texts:
Am looking to use a fuse tap to run a dash cam. These are instructions https://www.lumision.com/wp-content/uploads/2015/09/Micro2-Fuse-Tap-Instructions-e1441486778366.jpg for a fuse tap and consistent with the common recommended way to install. Basically, this shows the fuse tap powering devices on the original circuit and the dash cam in parallel. A more controversial way among dash cam installers is to install the fuse tap in series. That is the power end is switched around. The idea for the latter is it would allow for better protection for the supply wire going into the fuse box.

Can someone who is an electrical engineer comment on the pros and cons of each?

Update/ Follow-on Question (based on answer posted):
I wish to say that I am not an engineer so my level of knowledge is very basic. When you say that there is no benefit, wiring in series does not protect the supply wire? Please confirm. The goal is to avoid an eletrical fire which would entail replacing high dollar auto wiring. The sub $200 dash cam is expendable IMO. If wiring the controbersial way doesnt protect the supply wire then certainly the confusion is not worth it.


texts:
Does anyone know of a way I can use sequential statements in VHDL without using the traditional if, case, when statements?

I am building an 8 bit word splitter that will then pass a 4 bit nibble to a hamming encoder, then after that, will send the other 4 bit nibble to the hamming encoder.

I cannot for the life of me figure out how to use the same parity bits on both 4bit nibbles to give separate outputs and in the same process.

the only thought I have is that instead of writing for example P1 <= nibble3 xor nibble5 xor nibble7 -- would be to use the truth table and then use a when statement?

thanks


texts: How to implement a xor gate with nand gates

texts:
I try to resolve a problem, how to implement a xor gate with nand's gate.

A xor B = A'B + AB'

So, this becomes :

A xor B = A'B + AB' + AA' + BB' = A(A' + B') + B(A' + B') = (A + B)(A' + B') =

(with De Morgan apllied on the second term)  = (A + B)(AB)' = ..... ?

In this point i am blocked.
If someone can help me, please.
Thank you.


texts:
I want to try and make a power monitoring system for an off-grid solar system using a micro-controller (esp8266). I started by monitoring the battery voltage (using a voltage divider and an ADS1115) and the current between the battery and the PWM charge controller using an ACS Hall effect current sensor.
I connected the battery ground to the ESP ground to measure the battery voltage.
Next step is to measure the current and voltage of the panel. Firstly, I thought to do the same thing with the panel (common ground panel-battery-ESP and current sensor), but then I disassembled the PWM charge controller and noticed the panel and battery positive terminal is actually connected directly to the battery positive terminal.

What will be the next step to measure the voltage of the solar panel? Or should I change the whole method?
Is there a way to isolate the micro-controller circuitry from the solar power circuitry to measure the voltage and amperage of battery and solar wires?

This is what it looks like now -

Would love any other suggestions!
Thanks


texts: Is this protection circuit designed well?

texts:
I have been learning about designing a protection circuit for one of the projects I am doing. Here is my first crack at it, please let me know if I have made any mistakes, and any advice is appreciated! P.S. the parts are not finalized, and were mainly chosen for convenience not due to spec.

My specifications were to have no significant power loss, while maintaining reverse polarity protection. I have a 3S 11.1 lipo battery, where the voltage level is crucial, thus I cannot simply use a series diode. Would appreciate any advice on deciding which specific mosfet to chose here, as I prefer working with NMOS variety due to their simplicity and low Rds(on).

For the fuse, I decided for something simple and resetable, hence I chose the PTC, I have not chosen the specific dimensions, will probably have to make my own part in eagle. I have never designed a system with a fuse, so input here would be much appreciated.

The last part of the design is dependent on a wireless signal transmission from an external MCU. The MCU controls the relay, to provide an emergency stop if a user cannot turn the power off manually. I most likely will drive the mosfet using a pwm signal at the Gate to conserve power further. Does the mosfet I chose here matter that much? I understand the necessity of the series base resistance (to prevent ringing oscillations, and to prevent gate from charging to quickly), but would I need one when driving the gate with a pwm signal from a 16MHz clock?

I appreciate any help!


texts: Sampling circuit for decently high-accuracy ammeter?

texts:
I'm thinking about building a monitoring circuit for an existing residential power system. Currently there's a simple ammeter and digital voltmeter in use for some basic monitoring, but nothing fancy.

I'd like to augment this with something that supports some history and statistics. I've got some microcontrollers and LCDs lying about that I'd like to use for this, ideally. Here's a slightly simplified schematic for the system I'm thinking about trying building:

simulate this circuit – Schematic created using CircuitLab

Here's my concern: If I'm trying to track power use, then fundamentally, sampling with the A/D converter is giving me a box integration of the voltage difference across the shunt. Now, I can assuage my worries by using an A/D with a really fast sampling rate, but I don't know enough about the charge source input to be able to say how quickly the amperage will be changing. I suppose what I'm worried about is quick current spikes (<100μs) that regular sampling at 10ksps will miss.

What I'm considering is adding some filtering caps to the input, but since the amperage involved is quite high (>= 60A, and the shunt is rated up to 500A so higher peaks are definitely possible) I'm not sure that would be helpful. Am I just being very silly since A/D and amp error will contribute more to overall error than such peaks? Or would throwing a couple of low-ESR 100nF, 47μF, and 470μF caps actually make a significant difference? Is there anything else I should be concerned with? I'm quite the newbie when it comes to analog electronics, so I'm probably missing plenty of silly things. :)

Thanks!


texts:
I assume this rectangle around the IC is for RF shielding, but why when is it exposed? I have seen this occasionally and I am not sure of it's exact purpose or why its exposed.

Googling the title didnt help so I am here asking.


texts:
Need help use LM358 circuit with Arduino micrcontroller ADC input

I want to implement a LED fault compensation circuit. When a LED has failed, there will be an open circuit and no current will flow through the string. Hence, a zero current will be sensed at the RS and it will be feed backed through ADC to the microcontroller. The microcontroller will take response.

but I can't get the signal at ADC, please advice my circuit any wrong.

thanks

attached here


texts: If a circuit from a voltage source has a potentiometer to ground, does voltage increase or decrease when resistance does?

texts:
Below is a CRT circuit I am trying to fix, specifically the HV circuit.
In the bottom right corner, a reference voltage comes from the flyback and makes it's way to U701 on the HV. IN pin. My question deals with potentiometer VR722 (beside R722), going to ground.

As the resistance increases, what happens to the voltage? Does it increase as well?


texts: How to ignore simulation only ports when mapping to FPGA pins?

texts:
A design has a number of simulation ports that should not be tied to FPGA pins.
A VHDL example is shown in the source below, where the sim_only_* ports are for simulation only, thus should not be mapped to FPGA pins.
entity mdl is
  port(
    -- FPGA pins
    clk_i : in  std_logic;
    rst_i : in  std_logic;
    a_i   : in  std_logic;
    z_o   : out std_logic;
    -- Simulation pins only
    sim_only_in  : in  std_logic := '0';
    sim_only_out : out std_logic);
end entity;

The sim_only_* pins can be safely left unused by Quartus, since the inputs have default value.
When running Quartus, the mapper tries to map the sim_only_* ports to unused FPGA pins, which is not desired.
How can I specify that Quartus should just ignore the sim_only_* ports on the VHDL design?


texts: RE: RCR design in TRIAC circuit for inductive loads

texts:
I was working on a TRIAC based dimming circuit. Initially I plaaned to use a PCB mountable SSR (G3MB-202P), though this was a cheap but the device didnt allow me to do dimming with the same. I can only turn ON or Turn OFF the load. and the other SSR cost $$$(lots of them). So i decided to take a fairly cheap path of using an OPTO-DIAC and a TRIAC.

please find my design below.

I have actually copied the RCR circuit from an online blog. Can someone please help me with the design of this. I know that this circuit is a phase compensation circuit for the current and voltage(lags) due to the inductive load.

Thanks and regards.
Siddharth


texts: Does light of LED depend on current or voltage applied to it?

texts:
During a job interview, someone asking me this question: Does the light of an LED depend on the current through it or voltage applied to it?
This seems to be a very beginner question but in fact in background the reality is not quite simple from my point of view.
Everybody says that light of an LED depends only on the current passing through them. But the current depends on the ( applied voltage - cumulative voltages drop ) / the cumulative resistances of each loop. (Vdd - Vf ) / R = I(led)
I also know, that the diode (or LED) is not a linear device.
But from my point of view, current in circuit only depends on the voltage applied. Even for non-linear devices, or complicated things. For instance you cannot have current without voltage but you can have voltage without current.
So, in the end, from my point of view LED light depends on the voltage applied to it because the resulting current will alawys depend on the applied voltage to a given circuit.
Am I clear? How much am I wrong from your point of view?


texts:
I need to read 15 channels ADC. However my MCU is specific named STM32F042K6T6. I decided to use an analog MUX to read every channel from just one pin. But, I didn't read accurately the datas by writing these codes:

for ( z = 0; z <= 15; z += 1 )
{
HAL_GPIO_WritePin(GPIOA, ADC_CH_SELECT0_Pin, ( z >> 0) & 0x01 ? GPIO_PIN_SET : GPIO_PIN_RESET);
HAL_GPIO_WritePin(GPIOA, ADC_CH_SELECT1_Pin, ( z >> 1) & 0x01 ? GPIO_PIN_SET : GPIO_PIN_RESET);
HAL_GPIO_WritePin(GPIOA, ADC_CH_SELECT2_Pin, ( z >> 2) & 0x01 ? GPIO_PIN_SET : GPIO_PIN_RESET);
HAL_GPIO_WritePin(GPIOA, ADC_CH_SELECT3_Pin, ( z >> 3) & 0x01 ? GPIO_PIN_SET : GPIO_PIN_RESET);
}

When I decrease the repetition count of for, namely for (z=0; z<=2; z++)

The results is OK. But I can not read all the channels with that. Because of this problem, I decided to use an adc interrupt. I have set all the settings like ADC resolution, Cycle, right alignment, NVIC e.t.c. with STMCUBEMX. These codes are here:

static void MX_ADC_Init(void)
{
ADC_ChannelConfTypeDef sConfig;
hadc.Instance = ADC1;
hadc.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
hadc.Init.Resolution = ADC_RESOLUTION_12B;
hadc.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;
hadc.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc.Init.LowPowerAutoWait = DISABLE;
hadc.Init.LowPowerAutoPowerOff = DISABLE;
hadc.Init.ContinuousConvMode = ENABLE;
hadc.Init.DiscontinuousConvMode = DISABLE;
hadc.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc.Init.DMAContinuousRequests = DISABLE;
hadc.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN;
if (HAL_ADC_Init(&hadc) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
sConfig.Channel = ADC_CHANNEL_0;
sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;
sConfig.SamplingTime = ADC_SAMPLETIME_239CYCLES_5;
if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
}

And I know that when the configurations are OK, I need to Start ADC INT with that code:

HAL_ADC_Start_IT(&hadc);

I have inserted the code within main function above from while.

