texts: Review of PCB design: ESP32 + 2 Relay design review

texts:
I've completed the design of my pool timer that can turn the pump & light on/off via Wifi and would love to get my design reviewed.  At 120V; the pool light should handle 500W and the pump is a 0.5HP pump.  Since I'm using the HLK-PM03 as a power converter, I've also added a temperature & safety fuse for safety.  2 MOVs are used to protect each relay although the light shouldn't really generate much noise.  There's a jack for a one-wire thermometer; another to help program the ESP32 and a 3 pins of extensions to future-proof the board if I ever need to add additional relays boards without the CPU.  The board will be mounted in a traditional pool enclosure and I plan to apply a conformal spray on it to shield it against moisture.  The digital ground will be connected to the box's ground through the corner screws.  The digital grounds are not connected because I'm creating 2 ground planes (front/back).  The PCB presented below shows a 1mm grid for a total PCB size of 3"x3".  I'd appreciate any feedback before I order the appropriate hardware.
The schematic:

The PCB:

Part list:

J1/J2    https://www.onlinecomponents.com/american-zettler/az215011a120ae-44256439.html
MOC3063 https://www.futureelectronics.com/p/4780375?utm_source=octopart.com&utm_medium=cpcbuynow&utm_content=instock&utm_campaign=Octopart_Ext_Referals
MOV1 https://www.digikey.com/product-detail/en/littelfuse-inc/V14E130P/F5357-ND/1009238
MOV2 https://www.digikey.com/product-detail/en/bourns-inc/MOV-07D201K/MOV-07D201K-ND/2538095
ESP32    https://www.digikey.com/product-detail/en/ESP32-WROOM-32U/1904-1026-1-ND/9381735?utm_campaign=buynow&WT.z_cid=ref_octopart_dkc_buynow&utm_medium=aggregator&curr=usd&site=us&utm_source=octopart
R4
(470)    https://www.digikey.com/product-detail/en/stackpole-electronics-inc/RNF14FTD470R/RNF14FTD470RCT-ND/1975003
R3
(1k) https://www.digikey.com/product-detail/en/stackpole-electronics-inc/RNF14FTD1K00/RNF14FTD1K00CT-ND/1975018
R5
(4.7k)   https://www.digikey.com/product-detail/en/stackpole-electronics-inc/RNMF14FTC4K70/S4.7KCACT-ND/2617510
R1/R2
(10k)    https://www.digikey.com/product-detail/en/stackpole-electronics-inc/RNF14FTD10K0/RNF14FTD10K0CT-ND/1975090
C1
(10u)    https://www.digikey.com/product-detail/en/wurth-electronics-inc/860020672010/732-8856-1-ND/5728801
C2
(22u)    https://www.digikey.com/product-detail/en/wurth-electronics-inc/860020272001/732-8903-1-ND/5728846
F2
(72C)    https://www.digikey.com/product-detail/en/cantherm/SDF-DF072S/317-1124-ND/1014753
F1
(200ma)  https://www.digikey.com/product-detail/en/bel-fuse-inc/RST-200-BULK/507-1169-ND/809313
F3
(630ma)  https://www.digikey.com/product-detail/en/schurter-inc/0034.6042/486-2614-ND/640032
crimp    https://www.digikey.com/product-detail/en/molex/0192110003/WM18374-ND/279175
HLK-PM03 http://www.hlktech.net/product_detail.php?ProId=59
S1/S2    https://www.digikey.com/product-detail/en/omron-electronics-inc-emc-div/B3F-1000/SW400-ND/33150
TERM3    https://www.digikey.com/product-detail/en/nte-electronics-inc/25-E400-03/2368-25-E400-03-ND/11647403 SW1    https://www.digikey.com/product-detail/en/te-connectivity-alcoswitch-switches/1825910-6/450-1650-ND/1632536

Some questions:

I have chosen to place 2 ground planes on the digital side.  One on top and another at the bottom.  I was trying to figure if ground loops would be an issue here.  I could easily route the ground on the bottom layer if that's the case.  But I like the cleanliness of the planes
My neutral is 4mm wide everywhere except when it connect to the MOC since the pads can't handle that size.  That said; the MOC won't take that much power so I connected it to a 1mm trace instead.  I'm assuming that should be fine?


texts: How to remove DC offset of the input signal without using an opAmp?

texts:
Below is a pulse train with a DC offset:

This will go to the circuit below as input.

The thing is this works well in simulation but in real I need to remove the offset of the input signal.

My question is:

How can I remove this DC offset without using another opAmp i.e. just by adding a component to the circuitry ect.? Is there an easy way?


texts:
First of all this question relates to powering Peltier units and not the physical relationship.
I have two Peltier units and a 320w 12v supply similar to this the units are TEC12715. They are physically arranged in next to one another(parallel) and I have wired them in series; they are sandwiched between two heat-sinks which both have fans(also powered by the same supply). I am trying to cool a sealed box and currently the sealed(cooling) side will only drop a few degrees below ambient while the hot side is hitting 60*C.

Should I wire these units in parallel or series?

Thanks,
Mark


texts: Is it possible to make a one-off control FET switch circuit?

texts:
I was wondering if anyone knew any circuits such that when a small voltage is applied for a short duration (i.e. 500 ms), a switch transitions from the off-state to the on-state or vice versa for all time even after the voltage ceases to be applied. Doing it as follows would not be possible since $$ V_{G1} > V_{TH} + V_{S1}$$
Is required for the NFET to be in forward-active mode, as well as $$ V_{G2} = V_{S1} > V_{S2} + V_{TH}= V_{G1}+ V_{TH}$$
So in fact
$$ V_{TH} <0 $$
Is required for the second switch to constantly keep the first switch in forward active after the signal voltage is applied.
I have tried variations of this with PFETs and combinations, but I keep running into the same problem explained above. I think that it would work with relays since their switching voltages don't depend on the voltage across the relay. But would it work with FETs?


texts: S8050 transistor currents not like in the datasheet

texts:
I have a S8050 with an Ib/Ic current gain of about 100. The diagram for the current gain in the datasheet shows Ic being 330mA at Ib 2mA for this transistor. In my circuit I drive a 3.3-5V motor with the transistor, both are fed from the same 4V source. The motor takes about 65mA when directly connected to a 4V battery pack. I measured the following values:

Provided current for base (with 2.2kOhm resistor): 1.8mA, measured current flowing to base: 0.2 mA, Ie = ~50mA

Provided  current for base (with 1.0kOhm resistor): 4mA, measured current flowing to base: 0.22 mA, Ie = ~56mA

While I see a relation between the measured current flowing through Ib and Ie, I don't see it with the provided current for the base. In my understanding the motor should receive the full 65mA from the emitter as soon as I provide a minimum of around 0.5 mA to the base, which would lead to around 80mA for Ie (at least that's what the datasheet claims). But instead the measured current flow into Ib seems to stay static at around 0.2mA and Ie is smaller than expected (but still rising on higher input current values for Ib). Can anybody explain, why? Does transistors have a non-linear resistance on the base?


texts: TV flyback transformer replacement without RC snubber?

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I need to replace the flyback transformer on my Atari SC1224 CRT monitor. The flyback I removed from this monitor has a model number of Kf4825G, and has an RC snubber attached to it, which does not seem to be easily removable. The high voltage cable goes through this to the CRT. Here is a picture of the bad flyback:

The only replacement flyback I've found, which according to the eBay listing it's a replacement Kf4825G flybacks, does not come with the RC snubber. This is the eBay listing for it. And here's a picture of it:

Is it possible that with this replacement flyback, the RC snubber is not needed?
Or, should I attach the existing RC snubber to the new flyback? It does not seem to be easily disconnected from the flyback. Looks like I would have to cut the thick red HV cable? (I don't think that's a good idea)

I already messaged the seller asking this, but he has no idea.

Here is the Service Manual, if anybody wants to see it.

Thanks for your help.


texts: Create specific area in Altium 15 with smaller trace width/clearance rule

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I'm currently doing the fanout for a ~500 Pin FPGA. To keep the layer count of the PCB low, I'd like to lower the clearance/track width in the area of the FPGA in order to route traces between the pads. However, I do not want these low clearances/track widths to be valid for the whole board, to not cause any unecessary trouble for the PCB manufacturer.

Unfortunately, I have no idea how to set up such an area-based rule in Altium 15. If possible, Id love to just create a room and add clearance/width rules for anything in this room, but that seems to not be possible.


texts:
I made a working circuit for an INA122p, for arduino, so it has a 5V PS . I bought 2 ina 126p ic's, because  they are      nearly the same, but when I change the ics, the 126p has a fixed 0,6v signal output. the gain is set to 500.

here is the modified circuit:


texts: Why is there such a big difference between LED brightness?

texts:
I have some LEDS, yellow and blue. Using the exact same battery, the blue LED runs significantly brighter than the yellow one - why is that? I have tested using multiple blue and multiple yellow and blue is consistently much brighter than the yellow under the same conditions.
You can see the difference here:


texts: How to select external components for a buck converter?

texts:
I design a simple circuit activates fan when processor heats up and then control rotation speed.  The fan has a brushless motor with an internal motor controller. So I got the idea to create a buck-mode step-down voltage convertor like this:

Is my calculation correct?
Should I use Low ESR capacitors for the buck converter?
FAN: Sunon MF50100V1-1000U-A99, DC 5V, Imax 180mA@5V, Vapo-Bearing™ technology


texts: How to design a power distribution board?

texts: I want to design my own power distribution board. But I don't know where to begin and key points. I plan to supply the board with a Li-Po battery (11.1 V, 14.8 V) and the board must supply 5 V and 12 V DC output. Also, I want to make current overflow protection, voltage overflow protection, reverse voltage, and reverse current protection. I am open to any advice, especially the protection parts. Thank you for your time.


texts: LED does not blink in Experiment 11 (Make Electronics, 2nd Edition)

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I couldn't make the LED blink building with my breadboard.
So I tried out the experiment with an online simulator.
The LED does not blink in the simulator as well. Is it because the simulator does not reflect the reality, or I connected it wrong?


texts: 8051 with Keil-C filesize issue using a Megawin processor

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0
down vote
favorite

I've written a program using Keil C for a MegaWin 8051 MPC82G516A. When I check the file size of the Intel generated hex file it has a size of 8kb (I see the code in the binary code window), but when I go to program the device using Megawin's tool it increases the code size to around 29kb!? Can anyone provide the reason for why it might be doing this?

Also, something else that is strange is the fact that it seems to be writing the code at the top of the processor memory and not at the start. There are like 4 bytes at the start of the code, but the complete rest of it is in the end of the memory.

