texts:
I'm an Electric Engineering student and I have my first lab tomorrow. One of the questions in the prelab asks you to give the scales and the range of each scale in your multimeter. Here's mine

I want to know if the range is something like 20 – 200kΩ for the 200kΩ scale and then 0,2 – 20 MΩ for the 20MΩ scale or 0 – 200kΩ for the 200kΩ scale and then 0 – 20 MΩ for the 20MΩ scale.

I know it's something super basic but the information I have is very vague. Thanks for your help.

EDIT: Woah! Thank you all for your time and knowledge, it's a shame I can't even upvote.


texts: Implementation of D (differentiation) in PID

texts:
I am implementing a PID controller for motor speed control. I am done with implementing the PI control and it works perfectly fine for me. In the specification I have been told to implement a filtering technique by using the following equation for the D part:

Now what I understand so far, is that s represents "dx/dt" generally which corresponds to the rate of change of error, but here I can relate it with the rate of change of feedback. Td/N is for limiting the overall gain output (hope I got this right).
Now to represent this in terms of C code, I tried the following way:

        s = (CurrentFeedback()-Old_Feedback)*100/(MaxFeedback()); //to calculate the % change in feedback
        s = s*1000/sampleTime;      //1000 is multiplied because sampleTime is in milliseconds
        D = (Td*s)/(1+(s*Td/N));
        D = D*KP;   //Kp is multiplied as per the standard pid equation.

        Old_Feedback = CurrentFeedback();
        PID = P+I-D;

Well the results by adding D are not what I have predicted.
I just want to know if I implemented the D portion equation correctly? Am I making any mistakes in my understanding of the basic maths of differentiation?

NOTE: I am not in liberty to change the recalculate the kp,ti,td as it comes directly from the VFD.


texts: Most efficient way of creating a bool array in C - AVR

texts:
I'm using an Atmega32 to read various sensors using its ADC.

Using digital logic and a few multiplexers, I've multiplexed the entirety of PORTA, using PA0:6 for address and PA7 as the input. Therefore, I can have a maximum of 128 inputs from just a single PORT.

Now, since the user will be operating the system via a computer (using RS232), it'll be possible to add or remove sensors, so the system must keep track of which addresses are free to add sensors and which addresses to read from.

I was thinking of using a 128 bit boolean array as flags to indicate if there is a sensor at a certain address.

While C doesn't have native support for single bit variables, it is possible to use bitfields to pack together up to 8 "bool variables" into a single unsigned char.

So, I've created the following struct:

typedef struct bool_s{
      uint8_t bit1:1;
}bool_t;

Then, I created a array of type bool_t with a size of 128, hoping that everything would be nicely packed together, but sizeof() tells me that the array size is 128 bytes instead of the 16 bytes I was expecting.

Technically, I could create a single struct with 128 1 bit variables:

typedef struct Flag_s{
      uint8_t F1:1;
      uint8_t F2:1;
      uint8_t F3:1;
      [...]
      uint8_t F128:1;
}Flag_t;

The problem with this approach is that while it does reduce memory usage, it's not very practical to use and it occupies way too much real estate in the code.

Is there any easy way to create a huge amount of flags or am I asking for too much? I mean, it's not like saving 112 bytes is going to make a big difference when you have 2K available, but what if I needed even more flags?


texts:
Why does LVDS (or any differential signaling for that matter) use a common mode voltage of 1.2V instead of 0V?

Is there an easy way to shift the common mode voltage to 0V?


texts: Electromagnet Polarity Reversal Doesn't Matter?

texts:
I am working on an engineering design project for school which uses the electromagnet linked below to "lock" a door. The problem is that the electromagnet remains energized or magnetized even after turning off power to the coil. I believe this is because the core of this unit is tool grade steel and not soft iron so a magnetic field is induced while the magnet is powered on and is retained in the material after it is powered off.

My plan to counteract this behavior was to reverse the polarity supplied to the electromagnet for a short period after powering off the lock which would hopefully "release" the other side of the door lock. Unfortunately, even physically swapping the leads to the electromagnet does not change the direction of the field and it is not reversible. I don't know if there is an internal rectifier in the magnet or if the physical windings in the coil do not allow for a reversal of the field. Is there something I can do with the circuitry to counteract this or should I shop for a dual coil electromagnet that can be reversed?

Thank you!

https://www.amazon.com/uxcell-Electric-Lifting-Electromagnet-Solenoid/dp/B01NASKR8D


texts: Do I need decoupling capacitors when I'm PWMing an LED?

texts:
I'm a hobbyist (well, less than a hobbyist really) trying to layout my first PCB design.  I'm somewhat familiar with the concept of decoupling capacitors.  I'm fading 3 LEDs in and out (really, it's an RGB LED and I'm trying to create blended colors).  I'm using ATTiny's PWM pins to accomplish this.