And I know that after every reading cycle, our program must jump to that function:

void HAL_ADC_ConvtCpltCallback(ADC_HandleTypeDef* hadc)
{
Temporary_ADC_Value[0] = HAL_ADC_GetValue(hadc);
}

When I try to read adc value from Temporary_ADC_Value[0], I have not experienced a appropriate value. What may be the problem about issue? Is there any point that I forget? That issue is important for me. Thanks in advance.


texts:
I have a device with a lcd (1602) that needs to be replaced but I'm not sure about finding a compatible one.

The part number is BC-1602B-SBYA-I-B-A00 and according to the specification pdf it has an ST7066 controller which should be compatible with the HD44780 and operates with 5v. But looking at the usual lcds they have their pins on the top side of the pcb, while mine are on the bottom also starting with the pin 14. I don't know if there is reason for that like compability.

My experience is close to 0. Could I have a problem with the usual displays for arduino?(connected through cables) If not, what features should I look for?

Thanks


texts: Winding arrangement in small toroidal mains isolation transformer

texts:
I got a 0.3A 220/220 toroidal transformer with the primary (red wires) on the outside and the secondary (black wires) on the inside.
What is the reasoning behind this arrangement in this particular case if any (and if it's even a standard)?


texts: I am hacking a commercial board which uses ADS1130 for analog to digital conversion. Wiring in commercial board is a bit different than what is specified in datasheet. In commercial board, Pin number 4 is connected to Pin nummber 1 i.e 4 is connected to VCC. But datasheet indicates that pin number 4 is DGND. And commercial board operates absolutely fine without any problem. I need to design a layout for my ADS1130 too. So whether or not to copy the commercial board layout, I am in great dilemma. Here is the datasheet. Any suggestion would be appreciated.


texts: ASIC Solution for Digital Closed loop Buck Converter Control

texts:
I am implementing a Closed loop Current Mode Control Buck Converter on a dsPIC Microcontroller which has an output of 3.3V and unregulated input of 5V.

I am doing digital control, so I implemented the PI controller as 2p2z controller.

Someone asked me why I am doing all this? Is there not an ASIC chip which would already have code for 3.3V output and an unregulated input voltage range? The ASIC chip would have the control loop already implemented with all the interrupts and stuff.

Is there such a thing in market? If so, why is ASIC preferable or why not?


texts: how to reduce DC voltage using resistors?

texts: How would one go about using a 12 V DC power source to power something which needs 4.5 V DC using resistors? Is there a way to determine how much adding a resistor would drop the voltage?


texts: Optimal method for switching power to a DC motor spindle

texts:
I'm trying to use a 5V DC signal from a microcontroller to electronically switch power to a DC spindle (for use within a router I'm trying to build). The supply I'm using is a 48V-DC PSU (8.3A rating).

What would be the most suitable and long-term-safe way to accomplish this switching?

Based on my research, I could use a Solid-state relay or a Mechanical relay to achieve this, but I wanted to know if this is the optimal solution and, if so, whether SSR or Mechanical is better in this kind of application.

Assume I only need ON/OFF switching (i.e., no need for PWM/speed control of the spindle).


texts: Feedback on PCB design -Beginners request

texts:
I have started trying out PCB designing very recently and I found it extremely interesting and wanna learn more about it. A week ago I was working on a RF remote project and I have attempted to design a PCB for it. I would mean a lot for me if you guys can take a look at it and give your honest feedback about it. Good or bad feedback I am eager to hear it all. If it is very bad, am ready to get roasted for it as well.

I have already got the answer for 90 degree angle routing. I need some inputs like

Does the components are too crowded and difficult to make the PCB in real time?
In the receiver PCB, I have used two different PCB trace widths, Should i keep it uniform throughout the board? or it doesn't matter?
Does using Via is bad for the design?
Any specific component in a board I should take high care when placing in the board?
How well does the top layer routing works with through hole components, I have heard that it will give trouble when soldering the components to the finished board Is that true, should i try and avoid that?

Any other piece of advice is very much appreciated. Am not sure that these kinda feedback request can be posted in this community, if not kindly apologize :)

RF remote using HT12E Circuit Design:

PCB for the above circuit:

RF remote receiver and control circuit design:


texts:
I'm having a little trouble understanding this worked solution.

My understanding of superposition is that we "turn off" every independent power source except the one we
plan on analysing, then we superimpose all the individual results to get the real result.
But it's in the nodal analysis when we leave the current source on and turn the others off
that's getting me.

The solution implies two node voltages when to me there are 3 junctions/nodes. They seem to just follow the current through the 8 ohm and the leftmost 4 ohm resistors all the way to the ground. Is this because there is no branch between the ground node and the other node voltages?

Also, is there a reason other than time saving that we use mesh analysis for the voltage sources and node analysis for the current source?

Sorry for all the questions, but when we remove the current source, I've never understood how the remaining open circuit works. Do we simply disregard the wires that remain in figure (b)? If yes, why do they leave it there?

One last thing I am little shaky on choosing at which junction the make a reference node, is there a reason the solution chose the one it did?

Thanks so much!


texts: Switch between 2 voltage dividers depending on input voltage

texts:
I have a power managent IC that has features of Under and Over Voltage Protection through the EN and OVP pins. These pins are enabled by manipulating the voltages on the pin via a 3-resistor voltage divider.

Now my circuit takes in two configurations for the Li-ion battery for power, either at 3.7 volts (using 1 18650) or at 7.4 volts (using 2 18350). This makes it tricky for the power management IC. It is possible to use two of the PMIC for the different configuration making sure that only one is always active. But it take a lot more components and not much more GPIO pins for monitoring.

I was wondering if there is any way to switch between two different voltage dividers depending on the input voltage. Without using timers, I do not want to keep adjusting it.

The input voltage share the same line, but if the voltage is let's say lower than 5V, it will use the voltage divider on the left and if it's higher than 6V it will use the divider on the right.


texts: How to choose right PWM frequency for LED?

texts: I want to control LED's brightness with PWM (via BJT transistor). What frequency of PWM should I choose?


texts:
My plan is to build a discrete CMOS inverter(just out of curiosity) out of two complementary MOSFETS. Hence, I am currently looking for a nice pair of complementary MOSFETS, which is quite hard, because there is such an enormous variety. Furthermore, it is really important, that there is a spice model available for the MOSFET chip.

Do you think that this chip is the "right" one(would do a good job)?
https://www.fairchildsemi.com/datasheets/FD/FDY4000CZ.pdf

Best regards,
Pearson


texts: Q: ultrasonic sensors - distance detection

texts:
I have a question about ultrasonic sensors.

By connecting the car parking sensor to the scope I always get the same wave. But by changing the distance from the sensor, the parking system respond as expected (according to my distance from the sensors)

From my understanding i should see the sent wave (which i do) and after some time the echo signal (which i don't). if sound travels at a speed of 340 m/s (2.9ms for each meter) and i am 0.5 meters from the sensor i expected to see the echo signal attenuated after about 2.9ms which i don't although the car parking sensor does show i am 0.5 meters from the sensors. i thought perhaps the signal is highly attenuated, going as low as 50mV but all i see is noise. could it be that the frequency is inside the noise? even the noise does not appear to change.


texts:
I currently have the following verilog expression...

wire [15:0] address_delta = (rx_address_in * 8 + (rx_eof_in ? rx_len_in : 8)) - (seek_address + OUT_BYTES);

rx_address_in is 13 bits and OUT_BYTES is a parameter which is an integer constant (so I guess 32 bits).  I am assuming the 8x multiplication will get optimized into a left shift of 3.  If this is a bad assumption to make please let me know.  I am using the latest Vivado.

Right now my design is having trouble meeting timing.  Although my address_delta is only 16 bits, since I am using 32 bit constants inside the expression which I think might cause the operations to be carried out at a higher precision than necessary.  How would you rewrite this expression for efficiency or is it fine the way it is?

I am thinking I could do something like this...

wire [15:0] seek_end = (seek_address + OUT_BYTES);
wire [15:0] address_delta = ((rx_address_in << 2'd3) + (rx_eof_in ? rx_len_in : 4'd8)) - seek_end;


texts: full duplex serial communication with a laptop using ATMEGA8 USART

texts:
Can anyone please tell me how to use ATMEGA8's USART to establish a full duplex serial communication with a laptop using a USB-to-Serial Adapter.

I am working on a project in which I need to display accelerometer reading in a gui. But the problem is I want to start sending the accelerometer data to laptop only when i send a character 's' to my ATMEGA8, which will then initiate continuous transfer of Accelerometer reading to the laptop. Also during this process, I want to send another character 't' to ATMEGA8 to stop the accelerometer data transfer.

Please help...

Thanks.


texts: What is going wrong in this circuit which supposedly should step down AC to arduino friendly voltage?

texts:
So I'm using this circuit

but when adapter output is disconnected and only midpoint terminal of the transformer is connected the Arduino input pin reads some mV. mid point reads perfect 2.5V. What am I doing wrong?


texts: Is there a way to use the i2c interfaces on a standard PC mainboard to control a device?

texts:
I have attached a few sensors and an LCD display, all of them having an I2C interface, to my raspberry pi, and written a software on the pi to read/write them.
Right now, I have a network daemon running on the pi to retrieve data to my PC, and control the display from the PC. I would like to, if possible, omit the pi, and control the devices from the PC directly.

The PC has several /dev/i2c* devices, and I can use i2cdetect to list them:

root:~# i2cdetect  -l
i2c-3   smbus       SMBus PIIX4 adapter port 4 at 0b00  SMBus adapter
i2c-1   smbus       SMBus PIIX4 adapter port 2 at 0b00  SMBus adapter
i2c-6   i2c         NVIDIA i2c adapter 5 at 8:00.0      I2C adapter
i2c-4   i2c         NVIDIA i2c adapter 1 at 8:00.0      I2C adapter
i2c-2   smbus       SMBus PIIX4 adapter port 3 at 0b00  SMBus adapter
i2c-0   smbus       SMBus PIIX4 adapter port 0 at 0b00  SMBus adapter
i2c-7   i2c         NVIDIA i2c adapter 6 at 8:00.0      I2C adapter
i2c-5   i2c         NVIDIA i2c adapter 3 at 8:00.0      I2C adapter

So, there are some I2C adapters on the Southbridge, and some more on the video card.

Are any of those likely to be "visible" somewhere I can get to them without having to solder my mainboard? If so, where would I have to look?
i2cdetect -y finds several devices attached to i2c-0, but none to i2c-1, i2c-2 and i2c-3, so I guess using one of the latter should be safe to use as long as I'm not adding any other peripherals which might use them.


texts: Sizing transistors (W/L) for an IC Operational Amplifier

texts:
I have to design a simple operational amplifier in a similar way to what has been shown to me in a lesson at my university course:

I have some basic doubts about how to size the transistors (W/L) and I find online and on the books only explanations which are confused, unsystematic, and not with simple words. Precisely:

1) how can I size the transistors for the current mirror at left? I have seen on the web that they (M9, M10 and all other transistors which mirror the current) are usually sized with L = 3Lmin or 4Lmin in order to increase the output resistance. But this must be compensated with a higher value of W. My question is: why? My possible explanation is that to get a fixed current at the output, if W/L is lower, we need higher VGS, and so there is higher risk to make the transistors work in triode and not in saturation.