Please help

Cameron.


texts: Linear Power Supply Design Thermal Control

texts:
I am a electronics hobbyist trying to make a linear power supply/phone charger. This is a schematic that I have created. Optimally, my load would be a phone charging at 1A and 5V from a usb jack with the D+/D- lines shorted. From some experimenting, a multimeter measurment of the voltage on the wire that gets filtered by the caps and goes into the 5V regulator is ~18VDC. I know that 1A current draw from a 7805 will need serious cooling so I figured a fan would be able to both provide a voltage drop that will reduce the wattage of the 7805 as well as provide some cooling for all the components. My fan is a 12vdc 70mA computer fan. I am stuck finding a way to safely run the fan from an 18V line. I figured a voltage divider would be a good way to create 12v and also take more wattage away from the regulator. I am simply stuck finding values for those resistors. I did some quick math and found that R1 should be ~3.6K for 5mA thru the LED and R2 should be ~1.3k. Does those numbers seem reasonable? Would running the fan straight off of the 18V line be a feasible alternative?
Update: Would something like this form a resistor divider, dropping the voltage going into the regulator?[![enter image description here][2]][2]
[![enter image description here][2]]


texts:
I'm not an Engineer by trade, rather a programmer looking to put together a micro controller project that alters the water flow rate of a cooling system to maintain a specific operating temperature for a piece of equipment.

The media is mains-supply water, so is already at pressure.

What component would I be looking for to control the rate of water flow from a microcontroller? I was pointed in the direction of a solenoid valve, however it appears this is only on/off control not variable.

What is the appropriate terminology for a piece of equipment that provides variable liquid flow control?


texts:
Problem
I found an old (but not in use) garage door controller. The receiver is still intact but can't be reached from souterrain. The sender transmits a single tone on 27MHz in the citizen band. The signal is very weak, I measured 2Vpp (which equals to 10dBm, 10mW). I wondered if it is possible to boost the signal. I have a few of those "5MHz - 6GHz Broadband amplifiers" lying around, which you can get on ebay: https://www.ebay.com/itm/5M-6GHz-Low-Noise-RF-Amplifier-Ultra-Wideband-20dB-Medium-Power-Amp-Board-sz98-/283714550135 Is it possible to chain those amplifiers to sum up their gain?
Experiments
I asked the seller and he states, the modules can be connected together to add the gain of both modules. I connected the RF-Out of stage 1 to the RF-In of stage 2 with a 50Ohms cable and added a 50Ohm dummy load to the RF-Out of stage 2. I was quite suprised that the Gains of both stages were not added, on RF-Out I can read 3.7 Vpp so there was basically no "gain addition".
Questions

Are those modules generally not suitable for TX power amplification or would I need other modules?
Someone posted that one could use a Wilkinson splitter and combiner by first splitting the signal, guiding it through two amplifier modules and then combing them again. Will this sum up the amplification power of the modules used?
Both modules use the same 5V power supply. I have read somewhere this should be avoided. Also true for this case?
In general, can the Vpp output voltage outrank the supply voltage?

Edit
According to the comments and answers, my whole idea points into the wrong direction. That means, leaving the sender where it was the last years or increase gain on the receiver side (better antenna, LNA or upgrade the system with newer technology).


texts: Need of semiconductor instead of conductors for changing conductivity

texts:
Is changing conductivity is one of the reason to use semiconductors?
When we can change conductivity of metals(by some means) then why do we need semiconductors instead in most of the electronic devices


texts: Reason for power on sequence requirement in SoC

texts: In the SoCs that I am working on, memory rail has to be powered up first and then the logic rail. And memory rail is expected to be higher in voltage than logic rail at any point in time. Could you explain me the possible reasoning behind it?There are transistors that are reversed biased with these voltage rails and if the higher voltage rail is turned on later, they get forward biased leaking a lot. But, i need a little more explanation on possible functions of such transistors - may be 1 or 2 examples would be great. I had heard that level shifters go only one way that puts a restriction on power on sequence. But I did not understand how.


texts: Are there any issues with placing castellations on corners of a PCB

texts:
I've had a request from a client for a PCB design with castellations on the corners of the board. The board is not actually rectangular, so the corners are not right-angles but more like this:

I'd like to know if there are any issues with castellations on PCB corners in general (as opposed to the sides), and with non-right-angled corners specifically.


texts: Extremely low volume on headphones after jack repair

texts:
My headphones all of a sudden stopped working in one ear, then both. Same old story, I cut open the plug saw 5 wires (it's a TRRS plug, mic and button + headphones). The wires are

Red (Right Of course)
Blue (Left of course)
Golden (ground of course)
Green (no clue)
Golden and Blue twisted together (no clue)

Just to start off, I stripped the wires, burned the enamel coating, and re-soldered the Red, Blue and Golden wires to old jack only as below-
P.S - picture just for reference

Blank
Ground
Red
Blue

Plugging in the headphones to my laptop (which has a combo 3.5mm jack) I can hear sound on both earcups, but the sound is extremely low. My soldering is pretty shabby, so I'm suspecting that my bad soldering has increased the resistance so much that sound is low, but I'm not sure.

Why is the volume so low and how may I fix it?


texts: Accidentally misconfigured T type thermocouples as J. How do I convert my data?

texts: I was running a test between -70C and 70C using T type thermocouples but misconfigured it on my DAQ(keysight) to J. Is there a way to convert the data I gathered to the correct settings?


texts: Can the characteristic impedance Z0 of a conductor be measured?

texts:
We have a custom made data cable at my work, is there any good way to measure \$Z_0\$ of a cable, or must the formulas be used?

Trying to work out what value termination resistor to use.


texts: What's the cheapest way to do basic EMI testing?

texts:
I need to test that my project will not interfere with radios in the 27 - 72 MHz band.

I can't afford a spectrum analyser. Nor can I afford to buy all tx/rx pairs in between 27 and 72 MHz (27, 35, 47, 72...) My budget is a maximum of £100.

I was thinking of modifying a radio to have a much larger tuning range, but it would need to be sensitive to very low EMI emissions. I've found AM radios are slightly sensitive to noise but probably not enough.

Does anyone have any suggestions?


texts: USB Host and Device communication happen in the same controller preferably Pic controller

texts: Working on new project, which requires- 1st port is for HOST function with Type A connector and 2nd is for Device function with Type B connector & not support USB host port and device port at the same time. how that can be design with PIC controller.


texts: STM32 Custom Bootloader Jump to Application

texts:
I wrote a custom bootloader for the STM32F4 microcontroller and I'm able to write an application to the flash memory at the address of 0x08008000. The issue I have is when I use the jump function the application doesn't seem to execute. I have attached the jump function below. I have disabled all the peripherals, timers and interrupts. Also, relocated the vector table to 0x08008000 to run the new app.

void bootloader_jump_to_user_app(void)
{

   //just a function pointer to hold the address of the reset handler of the user app.
    void (*app_reset_handler)(void);

    //shut down any tasks running
    HAL_GPIO_DeInit(GPIOB, GPIO_PIN_10);
    HAL_GPIO_DeInit(GPIOB, GPIO_PIN_11);
    HAL_TIM_Base_Stop_IT(&htim4);
    HAL_TIM_Base_DeInit(&htim4);
    HAL_RCC_DeInit();
    HAL_DeInit();

    SysTick->CTRL = 0;
    SysTick->LOAD = 0;
    SysTick->VAL = 0;

    //disbale interuppts
    __set_PRIMASK(1);
    __disable_irq();

     SCB->VTOR = FLASH_SECTOR2_BASE_ADDRESS; //0x080080000

    // 1. configure the MSP by reading the value from the base address of the sector 2
    uint32_t msp_value = *(__IO uint32_t *)FLASH_SECTOR2_BASE_ADDRESS;

    __set_MSP(msp_value);

    uint32_t resethandler_address = *(__IO uint32_t *) (FLASH_SECTOR2_BASE_ADDRESS + 4);

    app_reset_handler = (void*) resethandler_address;

    //3. jump to reset handler of the user application
    app_reset_handler();

}

In the linker file for the bootloader I have broken the flash into two parts, one for the app and the other for the bootloader. For the application linker file I have the flash starting at 0x08008000.

/* Memories definition */
MEMORY
{
    CCMRAM  (xrw)   : ORIGIN = 0x10000000,  LENGTH = 64K
    RAM (xrw)   : ORIGIN = 0x20000000,  LENGTH = 128K
    FLASH   (rx)    : ORIGIN = 0x8000000,   LENGTH = 128K
    APPLICATION (rx) : ORIGIN = 0x08008000, LENGTH = 896K
}


texts: Getting an 8-bit LCD display interface to work

texts:
I have a LCD which this controller is used with: LCD Single Chip Driver.

I am trying to get it to work with an 8-bit interface, but in my kit I can't find the three pins that are mentioned in the datasheet IM [0-2].

Here are some descriptions: 2.8" TFT LCD.

and here is the socket description of the LCD kit that I have:
Socket description

Now the current interface of the kit that's working is 16-bit.

That's the schematic of the kit: Kit Schematic

2nd Question:

If this is not possible, it's already connected to FSMC 16-bit, is it possible to just send 8-bit data to the data pins by shifting the data? Because I'm trying to get a large double buffer 140*200*2 bytes and that would eat the memory, so if I have an 8-bit interface would it take less memory buffer, so is it OK to just send 8-bit data to LCD even if the interface is 16-bits?


texts: How to determine current flow direction in a circuit?

texts:
I have this diagram:

The datasheet specifies I should bias the COMM+ line around 1.5V. However, when I measure the voltage at TP1 with the oscilloscope probe connected to ground, the output from the oscilloscope is always 0V (i.e Ground)

I want to understand which way the current flows in the given circuit and what voltage I should see for every division.
The main current source is coming from 3V3. The other source is signal coming from the Coil attached to C23 and R18.
I am trying to get 1.5V at COMM+ through a resistor voltage divider.


texts: Will connecting a NEMA 14-50 to a IEC 60320-C13 in this manner present issues

texts:
I have a japanese item in my house which takes a considerable amount of power (>1.5 kW) and takes a C13 power plug expecting 210-250V at 50-60Hz.
My idea was to connect a NEMA 14-50 power cord in such a way that it will provide the needed voltage to the target. Here was my connection idea:

My main concern is that when you conventionally think about the wall socket, the earth is the same as neutral (in terms of electric potential). With this setup, the earth will not be the same as either prong, which I fear could introduce safety hazards.
Are my worries justified, or will this configuration be benign?


texts: Child-Safe setup for ESD protection environment on desk

texts:
I need to setup an anti-static workbench in my spare office, and kids sometimes get into it ever since they learned how to pick the locks.

