Wouter van Ooijen, who answered the comment question, told me that using parallel linings, the conductor will not necessary touch at the point where the user presses the film. But I am not clear how that would happen. So I made a separate question.

Also, what does the conductor looks like? Are they fine conducting strings placed close together?


texts:
I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

I am using a motor from an electric bike, as a generator and I am rotating it using a drill, to test its regenerative properties. The energy generated is consumed by R1. The current flowing through the circuit is controlled by a low-side N-MOS switch, using the STP55NF06L N-Mosfet. Its gate is driven by a PWM signal (at 500Hz) and an ICL7667 Mosfet driver.

I am using both a multimeter and the attopilot current sensor 90A version.

The output of the current sensor is driven to an AnalogToDigital port of my microcontroller. The problem is that the current readings I get from the sensor, are not steady and are changing rapidly, while the multimeter shows a nice, steady current value.

I decided to check the output of the current sensor using an osciloscope. With the N-MOSFET duty cycle set to 60%, and a current of around 1A (as measured from the multimeter), these were the results:

This picture has a 1V/div scale:

This picture has a 500mV/div scale:

How can I filter the above noisy signal to get a nice current reading from the sensor, like the one of the multimeter, that seems to be the mean value of the current flowing through the circuit?


texts:
I am currently messing around with a project I thought would be fun but am having some issues.

My goal is to use a signal generator to send a wave through my 7MHz (Steminc) piezo s-configuration transducer (through the carotid artery) and to use another transducer to capture the scattered wave and measure the doppler shift. I am trying to do a proof of concept first, and want to just get the measurement through a scope; however, when I try placing them, I only get noise.

My electronics background in theory is ok, but in practice is not strong at all. I'm assuming I need some circuitry or have overlooked something along those lines. I was hoping someone could give me some guidance, whether it be a useful resource or somewhere to start as far as the circuitry.


texts:
I am working on the Arduino magnetic levitation project and it requires "ratiometric" hall effect sensors. On amazon and adafruit there are no hall effect sensors that are explicitly "ratiometric". Based on a quick google search I know that being ratiometric means its output changes based on a change input or supply voltage, but this makes it seem like all Hall Effect Sensors are ratiometric. Can I buy whatever is on amazon or do I need to go elsewhere and buy a ratiometric hall effect sensor?
Thank you, the help is greatly appreciated!


texts: How to calculate impedance for reverb tank in a guitar amp

texts:
Background:

I'm in the process of restoring a HIWATT HI-GAIN 50 COMBO Valve guitar amp and one of the issues it has is that the reverb dial has no effect on the sound.

Attempted troubleshooting:

To troubleshoot this I first replaced the 12AX7 tube responsible for the reverb recovery circuit and that made no difference. After this I disconnected the reverb tank and connected headphones to phono / RCA connector that was connected to the tanks input. As expected I could hear the guitar signal with no issues. The next test was tapping the phono / RCA connector that was connected to the output of the amplifier. Sure enough the tapping created the expected buzz on the amplifier confirming that the signal paths to and from the tank were working. The next test was to connect the input signal to the tank and connect headphones to the output of the tank, nothing could be heard other than the sound of the reverb springs when the tank was moved (this could be heard with or without input phono connected)

I removed the tank from the amp and inspected all solder / mechanical connections and all seemed fine. Measuring DC resistance the input transducer measured 30 Ohms and output transducer measured 69 Ohms (Obviously this wont be the impedance the tank is rated by, but at least it showed that the transducers were not a dead short or open circuit). To further test my reasoning I fed an audio signal into the input and probed with an oscilloscope. Signal could be seen up to the input of the input transducer and nothing at the output / springs of the input transducer hence the conclusion it must be dead

Replacement Part:

The code on the tank is 3CA3A1B

From what I've found on the internet this means:

3: reverb type = 3 springs
C: input impedance = 240ohms
A: output impedance = 600 ohms
3: decay time = long 2.75 to 4.0 sec
A: connectors = input grounded/output grounded (Appears to be wrong as input is isolated output is grounded)
1: locking device = no lock
B: mounting plane = horizontal open side down

However I cannot find any tank with these impedances for sale (specifically in or ship to the UK)

Getting to the point... The Question

I have a schematic for the amplifier and would like to find a way to calculate the allowable ranges of input and output impedance for the reverb tank (connected to CN5 / CN6). By doing this I may be able to find another tank that will work with this amp that I can buy in the UK

The tank is driven and recovered by JRC5532 OP AMPs before being passed to the 12AX7 amplifier circuit. What confuses me is that in the datasheet for this part the maximum drive output is given as 600 Ohm which is far higher than the 240 Ohm impedance required by the reverb tank however the 600 Ohm output drive is given at 10Vrms.

In Short

How can I calculate the range of input and output impedance that would be compatible with this amplifier?


texts: In-system programming of the SPI Flash chip

texts: Device have Serial NOR Flash chip MX25L6406E located on the rear of the PCB (SO-8/SOIC-8 Package). Is it possible to program chip without desoldering it? (In-system programming). As I know, it depends mainly on specific design.


texts:
Does anyone know how to implement in Altium a buried via (a via in PCB inner layers) with e.g. rounded rectangle shape? E.g. i could define a pad with rounded rectangle shape and connections in inner layers, but the pad hole can go through full stack only.

I need this for a very specific design, and from manufacturer point of view this could be done. But, I would need advice on how to specify it properly in PCB design.

Perhaps there exists any other methods how to achieve this (specify a rounded rectangle shape slot with plated sides in PCB inner/core layer) with other methods?


texts: Voltage across capacitor/inductor in RLC circuit

texts: It is said that voltage across capacitor/inductor is higher than the  applied AC voltage. How?


texts:
I found a chip that is perfect for my application (it has all the necessary features) (Atmel SAM9G45) The processor is based on ARM v5TEJ Architecture with Jazelle technology for Java acceleration. In the datasheet it says:

  processor supports the 32-bit ARM and 16-bit THUMB instruction sets, enabling the user to
  trade off between high performance and high code density. It also supports 8-bit Java instruction set and includes
  features for efficient execution of Java bytecode, providing a Java performance similar to a JIT (Just-In-Time
  compilers), for the next generation of Java-powered wireless and embedded devices
  Blockquote

My question is, I would like to avoid the fees and risk associated with Jazelle. Does this mean I am strictly required to use Jazelle with this chip, or can I still compile C for ARM 32bit and proceed as I would for other 32bit Arm development?


texts: Is it good practice to run large amounts of current through a MOSFET?

texts:
I have been looking for a good way to control the flow of a lot of current in my project. This may at some points be 40-50 amperes at 12-15 V. While relays are a good choice, they are mechanical and therefore take time to activate and wear out over time.

I have seen MOSFETs (like this IRL7833) that are advertised to be able to handle such demanding tasks. However, considering the size of the FET, it makes me uncomfortable to be putting that much power through it. Is this a valid concern?


texts: Using a Steel Wire as the Heating Element

texts:
I'm new to electricity but have a basic understanding of circuit theory.

I came across this video using what appears to be a steel wire (looks like >0.5mm) as the heating element of a homemade hot glue gun.

youtube video

The key point is the steel wire is connected directly to a 12V 5A power.  But I don't understand why it works:

1) There is no resistor to limit the current, shouldn't it blow up some fuse?

2) If a steel wire of that thickness is used as the heating element, what current is required?

3) Is it possible to rely on the contact resistance as a way to limit the current?


texts: Parallel a diode to solid state relay load is a short circuit?

texts:
I'm trying to use a solid state relay control a 12v dc air pump, so I was reading the "Solid State Relays Common Precautions"(like below).
http://omronfs.omron.com/en_US/ecb/products/pdf/precautions_ssr.pdf

When I read the paragraph shown in the screen, I'm wondering if I parallel a diode to the load, I'm I making a short circuit since there won't be much resistance in the dioade so the current will just bypass the load and go through the dioade?


texts: Powering USB to serial CH340 converter - does it need to be powered from USB port?

texts:
I am creating simple expansion board for my Raspberry Pi with a few I2C components (EEPROM, RTC,...) and I would like to add  a USB to serial converter to be able to connect to the RPi's serial port for debugging purposes (console access).

Until now I've been using a simple module with CH340 and I've decided to "just move" the chip onto my expansion board. Unfortunately the official CH340 datasheet is only in Chinese and the unofficial translation is not detailed enough.