I'm planning to add a 100nF ceramic disk capacitor between the VCC and GND on the IC, but I'm not sure if I also need to decouple the LED signals.  If so, do I put them close to the LED or close to the IC?  What size caps do I use?


texts: Estimate nominal values of a brushed DC motor

texts:
Is there a good rule of thumb for guessing the nominal values (torque and current) of a brushed DC motor if you know its stall values?

I'm estimating parameters for a small DC motor (~5-10 W). When I look at datasheets for motors of that size, I see continuous values of around 20-30% of the stall values. Is this a good approximation? Or how would you do it? Does this hold true for larger motors as well?


texts: Arduino LED dimmer with IR remote control

texts:
I want to make an LED dimmer with IR remote control using Arduino, by pressing each number in the remote control give different luminescence for example number 1 give 10% duty cycle and number 9 100% duty cycle.
I tested many codes but all them don't work, i have following code,
 can you help me why it doesn't work?

#include <IRremote.h>

int RECV_PIN = 11; // the pin where you connect the output pin of TSOP4838
int led = 3;
int brightness = 0;

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
{
Serial.begin(9600);   // you can comment this line
irrecv.enableIRIn();  // Start the receiver
pinMode(led, OUTPUT);

}

void loop() {
if (irrecv.decode(&results)) {
unsigned int value = results.value;

Serial.println(value); // you can comment this line
analogWrite(led, brightness);
if(value == 6630){
  brightness=25;
}

else if(value == 2550){
   brightness = 255;
}
  irrecv.resume();

}

}


texts: Whenever two system or sources are coupled they should have same current sink or common reference point (say ground). How to realize this in ECG?

texts: Electrode (Ag-AgCl) are placed at different part and directly fed to positive and negative input of differential amplifier. How can we realize human body and amplifying system have same current sink or common reference point(say ground)?


texts:
I'm planning to use the MCP1825 LDO regulator to be used with a 3.7V LiPo battery to power up a circuit with 3.3V requirement (microcontroller + ESP8266). However, I'm confused with which package to go with.

MCP1825 comes in a SOT223-3 and SOT223-5. The later offers two extra pins: Shutdown and Powergaurd. I'm not able to comprehend the datasheet as to why these two extra pins are provided.

Does it mean that once my battery voltage is below certain voltage (such as 2.7V), it will shutdown regulation and prevent over discharge? If yes, how do I set that limiting voltage? Should a SOT-233-3 package be sufficient to provide 3.3V regulated output?

Datasheet Link


texts: How can I tell which alternative is used in PoE?

texts:
I need to disable the power over ethernet being output by a device to prevent any damage to routers and switches. After looking more into how PoE works, there appears to be two alternatives to how the power is sent over the wire.

Alternative A - Uses phantom power. This method involves sending power alongside the data signals since they are at such different frequencies.

Alternative B - Uses the unused wires of a 10/100 cable to send power.

I'm not certain as to whether the device is 10/100 or if it supports gigabit connections. If there is a way to discover the gigabit capabilities that would tell me that it cannot be alternative B. I don't have many details on the hardware, as it's part of a larger system.


texts: How to suppress voltage spikes caused by USB fan on ATX 5V rail?

texts:
I bought a cheap largish USB fan and plugged it in to the 5V rail on my adapted ATX bench power supply. Immediately, the ATMega328P that is present on the adapted ATX supply started to act erratically. The '328 is there to measure voltages and currents and to drive 7-segment displays and it is powered out of the same 5V rail. (picture and schematics are at the end of the post).

I checked the 5V rail with the oscilloscope (screenshot below) and, to my surprise, the fan was causing the rail voltage to spike up to 6.3V at 160Hz. That's way past the poor '328 absolute maximum 5.5V supply voltage.

I know what is causing me problems, but I don't know why or how to fix it. But I thought I should learn something from this. My questions then are:

1. What is likely the cause of those spikes?

My guess is that the problem comes from the inductance of the motor coils. When the commutators loose contact with the brushes, the current through the coils is suddenly interrupted, and according to the inductance formulae \$V = L \dfrac{di}{dt}\$, there's an increase in voltage to counter it. I hazard a guess that the frequency I measured (160Hz) is double the fan RPM (I'm guessing 4,800RPM).

Am I in the right direction? The only thing that doesn't add up is that I think the spike should be negative (same signal as \$ di \$), not positive.