2) Which is the role of M11 and how can I size it?

3) How can I size the transistors of the differential pair (M1 and M2)? In this case they have been sized with minimum L and W

4) It has been asked to me to size the differential pair with transistors with transconductance gm = 200uS. Now, in saturation its expression is:

\$g_{m}=2k(V_{GS}-V_t)=\mu C_{ox} W/L (V_{GS}-V_t)\$

where:

(V_{GS}-V_t) may be evaluated by a simulation
W/L are chosen by me
\$\mu\$ and \$C_{ox}\$ are unknown

so there is not the possibility to choose W/L to get the desired \$g_m\$ with this math analysis. How can I see the value of \$g_m\$ with the simulator, fixed W/L?


texts: PCB Layout, Functional vs Actual Pin Order

texts:
I'd like to continue this conversation here:
CAD Schematic pin arrangement approach

Basically, there are 2 major ways to do schematic symbols, either with true pin order or by grouping pins by their functions.   More people seem to advocate functional groupings over true pin order because of the clarity it can give your schematic.

The first PCB I did a few years back I used functional groupings on the schematic, then when I switched over to do the PCB, the number of crossings and vias made it a complete mess.  Since then I've made every single schematic symbol true pin order, then focused on making sure as few lines on the schematic cross, meaning minimizing the crossings on the PCB. This has produced very clean and efficient boards, however, I don't think my method will scale well when doing very large boards.

For those of you that use functional pin groupings, how the hell can you produce an efficient PCB without too many crossings or vias? For instance, PORTB on an ATmega could be spread out on all 4 sides of the IC.  If you group them together as a functional block you may assign them to one device then have an absolute nightmare when you switch over to do the routing.  This easily could've been avoided if you noticed: "Hey, PB0, PD7 and PD6 are all right next to each other, maybe that'd be the better choice."

So I'm not trying to convince anyone of anything, I just recognize that the more professional route is functional pin groupings, but I simply don't know how to translate that to an efficient PCB.

I've included one of my schematics as an example of how I do it.  This board was 1 square centimeter and so every single via was major real estate.

Thanks in advance.


texts: I can't understand how does the circuit work? Can anyone help me?


texts:
I want to connect 4 bulbs in parallel. The bulbs need 12V DC and rated 18 watts. P=V*I, that means I=1.5 A on each bulb. From that the resistance of the bulbs are 8 Ohm (R=12/1.5). The circuit will look like this:

simulate this circuit – Schematic created using CircuitLab

But in real life wires have resistance too. The resistance of my wire is 12 mOhm/m. I need around 12 meters of this wire. The bulbs will be 3 meters from each other. If I calculate this, on the last bulb only 11V will fall and 1.375A will flow through. Which is only around 15Watts.

simulate this circuit

If I want to connect more bulbs (lets say 8 or even more) there won't be enough Voltage across the bulb and it wont work. Did i calculate it wrong? How is this problem problem solved in real life?


texts: Is it possible to build homemade storage device?

texts: From what i know, HDD is built on magnetic recording technology. My question is, is it possible to create a storage device from scratch (USB, HDD, etc.)? I'm just eager to try out building some electronic devices...


texts: Why can't regs be assigned to multiple always blocks in synthesizable Verilog?

texts:
The accepted answer to this question notes that "every reg variable can only be assigned to in at most one always statement". It's clear that in a lot of cases assigning a reg to multiple always blocks is meaningless. However, it's seems that there could be hardware-meaning instances of a reg in different always blocks.

For example, what if a same reg is assigned to always @(posedge clk1), always @(posedge clk2) where clk1, clk2 never beat of the same time? There would be no race-condition.

Why is there a "hard rule" concerning regs in different always blocks?


texts: Switch on an esp8266 with a npn transistor (2n2222A)

texts:
this is my first question here, so I would like to ask you to kindly point out my mistakes regarding the question instead of just pressing the down arrow. That way I will have the opportunity to correct my mistakes on the next question and keep up the high question-answer quality of this forum. But now to my problem:
I'm currently working on a battery powered project using the Attiny85. Because I want to have the possibility to send push messages to my mobile phone I decided to add an Esp8266 D1 Mini to the circuit. To save power (I know that I could also put the Esp into deep sleep mode, but that would be boring and I wouldn't learn anything new ;)) I thought it would make sense to switch the Esp on and off immediately after sending a message using the transistor 2n2222A and the Attiny. But unfortunately the following circuit does not work:

The funny thing is that the circuit above works when I replace the Esp with a Led. Also reversing the polarity (i.e. instead of switching + with the transistor, - ) works with the Led without problems, but not with the esp.
Many thanks for your ideas in advance


texts: Can you tell me how the op-amp in this DMM circuit works?

texts: This is a autoranging DMM circuit. Specifically I would like to know what the lower op amp is for. It seems to be a non-inverting configuration with the (+) terminal at ground, but I don't what it does. Also, what are the symbols with the dashed circle? Why does the + input of the opamp go to one of them?


texts: Interfacing a mains referenced AC measurement circuit with a PC

texts:
I need to connect an AC mains referenced measurement circuit with a notebook and I wanted to know if its safe to do that without an isolator. The measurement circuit primarily steps down AC voltage and current and then runs it through a set of instrumentation amplifiers (powered by a 5V wall-wart) to give a single-ended output which is then connected to the ADC pins of a MCU (which is a TI Launchpad). Now can I safely connect this LP to my Notebook USB without any isolator between them?

I saw an eevblog video where Dave shows that in a notebook, the charging pin 'ground' and the earth pin on the mains plug have very low resistance between them (essentially shorted). On my Dell notebook thats exactly the case. In that case, would the shown connection arrangement work and be safe? The first USB port on the extreme left is the notebook's USB port.


texts: Is it possible to mount a 7-Segment on an FPC and what points need to be considered?

texts:
I am designing a project with a flat flex PCB, in which I would need a 7-Segment display similar to below picture.
I would like to avoid to add an extra PCB with a connector or hot-bar just for the displayand I would also like to avoid a rigid-flex design.
So I thought, why not put it directly to the flat flex...
However what felt like a brilliant idea, after I started searching I found little to no examples, of even through hole components being put on a pure flat flex PCB.
So my questions:

Is is possible to do?
If so, why isn't it done often enough to find plenty of examples?
Are there problem or issues to be expected?
Is it feasible for mass production?
Does it, same as for SMD components, require to add stiffener under the flat flex?


texts:
I have been working with enhancement MOSFET for a long time. But I have never seen any circuit using a depletion-MOSFET.

What are some typical use-cases of the depletion-MOSFET?


texts: Problem simulating current controlled current source in LTspice

texts:
I've been trying to simulate the following circuit in spice. (I'm plotting the voltage over R7)

Everything is okay, and works as expected until I change the gain of the current controlled current source to a value that's greater than 58. And I should simulate this with a value of 290. Any idea on how to fix this?

Here is another photo with the gain in 290

When I set the gain in 58. Spice trows the following error "spice analysis: Time step too small; initial timepoint: trouble with node n002" The node n002 is the node that connects R4 with R1. For greater values the error doesn't show up anymore but the result is the one from the picture.

Thank you for any help you can give me on this issue!


texts:
I'm an embedded software developer working on a personal project using RFID. I'm attempting to read a passive 13.56 MHz tag moving at 100ft/sec. Given the limited range of passive tags, I'm looking for something that can read a tag in under 10ms. Is this possible? If so, would it be possible to reduce the latency further? I've worked with the MFRC522 reader module hooked up to an arduino uno and couldn't get anything better than ~15ms.
Any advice here would be greatly appreciated.


texts: Circuit diagram question - microcontroller input protection

texts:
I'm new to electronics, and I would like someone with more experience to look at my diagram.

The circuit consists of:

a 5 V regulator (from a 12 V input) that powers the microcontroller
a pull-up resistor, and
a transistor.

The "0 V to +80 V" input is idling at ~12 V, but occasionally drops to 0 V (for a period of 10 ms) followed by a ~80 V spike.

The goal is for microcontroller to count those spikes, by reading the value of PB0 (pin 5).

My question is: Will this work? If not, what do I need to make it work? :)

Circuit diagram:

Update

Input signal:

(Original image source: tinypic.com)


texts: Use of 100K ohm resistor along with 0.1uF capacitor?

texts:
In the circuit diagram below, why is there a 100KΩ resistor (NOT R2) connected to the capacitor? To my understanding the capacitor-resistor act as a high pass filter to block the DC offset of the microphone, but since only the capacitor blocks DC why is the 100k resistor used? According to the author of the video (link below) he said, the 100k is used "not to overload the microphone's un-amplified output". I don't get this part.

Also, can only a capacitor be used in this circuit or any other circuit without the 100k resistor?

Passive RC high pass filter tutorial!


texts: Why use both big polarized cap and small non-polarized cap in the TB6612FNG DC motor controller terminal?

texts:
In the datasheet of TB6612FNG DC motor controller, Typical Application Diagram section.

Both DC sources are smoothed by caps. But I don't understand why there are two caps in each position.

The polarized cap is 10uF and the non-polarized cap is only 0.1uf. Which is a hundred time smaller than the other, so I guess it is not for making a specific capacitance.

Is the small cap for shielding off back emf spike? But wouldn't the electrolytic cap break in such case?


texts: How to properly design LC bandpass filters?

texts:
A little disclaimer. Electronics is a hobby to me so I learn it on my spare time. This leads to certain knowledge gaps that professionals might not have.
I want to build a good filter using SMD components. I started from some existing design I found online and trying to modify components and parameters in order to achieve the good results.
I lack in theory heavily so I would welcome a good literature references.
I found LTSpice and started playing around. I learned how to step through parameters.
The only thing that concerns me is impedance matching. CT/CB are forming the divider and I want to optimize schematic for optimal Q while preserving 50 Ohm i/o impedance.
The problem here I don't know how to do these optimizations while I remain within assortment of available components. Plus there are tolerances on them which also should keep the schematic working fine.

My question is - what I should read or where to find an information or methodology to design such filters properly and suitable for manufacturing?
Answers for questions:
Type of the filter - band pass filter for ham-radio transceiver.
So I have low signal levels.
Low losses are very important because the signal will come from the antenna.
Frequency range: HF, 1.5MHz-30MHz. Bandwidth depends on the band. I am not sure about the ripple, the lower the better but I think 1db should be ok.
Source has a  series resistance set to 50 Ohm in Parasitic Impedances section.
My load is a resistor of 50 Ohm.
With regards to the components Q - ideally I want to use a inductances table from manufacturer which already has a Q measured. But I don't know how to use this table inside LTSpice because it has inductance+DCR+Q at the same time. Plus, there are tolerances that affect filter performance.
Also, the filter works at the higher impedance than its input output (CT/CB make a some sort of capacitive transformer).
Right now I am pretty much lost because I am trying to find the best fitting curve with lowest losses. Plus how to keep input/output impedance the same 50 Ohm?
This is what I have simulated so far:


texts: Altium Designer Rules - Nets with different width

texts:
I would like to know if is it possible to build up a rule that treats a single net in different way.