I am not sure how to power the chip. In all examples it is powered from the USB port via voltage regulator (I need 3V3 logic for my RPi) however I have 3V3 available from RPi and I would like to power the CH340 chip from it to avoid using additional voltage regulator. Is this possible or does the CH340 need to be powered from the USB port?


texts: Stop a Relay H-Bridge for Brushed DC-Motors to get burned

texts:
i am using two Relays to create an H-Bridge.
This H-Bridge drives a 24V Motor ~3A in both directions.
Now i often got the problem, when i turn on a motor and turn it off again, the relay contacts are getting burned (because the motor gets shorted between the two GND pins and its kinetic force will get stopped and it creates an electric arc)
Do you think i have attached the snubber (R = 27Ohm | C = 470nF) in the right way?
Would it be better to create a second snubber on the GND Pin of the Relay, so that both: Motor ON and Motor OFF gets secured by snubber?
Unfortunately we need to short the motors when they are turned off, so it is harder to rotate the rotor of the motor.
The Relay contacts when the motor is getting turned on are always looking very nice, it is mostly the GND contacts on the relay when the motor gets shortet after it is turned off.
Any Ideas? :)
Schematic -> See in the Pictures.

I am also using Free-Wheeling Diodes


texts:
Let's say I want output voltage from LM317 in range from 8V to 15V. What circuit do I need to built?

I understand perfectly how to set upper voltage range (1 x resistor + 1 x pot), but how do I set the lower point at the same time?


texts: Solving for electromotive force constant in motor armature circuit

texts:
I have a motor with the following parameters. The motor has gear ratio of 19:1 all values are shown at 12V.

According to the electric circuit of the motor armature, this holds:

Circuit:

how to solve for the k_e constant? I tried to solve for R_a by noting that in the stall condition, ̇w_g=0 and at steady-state di/dt= 0. but can't continue from that point to solve for k_e
Motor datasheet : https://www.pololu.com/file/0J1706/pololu-37d-metal-gearmotors.pdf


texts: AC-model of Integrated Boost-Flyback converter

texts:
I am designing a small SMPS to light a few Nixie tubes from an ordinary USB charger. This requires a high voltage gain around 40 which disqualifies many of the typically used topologies. I have grown fond of the Integrated Boost-Flyback converter proposed by Prof. G. Spiazzi. link

I have simulated the circuit in LTspice, and it works out really nicely, and with a snubber over S it seems to be a very quiet circuit as well. Now I need to design the feedback loop and input filter, and therefore an AC-model is required.

I have tried to follow the procedure from the Fundamentals Of Power Electronics textbook and it works out quite nicely until the equivalent circuit is to be drawn. (I did make a short cut though: I removed the leakage inductances to avoid resonances and a few extra states. Basically I replaced the primary and secondary leakage inductors with equivalent resistors.)

Basically each linearized AC equation can be drawn as a circuit, each pair of dependent voltage/current sources can be replaced by an ideal transformer. But I get a few terms that I cannot find a suitable component for =/

E.g. during the charging time slot current will flow both through the magnetizing inductance and through the secondary of the transformer so that C1 is charged. Therefore the currents on the primary and secondary side will both depend on the voltage from Vg and C1. But since the equations for the input current and the current through C1 are node equations, these terms will appear as current sources in the circuits for Ig and Ic1.
What can I do here? Should I keep 2 dependend current sources in the diagram, or is there in fact a component that properly describes the coupling between the circuits?

Additionally, since Vg is loaded by the secondary resistor, its current ig will depend on Vg. This typically happens in the inductor loop equation, and in that case that term is identified as a resistor. But in this case the term appears in a node-current equation in which I cannot fit a resistor. One option is to represent the term with a dependent current source, but I expect there to be a more elegant solution.

Any help or ideas how to reach a proper AC equivalent circuit is highly appreciated


texts: dspic30f4011 crystal oscillator configuration confusion

texts:
I am using a dspic30f4011 controller. I am confused about the oscillator frequency. According to the datasheet, it can support 4 to 10 MHZ. I have 8 MHZ and 11.0529 M HZ crystal oscillator. I know, there are two types of the external oscillator can be connected to the controller. 1. XT which is up to 4 MHZ and other is 4 MHZ to 10 MHZ which is HS type oscillator.
I am using this oscillator with dspic30f4011.
I don't know this type. It might be HS type as it is with high frequency.
But the problem is that I am not using the external oscillator below 10 MHZ. If I used 110.592 MHZ oscillator, What will happen?
should I have to use exact value of external oscillator?
define FCY 18000000 //
define FPWM 4000 //
define DEADTIME (unsigned int)(0.00004* FCY)
define FOSC 11052900 //64MHZ
can you tell me what I have to configure about FCY, FOSC for this crystal oscillator for dspic30f4011?
I am very sorry for this question but I am confused with much more information on the internet.


texts: Stepper motor to replace brushed DC motor to be used to start a gas engine?

texts:
I'm trying to decide if it would be possible to use a stepper motor to replace a current 12V DC brushed motor that is used to turn over a small (~149cc) gas engine for starting.

The reason why is, I would like to use the stepper motor to generate some small current when it isn't in starting mode. I can't do this with the current brushed motor setup, as that would wear out the brushes.

My idea is that using a stepper motor would give it dual purpose: starting the engine, and generating small current when the engine is rotating it.

The current brushed motor has 0.3 ohms of resistance, but I'm not sure of it's torque capacity, so I need help picking out an equivalent stepper motor. Here's a link to the current motor: GY6 150cc starter motor

If you do not think it's feasible (like if the suitable capacity stepper motor is too big or too costly). I would like other solutions as well if you have any feedback.

Thank you.


texts: Why polygon pour size and trace width don't influence each other in altium

texts:
Im using some thin traces in certain areas of the board that I want to have beefed up with a polygon pour. However, when I run the rule check it just ignores that the width of the traces is now effectively larger due to the pour, and still reports that they don't meet the minimum width. Is there a way to change some of the rules so that it doesn't do this?

Here's a picture for reference. The wire inside the black rectangle highlighted green due to breaking a rule is of the same net as the polygon surrounding it.


texts: Short the ground isolation of an isolated gate driver

texts:
I want to play with BLDC motor control and wanted to use the relatively new gate driver UCC21520 from TI. It is an isolated one. I'm wondering if for testing purposes there are any disadvantages if I connect the two grounds and so disable the isolation?
The main reason for me doing that is the measuring with my scope. If the grounds are isolated I have to measure one voltage differentially with two probes. If the grounds are connected, I can measure two voltages with two probes.


texts:
I am having problem understanding the Transfer function for Small signal model of inductor series peaking as shown below.

However, how does this transfer function contribute to peaking since there are no "zeroes" at the nominator ?

Retrieved from A Wideband Low Power Low-Noise Amplifier in CMOS Technology


texts: I want to calculate the number of cycles that my battery has reached during its life in my PV plant. In the datasheet is indicated that the state of charge minimum is 10% and the maximum is 100% and that the maximum number of cycles is 5000, after that it starts to decrease his capacity until the change of it. I want to know if it has reached 5000 cycles. It is not clear if for cycle is indicated the charge and discharge of the battery from 10% to 100% or 2 times the nominal energy that is charge and discharge the battery from 0% to 100%. Do you know what is exactly a cycle of a battery? Is there someone that has experience with solar panel and batteries?


texts:
I've found this method of triggering of the SCR through DIAC and I'm trying to understand it. I was able to figure out the whole trigger circuit and how to compute the values of RC in order to have the desired delay time to trigger the DAC. What I don't understand is how should I syncronize the trigger part with the wave from the line.

simulate this circuit – Schematic created using CircuitLab

After reading the comment of @user287001, isn't something like that almost correct? (suppose that is enough for me to use only an half-wave)

simulate this circuit


texts:
Currently I am working on FPGA design which uses trace32 to interact with jtag devices. Since there are more than once JTAG device in the design we are using parellel (not daisy chain) approach from JTAG controller to select a spefic device.
Are we doing it right? Or daisy chain is the recommended method for muitiple jtag devices design ?


texts: How to implement multiple functions on single push button

texts:
I am using a STM32 Nucleo MCU and trying to pull a multi-function single-button method.

I need a way to implement this form of functionality for a single push-button:

Push 1: function 1
Push 2: function 2
Push 3: function 3
Push 4: function 4 + reset/loop back to before Push 1

I tried using a sort of counter variable like:

if(GPIO_Pin == Pin){
    Counter++;
    if(Counter == 1){
        function1();
    }else if(Counter == 2){
        function2();
    }else if(Counter == 3){
        function3();
    }else if(Counter == 4){
        function4();
        Counter = 0;
    }
}

But then the problem I faced is - I had to place these conditional statements inside a while(1) loop - so it keeps running. Here the Counter variable becomes unreliable since the while loop will increment the Counter variable too many times.