2. Based only on my oscilloscope readings, can I consider that the fan design is flawed? If so, what circuitry is likely missing on the fan, that would otherwise prevent those voltage spikes from happening?

My guess is that the voltage spike is something that all brushed DC motors produce by design, but additional circuitry (possibly filters) are put in place to suppress its effects. But I don't know what these filters would be.

3. How can I improve the design of my adapted ATX bench power supply to protect it from such voltage surges?

Is this a case in which a flyback diode should be applied?

The fan is 1.5W (2.5W start up power). I have two other smallish USB fans (1W) that do not produce any spikes like that.

ATX power supply adapter schematics:

My adapter plugged to the ATX power supply in the background (they are actually two separate units), and the fans.


texts:
I know it's important to protect analog and digital inputs. My question is should you also protect outputs, both analog and digital?

For the inputs, right now I'm using clamping diodes, an MOV, a series resistor, and a series ferrite bead for high frequency noise rejection.

If outputs should be protected, how should this protection differ from inputs?


texts: What's the relationship between chips, wafers, and dies in a computer?

texts:
I have the following question:

If your demand is 50,000 RedDragon chips per month and 25,000
Phoenix chips per month, and your facility can fabricate 70 wafers a month, how
many wafers should you make of each chip?

Note: info about the die and such where given before and we calculated the amount of dies per wafer in a previous question, profit for each chip was calculated as well.
What they did is divide 50,000 and 25,000 per the amount of dies per wafer and got the amount of wafers needed I don't understand why.
From my understanding is that every chip is made of a wafer which has a lot of dies, if that is case case why don't we have 1 wafer for each chip, what am I getting wrong? Would appreciate you explaining the general picture and relationship between these three.


texts: Bit error rate calculations for a photodiode receiver driven from a laser

texts:
I'm having problems understanding how the following specification for a photo-diode (with built-in amplifier) rationalizes the bit error rate: -

Circled in red are two important figures. One is NEP (noise equivalent power) and the other is minimum receivable sensitivity. The way I figure it works is like this but please correct me if I'm wrong: -

NEP is typically 310nW and note 3 says this is for a single-ended measurement and therefore I assume that for the diff outputs of the device, the power is doubled to 620nW. From this I conclude that the noise voltage out is sqrt(50 x power) = 5.6mVrms.

Next is the minimum receivable sensitivity of -25.5dBm. Laser jargon talks about a 10dB extinction ratio which means that the logic levels transferred via light are 10dB apart so I naturally assume that -25.5dBm is for logic 0 (dimmer) and -15.5dBm is for logic 1 (brighter). These, in mW terms are simply 0.0028mW and 0.028mW.

Now, if I look at photo sensitivity, this tells me how to convert these to voltages. The figure quoted is single-ended and therefore light powers convert to 4.2mV and 42mV respectively. These double up because the output is differential to a peak to peak output of 76mVp-p.

So now, I have rms noise (5.6mV) and p-p signal amplitude (76mV)

Here is where I may also be going wrong. I can convert the noise to a p-p value by assuming it is Gaussian and, for instance if I used 6.6sigma (99.9% "coverage"), the rms voltage becomes 37mVp-p. This is approximately 50% of the signal p-p amplitude and as far as I can tell will be high enough in amplitude to produce bit errors.

Any smaller than 50%p-p and it isn't quite enough to do bit-damage. I used 6.6sigma and this means the noise signal is below 37mVp-p for 99.9% of the time. For those occasions it is greater than 37mVp-p, 50% of those times the amplitude of the symbol may be enhanced and 50% of those occasions the symbol will be destroyed. I therefore conclude that the BER rate is 1 in every 2000 bits.

However the spec (in the picture) says BER = 10^-10 and this is totally at odds with my calculation.

My calculations suggest a bit error rate of 1 in every 2000 and the spec suggests 1 in every billion.

Where am I going wrong?


texts: How much is the current consumption of this sensor (tmp102)?

texts:
Here is the data-sheet.

I just want to know how much time it takes to measure the temperature and how much current it consumes. I struggle when trying to find such info in the data-sheet so any help would be appreciated!


texts: Autodetection of presence of internal CT burden on plug-in CT

texts:
I am going to measure 3 phase energy using CT from YHDC model SCT013-000 (100A:50mA) and SCT013-100 (100A:1V). I have a board which is done in my company and my job this moment is make a shield board for this main board which have as uC an ESP8266.1

When I plug a CT on KRE2 (terminal block), I need a circuit that detects if the CT has an internal burden inside or not to switch for the right circuit.

In the CT1 (100A:50mA) there's no burden inside, so I need an external burden to have a closed loop.
In the CT2 (100A:1V) it already has a burden built inside then I just need offset circuit for ADC.