I have some circuits in which some nets needs to be dimensioned for high current. So I create a net class and I assign to that net class the desired width. So far, so good.

The problem is that not all tracks of that net need to this width for high current (for example think about parallel components). So I would like to make a rule that makes the net bigger only where it needs.

Is it possible?

I've tried with some rules but without any result: I made the Net Class with all net for high current and then a Component Class with all and only the component connected to high current wire. I make this rule: InNetClass('HC') AND InComponentClass('HC')... but obviously it doesn't work because the nets of class HC belongs also to component outside class HC.

How can I solve this?


texts: How can I do a frequency sweep when the frequency modulation index is dependent on the amplitude?

texts:
I have a question regarding frequency modulation and the modulation index.  I know that the modulation index can be given by

$$\beta = \frac{\Delta \omega}{\omega_m}$$

So the value of the modulation index is highly dependent on the value of \$\omega_m\$.

When we calculate the coefficients for Bessel functions, we need to get \$J_n(\beta)\$, which is a function of \$\beta\$.  So that means, whatever \$\omega_m\$ we choose, will affect the value of \$\beta\$.

So then my question is how can I do a frequency sweep then with \$s = j\omega\$?  The \$\beta\$ value is always changing and thus so is the amplitude of my signals.  Can I just choose the lowest value of \$\omega_m\$, and therefore, the largest \$\beta\$ as my worst case, and thus have "constant" J values?  Hope this is making sense.


texts: Does LED "luminous output" follow a continuous curve to Vf=0, i.e. follow forward current?

texts: I was wondering whether a bi-directional opto coupler could measure absolute value of AC voltage this way.


texts: Use a current monitor IC or roll my own?

texts:
I'm looking to measure current consumption of my microcontroller as an in-built feature of the final design. Should I buy and use high-side current monitors that are available on the market (e.g. Zetex ZXCT1009)? Or is it possible to build one out of discrete parts that's cheaper and better?

Device operating out of a lithium polymer battery, so 3.7V typical only. Drawing around 0 to 30mA.


texts: Positive LDO used to regulate negative voltage

texts:
I need a quiet LDO with very low (few microamp level) quiescent current, but this does not seem to exist as a negative voltage LDO. So the question is, do I need a negative regulator, or can I use a positive one instead, as shown here? The circuit is showing a ground symbol on the output of the LDO. Aside from swapping the GND symbol and the OUT label (which makes no difference to SPICE), it is an entirely conventional use of the LDO. So naturally, it seems to simulate fine. It regulates to approx. -5VDC on the OUT node.
To make my question more specific:
a) does anyone know a reason why this should not work as expected?
b) if so, what problem should I expect and why?


texts:
i have been troubleshooting a guitar amp that blows the 125 ma slo blow fuse upon startup. The fuse does not blow when the amp is brought up to 115 VAC with the Variac. However when starting the amp without the gradual Variac increase in voltage the fuse blows. I removed the 100 uf 350 volt filter cap and installed a 33 uf cap. The amp now starts up without blowing the fuse. However I see a millisecond filament glow when turning the amp on. My question is: Is the filament glow stressing the fuse, or just me?

update:

Thank You for your response. After a half dozen slow start up observations on a pair of these amps exhibiting the 125 ma fuse glow or blow, I thought to replace the first 100 uf filter cap with a 20 ufd cap. The problem of fuse blow at normal start up and fuse glow at slow start up was eliminated.


texts: Arduino : Finding ADC & Pin Change in same pin

texts: I am using ATMega 328. I'd like to get ADC & Pin change interrupt in analog input pins (A0 - A5). ADC is working but how to make the electronic circuit for Pin change?


texts: Why transistor doesn't oscillate in this configuration?

texts:
This probably sounds funny but I'm curious.

simulate this circuit – Schematic created using CircuitLab

Current will flow between base and emitter. This will switch the transistor on and current flows from collector to emitter.

But this should create low potential at base probably? Because once transistor switches on all the current should flow through collector and emitter. Transistor should turn off due to no base current and current flowing through collector and emitter should stop. Again current will flow through base.

Shouldn't this happen to transistor and wont transistor oscillate?


texts: Load cell required with resolution of 1 gram

texts:
In a project, I want to measure weight with the resolution of 1 gram. Things I want to weigh, are max of 6 grams and I need to diffrentiate between a 5 gram thing and a 6 gram thing.... So I would require a Load cell with resolution of 1 gram.

I searched in Local Market as well as online but I couldn't find a good one.... Can anybody have suggestions what can I do?? Or Links where such load cells are available will be way good....If anyone used such load cells then...then I would be the happiest person on earth! :)

Thanks!

P.S. I been to  omega.com but these are very costly.... If no other alternative.... I have to choose them or close the project.... Second option would be easy for me! :(


texts: Is it ok to have two stepper motors right next to each other?

texts: Would there be any issues having two nema 23 stepper motors laying right next to each other, facing opposite ways (see image)? 48v, 4amps.


texts: Update ESP8266 esp-01 AT command Firmware?

texts: I am trying to install AT command official firmware and so far I am not able to find a reliable way to do that. I have tried using the official flasher tool from Espressif's website but I do not know what hex values should I put in that and what bin files and in which order should I put in that. I have tried so many tutorial and I think all of them are out of date in firmware version.(Also which firmware should I download from the website and my esp8266 module is 8 Mbit module.)


texts: Building a Meter to Measure UVB Radiation

texts: I need to build this instrument for a science experiment related to vitamin D production. I understand that it is necessary to use a photo-diode that responds to UVB wavelengths only and that I need to use an operational amplifier that functions as a transimpedance amplifier with a very high input impedance. Since the photo-diode will generate a current in the range of 1 nano ampere to 1 micro amperes, several precaution will need to be taken to build a properly functioning circuit. Can someone identify the precautions that I will need to take in designing and building this circuit? Since UVB photo diodes are quite rare, I also need some help in selecting a component that will be reliable and available.


texts: What connections (e.g. between gate, drain, source, body, and surrounding circuit) are implied by this MOSFET symbol with a line through it (M3)? For comparison, here is another NMOS transistor from the same paper without a line through it (M4).


texts:
Electronics student here, so i'm printing a IR receiver for a project of my school.
I'm trying to understand the filtering part of the circuit.

The signal is received through the BP104 photodiode and then passes in a filtering/amplifying part of the circuit to be decoded then by a LMC567 tone decoder. Here's the schematic:

So far this is what I know :

Q1, Q2, Q3 and Q5 are Darlington pairs, to amplify the signal.

My questions are :

C2 and C3 would be low pass filters ?

What is the purpose of R11/C7, R7/C5 and C11/R14 ?

Any help would be appreciated.

Thanks.


texts: Can a 12V (automotive) relay carry more than 12v?

texts:
Everywhere I dig around the web (in forums etc.) I see people not recommending more than 12v to go on an automotive relay.
Let's look at this one for example:

I understand they have been designed for 12v systems but the vast majority, if not all, have rated amps on them.
AFAIK conductor cross section requirements have no relation to voltage so if it can carry 40A at 12v it should be able to carry 40A at 50v or any arbitrary, reasonably high, voltage. That is until we get to the point where the voltage gets so high that arcs could jump through gaps between the inside components of the relay but that would be way out of the league of anyone like me.
I'm suspecting the posts I found which discourage going above 12v are regarding the energizing voltage, and not the carried voltage.
Is my guess reasonable and would it be possible to use higher voltage on the NO/NC paths of relays such as the one shown above?


texts: What do I need to program an ATmega 168?

texts:
I use AVR Studio for my compilation and c/c++ code (not arduino).So far I have used a Atmega 2560 development board provided by  Nex robotix.

I have ISP programmers of the following sorts...
AVRISP mkII USB Programmer
and NEX AVR USB ISP STK500V2.

Now I need to do some programming on low end microcontrollers like ATmega 168 (28 pins).
I just have the raw chip. Can I program it on breadboard,or must I buy a development board?

After programming the chip can I use it on breadboard with Vcc, GND and the pins I need for my application?


texts: Hi, I have a headphone(trs) and its audio jack got broken and I have other earphones and I am wondering if I can connect the trs wire to trrs jack. please Inform me . Thanks for your help.


texts: Why single-ended pcb trace impedance is fixed to 50ohms

texts: Why is the trace impedance of a single-ended trace on a PCB fixed to 50 ohms or 75 ohms (for video signals)? Why can't it be fixed to any other impedance values?


texts: How dual gyroscopes can be used to remove gyro drift?

texts:
I need to measure yaw/heading/azimuth correctly.

Now, I have done with gyro with very strong filtering and the results are very low yaw drift and even when there is perfect calibration then there is no drift but angle measured is not perfect and if there is to and fro motion then there is a difference in angle from reference point become increases

Now, what will be the effect of using dual gyro even with three gyros? can I have better results by using multigyro. If yes then how and also suggest any research paper, fusion algoritm or math, etc.

Note: My environment is highly influenced by electromagnetic waves. So, there is no option for the magnetometer.

Thanks


texts: AM radio Transmitter with one station DIY - microcontroller

texts: I have to build a project with a AM transmitter and receiver. The idea is that I will speak something which will be transmitted and received to the receiver. The Transmitter and the receiver assembly will be located very close (within couple of feet). My question is that for the receiver circuit, do i still need a tuner even though it is receiving only one signal from the transmitter?


texts: Can I use a voltage controlled resistor to adjust high side switch current?

texts:
A number of high-side switches (e.g. the NCP380) go into constant-current mode when the programmed maximum current is reached. This is typically set with an external resistor according to the required max current. (e.g. page 17 from the NCP380 datasheet). In this case they seam like a perfect replacement for a constant-current source with all the added protections in one package.

My question is can i use a voltage controlled variable resistor in its place to adjust the constant-current limit during operation e.g. from the output of a DAC. Then i could choose the current limit according to the load that is connected.


texts: Clarification on SMPS circuit design details

texts:
The following is the schematic of the SMPS stage of an old (mid 90s) CRT TV set that I often use to show my students how a real SMPS design might look like.

More ore less I've already understood the details of its workings, but a couple of components placed here and there (highlighted in yellow below) defy my full understanding.

Could someone please shed some light (if it is possible without further design notes) on why the designer put those components where they are?

The following is the internal block diagram of the controller chip (an obsolete TEA2261):

Here is what I think so far:

C12 (270 pF): put there for stabilization purposes of the switching transistor T1 against oscillations/ringing at high frequencies.
D4: it's in parallel with R13, which should be part of the snubber for the primary transformer winding together with C13. Could it be a freewheeling diode for when the switch turns off? In this case why is it not in parallel with the primary winding, but in that unusual (to me) position?
D1: it's a Zener across the electrolytic cap C9. I would guess it's there as a protection against over-voltage across the cap, but it's rating is funny: it clamps at 3.3V whereas the cap can withstand 35V. Is it just a huge safety margin or could it have other functions?
L1: really no clue at all, it just bypasses R3 (which is part of the AC-coupled voltage divider used to drive the base of the BJT switch). It lets DC pass, but DC is then blocked by C9. I'm puzzled. Could it be intended to interact with D1 in some way?
C17: No clue. Why would a designer put a small cap (470pF) in parallel with a rectifier diode? My only guess is it somehow bypasses the junction capacitance, but why?