I tried using GPIO_EXTI - which are interrupt callbacks. Even when I call the functions using with External Interrupt Mode with Rising Edge trigger detection I am having the same problem with the counter variable increment multiple times.

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
  if(GPIO_Pin == Pin){
            Counter++;
            if(Counter== 1){
                func1();
            }else if(Counter== 2){
                func2();
            }else if(Counter== 3){
                func3();
            }
    }
}

Is there any way around this rather than just use more buttons? Or any way to implement a multi-function single-button method different from the counter method I thought of?


texts: What will a pin-header connection do to my voltage supply integrity?

texts:
I am working in verification and my boss came up with a new idea I should be looking into. The verification boards that we are designing for testing the microelectronics that we develop are different each time and we develop them from scratch each time (I take schematic pages from old projects sometimes but I don't reuse boards from older projects).

His new idea is: Build a motherboard that inherits all the generic components that we need for testing in every project and then have a specific board build for the specific chip we have designed in the specific project.

I gotta say I like the idea. I can test some functionality of my test bench before the chips are manufactured and I can reuse these features for other projects. Also digital control which would be programmed from an mcu can be reused.

The chips that we build can be quite different from each other but what they all have in common is that they have similiar voltage supply schemes and they are all configured via spi. So i figure, I could put an mcu as spi-master + the necessary voltage supplies on the motherboard. the "project board" would then be attached to the motherboard with pin-headers(?).

Long story short:
What happens to a powersupply rail (lets say 0v8 or 1v8) if I generate it on a motherboard and then transfer it to a 2nd board via a connector (a pin-header/socket-connector for example)? Current won't be that accessible so I would have to provide capacitors on the 2nd board. That I can calculate and come up with capacitors I can place. Is there anything else I should think about? Do you have ideas about this concept? Is there a different connector then pin headers I should consider from your guys opinion?


texts: 5v relay to be driven from a limited supply of 20mA which requires 200mA of latching current

texts:
Possible Duplicate:
  Pulse-powering heavy loads with a coin cell

I have to operate a latching relay at a nominal voltage of 12 V or 5 V. Right now, i have not chosen the relay so lets consider I have a relay to operate at 5V and the coil resistence is 24 Ohm. The hold current of the relay will be 200mA and we need to give a 5V pulse upto 50mSecs for the relay to latch properly. The problem is I have a limited supply of 20mA from my power source, so I need to employ a charge pump sort of thing which can store some energy and give it to relays when they operate. But is there any specific design which I can follow, and arrive at proper design.


texts: Get Feedback from Internal Potentiomet of Servo Motor

texts: Hello! I was trying to control an MG996R Tower Pro servo motor using Matlab and I need to get some feedback from the internal potentiometer of the servo. However, I don't know where to connect the wire so that I can get some feedback from the potentiometer. I have attached a picture of the board of my servo. Thanks in advance!


texts:
I am trying to make a counter that counts up to 10. I have used 4 flip flops and I added an AND port so that when the counter reaches 10 it goes back to 0. The problem is that after 10 it goes directly to 16 and then back to 0.
Below is the circuit:


texts: 3 Phase power logger with ADC and Raspberry Pi

texts:
I am building a 3 phase power logger with the ability to measure 3-phase AC and 2 DC inputs as well for a final year project. A typical application would be measuring a small inverter for a solar application on both the AC and DC sides. I am using CT's and a burden resistor for AC currents, a hall effect sensor for DC currents, and simple voltage dividers to bring down the AC and DC voltage to within the range of the ADC. I am using a 12 channel single ended ADC with simultaneous sampling. Sampling the voltage and currents for each phase simultaneously and sending it via I2C to a raspberry Pi where all the calculations etc. is done.

My problem is that the ADC only takes voltages from 0 - 2.5 V as analog inputs. All my signals are voltage signals that ranges from -V to +V. So my signals need to be scaled down and lifted with a DC offset. I have found a couple of ways in doing it but would like some advice. Another thing is that I've read that a Low Pass filter needs to be added before the analog input to eliminate aliasing effects etc. So I need to shrink voltage, add a DC offset and a low pass filter.

I would want to capture at least 30 harmonics for a 50 Hz AC signal so the filter needs to let those through. I simulated a simple 3 resistor voltage divider network that lifts and shrinks the voltage to the correct level but will it work on all the frequencies and is it reliable? and where do I need to place the filter, cause the moment I add a filter the wave-forms change, do I need to add Op-amp buffer between the divider network and the filter? Is it best to use a op amp for the low pass filter?

I've added a picture of my suggested circuit.

Any advice would be highly appreciated.
Thank you


texts: Connecting two CMOS transceivers on different boards

texts:
I have a main board (with DSP controller & CMOS Transciver) and an daughter board (with CMOS Transciver, Ethernet & GPIB controller). these two boards are connected with DIN connector with flexible PCB.

Output pin of the CMOS Tranceiver in main board - has 23.7 Ohm
Input pin of the CMOS Tranceiver in daughter board - has 22 Ohm

Pls let me know what could be the purpose of these resistances.?


texts: How exactly to track oscillator in superhet receiver

texts:
The IF is 490 kHz. I have learnt that the local oscillator and the tuning block before the IF stage must "be aware of each other" or track. So in my case, the tuning of both the circuits should differ by 490 kHz. See this article:

Radio Receivers - Constant Frequency Separation

Specifically, it is mentioned that:

  Since we have to tune the RF amplifier section throughout the entire broadcast band,
      the frequency of the local oscillator must also vary in a manner that it always
      maintains a gap of 455 kHz. To achieve this condition, the Local Oscillator and RF
      Amplifier section are 'ganged', i.e. their tuning condensers are connected/ganged
      mechanically in such a way that when we tune the variable capacitor in the RF section,
      the variable capacitor in the local oscillator also changes its value, it 'tracks' the
      frequency to which the 'Aerial Circuit' is tuned and remain separated from the tuned
      frequency by 455 kHz up.

I want to know how exactly is this tracking done. As far as I understand, the variable capacitor is made common to both the oscillator as well as the front end tuner. How will this lead to a difference of 455 kHz (or 490 kHz in my case) in the tuning of the tank as I vary the frequency of the oscillator?


texts: frequency division by 5 using only JK flip flops

texts:
I've was asked to design a circuit using nothing but JK Flip Flops and a clock that will divide the clock's frequency by 5.
while obvious solutions can be done using other logical gates i can't seem to solve this one with nothing but Flip Flops.
any ideas?


texts: ADC - Internal Reference Works Better at 3v vs. 4v?

texts:
SOLUTION: Make sure your power input is 200mV over the reference power source (that's a typical bandgap reference voltage required).  So, 3.2V is required for a 3V reference.

I'm finishing up a embedded design with an 8051 MCU, and coding up the ADC to function as a battery voltage detector.

I noticed a strange anomaly, I'm sure there is a very easy explanation.

I power the MCU & circuit with a 3.7v Lipo battery (so it fully charges up to 4.2v and discharges to say 3.5v with the protection IC on it... something like that).

I have a voltage divider from the circuit power, that turns the input voltage going into the ADC input from a max of 2.483v max to 1.848v min.

I set the ADC to use 4v as the internal reference voltage.  I assumed this would be fine since since the inputs from the voltage divider are below 4v.

I got all kinds of funky readings that are not consistent from a adjustable power supply. It's not a software issue combining the 12 bit results.  The hardware is just putting out flucating values.

I thought maybe my adjustable power supply has a really noisy output, but looking at it with a scope the output isn't flucating around like crazy.

On a lark, I changed the internal reference to 3v and all of a sudden the readings are totally stable and respond as you'd think.

Is there some reason that the 3v reference voltage works so much better?  Is the 4v reference voltage just too far off?

Maybe this is obvious -- could it be that the 4v reference isn't possible if the Lipo is at 3.7v?  This is some really cheap Asian 8051, they don't really spell out how the AD reference voltages work.

I'm not 100% on the arithmetic of an AD, I could sit and noodle the step values of the 12bit AD, but I really just am curious if there is something obvious here why the AD readings didn't work well with the 4v voltage reference?


texts: Does the signal direction matter for a series N-channel FET switch circuit?

texts:
I'm working with a 40-year old audio circuit that someone modified to use an FET as a series switch. The circuit uses the Toshiba 2SK30A N-channel FET to pass a nominal ±1 VAC audio signal.
The Source-Gate legs have the appropriate 10M resistor across them, the gate control works fine, and the device seems to pass audio as desired.
The problem is, the incoming audio signal is hooked-up to the Drain leg and passes through the FET to the downstream op-amp via the Source leg rather than the other way around.
Is there a possible reason for doing it this way? Any problems this arrangement might cause?


texts: How can I create a series switch with a transistor for low power application

texts:
Hi,

I would like to make a switch that turns on/off input Vbattery to a analog (AIN) pin of uController used to measure battery level.