I was thinking about comparator but I don't know if that is going to work. That's where I need help. I need something analogous to a switch between SW1 or SW2 depending on which CT I plugged on KRE2.

Thats what I need help, please.

If someone have a better idea for circuit topology let me know too, if I can reduce components, for instance.

1 Well, the ESP ADC isn't good enough for what we need but it's a firmware guy deal, not mine so much, and we will use the A0, A1 and A2 analog input from ADS1115 to measure current using these current transformers, because it has better resolution. I will leave A3 pin from ADS1115 open (no connect). It is for a specific application, which is just measure 3 phase current.


texts: Assembly of PCBs containing a mix of SMT and thru-hole parts?

texts:
I have a batch of beta PCBs which we have to assemble in our lab. We have an APS manual pick-and-place machine and a tabletop reflow oven so I thought assembly tomorrow would be easy and straight forward until our technician bought up a point.

The PCB to be assembled has a mix of both through-hole and SMT parts. We'd planned to place and bake all of the SMT components first, and then hand assemble the through-hole parts. But out tech is concerned that in reflowing the SMT parts some or all of the through-hole footprints might close up. This is our first attempt of an in-house build so we are looking for how others may have approached a mixed build.

If the through-hole parts can all tolerate the reflow heat curve we can add them to the PCB and reflow all of the parts at once. The through-hole parts would essentially keep the holes from filling, but if they did no harm would be done. Of course, the through-hole parts would still be hand soldered after reflow. Is this a reasonably good approach?


texts: Input impedance of grounded emitter amplifier with DC feedback

texts:
In AoE3 2.3.5.C (page98) it states the following (referring to the circuit in the image):

  For instance, feedback acts to reduce the input and output impedances. The input signal sees \$R_1\$ resistance effectively reduced by the voltage gain of the stage. In this case it is equivalent to a resistor of about 200\$\Omega\$ to ground (not pleasant at all!)...

The intrinsic emitter resistance \$r_e\$ is \$\frac{V_T}{I_E} = 25.3\Omega\$ (with \$V_T \approx 25.3mV\$). Only \$R_2\$ and \$r_e\$ are "to ground" so \$R_1\$ does not play in the part. So \$R_{R2||(\beta*re)} = 1844\Omega\$ (with \$\beta \approx 100\$), and hence the signal input impedance. I can't understand how input impedance is reduced to 200\$\Omega\$ in this grounded emitter amplifier circuit with DC feedback.


texts: current flow from positive to positive between batteries?

texts:
If you have two batteries with different voltages, let's 12 and 9 volts and you connect the negative terminals while you put a LED or whatever between the positive terminals, there will be current flow. I reason that is because there is a potential difference even thought both terminals are positive. However I'm not sure I understand how electron current would work here.

If there is current then that must mean that electrons actually flew out of the lower positive terminal into the higher one? is that what's going on? if not, could someone clarify it?


texts:
I have an ATtiny85 and I'm trying to set the clock to 8 MHz.  I have read the data sheet and some discussions on how to do this but am not having any luck getting it to work.  I have included my code and any help will be greatly appreciated.

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

int main(void)
{
    cli();
    CLKPR |= 1<<CLKPCE;
    CLKPR |= 0;
    sei();

    DDRB |= 1<<PINB1 | 1<<PINB0;

    TCCR0A |= 1<<WGM00 | 1<<WGM01 | 1<<COM0B0 | 1<<COM0B1;
    TCCR0B |= 1<<CS00;
    OCR0B = 240;

    TCCR1 |= 1<<PWM1A | 1<<COM1A0 | 1<<CS13 | 1<<CS12 | 1<<CS11 | 1<<CS10;
    OCR1C = 255;
    OCR1A = 127;

    while (1)
    {
    }
}

I do not have a scope, so I'm not able to determine what the frequency of Timer0 is but I know that Timer1 is running at around 61 Hz (prescaler = CK/16384) because I timed the blinking of a led. That would mean that the CK is still at 1 MHz.  Not sure what I'm doing wrong here.


texts: 22J 6KV and 33J 6KV are two kinds of ceramic cap that seems to be burned out. What do I replace it with?

texts:
These capacitors are located in power supply module DPS-279BPA section where it is marked with high voltage area. It is a Phillips LCD televisionPhillips 37PFL5603D/10 with no picture and audio, Though it shows the power light in front panel. After I opened the back lid and noticed that these 3 capacitors turned black. Not sure if damaged or not. Other similar cap are still blue in original color. Not having multimeter and ESR I am not able to test these these out.
I guess replacement parts will cost less than the multimeter or other measuring devices so thing to just find the replacement part and replace and see if really needed go for other options.
I hope I am not in a wrong place, I am sorry that I could not be detailed than this!