My intended approach is to:

Lay out an ESD mat on the desk.
Punch a whole through the mat, and connect an ESD common point ground to the mat through the whole with a snap-cap.
Connect my ESD wrist strap by removing the alligator clip and connecting the wrist strap to the common point ground.
Connect the banana jack of the common point ground to the GND pin on the NEMA-5-15 wall outlet or equivalent on the power bar on my desk, ie:

I have one problem with this setup, assuming it is correct: I have a small, flat nema-jack connected to the GND of the wall outlet with an exposed banana plug sticking out of the wall. I'm worried that one of the kids could pull the banana plug out of the GND plug, and plug the banana jack into the hot or neutral blade slots of the wall outlet.

Is there a safer way to go about this? Are there maybe 3-prong plugs that have two plastic blades for the neutral and hot, and a fixed metal plug for the GND so there's no way someone can electrocute themselves by playing with the connector to the mat?


texts: Can the negative impact of mixing new and old batteries be mitigated?

texts:
Mixing old and new batteries is bad.

But there are various options how they can be mixed, and I guess there are use cases in which certain ways of mixing can be justified.

In my off-grid solar system I am using quite good lead-carbon batteries capable of surviving 4000 cycles when discharged up to 50%. Their Partial State of Charge (PSOC) wear is minimal. Also they can be charged 2.5 times as fast as traditional lead acid types. At the moment I am running 12 of them — connected in 3 parallel quartet series. I am giving them quite hard times — discharging down to 50% every night and topping up to 100% during daylight.

Now I want to scale the array up — add another quartet or two. Say if I do it this way it perhaps would be quite bad:

But a gut feeling tells me I might get away with this:

I am sort of lazy to do the calculations vs ask this question. Is my gut feeling wrong or right? Is there any difference between the two options above? How much will the new batteries suffer if the old ones are only say 20% worn? Should I even think of scaling the array up, or should I just wear it out completely and buy all new batteries thereafter?


texts: Transistor Noise A Concern In Emitter Follower

texts:
I'm looking at using a high voltage BJT as an emitter follower in a high voltage tube audio application (guitar amp). Unfortunately in the range of 200V, most BJTs are marketed as switching transistors and have no noise specs etc. Also I'm aware transistors in this range have a low beta, that's fine, I'm looking to still have some source loading.
My assumption is due to a large input voltage, any noise that the transistor would add to the circuit is effectively negligible. That being said, I am not familiar with understanding noise figures in dB vs affect on something like an emitter follower...
Question: In general for emitter followers, with a typical ~100mV to ~10V AC signal bounded in the audio frequency realm, Does the quality of transistor matter?


texts: How to connect a 1mA IR receiver with a 20mA led in the same circuit?

texts:
datasheet of ir reciever

I tried connecting them in parallel and in series but neither gives correct amperage to the components


texts: How should I make the gain outside the bandwith of this low pass filter less than -50dB?

texts:
I want to block all frequencies higher than 12kHz coming from diffrent sources.
The required filter should have the fastest response possible without inducing any ripple and the gain inside the bandwidth should be higher than +20dB and outside it should be less than -50dB.
My question is how should I design it to have the gain outside less than -50dB.
I'm new to non linear electronics so I don't have much experience.
I know exactly the steps to do for a Sallen Key design but it's just that this outside gain that is confusing me. Does this mean that I should use a 3rd order low pass filter with a Chebyshev 3dB type?
Because if a 1st order LPF gives an amplitude of -20dB/decade this means that I need a 3rd order LPF.


texts: How can we have high voltage and low current (in transformers), if V = I * Impedance?

texts:
I have researched a lot on this topic (including this site) and found this link somewhat helpful :   How is it possible to have high voltage and low current? ...
        But still it seems to fall somewhat short.

People have explained that since power must remain constant(no losses in ideal case) then power in = power out, i.e.

$$V_{in} \cdot I_{in} = V_{out} \cdot I_{out}$$

and

$$\dfrac{V_{in}}{V_{out}} = \text{Ratio of number of turns in primary to that in secondary coil}$$

But how is this possible? Let's say the plant can supply power of 1000 W, @1000 V and 1 Amp.
The voltage is determined by the generator but the current is determined by the impedance of the circuit having the primary coil. Lets say the transformer is step down and the voltage induced (RMS) is 200V. According to previous logic, the current must be 5 Amps. But shouldn't it depend on the resistance(or impedance) of the appliance we have connected to the secondary coil?

EDIT 1 Why does the primary impedance depend on Np/Ns Ratio? Is it due to mutual induction? And why does actual load impedance in secondary depend on that ratio and not what appliances we have connected across the secondary coil? If I connect different number of appliances will the voltage induced across the secondary change?

Edit 2  If the primary impedance is changed by connecting /disconnecting "appliances" then will the apparent power to be supplied by generator change? What about actual power? (Although power in = out, I'm talking about the value) If so, how does the generator manage to change the power supply?


texts:
I have this exercise of a Thevenin's equivalent that really got me confused with it's usage of a transistor and was wondering if I could get some help with understanding how to solve this particular circuit.

R1= 47 Ohms

R2= 47 Ohms

RC= 47 Ohms

RE= 47 Ohms

V1= 15 V

V1= 15 V

The exercise: Calculate the current th IB through the point B in the transistor, if the current IE through the resistor RE is 2.7 mA, and the voltage between point B and E on the transistor is 0.7 V.

Also you don't need to know about the transistor as a component to solve the exercise. It's good to know that the current IB is normally way smaller than the currents IC and IE in the transistor.


texts: Cortex-M0+ check if running under debugger control

texts:
I would like to check from my firmware if the MCU is running under debugger control. The MCU is a Cortex-M0+ KE06Z128.

On M4 I used to check a bit in DHCSR. Even though this register exists in M0+, it seems to not be available to the firmware (I can't find it anywhere in device headers).

Is there a way to check if an M0+ is running under debugger control (apart from setting some variable by the debugger)?


texts: Best way to create an Adapter to connect an eDP LCD panel to Mac/PC USB-C or DisplayPort?

texts:
I look for guidance on how I can best reuse a Panasonic VVX14P048M00 LCD panel (3000x2000, 13.5", 4-lane eDP v1.3) as a secondary screen via USB-C Video Function or DisplayPort.
Besides adding some backlight driver, is it possible to simply route the panel's eDP signals to a DisplayPort connector, or is some interface logic be necessary, e.g. a signal repeater chip like the SN75DP119?
Thanks for sharing your experience.


texts: Automatic Button Pushing Device Hardware

texts:
I want to make a wrist mounted button pusher, connected to a timer that can be programmed with a routine to push buttons at specific times accurate to a millisecond. I've been told I could use a micro-controller and a servo motor to do this, but I don't know enough about electronics to find a controller I could program or a motor that would be accurate to a millisecond.

First: Is this even possible?
Is this the best way to approach this?
Where can I find the materials I need and learn how to put it together?


texts: Ultra low noise charge sensitive preamplifier

texts:
I developing charge sensitive preamplifier for radiation detector. This is a very sensitive device, the smallest amount of noise can completely ruin the signal.
The schematic and the PCB you can see on these pictures:

The left part of the circuit is separated from PCB, later it will cooled with peltier.
The wide olive rectangle on the PCB is a metal shield. All of the circuit, except the supply voltage filters is under this metal shield.
First question: Is it a good way of shielding out a noise? Should I add other parts below this shield or remove some?
Also the whole of the circuit including detector, etc. will be in metal case.

I added ground plane to the PCB except below of the mentioned metal shield. The whole of the bottom layer is a ground plane, including under the metal shield (but the layer is hidden on this picture).

I have thought a lot about to separate or do not separate grounds, if yes, then which ones?

Finally I decided to separate ground from HV source together with R6 resistor ground and with Q1 FET ground. This all will be connected on the output ground as you can see from schematic.

The output of the preamplifier will be connected through BNC to other chain of signal processing.
Q2:Its is good way of grounding? The GND_HF on OUT1 connector should I connect to power ground?

My plans are using standard metal film 0805 resistors, low ESR elko-s and MLCC 0805 capacitors.

The circuit is from here: Low noise charge sensitive preamplifier DC stabilized without a physical resistor


texts:
I am trying to boost audio signal from around 3V to around 60V for a piezo element with a component as small as possible.

I found audio transformer MET-23 that reflects 1.6 kOhm impedance on primary when there is 3.2 Ohm load on seconday (http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/MET-23.pdf). Music player says that the impedance should be 32 Ohm.

This is my train of thought: I was planning to hook up the transformer backwards to boost the voltage. Piezo element which acts like a capacitor produces capacitive reactance which is xc=1/(2*pifC) where f=1kHz (sound average frequency). Secondary impedance should be then |sec coil inductance - piezo capacitance| (if I don't count the resistance). That impedance should reflect on the primary so primary impedance is sec impedance*(1/22,4)^2. If the primary impedance is below 32 Ohm then I can just add a capacitor to primary.

Is this correct way to do it?


texts:
I'm trying to design a circuit based on an ATMega328 (from an Arduino stand-alone type kit), and was planning on adding a USB connector and powering the board from a generic USB phone charger type device.

Do I need to add a voltage regulator to my circuit, or can I just assume the charger will give a good enough 5V supply?

The instructions I found at http://arduino.cc/en/Main/Standalone show how to add a regulator, but I'm not sure if I need it.


texts:
I want to use raspberry pi for a vehicle park project. The Raspberry will stay in a metal box and it will never power off. The metal box is waterproof but its in middle of a empty area so it will get really warm under sun and really cold at the winter.

So can I use raspberry pi for a project like this? Can someone give me idea?


texts: Fast switching (microsecond to nanosecond) voltage using 10V signal pulse

texts:
I have an application where i need to be able to switch from a 20V supply to a 40-50V (variable) supply in a very small amount of time. Ideally this changeover needs to be prompted with a signal pulse in the region 5-12V. It also needs to occur as fast as possible - the microsecond to nanosecond regime.

I have the power supplies ready and varying the voltage is also taken care of, however I've yet to find a suitable way to switch between the two at these speed.

Edit: Some more information about the application below.

I'm driving a CCD; an imaging device that converts light into electrical signal that is stored within pixels. The signal is read out and used to recontruct the original image. Within the pixels are seperate gates that have biases applied to transfer charge between one pixel to the next. This transfer process occurs in the us to ns regime depending on operation speed.

The typical gate voltage is around 20V for this device. I need to be able to increase this gate voltage from 20V to 40V and then reduce it to 20V again in a time comparable to the speed at which charge is transferred from one pixel to the next. The gate voltage is currently controlled by a power supply that contols the low level, the plan was to add another that controls the high level and to switch between the two quite fast. I'm trying to design a ciruit that interfaces the power supplys and supplies the voltage needed to the gate of the CCD.

Ideally I'd like a switch where when its in the "off" state, the 20V is being supplied and when its in the "on" state the high voltage is supplied. There needs to be no time where no voltage whatsoever is supplied (I may have about 1-5ns of grace, but not much room for error).

I'd previously done this by hooking up a couple of relays, but they are too slow. Is there a faster alternative out there that i can get hold of in a single IC package?