The uC also should control if the transistor is providing the Vsense voltage to the uC.

I need the circuit to have the following properties.

When the transistor is OFF (i.e. not providing Vsense) then the current consumed by the transistor block should be not more than few micro amps.
When transistor is ON the output (that goes to the divided resistors) should follow the same voltage level as the V battery input. I can allow for a constant voltage drop between the input and output of the transistor as long as its fairly constant.
The on/off controller is TTL 0v/3.3v I don't mind which way is on or off.
The divider resistors are 1K ohm (more or less)

I am thinking that I will need some sort of FET but not sure what to use or how to create a circuit.

Thank you for your assistance.


texts: Are there good free software analog filter design tools? If not, why?

texts:
I'm finding myself needing to do a fair bit of analog filter design.  Mostly passive LC ladder filters.  I honestly don't know much about how to design them by hand, I've been using the Genesys tool.

I'm also getting into using a lot of free software for my work.  I find the work flow is generally faster and more enjoyable.  So, I've been looking for a free software analog filter design tool.  It's quite easy to design digital filters with Python, but there doesn't seem to be much for analog filter design (and I mean choosing the values of capacitors and inductors).

So, am I missing something?  Is it straightforward to realize an analog filter with these tools?  If not, why does nothing like this exist?  What are the typical algorithmic methods for designing analog filters?

*EDIT: What I mean is free as in freedom software.  I'm aware of all the vendor provided tools, I don't like them.  I usually find them much more difficult to work with.  And, I'm also just curious now about why there doesn't seem to be much open software in this area.


texts: How does Laplace transform include the transient response?

texts:
When we provide a sinsusoidal input, the evaluation of the solution of the differential equation head-on becomes horrendous. So we give an imaginary, complex exponential input and solve the differential equation and finally take the imaginary part as the solution (superposition theorem). So once we find the complex amplitude we can just multiply it with \$e^{iωt}\$, take imaginary part and arrive at the solution.

We can find the sinusoidal steady-state response for the given system, with this neat trick. When we use Laplace transform, as far as I can understand, it also gives us a complex amplitude, not only for the steady-state but also includes the transient response, for any input !. The idea behind the precious trick of modelling a sinusoidal input with complex numbers was perfectly intuitive. But I've got no idea how Laplace transform does all this, I don't even understand, why it demands the use complex numbers? rather how does it find this alternative model for any given input, as we did in the previous "trick" only for sinusoidal input.


texts:
I have a 1000mW engraving laser module. It was working well.

Unfortunately it suddenly lost its burning power and wasn't capable of engraving anymore, although the laser diode is still ON and generates the same focused purple-blue light and the body of the module gets warm when it is plugged in to power.

I changed the power source - the result was the same, it is just a laser pointer, not burner.

Is the problem with the laser diode, or its driver?


texts:
Do constant current batteries exist? If not, why not? Else, why are they not very common in the market?

I am not talking about an ideal current source. But it should be a constant current source for few range of values (load, voltage or something). "1mA source with max terminal voltage of 20V" or something like that (I am not sure about the specs).


texts:
I want to play a small .mp3 file using AVR ? How
I've been googling with no good result  ,
Those are the result of m googling :
http://www.beyondlogic.org/pic/ringtones.htm
http://www.avrprojects.info/files/media/MMC-card-wave-player-circuit-diagram.gif
http://www.avrprojects.info/avr-projects/mmc-card-based-wav-player/


texts: How to choose a "gate current limiting resistor" for an SCR in a crowbar circuit using gate voltage and gate current from SCR's Datasheet?

texts:
I want to choose a **gate current limiting resistor ** R2 for a crowbar circuit like this:

First of all I am not an electronic engineer and I have limited knowledge about circuits. I am a little baffled. I have chosen an SCR: BT152-600R.

Datasheet says:

I_gate = typically 3 mA and maximum 32 mA.

ok! This maximum 32 mA is actually the minimum guaranteed current that trigger the SCR. From what I know I should provide this 32 mA to the gate to be sure that it is going to trigger it.

But what baffles me is that there is another thing:

V_gate = typically 0.6 V and maximum 1.5 V.

Isn't the current enough?  Is it important to have this 0.6V or 1.5V supplied to the gate?

In other words assume that I have LM7805 and a 5.1 V zener diode placed after that which pass 0.1 V to the line that goes to SCR. If that line provides enough current, is it going to trigger the SCR? If yes... so what is V_gate actually?

Now back to the main question.

If the Zener in the circuit below was 7V then in the over voltage condition it provides 2 V to the gate of SCR. The maximum current for triggering is 32 mA and V_gate is 1.5! So I think R2 should be maximum = R2 = (2-1.5)/0.032 = 15 ohm . Am I right?

The circuit below with 6.2V zener diode is going to provide 1.2 V to the gate of SCR during over-voltage condition. The maximum current for triggering is 32 mA and V_gate is 1.5!! How can I calculate it this way?! it yields: R2 = (1.2-1.5)/0.032 = -9.38 ohm!

Does it mean that I don't need a resistor?
Does this mean that V_gate is irrelevant?

That's what baffles me.

I'd be thankful if you could clarify this for me.
Thank you in advance.


texts: Do 2 5V DC wall warts in the same AC outlet have a common DC ground?

texts:
I'm trying to power a LED strand from one wart (5V), and my logic driver FPGA from another wart (also 5V). Both warts are plugged into the same outlet strip. I know I should probably power them from one, but I don't have the plugs on hand to rig both to the same plug.

Both warts are 2 prong (not 3 prong).

Can I send 5V digital signals from one domain to the other?

I tried testing voltage across the domains with a voltmeter but it just reads 0 (floating?) anytime I try to cross them.

VDDA to GNDA reads 5V  (first wart)
VDDB to GNDB reads 5V  (second wart)
VDDA to GNDB reads 0V  (cross domain)
VDDB to GNDA reads 0V  (cross domain)

I'm assuming my voltmeter reading tells me that I can't send signals from A to B. If that's true, would I want something like an opto-coupler to transfer a signal from A to B?


texts:
I know that a semiconductor material, that is usually used for heaters in variety of application, heat up due to high current, which flows through them or high power dissipation across them.

But lets say that some material is going to heat up for more than 400°C if some voltage is applied to it, and also a high current flows through it. But what about the supply cables that are connected to nodes of heater material - shouldn't the heat up for the same amount of °C? I mean, as that high current flows through the load (heater) it must flow through the supply wires also, right? But in real life cables/wires don't heat up as much as the load, that is used for heating up something.

But why is it so? Is it not all about current flow but about power dissipation across wires compared to power dissipation across load (heater)?

A good example is a welding machine - cables that supply all that high current and high voltage definitely don't heat up as much as a contact point, where material is welded.


texts: How to find equivalent resistance in following question

texts:
I am solving objective questions from my book but the main problem is that it doesn't have solutions and in following question I don't know what type of question is this. First I am thinking its Wheatstone bridge related but its not. And resistance are in series but its not. So please tell me what type of question is this and how to solve it.

Here's one I draw before but above one is confusing.


texts: Finalize project: How to go from breadboard to a semi-permanent circuit

texts:
I'm tinkering with Raspberry Pi, and envision a few small applications that will require external circuits.   I find the breadboard setup to be a bit too fragile for long-term use, but I'm not sure how to make it more permanent without making a custom PCB, which seems like overkill.

Here's a crude breadboard to connect an I2C temperature sensor -- which can be redone as a cable and some heat-shrink tubing, but my next project will have a few more components.

One option seems like a few drops of glue in strategic places on the breadboard, but this seems a bit clunky.

Is there an option between breadboard and PCB?


texts: Why is it important to never charge a cell at voltage higher than Vmax?

texts:
In specifications for Li-ion cells, the maximum charging voltage (Vmax) is typically given and said that the cell must not be charged at a voltage higher than that.
If I understand correctly, there are two reasons why charging a Li-ion cell at a voltage higher than Vmax can degrade or destabilise the cell:

If we charge at this voltage long enough the cell will over-charge (Vmax assumed to be equal or close to OCV(SoC = 100%))
The difference Vmax – OCV(SoC = 0%) is high enough to make some unwanted reactions at the electrode-electrolyte interface(s) possible, or alternatively, the current = (Vmax – OCV(SoC = 0%))/Rchg is high enough to cause some damage to the battery. (Though, the maximum charging current Imax could also be specified directly.)