 I tried to search the actual part specifications as suggested but was unable to find appropriate no. I have uploaded the some more pictures hope helps. The Manual suggested looks similar.


texts: Need help with instrumentation amp behaviour

texts:
I was wondering if someone could help me understand why this instrumentation amp isn't working the way I think it should. The amp is an INA155.

My intention is that at if a voltage (positive or negative) is applied across the input pins, I should see the same value, multiplied by 10 (since this amp has a gain of 10) at the output pin, relative to the ref pin. I have a virtual ground using a 2.5V reference at the ref pin. I have some low pass RC filters on the input. Eventually I want to read the output voltage using an ADC.

I have the circuit in this picture bread-boarded:

I have the ref and output pin connected to a multi meter. I am powering it with a bench top supply. I haven't applied a voltage to the input pins yet, because I thought I would first test the offset voltage by measuring the output when the input pins are shorted together. It should show a voltage close to 0, with a small offset right???

What I'm seeing is the output voltage start at close to the rail (so I measure exactly 2.5V on the meter since the ref pin is tied to 2.5V),then it slowy starts to drift, over the course of minutes, until the voltage on the meter hovers somewhere around 200 to 300mV between the output and the ref pin. The stability increased since I added the low pass filter, but the output doesn't make sense (at least to me).

Can anyone explain why I'm seeing this? There is obviously some gap in my understanding of these amps. So far all I've worked with is a unity gain buffer. I'm just trying to design a simple buffer for measuring a signal, mainly DC, that can be bipolar.

Looking for any tips or help with this, or even a different approach to achieve the same thing. I am forced to work with a single 5V supply, hence the 2.5V virtual ground, but I need to measure both positive and negative voltage. I've tried this with added resistors from the input to 2.5V for a return path, but the output didn't change.

Thanks!!


texts:
Currently, I'm working on a Invidia Jetson TX2 dev kit.

I'm trying to power a 12V 2A LED from a 3.3V GPIO.
My current system uses a 12V relay with an optocoupler (generic Arduino One), but I'm trying to use a transistor instead.

Using FQP30N60L MOSFET without a load and a 10kΩ pull-down resistor.
Using 2N3904 for driving a 3V blue LED with a 390Ω  on 12V (and 10kΩ on gpio<>base)

Both scenarios show that GPIO voltage drops from 3.3V to 1.3v~1.8v when connected. Is that normal or am I doing something wrong?

It's not very clear what current can the GPIO supply, but from my understanding it's 1mA (could be wrong).

Thanks!

EDIT:
Thanks to 'amb' i understand my readings; thanks :)
So after reading some more i have another question:
GPIO port is an 'open-drain design' with 100k ohm internal pull-up (other GPIO ports have 20k and 47k), This port can provide 1ma of current.

What is the proper way of driving a 12v (2a max) LED using a MOSFET?

Note: i have added a simple drawing of my setup, i know it wont work, just trying so simulate my problem

EDIT 2: Internal pull-up is 100k ohm

EDIT 3: Is R2 needed here? as its an open drain with internal pull-up, pin wont be floating (i put it as i did in arduino, witch is not the case here)


texts: Current Ripple in Ceramic Capacitor Selection

texts:
I need to choose a ceramic capacitor (ESR<10mOhms, 5VDC) for my buck converter application, whose value should be around 300uF. The reason for going for a ceramic capacitor is the low ESR they have. Also my converter would be operating at 100kHz. Off course these capacitors can be placed in parallel (for eg three 100uF caps in parallel) to give equivalent capacitance as well as low total ESR.

Now the confusion is that the capacitors data sheets are very very vague. Vague in a sense that all of them don't give the ESR directly. While searching for it on the Google, I read a post on this website where this issue has been discussed that some caps data sheets give DF instead of direct ESR, and from that D.F we can calculate the ESR knowing the frequency at which the capacitor is operated.

Also some data sheets give the max ripple current and mostly do not. And this is the most confusing for me. How can i select the capacitor for my buck converter application (max 40A current)? I mean is this current ripple rating of the capacitor of my concern or not? As my thought earlier about selecting a capacitor was just keeping the capacitor value, the voltage rating and the ESR value in mind, but I'm not sure about that current ripple thing (which is not mentioned in most of the ceramic capacitors data sheet), if it is to be considered or not? Its been almost 3 hours that I am trying to find something suitable for my application, but unexpectedly I haven't found anything. Either the price is too high (more than 5$ for e.g), or the data sheet isn't providing enough information (some don't give ESR as well as D.F) and now I am confused about current rating (as this parameter also, is not mentioned in most of the data sheets).