In terms of requirements the max voltage will be about 50V DC. the max current draw will be about 200mA.

Forgive me if the answer is very simple, however I've searched for answers with not much luck.


texts: How to increase distance between PHY and RJ45 for GbE?

texts: The PHY I will be using is unfortunately far away from the front panel RJ45 jack (with integrated magnetics). Approximately 13 inches. This is over the maximum recommended distance between the PHY and the magnetics. Is there some sort of a redriver/buffer/equalizer IC that i can use to boost this signal midway?


texts: Two directional FET switch. Is it possible?

texts: Is it possible to have a high side MOSFET switch that will allow any direction of current? I was trying to design one but without the success. Or should I use a relay?


texts: I have a motor that I pulled off a broken Dyson v8 hoover. When I removed the broken driver circuit(the capacitors snapped off) I found this motor layout with 4 coils and no wiring pattern. How can I connect this motor together in order that I can drive it with a constant DC power source. Thank you for your help!


texts: When using NOW in ModelSim in VHDL simulation, what determines the time resolution or its unit?

texts: The value returned by now could be in ps or ns or some other unit. How do I know what the unit if the returned value is and what in modelsim or VHDL is used to control this unit or resolution of time?


texts: I am designing my personal FM receiver, and I have a question regarding how to design my Antenna, in terms of choosing the wavelength to determine the size of the antenna. To put it as simple as possible , how do I select my the length such that it can detect 88-108MHz?


texts: Proteus - problem with voltage and current measurements

texts:
Okay, don't hate me too much or criticize me here. I'm just new to Proteus and I don't know which part I got it wrong but if you'll help me out, I'd really appreciative it!

In the first picture, it's supposed to have a total current of 10 A and then 6.25 A, 1.25 A and 2.5 A respectively but it keeps me giving this weird numbers. I know they're quiet close however my professor won't accept it.

Same problem here too, obviously it's supposed to give out 125 V but why is it giving 124 V?


texts: confusion regarding transfer function of feedback system?

texts:
As shown highlighted in attached photo,the sign in denominator of the transfer functions
Are these both signs correct?or one of them should be negative?If yes,which one should be negative??


texts: What is the maximum resistance that is allowed when connecting two grounds in a 5V unit?

texts:
Say I have a 5V Arduino and I want to connect two grounds (I don't have another idea of anything else I would like to short). How good should the conductive between them be? For example if I want to share grounds of the MCU and another power source. Wires will always work but what would happen if I use lesser conductive materials?

Edit:

On a practical level-
In one scenario I using a 0.5-2A motor with a power source of 6-12V along with an Arduino.
In another I connect to an Arduino two grounds of a unit that draws for it between minimum current (LCD) to 20mA.

Can I use a trail of conductive glue or a piece of a common conductive cloth (say 0.5*5cm->100ohm)?


texts: Trying to draw the schematic for a power divider circuit

texts:
I want to draw both the schematic and layout for the following power divider circuit using microstrip lines in ADS. First of all I want to see if my schematic agrees well with theoretical results at all.

Here I have drawn the schematic. I'm not 100% confident whether I've ended up with the right schematic configuration to begin with. Particularly I'm not sure whether or should I need to use step junctions, junction Tees as required?

To check my schematic I did an S simulation and drew magnitude of S11 for comparison. The left shows my simulated result while the right depicts the result obtained from theoretical calculations given in this paper. As you see it doesn't well agree with the theoretical results :(

Note that as far as S11 concerns the series connected R and C does not matter at all (a result verified by even- and odd-mode analysis given in the paper). So for simplicity I didn't include them in the schematic. So now I don't know what I should do to get as close as possible to the actual S11 response. What practical considerations have I missed?


texts: I am trying to understand what it means by an IR receiver that has transmission range up to, say, for TSOP1738, 35m. For example, if the receiver's working at 38 kHz, how much sensitive would it be to IR LED transmitters that are way further away but working at the same modulated frequency with a much lower emitting range of a few centimeters? Does it ever detect them? I guess since it has a broad range, it should be able to detect any (even weak) 38 kHz wave circling around? In case it's gonna detect them at a long distance, how actually it does? Please clarify these for me.


texts:
I have multiple RFID cards that I use to get into parking garages at the office, client site, home, parents place, etc, etc, etc.....

I'd like to either

A) combine all of these into 1 card or device (perhaps pressing a button to send the right signal?)

Or even better B) Have a way to transmit the proper signal from a device mounted in my car with a dash button.


texts: What is the time constant L/R of this circuit?

texts:
I've solved this circuit but i got some issues about the alternatives.

English question at this picture:

Switch \$S_1\$ had been closed for long time and after that \$S_2\$ was opened. Therefore, at \$t=0\$, the switch \$S_2\$ has closed.

The current \$i_1(t)\$ is equal for \$t\geq 0\$

My attempt:

\$L\frac{di_1(t)}{dt} + i_1(t).1 = 2\Rightarrow\$
\$i(t) = C.e^{-t} + 2\$

\$i_1(t=0^-) = i_1(t=0^+) = 2V/2\Omega = 1A\$

\$C = -1\$

\$i_1(t) = -e^{-t} + 2\Rightarrow \boxed{i_1(t) = 2\left(1-\frac{e^{-t}}{2}\right)}\$

\$\tau = 1s\$

Is this alternatives about that question all wrong respecting time constant?


texts: Voltage spike at the coil when opening the switch

texts:
I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

In my book they stated the following sentence:

  After that the switch is closed for a long time, I let go of the switch. The voltage at the node \$Y_1\$ will rise in a few miliseconds to about -90 volts.

Question: why is that true? Because the supply voltage is way way less than 90 volts. How can the voltage at the coil exceed the supply voltage soo much?


texts:
This may sound like a very stupid question. However, I am new to the Z80 stuff. I am planning on how to connect the Z80 control signals to a SRAM. But the Z80 has seperate RD and WR, while my SRAM has them combined. My issue is that the Z80 when is reading for example, instead of just low, it makes a square wave. Any ideas?

SRAM Model: TC551001BPL-70
Datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/31687/TOSHIBA/TC551001BPL-70L.html

READ IS HIGH
WRITE IS LOW


texts: Xbee not responding timely. Large delay between each transmission

texts:
I have prepared a setup for 2 Xbees one connected to the PC via XCTU and the other interfaced with Atmega 168. The terminal software will send 1 and the xbee with Atmega 168 will return 1.

The code is as follows.

#include<avr/io.h>
#include<avr/interrupt.h>
#include<util/delay.h>

    unsigned char data; //to store received data from UDR1

//Function To Initialize UART0
// desired baud rate:9600
// char size: 8 bit
// parity: Disabled
void uart0_init(void)
{
 UCSR0B = 0x00; //disable while setting baud rate
 UCSR0A = 0x00;
 UCSR0C = 0x06;
 UBRR0L = 0x06; //set baud rate lo
 UBRR0H = 0x00; //set baud rate hi
 UCSR0B = 0x98;
}

ISR(USART_RX_vect)      // ISR for receive complete interrupt
{
    data = UDR0;  //making copy of data from UDR0 in 'data' variable
    if(data == 0x31)
    UDR0 = data;                //echo data back to PC

}

//Function To Initialize all The Devices
void init_devices()
{
 cli(); //Clears the global interrupts
 uart0_init(); //Initailize UART0 for serial communiaction
 sei();   //Enables the global interrupts
}

//Main Function
int main(void)
{
    init_devices();
    while(1);
}

This code works well and the following is the desired and the obtained output...

Now the problem is when I want to get reply 3 for a transmission of 3 from the PC. I am using avr studio 4 (yeah I know I am backdated) and Atmega 168PA-PU. The configuration for both cases is as shown in the image...

So I copied the previous program totally and just changed the line

ISR(USART_RX_vect)      // ISR for receive complete interrupt
{
    data = UDR0;  //making copy of data from UDR0 in 'data' variable
    if(data == 0x31)
    UDR0 = data;                //echo data back to PC

}

to the following

ISR(USART_RX_vect)      // ISR for receive complete interrupt
{
    data = UDR0;  //making copy of data from UDR0 in 'data' variable
    if(data == 0x33)
    UDR0 = data;                //echo data back to PC

}

But the obtained output is nowhere near what its supposed to be. The following image should clarify.

PS: We used separate (Atmega 168A-PU & Atmega 168PA-PU) for the two programs. It may so happen that there is some discrepancy in the internal oscillator. I have read somewhere that there can be a +/-10% inaccuracy.


texts: How to find the direction of current of the circuit?

texts:
Okay this is the circuit

The magnet given is moved up and down continuously at a high rate through the coil and generates a peak voltage of 4V.

I eagerly use the right hand rule in order to find the direction of the current . But what I have found is very-much  confusing.

To use the right hand rule the I assume that the magnetic field is pointing downwards, so without any doubt I point my  fingers towards that direction, I.E I got the dorection of current as rightward. But I am confused with it.

Yes of course I got the direction of current point toward right side, but I am muddled due to this spiral thing in the coil,because in the coil we have springs which are usually take a shape of a circle place in a 3-D space , So I couldn't get a clear idea about where does the current coming out whether it is from the upper end or the lower end of the coil.

So how can I make this puzzle clear?


texts: Would an inductor and a wire in parallel have an equivalent inductance of 0?

texts: Since the equation is \$\frac{L_1L_2}{L_1+L_2}\$ and one of the wires has an inductance of zero , would the \$L_{eq} = 0\$?


texts: Cascade of 3 MCP1663 to generate 100V @ 100 mA

texts:
I would like to generate 100V from one LiPo battery at a output current of 100 mA.

There are circuits with transformers but there are a bit bulky and expensive. The MCP1663 can generate 32V from 3.3V with one 10 uH coil and an output diode. Is there a nice way to build a cascade out of three MCP1663 where each output ground is connected with the output voltage of the lower stage to charge one common capacitor to 100V which can then draw 100 mA. Since there is no isolation to the input stage, what could be the problem?


texts: Orcad hierarchical design alias / physical net

texts:
A hierarchical based Orcad schemactic has two children blocks and the parent one. Each child block is connected through the parent via the net called VDD_IN. However, once I hover on the net, a physical net number is shown alongside the alias I attributed to it. What is bugging me is that in Orcad PCB, only the physical net is showing up after reading out the netlist. Is there a way of forcing the alias to be used in the Orcad PCB?

