texts:
I am not very experienced with relays but I need to control the state of a relay with a PWM signal such that if the microcontroller is damaged and the controlling pin gets stuck in a high or low state the relay will not get power. I am hoping to implement this with passive components only.

In the image below is my circuit with basic control Digital high = relay off and so on.

If I add a capacitor between the microcontroller and the transistor I will filter out DC but now I need the transistor to stay open when a PWM frequency is applied, or the relay to say closed.

I have tried to simulate it and found that adding a parallel resistor and capacitor after the transistor helped, but not enough as seen below.

I have also changed the duty cycle but this has little to no effect.

The red arrow(red simulated output @ 20KHz) refers to the output from the microcontroller and the blue arrow is the output fed into the relay(blue simulated output).

I have played around with the value of these components and this is as low as I can get voltage (the relay will see) to go.

I am also worried that this might put the relay into an unknown state due to this 3V offset.

I have seen other systems, they use the inherent properties of the inductor in the relay when controlling it with a PWM signal but as this is a 16A relay I am hesitant to do that and I don't want contact welding.

Any help or insight to this design problem is appreciated.


texts:
On most hobby Li-ion packs there is a prominently displayed C rating (typically 20 - 35), which tells you how many amps you can draw from it, in a multiple of the capacity.

I have never seen a C rating on a NiMH pack. Neither do you normally see how many amps you can draw from the battery.

What is a typical C rating for a NiMH battery?

Note: I am looking for an estimate, so if it's a range, go ahead and put that. I do not have a particular battery in mind.

EDIT:

I can see that I was misunderstood already by EM Fields. Let me try to clarify. The C rating refers to a constant with units of 1/hours which gives the peak amp draw in terms of the capacity, like this: Capacity [Ah] x C rating [1/h] = Max draw [A]


texts: I am new to biasing calculations and I cannot understand why in a voltage divider bias we can apply the Thevenin Theorem to find the potential in the transistor base. For example, here http://www.learningaboutelectronics.com/Articles/Voltage-divider-bias-of-a-BJT-transistor why is V in the base calculated as if the current though the base is 0?


texts: Switching high voltage battery from series configuration to parallel configuration for charging

texts:
I have a question regarding switching batteries from series to parallel to charge them.

I have 36 modules of 1Sx11P Li-ion batteries connected in series.  During normal operation they drive a car with a high efficiency motor, and are recharged via solar panels and two max power point trackers.

However, when the car is not running off of solar power or is parked in the garage I would like a way to charge the vehicle with a battery charger or power supply with a cable that could plug into the car.  I have been reading some descriptions about people doing similar things for beefy RC airplane batteries by connecting them in parallel and charging many more than the battery charger could originally charge.  Here is an image from this website:http://www.rchelicopterfun.com/parallel-lipo-charging.html

Or other configurations like on this picture

The advantages of parallel charging would be very big for me as it would regulate a lot of the cells voltages without the need for external balancing circuitry, though I do have that available when the car is in serial hookup.

The batteries aren't all that accessible in the car either, so plugging in two different harnesses isn't really option for this idea.

What I want to know is, is their a way I can implement a circuit that can flip back and forth between series and parallel for the batteries that could handle the high voltage and large currents I would be dealing with?  Do you have any recommendations on how many batteries I should look into having in parallel while charging?

I would appreciate some insight as this is a little out of my typical realm of electronics.


texts: I have a 200 watt 12 volt solar panel. It has 3 diodes mounted on the back. Can you take the diodes out and the panel still operate normally in the day time?


texts: Will 5W power on TIP41C/TIP42C require a heat sink?

texts: I do guess it will require but I have never used a heat sink before, so I am not sure.


texts: Energy Measurement in 3 phase ac split into 3 lines

texts:
I have observed that residential buildings receive 3 phase supply, even though almost all appliances are single phase input type. The phases are split into three separate lines and loads are evenly distributed on all of them. Something like this except the 3 phase motor which has been shown in this image:

Even though the lines are split inside the building, I think that a 3 phase energy meter is installed at the incoming point for energy metering purpose (please correct me if I am wrong).

My question is - If I use 3 X single phase energy meters for all three lines, will it give me the total energy consumed in the building as recorded by the 3-phase meter?

The plan is to measure energy at switchboard level to collect some stats for high energy consumption points. The switchboard will contain single phase appliances like fan, tubelight, CFL light, socket, TV etc. However this will make sense only if energy recorded by main meter is equal to sum of energies recorded by individual switchboards. Ignoring some losses in wiring. 5% accuracy is good enough for me.


texts:
I need your knowledge and experience for a problem I am having.

I am designing an embedded system which is powered by a 3V LiMnO2 battery. The battery operates at 3V and this covers all needs.

Except for a green LED which is best operated at 3-3.3V. As long as the battery is healthy enough, the LED works fine, but overtime and with steeper voltage drops (to 2.85 and such) the brightness of the LED deteriorates and damages the signal.

Do you think using a regulator is needed in this circuit? Or regulating a 3V circuit powered  by a 3V battery for voltage drops of 0.1 is not a good idea?

It is very important for us that the device can work for a very long time (2 years), so the power consumption of the regulator is also very important.

Is it generally worth it? What are my options?


texts:
I recently bought my new macbook pro 2017 model which comes with USB Type-C ports supporting thunderbolt 3 standard with USB 3.1 standard. So since I have lots of devices with USB A type and supporting USB 3.1 standard, thought to buy some adapters. But when I'm shopping to buy them I saw that most companies have claimed that their USB Type C adapters are supporting USB 3.0 standards instead of 3.1 and couldn't find any adapter (which satisfies my needs) supports USB 3.1 standard. I was kinda confused now and have to problems to solve before buy them.

1) Since my devices supprt USB 3.1 and Macbook supports USB 3.1 standard, will those adapters (which claim to work fine with UBS 3.0 ) deliver the speed of USB 3.1?

2) Those companies have claimed that those adapters are working with USB 3.0 standard because USB 3.1 is quite young?


texts: Uncertainity with CIPSEND command to updating the data field on thingspeak using esp8266

texts:
I am having a bit of uncertainty here updating data on thingspeak using their generated API or may be because of the "AT+CIPSEND" command. Below are steps I followed for the 1st trial:

AT+RST

OK
B1���:6�;�;!G��R��A#�
[System Ready, Vendor:www.ai-thinker.com]
AT+CWMODE?

+CWMODE:1

OK
AT+CIPMUX=1

OK
AT+CIPSTART=0,"TCP","api.thingspeak.com",80

OK
Linked
AT+CIPSEND=0,85

> GET https://api.thingspeak.com/update?api_key=1VMOGPWM9SGJXI5C&field1=77

OK
Unlink

I have been following Kevin Darrah's tutorial Here. When tried the above, the data field does not update.So, 1st trial failed!!!.

But, when I did the below by changing the length of bytes assigned to CIPSEND command with 76, surprisingly the data was updated on thingspeak.

AT+RST

 OK
 �6B�=Cl��1�� �A#�+�A��
 [System Ready, Vendor:www.ai-thinker.com]
 AT+CWMODE?

+CWMODE:1

OK
AT+CIPMUX=1

OK
AT+CIPSTART=4,"TCP","api.thingspeak.com",80

OK
Linked
AT+CIPSEND=4,76

> GET https://api.thingspeak.com/update?api_key=U6PE1HI433A8XPQY&field1=77

SEND OK

+IPD,4,1:1
OK

OK
Unlink

So, the 2nd trial worked!!!.

Again, I did a third trial and this time I changed the length of bytes assigned to the CIPSEND command to 100 as shown below:

 AT+CIPSTART=4,"TCP","api.thingspeak.com",80

 OK
 Linked
 AT+CIPSEND=4,100

> GET https://api.thingspeak.com/update?api_key=U6PE1HI433A8XPQY&field1=46

OK
Unlink

The only difference between the 3 trials is the length of bytes to send, assigned using "AT+CIPSEND". And the data is posted to thingspeak successfully only when the length of bytes is assigned as 76, but did not work when assigned with 85 and 100.I am using Arduino IDE's serial monitor to send these commands with NL&CR enabled.My question is,

Why is it working when CIPSEND is assigned with value of 76 and not for 85 and 100


texts: Are overdamped rise waveforms really "curvier"? Or is that just time scale?

texts:
Do the rising waveforms for overdamped circuits of different \$\zeta >= 1\$ actually have a different "curviness"? Or does it just look that way because they're all shown on the same time scale?

You know, how you can get any square wave to look like any one of these by adjusting the horizontal scale on the scope. I'm wondering if they actually have more rounded shapes as the damping factor increases or whether they're all exponentials with a different time constant or something and you could overlay one on top of the other if you had a "fine" mode on your scope horizontal controls.

The reason I'm asking is I had the preconception that a waveform for a damping factor of 1.0 was going to be better (like straighter until you got to the top) than one for say 2.0, even if they both exhibited the same rise time. So I was thinking I would have to get my pole placement just right to get about 75° phase shift at exactly the crossover frequency, even if I could have say 85° at crossover without careful tuning.


texts: Highish current constant current source design?

texts:
I need a design for a constant current source that can deliver a hefty current at around 12 volts with at least 1-2 amps, preferably up to 5. Every current source I've seen uses BJTs or resistors that are submitted to the same current as the load, but I don't want to dish out the money for a 100w resistor or BJT.

I'd like to avoid an LM317, though I'll do it if it's the best option. Is there a good constant current source design that can deliver 12v @ 2-5A using, say, op-amps or mosfets?

The output doesn't need to be perfectly stable, I just want to prevent any components (namely electrolytic caps) from blowing up.

Thanks for any help


texts: ATX power supply front-end: How does this work?

texts:
I've been trying to educate myself on general power supply operation and stumbled across several schematics for ATX power supplies. In general I understand how a SMPS operates, and an ATX PS is just one example.    However, in reference to the following schematic, I am totally stumped on several fronts:

And enlarged:

Why is the primary of T1 fed off the un-rectified input 'AC2'? Why should it not be connected to the + output from the bridge rectifier?   From what I've seen on other SMPS, the primary side on the main switching transformer is fed by a DC source and switched on/off at several kHz usually by a low side power NFET.
I also don't understand the point of coupling the un-rectified AC line signal (through ZNR1) into the center point of the filter network formed by C1/C2/R2/R3
How can any current flow in T1's primary at all?   Cap C9 blocks all DC on T1's primary.
I understand T2 is an isolation transformer;    Q6 and Q5 run off the PWM from the controller, and by way of T2 provide current to turn driver transistors Q3 and Q4 on and off.   What I don't understand is what's happening as a whole on T2's secondary:  Is the pin #10 a center tap?   An off-center tap?  Why not just have one NPN turning the current through T1's primary on and off?   Why is pin 5 connected to the lower half of T1's primary?

I understand I am lacking some basic knowledge here about how this works, so if you may be so kind please direct me to books or other tutorials on what is happening here.  Thanks!


texts:
Thanks to the help of a few of the other guys I have my AC to DC rectifier working, and the rest of the power supply working.