Please help me out, you comments would be appreciated.

Thank you!


texts: Does the orientation of a Bluetooth antenna affect the transmission distance?

texts:
I'm doing a project with a Bluetooth device for the first time, specifically with a JY-MCU Bluetooth module:

As you can see, the antenna is on the green PCB, which is in turn soldered to a breakout board.

Does it matter what orientation the antenna is in? For example, I could set it flat on its top or back as shown in the above image, or I could also plug it in vertically.

Will changing the orientation change the receiver and transmitter distance?


texts: Charging 2 lithium batteries from 2 photovoltaic modules

texts:
I have 2 PV modules, each producing 3V, 100 mA and 0,6W. I want to use these modules to charge a lithium battery.
I know that I need to use a charger and I found this one based on the CN3065: https://grobotronics.com/solar-lithium-battery-charger-cn3065.html#group_1436660811b1c33c54-4
In the datasheets of this charger the tension that it needs from the PV module is between 4 and 6V. So I decided that I need to connect my modules in series in order to obtain more than 4V.
On the other side, I found for example 2 batteries of type 18650, each of 3.7V (connected in series).
The problem is that I don't think that my PV modules produce enough in order to be able to charge these 2 batteries. Is there any formula that I could use in order to know if my circuit would work?


texts: Turn on LED strip via PIR using NPN transistor

texts:
I have following circuit. Really simple. But I keep missing why I cant power LED strip (5V 1A). Falstad simulator says overflowing current. I am not very good at simple hardware thing. I often solving it via microcontroller which is not now suitable for solution small as possible.

Figure 1. Original circuit.

Figure 2. Update to match @Transistor's answer.

What do you suggest to have minimal working circuit?


texts: Smoothing out current spikes so three-phase machine doesn't exceed site's electrical supply

texts:
We are looking at installing a machine at one of our manufacturing sites that draws around 120A at 415V three-phase (we are in the UK) but the maximum current we can draw at our site is 100A before the breakers trip. We have some other equipment at the site as well, but its all much smaller so most of that 100A should be available.

The machine operates for around 5 seconds, and then does nothing for around 3 minutes while we change over parts. Is it possible to smooth out the current spikes somehow so the site's electrical supply can handle it?

I have found some information about peak shaving and load smoothing systems but they generally seem to be large battery banks for covering peaks with time periods of hours not seconds.

We have discussed increasing the electrical supply with the power company and unfortunately it is not possible without some major upgrades in the area.


texts:
I am building a power supply.
I made all my footprints and and my schematic library (if this can have an impact)

Briefly, when I import my change to my pcb board, none of my connection stays and I get a bunch of unmatched nets...

Here is my schematic:

If anyone could help, that would save me. It's been 2 evenings i'm trying to work this out...

THANK YOU

Thank you for your response.

I have tried to recompile and I didn't get any error.
Here is what appeared when said "no" to matching nets automatically and executed the changes:

It says Unknown pin..., is there a way to modify that?


texts:
I have a question about the amplifier with circuit shown below:

I don't understand if this is a voltage or a transimpedance amplifier.
Can someone provide some explanation?


texts: How do I safely power 2m 144 LED/m WS2812B strip with 5v and 10a?

texts:
I am using a 2 meter strip with 144 led/m on a WS2812B led strip. By doing the maths on how much current would be required to power this we get
60mA * 288 = 17.28 amps.
However, I am not planning on having the LED's at full brightness and I do not plan on having any white LED that will draw more current. I will have the LED's at 40% brightness so I would need ~7a. But once again this would be if the LED was white.
So with these numbers, I bought a 5v 10a power supply. The schematic that I am using is attached to this post. It is from the NeoPixels uberguide, in the section "Powering NeoPixels". I have also attached a picture of the connections that were already wired up on the LED's.
I am completely new to any sort of circuitry especially at these high currents and to be honest it scares the crap out of me worrying that I will completely burn down my house!
So here are my questions:

I am currently using the Arduino Uno starter kit along with the included jumper wires. From looking up online I can see that the gauge of these wires is 22 AWG which I believe is not suitable for the ~7a that I need (Please correct me if I am wrong). So I know I would need to get better wires, however I am not sure what gauge wires I would need?

If I was to get different wires, for example 16 or 14 AWG, are they available as jumper cables and will they fit into the Arduino pins?

My LED strips have 5 wires coming off of them already, two red, two white, and a data cable. One of each of the white and red cables a long with the data cable, go to a female connector that I plug the jumper cables into. Would I be able to plug the bigger cables into this connector and are these wires suitable to handle the current or do I need to unsolder them and re solder new wires?