Here are the relevant part of each child block:

Thanks.


texts: Can somebody explain why folding circuits are used in ADC.  I know that they are used to estimate the noise but exactly how is this done.  Also I would like to know in what kind of ADC is this used and do they suffer from problems such as non monotonic, DNL or INL.


texts:
I want to use this Half Bridge Driver for a Buck converter Design. To validate it, I wire the connection as the simplified application diagram in the datasheet, with .1 uF capacitors. The input VDD is 12V. I feed the High and Low inputs with a %50 percent fixed duty cycle at a 15KHz frequency using a micro-controller as shown below on the Left. There was a small dead-band included for protection.
I expect the output at HO and LO without anything connected to be a square wave but I receive the output below on the right, where green is the low side, and yellow is the high side:
What did I do wrong? What Can I check? When I turn the driver on without input I see a biased Voltage around 10V.


texts:
I am using an LM2596 module with my project because it has a good efficiency and a stable output voltage.

My question is about the potentiometer found in the module.

Does it select the output voltage value what ever the input is, or does it just select the output related to input?
So if I set the output to 5v with 12v input will it change if I give 9v input with resetting the potentiometer?


texts: Question about time constant of Voltage Multiplier

texts:
Time Constant is Large Compared to Time Period i.e. $$R_LC_{1,2}>>T=1/f$$

can someone please explain, whats the meaning of this line and how is this affecting the circuit behavior. I am looking for answer in little bit simple language. Thanks


texts: How can a diode parallel to the source can't take the source value but take about 0.7V?

texts: I was practicing diode circuits and this question stucked in my mind. When a diode connected parallel to a DC voltage source, doesn't it have to take the value of the source rather than 0.7V according to Kirchoff laws ? ( the diode is forward-biased )


texts: Simple curve to illustrate how much current it takes to turn on a PN2222 transistor?

texts:
It's been about 30 years since I studied transistors so please forgive my basic question.
I bought my kid an Arduino kit to give him a basic taste for how electronic circuits work. Included in the kit was a couple of PN2222 transistor. Not having a large potentiometer, I set up the following circuit, using all the large value resistors that came with the kit:

simulate this circuit – Schematic created using CircuitLab
With a jumper, I can crudely vary the current flowing into the emitter. I was very surprised to see that 10 100K resistors were not enough to turn the transistor off. I was even more surprised that and additional 10 1M resistors were not enough to shut it down, though the LED was very dim. I was also surprised to learn that the transistor consistently dropped around 3V no matter how much current was coming into the emitter. I have forgotten a lot, it seems.
I looked at the technical specs for this device that shows some plots but I honestly couldn't make heads or tails of them. How do I figure out how much resistance it will take to turn the transistor off?
And does anyone know of a simple curve that can help illustrate how the transistor is behaving in relation to the changing resistance on the emitter?
Thanks.
Photo:


texts:
Disclaimer: I am not an electrical engineer, and nowhere near studying it either. This is just a curious question which I got and couldn't find an answer to.

I am aware of how several pixels are used to make up a television screen. Each pixel consists of 3 LEDs; one red, one blue, and one green. By varying the intensity of either the red, green, or blue; it's possible to bring about any possible color that exists.

My question is, what are the wavelengths of the light that these blue, green and red LEDs emit? Does it depend on TV to TV or is it general?


texts: Increase voltage from 5 to 12V to deactivate a display

texts:
I'm developing a timer based on this project: Digital Stop Watch with ATmega8 by Avinash Gupta (I cant put the link, because my reputation is too low)

Original schematic:

At first, I made the same schematic (as in the image) with 13mm x19mm and 5V displays and it works fine. The displays work perfectly. Then I change the displays by larger 12V display (something like 5cm x 10 cm). Now, I have a problem: the segments of the display dont turn off at all.

I supply the display with 12V throught BC558 transistor and when I want to show a number: 1, for example, the others segments of the display dont turn off, them only dim a little bit. Later I tried many ideas about the origin of the problem we saw that the problem is this (or we think so): the digital signal from the microcontroller is 0V (to turn on the segment) or 5V (to turn off the segment). The low voltage works fine to turn on the segment because the voltage throught the led is 12V (bigger than threshold voltage), but the high voltage dont woks to turn off because the voltage trought the led is 7 (12V from the transistor - 5V from the micro) and this voltage can turn on the segment (a little dim). So we try to increase the voltage from the pin of the micro using a common emitter transistor (emitter to 10k resistor to ground, base to the micro pin and collector to 12V) and a lot of other configurations, even with an op amp in compare mode. All this in order to increase the voltage of the digital signal to 12V. But all this doesnt works.

After this, I see that that exist two reason for this problem:

1) The 5V from the Port C in the base of the PNP transistor is too low to turn off at all this transistor, when I want deactive the display. So I need increase the voltage in the base of this transistor to 12V in order to turn completly off the transistor. When I have 0V from the Port C all works fine with this transistor, because turn on perfectly.

2) Similarly, in the Port D, when I have 0V all works fine, because the voltage throught the display is 12V, enough to turn completly on this. But when I have 5V in the Port D, the voltage throught the display is near to 7V and is not low enough to turn off the display.

Thats the reason why when I tried to level shifting only in the Port D of the micro doesnt works. I need to do both two level shifting in Port C and Port D.
Then, I assembly this circuit: , but this circuit doesnt works. I dont have idea whats happen. Just seems like if the display segments turn on almost all time and turn off when they want.

Excuse me for the large explanation. Now, can someone help me to know how can I solve this problem?


texts: Crosstalk between Ethernet and Analog Signals on PCB

texts:
I am wondering the possibility of crosstalk between the two ethernet lines and an analog signal.

The ethernet will operate at 100MHz. If I place positive and negative traces in parallel and place them sufficiently away(is 5 times the Width of the trace enough?) from the analog signal trace, will it prevent it from affecting analog signal majorly?


texts:
I have this programmer. It works fine with their custom software and on windows. But when I try to use it on linux it shows errors. Its some kind of avr-doper clone I think. Don't know for sure.

I am running it into the hid mode. But i get this error

rick@Abigail:~$ sudo avrdude -F -t -c stk500v2 -p m16 -P /dev/hidraw0
avrdude: ser_open(): can't set attributes for device "/dev/hidraw0": Inappropriate ioctl for device

Any ideas what to do? I have also tried /dev/usb/hiddev0. But it still doesn't work. The manufacturer says I sure use robokitsusbprog, but that results in device not found. Any ideas? It also has a serial mode. But that shows this error

rick@Abigail:~$ sudo avrdude -F -t -c stk500v2 -p m16 -P /dev/serial/by-path/pci-0000\:00\:1d.0-usb-0\:1.3\:1.0
avrdude: stk500_2_ReceiveMessage(): timeout

Here is the demsg outputs for when I add the HID jumper

rick@Abigail:~$ dmesg | tail
[ 9246.117266] usb 2-1.3: new low speed USB device using ehci_hcd and address 9
[ 9246.297138] generic-usb 0003:20A7:0264.0005: hiddev0,hidraw0: USB HID v1.01 Device [Robokits Robokits USB Programmer] on usb-0000:00:1d.0-1.3/input0

And this is when I remove the HID jumper

rick@Abigail:~$ dmesg | tail
[ 9295.220180] usb 2-1.3: new low speed USB device using ehci_hcd and address 10
[ 9295.343748] usb 2-1.3: config 1 interface 1 altsetting 0 endpoint 0x1 is Bulk; changing to Interrupt
[ 9295.343758] usb 2-1.3: config 1 interface 1 altsetting 0 endpoint 0x81 is Bulk; changing to Interrupt
[ 9295.358656] cdc_acm 2-1.3:1.0: ttyACM0: USB ACM device

Also it does work in windows as an hid device

EDIT

I tried to run this on a 64bit machine with 32 bit Ubuntu 10.10 on it, it worked with that. Any guess why its not running on the native 64bit OS?


texts: connecting 2 GNDs with relative voltage difference

texts:
I have USB ground and Lab Voltage Source ground, for which I need common reference. I thought I could just connect them together, but I found, that USB ground is relatively higher than Voltage Source ground (1.5 V difference). Even more interesting was the current measurement ("short-circuiting" those 1.5V with Ampere-meter), that yielded only 4 mA.

Question:

What is going on when the 2 grounds (that are relatively different) are connected together?

Why there is such small current between terminals that have 1.5 V difference? Shouldnt  short-circuiting them produce high(er) current? (relatively higher - e.g. USB can handle up to 500 mA)


texts: Level shiffter (3.3V / 5V) for controlling transistors

texts:
Is it possible to control the base of the transistor using the level shift chip (3.3V / 5V)?
I want to use the SN74AHCT125 level shift chip.

Transistor BC337-16


texts: PMOS Inrush Current Limit - Where to place Capacitor

texts:
In order to reduce back-EMI of a Buck converter a LC input filter is to placed in front of the converter. To limit the inrush current when those caps are charged I consider to use a PMOS with a RC filter at its gate.

The following schematic shows the whole input stage including inrush current limiter (M1), reverse voltage protection (M2) and fuse.

During simulation I noticed that placing a capacitor from gate to source (C5) is much more effective in limiting inrush current than placing it from gate to drain (C4). This contradicts sources on the net like here that show the capacitor from gate to drain. Is the effect I see only in my simulation or is this due to the fact that I don't actively drive my PMOS but effectively tie it's gate to ground?

simulate this circuit – Schematic created using CircuitLab


texts: I'm looking to make a battery life indicator that I can use in conjunction with a micro-controller. I'm hoping that I can then read the current battery life remaining and increasingly put the micro-controller to sleep to preserve battery life.


texts:
I'm creating a box that will have an external TTL trigger. I want to isolate my box's power/ground from that of the triggering device.
Obviously, an optoisolator is the way to go (eg. PS2502).

HOWEVER...
I want to offer V+ and GND as well as the Opto's anode/cathode so that an unpowered device (eg. a dumb toggle switch) can run the trigger in addition to powered devices (which can src the current to turn on the opto). I'' build a series resistor into the exposed V+ so the opto can be direct-connected with no worries.

simulate this circuit – Schematic created using CircuitLab

Of course, in the above ckt I don't really need isolation.

BUT, when an external, powered device is used to drive the opto, and I want to ensure that the external device's pwr/gnd can't be tied to my pwr/gnd. NO GROUND LOOPS!

I don't need a whole lot of power - 10mA is easily enough to trigger a photodarlington like the ps2502 (or maybe something like a SI8710CC).

The parts I'm finding are in the several dollar price range. There's gotta be something like this for under a $1... can anyone suggest a part?

Thanks!


texts: Frequency of the standard battery discharge curve

texts: What can we say about the frequency of the discharging battery? You know that batteries, for example Li-Po, have a characteristic charge and discharge voltage curve. And under a certain rate of discharge and a certain load, the voltage drops for a time, for example from 4.2 V to 3.7 V in 1 hour. I wonder how can we calculate this frequency? The change can be very slow but imagine a battery goes 4.2 V to 3.7 V in a second and we measure the voltage with an oscilloscope.


texts: Ensuring certain amplitude level of RF signal on a PCB board

texts:
I have an RFIC which has an LO input. This LO input has rails 0V and 1V and the LO input should be rail-to-rail. The termination is on-chip and may not be perfect.