Now while testing the power supply, my 18V AC transformer gets rectified and put into my circuit below

And I end up with 1.3-26V DC output selectable via the pot R2.

Now while running this @12V with a LED strip light, running about 600mA my heat sink got quite hot. Not hot enough to cause the thermal protection in the LM317 to cut in but hot enough to get me thinking.

Power dissipated = (Vin - Vout)*Il = (26 - 12)*0.6 = 8.4W

My heat sink is rated at 11 C/W and I pasted the LM317(TO-220) on.

Max C/W is = (MaxRunningTemp - ambientTemp) / power = (60-25)/8.4 = 4.2 C/W

Does that sound right, never done any heat sink calculations before. So I would need a heat sink rated at <4.2 C/W

I would not see my self running this over 500mA again but running this circuit at 5V would change a lot? The power dissipated would be 42W if 5V @ 500mA. What can I do to prevent needing a HUGE heatsink? and are my calculations above correct?


texts: How practical are these land patterns for connecting components in a SMPS?

texts:
Was reading this app note from Linear Technology: PCB Layout Considerations for Non-Isolated Switching Power Supplies and on page 7, there is the following image.

Are the desired connections practical?

Are thermal reliefs only necessary if there is an uneven distribution of copper (a trace on one side and a polygon on the side side) or are thermal reliefs necessary for any "large" body of copper?

If I use the desired connections in my layout, would I have any assembly problems (assuming everything else is fine)?


texts: How to remove leakage current from nRES transistor switch?

texts:
I have this AVR reset pin design, which provide a 12V into the nRESET pin of an ATtiny μC. It's function can be describes as follows.

(a) An input signal given by a "low" (0) on J2-1 lets a current flow through LED to show it is "ON", while at the same time pulling the T1 base "low", thus effectively removing T1 from circuit and providing 12V from battery into nRESET.

However,

(b) An input signal given by a "high" (1) on J2-1 would turn "OFF" the LED, while at the same time pulling the T1 base "high", enabling T1 and feeding 12V to GND via R1 (1K) and pulling nRESET "low".

Here is the schematic.

What is the problem?
Battery drainage of 12 mA, when the nRESET signal is not needed, or signal input or power is not connected.

How can I improve the circuit to not drain the battery when the reset signal is not needed/used?
(Preferably with minimal number of added components and using cheap off-the-shelf ones.)

BTW. Is there still a Voltage drop when 12V is not grounded?

References:
I've also looked at a few similar posts and solutions using MOSFETs, but they are either not helpful or I don't understand them, as I'm not clear how to apply the differences, and how to understand the many variations of the MOSFETs available.

BC547/BC548 with 5V at base can't control 12V at collector-emitter?
What is the conventional circuit to control a P-MOSFET with MCU?
N-Channel MOSFET as on-off switch between battery and load
How to shorten fall time on high-side BJT drive?
Avoid leakage current
Transistor weak current when switched from microcontroller

Some additional assumptions:

No significant load on nRESET
Some (internal?) pull-up/down R may be present on nRESET side
12V Battery may be replaced by ~12V DC source
HVSP_ON signal may be 5V or 3.3V

UPDATE-1:
Since I was told that the type of circuit to search for is called a High-Side Driver, I now see these everywhere, with thousands of variations. I choose to accept Turbo's answer because his diagram provide a very nice flow of higher voltages to GND from top to bottom, and signal flow from left to right.

UPDATE-2:
I tried the Tubo's circuit in LTspice, but there seem to be a problem with the MOSFET never shutting down 12V. I tried several different components. Any ideas why this doesn't work?

Where:
Green - nRESET
Blue - V1
Red - Q1:B

UPDATE-3:
Added a load resistance R3 via GND to \$\overline{RESET}\$, so now it works.


texts: What is a bipolar capacitor and when is it used?

texts:
I am studying the schematic for a reactive load box - a device which can be plugged into a guitar amplifier instead of a speaker, on the website http://www.aikenamps.com/index.php/designing-a-reactive-speaker-load-emulator .

The circuits uses a 'bipolar' capacitor - a component i have previously not heard of.  I am familiar with parallel-plate capacitors and electrolytic capacitors, and the physics of them both but the mention of a bipolar cap has confused me.  There are debates online about creating a cap from two bipolar caps connected head to head, but there doesn't seem to be much on the component itself.

What is it
What notable uses does it have?

Thanks


texts: I'm in the process of learning how USB works. What is a USB transceiver and how is it different from the PHY logic of a host controller?


texts:
Is it possible to run both USB Host and USB Device controllers on top of an AVR (ATMega64)?
Specifically, what I'm looking for is to receive data from a usb keyboard, and simultaneously sending keystrokes to a PC.

From what I've seen, both VUSB & LUFA stacks support USB host modes, but they work with a single usb port only.

Any help is appreciated!
Thanks!


texts: It would be very handy for me to have an XLR plug with an LED on the end to check for DC at the output of balanced audio gear. The challenge is two fold. First is that this gear can fail with a positive or a negative voltage on it's output pins 2 and 3 in reference to pin 1. I am using regular old red LED's. Second challenge is I would like to check pins 2 and 3 with a single LED. This brings up the issue of what happens when pin 2 is +VDC and pin 3 is -VDC, it will not light. I feel that a diode OR arrangement might get me close to the functionality I'm after but my design experience falters here.


texts: Why I can't issue commands after CMD8 to an SDHC card in SPI mode?

texts:
I am using the following sequence of commands at 250 kHz SPI to initialize SD cards:

(1 ms wait, then 80 clocks)
CMD0 with argument 0x00000000
CMD59 with argument 0x00000001 (turn on CRC checking)
CMD8 with argument 0x000001AA
CMD55 with argument 0x00000000 (prefix for ACMD)
ACMD41 with argument 0x40000000 (HCS bit set)

Of course repeating the CMD55-ACMD41 until getting out of Idle state. The CRCs are correct (they are calculated with the appropriate algorithm). Chip Select is released after every command (including between CMD55 and ACMD41) with eight trailing clocks.

This sequence works fine for three SDSC cards I have; I can read data from them after the completion of the initialization. However, the two SDHC cards I have fail with it.

They both progress properly until CMD55 (including experiencing a 0x01 R1 response from CMD8), then to CMD55 they react the following manner:

Maxell X Series SDHC Class 4 8 GB (S708G1249 TP2T0M2B49059): No R1 even after receiving 256 0xFF stuff bytes.
PQI SDHC Class 4 4 GB (BH1013316030G): 0xC2 comes after 5 0xFF stuff bytes, which has bit 7 set (an R1 shouldn't have this bit set), otherwise it doesn't even have bit 0 set (Idle) as it should be.

Issuing ACMD41 after this on either card results in an R1 of 0x05 (Illegal command + Idle). Now what? I didn't try to initialize them with CMD1 yet (but as they are SDHC, they shouldn't react to that).

(Both cards operate normally when accessed by a PC or in a digital camera I have.)

I tried issuing other commands; they also fail in this manner. So it rather seems like after CMD8 the card somehow became totally inaccessible despite the valid R1.


texts:
I wrote a simple code to blink an LED connected to PA3 on the STM32F4 Discovery board every 1sec using timer4.  I haven't declared any of the swd pins of the board for gpio, yet I get the following error" Target not connected" Why is it so?
Are there any lines in the code causing this issue?

#include "stm32f4xx_hal.h"
#include "stm32f4xx.h"
#include "stm32f407xx.h"
#include "stdint.h"
#include "string.h"
#include "stm32f4xx_hal_rcc.h"

//NVIC_EnableIRQ(UART4_IRQn); // Enable IRQ for UART4 in NVIC
    void Timer_init()
    {
        RCC->APB1ENR|=(1UL<<2); //TIM4 connected to APB1, hence enable clk though this register
        RCC->AHB1ENR |= 1;  //clock to GPIOA
        TIM4->PSC=42000;// 42MHZ/42000=1KHZ, 1millisec between two ticks
        TIM4->ARR=1000;//count will increment for every one sec
        //TIM4->DIER|=0X0001;//update interupt enable;
        TIM4->CR1=0X0000;//UPCOUNTER;
        GPIOA->MODER=0X00000040;
        GPIOA->OSPEEDR=0X00000040;
        TIM4->CR1|=0x0001;// enable counter
    }

//#########################Clock Configuration#################
void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

  /* Enable Power Control clock */
  __HAL_RCC_PWR_CLK_ENABLE();

  /* The voltage scaling allows optimizing the power consumption when the
     device is clocked below the maximum system frequency (see datasheet). */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /* Enable HSE Oscillator and activate PLL with HSE as source */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 25;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 7;
  HAL_RCC_OscConfig(&RCC_OscInitStruct);

  /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2
     clocks dividers */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_PCLK1 |
                                RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);
}
//########################################################

    int main (void)
        {
      SystemClock_Config();
            Timer_init();
            while(1)
            {
                if(TIM4->SR&0x0001)// CHECK UIF FLAG
                {
                    TIM4->SR&=!(0X0001);//CLEAR UIF FLAG
                    GPIOA->ODR^=(1<<3); //TOGGLE PIN A3
   /* while(!(TIM4->SR&0X0001));
            if((GPIOA->ODR)&(1<<3))
            GPIOA->BSRR=((1<<3)+16);
            else
                GPIOA->BSRR=(1<<3);*/

                }
            }

    }


texts: Is there any schedular that exists for STM32F103 in which the 'tasks' are run at the ISR() level while the Schedular() code runs in the main() thread?


texts: Creating a sketch (.HEX) file from a .PDE file

texts:
I have been using the Ardunio IDE to edit code for an Arduino sketch.

I was having trouble uploading to the board, so I bought a pocket progammer in response to this question: What possible ways can I upload sketches to arduino mega chips?

Now, using this programmer I can upload .hex files via the command line.

Now I want to create a .HEX file from my existing .PDE files.

The problem is:

The graphical IDE has a "Upload Sketch" button (which compiles and attempts to upload in one go), but there doesn't seem to be a "Create Sketch" button.
avr-gcc can create a sketch (I believe) but doesn't recognise .PDE files.

How can I go about creating this Sketch?


texts: What happens if we apply a Gate to Source voltage above that the threshold voltage of the MOSFET

texts:
I have this NVB5860NL Power MOSFET.
In the datasheet, it is given as the Gate Threshold voltage is 3V maximum. But that is for a condition of drain current in microamps.
But, my condition is, I require a continuous drain current of 5A from a 10V source with Gate Source voltage as 10V.
Whether can I use this part? (Mainly asking for the threshold voltage and the maximum drain source voltage)


texts: An overseas company is making a machine for me and they need to know whether I want 1,2 or 3 phase and what voltage

texts:
I'm in Quebec and the company making the machine is in China. The machine is an industrial sized T-Shirt sublimation machine that does two sided printing. So there's a large heated plate that is pneumatically pressed down on to another equally sized heated plate.