I also bought a barrel jack adapter that splits the power supply into the + and - connections. I believe it is called a 5.5mm x 2.1mm adapter. The brand is EFISH and once again I am wondering if this can handle the current?

As you can see from the schematic, there is a 1000uF capacitor on the + and - from the power supply, I then connect the wires to the LED as well as the ground to the Arduino. What is the best and safest way to cover all of this once I am done testing and ready to install?

Finally, I know that it is suggested to power both ends of a strip to ensure equal brightness and colour accuracy especially across 2m of LEDs. The end of my strip has the same wires already connected however, instead of the female connector, it has a male connector. How do I power this end of the strip? Do I simply wire the white and red cables into the same power supply as I did with the other end?

I know there are a lot of questions here but I am very excited to get this working but mainly I am very nervous about all of it! So any help or input would be greatly appreciated!

owjo


texts:
I recently started studying STM32 microcontrollers (BluePill STM32F103 dev board + ST-link V2 clone). I was wondering if it is possible to add serial communication to ST-Link clone?
From what I understood, those clones are copied form ST-link schematic of official Nucleo boards. The ST-link on Nucleo boards is build with STM32F103CBT6 and pins 12 and 13 (PA_2 and PA_3) are used as TX and RX for serial communication with target microcontroller (and connects to PA_2 and PA_3 pins of targer). See page 65 of official Nucleo documentation
Meanwhile, on ST-link clones those pins are floating and not connected to anything

If I solder 2 wires to pins 12 and 13 of STM32 microcontroller on ST-link clone, would I be able to use those for serial communication with target microcontroller on BluePill board (PA_10 and PA_9 or PA_2 and PA_3)?
UPDATE:
Looks like specifically this ST-link clone is made based on schematics of ST-link on old Discovery boards like this:

In this "configuration" in can't be converted into ST-Link with Serial port feature, since this feature (as Virtual Com port) was added in ST-Link V2.1 on Nucleo boards and has another schematic:

FINAL UPDATE
The topic is not relevant anymore. Recently STMicroelectronics released STLink V3 Mini with very affordable price and same functionality (SWD + VCP) which I bought.
Now it can be bought at about $10


texts: Is it safe to run these motors with raspberry Pi directly?

texts:
I got this RC car today. It's the cheapest possible model.
I want to make a raspberry Pi project with it (which has its own 5V supply from a power bank).
Is it safe to directly power the motor with the raspberry Pi ? Should I connect a resistance in series first to the motor? If so how much should be the value of the resistance ?
Kind of how we run LED experiments with raspberry ?
Current setup (it came like this) has 3 X 1.5 V AA batteries as input. And it runs pretty fine.


texts:
I'm currently trying to figure out the best way to make use of my gas gauge LTC2943-1 in conjunction with my pack of NiMH batteries. I am aware that voltage alone is not a sufficient measure of the SoC of a battery, so I am trying to make use of the gauge's coulomb counting ability. Unfortunately I am not clear on a couple of things.

1) When should the fuel gauge be set?
From my understanding, it should be set after a full charge has completed. Does this need to be reset every time a full charge has occurred though? Because batteries are dynamic, and don't necessarily accept the same amount of charge all the time, and because batteries tend to lose capacity over time, is resetting the gauge after each full charge the best way to get an accurate read of SoC?

2) What is the best way to calculate/figure out the "low end" of my gauge?
Currently I've just been waiting for my device to reach a state where it can just power on, and then capturing the coulomb count at that point. The value attained for one unit, may not necessarily be applicable though to other units as their full charge counts could be different. As such, what is the best method for determining this value?


texts: SIM7020G nb-iot module interface with esp32

texts:
My code at the moment is to connect esp32 to MQTT server via wifi and its working completely fine.
The next step is to use sim7020G NB-IOT module to achieve the same connection but as I have never worked with Sim modules before, Can someone here give an overview of how this can be done? If any of you can share any tutorial or guide it can solve my problem. I couldn't find any tutorial on the internet.
Thanks


texts:
I am looking for a language that can declare a circuit board, and then draw it in schematic form or whatever. Can you tell me if such a thing even exists?

The common "language" people use to design circuit boards is some graphical tool like Eagle, KiCad, Altium or any of the plethora EDA packages https://en.wikipedia.org/wiki/Comparison_of_EDA_software. I am looking to create a text file instead, that will be processed and generate as output one of the EDA file formats.

Detailed explanation:

For example in the world of computer cloud infrastructure, there are several declarative languages that are used to define resources and create them. HashiCorp Terraform, AWS CloudFormation, OpenStack HOT, Azure ARM Templates, and more.