(For simplicity, I also assume the cell's internal voltage consists only of the OCV.)
If this is right, I don't see what could go wrong if I charge a cell at a voltage higher than Vmax at the moment when it's at SoC = 70%, for example. Assuming the Imax of the cell is in the order of hundreds of Amperes because otherwise, it probably limits my charging voltage to a value lower than Vmax even at SoC = 70%.
So one explanation I can see for why cell manufacturers give "simplified" instructions about Vmax is that they also specify Imax in the order of single-digit Amperes (translates to single-digit C-rates). This means that at the normal temperature when the Rchg is single-digit mOhm, we are never allowed to charge at a voltage more than about the current OCV voltage + 0.05 V. This means that the theoretical time window when we would be able to charge at a voltage higher than Vmax is too small to bother specifying it.
If the above explanation is correct, then I don't understand why the cell's available charging power is calculated as Vmax*(OCV - Vmax)/Rchg: in practice, this charging power should be prohibited almost all of the time?


texts: Darlington-pair transistor power amplifier for cd-player

texts: I want to build simple one-transistor power amplifier for cd-player. I found 2sd605 Darlington transistor for it. I use 8 Ohm load speaker and have a lab power supply 20V. I want to connect speaker between Collector-Emitter through capacitor. I want to know how I can find collector resistor and input power-to-base and base-to-emitter resistors values.


texts:
I am working with bunch of uSD card. The place where i work is not ESD protected so i am just concerned if these devices can get damaged by the discharged current.
Can someone help ?


texts:
Would you be so kind to point out any errors in this schematic or anything else to improve (layout and clarity also greatly appreciated).

This is supposed to be the power/regulating/batterycutoff schematic of a device.

Device has a lipo battery and a switch (S1) to turn on and off.
Battery is connected to voltage detector (U3) which sends a high
signal to U4 at 3.05V.
Battery also connected to analog switch (U4). Depending on signal from U3
switches between battery low warning led and main circuit. (acts like relay)
U2 regulates power supply to 2.8V (VCC) which supplies main circuit .

Schematic:

Bill of materials (only chips since rest isn't important, i think?)


texts:
ever since posting here I never been so lost of using op-amps before, hearing new things that I have never heard before (Vom, Vcm etc). I always thought OP AMPS is just plug it in and it will work everytime... Very wrong.

I have a couple of questions which would be most appreciated if anyone of you could answer them, before I asked them, yes I have been looking for the past 2 hours in this forums for previous questions that were asked. Still a little confused but it did clear some things up.

To keep things consistent I would be using This OP AMP throughout this whole example. MCP601

VCM: Common Mode Input Range

Here is what I understand -Its the range of which the MCP601 can happily accept with nothing going wrong, if one were to go over or under these ranges the op you will see unexpected error.

Example: Input = Audio Signal (1.2V pk-pk) VDD = 4.8V VSS = GND

VCM - Upper limit = 4.8-1.2 = 3.6

VCM - Lower limit = 0-0.3 = -0.3

VCM - \$V_{CM_{PP}}\$ = 3.6-(-0.3) = 3.9V

\$V_{IN}\$ - Positive Cycle of input = 600mV + (VDD/2) = 3

\$V_{IN}\$ - Negative Cycle of input = -600mV + (VDD/2) = 1.8

\$V_{IN}\$ = 1.2Vpk-pk

Meaning the input Vpk-pk is suitable?

VOM: Output Voltage Swing

Here is what I understand - Its the range of which the MCP601 is capable of outputting before clipping.

Example: Input = Audio Signal (1.2V pk-pk) VDD = 4.8V VSS = GND GAIN = 3.2

Input Bias = VDD/2 RL = 5k

VOM - Upper limit = 0+100mV = 100mV

VOM - Lower limit = 4.8-100mV = 4.7V

VOM - \$V_{OM_{PP}}\$ = 4.7-100mV = 4.6V

\$V_o\$ - Positive Cycle of input = (3.2*600mV)+(VDD/2) = 4.32V

\$V_o\$ - Negative Cycle of input = (3.2*-600mV)+(VDD/2) = 0.48V

\$V_o\$ - \$V_{o_{PP}}\$ = (4.32-0.48) = 3.84V (Before decoupling Cap).

This is how I understood to calculate for both \$V_{CM}\$ and \$V_{OM}\$. To me this OP-AMP shouldn't have a problem with the Vin as well as happily amplifying the Vin as well, however the opposite happened as it clips at 2.84Vpp. This doesn't make much sense to me from the calculation above. The VCM should be satisfied as well as the VOM. As the VOM has a Vpp of 4.6V which is > then my Vo of ideally 3.84Vpp and my VDD being 4.8V it should amplify to 3.84Vpp no problem?

If anyone can show me how to actually calculate VCM and VOM that would be amazing, I believe this method is missing something or I am not understanding some fundamental logic. I would like to gain the ability to understand input and output limitations through this method.

This configuration works if I increase VDD to ~6.1V if anyone can explain why through the VCM and VOM calculations I can probably correlate the two and probably will clear up any confusions I had.

simulate this circuit – Schematic created using CircuitLab


texts: Protecting a power supply from inductive load

texts:
I recently got a PeakTech 6225A power supply for my hobby of making/"tinkering"/messing around. I get many parts that I want power separately to diagnose them. I also get a lot of electromotors and get asked to see if they work.

Unfortunately,  the manual states:

  Do  not  operate  the  device  to  power  inductive  loads,  such  as  electric  motors,  which  act  as  a generator  during  overrun  and  thus  can  produce  a  reverse  voltage!

I am very inexperienced in electronics, so I chose to ask this specific question, rather than applying concepts from answers to similar questions, as my grasp on the matter is not firm enough yet.

My idea was to make a kind of module/filter that I could plug between the power supply and the electromotor that would protect the former from reverse voltage.

There are several components buzzing in my head: a TVS diode? A MOSFET? RC snubber? Flyback diode? Would a bidge rectifier do anything, since reversing the input polarity isn't an issue, it's the reverse voltage from the inductive load.

Can I apply the circuit described in this blogpost to protect my power supply?

Could I take his (second last) circuit as is, or should I make some adjustments?


texts: What is the purpose of the elements of this antenna?

texts:
I have a 5GHz 23dBi Wi-Fi panel antenna which has the geometry shown in the images below.

I have been quite curious as to the purpose of this bizarre antenna design. The elements have such unique shapes, and each is slightly different, though there is plenty of symmetry. Some elements are not connected to anything (parasitics?) but many are tied to the centerline. The antenna has a ground plane below (about an inch) and the driven elements are etched on a PCB.

How does a design such as this come about, with such complicated geometry? I am familiar with electromagnetics and antenna theory to some extent, but I do not understand this yet.


texts:
There is an example in OrCad PSPICE which calculates noise figure for an RF amplifier.

I know the following formula for noise figure:

$$\text{NF}_\text{dB}=10\log\frac{P_{no}}{G_aP_{ni}}$$

But in this example the software uses another formula:

10*Log10(V(inoise)*V(inoise)/8.28e-19)

Where V(inoise) is the equivalent  input voltage noise.

I don't understand why this formula should be true and where does 8.28e-19 come from?
Is it a general formula that can be used in every simulation?

Here is the result

and the circuit


texts:
I'm studying the difference amplifier circuit configuration of op amps, reading from this datasheet.
I know that unlike the instrumentation amplifiers, the difference amplifier differential gain can be controlled by changing the value of more than one resistor.  For the sake of experimentation, I assumed all the resistors are equal in resistance. I used the high power gain op amp LM324 downloaded from here

In this case, all the resistors values are set to 100kΩ.
From my experimentation the 100kΩ values for the resistors indeed yields a relatively satisfying frequency response:

As I change to lower or higher values for the resistors, the frequency response also changes.
Bode plots for:
10kΩ
100Ω
100Meg

Is there a deeper reason why setting all resistors to 100kΩ yields a better frequency response?
Why is there a change in frequency response when we simultaneously vary all the resistors?