The LO comes from an off-board 90 degree hybrid and enters the board via SMC connector and this is the board schematic into the chip:

simulate this circuit – Schematic created using CircuitLab

How do I make sure that the 2.1 GHz LO signal is rail-to-rail at the chip input pins?

I have a GHz DSO and GHz active probe but I think that's still not enough to probe the signal there.

I have the S-parameters of the MABA balun and a transistor level model of the chip input. I hope with these I would be able to create a reasonably accurate model in a circuit simulator (Cadence). Then I would know (< 1dB) which power exactly needs to go through the SMA. If everything would be perfect, that number would be +10 dBm (the MABA balun has a 1:1 impedance ratio, hence the ideal impedance at the differential outputs is 25 Ohm and hence the amplitude is halfed. 1Vpeak at the port input is +10dBm at 50 Ohm).

Now I would have a coupler in front of the SMA input which is connected to an RF power meter.

Is this the proper way to do it?
Which coupling ratio is proper for this scenario? I thought about 30 dB ... giving minimum insertion loss but -20dBm should still be nicely detectable
I have I and Q LO inputs on the board. For matching, I would insert the coupler on both inputs but connect the power meter on just one (since I only have one). Is there anything wrong terminating the unused coupler with a normal Mini-Circuits 50 Ohm terminator?
How to deal with the fact that the signal path will not have perfect 50 Ohm termination? To my understanding, only the incident RF power would be coupled to the RF power meter and the power meter would not see which part of this is actually absorbed by the chip input (hence giving rise to the desired amplitude level) and which part reflected.


texts: Bi-Directional Level Shifter Circuit with pull-down resistors

texts:
I'm looking for a bi-directional level shifter circuit to interface a 3.3V controller to a 1.8V component which is not 3.3V tolerant. Usually I'm using the well-known level shifter circuit, e.g., https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide. This circuit will output a high logic-level on either end unless one end is pulled low which causes the other end to go low as well. This works well for bus-systems such as I2C or One-Wire where the bus wires are usually pulled to Vcc using resistors.

However, I now have to interface with a bus-system (MIPI RFFE) that uses pull-down resistors to set the bus lines to GND level unless a bus device pulls it to Vcc. The bi-directional level-shifter circuit does not work in these cases (at least not bi-directional, I was able to hack something for devices that only require writing). Otherwise the bus is very similar to I2C.

Can anyone point me to a circuit that implements a bi-directional level shifter that outputs a LOW-signal unless one end is actively driven HIGH?

Addition 1: Regarding the comments using P-Channel MOSFETS and Pull-Down Resistors.

Wouldn't that cause the loss of the level-shifting capability of the circuit. As far as I understood the pull-up based level shifter the Pull-Up resistors cause a High potential on either end and the transistor to be "closed". Now, when one end pulls the line low, the transistor will open in any case connecting both ends and hence, pulling the other side low as well. I guess the reason that this works is that LOW potential is the same for both sides of the circuit.

My guess is that when I use a P-Channel MOSFET with pull-down resistors, whatever HIGH-potential is applied to one end will also appear on the other end which goes against the level-shifting requirement. Or am I missing something here?


texts:
I have searched for troubleshooting the ULN and did not find any solution.

I use a ULN chip in a motor inverter for controlling precharge relay and main relay.
The problem is when the motor inverter is powered off, and for instance the charging is on (battery charging)  the relay will kick in getting negative trough the unpowered ULN??? Sounds strange, but It's happening.
And I don't want the motor inverter ON all time (uses power and draining the battery)

I can not disconnect GND from inveter.
I can not disconnect POS from relays.

Is there a "easy" solution to this??

The relay is connected to +12V and one output pin on the ULN. The ralay gets some "creepage" current from the ULN, enough to energize the relay. Happens when inverter is off, but other devices are on (like charging)

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to make a jumper with MOSFET?

texts:
I have a PCB where two signals can be connected with a jumper. These two signals are neither GND nor VCC.

The problem is that switching between the unconnected and connected mode requires a user intervention (ie. setting the jumper or removing it). I would like to replace this "mecanical" switch with an electronical switch. I was thinking of using MOSFET controlled by a microcontroller.

Is it possible ? Is there a simple schematic to do this ?

Thanks. :)


texts: I made a triple PWM motor controller with a 555 timer hooked up to 3 IRF621 MOSFETS to the motors. I am having interference troubles. When I turn one knob up, the other motor wants to change speed a small amount, and it is not stable. I added a 47pf capacitor from pin 5 to ground on each, but that didn't seem to help. Is there a way around this, or is that just how the 555 timer is? Here is the schematic I made (yes I know it is a very bad schematic).


texts: Sensor buffer with minimal component count

texts:
Intro

I have an automotive-type Hall sensor that is slowly failing and want to squeeze a bit more life out of it, since it's costly and not readily available. Not a critical part.

Original design

The sensor I assume is a Hall transistor-type arrangement - it takes 12V supply, a 6V pulled-up signal line and ground. On detection, it pulls the 6V to ground.
I've measured the short-circuit current on the signal line to be 20mA.

The "computer" on the other side reads the low signal and can work with a bit of headroom, but I assume it needs to be down to at least 2-3V in order for the signal to register reliably.

Goal

I want to design a very simple circuit that raises the input impedance on the sensor side and provides a low impedance (>20mA) on the "computer" side. That is, the circuit should provide a 6V (Vcc/2) signal line with about 10k of impedance, and when that voltage falls below 5V (~Vcc/2.5) it should drive the output side low as well.
Inverted should also be fine, as far as I can tell.

Ideas

I already had an LM324 window comparator built before I knew how the circuit actually behaves. However I don't like the fact that it feeds 12V on the signal line, computer side. I could add a diode to allow only pull-down, or set the Vcc to 6V for the LM324, but the component count is already high. Also three gates are unused.

I could try a 2N222 common-emitter circuit but from my calculation it seems that the gain is too low. Maybe a Darlington would work?

The last idea, which I would like to avoid, is to just use an ATTiny85 board (have a few of those), reading the ADC through a large resistor, pulling the output line low if it goes below a threshold. This is a minimal part solution since it already has a regulator in place and would only need a diode on the output and a resistor (>25k) on the input. Edit: won't work, the ATTiny will see 6-7V on its output pin.

Edit: I've measured that the sensor can source 4mA to ground, assume it also sinks around that value. Likely the computer can work with 5-10mA (since it works sporadically), but targeting 20mA just to be safe. It needs a pullup.
Can't seem to shake the feeling that this sounds like DTL / TTL.


texts: Does somebody know, what the parts "D1" (top left) and "D2" (bottom left) are? I would think it is a special kind of diode, but I never saw that symbol before in 10+ years of electronics.


texts: How can I create a resistor (rheostat) network adjustable from 10kohm to 1Mohm?

texts:
This is for a part of a system that provides feedback to a voltage reference of 0.6 V. The output voltage has a range of 125 V to 500 V.

Using a voltage divider, 414k and 2k will provide the 0.6 V when the output is 125 V. Similarly a 1664k and the 2k will provide the 0.6 V when the output is 500 V.

In order to control the feedback, I plan on using a resistor network adjustable between the 414k and 1664k for the top resistor. I have split that resistor into a fixed 390k resistor and a 24k - 1274k variable resistor network.

What approach should I take to solve this problem?


texts: What will be the graph of flux of coil 2?

texts: In the following picture current is flowing through coil 1. Let's assume that current is increasing linearly in coil 1. Then emf induced in 2nd coil be will constant and having some negative value. What would be the flux in coil 2? How it could be interpreted in graphs and what's reason behind the behaviour?


texts: Asking for an opinion on By-passing an Op-amp circuit

texts:
Hope you are having a great day, I need to be able to bypass a non- inverting amplifier on my PCB in the future.I am using a header jumper to do this. My question is, should I :
1) short the non inverting input to the output
2) or do the header jumper in parallel to RV4(so that I create a unity gain buffer)

Thanks for the response


texts: Where is Pb (lead) found in an immersion heater?

texts:
Clicking "Technical data" on this page gives a pretty good overview of the composition of immersion heaters: Terminal, End Seal, Cold Pin, Alloy spiral, Sheath, and Insulation.  Having bought a RoadPro immersion heater for my on-the-road needs, I read on the label that it contains lead.  Not sure where, but the other immersion heaters that are sold on Amazon are sourced from China -- meaning that they won't disclose it, even if they also contain lead.
So I decided to buy lead test strips, and test the heater that I buy, to check whether it also has lead.  My question is, which of the above components can contain lead?


texts: Which differential protocol to use when redriving Ethernet?

texts:
I want to redrive a 100-BaseTX signal on a board. The signal is to be redriven 3 times (by the same setup). On one end is a STM32 NUCLEO-F767ZI board, and on the other end is a GbE switch including the Vitesse VSC7429, which has 12 integrated PHYs.
When looking at an application note from Wurth (here), I saw the 2 ways to use Ethernet isolation tranformers : VML and CML. I went on to look at the NUCLEO-F767ZI schematics :

And it seems to be wired in CML mode, according to Wurth's appnote (the transformer's middle point is connected to +3V3). However it doesn't exactly fit what Wurth shows (mostly on the 50 ohms pull ups), which confuses me.
On the other hand, here is Vitesse's Media Interface :

It corresponds to Wurth's VML schematic. I'm not sure the resistors shown inside the PHY are the 50 ohms series resistors, but I'll consider they are.
I went on to look at specialized ICs to redrive Ethernet, but found there are very few with this specific role. On Texas Instruments' DS100BR111A Datasheet, which is in their "Ethernet redrivers" section, it is shown to also be compatible with SATA protocol. The differential in/out pins are shown as "CML", and the layout recommendations indicate the pairs are to be AC-coupled. On another chip, the SN75LVCP600S, the inputs are listed as CML and the outputs as VML. I am so confused.
One important thing about Ethernet is inter-compatibility of devices, so I need to make it look like (to the GbE switch) it's directly interfaced with the Nucleo board, and vice-versa. So I need to reproduce what's happening beyond the magnetics. I think the setup [Magnetics <-> CML/CML repeater <-> Magnetics] should be transparent, but it's very heavy, and I'm looking for the minimal parts count.
Question 1 :
Does it matter ? I couldn't find info on the compatibility between the 2, and most appnotes and datasheets don't even bother with the VML/CML notion.
Question 2 :
Can I use a "simple" CML repeater ? I don't need the 10 Gbps, and would do fine with a smaller pin count.
Note : I am not looking for component suggestions, I've simply included the ones I looked at to illustrate my confusion on the matter.
Edit : Removed question about magnetics and included info about desired design characteristics


texts:
Theoretically, on a 12v with a max of 10w power line, how many LED's could you chain in series before the LEDs further down the chain begin to dim? Where the LEDs have a forward voltage of 3.2 - 3.5 and a forward current of 20mA?