EDIT (n.2 solved!)

Thanks to a comment of G36, n.2 was sorted out!

R13,C13 and D4 together form what is called an RCD snubber network, also known as polarized turn-off snubber network. See, for example, this document (fig.5 at page 4). As in most documents I've seen, the D+R sits on top of the cap, but they are in series, so it doesn't change the overall network behavior.


texts: Identify the manufacturer of these circuit boards?

texts:
At a surplus sale, a friend picked up a large number of old circuit boards, probably 30-40 in all. Here's the box:

All the boards seem to be made by the same manufacturer and probably come from the same device. Notable components include motors, dials, and op-amps (LM741CN).

Close-ups of some of the boards:

and the back side of the motor board:

The most notable and obvious feature of these boards is the logo:

This logo is on the back of every PCB, although I could not identify it with either reverse image search or by searching for the description.

Can anyone identify the manufacturer? Maybe narrow down what era of technology this is (probably 1970-1980 but that's a big range)? Or what this device might have been? It's to satisfy a burning curiosity :)


texts:
What exactly is the base band? I always thought that it is a synonym to intermediate frequency but it appears not to be the case.

For example I have Bluetooth signals in the range of 2.4 to 2.48 GHz. What does it mean to mix it down to the base band?


texts: Adjustable Voltage Regulator behaving weirdly

texts: I'm using a IFX27001TF adjustable voltage regulator from Infineon.  Here is a link to the datasheet and the useful schematic is on page 16.  I would like to get about 5.3V from the output so I've calculated my resistor values to be R1=100, R2=330.  I'm using a 1uF cap on the input and 10uF cap on the output.  Instead of giving me a steady 5.3V output, it outputs whatever the supply voltage is minus 1V.  I've tried it at voltages up to 10V.  I'm using a bench power supply that can output several amps so I don't think that is a problem.  I've tried with 1 led at the output, 3 leds at the output, and 3 leds a 3.3V regulator and a arduino Uno board doing stuff.  The current draw on that last one was about 100mA so I don't think it's an issue of drawing enough current for it to be stable.  Anybody have any idea what is going on or what my next step might be?


texts: What is a normal quiescent current in BJT class AB amplifier

texts:
A BJT class AB audio amplifier has .27 ohm resistors between the push-pull outputs and speaker. There is 55mv and 59mv,  respectively, across each resistor meaning a quiescent current of over 200ma. This is the lowest it can set to with the bias pot. Is this much current normal or even acceptable for class AB using BJTs?  Is there any way to reduce this or at least have both outputs be the same?

Thanks for the feedback.  Not sure what is meant by which class AB design.   I can tell you it has a differential input and a voltage amplifier, couple for driver transistors and two output transistors which are 2N4915.  Rated output is 42W min into 8 ohms.  No bias diodes,  uses Vbe multiplier.

Measurements were done after the amplifier warmed up for several hours connected to a speaker set at low volume. I will retake the measurements again after warming up with higher volume to see if there's any change.

What I really want to know if I should be concerned with the 200ma quiescent current with no signal and no load?


texts:
I am beginning to design a monolithic frequency synthesizer (around 2.4GHz) in which I need the maximum of spectral purity.  I was looking at injection locked frequency dividers (ILFDs) for use as a prescaler as an alternative to flip-flop based prescalers.  Are there disadvantages to using ILFDs in terms of spectral purity?

As a sub-question, there are two main types of ILFDs--LC based and ring oscillator based.  Ring oscillators have a reputation of being jittery as opposed to LC oscillators.  However, within the context of an ILFD, does this jittery-ness come into play?  In other words, WRT spectral purity, would a ring-based ILFD be sub-par?


texts:
I'm new to using MOSFETs and I need to source one for a personal project of mine. I'm using an N-Channel FET to pull down a 12v (5mA) logic/signal line from logic level (3.3v).

I've used an FQP30N06L successfully, but I'm looking to move to an SMD part, specifically the BSS138K from ON Semi.

Looking at the DS, I see that the RDS(ON), and that a Vgs of 2.5v with an Id of 50mA produces about 2ohms of resistance. This leads me to assume that this MOSFET would be suitable for my use case. Am I missing anything?


texts: Deformation of PTH component pins during handling

texts:
The PCBA drawing specifies 4.23 mm standoff for a PTH component.
Now we encounter deformation issue of the pins during handling due to being slightly touched by operator.

Is there any improvement for the component design to avoid this issue?

Your advice is much appreciated!


texts: Help with using monostable one-shot multivibrator?

texts:
Above is the schematic I simulate in LTSpice. The input signal is a 8V pulse train with 100us ON time and 2250us period. The signal is fed as an input to the timer 555(NE555 in LTSPice).

I'm trying to stretch ON time to around 600us. So according to math R1 = 560 ohm and C1 = 1uF for this ON time.

But when I simulate in LTSpice whatever the R C combination is the output is the same: goes on with input's falling edges and goes off with input's rising edges.

Am I doing something wrong here?


texts:
I know that a rectifier converts AC voltage into pulsating DC voltage.

However, when would you use a half wave rectifier as opposed to a full wave rectifier ?

Can you give an example of some appliances that use half wave and full wave rectification.


texts:
I would like to design a slave device that can communicate with POE in a daisychain configuration. I am going to use dual RJ45 port but in terms of connection of the transformer circuitry, I have no idea. Could you help about the daisychain configuration? How can I make the dual port connections to the slave device? Is there a need for additional controller or a switch?
Best.


texts: Calculating energy accumulated in toroidal coil

texts: That's a cross section of said coil. My question, is since there are two different permeabilities, can I split it into two toroidal coils, with unique permeabilities, or should I've done the Ampere's law for the middle, which I see now is at 25mm, μ2. Tangential vectors of the strength of the magnetic fields are the same.


texts: When designing a PCB, is it sensible to use a pin jumper in the pathway of a small current signal (around 0.8 uA) or could there be issues with noise? I would use the jumper to select between different transimpedance amplifiers.


texts: When driving stepper motors do i need to worry about back EMF?

texts: When i've driven coils in the past(such as mechanical relays) i've had to put a diode to protect it against back EMF once turned off. Do i need to do that when driving stepper motors with a ULN2803a?


texts:
I previously created a question about how to create a circuit that supported battery  discharge where the discharge current would be configurable by a microcontroller using PWM:

Control discharge current using Arduino

I have implemented this and it works really well. The discharge current matches the expected values very precisely.

Now I am interested in knowing, if the same principle can be used for charging using a programmable current.  I.e. the MOSFET would be used to sink the desired current over the battery and would also be regulated using an op-amp. Previously my charger has been using a LM317 regulator in constant-current mode, but the MOSFET+opamp solution would be much better due to allowing dynamic control of the charge current. Also now I already have a dual opamp IC on the circuit board I could use the other opamp in the IC to control a secondary MOSFET used for charging.

Is there any downsides to this approach over using, say, a LM317 regulator in constant-current mode? Is there more noise in the current delivered etc.?


texts:
I need a circuit that would allow me to optionally add pull-up resistors to an I²C bus. One way would be to add two jumpers for each pull up resistor. But I thought of something like this:

This way only one jumper is used and SDA does not interfere with SCL when J1 is not mounted. IMO this should work, but maybe I am not seeing something.


texts: Atmega328p - Program works with 2.7V power supply but doesnt with 3.3V

texts:
I already posted this question on avrfreaks but so far I'm not getting many responses so decided to ask here as well.

  So I'll start by telling little bit how this project looks together
  for the basic idea. We have Microchip RN4020 Bluetooth module(3.3V
  device), Cypress CY15B102Q FRAM(3.3V device) and two Atmega328p.

  The idea is to light up neopixel WS2812B(5V device) leds depending
  what data comes in from Bluetooth module. It can be both just a single
  color or different animated movements. So we save data about animated
  movements in FRAM. Problem with one Atmega328 was that it couldn't
  manage in time to both receive UART data about new animation and save
  it to FRAM and light up LEDS frame by frame without missing some data
  from UART(because had to tun off interrupts at the time of lighting up
  LEDS).

  These devices get power from LM1117 Regulator that's supposed to give
  3.3V output when given in 5V.

  So now one Atmega328p is responsible for getting UART data from RN4020
  and saving them to FRAM and the another one takes data through SPI
  from FRAM and lights up leds. Problem is of course sharing the same
  FRAM by these two Atmega328p so I decided to dedicate 2 pins that
  would indicate whether or not FRAM is in use by any of these two
  Atmegas.(if in use PIN is high, if not low). The other Atmega looks at
  this and waits when SPI is not used by another Atmega and only at this
  point turn on SPI and start using FRAM. When SPI is not used those
  pins are set as inputs so they wouldn't screw the signal.

Here are the functions that are responsible for turning SPI on/off

void turn_SPI_on()
{
    if(!spi_is_enabled){
        DATA_PORT |= (1 << FRAM_USED_BY_MCU2);
        PRR &= ~(1 << PRSPI);

        /* Set MOSI and SCK, MOSI and SS output, all others input */
        SPI_DDR = (1<<SS) | (1<<MOSI) | (1<<SCK);
        SPI_PORT = (1 << SS); //slave select high

        /* Enable SPI, Master, set clock rate fck/4 */
        SPCR = (1<<SPE)|(1<<MSTR);
        SPSR = (1 << SPI2X); //double SPI speed

        spi_is_enabled = 1;
    }
}

void turn_SPI_off()
{
    if(spi_is_enabled){
        SPCR = 0;
        SPSR = 0;

        //set everything to input
        SPI_DDR = 0;
        SPI_PORT = 0;

        spi_is_enabled = 0;

        DATA_PORT &= ~(1 << FRAM_USED_BY_MCU2);
    }
}

So the interesting thing is that when LM1117 gets input voltage of 3.3V from UART USB module it gives output of 2.7V as datasheet suggests and its still fine because everything still works with this voltage. (Both Atmegas can share the same FRAM though SPI without any problems at all). Now the fun fact happens when LM1117 received 5V in its input and gives 3.3V ouput which should work the same way. Now the second Atmega which is supposed to light up leds reads the values from FRAM all wrong while the Atmega responsible about receiving data from UART still can access FRAM without any problems. If I unplug the SPI CLOCK(SCK) wire from 1st Atmega(the one responsible for UART) 2nd Atmega starts accessing correctly.

Can you guys give me any ideas why this might happen? Remember that this is the same program and works with 2.7V power supply but doesnt with 3.3V.

LM1117 regulator circuit

EDIT : One more potentially important thing - If power supply V_in = 3.3V (V_out = 2.7V), its taken from UART USB module, if power supply V_in = 5V (V_out = 3.3V), its taken from LRS-50-5 power supply


texts:
I'm trying to create a DC voltage attenuator which linearly scales the loss relative to an applied control voltage "Vc". In other words, K = Vout/Vin is a linear function of Vc. Vin is guaranteed to be in the range -2.75 to 2.75 V.