It draws up to 4600 Watts.

I can have it made with 1,2 or 3 phase and 220 Volts.

I'm Montreal and will have this set up in a commercial location that I'm going to start looking for this week, but the Chinese factory needs an answer asap.

I'm actually planning on heating only one of the plates so I told them 110 single phase will be fine, then they told me that even if you're only using a single plate with 110 it probably won't be able to hit the full temperature range.

What I'm afraid of is that if I order this thing with 3 Phase 220 it will be an overkill that I don't need that will limit the number of places that I might be able to rent. Or perhaps seriously jack-up my set up costs and time by needing to have 3 Phase installed in a place that doesn't have it.

I checked and the dryer in my home says 'Heater L1-L2 4.5 KW @ 240V ; 3.4 KW @ 208V' and the 4 prong wall socket it's plugged into says '30A 125/250V'. I know 2 Phase doesn't really exist, but this is what the manufacturing company is referring to when they say 2 Phase right?

Since the rating on my dryer would be sufficient to run my machine (I think), and my dryer is on a normal residential circuit, am I right in assuming that if I ask the manufacturer to do it as 2 Phase 220V then I'll have the most options in terms of locations AND be able to run the machine properly?

I need to get this right and I'm totally out of my element. I really appreciate the help. Thank you so much.


texts:
To avoid ground loops I want to isolate several video channels (base-band).
I have a video source with 4 channel, they all share the same ground.

I'm thinking about some transformer like used in audio application with an impedance of 75 ohm. Two issues: I can't find a suitable product, I will lost the DC offset.

Is there a better way?


texts:
I am making this very simple hobby circuit and I need help.

This utilizes the sound (variations) from the device through the jack to provide light (intensity) variations in the LEDs using TIP31.

Hence, the sound is not heard (pretty obvious, I know).

I want to know the additions that can be made to this circuit to enable the music (sound) from the device to be heard AND provide enough to drive the transistor and LEDs.


texts:
This is my first time creating a circuit, so forgive my poor understanding. I am trying to create a simple intercom system with a 9v battery. I have an 8 ohm speaker and a standard microphone:

(source: seeq.com.au)
My circuit looks like this currently
What else is necessary to get this circuit to function.


texts:
What can be the possible DC and Transient analysis for OR gate using CMOS and the threshold voltage like we do for NAND or NOR?
Or what can be the possible calculation to decide the W/L of PMOS and NMOS in designing an OR gate?


texts: Understanding Royer oscillator (for wireless power transfer), (specially mosfet gate driver circuit)

texts:
I need to understand how exactly this circuit works, there is not much references and books on those circuits, they're used as "power" oscillator for DC AC conversion for wireless. i finally found their name after being so downvoted here when i asked if oscillators can be used to generate power.

here is something i found on how it works (i'm not sure you need that to answer my question)

i also know that the mos control voltage is arranged in such a way to perform switching at ZERO BIAS VOLTAGE.
what i really need to understand first is what are the  capacitors C4 and C5 on the gate drive and how are they calculated, also what are the zener diodes for exactly? and i think the shottky is for have a fast turn off right?

here are different other circuits of the royer i found, if this may help, it seems like there are two types,

thank you very much.


texts:
I am planning to use a Right Angle RGB LED EASV3015RGBA0 and here is the package dimension and recommended soldering pad:

Top matches with LED image(see the anode mark). Bottom is consistent with top. However in recommended soldering pattern, for the given LED orientation, I feel that pad sequence should be 4, 3, 2, 1 rather than 1, 2, 3, 4. Or alternatively, the LED will face in opposite direction (180 degrees rotated).

Am I correct or am I missing something here?


texts: Simulate in Puma-EM given radiation pattern

texts:
Is it possible to simulate the EM field in Puma-EM if the radiation pattern is supplied instead of a 3D model of the antenna?

Is there other (free) simulation software that can do this? I need to generate a RadHaz zone ("Radiation Hazard", an isosurface of constant intensity) from a microwave anetenna.


texts:
Objective

I am trying to build a gain-of-1 current controlled current source (current mirror) that is less sensitive to resistor value variation. The designs i have been making are highly resister dependent, as I am using shunt resisters.

Specifications

On the input and output sides, I have 24vdc source
The input side control current is well behaved.
Input and output safe-operating-range must include 4mA-20mA
The load is 500 ohms

Current Approach

This is the circuit I have been playing with. The circuit is very dependent on the 50 ohm resisters.

I have looked at a current mirror, but the matched mosfets I can get only have a VDS of 10V, when given a 24vdc supply, bad things can happen.


texts:
Would anyone share some tips, advices for solving this task?

So far, I have dealt with far simplier electric circuit's tasks. This is new to me. Any kind of help or advices are appreciated, thanks!


texts: Is it safe to plug a computer into itself?

texts:
I have a USB dongle (with microphone and headphone 3.5mm jacks). Is it safe to plug the headphone out into my motherboard microphone/line in?

Would there be any grounding, feedback, impedance problems?

How loud could the USB dongle headphone out volume be without damaging the microphone/line in?

My setup would be: microphone - USB dongle microphone in - computer - USB dongle headphone out - 3.5mm jack extender cable - motherboard microphone/line in

Thank you.


texts: Can a solar panel be used as a Light Dependent Resistor?

texts: I have a small 1.5 volt useless solar panel. Is it possible to have the resistance change between two wires based on the amount of light? And what would the circuit look like?


texts:
Regarding this instructable , why is it possible to build this circuit without transistors?

We have 4 layers of LEDs like that, which is controlled by an Arduino.

Every circle is a LED, the blue arrows are connections to ground (individual pins set to LOW on the arduino when the LED should turn on).

And there's 1 connection to a HIGH pin on each layer with a 100 Ohm resistor.

In total 16 Pins for the ground connections and 4 Pins for each layer (VCC).

This code turns all LEDs on 1 layer on.

////////////////////////////////////////////////////////////turn all on
void turnEverythingOn()
{
  for(int i = 0; i<16; i++)
  {
    digitalWrite(column[i], 0);
  }
  //turning on layers
  for(int i = 0; i<4; i++)
  {
    digitalWrite(layer[i], 1);
  }
}

So when everything is turned on, each layer pin has to drive 16 LEDs, this will result in a higher current load than what the atmega chip on the Arduino can supply. At least this was my original question / concern.

My original understanding was that there are 4 LEDs in series (one vertical red line connecting 4 LEDs) and that each of these 4 lines are in parallel.

As already has been pointed out in the answers / comments, the 16 LEDs are actually in parallel.

The calculation for the resistor was made via 2 V / 0.02 A = 100 Ohm.

Remaining questions:

1) I don't see why all 16 LEDs per layer are in parallel? Is it because they don't share a common ground connection but each one has an individual ground?

If I imagine the red vertical lines (only drew 2) look like this

simulate this circuit – Schematic created using CircuitLab

and you could also draw it like that

simulate this circuit

then I think I understand why all 16 LED are in parallel.

2-ish) The calculation for the 100 Ohm resistor results in:
2V is shared among all LEDs and they have to share the 20 mA provided by the current limiting resistor? This would match passerby's calculation of 1.25 mA per LED. I assume 20 mA was chosen to have enough headroom to the max. current?

The I can understand why we don't need transistors.


texts: What is this component in the picture (brass and plastic)?


texts: Electrically control material to channel light from specific angle

texts:
I am wondering if there is any material that can be electrically controlled
so that light from a specific angle or diretion is received.

Is it possible to manufacture such materials using semi-conductor
manufacturing processes?


texts:
Why manufacturers use GRB(Green, Red, Blue) format for "RGB programmable LEDs" instead classic RGB format?
Eg. IN-PI55TAT RGB LED 4 pin
From the bottom of Page 6 on the datasheet:

Is this choice based on hardware simplicity or with by engineers?


texts:
First, let me say thanks for taking the time to read/help.  I'm fairly new to electronics design, although I have a decent working knowledge (and am not afraid to do the legwork to figure out how something works through my own legwork).  Any help would be greatly appreciated.  I'm not afraid to go do the legwork to suss out a solution, but I need the help of someone seasoned, as even the most basic suggestions will cut down the time dramatically.  Again, thanks for taking the time!

Basically, I have a bill acceptor (takes a variety of monetary notes for payment).  This Bill acceptor is designed to output a "pulse" when a bill is inserted/accepted.  I have the circuit hooked up as the image below, and it's working properly.  I've seen the output pulse on my oscilloscope, when reading between the Credit Pulse(Pos) and Common Ground.

When a bill is inserted, the 5Vdc line pulses on the scope for 250ms.  It falls from 5Vdc to around 4-4.2Vdc.  What I NEED is to cause this line (at the interrupt pin on the Arduino) to read 0Vdc, as the small change in voltage isn't triggering a HIGH/LOW state change at the pin (the Arduino doesn't recognize the pin as being LOW during the pulse cycle).

Any suggestions you have, or direction you might point me in would be very helpful.  I apologize for the rudimentary nature of my schematic, or any faux pas I might have tripped over here.  I've tried to be as detailed as possible.  Thanks again for your time and assistance!

NOTE: I'm actually using an Arduino Uno Rev3 (I didn't have a schematic symbol for it, but found one that would suffice).


texts:
I have a relay operated by an NPN transistor that needs some voltage applied to the base.  I'm working with an arduino and if I give it a digital port, all's well.  The circuit looks like this one:

Now I want to replace the arduino port with a DS2406 (the TO92 kind).

This seemed to get really complicated fast.  My library for operating the 2406 is fine, but I can't figure out how to wire it.

Now that both pieces independently work, my goal is to get some current fed into the base of the transistor so it throws the relay.

I've run into the following issues:

The DS2406 closes to ground.  That's the only option, so I can't map it directly to the base pin of the transistor.

The TO-92 package doesn't have a vcc pin, so I have to have a pull up resistor between vcc and the data pin.  This causes stuff to get hot and smelly when I power it up hooked up to the collector of the transistor with the base wired to the relay power.  I could be using the wrong kind of resistor, but I don't have a strong sense of what's right here.

I may be able to run the relay strictly off the DS2406, but I'm afraid it will have too much draw, which is why I want it to go through the transistor.

What's the easiest way to go from a switch that opens and closes ground to a transistor base that wants current?


texts: When making power polygon , making polygon on the smd-pad has any problems?

texts:
I'm now making 4 layer PCB
and my PCB has one Power plane (L3) and one GND plane (L2).
Now I just make a connection with inner layer (L3) with Top plane(L1).

At this point, I'm curious that what is the best connection for supplying power.

In the picture, Left one is that making polygon on the component's smd pad.
and right one is that first I'm making polygon and routing wires to polygon.

I'm new to 4 layer PCB.
so I want to know what is the common way for this.
I use DC power and this is 3.7 to 4.2 voltage comes from Lithium Battery.
I hope many experts may help me.