I would be using a 470 ohm 1/2w resistor before the first LED.


texts: Astable Multivibrator - Kalafuna is burning, not switching

texts:
I am having problems with circuit, that I designed.

R1=R2=R3=R4= 680 ohm; C1=C2 = 20nF; R5=R6 = 7,3kohm
Circuit works only when voltage is about 0,5-0,7V and resistors r5/r6 are not connected.
It "should" oscillate at 50Khz.

** R5=R6 Are calculated for hfe=306 measured.
Designed for 20V -> 680 ohm -> U/R -> 20/680 = 0,0294A. Thats what transistor should turn on. With hfe 306 -> 0,0294/306 -> 0,000096 A. Thats minimal current for turn it ON. So to bypass turning second transistor On when capacitor rise 0,7V - resistor is calculated for 20V -> 20/0,000096 = 208kOhms.
With resistors connected, there is no switching and i got nice smell from burning resistor R1 when rising voltage to 20V.


texts: What is meant by "capacitors try to try to maintain voltage at a constant level"

texts:
I'm trying to self learn electronics and to that end have been studying capacitors and I came across the following

  A capacitor’s ability to store energy as a function of voltage
  (potential difference between the two leads) results in a tendency to
  try to maintain voltage at a constant level. In other words,
  capacitors tend to resist changes in voltage drop. When voltage across
  a capacitor is increased or decreased, the capacitor ”resists” the
  change by drawing current from or supplying current to the source of
  the voltage change, in opposition to the change

I can't understand the wording here, so if anyone can answer the following questions I'll be really grateful.

Does this resisting to the voltage happen while charging or only
after capacitor been fully charged?
What exactly happens if the voltage drops in the source
What exactly happens if the voltage increased in the source.

EDIT
Let me see if i got this correct.
Lets say a capacitor is connected to a 5v source in series where the capacitor and the voltage source are ideal

the capacitor starts charging up and the voltage across it increases
the current through the capacitor increases as the voltage across it
increases
when voltage across the capacitor reaches 5v the current stop
flowing through the capacitor
if the voltage of the source drops to 4V, then capacitor will
discharge some current opposite the current flow from the source
this will reduce the net current flowing through the capacitor and
thus reducing the voltage across it to 4V.
after the voltage across the capacitor reaches 4v current again will
stop flowing through the capacitor
now if the voltage of the source increases to 7V the capacitor will
start to charge again and current flowing through the circuit will
increase.
when the voltage across the capacitor  reached 7V then current will
again stop flowing

is my understanding correct? if so does that mean that a ideal capacitor can charge it self upto infinity or is there a max limit


texts:
I'm working with ICL7650S(online datasheet). Today, when I was working with the Op-Amp, I came across to an odd thing. this is my circuit:

simulate this circuit – Schematic created using CircuitLab

Note that 22uF is for reducing the supply osilation(this question might help you that why I put this cap. also at first I used 100nF and it was getting better and when I changed it to 22uF, the output just 10mv increased(a bit better than earlier)).

The problem is that the Gain isn't correct and especially when I reduce the input, the Gain is going to be reduced(due to the input). for example look at this table:

This table is an example of my measurements(from above circuit). the gain for this circuit should be (357/1.033)+1=346.59

The question is Why the Gain is reducing due to the input?

P.S. A not-completely relevant question. How can I smooth the output of my switching supply as possible as?


texts:
I have a simple setup where an Arduino Mega + Raspberry Pi 4 are connected via regular USB cable.

They are also using a shared 5V@5A power supply which provides more than enough power for the 2 devices.

Both of them getting the 5V directly from their VIN pins skipping any kind of voltage regulators on board.

The problem comes when I disconnect the Raspberry Pi now from the 5V line while the Arduino is still running and try to plug it back in. It never boots with only the RED led lighting and the green HDD led never lights up UNTIL removing the USB connection between the 2.

After that it happily boots up and I can plug back the USB.

What is causing it and how to solve it the simplest way with the current setup?

Would adding a diode on the Raspberry Pi VINs help anything? I assume there is some back current loop going on here.


texts: taking long exposure image with CCD sensor

texts:
Assuming you use a CCD image sensor, would it be possible for you to take images with exposure time of 1s without stacking image?

I'm wondering how you can decrease data rate of the CCD. CCD camera has ADC   and ADC has its own clock frequency. Let's assume that the clock frequency of your ADC is 20Mhz and its bitdepth is 10-bits . Then it outputs 10-bits data every 50ns. Therefore during 1s you would have lots of meaningless data. So in order to take long exposure image, you always need to process data(remove meaningless data) and stack images. Could anyone please let me know if I'm correct?


texts:
I just had a problem with some lines coming from a PIC IO bank, and going into the base of a transistor (BC635) at some high speed.

Without any base protection (since the PIC can't provide enough current to damage the transistors) I start experiencing some synchronization issues, with some not being turned off before the next turn on.

After putting some 100Ω in series, the synchronization issues disappear.

Why?
Should all high-speed data lines have some resistance? If so, how much?


texts: Handling of complementary errors in embedded software

texts:
I've to design a firmware for an embedded device which may be in different error conditions at the same time. Each error condition requires to set the hardware components of the system into different states. Means every error condition requires a dedicated transition callback function for entering the error sub-state or a dedicated "in state" logic which is executed simultaneously with potential other error sub-state logic. In addition the states of the HW system components may be conflicting in different error conditions. Means there is need for prioritization to resolve potential conflicts between "safe states" for different error conditions. Each error condition shall be acknowledge-able. Means each error sub-state requires explicit transition callback function for leaving the error sub-state.
How should I model this design using e.g. an UML state diagram?
BTW: I've designed UML state diagrams before. However I never had to deal with that kind of requiremenst before. In my opinion the requirements cannot be abstracted in an "off the shelf" state machine design like I used before. The question is not about UML state diagrams but the given requirements.


texts: How to switch 7 wires with a single on/off slide switch

texts:
I am working on a project, where I want to build a raspberry pi into a nintendo 64 console, and be able to switch between with a single switch. By that I mean, I want to be able to use a single slide switch to either switch on the raspberry, or the n64.

I already figured the most stuff out, but I need help with wiring the controller port.

I have a n64 to USB controller adapter, which is connected to the raspberry. Each controller has 3 pins, VIN, GND and Data. I have 2 ports I need to switch. I also need to switch the usb Power for the raspberry.

So, I need a single switch, which has 2 states (ON, OFF), to switch the n64 controller ports to either the n64 console, or to my USB adapter. It also needs to switch the 2 wire power for the raspberry. I made some pictures to visualize it better:

So here is how it should be for to work with the regular N64. The controller ports are wired to the n64 console, and the raspberry power is not connected.

Then, when you switch it over to work with the raspberry, the n64 controller ports should go to the USB adapter, and the raspberry power is connected.

Now, my problem is I don't know how to achieve that. I know there are slide switches with enough pins, but they have multiple possibilities, not only two.

I also need something small, since the n64 case is small and doesn't have a lot of space.

Any ideas?


texts: In order to obtain Power-Voltage characteristic of domestic loads (coffeemaker, microwave oven etc) I need to measure consumed active and reactive power at vooltage range U=[0.9-1.1]Un. Is there universl technique for such measurenemts? I'm a bit confused at the moment, because the loads should be live during the measurenemt, but where do I connect the mesurement circuit?


texts:
I want to charge an 100AH battery with a UPS of 220V Ac input and output. On the back of the UPS there are not enough information provided regarding how much ampheres it provide for charging the battery however it has 1250VA written on the back side. In my desired setup, I will have the following,

An 100AH battery connected with my 1250VA UPS whereas the UPS will only charge the battery I.e will not provide any AC output (a spare UPS that I want to use as a charger only, instead of purchasing a new charger). I will connect a DC fan to the battery in this setup whose power is 48-50 watts. The UPS as a charger will be supplying charge almost 10 hours a day as there is at least 14 hours electric power cut-off in our area.
I need to know below:
1. Is the UPS power capacity OK for the battery I.e it will not damage my 100 ah battery.
2. For 10 hours daily the UPS will have electric power to charge the battery and during when it is charging I may be using my DC fan connected with to the battery, will it work without getting damaged ?


texts: Difficulty understanding data over opto-diac

texts:
I'm having difficulty understanding the data over MOC3021, DIAC side.
Should I see it as with DB3? So DB3's \$V_{bo}\$ (28-36V) is the same in opto-diac, and DB3's \$V_o\$ (min 5V) is the same as MOC3021 \$V_{tm}\$ (typ 1.8V max 3V) and DB3's \$I_{trm}\$ (2A) is MOC3021's \$I_{tsm}\$ (1A), all calculated from \$P_d\$ max for MOC3021:

$$ {300\text{mW}\over1\text{A}} = 300\text{mV}$$

although max 3V why

$$ 300\text{mW} \times 3\text{V} = 900\text{mA}$$

or

$$300\text{mW} \times 1.8V = 540\text{mA}$$

?


texts: synchronous rectifier control chips for half-bridge

texts: I'm looking for synchronous rectifier control chips for use in a boost converter, but all the chips I've seen so far sit behind transformers in the application circuits (for example, as shown here: TEA1795T datasheet). Are there synchronous rectifier control chips that can be used without isolation?


texts: Is electricity wasted when energy generated by power plant is not in immediate demand?

texts:
After my second series physics course I have begin to wonder how power plants control energy production to match the usage of a city.

There are several possible answers in my mind listed below:

Does it always over-produce the amount of energy that a city needs so that a certain amount of electricity is wasted?
Does it over-produce the amount of energy but stores the excess energy in molten salt, or pumping water?
Does it match exactly the current energy need?

The reason that this question has come to my mind is that if option 1 or 3 is true, then solar power and wind power is completely useless, as the generated energy must be used immediately, but I have to list as an option as I often don't see dams or molten salt reservoir around solar and wind power generators.


texts:
Can someone from their experience share part number for equipment for low current measurement. The current to be measured is less than 6nA.
I am aware that I can connect a resistor and by measuring the voltage drop across the resistor, I can calculate the current.
Is there any equipment in the market which can measure such low current?
Awaiting for your kind reply!


texts: netduino plus 2 compatible gps/gsm module

texts:
I have a netduino plus 2 board and I am trying to send gps location with gprs to my server.I am a java programmer by profession,but recently I got interested in IoT and m2m communications.I would like to know if I can use the below shield for the netduino plus 2 , though its mentioned for arduino.I just want to make sure I purchase the right parts.Or if anyone could suggest me the right parts to purchase for my gps+gsm tracking project.

here is the shield which I found that has gps & gsm.

http://www.dfrobot.com/wiki/index.php/GPS/GPRS/GSM_Module_V3.0_(SKU:TEL0051)


texts: How to turn off a circuit with a ON/OFF switch

texts: I`m designing a circuit and I want to turn it on and off. I have two linear regulator and a step-up switch regulator in it. If I use a switch that connects the input pin of the regulator to the battery positive pole or open it, do I have a ON/OFF button or can I have malfunction doing so?


texts: Zener diode BZX55C3V3 does not behave as Zener diode

texts:
I have bought a couple of BZX55C3V3 diodes to protect the ADC inputs of the microconroller but I noticed they all behave strange (and each one in a different way). This is a ST 3V3 diode (http://www-3.unipv.it/lde/strumentazione_componentistica/datasheet/ZenerBZX55C33.pdf).