Looking for an answer, I found this thread that doesn't really answer my question.


texts:
Is there a fundamental limitation on how rapidly (with voltage) can a diode ’switch’ ? If so, can you pinpoint its origin?
The diode here is a 1N914


texts:
I got used battery MODULE with the next specs

"40V 18.4AH 736WH build of ninety six A123-26650 LITHIUM LIFEPO4 cell "

Cell specs:

Nominal Capacity: 2300mAh
Voltage(nominal,V): 3.3V
Internal impedance(1kHz AC typical,mΩ): 6
HPPC 10 Sec Discharge Pulse Power 50% SOC: 200W
Recommended standard charge method: 1C to 3.6V CCCV, 45 min
Recommended fast charge Method to 80% SOC: 4C to 3.6V CC,12 min
Maximum continuous discharge(A): 70
Maximum Pulse discharge(10 seconds,A) 120
Cycle life at 10C discharge, 100% DOD: Over 1,000 cycles

I plan to get either:

Solar panel with 18v and 400 watt
Wind turbine 24v and 600 watt

There is a big different between VDC and the Battery voltage.
Can MPPT solve this issue and if the answer is yes what will be the MPPT sepcs.


texts: How did the Telstar 525/405-line conversion system from 1962 work?

texts:
The Wikipedia article on the Telstar satellites from the early 1960s says that in order to facilitate transatlantic television signals (where the US had the 525-line (480 visible) NTSC system, and the UK's BBC had a 405-line system) the BBC had room-filling video signal conversion apparatus.

  The standards 525/405 conversion equipment (filling a large room) was researched and developed by the BBC and located in the BBC Television Centre, London

I'm curious how this conversion equipment setup worked. I know that delay-lines
  are used in relatively modern analog television systems (such as PAL), but it's implied a delay-line system could really only buffer a single line - rather than multiple entire frames to cover a frame-rate mismatch.

Today, to convert video of one-frame-rate and resolution to another necessarily involves modern interpolation algorithms operating on multiple digital frame-buffers - but [Wikipedia implies that the capability for video framebuffers in the 1960s simply didn't exist. I know that but it wasn't feasible to bufferm

(I'm assuming that they had a fully electronic system and that they weren't employing tricks such as using a 525-line TV-signal projector to illuminate a screen that was being simultaneously filmed by a 405-line camera for onward distribution.)

My question is: how could an electronic television signal frame-rate-and-resolution conversion system be implemented using 1960s-era technology?


texts:
I am designing a circuit which reads a analog signal(DC - Response from a photo-diode exposed to tungsten lamp) to a 12 bit ADC. The ADC is MCP3202 running at 1Mhz speed and uses 16 input bits to get one sample of the result.

As per my calculations, I have calculated the response time of the low pass filter as shown below:

Chip Speed (Mhz)    1
Period(us : microSecond)    1
No of Process Cycles    16
Response time required (us) 16
Response time required (ns : NanoSeconds)   16000
Response time required (ms : MilliSeconds)  0.016
Response time required (Seconds)    0.000016 or 1.6E-5

I believe that if my RC circuit is slower than the above response time, then I will see a delayed response, which I should avoid.
Therefore, I choose the following Resistance and Capacitor values for my RC low pass filter.

R = 1 K
C = 5 nF

The cut-off frequency is calculated as :

 fc = 31830.9886184[Hz]

The response time is calculated as:

1.1512925465E-5

Does all of the above sounds OK or am I off track here?


texts: Arduino has an input value in disconnected pin

texts:
I'm new to arduino. Maybe is an elemental question...

If I load this program:

int mval = 0;
void setup() {
  Serial.begin(9600);
  // set up the LCD's number of columns and rows:

}

void loop() {

  mval = analogRead(1);
  Serial.println(mval);

  delay(1000);
 }

I get a value that varies between 300 and 400. When I think it have to be 0, being that there's nothing connected to that input.

Any ideas?? It's an arduino UNO connected to my laptop via USB


texts: Driving three large 7.5v common anode 7-segment displays with Arduino

texts:
I'd like to drive three common anode 7.5v 10ma 7-segment displays using my arduino uno and a few 74HC595N shift registers. The problem is the uno only outputs 5v 40ma on the digital pins.

I am considering inverting the 5v-out to -5v using an ICL7660. The -5v could then be placed at the anodes for a 10v total drop.

I have a few questions before trying this out-

Would the ICL7660 sink enough current to drive all three 7-segments? Are there other drawbacks? Is there a better solution?

Resources:
The 7-Segment Display
ICL7660 Arduino tutorial


texts: Unity Gain Op-amp - 0 volts input giving 1.x volts output. Why?

texts: I have this setup going into an MCU. I'm using a multimeter to verify voltages, and I notice whenever i set the input voltage to 0, the output of the OP amp is over 1 volts. When i increase voltage it starts following it. THe minimum volts it is giving is the 1.x volts. Why is this so?


texts:
I am very new to electronics field, So excuse me I sound silly in any part of my question. I have a sensor which is giving me a digital singal with the help of 2 wires (+ve and ground). The signal I am getting from my sensor and a comprator ciruit after the sensor:

 I am trying to build a DAC which takes this digital signal and converts it to analog signal. I was looking into different ways of doing this.

My first try was using a R/2R ladder circuit.

But I am not sure how do I give binary inputs. I am looking at many other possibilities. But I am not getting a clear idea of how to give give input to my DAC. I'd be grateful if anyone points me a proper way to do this.

Edit:


texts: How to calculate free wheeling current value

texts:
In the below mentioned circuit
which is used for automotive EMR braking. We are facing freewheeling diode burn out (FR607 is currently being used).

We are still clueless about the cause. But as per design this is a 6 A rated diode with surge value of 300 A which according to my design team is well enough. But we suspect that this ampere rated diode is not OK.  We need to find the maximum freeweeling current in this circuit. How to calculate this current value. The coil resistance is 0.8 amps. Load of the circuit is 30 amps and the supply is a 24 V DC battery source 200 Ah.


texts: What is the boxy plastic housing around spade connectors called?

texts:
This spade connector is used to connect to 12V SLA batteries, and I believe it's the F2 variant.  However it has a nice plastic shroud around it which makes it easier to remove from the batteries and since it's fitted after the crimp it doesn't get damaged as some alternative shrouds do.

I am trying to find where to buy these covers (with or without the female spade connectors) however I'm having trouble because I don't know what they are called!

Does anyone know what retailers label these parts as?


texts:
When pin RB5 changes between high and low it should trigger interrupt. Interrupt happens when IC gets powered and does not occur afterwards when RB5 gets connected or disconnected from vdd. Why so?

I am using PIC16F677-I/P

#include <xc.h>
#include <stdbool.h>

#pragma config FOSC = INTRCIO   // Oscillator Selection bits (INTOSCIO oscillator: I/O function on RA4/OSC2/CLKOUT pin, I/O function on RA5/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled and can be enabled by SWDTEN bit of the WDTCON register)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // MCLR Pin Function Select bit (MCLR pin function is digital input, MCLR internally tied to VDD)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown-out Reset Selection bits (BOR enabled)
#pragma config IESO = OFF       // Internal External Switchover bit (Internal External Switchover mode is disabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is enabled)

void main(void)
{
    // Select 8 MHz internal oscillator
    IRCF2 = 1;
    IRCF1 = 1;
    IRCF0 = 1;

    // High Frequency Internal Oscillator is stable
    HTS = 1;

    // Use internal oscillator for system clock
    SCS = 1;

    // Global interrupt enable
    GIE = 1;

    // PORTA/B change interrupt enable
    RABIE = 1;

    RABIF = 0;

    // RB5 as digital input
    ANS11 = 0;

    // RB5 as input
    TRISB5 = 1;

    // RB5 interrupt on change
    IOCB5 = 1;

    // RC6 as output
    TRISC6 = 0;

    RC6 = 0;

    while (true)
    {

    }
}

void interrupt myintrout(void)
{
    if (RABIF)
    {
        RC6 = RC6 ? 0 : 1;
        RABIF = 0;
    }
}


texts: Where do I start for Arduino PCB design?

texts:
Looking for resources on how to start taking my creations to the next level.

Where I'm at:

I'm a software developer nerd with limited hardware design experience
Comfortable creating stuff with the Arduino Duelimanove / Uno pre-fab boards w/ breadboards, project boxes, and lots of tape and zip ties

Where I want to go:

Turn a "breadboard" solution into a custom, non-ghetto PCB
Integrate Arduino / Netduino chips into designs
Being a software guy, I don't really have a desire to make PCB's by hand with the newer "design in computer and have it shipped to you" model
Have designs made in very small quantities (1 at a time, maybe 5 at a time max)

In my google-ing so far, I've tried looking for an outsourced PCB manufacturer that might have an Arduino template component that I can drop on a virtual PCB board and start messing around, but haven't found anything. I assume there are some specific measurements that would allow me to create my own component, but no idea what they are called to search for them.