Thank you for reading.


texts: Minimum voltage to avoid EEPROM corruption for ATMega328P

texts:
I have a battery powered contraption with an ATMega328P with Arduino code that sleeps most of the time. Occasionally it needs to write some values to EEPROM. It's battery powered so I have tried to minimize the consumption by disabling the BOD, so now I'm curious around what voltage range the EEPROM might become damaged. Has anybody tried to see how low one can lower the voltage and still have it safe?

In the datasheet I see there are options for BOD at 1V8. Does that mean that it would be safe to write EEPROM at 2V?


texts: Positive feedback and virtual short in Operational Amplifiers

texts: Can anyone please explain, with sufficient mathematics, why the virtual short concept is not applicable to an operational amplifier in positive feedback.


texts: Handling register updates in Modbus systems

texts:
I am currently developing a Modbus RTU enabled system that consists of DSP and a microprocessor that handles the Modbus communications. The DSP is sending data to the microprocessor and the microprocessor provides Modbus interface to the DSP results. The results may update at any moment in time (some are updated periodically, and other are updated at random intervals).

If the Modbus host decides to poll a set of registers that correspond to a single data set in several Modbus commands (we had an experience with one Modbus host that could not retrieve more then 32 registers at a time) there is a possibility that the data will be updated in-between the Modbus polls.

Is there any conventional way to handle scenarios like that in Modbus systems?


texts: Is there any pitfalls in converting (amplifying) analog DC signal from transducer to measurements, except noise

texts:
I need to measure force with a load cell and transmit it to a computer.

The load cell outputs 2mV/V for whole range. Vdd < 12V, so I have 0..24mV signal, which I assume is enough to have good resolution and probably good signal/noise ratio.

The Manufacturer also produces amplifiers for these cells, which are pricy (cost as much as the cell itself), bulky and have extra features (like galvanic isolation), do I realy need them?

Is it a good idea to cut expenses using custom designed amplifier from standard instrumental amplifier (for example AD620) or put signal straight to adc (for example AD7705).


texts: A very basic question about the concept of feedback in oscillators

texts:
This is a conceptual beginner question. I'm novice about the oscillators. But I'm trying to understand the idea behind.
See for instance the following paragraph:

I can understand the idea of feeding back the equal amount of lost energy to the input to keep oscillations continuous. This is like when we give a push to swing to make the swinging continuous. And for that we should give the push at the right instant and with right amount of force.

But in the case of the circuit I guess they don't just tie the input to the output. There must be something between the input and output which decides how much amount of the output must be fed back to the input. And this has to be very precise.

Let's say I'm the interface which does this job between the output and the input. I'm the responsible unit to keep the oscillations continuous. And lets say I have the ability to sense the input voltage and output voltage anytime. What do I do with these info and process and find out the exact energy needs to be fed back?


texts: Multiplexing AVR (ATMega328) PWM within Interrupts

texts:
I'm trying to take 3 common anode RGB LEDs and hook up the cathodes of each to three of the PWM outputs on an ATMega328p and then in an ISR, multiplex between them all. The problem I'm running into however, is that even if I, for example, only want red on LED0 (out of LEDs 0 - 2) and I only turn on the PWM for that channel while the anode for that LED is turned on (logical High since common anode) I still get red on ALL the LEDs. See schematic below for how it's setup. To make things simpler, I'm only showing the schematic and code for one of the LED channels.

void setup()
{
  //Setup outputs for anodes
  DDRB |= (_BV(PINB0) | _BV(PINB1) | _BV(PINB2));

  //Setup Timer2 Interrupts
  TCCR2A = _BV(COM2A1) | _BV(WGM21) | _BV(WGM20); //Fast PWM mode on OCR2A (PINB3 - Digital 11)
  TCCR2B = _BV(CS22); //64 Prescaler
  OCR2A = 255;

  //Setup Multiplex ISR on Timer1
  // set compare match register for ~50Khz
  OCR1A = 300;
  // turn on CTC mode
  TCCR1B |= _BV(WGM12);

  TCCR1B |= PRESCALE1_1;
  // enable timer compare interrupt
  TIMSK1 |= _BV(OCIE1A);
}

volatile uint8_t col = 0;
ISR(TIMER1_COMPA_vect)
{
  //Set all anodes to LOW
  PORTB &= ~(_BV(PINB0) | _BV(PINB1) | _BV(PINB2));

  //Faking it here: Basically simulating that LED 0 is on but LEDs 1 and 2 are not.
  //Note that because the PWM is on the cathode, 255 is OFF and 0 is full brightness.
  if(col == 0)
    OCR2A = 0;
  else
    OCR2A = 255;

  //Turn on JUST the LED that we want.
  PORTB |= _BV(col);

  //Step through the LEDs
  col++;
  if(col > 2)
  {
    col = 0;
  }
}

simulate this circuit – Schematic created using CircuitLab

So, what I would expect is that LED0 is on at 1/3 brightness (since it's only on 1 out of three times through the ISR) and LEDs 1 and 2 are COMPLETELY off. However, instead, ALL the LEDs are on at all times and will sometimes seem to flicker a bit.

This has got me completely stumped. Because the only time that the PWM of the LED should be on is on LED 0 and for the times that the anodes of the other LEDs are turned on, the PWM should be set to 0% duty cycle (for a cathode PWM).

Obviously, I normally have a global variable that contains RGB channel data for each of the LEDs and that data is pulled from during each ISR step to set the respective PWM duty cycle for that LED. This is just simplified for the sake of readability since it happens regardless of what color channel I'm using.

Thoughts?


texts: RLC without Source, finding the value of Resistance given I(0)

texts:
A capacitor of 1.58mF was charged by a battery of 12V and lies on the ground of an abandoned radio station. During a storm, an old telephone cable fell from a rack and one of its tip got in touch with one terminal of the capacitor. The telephone cable has a resistance of 14mΩ and an inductance of 15µH.

A wet racoon entered the building and accidentally stepped on the not connected terminal of the capacitor and the telephone table. Knowing that he suffered 18µs
before being able to run away and that the current that made him squirm was of 100mA, what is the value of the resistance of the racoon?

simulate this circuit – Schematic created using CircuitLab

I imagined the circuit as above, where R is the resistance of the racoon. I supposed 18µs was to be considered as instantly after 0, so I had the initial value of current to find the coefficients with:
$$ \frac{di(t)}{dt} = - \frac{1}{L} \cdot (RI_o + V_o)$$
where
$$ I(0^+) = I_o = 100\,\,mA $$
and
$$ V(0^+) = V_o = 12\,\,V$$

From this, I tried to solve the EDO bellow:

$$ i''(t) + \frac{R_{eq}}{L} + \frac{i(t)}{CL} = 0$$
where
$$ R_{eq} = R_{racoon} + 14 \cdot 10^{-3}$$

But I'm not able to go further, since it seems not possible to know its root without R, nor its coefficients (bellow is the equation I found manipulating the variables):

$$-\alpha\,\pm \, \sqrt{\alpha^2 - w_o^2}\,\, =\,\,  \frac{R_{eq} \, \pm \,\sqrt{C^{-1}(R_{eq}^2C-4L)} }{2L} $$

So I kept thinking, is this question even analytically possible?


texts: Calculating the smallest control function (conjuntive normal form)

texts:
i am trying to calculate the smallest possible control function.

The function from the function table is:

A = NOT(S3) & S2 & S1 v S3 & NOT(S2) & S1 v S3 & S2 & NOT(S1) v S3 & S2 & S1

My solution is:

A = S1 & (NOT(S3) & S2 v S3 & NOT(S2)) v S3 & S2

The right solution is:

A = S1 & S2 v S2 & S3 v S3 & S1

I think the first part of my solution is not in the final stage.

What am I missing?


texts: DIY water tank gauge using analogue ammeter - linearity

texts:
A follow up question to my previous on building a DIY water gauge DIY water tank gauge using analogue ammeter.

I have scrabbled together a "Euro type" sender (10 Ω empty - 180 Ω full) and repaired the ammeter (which I need to keep). It has a resistance of 10 Ω and a full scale deflection at 6 mA (odd, I think, but it appears to have been adapted before).

Using the help gained from my previous question I have designed this circuit:

simulate this circuit – Schematic created using CircuitLab

It has (as I understand all Wheatstone Bridges will) a non-linear response.

My question: what simple strategies can I employ to make the response as linear as possible?

Edit: To add a graph of the sender's resistance vs tank level. These are actual measurements taken on the bench.

Edit: And an additional graph showing (I think) the discrepancy between actual level and the gaugeAmps.


texts: How can I disassemble an iPhone 4 battery without damaging it?

texts:
I would like to measure the power consumption of an iPhone 4 using a source/measurement unit.

On other devices I am able to connect the SMU directly to the +/- battery terminals, using tape to insulate the +ve battery terminal from the SMU's supply voltage thereby replacing the battery with the SMU as power source.

The iPhone battery connects to the rest of the device using the connector shown below.

I removed the outer layer of the battery & found that this is part of a small circuit board that is in-turn attached internally to the battery terminals (in blue).

I figured I could snip these contacts and attach the SMU to the circuit board to replace the battery, but in doing so I seem to have destroyed the circuit board (I assume from a short while cutting the contact)

I have two more batteries to experiment with: What method should I use to disconnect the circuit board from the live battery to minimize the chance of damage?


texts: Protecting fine pitch components from debris

texts:
I am making a Battery Management System. However the chips I am using are the LTC-6803-4 chips, and they have a pitch of just 0.5mm. The boards will be placed in a battery box with good ventilation, however I am worried that a stray metal shaving might come across the chip and short out multiple pins.

I am looking for a way to protect the chips in case metal shavings do find a way to enter the box. My first thought was hot glue, but I still need adiquite ventilation of the chips, and I am not sure about the conductive properties of hot glue.

I am sure this problem has come up in industry many times, but I just cant seem to find a simple solution. Any suggestions?


texts: LDO - SOT223 - What's the Fourth pin for?

texts: What's the fourth pin in LD1117-33 for (the thick on the top)?


texts: Building an electrolysis tank and I want to regulate a 1.23V into the tank. Any ideas how?

texts:
I am building an electrolysis tank and I need some help.

I am an architectural student and I have no idea how to regulate voltage or what battery would I need.
I want to regulate from the battery into the tank a 1.23V current.

Any ideas how to do this?


texts: what could be the visualization equivalent of the resistors in series?

texts:
Why do resistors in series add-up? Is there any visualization equivalent of that? I have  in mind electrons as cars driving on the highway, now a resistor could be a narrow spot (R1) where cars are moving slower, if I will "add" another congestion point R2 (resistor), after the first one, the cars that had already past by R1 will continue on R2,
in case R2 is narrower they will slow down even more,
in case R2 is wider it will be no problem since the cars will move freely,
in case R2 is the same again the cars will move freely after the first congestion point R1

Can someone explain in that way why should the total R is equal to R1+R2?

|Many thanks in advance!


texts: Can I drive stepper motor with AC voltage?

texts:
I want to buy this motor
SANYO DENKI 103H7823-1741 for building my CNC

I have found the datasheet over here

in the website that I will buy it from it says

Motor: AC; stepper; 100VAC; step 1,8°; 2.7Nm; 1.34kg; 4A

from what I know the stepper motors work with pulses but using DC voltage, so what does it mean to be rated with 100 VAC ?