Ideally, the gain K ranges from 0.005 to 1.0. Such is to say, if Vc ranges from 0 to Vcmax, the goal is to come close to realizing the following transfer function: K = Vout/Vin = 0.005 + Vc*(.995 / Vcmax)

Does anyone know of a circuit or IC which will come close to realizing this functionality? No supply/cost constraints. I've heard that JFETs can be used as fairly linear voltage-controlled resistances: http://graffiti.virgin.net/ljmayes.mal/comp/vcr.htm

Edit: Another option could be to pre-scale the input and then implement a voltage-controlled amplifier


texts: Latching circuit latches before pushing the latch button

texts:
I am a beginner and I am trying to build a latching circuit.

In the diagram below, the LED is on while I expect it to be off.

The push button should switch the PNP 2N3906 on, which in turn switches NPN 2N2222A on, keeping the PNP transistor switched on when the button is released.

Did I calculate the base resistors wrong?

From the data sheet for 2n3906

(5.2V-0.95V)/0.005 = 850ohm

I put 1k since I don't have a 850ohm resistor

From the data sheet for 2n2222a

(4.2V - 1.2V)/0.015 = 203ohm

I believe the calculations are correct. Why is the circuit closed?


texts: Unbalanced voltage on 3-phase wind turbine system

texts:
I work on wind turbines, I am a troubleshooter.
I have a problem on the turbine which I cannot solve so far
I would like to ask the help of this community.

When turbine starts to generate, an unbalance appears on the 690V 3-phase system. This appears only when the turbine is producing. The phases are balanced when the turbine runs from the grid.

As the generator production increases, the difference on phase 1 gets bigger. The maximum I've measured on phase 1 was 422V to ground. The other two phases are stable 397V.

In the line of the production there is the generator, converter AC/DC and DC/AC, main reactor, filter cabinet and the 690V circuit breaker.

My question is, what could cause this unbalance?
If you need more info about the system, just let me know.


texts: 555 Charge Controller Schematic Explanation

texts:
To preface, I am a relative beginner electronics hobbyist, and I have no experience reading schematics.

I have been working on a home wind turbine, and I would like to use Michael Davis's charge controller, but I am confused about the diagram.

Are all the "negative" wires for the three inputs to be connected together as the single common ground? Also, would the ground connection near IC1 simply denote another wire to said common ground? Last, if this is all the case, why would the relay inductor receive any current if the circuit has already been completed?

I'm sorry if the answers are terribly obvious. Any help would be appreciated.


texts:
Looks like I killed a mosfet today, its an irf3205
http://www.irf.com/product-info/datasheets/data/irf3205.pdf

The dc motor always goes on as soon as +12v and GND for the motor are connected, no matter if the gate is connected or not.

This mosfet wasn't my first choice but the shop I was visiting was out of stock on the TTL mosfet I originally wanted. A quick google turned up the irf3205...but I missed that VGSon = 10v.

I was driving it via a bc547 from a avr a short test with a 35ma 5v motor worked even without the bc547 so I connected it directly.... there's a shottky diode in parrallel to the dc motor to kill spikes after shutdown.

A windshield washer pump is turned on by the mosfet, connected like in this circuit (the part to the right of r2):

The pump should take about 2a(found different sources for that) when running and of course a lot more when it starts.

I'm missing a RDSon graphic in the datasheet for different VGS voltages - shouldnt there be one?

The on time for the pump was at most for 30s...the avr code still got some hickups. Could this be enough with the not so good VGSon value to kill the mosfet?


texts: Use an active PS/2 -> USB adapter as USB-Serial Bridge

texts:
I'm working on a small robotics project where I need to enable my old phone (Nokia 5230, shows up as USB Serial port on Windows but USB cable is straight-through) to talk to an Arduino UNO R3 (doesn't support USB Host mode natively).

My idea is wiring together the USB cable for the phone and the USB end of the adapter and wire the DATA/CLOCK port out of the PS/2 socket to the Arduino and communicate over USB serially.

Essentially, the phone will act same as a PS/2 keyboard connected does to the Arduino.

Sorry if my answer is lacking on original research, I am just inquiring if it's feasible (and some general advice) so I can start reading more on it in depth.

ps: With active I mean, Windows shows the adapter as composite USB device (with nothing connected at the PS/2 ports) and there is a circuit inside with some capacitors and a big epoxy blob on it.


texts:
I’m looking for an off the shelf device to send a serial stream of data (low speed ok) wirelessly to a PC.  I’m guessing the easiest way is through a comm port or USB port.  Distance is less than 25 ft.
I also need to write code to catch the data.  Can anyone suggest some inexpensive off the shelf hardware? Low cost is important in this project.


texts:
Is voltage divider is a good option for supply voltage to an IC ?

I am working with a 555 timer, MAX232 ,an Inverter SN74LVC and with a 12V relay.

I heard that voltage devider is not a best way to step down 12v to 5V  for supply voltage.


texts: HM-TRP radio module works at 56K data speed but only in delayed chunks

texts:
I created the following setup:

I created one circuit in which the PC connects to an HM-TRP radio module via a max232 DIP IC. This circuit for the test is the master to all devices and sends a 16 byte packet to each slave in turn.

The second circuit is a whole system on a microcontroller with an HM-TRP radio module. This circuit is meant to be a slave. This slave sends a result packet which is 16 bytes twice in a row the moment a valid packet is received from the master.

When the master sends any kind of data continuously at 56K speed, the slave receives all of it.

If the master attempts to send 16 bytes of data at 56K speed that the slave expects to receive and the master waits 20ms after sending the last bit of data, then it is able to receive the correct result data the slave has sent back.

Now if I change the waiting time from 20ms to 15ms, then no data is returned from the slave. I know this by observing the lights on the radio modules themselves.

So this suggests to me it's not the computer nor the microcontroller that's the problem, but the timing.

If my math is correct, then I believe the timing should be as follows:

Master sends out 16-byte packet.
Master receives a 16-byte result from correct slave.
Master receives same result again.

So 1/57600 times 10 bits a byte times 48 = 8.3ms

Which means it should take 8.3ms plus maybe a few hundred microseconds to process the entire communication between the master and any one slave.

So why do I need to make the waiting time to 20mS instead of 8ms? I mean I heard somewhere about some "ramp-up" time when receiver switches to transmit mode or vice-versa? but I don't know. and the documentation for the module doesn't explain anything about delays.


texts: Noise and ripple values in a bench power supply

texts:
I was trying to analyse the Vpp and Vrms of a bench power supply. Now, I understand that Vrms = Vpp * 0.707.

Now, the bench power under study is the GPD-4303S.

The Vrms and Vpp is given as shown below -

Now, Vpp = 10mV. So the positive is 5mV.
Henceforth Vrms = 0.707*5mV = 3.53mV.
How come they have 1mV as Vrms ?

Kindly clarify this please.


texts: Problems with a two-diode 3.3V -> 5V level shifting circuit

texts:
I'm trying to drive a strip of 57 APA102 LEDs from an ESP8266.

Driving just one LED directly (without level shifting) with a very short (about 10 cm) bus seemed to work, even though the APA102 expects 5V logic.

Now I built what I actually need:

the ESP is about 1m away from the strip
added diode level shifters for clock and data as per this answer: https://electronics.stackexchange.com/a/82112/18496
the circuit is wired correctly, I checked all connections twice.
ESP and strip are supplied by a 5V, 7A power supply, with 5V and GND connected on both sides of the strip.

The strip shows wrong colors, though. I think this is caused by the level shifting circuit, which simply can't drive the long signal lines with proper waveforms.

I lowered SPI frequency to about 500 kHz (bit-banged SPI with 1 microsecond delay between clock transitions), but the result remains the same.

It's hard for me to get many of ICs suggested for this kind of level shifting, such as the 74AHCT125
. However, I can get the 74HCT125. It can run off 5V and minimum high level input voltage is 2V. Would that be a suitable chip for this purpose?

Any other things I should try or test?

Voltage levels:

The APA102 has a maximum low level input voltage of 0.3 VDD = 1.5V and a minimum high level input voltage of 0.7 VDD = 3.5V.
The ESP outputs max 0.1 VIO = 0.33V or min 0.8 VIO = 2.64V. It seems to be able to drive 12mA.


texts:
I am using the IEEE 14 bus test system for a simulation and was wondering why some of the resistances of lines are set to zero, e.g. see lines (4,7), (4,9), (5,6) below (only part of the full data is shown below).

From  To   R           X           B
Bus   Bus  pu          pu          pu
2     5    0.05695     0.17388     0.0346
3     4    0.06701     0.17103     0.0128
4     5    0.01335     0.04211     0.0
4     7    0.0         0.20912     0.0
4     9    0.0         0.55618     0.0
5     6    0.0         0.25202     0.0
6    11    0.09498     0.19890     0.0

I thought all lines have some resistance; is a zero resistance line just an approximation for a very small resistance?


texts: Derivation of the Bandwidth formula for noninverting opamp

texts:
I want to find why the bandwidth formula in a close loop noninverting opamp is:
$$f=f_{unity} *B$$
I tried to prove the equation above by using the formula for close loop gain and the midband equation, the steps are:

Find the open loop gain \$A_{OL} \$ when the close loop gain is \$\frac{1} {\sqrt2} \$ of its max close loop gain:
$$\frac{A_{CL}} {\sqrt2}=\frac{1}{\sqrt2*B}=\frac{A_{OL}}{1+A_{OL}B}$$
$$\frac{1}{\sqrt2*B}=\frac{A_{OL}}{1+A_{OL}B}$$
$$A_{OL} =\frac{1}{B(\sqrt2-1)}$$

Next, find the frequency "f" in which the max open loop gain \$A_{max} \$ will be equal to the value of the open loop gain equation above(using midband equation) :
$$A_{OL} =\frac{1}{B(\sqrt2-1)}=\frac{A_{max}} {\sqrt{1+(f/f_2)^2}}$$
(simplifying.....)
$$f=f_2*\sqrt{(A_{max}*B*(\sqrt2-1))^2-1}$$

Next,I add \$A_{max} \$ to both numerator and denominator so that I will have an \$f_{unity} \$ at my equation, I will also move \$A_{max} \$ inside the squareroot:
$$f=A_{max} *f_2*\frac{\sqrt{(A_{max}*B*(\sqrt2-1))^2-1}} {A_{max}} $$
$$f=f_{unity}*\sqrt{(\frac{A_{max}*B*(\sqrt2-1)} {A_{max}})^2-\frac{1}{A_{max}^2}}$$

Since \$A_{max} \$ is super large, I can cancel some values and the result will be:
$$f=f_{unity} *B(\sqrt2-1)$$
Why do I have an excess \$sqrt2-1\$ in my formula? Where did I go wrong?


texts:
I'm using this S23K142 Microcontroller - 64 pins.
I just want to know (in general as well as with respect to this microcontroller) how many states does this Microcontroller have?
By states I mean, Reset State, Default State, Normal State, During Reset State, After Reset state and Sleep state?
My questions:

I'm asking because I need to configure my Microcontroller (SPI, IC Communication, ADC & GPIO peripherals) pins , right? So, each of those pins would need to be configured differently during Reset, Sleep and default state right. So, how many states are there in the Microcontroller and where to view this information?