The test connection is simple:
Vcc -> 1kOhm resistor -> cathode -|<|- anode -> GND.

I measure the voltage drop (Vd) on the diode and it is the following:

Vcc Vd
1V  1.00V
2V  2.00V
3V  2.55V
4V  2.85V
5V  3.05V
6V  3.20V
7V  3.30V
8V  3.40V
9V  3.45V
....
15V 3.70V
...
20V 3.85V
...
30V 4.00V

When it is positively polarized (anode +, cathode -) the voltage drop is more less 0.65-0.8V (between 1V and 30V), which looks ok.

What might be wrong with these diodes? The problem is that in my local shop the only 3V3 Zener diodes are exacly BZX55C3V3 and I have no idea whether this specific model is that poor or maybe all my diodes come from a failed batch.


texts: I have a question about this circuit. How do I get the transfer function of a circuit with a diode? The current through diode is $$I_d = e^{U_d/5} -1$$


texts: How are microchip transistors different from larger transistors?

texts:
I've watched several programs which explain the fabrication of microchips essentially similar to developing film to the layperson. There is a silicon wafer, a special designed mask, and then light is used to "burn" the design into the silicon wafer in a multi-step process. One of the most modern ways to do this is called Extreme Ultraviolet Lithography.

Frankly, I understand the concept quite well. What I don't understand is how the burned-in result on the wafer includes a bunch of tiny electrical components which actually do something when potential differences are applied. If I search the Web for "transistor" images, I get a quite familiar electrical component with leads that could be plugged into a breadboard, for example.

My question is, what makes a "standard" transistor like one you may find in an electronics store in a bag, different from these etchings and how do we go from burning a pocket into a wafer to a functioning electronics component like a transistor? Additionally, what types of electrical differences may we see in a transistor used in a microchip vs a traditional, visible-to-the-eye transistor? If the answer to this question is too complicated to summarize here, some references would be appreciated.


texts: Question about voltage ratings on constant current LED Drivers

texts:
I have a 50W LED chip, 28-32V, 1400mA max current.

I'm looking at a 60W, 1400mA constant current LED Driver but it's output voltage is rated 25V to 43V.

Will this driver work as is, or do I need to limit the voltage of the output so it falls within the LED's range?


texts: Simplest Way to Connect an Arduino to Android (Wirelessly)?

texts:
I want to control a simple Light on an Arduino from my Android. The Arduino I have down pat, no problem. However without using Bluetooth on my Android, whats the simplest way to actually connect it (or use some sort of app) to control an LED.

I have Option A: Set up a Server on my Arduino, with a website that allows me to click on buttons or something to change lighting options.

or Option B: Sending Serial Data from my Android to my Arduino Wirelessly?

Which would probably be the easier option? Is option A even viable or not really? I don't really know the "hosting" capabilities of an Arduino, but if the Arduino is on the same Wi-Fi as the Android phone I'm using, it shouldn't have any issues receiving information (from clicking on buttons on the Arduino "webpage" correct?)


texts:
I just finished working on my 4x4x4 LED cube. I am trying to write an animation for a bouncing ball in the cube. Basically, a ball either 1 LED big, or 2x2 LEDs big should be moving around within the boundary of the cube. The ball should correctly bounce off the edges and continue travelling till it hits another edge. It will be like an object bouncing off surfaces in a vacuum.

I am not able to work out the algorithm to achieve this. What is the logic for simulating this ?


texts:
I bought 10 Thomas Watt LED bulbs and 8 are dead in less than a year (each last about 2-3 months). Soometimes a couple of days before they stop working, they flicker when I switch them on or after they are warm.

I have open some of the bulbs and for some of them, I saw a little black dot on one or two LEDs. I removed the LEDs and solder the connections (cf the picture). After this repair, the LED bulb works for a while and then stop working again.

On a forum someone having similar LED light bulb wrote that the LEDs get twice the current that they are supposed to get. Is this my problem? How can I solve this?

On the "SMD side" of the PCB:
- DB1 (right) is a brigde rectifier (MB10F)
- DS1 (top left) is apparently a Fast / Ultrafast Diode (ES1J)
- the resistor: RS1 (1045)= 10.1mΩ, RS2 and 3 (4870) = 487Ω, RS4(514) = 510kΩ

On the "DIP side" of the PCB:
- U1= 51LP F45


texts: Consider an asynchronous FIFO interface (e.g. FT245, FT2232H or comparable). Since there is no clock, how do you decide who deserved to be called master? Or do you call it controller instead?


texts: When a pin needs to stay LOW or HIGH, is it okay to connect directly to VCC or GND?

texts: For example, I'm using an Exar Exar SP3220EBCY-L RS-232 transceiver and the typical application loop back test shows that the EN pin is connected to GND and the SHDN pin is connected to VCC.  Should I take this literally or am I suppose to assume that I'll need a pull-up/pull-down resistor?


texts: Car battery terminal sensor alternative?

texts:
I recently tried to replace a car battery, and on it was connected a negative terminal (ground) battery sensor which had a few sensitive corroded bolts that accidentally split. The 2 cables for ground and sensor ground connect perpendicularly on opposing sides of the terminal. The part which connects the sensor cable is insulated with what i'm assuming is some sort of plastic. This part is fairly expensive compared to a typical universal car battery terminal because of this sensor isolation. Here is a picture of it. One connection is on the bottom left with two cables, green and white. Top part is the sensor connection with a metallic plate and hole over the bolt.

Here is a universal car battery terminal.

People who have tried messing with this without the isolated ground ended up getting the light inside the dashboard which says there is something faulty with the battery and in some cases, it doesn't get a readout for the voltage level etc. So they took the universal battery terminal and did a somewhat similar thing as in the 1st image and put a large plastic piece over the top and a bigger bolt which connects to the sensor plate and touches the plastic. Is this enough for a normal car operation or should i just the more expensive battery terminal instead? Let me know if there's alternative for this type of connector


texts: How is a simple push button implemented in professional grade electronics

texts:
I just want to ask how is one of the basic components of electronics a push button implemented in professional grade equipment?

The most basic of a tactile switch circuit might look like this:

This itself is good enough in theory, but we know that in practice we will encounter some problems; such as switch bounce. It can solved by adding capacitors on the switches, adding a delay in your code and checks again if it was a valid press, or doing both. This solution is simple and easy to do, and is the go to of almost everyone doing DIY.

Now for my question, how do big companies where a button not registering could mean bad PR for their products and their brand. Examples of what I mean are, iPhone's (or other phone brands) home and volume button (6 plus and older on iPhones), keyboards, mice, arcade games, etc.

Here are some of specific questions on my mind:

on high end keyboards that has "anti ghosting", how did they implement this anti ghosting feature? Is this done in hardware or software or both? Are they still using a matrix of buttons to save some space on the keyboard chip?
Is there an IC for buttons that handles everything (or most), pull down/ups, capacitors, multiple button press, or some other feature, that just send a very clean signal to your controller chip/computer?
In software what are best practices in registering a button press, rising/falling edge, the classic approach, interrupts?


texts: Place decoupling capacitor before or after the reverse voltage protection diode?

texts: I want to add a reverse voltage protection diode (i'm using the 1N4001) to protect my robot from silly mistakes when connecting the battery terminals. But i also want to add a decoupling capacitor at the power supply. So, which setup should i use, A or B? And, why?


texts: Ge Diodes have been used for AM detection many decades before Si Diodes became cheap.They were attractive when compared to the large power hungry valve .Nowdays Si diodes are much cheaper and easier to find than Ge diodes,so they are commonly used for detector service .The old school point contact Ge diode has low capacitance ,low foward drop and more gradual VI characteristics which should give low distortion.I have seen Ge diodes on some high end MW AM tuners .Prebiasing the diodes and keeping the output voltage level reasonably high does result in low distortion .My question is about impedence level .If the impedence is low like say 5K the bulk resistance is significant .This could be why old solid state radios sound bad .If the impedence is too high then the diode leakage currents will at some point muck things up .Remember that leakage is very temp dependant and not linear  .          1 meg which is common for valve stuff sounds much better. Is 1 meg too high for Ge considering leakage issues?                   What impedence would be optimum  ? Would the valve stuff do better with a properly prebiased            Si diode circuit     which has much less leakage?


texts: Unshielded RJ45 connectors on SFTP Cat5e

texts:
I have "inherited" an old SFTP Cat5e cable connecting the basement of my house to the upper floor. There seems to be a break on some of the wires (6 and 7) so it won't even function at 100mbps.

I think the breaks may be in the connectors themselves, as they appear to have been crimped very (very!) poorly. In fact, the shield doesn't seem to be connected to the connector at all at one end!

I don't really want to rerun this cable (for a start I have no idea where it actually goes once it leaves the basement) and I would like to recrimp both ends of the cable to see if it's just the connectors or if there is a break in the wires inside the cable. I only have ordinary Cat5e connectors handy.

I'm guessing that the entire run is less than 40m and that there was no actual reason to use SFTP vs UTP in this case. There don't seem to be any sources of major interference nearby so I can't imagine why the more costly SFTP was used in the first place.

Will replacing the existing shielded connectors on the cable cause any problems? Obviously the shielding won't be grounded - but it doesn't seem to be at the moment anyway - and I've heard that an ungrounded shield is worse than unshielded because of the "antenna" effect, but this page seems to contradict that:

http://www.siemon.co.uk/us/standards/Screened_and_Shielded_Guide_7_Antenna_Myth.asp

Will ordinary unshielded RJ45 connectors be OK, or at least not much worse?

Thanks.


texts: How can a transformer convert the voltage of the same wire before and after connection?

texts:
Today I discovered a very strange thing, this transformer in the picture below, has 3 phases as input, and the output varies as you can see in the picture, the weird thing is that when I measure the voltage across every two phases before connecting them to the transformer I get 380v, but when I do so after connecting them, I get different values, the very same wire goes from high voltage to 0 voltage, is this correct? I couldn't believe it until I touched the wire and didn't get a shock! How does this work?

simulate this circuit – Schematic created using CircuitLab