EDIT

would it make difference if this motor was rated with DC voltage ?
Can I drive this motor with 24V DC(of course using stepper motor driver)?


texts: adding an alternative power net in KiCad

texts:
I have a board with a Raspberry Pi and an ATX power connector.  The Raspberry Pi provides 5V to some components on the board via its GPIO header.  The ATX connector also provides 5V to a servo.

How can I draw 5V_A and 5V_B symbols?  I am unable to edit the 5V symbol field value when I place the 5V components from the power library.  Using labels seems like it would work but I wonder if there's a better option.


texts:
I have just bought this pump to circulate coolant through an experiment. I would like to control the pump output as it doesn't have any control on it.

It is being powered from a 12V 0.5A power supply.

How would be best to go about this? Voltage control or PWM?


texts:
Why does some manufacturer which I know using NiMH battery in their products recommends to charge the product for like 24 hours the first time you charge it, yet the seller usually tells to charge only 8-10 hours the first time you charge it. Which one should we follow?  If we should charge it based on the sellers recommendation, then why did these manufacturers recommended to charge it 24 hours in the first place?

As side note the battery is usually around 1300-1500 mAh 2.4 V.

And There is no indicator whatsoever which tells how much charge is left on the battery. The charger itself is around 100 mA 3V (is this categorized as slow charging? ).


texts: This is sort of a spin off of this question.  Fluorscent have a tiny transformer inside them, and a bunch of capacitors, as well as transistors, and diodes.  What exactly happens when a light bulb goes out?  Is it the transformers fault?


texts: problem with using ili9341 TFT LCD with stm32f103RE

texts:
i successfully used a HAL code i found on Github for driving an ili9341 TFT LCD with SPI then I rewrote the code with registers. Part of my code works and i am able to fill pixels with color but when i try to use a function named ILI9341_Draw_Colour_Burst the code doesn't work. I tried to use the Keil debugger to see what happens and it showed a hard fault occurred. The function code is shown below
void ILI9341_Draw_Colour_Burst(uint16_t Colour, uint32_t Size)
{
//SENDS COLOUR
uint32_t Buffer_Size = 0;
if((Size*2) < BURST_MAX_SIZE)
{
    Buffer_Size = Size;
}
else
{
    Buffer_Size = BURST_MAX_SIZE;
}

LCD_DC_PORT->BSRR |= LCD_DC_PIN;
LCD_CS_PORT->BRR |= LCD_CS_PIN;

unsigned char chifted =     Colour>>8;;
unsigned char burst_buffer[Buffer_Size];
for(uint32_t j = 0; j < Buffer_Size; j+=2)
    {
        burst_buffer[j] =   chifted;
        burst_buffer[j+1] = Colour;
    }

uint32_t Sending_Size = Size*2;
uint32_t Sending_in_Block = Sending_Size/Buffer_Size;
uint32_t Remainder_from_block = Sending_Size%Buffer_Size;

if(Sending_in_Block != 0)
{
    for(uint32_t j = 0; j < (Sending_in_Block); j++)
        {
        write_buffer32((unsigned char *)burst_buffer,Buffer_Size)   ;
        }
}

//REMAINDER!

write_buffer32((unsigned char *)burst_buffer,Remainder_from_block)  ;

LCD_CS_PORT->BSRR |= LCD_CS_PIN;
}

and the code i wrote for SPI is as follows:
    #define RXNE    0x01
#define TXE     0x02
#define BSY     0x80

void  SPIInit(void)
{

   RCC->APB2ENR |=  (1<<12);      /* Enable SPI1 clock   */
     GPIOA->CRL&=~0xFFF00000;
   GPIOA->CRL |=0xB4B00000;

  /* Enable SPI in Master Mode, CPOL=0, CPHA=0. */
  /* Clock speed = fPCLK1 / 256 = 280 kHz at 72 MHz PCLK1 clk. */
    SPI1->CR1  = (0 << 0) | // Clock phase
                 (0 << 1) | // Clock polarity
               (1 << 2) | // Master selection
             (1 << 3) | // Baud rate control clock/2
                             (1 << 6) | // SPI enable
                             (0 << 7) | // Frame format : 0: MSB transmitted first
                             (1 << 8) | // Internal slave select
                             (1 << 9) | // Software slave management enabled
                             (0 << 11); // Data frame format :  0: 8-bit
  SPI1->CR2  = 0x0000;
}

u8 SPI1_WriteByte(uint8_t TxData)
{
  /* Loop while DR register in not emplty , 1: Tx buffer empty*/
   while ((SPI1->SR & TXE) == 0);
   /* Send byte through the SPI2 peripheral */
   SPI1->DR = TxData;
   /* Wait to receive a byte ,1: Rx buffer not empty*/
   while ((SPI1->SR & RXNE) == 0);
   /* Return the byte read from the SPI bus */
   return SPI1->DR;

}

void write_buffer(unsigned char *data,u8 size)
{
  u8 i;

  for(i=0;i<size;i++)
  SPI1_WriteByte(data[i]);

}

void write_buffer32(unsigned char *data,int size)
{
  int i;

  for(i=0;i<size;i++)
  SPI1_WriteByte(data[i]);

}


texts: ARM LPC2148 Bootloader filesystem problems

texts:
I installed Keil's LPC2148 bootloader on my ARM board and as indicated in the docs my PC is able to identify it as a mass storage device. However, the bootloader uses FAT16 filesystem which is apparently incompatible with my Windows 7 Home Premium (64-bit) PC. It works just fine when operating on a Windows XP system and I am able to copy files to the ROM.
As I didn't have XP mode on my Win7 machine, I loaded a virtual machine using VMWare with XP and bound the board's USB to it but to no avail. Any attempt to copy files into the device causes the virtual machine to 'hang'.

Why is it that the same copy-function works on a 'real' XP machine but not on a virtual machine? Is there any other alternative?


texts:
I am using the PE42423MLBA-Z RF switch.
I am trying to get an idea of the output current given by this chip.

Now E = Sqrt(P)*R. E =5V, R = 50Ohms.
So, P = 10mW.

But, this is a switch, that merely routes power/signal with almost no loss in efficiency. Hence, in ideal cases ,Pout = Pin.

Pin (max) = 38.5dBm, which roughly translates to 3W or so. How am I getting 2 different power ratings ?


texts: How do I send a signal from my computer to my USB antenna

texts:
I'm trying to make an RC car that can be controlled by my computer.
The heart of the car is a simple mother board from an old toy. It basically accepts a signal 49MHz from a controller with a 9V battery.
I want more range on the controller but the output strength isn't strong enough. The controller circuit is only rated for 9V, so I guess ramping up the power isn't an option.
Overall I want to output a 49MHz signal from my computer out of a USB port.
Is that possible? If not, any solution would be awesome.


texts: Need approval of transformer driver design

texts:
I designed a circuit from several ideas I saw before and I'm a bit too impatient to build the thing myself.

(http://imgur.com/KD97NuJ)

Basically, it's a two-transistor oscillator combined with an inverter and a circuit that I saw somewhere. The oscillator generates a DC signal, which is converted into a square-wave AC signal, used to drive the primary of a transformer. My goal is to make a high voltage power supply powered by 4 AA batteries for various fun experiments.
Anyways, will this circuit work, and if not, why?


texts: Generic number of Component declaration in VHDL

texts:
I want to design a 64 entry register file. Now instead of defining all the registers separately, I want to do it in a more compact form like using a loop.
Is it possible? If yes, then how?


texts: Can this be reworked with a hot air gun?

texts: I posted before about the Microchip RN4020 (Bluetooth Low Energy) PicTail failing. I have some spare RN4020 modules and access to a heat gun. If I can take this RN4020 off and put a new one on, how would you suggest I do it? Or is it too large or difficult because of the package?


texts: Round/smooth PCB traces or angular traces?

texts:
I was looking at my LAN8720 module because I tried to build one myself. I realised that the traces on the PCB have mostly round edges/are really smooth while other PCB layouts I see have angular/edgy edges.
Should I make my traces also smooth or does it not matter?


texts: Why Doesn't the Current in a Transformer Diverge?

texts:
I just started learning about mutual inductance and transformers, and I haven't been able to find the answer to this question. I suspect it's really basic, and that I'm just missing some understanding.
Say I have 2 coils, A and B, both wrapped around a common volume, and the two current directions denoted -> and <-.
If I quickly increase the -> current in A, then this induces a large voltage in B, causing a <- current.
As the current in B now increases, it will again induce a voltage and -> current in A. But the current in A was already going in the -> direction, so it looks like it just got a boost which obviously violates conservation of energy. Where did I go wrong?


texts: Choosing the shunt resistor value and capacitor for op-amp integrator based on input resistance and DC gain

texts:
I think it's option C based on C = 1/R and the R2 as 10 times R1 but apparently the answer is option A.
Please tell me where i'm going wrong.
The full question reads

The following figure shows opamp-based integrator circuit. If this circuit were to integrate a symmetrical pulse waveform ...


texts: Instrumentattion amplifier gain appears to change

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I made a very simple circuit to amplify a ~1 mV signal up to ~2 V.

The input is a 0~2 mV DC signal from a scientific instrument.

The problem:

I made the circuit, and it worked as intended. The 1 mV signal became 0.2 V, with the intended gain of 200. At home, I input a ~1 mV signal that I made by splitting 5V (wall adapter) into 4.999V and 0.001 V with resistors.

Next, I used the circuit with the scientific instrument. The input was ~ 1 mV, but the output was only 30 mV! The gain appeared to have changed to 30!

(I then double checked the gain with the split voltage setup--200 as intended. So nothing is broken, etc.)

The difference between the two cases is only signal source.

I am measuring the signal source with a digital multimeter. Both cases are ~1 mV. I tried measuring the current from the scientific instrument--it doesn't show up even on micro ampere scale--I didn't expect a current there, anyway. The scientific instrument signal is steady--I do not detect noise with my multimeter (0.1 mV precision).

Question:

Could there be some other difference between the two signals that would affect the gain?

Other bits of information:

The millivolt signal is the pressure reading output from a Shimadzu HPLC pump.

The circuit I built is copying the schematic of Figure 48 ("Optimal ground practice in a single supply environment") on p 20 of the AD623 data sheet.

In the figure, there is a cylinder-shaped symbol around the signal input. I don't know exactly what this is, but I have done nothing to my signal input. On page 19 of the data sheet, in figure 44, 45, there are schematics for RF interference protection and other input protections. Since my circuit works when I apply a ~1 mV signal from a split voltage, I didn't think there is a problem with RF interference in the environment, etc., so I didn't do any input protection.


texts: How to block/allow an i2c data signal to pass on to another device

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I have three devices which I'm working on and one of them needs to control i2c communication between the other two.