In general, Does Before Reset, After Reset and Reset - denote the same state? And does Default and normal pin configuration also mean the same? - Just trying to fix my terminology here.

Request you to help with the above 2 questions.


texts: How to split a floating point number into individual digits?

texts:
I am helping a friend with a small electronics project using a PIC microcontroller 16F877 (A) which I am programming with mikroC.

I have run into a problem which is that I have a floating point number in a variable lets say for example 1234.123456 and need to split it out into variables holding each individual number so I get Char1 = 1, Char2=2 etc etc. for display on LCD. The number will always be rounded to 3 or 4 decimal places so there should be a need to track the location of the decimal point.

Any advice on how to get this split would be greatly appreciated.


texts: PIC12F629 variables overflowing with nested loops

texts:
I'm trying to do a simple binary counter using a PIC12F629 (Code below), driving LED's direct from GPIO pins 0,1,2.

I'm sure it should be a very simple counter, but as written it just won't count past 7 - the 8th time through the delay function, it just resets.

If I set the delayMax counter to a much lower number (512, for example), it works as expected, counting up to 15 (0x000F).

It also works if I set my innerCtr loop counter to a small number (like 3).

My instinct is that a counter or variable is running out of bits, or memory is filling up, but I'm new to PICs so I just can't figure where to look

All the break points and variable watching I can think of in the simulator shows nothing actually wrong - all the values of all the variables look correct, but it just doesn't work.

It behaves exactly the same on the hardware, so I know it's not a simulator bug.

I'm using MPLab X IDE on OSX, using the XC8 compiler.

I'm sure I'm missing something really simple.

Can anyone see what I've done wrong?

/*
 * File:   pic12BinaryCounter.c
 * Author: BungledB
 *
 * Created on March 18, 2018, 17:34
 *
 * Chip: 12F629I/O
 */

#include <stdio.h>
#include <stdlib.h>

// CONFIG
#pragma config FOSC = INTRCIO   // Oscillator Selection bits (INTOSC oscillator: I/O function on GP4/OSC2/CLKOUT pin, I/O function on GP5/OSC1/CLKIN)
#pragma config WDTE = ON        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-Up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = ON       // GP3/MCLR pin function select (GP3/MCLR pin function is MCLR)
#pragma config BOREN = ON       // Brown-out Detect Enable bit (BOD enabled)
#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)

#include <xc.h>

//  Prototypes
void delay(void);
void init_ports(void);

// Globals
unsigned int delayMax = 2048;

int main(void) {

    unsigned int clockCtr;

    //Set the ports up
    init_ports();

    while (1)
    {
        for (clockCtr = 0; clockCtr < 16; clockCtr++)
        {
            GPIO = clockCtr;
            delay ();
        }
    }
}

void delay(void)
{
    unsigned int outerCtr,innerCtr;

    for (outerCtr = 0; outerCtr < delayMax; outerCtr++)
    {
        for (innerCtr = 0; innerCtr < 8; innerCtr++);
    }

}

void init_ports(void)
{
    // Set all GPIOs to Outputs - although for this chip, 3 is always an input or mclr.
    TRISIO = 0;
}


texts: Error in Reading Internal temperature sensor in stm32f042

texts:
The program to read the Internal temperature and V_battery voltage using ADC in STM#2F042 is as follows:
#include "main.h"

#define I2C_ADDR                            (0x40<<1);

#define V_Ref                                   3.3

#define RESOLUTION                      255

#define TEMP30_CAL_ADDR             ((uint16_t*)((uint32_t*)0x1FFFF7B8))

#define TEMP110_CAL_ADDR            ((uint16_t*)((uint32_t*)0x1FFFF7C2))

ADC_HandleTypeDef hadc;

float internal_temp;

uint8_t index1=0;

uint32_t adc_value[2];

float V_bat;

void SystemClock_Config(void);

static void MX_GPIO_Init(void);

static void MX_ADC_Init(void);

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)

{

    if(__HAL_ADC_GET_FLAG(hadc,ADC_FLAG_EOC))

        {

             adc_value[index1]=HAL_ADC_GetValue(hadc);

             index1++;

        }

    if(__HAL_ADC_GET_FLAG(hadc,ADC_FLAG_EOS))

        {

        internal_temp = adc_value[0];

        internal_temp -= (int32_t) *TEMP30_CAL_ADDR;

        internal_temp *= (int32_t)(110-30);

        internal_temp /= (int32_t)(*TEMP110_CAL_ADDR - *TEMP30_CAL_ADDR);

        internal_temp += 30;

        V_bat=(float)adc_value[1]*V_Ref/RESOLUTION;

            index1=0;

        }
}

int main(void)
{
 HAL_Init();

SystemClock_Config();

  MX_GPIO_Init();

  MX_ADC_Init();

  MX_TIM2_Init();

HAL_ADC_Start_IT(&hadc);

  while (1)
  {

 }
}
static void MX_ADC_Init(void)

{

  ADC_ChannelConfTypeDef sConfig = {0};

  hadc.Instance = ADC1;

  hadc.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;

  hadc.Init.Resolution = ADC_RESOLUTION_8B;

  hadc.Init.DataAlign = ADC_DATAALIGN_RIGHT;

  hadc.Init.ScanConvMode = ADC_SCAN_DIRECTION_FORWARD;

  hadc.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc.Init.LowPowerAutoWait = DISABLE;

  hadc.Init.LowPowerAutoPowerOff = DISABLE;

  hadc.Init.ContinuousConvMode = ENABLE;

  hadc.Init.DiscontinuousConvMode = DISABLE;

  hadc.Init.ExternalTrigConv = ADC_SOFTWARE_START;

  hadc.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

  hadc.Init.DMAContinuousRequests = DISABLE;

  hadc.Init.Overrun = ADC_OVR_DATA_PRESERVED;

  if (HAL_ADC_Init(&hadc) != HAL_OK)

  {
    Error_Handler();

  }

  /** Configure for the selected ADC regular channel to be converted.
  */

  sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;

  sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;

  sConfig.SamplingTime =ADC_SAMPLETIME_1CYCLE_5 ;

  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)

  {

    Error_Handler();

  }

  /** Configure for the selected ADC regular channel to be converted.
  */

  sConfig.Channel = ADC_CHANNEL_VBAT;

  if (HAL_ADC_ConfigChannel(&hadc, &sConfig) != HAL_OK)

  {

    Error_Handler();

  }

}

This is the code I have written (generated from Cubemx.) It will not get the proper value for internal temperature and V_bat (battery voltage).
Can someone please tell me the error/problem in the code, especially in the callback function?


texts: BJT conceptual issue or is my circuit bad?

texts:
Working on a lab that is the IV characteristics of BJTs. I constructed the circuit as depicted in the lab, I think. The lab wants me to measure the V(collector-emitter) and I(collector) for values of V(Collector) from 0-10v. Do this for values of I(base) of 0,50uA,100uA,150uA,200uA. Now I did this simulation in Pspice before doing the real circuit, and received the following.

a plot of Ic as a function of Vce, where each curve represents increasing values of Ib. This graph makes sense. My issue is when I construct the circuit and measure the values, despite changing Ib, there is no change in Ic. The graph of Ic Vs Vce should shift upwards as depicted by my Pspice simulation.

Now, to get the values of Ib, I set the base voltage (Vb) to 1 volt and said that due to this relationship

Ib = Vb - Vbe / Rb that if I keep Vb constant and know what Ib I want then all I have to do is change Rb. So for an Ib of 50uA I calculated an Rb of 6000, for Ib of 100uA, Rb = 3000 and so on.

The issue is that if I have Vb = 1, and Vc = 1 when changing Rb from 6000 to 3000, there is no change seen in Ic.

I really dont know what I am doing wrong. Ive been sitting in the lab for a while. It is springbreak, no one is here. I don't know if I am building the circuit wrong or I have a bad conceptual understanding.

My exact readings are

with a 6k resistor and with a 3k resistor for Rb

PSU(Vcc) - 1v and 0.010A CV

Vce - 1.00655Vdc

Ic - 0.0965uAdc

PSU(Vb) - 01.00V and 0.0A CV

Using a 2N3904 NPN transistor

The lab circuit

NOTE: Ignore the 27k ohm resistor in this picture. This lab is for people with Elvis boards, we don't use them. We also don't have a power supply that can supply microamps.

My circuit

(sorry the picture is huge from my phone)

http://imgur.com/a/r87Dw


texts: Need help to increase schmitt trigger sensivity in a circuit

texts:
I need help on a circuit I've designed to detect hits on a piezo sensor on a drum. It uses an opamp with 2 channel, on goes to a schmitt trigger, the other to the ADC input on the XMEGA microcontroller. Once the interrupt for the schmitt trigger is raised, the reading is done on the ADC and then a reset pin activate a transitor that flushes the excess signal.

All of it works super fine as expected but there one little catch: I'd like to increase the sensivity of the schmitt trigger by a fixed value. The opamp I'm using to feed the schmitt trigger gets maxed out when I apply the maximum gain on it. On the side of the ADC channel, all is good, the signal is within good range (about 0V-4V).

Now here is the question: is there a way I can use this exact(ish) circuit and maybe add a resistor or 2 somewhere or remove one to bias the input of the schmitt trigger of let's say +1-2V? Since the threshold of this particular schmitt trigger seems to be about 2.2v when Vcc is at 5v but I want to detect signal to about 1-1.5v as well.

My background is software/firmware development so I'm a bit lost on what to do to solve this problem without having to redo the whole things (which works fine but isn't sensitive quite enough to my taste)

Schmitt trigger used is: SN74LVC1G17
Opamp used is: ADA4075

Here is what the board looks like (it if may be of any help), so there is room to solder jumpers or resistors around without having to older a new set of board:


texts:
Have a design that is taking an input from .549V-.838V out of a DAC and am trying to get it to amplify it into a range that would be more useful in an ADC, like 0-5V.  So far I came up with this design:

This gets me from .549-.838V to 1.921-2.933V, which is way better.  I feel like I should be able to shift the output left so that the .549V translates closer to 0V or 1V, and I could amplify to 4+V for the high end.  Thanks for any help or insight.

EDIT for new problem
So I am trying to apply this to a similar problem now with what you showed me to do.  I have a thermistor as part of a voltage divider, and the output is currently going into an ADC.  I am trying to use an Op-Amp to increase my resolution.
My current range would be 2.22V-2.73V, so a spread of .51V.  I am trying to spread this out over 0-5V, and specifically I am trying to do this with my op-amp limited on the rails with 0-5V, because my current design(not shown) would overload my ADC with like 10V if I unplugged the thermistor.
So, I did 5V/.51=9.9.  8.9 for a non-inverting setup, and i used this for my gain resistor, R102, then I used a 1k resistor for R101.