Any recommendations here would be appreciated on vendors, software, concepts I need to educate myself on, and such.


texts:
Is my thinking of half wave voltage Tripler Circuit right?because my thinking  is a little bit different from the book's

Book
Let the input is a sine wave with amplitude \$=V_m\$

1.When input is the first positive half wave,\$D_1\$ on,and \$C_1\$ will be charge to \$V_m\$

2.When input is the first negative half wave,\$D_1\$ off,and \$D_2\$ on ,and \$C_2\$ will be charge to \$2V_m\$

3.When input is the second positive half wave,\$D_1\$ on, \$D_2\$ off,and \$D_3\$ on ,and \$C_3\$ will be charge to \$2V_m\$

now the \$V_O=V_{C1}+V_{C3}=3V_m\$

My opinion

1.When input is the first positive half wave,\$D_1\$ and \$D_3\$ on,and \$C_1\$ and \$C_3\$ will be charge to \$V_m\$

2.When input is the first negative half wave,and we add the sine input with the voltage of \$C_1\$,the amplitude of input will become \$2V_m\$,now  \$D_1\$ and \$D_3\$ off,\$D_2\$ on ,and \$C_2\$  will be charge to \$2V_m\$

3.When input is the second "positive" half wave,and we add the sine input with the voltage of \$C_2\$,the amplitude of input will become \$3V_m\$, and \$D_1\$ and \$D_3\$ on,and \$C_3\$will be charge to \$3V_m\$.and the voltage of \$C_3\$ is the \$V_o\$

I want to ask is my thinking about the half wave voltage Tripler Circuit right?if wrong,which part of my thinking is wrong,can anyone tell me?thx a lot!


texts:
I have a question about how to take an output from a sensor and calculate RPM.
The sensor produces a square wave at a maximum frequency of 1kHz.
So I think I have two options:

Count rising edges in a set time period

or

Count time between rising edges.

As the sensor is only 1 pulse per revolution, I will have to go with number 2.
This is the method I am thinking of:
On a rising edge I will store the 16 bit counter value and begin incrementing.
On the next rising edge I will store the 16 bit counter value, reset it and then being counting again and repeat on every rising edge.
I will have a counter value from 0 to 32768 between each pulse. How can I mathematically calculate an RPM value?


texts: Effect of Discontinuous Conduction Mode of a Buck Converter on Charging IC

texts: I want to use a buck converter to step down a 20VDC Input to 15V to use for a charging IC (BQ24193). The reason for this is because the charging IC I'm using won't operate with a voltage input higher than 17V. I'm designing a Buck Converter on a PCB, and I'm trying to figure out what inductor size I need. I'm able to calculate the ripple current of the inductor and compare it to the Average Inductor current when the charging IC is in CC mode. There, the Buck Converter will operate in Continuous Conduction Mode since the Average Inductor Current is greater than the ripple current. The issue is I'm facing is when the charging IC reaches CV mode. There, the output current is going to decrease, and the Buck Converter may end up in the Discontinuous Conduction Mode since the ripple current may become greater than the Average Inductor Current. So my question is if my Buck Converter operates in the DCM, how will that effect the charging IC? Will it just still operate like normal since the output Voltage on the Buck Converter will have minimal ripple (under 100mV)? Or will it turn on and off as the inductor current rises from and falls to 0A? Thanks.


texts: How can I flash the STM32F0 flash over SWD?

texts:
I am trying to program an STM32F0 from a linux based processor. I have connections to the SWRST, SWDIO and SWCLK pins.
I have most of it working well, but when I go to write to the flash memory locations, it fails with the DAP controller reponding with ACK FAIL. My current technique is to access the flash memory controller registers @0x4002200 and to write to flash this way. Just like the flash programming examples in the STM32 datasheet
I have verified that I am able to erase flash. When I capture some traffic from my ST Link programming the part, it seems to use a very different approach that i can't figure out, it seems to be writing to addresses @0x20000000. My flash is @ 0x08000000.
Does anybody have experience with this? Is my approach completely wrong?


texts: LTDC data starvation during simultaneous SD-RAM and NOR Flash access with STM32F429 rev 3

texts:
Application details:

SDRAM is used as the LCD frame buffer.
Memory for 2 LCD frame buffers are allocated(double buffering) in SDRAM. LTDC will be always accessing one of the frame buffer in the SDRAM for updating the frame. The new data(which is to be shown in next frame) will be updated in the other frame buffer area which is not being used by LTDC at that instant.
I am storing all the static images in NOR flash.
My application needs simultaneous access to SDRAM and NOR flash which is supported by the controller(I am using STM32F429 silicon version 3).

Issue:
Whenever the application executes a copy operation from NOR flash to SDRAM , FIFO underrun error  occurs in LTDC and the images in LCD are getting distorted for some time.
I got to know that LCD controller is denied SDRAM access for a time, long enough for the LCD FIFO to become starved.

•        I tried reducing the LCD clock then the images are getting displayed without any distortion.
LCD’s typical working frequency is 30 MHz . If the frequency is reduced I am seeing some dimming in LCD.
From LCD datasheet it will take 18.29 ms to update one frame in LCD at 30 MHz LCD clock. i.e.,  frame rate will be 54.65 fps.
At  24 MHz LCD clock, it will take 23.1 ms to update one frame in LCD . i.e., frame rate will lower to 43.29 fps.
I would like to keep our frame rate above 50 Hz.
The contents of SDRAM and NOR flash are verified and found to be valid.

SDRAM_CLOCK_PERIOD used = FMC_SDRAM_CLOCK_PERIOD_2 ( 2*Thclk) ( HCLK = 168 MHz)

•        When the LCD frequency is increased to 40 MHz in ST evaluation board, we were able to find same issue.

It is taking more time to copy an image from NOR flash to SDRAM in my custom board compared to evaluation board.

Queries:

Even though same FMC configuration is used in both boards, time to copy from NOR to SDRAM was more in my custom board. Is it because the SDRAM data bus is just 16 bits?
Can I resolve the issue if I use an SDRAM with 32 bit data bus?
What is the maximum frequency in which LCD can be operated in this configuration ? (simultaneous access of SDRAM by both LTDC and NOR flash).
How can we measure the actual time required to copy from SDRAM to LTDC controller?


texts: Effects of DC offset and loading at the input of an envelope detector (simple diode demodulator)

texts:
I am currently designing an AM radio. I am utilizing a diode demodulator

(https://upload.wikimedia.org/wikipedia/commons/6/6c/Simple_envelope_detector.svg)

to extract the envelope of my carrier signal. I am using a 1N34A germanium diode, which has a forward voltage of 0.3 volts. I would like to know what are the constraints on the DC point at the input of the demodulator. I believe it is necessary to have an offset of 0 V so as to avoid following the input signal at the wrong moment, but I am not entirely sure. Could I benefit from a DC offset? I'm also wondering about the effects of loading on my demodulator, since I will be connecting a voltage amplifier stage before it. Thank you!


texts: Ferrite underlay impact on chip antenna performance

texts: I'm designing a small wireless chargeable IoT device which also has TX/RX in subGhz frequency (LoRa). The idea is to stack everything on top of each other starting with charger RX coil, then ferrite underlay, then battery and PCB with chip antenna on top of it. While the RF channel is a challenge by itself in this situation, I realised that ferrite presence most likely will have an impact, and I'm trying to understand if it could be used for a benefit; or the presence of ferrite in near proximity to chip antenna will make it pretty much useless. This is rather a theoretical question or maybe someone had an experience with such composition and would tell straight away this is dead idea or worth going forward.


texts:
The pins in Port 1 has internal pull-ups when used for input.
The Mosfet is off and the drain is pulled high using an internal pull-up resister.

I connect an ammeter and see that the current (IL current) flowing to ground is about 15uA. I inferred that the value of the internal pull-up resister is 333k.

Now I connect a 10k resister and measure the current. I get 0.5mA (5/10k). What happened to the internal pull-up resister? Is not the internal pull-up resister and the 10k resister in series?