Each of the devices is based on an AtMega or AtTiny chip. The Controller (based on some external input not known to either the Master or Slave) needs to be able to decide whether or not to pass on the i2c signals to the Slave.

I'm assuming you can just 'block' the data signal (no need to stop the clock signal being passed through) in some way. I've looked at devices like Single Fet Bus Switches but I wonder if that is the best way or not.

The setup looks like: Master --i2c-> Controller --i2c-> Slave


texts: How does a device's physical size affect its parasitic capacitance?

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I'm looking at a very small bi-directional diode and for this RF circuit, an ESD with parasitic capacitance << 1pF is recommended.

The diodes I've seen for this application are VERY small.

Why are these devices so small?
Does the diode's size affect the parasitic capacitance?
If so, what calculations are use to determine the capacitance?


texts: Transient analysis initial conditions in book

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There is an example in Book:

Why is \$V_R = 5i_R\$? I can't see that.

more info:


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In a course I am taking on embedded systems, I program LPC1768s which are based on ARM using C.

The main functions are always of int return type. However, there are no return statements in the end like a return 0.

I believe this may have something to do with the infinite while loops that these programs use because the controller is never really able to reach the return statement. However, I thought that as this is C, there might be errors, though it turned out that I was wrong.

Just for reference, here is the main function of a program trying to use UART

int main (void)
{
    SystemInit();

    GPIO_PinDirection(LED1,OUTPUT);        /* Configure the pins as Output to blink the Leds*/
    GPIO_PinDirection(LED2,OUTPUT);

    TIMER_Init(0,100000);                  /* Configure timer0 to generate 100ms(100000us) delay*/
    TIMER_Init(1,500000);                  /* Configure timer1 to generate 500ms(500000us) delay*/

    TIMER_AttachInterrupt(0,myTimerIsr_0);  /* myTimerIsr_0 will be called by TIMER0_IRQn */
    TIMER_AttachInterrupt(1,myTimerIsr_1);  /* myTimerIsr_1 will be called by TIMER1_IRQn */

    TIMER_Start(0);                         /* Start the Timers */
    TIMER_Start(1);

    while(1)
    {
        //do nothing
    }
}


texts:
Hello I am trying to communicate that is using SMBus. So when I try to send a data which was 0x0D and address of the device was 0x16. I see something like that on the data line:

And this is how my clock (SCL) pin looks like:

So my questions are :

Is this data and clock signals look normal? I know data is not normal because I cannot transmit the message but what about clock signal?
So Data looks like 1 1 1 1 1 1 .... 1 1, is it because I cannot ack ACK/NACK from slave, it keep sending the data over and over again? Or maybe something else behind this strange data signal.
I used 20 K pull up resistors for SDA and SCL for 5 V Vdd. (For SMBus I think I should have used 15 k ohm.) Can it be the reason? Or any other ideas that causes this? Thanks beforehand

In the datasheet of the battery that I try to communicate, it says:

So I thought I could use 20 k ohm as pull up resistors.(to be honest I could not really understand what they say in the document..)

And this is how SCL/SDA signals look like together

This is the circuit schematic (I use RB1 and RB2 for SMBus communication.)

This is the pin diagram for the battery. I am communicating with the first section, PINS 1-4:


texts: relay coil voltage: can I have trigger with both 110v and 240v?

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I'm searching for a relay that can both trigger and switch on either 110v or 240v. To clarify - both the coil voltage and the switched power would be the same voltage - and as low as 110v or as high as 240v.

(think of an appliance that could ship in the US, or internationally).

The relays I've found so far trigger at ~80% of max coil voltage, which isn't enough latitude to run in both scenarios. Am I likely to find a relay like this, or should I devise another solution?

Per request: here's the relay I was looking at with a datasheet for    LY2F-AC220/240


texts: The criterias to select peak detector capacitance and resistance

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edit: diode is replaced with 1n4148

While designing such a peak detector, what should be the approach of choosing C and R values? Which specs of the detector will be based on them? I assume their values will be depending upon the frequency of incoming signal, and related to time constant of RC network. But, I need some better understanding.


texts: Variable Current Draw from motor for torque control

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I am building an electric go-kart. I would like to use regenerative braking. I would like to have a brake pedal that controls the amount of torque (slowing the motor and wheels down) that the back emf from the motor creates.

In a hypothetical situation, the motor (90amp 36volts permanent magnet dc motor) will be spun up when the car accelerates. It will then spin freely once up to speed. This part of the circuit I have figured out this part of the circuit already.

(in this image the important switch is the pedal microswitch which closes every time the throttle is engaged Also, the Main, Foward (F) and Reverse(R) notations refer to contractors used to provide power to and switch the polarity of the motors respectively)

If we now treat the motor as a generator, from what I understand the amount of current that we draw from that generator the more torque will be applied to slowing the motor down. If we take the extreme and fully connect the motor leads together with zero resistance the motor will lock up.

Where I am confused is how to draw variable current from the motor and control it with the brake pedal. For safety purposes, I plan on installing a mechanical hand brake as well.

Any help on this would be appreciated, I am sure that I do not have a full understanding of this mechanism.

Note this diagram is from a Curtis motor controller manual. Here is a picture of the cover.


texts: DAC/ADC Precision & Noise: PD Resistor/Capacitor effect

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I'm developing a device that utilizes both ADC and DAC, and I have realized that my DAC output, which is fed into the op amp, is de-facto almost floating, since op amp has high input impedance. Both DAC and ADC are on the MCU now (STM32G071KBT6), although for some time they were discreet components, which doesn't matter much, I guess.
I tried to google some stuff, and only found out that lines that end up with Hi-Z are susceptible for noise, which makes sense to me, but nothing more specific.
Also, some discreet DACs have max output capacitance in datasheet, which is usually of order of 1000pF, some a bit more, some a bit less (others never mention output capacitance).
I tried to google specifically my question, but couldn't find any reasonable answer.
Should I have some large pulldown resistor on DAC output to add it some stability and noise resistance? Some 47k (which are everywhere on my PCB, so another one won't hurt). Why, why not? (I would also really love to be able to go close to 0V output).
What about ADC? My ADC is fed from the voltage divider from the current sense amplifier, total resistance of that one is ~15k (5V->3V3, 4.7k/9.12k to produce 3.299 from 5V to stay in range, will have to account for tolerance too, probably in software).
If I fed my ADC (input) from op amp directly, it would create same problem as with DAC output into op amp. Would I need a pd resistor there? What about capacitor on the ADC line?
Summary of questions:
ADC input: capacitors and pd resistors? Yes/No, when, why?
DAC output: capacitors and pd resistors? Yes/No, when, why?


texts: Signal representation in frequency domain

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My teacher taught me that the frequency representation of time limited signal will be band unlimited.

Also the frequency representation of time unlimited will be band limited.

i.e frequency domain representation of rectangular function will be sinc which is perfectly fine.

Now,the question I have is if I have series of rectangular pulses

Why don't I get band limited signal?


texts: Plotting step and impulse responses on Matlab

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I'm trying to graph a simple response function:
1/(1-0.5s^-1)

Now, I know that the function can also be written as: s/(s-0.5)

So I tried plotting the step and impulse responses in Matlab:

sys = tf([1 0],[1 -0.5])
figure(1);
step(sys);
figure(2);
impulse(sys);

And these are the graphs that I'm getting:

I think the shape of the step response is right; however, shouldn't the impulse response decay?

It just doesn't seem right that both graphs have the same shape.


texts: LTSpice Simulation Showing Inaccurate Results and Excessive Current

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So I'm trying to make the following simulation work properly to verify some hand solving for a circuit. The circuit is an LC tank with some diode clamping, and an initial capacitor voltage of -50V.

I tried both with and without a switch to see if that helped...it didn't.

Solving for this by hand I expected to see around 300A as the initial surge current, but it's up in the high kA range in the simulation. I know this can occur with LTSpice time base errors, but here's the stranger part

I had it working fine, then accidentally didn't save the changes. Now I can't make it work properly for some reason. I've tried:

all the integration modes
normal/alternate solver
Taking the maximum timestep all the way down to 1E-12...took forever but it didn't help.

Nothing seems to make this simulation behave properly. Is there anything else I can try? I don't know why it isn't working now as opposed to earlier.

Thanks!


texts: Solar cells, current limited by smallest cell?

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I've read on a bunch of different sites that:

"You also do not want to mix different sized cells together because the current or AMPS of your solar panel will be limited by the smallest cell in the group"

"the output capacity of the entire panel is limited to the output of the smallest cell on the panel"

"the current will be limited by the smallest cell in the group and the larger cells will not work to their full potential."

"mixing cell sizes is not a good idea. This is because the current your panel can produce will be limited by the smallest cell in the group and the larger cells won't work to their full potential"

... and I'm wondering why?


texts: What gauge of single strand wire works well with breadboards?

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I bought some single strand wires hoping to prototype on the breadboards. Unfortunately it was too small to properly fit into the breadboard holes.

So my question is which gauge fits well on those small holes of breadboard?


texts:
I'm working on some boards layed out before my time, or anyone that I can ask why they were made this way. Very much learning as I go, and I'm confused by this.
They all tend to have this loop around the board.
It's not connected to anything.
Even a simple break out for a connector has this same loop trace.
Why? What does it do? Is this a good practice?
Thanks.


texts:
I'm planning a communication bus between one ATxmega256A3U and multiple ATxmega64A3s. The challenge is that I need to use as few wires as possible, so I would like to address the slaves without a separate slave select pin for each. I need to estimate the maximum speed of the bus, because I have to guess the maximum number of slaves per one master.

Fortunately, both support TWI, which is a I2C implementation, if I understand correctly.
I2C defines multiple speed grades:

standard mode: 100 kbit/s
full speed: 400 kbit/s
fast mode: 1 Mbit/s
high speed: 3,2 Mbit/s

The XMEGA datasheet clearly states that the standard and full speed modes are supported.

According to the AVR315 application note:

  The Bite Rate Generator unit controls the period of SCL when operating in a Master mode. The SCL
  period is controlled by settings in the TWI Bit Rate Register (TWBR) and the Prescaler bits in the TWI
  Status Register (TWSR). Slave operation does not depend on Bit Rate or Prescaler settings, but the CPU
  clock frequency in the Slave must be at least 16 times higher than the SCL frequency.

The XMEGAs will run at 32Mhz, so slave speed is maximized at 2Mbit/s and we can use following the formula to calculate the exact speed

  I2CSpeed = CPUClock / (16 + 2 * TWBR - 4^TWBR), where valid TWBR values are between 1 and 256

I think it might theoretically be possible to reach the fast mode, since 32/(16*1-4^1)=2.66Mbit > 1.0Mbit (speed of fast mode).
(Fast mode's protocol is backward compatible with full speed.)