I am modeling this graph to show the voltage as the Thermistor changes in values.  2.222 is at 8k, and 2.73k is at 12k.

Thanks again for all the help.  Learning a lot here.


texts: How to understand the parameters of a transistor

texts:
I am trying to design a circuit using a transistor but I don't understand the parameters of the transistor written in the program.
Does anyone know what is the meaning of the following symbols?

I_s,B_R,R_B,R_E,T_R, M_JE, C_JC0, V_JC, B_F, V_A, R_C, T_F, C_JE0, V_JE, M_JC

I do understand the logic of a PNP and NPN transistor. I don't understand the names of the parameters here.

Thanks!

here is the figure from the editor:


texts: Finding Differential Equation in RC Circuit with op-amp

texts:
I am trying to find the D.E. that relates Vin to Vout.

KCL at A: $$\frac{A-V_o}{12} + \frac{A-V_i}{6} + \frac{1}{12}*\frac{dV}{dt} = 0\tag1$$

KCL at B: $$\frac{B-0}{10} + \frac{B-V_o}{10} = 0\tag2$$

\$2B=V_o\$ or \$B = .5V_o\$

By using op-amp rules V+=V-(A=B) I found the following equation.

$$\frac{3}{2}V_o = \frac{dV_i}{dt} - 2V_i\tag3$$

I don't really know if this is 100% correct and would like to see what someone else comes up with.


texts: What is the purpose of those star like solder joints?

texts:
I recently watched a Xbox Series X PSU repair video on YouTube and was surprised by the fact some solder joints have a star-like shape :

Is there any specific reason to do this ? This is the first time I see this.
My guess is those joins are stronger than typical round shaped joins (which might break and create false contact after a very long time) but maybe it's something else.


texts: STM32 : reset the I2S DMA address pointer

texts:
For my application I have a DAC communicating with an STM32F4 through I2S. On the microcontroller's side, informations are send to the DAC through a DMA stream, with a circular buffer.
On an external interrupt, I would like to pause the DMA, change some sound parameters and then resume the DMA stream.

My interrupt routine is basically like that :

void HAL_GPIO_EXTI_Callback(uint16_t pin)
{
    if(pin == GPIO_PIN_13)
    {
        HAL_I2S_DMAPause(&hi2s2);
        changeSound(&sound);
        HAL_I2S_DMAResume(&hi2s2);
    }
}

And I have 2 interrupt routines triggered on DMA TxHalf/TxCplt that fill each half of my DMA buffer with the sound. (EDIT : during my research I also learned that there is a "double buffer mode" that allows to do that with some advantages, but that's off topic.)

What I want to avoid is to transfer some remaining samples of the old sound after my Exti interrupt. So my idea was to fill the whole buffer after changing the sound, and then reset the memory pointer of the DMA stream to the beginning of my buffer.

It would look something like that :

void HAL_GPIO_EXTI_Callback(uint16_t pin)
{
    if(pin == GPIO_PIN_13)
    {
        HAL_I2S_DMAPause(&hi2s2);
        changeSound(&sound);
        fillBuffer( address_of_1st_half, &sound);
        fillBuffer( address_of_2nd_half, &sound);
        *reset_DMA(&hi2s2)*; <==== this is the function I'm looking for
        HAL_I2S_DMAResume(&hi2s2);
    }
}

nb : as you can see I'm using CubeMX's HAL drivers

I have looked into the HAL datasheet for such a function but I haven't found any.

The only thing that is close to that is using DMAStop() and then Transmit_DMA() again. But I'm afraid that would take too much time...

If anybody has an idea I'd be glad to hear it!

Thanks


texts: Why can't I get a output lower than 0V in this diode and capacitor circuit?

texts:
In the image above green is my input (node left side capacitor) and blue is my output (node right side of the capacitor).
I would expect that the blue signal would follow the input, but it does not do this. Why is this the case? Can you explain this with open circuit and short circuit equivalents for the diode?


texts: Multiple isolated DC-DC converters in series - ground reference question

texts:
I have a question concerning multiple isolated DC-DC converters in series and ground references.
I need to measure 48 volts from the input of the first DC-DC converter via a voltage divider, and also 24 volts on the output. However my MCU is powered by an LDO (from 12 volts) which uses GND2 as reference, which is totally isolated from GND1 and GND.
Which ground reference is needed on the both voltage dividers?


texts: 100MHz noise filter doesn't attenuate much

texts:
I have a switching regulator that puts 100MHz noise onto the power supply that it shares with a microcontroller, and I'm trying to filter this noise to give the microcontroller a clean DC power source.

Unfortunately my 3 filtering attempts don't attenutate the noise very much:

Inductor circuit

Part: B82144F2332K000
Value: 3.3uH
Resonant frequency: 100MHz
Link: https://www.mouser.com/productdetail/871-b82144f2332k000
Expected NoiseOut/NoiseIn:

(Based on datasheet, Zinductor = 2000ohms @ 100MHz)

Rload/Zinductor == 100/2000 == 0.05
Measured NoiseOut/NoiseIn:

248mV/670mV == 0.37

Feedthrough capacitor circuit

Part: YFF31HC2A104MT00
Value: 100nF
Resonant frequency: 105MHz
Link: https://www.mouser.com/productdetail/810-yff31hc2a104mthn
Expected NoiseOut/NoiseIn:

(Based on datasheet, InsertionLoss @ 100MHz == -70dB)

-70dB == 20Log10[NoiseOut/NoiseIn]

NoiseOut/NoiseIn == 0.00032
Measured NoiseOut/NoiseIn:

400mV/800mV == 0.5

Ferrite bead circuit

Part: FBMH4532HM202-T
Resonant frequency: 100MHz
Link: https://www.mouser.com/productdetail/963-fbmh4532hm202-t
Expected NoiseOut/NoiseIn:

(Based on datasheet, Zferrite = 2000ohms @ 100MHz.)

Rload/Zferrite == 100/2000 == 0.05
Measured NoiseOut/NoiseIn:

201mV/530mV == 0.38

Here's a picture of the ferrite bead circuit and a scope shot (NoiseIn=yellow, NoiseOut=green), for example:

Why don't these circuits attentuate the noise closer to the expected amount?

Thanks!


texts: When does raspberry Pi pin reset its state

texts:
Using Arduino, I'm trying to detect whether Raspberry Pi has successfully turned itself off. I first tried to check on the pins that are used for serial communication between said devices but the pin state is obfuscated by voltage level shifter that protects Rasperry Pi from (eventually accidental) 5V voltage.

So my plan is to set any other Raspberry pin HIGH and hope it will go low as soon as the Arduino shuts itself down.

But I have doubts whether the pin will not lose its state sooner (as soon as my controller application exits, or during the shutdown phase).

So is pin approach a good one if I want to check if the Rasperry Pi is off?


texts:
I am using Artix 7 FPGA (XC7A200T-2FPG676) BGA package on PCB, after unstuffing of FPGA I want to short two pad P18 and R18 on PCB with each other and then wants to stuff back my FPGA .
Note: P18 and R18 are adjacently placed.
It is possible will it work?
If someone does this successfully could share picture?
Your suggestion regarding this will be highly appreciated Thanks


texts: RFID reader array using row/column RF switches (multiplexers)

texts:
I need an 8x8 grid of RFID readers arranged on an 8"x8" board. The RFID tags will be placed only millimeters above each antenna.
I was wondering if I could use one 1:8 RF switch (e.g. pSemi PE426482) to connect one antenna connector from the reader to a selected column, and a second 1:8 RF switch to connect the other antenna connector from the reader to a selected row, and be able to read from the antenna on that row/column only. To clarify, each antenna in the array has one lead connected to a row line, and the other lead connected to a column line.

[Update]
Perhaps I should go with 125khz tags and cheap analog switches instead of 13.5 MHz tags and expensive RF switches...


texts: Relation between torque and speed in a dc motor(say dc shunt motor)

texts:
I have a doubt on relation between torque and speed in a DC motor. Please correct me wherever I am wrong.
As we know that if we increase load the armature speed will decrease so that back emf also decrease or say armature current will increase and we know that torque depends on armature current Ia ( in a dc shunt motor so the flux could be constant)
       Torque proportional to flux × Ia
          Sience Flux =constant
    =Torque proportional to Ia
So when armature current will increase torque will increase and thus speed should also increase.
  So my question is that if rotor slows down because armature is not producing enough torque for increased load then why  does it not regain the same speed (on which it was rotating) after the armature produces sufficient torque (due to increase in current)


texts:
I'm looking for a little bit of help on a project I'm working on.

I need to find some way to make led light bars (18w and 120w) to automatically start out dim and gradually brighten to full brightness over a few seconds when they get power and turn on.

They are activated by a infrared motion activated switch and ran off of a car battery. It's for night hunting lights and I need the function to keep from spooking animals when the green lights suddenly turn on. I've shot one wild hog with it, but I want to make it even better.

I need it to be waterproof simple and something I can integrate easily into my current build. Any ideas?


texts:
I made a circuit with 16 transistors which switch 16 LEDs, input signal is from raspberry (or any board) digitally.
But is was difficult to solder and I tried to keep it as small as possible.
In the end there are still a few switches who do not work.
So I put that aside and tried with smaller amounts, ie. four
But meanwhile it came to my mind, maybe there are ICs who can do that job much easier??


texts: Reducing resonance in a piezoelectric ultrasonic transducer

texts: I am using a piezo transducer to launch an ultrasonic pulse in air, at a frequency of 125kHz. A picture of the received waveform is attached. My question concerns how I can (electronically) limit the long resonance tail in the emitter pulse which I assume is because of the relatively high Q of the device.


texts:
I have to confess that I'm not a handy person thus soldering is too difficult for me. I was researching on the internet about soldering alternatives but all of them are done for soldering 2 cables.
I need an alternative for soldering a cable with a relay (those with 3mm or 4mm pins).


texts:
I am studying patch antennas for mobile communication (technology.)

I have found some examples of them but without explanation.

Maybe can someone explain to me the difference of examples from this picture?

my thoughts:

c) Is a patch which is connected with a waveguide (or linear antenna.)

f)  With a folded slot

But I am not sure, that' s why I need your help.


texts: Why do refrigeration compressors stall when switched off and on quickly; or, why do I need to wait three minutes before restarting my air conditioner?

texts:
All of the air conditioners I've worked with have the following words on them:

  Before restarting, wait three minutes.

In the event the air conditioner's compressor is switched off and back on too quickly, the compressor motor stalls with a characteristic humming noise instead of running, and either a PTC trips to stop the compressor or the circuit breaker trips altogether. The same thing happens when the same is done on a refrigerator (and by extension, any device which uses vapor-compression refrigeration).

Why do refrigeration compressors stall when switched off and on quickly?


texts: Why can energy invested in RF radiation not be harvested fully? What are the main factors that affect this? Is there any significant research nowadays that fully describes this process? I stand on the conclusion: "Energy moves from one form to another.", but in this case why can it not be harvested in that quantity to use it for powering low-power devices or store it in significant quantities in some batteries for later use? Why is it not profitable nowadays and why is it not used today like energy from water, wind and other energy sources?