What is happening?
When I use external pull-up at Port 0, things appear as expected - Resisters in series and both resisters acting as voltage divider to create a voltage drop at the pin.

ps: I am using AT89s52.

ps: The same problem exists in port 2,3

ps: Here is the current for different resisters:

- 330 ohms - 15uA
- 1k - 15uA
- 100k - 50uA
- 220k - 22uA

The Max IL (as per datasheet) is -50uA


texts: 433 MHz Antenna - Balanced Dipole + Balun?

texts:
I've got three 433MHz receivers (all the same type) and I would like to increase the range on them (by which I mean the physical distance that the receiver can detect the signal from the transmitter). Changing the antenna on the transmitter (the little key fob/dongle thing) isn't an option for practicality reasons. One of these receivers is unfortunately housed in a sheet metal box (which can't be readily changed), so I would like to get the antenna outside the box, but I'm unsure as to how running it out of the enclosure interacts with the total length of wire used in the antenna itself, (i.e. the length exposed outside the enclosure vs total length to get back to where it is soldered to the receiver).
The receivers currently have short coiled wire antenna (they look like a spring, but are actually coiled wire). Since the receivers are stationary, I can take some liberty with a larger antenna. Googling suggests that a balanced dipole antenna with a balun is the way to go, with 178mm straight wire on each 'leg' (not sure of the right term) on the antenna. The problem is, I don't know the first thing about RF, so I haven't been able to discern what is a good guide for how to construct such an antenna.
Could anyone point me in the direction of a practical guide in this area that is technically sound?
EDIT - Hardware Details:
The transmitter and receivers are Elsema PentaCode series devices:
Transmitter: PCK43302
Receivers: PCR43301RE & PCR43302240R

https://www.elsema.com/pcr43302240r
https://www.elsema.com/pcr43301re

Basic details are on page 3 of this document:

https://www.elsema.com/wp-content/uploads/2019/05/pckmanual.pdf

They're frequency hopping spread spectrum devices, with a freq range of 433.100 to 434.700MHz.
Target range is ~200m, not quite line of site (elevation diff of about 10m over 150m due to small hill that rolls off).
EDIT - Directions to Transmitters:
So, the receiver's are stationary, but the transmitters are mobile. In the case of the gates, they're on access roads, meaning the transmitters can be sending a signal from either side of the gate (so, 180 degrees from each other). This is part of the problem, as a high gain antenna in one direction will hurt the radiation pattern 'out the back' (i.e. from the other direction), which isn't great given that the goal is to open it from both sides. Energy radiated 'to the sides' is wasted though. Is there an antenna design that can help achieve this?


texts: can somebody please explain why can't I say that SATA is a COM port, SATA is a serial port and COM port is a general name for serial ports, am I wrong? thanks in advance


texts: Maximum Current Gain Possible for a 100 mA PNP transistor

texts:
I have a pulse charging circuit where the maximum current is limited by the hFE of the PNP transistor (DTA144EE).  The typical hFE at room temperature is ~220 as shown in the plot below.  There is of course no spec on the MAX Hfe at room or any other temperature.
My calculations show that the circuit will correctly limit the current to 100 mA due to the current gain as long as the gain is not more than 500.
Is > 500 a physically realizable gain value at 100 mA for a low power discrete PNP transistor, or am I safe to assume that the gain will never be more than 500?  Note that I am operating in fast pulse mode, so 100 mA is in the safe operating area for the ~100 ms charge time for the circuit.
Note that PNPs with 500 gain exist, but I could not find one near that at 100ma of collector current.  The high gain was in the 1 mA range.
Also, doesn't gain typically go down at higher currents?


texts:
I plan to use a differential AD9235 to sample a signal that will range from 0.5 to 2.5V. Currently, I am trying to interface the ADC and learn how it works. As suggested in the spec sheet, I am using a differential driver before the ADC input. I have AD8132 - a similar driver to AD8138, that is in the configuration example in Fig.35 of the ADC manual. And here's how it's connected:

I set the SENSE pin to ground to get 2.0V differential span (I assume that's the range of the input signal), and the MODE pin to ground to get offset binary output (I assume that the lowest input signal will correspond to 0000 and the highest input will be converted to 1111).

Thus, I expect to input a signal 0-2V and expect it to be converted 0 to 2^12. I do get all the 12bit range, however, my input range is very small: for 1V and above, the output is zero. Decreasing the input voltage from 1V to about 700mV provides 2^12 output. In other words, my input range is only 300mV, as opposed to expected 2V span.

Measurements:

VREF = 1V

REFT =~ 2V

REFB =~ 1V

Given that I set the VREF to be 1V, the calculations are consistent with the equations on page 15 of the DAC specsheet:

REFT = 0.5(3V + 1V) = 2V   ->   right!

REFB = 0.5(3V - 1V) = 1V   ->   right!

Span = 2(2V - 1V) = 2 * 1V = 2V right!

So, why is my voltage input span is only 300mV? What am I not understanding correctly? What should I do in the future to be able to input 0.5-2.5V signal?

Also, why would I even care about VREF, REFT, and REFB? Why those pins are made external?


texts: 1/4" TRS cross-coupled output with bypass capacitor. Is TRS jack wired for cross-coupled or not?

texts:
I wrote Alesis to get the specs on my mix board main out. Here is what their engineers said:

  The main outs are cross-couple, capacitor bypassed, single-ended output, for a TRS jacks.

My cable builder sent me the following chart to pick the correct connectors:

http://www.rane.com/note110.html

I am in need of two 1/4" TRS output (mix board) to RCA input (amp) cables. After looking at the above referenced chart it is obvious I need #12 cable design. However, you will notice that there are two options on #12 for cross-coupled and non cross-coupled (cross-coupled jump shield to ring and non cross-coupled no jumper) of which no one, including my cable builder and Alesis, seems to know the answers to the following questions.....

My questions are:

does a bypass capacitor (decoupling capacitor) on a cross-coupled output negate the need for the corresponding 1/4" TRS jacks to be wired for a cross-coupled output?
or, is a cross-coupled output always a cross-coupled output regardless of a decoupling capacitor whereby I should have the 1/4" TRS jacks wired for a cross-coupled output?

I assume the answer is number 2 above, but not sure so I am hoping to get confirmation here. And, I understand that either cable will work. However, the cable builder says it always better to get the cables built to match the exact output and input specifications to eliminate potential problems.


texts: Using an opamp with fractionnal gain with supply less than input signal

texts:
Let's say we have an AC signal that can swing from -15v to +15v max peak to peak. If I use an opamp with the power rails to -5v and +5v, can I get a non clipped output signal if I use a gain of 0.333? Or will op amp failed to recognize anything above/below +/-5 V at it's input even if the required output is within range?

Do I need to have my opamp's power rails and specs within the input range or the output range provided that the output have less peak-to-peak swing than the input with my gain of 0.333?

The signal I'm talking about is a low, signaling level (about 1mA max) with varying frequencies, like an audio signal.


texts: Do bi-directional level converters connect either input directly to ground?

texts:
So I have the following circuit, which is a bi-directional level converter:

I am using it to convert a 5v logic signal (which at high is actually 4.2v and low is ~0.2v) to a 3v3 logic signal. I have already tried my own, one directional level converter, like this:

simulate this circuit – Schematic created using CircuitLab

The problem is, when I use the one directional converter, the 5v input is connected directly (except for 3K Ohms of resistors) to ground, which causes the signal [from the 5v] to drop to 0v. Also, an LED on the board that the signal is coming from turns on. The board that I am using is this board and the output/signal I am using is the LB (Low Battery) pin, which is pulled to BAT, which is anywhere from 4.7v-3.2v, unless the battery drops below 3.2v, then LB drops to about 0.2v.

So my question is: Will the bi-directional converter have this problem? Will the input ever be connected directly to ground?

If so, how can I do this so that the 5v signal can be used as 3v3, I was thinking of using a MOSFET, where the base is the 5v from here.
How can I convert this ~4.7v signal (which is pretty much 5v logic even though it's really analog) to a 3v3 digital signal?

Finally, I am really REALLY dumb when it comes to circuitry, so try to dumb things down a lot please, thanks.


texts:
I just recently bought a OPA350 OP-AMP due to its fast recovery speed that I need for my application (Precision Rectifier), it just arrived today and I went to go test the circuit. However weir behavior is starting to surface at high frequencies...but this time it's the Vpk-pk.

Datasheet: OPA350

Frequencies of (100Hz-10kHz)

Frequencies of (20kHz)

As you can see the \$Vpk-pk\$ took a beating at 20kHz and I thought this was due to the bandwidth of the OP AMP, however it's stated to be 30MHz. It also gets much noisier as well.

GBW EQUATION:

\$F_c=\frac{30MHz}{1}=30MHz\$

so the flatness should decade 6dB/sec after 30MHz ish, but why is it doing it around 20kHz?

SLEW RATE EQUATION:

\$SR = 20kHz*2*\pi\$
\$SR = 0.127V/uS\$

The OP AMP is rated for 22V/uS

Schematic:

simulate this circuit – Schematic created using CircuitLab