Has anyone reached this speed with XMEGA's TWI in practice? Are there any other limitations which I didn't realize?


texts: Gate Driver Not Working as Expected. Why?

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I am using the ADuM5230 gate driver to drive an N-channel MOSFET in a basic buck converter circuit that will convert a 12V DC input to a 5V DC output. The buck converter will operate at a 10kHz frequency and is to drive a 10 ohm load.

Block Diagram of ADuM5230:

The schematic of the converter on Proteus software:

Capacitors according to datasheet (tantalum & ceramic).
Three-Pin schottky.
Used this MOSFET.
Supplied 5V on Pin 2 and PWM signal on Pin 5, from power supply and signal generator respectively. I will use a micro controller in the future.

When I built the above circuit on a breadboard, I saw a 5V output across the load, as expected. Capacitor values are 10uF and 100nF as specified.

However, when I came to test the circuit on the PCB schematic provided below, the driver only produced 5V between the Viso and GNDiso pins (15 and 14) instead of 15V. The gate driver proceeded to heat up extremely quickly and somehow pulled more than 3A from the power supply. What am I doing wrong here?

PCB layout:

Track width is T50 and T20, while via size is T70.

Any ideas or suggestions on what could be going wrong?


texts: Determining LED power supply (Series & Parallel)

texts:
I have the following LED array:

I need help calculating the power supply needed. All the LEDS are the same - 1W, 700mA and instead of just 5 columns my actual circuit has 14 columns (as in the second picture). Please can someone teach me how to do the calculations for this circuit. If it were a straight forward parallel string of series LEDs, I would not bother you, but the additional junctions throw me off a bit.

Please don't suggest alternative layouts as this is what I am reverse engineering.

Thanks


texts: What's wrong with this ring counter made using D Flip Flop?

texts: I have created this ring counter using D Flip Flop in multisim(I am learning counters). It's not working maybe due to the switch provided on the top left for the preset pin of D Flip Flop. I have no idea how to correct it. Any help would be highly appreciated.


texts:
Can anyone explain if it's good to have the Gnd pin of a Bypass Caps tied to IC's Gnd? I've observed some design using those methods. Just want to have a justified answer.

I'm not sure if the thickness of the board plays a huge role in here.


texts: STM32F4 custom board, low voltage on reset pin

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I designed the following the STM32F407vgt6 custom board for a project.

I recently soldered the parts, and powered the board up. I tried programming the board via an STM32F429 Discovery board through the SWD interface and got plenty of errors indicating the MCU was being kept under reset. Then I probed the NRST pin and read a value of 0.40 volts.

The MCU is brand new. All the decoupling capacitors seem to be getting enough voltage(2.9 volts). Regulator works fine too. I am not sure why the NRST pin is at low voltage. Here's the relevant part of the board layout.

edit1: This is a two-layer board with the top layer being GND+signal and bottom being VDD+signal. I think it's worth mentioning that sometimes the NRST goes down to 0.20 volts. It just varies around 0.20 - 0.40.

I can add a picture of the board if you guys want to see the if there's anything wrong with soldering.
Here are the pictures of the board. Notice that I tried to cut the VCAP line, but it didn't help assuming I successfully cut the line.

update

I pulled the NRST pin high. After that, I was able to connect and program the MCU via the STM32F429 board through the ST-Link utility. ST-Link utility states that the memory is programmed and verified. I wrote a small program that toggles a few GPIO pins, but when I measure the voltage on those pins I don't see them going high(3V) or low(0V). They just vary around irrelavant values(1.2V, 0.4V, 0.9V etc.).


texts: Charging a 12V battery bank while using it

texts: I have (4) 12V 190 Ah AGM batteries connected in series. I want to run a portable A/C unit through a 2000 watt inverter connected to those batteries and charge the batteries simultaniously with a battery charger powered by a generator. The A/C unit requires 7.5 amps continous and 15 amps surge. I would like to do this because with the A/C unit connected to the generator, every time the compressor kicks on the generator revs up which is just annoying. My plan is to use a 100 amp charger to contiually charge the batteries while im running the A/C. I calculate that the A/C will draw approximately 83 DC amps while running.


texts: Issues with hooking up a solar panel to an air pump for a mini-hydroponic School Project

texts:
I am new to Solar and but I am a High School Science teacher. My question is in regards to a small scale hydroponic project that runs off solar.

I need to get the 6v 2w 350mA solar panel to power up a Koge air pump that draws 4.8v at 100-250mA. When I used alligator clip leads to connect the terminals and had a 100w incandescent bulb 5 inches from the solar panel...nothing happened.

What am I doing wrong? What do I need to add? Your help is GREATLY appreciated!


texts: saftey wiring lipo's in series and parallel

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I want to make sure I am being as safe as possible. I have 2 18650's wired in parallel and 3 of those pairs wired in series with a 3 cell BMS board. I also have a constant current driver at 700 mA with a fuse that breaks with current more than 1 A, that is overall powering some decently bright leds.
I am making a flashlight for someone and I want to make sure I am absolutely being as safe as possible; I don't want the batteries to blow up on them or anything like that.

I know that when wiring the batteries in series/parallel its essential to have the voltages the same to prevent backflow. If their voltage is off by 0.1 V is that still acceptable? I know the BMS baord should help prevent over dischange and such, but is there anything more I should know to be safe? Could there be any danger with the batteries leaving them wired together constantly, even when not in use?

I apologize if my questions are dumb, I've tried to do the research to be safe I just want to make sure that I'm not missing anything and that there are no concerns and I wont end up putting anyone at risk. I can attempt to draw the full circuit if that would make it easier to provide feedback


texts: I am using the UART of ATmega16 for transmission. It is connected to XBee using a development kit which already has a MAX232 IC. How can I use the UART of ATmega16 with XBee? The other XBee is connected to PC.


texts: Resetting a microcontroller with a button connected to Vcc

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I would like to have a way to reset my PIC by removing power from the chip.  My hacker self thinks that the simplest way would be to add a resistor between the output of my LDO and Vcc on the PIC, and then add a button between GND and after the resistor.  To avoid any potential issues with switch bounce, I figure I could add a cap in parallel with the button and a resistor in between, like this: (ignore component values, those are the defaults from the editor)

simulate this circuit – Schematic created using CircuitLab

Is there anything seriously wrong with doing it like this?  I'm trying to keep it simple and not require a bunch of components.


texts: Connecting 4 18650 batteries in series without bms

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I have 4 batteries (18650) 3.7 volt each and i want to connect them in series to get around 15 volts, can i do that without having a bms? Just directly connecting them together?
Note: i do have a charger specifically to charge this type of batteries, so if your answer is "bms is better for safe charging" please don't, charging isn't my concern.


texts:
The attached photo is pulled from a Piccolo DSP reference design from TI.  They use 57.6k pull-up resistors and 2.2k pull-down resistors to allow configuration of boot pins at startup.  I've seen all sorts of values for static configurations like these, and I'm not sure why you would choose 57.6k/2.2k vs. 10k/1k, or 10k/0 (i.e. tie switch pin directly to GND).

Are the SW1 pins not shorted to GND to protect against an accidental short if the GPIO is misconfigured to be an output?

Why did they choose 57.6k/2.2k?

Another example is the write-protect pin on an EEPROM.  It can be configured via pull-up/down resistor to set a static config, but I've seen designers choose to use 330/1k/2.2k/10k/etc resistor to pull the pin to GND or VCC (even when the pin can't be misconfigured as an output).  The only reason I can think of is that this provides flexibility for some kind of automated manufacturing ICT test to pull the pin in the other direction.  For example, if the EEPROM is normally write protected, but manufacturing wants the ability to program in-circuit, then connecting the pin via 2.2k ohm resistor (instead of shorting it to VCC or GND) allows the test probe to pull the pin into write-enable mode temporarily.

What are the other considerations for choosing pull-up/down resistor values?


texts: Source of Audio Noise at Low Volume -- BlueTooth Mini Amp board

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I'm still learning some of this stuff.  This is the first time I'm really using an oscilloscope in a few decades.  I picked up a small bluetooth only audio amplifier board. Puts out a whole lot of power, 40 watts/channel to 4 ohm speakers.  Uses a TPA3116 Audio Amp Chip.  The board requires 18 to 24vDC input.

Unfortunately, I hear a lot of unwanted noise at low volume levels, or when ever there is a pause in a song.  It's pretty irritating. Its more than simple white noise.

So I'm trying to figure out if my power supply is causing the issue.  I'm using an old Compaq laptop switching power supply, circa 2000. The power supply puts out 19v, 3amps.  Here's a trace of the power from that supply, under load with the audio board displayed.

On that trace, the time division is set at 1 micro second. The vertical division is set at 0.5v / div.

I'm not sure the best way to test for this.  Build a filter and see what happens?

If I wanted to filter out that ripple, what type of filter design would I use?  Any hint on how to size the components to handle the appropriate current / power?  Many thanks.

Update:
So I borrowed a friends bench top power supply.  It was of pretty nice quality, and included a current display (as well as current limiter)  I initially set it to 20volts DC, then hooked it up to the bluetooth amp.  Uh-oh... I got nearly an identical display as before.  The peak to peak wasn't quite as high (only 0.5v) but the shape of the curve and the time division was identical.  Oh, and I did note that the amp meter registered 0.1 amp during normal audio steady state.  There was no change to the undesired noise at low volumes.

As I played a bit with the audio volume, I was surprised to see the trace expand in height during heavy beats or loud portion of music.  This got me to thinking.. with the oscilloscope, I'm just taking the measurement of a system.  Who's to say that the trace I'm seeing doesn't represent the source minus the load of the audio amp.  (I know those aren't exactly the correct words, but I think you get my meaning...)

So I went back to my original power supply.  I added a 1/4 watt 3.28K ohm resistor across the output (6 mAmps)  The output trace of that looks nearly like a sine wave, with a peak to peak voltage height of 0.040 volts, and a cycle at 285 KHz.  That seems much more reasonable as the DC output for a switching power supply circa 2000CY.

So my bottom line now is: I don't think the power supply is inducing the unwanted audio noise at all.  I believe that is coming out of the blue tooth signal processing in the unit.  I suspect mediocre board design.  I do see nearly identical boards for sale, with additional capacitors on them (design improvement, phase 2?)   ...Sigh.

update, 15 Jan 2016
@ruminant1 you are my hero.  Much improved.  Not perfect, but much improved.  Many thanks.


texts: Raspberry Pi not Compatible with Mosfet?

texts:
This is my mosfet datasheet RFP30N06LE

i have my schematic setup exactly like this (except powering a 12v load not 60v) and even confirming with a multimeter when i set my gpio pin to high that there is a 3.3v voltage between gate and source. upon disconnecting the gpio out jumper wire and supplying 5v from the raspi instead, current is allowed to flow between drain and source and my load (12v dc fan 500ma) is turned on.

why does this work with the 5v pin and not the 3.3v gpio pins?

I have tried to switch out mosfets in the event there is a bad one i have and even moved them around my breadboard and swapped cables in case of any faulty wiring. Based off the data sheet i see 250uA as the VGS(TH) testing and a max of 2v.

the raspi delivers 3.3v and i think max around 50mA on the 3.3v rail, am i reading these mosfet charts incorrect?


texts: Is FPGA the right way to go for recognizing cards from a desk?

texts:
I'm building a playing card dealing machine and I would like to get some advice in regards how I should do with my image processing.

The card will be scanned and depending on the suit and rank of the card it will be place in 1 out of 4 slots.

The best way I believe (Which does not have to be the right one..) is to use a FPGA chip for the image recognition. A FPGA chip seem to be very affordable for the speed but I have no experience with this. So here is a few questions.

Is FPGA to way to go or should I look into a different solution? (Low price and energy consumption is two important factors for me)
Is it best for example to read the corner of the card and read the suit and rank individually(4 suits and 13 ranks) or just compare against the 52 cards right off? I really want the solution simple so I can for example easily use different layouts of decks.

Hope I'm making some sense here!

Thanks,
Stefan


texts:
I recently acquired a Seiko slave clock, like the ones used on ships. It has 2 coils, one for advance and one for retard. I'm intending on making a master clock for this out of an RPi or ESP32 or something similar, but I need to figure out how it works first.

The coils are marked 24 VDC/2000 Ohms, and I've found some semishady references that it wants an impulse every ½ sec, so my current idea is a 2 Hz square wave with a 24VDC peak, but do anybody on here know anything more about how these operate?


texts:
The following circuit converts high-frequency electromagnetic fields to direct current (DC) power.

I'm trying to understand how it works.
The diodes are used to rectify the signal, however it's not clear to me why they are put in that particular configuration and why we need four of them (and not only one). It this sort of voltage doubler ?

Also, AFAIK, C3 and C4 are used to store the electrical energy. But what is the purpose of C1 and C2. Does it act as a filter ?


texts: How does the change of load on the Rx side influence the Tx resonance voltage in a wireless powering sysytem

texts: As the circuit shows, U = 5V toggling the polarity in 10KHz. When IL is changed from less than 1mA to 20mA, the P-P voltage of the Tx coil will increase. How should I understand the phenomenon? I have guessed that the increase of IL will only decrease the voltage on the Rx side.


texts: The system is not completely reachable, Is state x1 reachable from x0?

texts:
The system is
$$
x(k+1)=\begin{bmatrix}
    1 & 1 & 0 \\
    0 & 1 & 0 \\
    0 & 0 & 1
  \end{bmatrix} x(k)+\begin{bmatrix} 0 \\ 1 \\ 1\end{bmatrix} u(k)
\\ y(k) =\begin{bmatrix}
    1 & 1 & 0 \\
    0 & 1 & 0
  \end{bmatrix} x(k)
\\C=\begin{bmatrix}B & AB &A^2B  \end{bmatrix} =\begin{bmatrix}
0&1&2\\1&1&1\\1&1&1\end{bmatrix}
$$

The rank of C is 2 that is not equal to the full rank. The means the system is not reachable. However, the system can be not completely reachable if the state that the system should go to is linearly dependent to the basis of C

Let the state x1= \begin{bmatrix}3\\2\\2\end{bmatrix} that reachable form the zero state.

My questions are

1) how to determinate the minimum number of step to reach x1?

2) What input do I need? and how do I verify my answers?


texts: Using a delay circuit to keep track of button presses

texts:
I'm running off batteries so I don't want to leave the esp8266 on unless there is a state change. I have the button hooked to +3.3v that triggers the reset pin on the esp8266 which then sends the data off. This works fine but I would like to use 3+ buttons and I need to know which button was pressed. Since the esp8266 is just being reset there is no way to tell which button reset it so I was thinking of hooking each button up to a RC delay circuit to keep it's state longer so the MC can then boot up and read it. Using this formula

$$t = -\log \left( \frac{V-Vc}{V} \right) \times RC$$

I should be able to keep the buttons in the correct state long enough for the MC to boot and read the values while not using a lot of energy.

Is there a better approach, easier?


texts: How to design and implement a sequence detector

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I have to implement a Moore machine that has an input L and an output Z.
The input line L provides values of 1 and 0 as input, in a random order.
The output line Z takes the value 1 whenever two values of 0 and two values of 1 have been detected in the input, no matter the order.
For example the sequences 0011, 00001001 and 1010 would all set line Z to 1.
I have to use D flip-flops and NAND gates only but am stuck halfway.
So far I have drawn the state diagram and the table below: (CS stands for current state and FS stands for future state).
I know that I must draw 8 Karnaugh maps I think but I am not sure and I have to use 3 or 4 flip flops.
Could you point me in the right direction?
EDIT
After some more research I managed to finally draw the Karnaugh maps and extract the functions, and I designed a circuit using LogiSim. I am not sure what I have done wrong and have no idea how to proceed. The circuit is not doing what it's supposed to do. Here is a link to my LogiSim circuit.


texts: Unamplified AND Amplified input on the same speaker

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I would like to at night use just my (unamplified) phone as signal for two speakers.

However, I also want to use them with an amplifier. To do so, would I need to just switch between the + cables, and join the other ones, or will doing so be potentially harmful to the phone? (since it is an ac current) or would I need to switch out all of the connections? (by using a switch with 4 channels)

I really like my phone, so I don't want to just try it.


texts: What component does this symbol represent?

texts: Can anybody please tell me the name of the component represented by this symbol (encircled in picture.)


texts:
I'm looking to power about 10m of RGB LED strips (60 LEDs / meter) from a battery of some sort. Max current draw for the 10m run is 36A @ 5V.

My initial thought was to get a ~12V RC Car battery and run it through multiple DC/DC buck converters to get it down to 5V (probably get 8 rated at 5A or so) but I wanted to make sure I wasn't missing another, possibly cheaper, option. Runtime doesn't have to be super long... I'd be happy with anything beyond 20 minutes.

Also, note that 36A is absolute worst case scenario. Everything full white. In reality, it would probably average 1/2 - 1/4 of that... probably even less. But, obviously, I want to design for beyond max possible current to give some margin of error.

Battery needs to be rechargeable. Are there any other good (and hopefully cheap) options for providing that much power?


texts: How much can I safely plug into a light socket converted to a standard outlet?

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I just moved my office desk from our extra bedroom on to our stairway landing.  The tricky thing was that there was no wall outlet to plug anything into.  However, there was a nearby light socket, which I converted into a standard outlet using a GE polarized handy outlet.
Upon reading the label on the packaging, it says there is a 125VAC 660W max.  It also said on the back to not exceed electrical ratings in order to avoid the risk of fire.  I also had to use a Non-grounded to grounded plug converter to be able to plug my power strip in.

I'm not an electrician and I don't know too much about this beyond my high school electronics class.  Am I going to be safe if the only things I have plugged in to it are my Macbook Pro and my flatscreen LED LCD monitor?  I have done some research for my macbook to see how much power it uses and found that it rarely will ever go above 45 watts.  Assuming my LCD monitor also doesn't exceed much more than that it seems to reason that I would be safe.  ~100 watts is far less than the 660 watt limit. Am I making some correct assumptions here?  What else do I need to consider?  Would I also be safe to plug in a printer and possibly more appliances?


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In a Battery Charging application, i am using ADS8319 ADC from Texas Instruments for digitizing the charging voltage and current signal, and providing it to the Microcontroller via SPI interface. (Battery charging will be done via synchronous Buck converter running at 62.5kHz, and ADC's sampling frequency would be a few Hz considering its a battery charging application). I will be using 2 of these ADCs (one for current and one for voltage measurement) as its a single channel ADC. For reference signal to this ADC i will be using the reference voltage IC REF5050 from TI. Two of these IC's will be used to provide reference to the ADS8319 seperately.

If you see in ADS8319's data sheet at page 21 Figure 59 and at page 22 Figure 60, two different methods of interfacing this REF5050 with the ADS8319 have been used (one is using OPA365 as a buffer i guess, and the other one is interfaced directly with the ADC). However i couldn't find the significance of (using or not using) the OPA365.

So my question is, should i consider using this OPA365 in between the REF and ADC ICs ? Would it (using it or not using it) effect in my case ? Offcourse i'd find it easy NOT to use it (less work @ circuit design + less circuit cost). So i just want to know what effect does it (OPA365) have on the circuit (especially in my case) ?

Your helpful comments and suggestions would be appreciated.

Thankyou!


texts: Difference between radiated and conducted emissions?

texts: The company I work for needs FCC certification for an electronic product we are designing. I have watched a couple of YouTube videos on the subject but I’m not clear about the difference between the conducted and radiated emissions tests. If someone could explain the differences that would be great.


texts:
Just a general question about voltage graphs for first order circuits.

For example in this circuit:

The graph of v(t), the voltage across the capacitor may turn out to be something like this (values not correct)

Would the voltage across the 6k resistor be the opposite of this graph? For example if the values in the graph were correct would it start at -9V?


texts: How to choose the emitter resistor for a common collector configuration?

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This link feature a video starting at a specific time: https://youtu.be/t0UOSIUve9E?t=16m24s

For a common collector configuration, The teacher chooses the emitter voltage (output voltage) to be the half way between Vcc and gournd, Why?
Also, He does not explain why he choosed 5mA as a quiescent current?
What considerations should I take care of while choosing those values?
If I'm using PN2222A transistor and I want to drive 8-ohm speaker as a load (audio amplifier).
What would be the values of emitter voltage and quiescent current ?

Datasheet:https://www.fairchildsemi.com/datasheets/PN/PN2222A.pdf


texts: Why Vin should be above Vout by a Vbe in LDO using NPN?

texts:
This is a description of LDO in Switch-Mode Power Supplies Spice Simulations and Practical Designs by  Christophe Basso.

I am wondering if there is any mistake here. The author said that for linear regulator using NPN pass transistor, Vin shall be above Vout by a Vbe, at least.
I don't understand why. I think it may meant to say the base voltage should be about Vbe above Vout instead.
Can someone explain?

  Figure 1-2 finally shows how our resistive converter could be improved, let’s say for the 5 V section. The error amplifier is made via a voltage-controlled voltage source (E primitive) and features a gain of 10k (or 80 dB). One of its input receives the voltage reference whereas the other one, the inverting input, is biased by a portion of the output voltage. This is actually a linear regulator, however, limited in the input voltage range since Vin shall be above Vout by a Vbe, at least, to guarantee a proper drive for Q1. If Vout
  is below the target (5 V in our example), E1 output increases and strengthens Q1 bias current: Vout goes up. On the other hand, suppose the load has suddenly been reduced, therefore Vout exceeds 5 V. Thanks to E1, Q1 bias current goes
  down, reducing the output voltage until regulation is met again.