For example, if I need to create a circuit that has a battery, IR receiver, IR transmitted and an Arduino. Using this language I would just define which pin of each device needs to be connected to which other pin - and the output of the language can be a graphical representation of the circuit. As-if I designed it in KiCad or some other EDA.

One example for automatic dependency resolving is Graphviz. For example using Graphviz I can create a text file where each component is listed, along with all the dependencies and it creates a graphical representation from this in some graphics format (svg, png, ...).

Example Graphviz dot notation file
https://gist.github.com/kesor/2b858d218a25d22f27eefb780c6b1a17

When rendered it looks like this
http://imgur.com/a/kiUR2


texts: Why are two different length antenna sold with this 433MHz module?

texts:
I've stumbled upon this module. It is a set of receiver and transmitter module at 433MHz.

This shows the antennas:

With the lengths being given as:

"external antenna: 25cm ordinary multi-core or single-core line" (transmitter)
"External antenna: 32CM single core wire, wound into a spiral" (receiver)

What is the rationale behind this? As far as I understood it (only basic knowledge), a different length of the antenna causes a different resonant frequency.

For example, if you use a LoRa module at 868MHz, Adafruit recommends a 8.2cm long "quarter wavelength" antenna. Since λ = c / f, here λ/4 is ca 8.63cm, which make sense (slightly longer but maybe they're accounting for something else?).

For this product I don't see relation since 25cm and 32cm don't have a nice factor between them (like one is λ/4, the other λ/2).

Why is it that it is apparently better that the receiver has a longer antenna than the transmitter? Where do the antenna lenght numbers come from?

Btw, I've read this question, which however doesn't give insights on why there are different length antennas.


texts:
I am using an ADS1115 as an analog to digital converter to measure temperature. I am using an RTD100 temperature sensor to measure a temperature range of -40 to 150 degree celsius but the resistance vs. temperature table of the temperature sensor is non linear.
How can I convert the temperature range of -40 to 150 degree celsius
to a proportional voltage of 0-5V so that I can measure it with an ADS1115?
Temperature vs. resistance table of RTD100:

This is a reference circuit to which an RTD100 is connected.  It converts the temperature range of 0-200 degrees celsius to 0-5V but I want to design a circuit that converts (-40)-150 degree celsius to 0-5V.
How should I calculate the resistance values connected to the opamp?


texts: What is the relation or advantages or reason about these advantages of bundled conductors?

texts:
The book show me the advantages of bundled conductor

Decrease the loss from electronic corona
Decrease the reactance and voltage drop and increase the efficiency of power transmission
Decrease the interference from wireless communication
Decrease the potential gradient
Decrease the surge impedance

In my thinking ,there is a relation between 1. and 2.

Relation between 1. and 2.

  because bundled conductor can decrease the loss from electronic
  corona, eactance and voltage drop, so of course it can increase the
  efficiency of transmitting power

Relation between 2. and 3.

  because it can decrease the reactance, so it can also decrease the interference from wireless communication

I want to ask :

Why can the bundled conductor decrease the loss from electronic corona,is it because it is bundled?
Why can the bundled conductor decrease the reactance?
Why can the bundled conductor decrease the potential gradient and surge impedance? What is the advantage about them? Does it increase the efficiency of power transmission, decrease the current or something else.


texts:
I am having trouble actuating this relay I bought off Amazon. I have been successful actuating the relay but am having issues wiring up a LED to simply turn on and off. My setup looks very similar to this (see attached) with two modifications, running it off an Arduino Uno and wiring up the JDVcc and GND to a separate 5v power source(set of pins that normally have the jumpers attached). Here is the relay I bought:
https://www.amazon.com/gp/product/B072BY3KJF/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

LED on the breadboard is not illuminating at all, however the relay is actuating and making a click. The status led built into the relay does light up accordingly, indicating I have an issue with the high voltage/current side of my wiring.  Any help would be greatly appreciated! Thanks.
-Mike


texts: I keep getting an error in OrCAD using a certain op-amp

texts:
I keep receiving this error in OrCAD. I am trying to use an LM741 operational amplifier for my schematic but am unsure why I can't open it.
Error:

Placing symbol instance for Model LM741 failed because in Demo mode Library path opamp does not exist

Here is the circuit:

I need to use the LM741 op-amp but maybe there is another op-amp that will produce the same results?


texts: How to change Bluetooth music receiver's name and other settings using a serial converter (or otherwise)

texts:
I'm rather new to electronics but I have a fundamental grasp of the general concepts. I'm not very fluent, however, on the workings of specific devices as of yet (internally, I mean; inside their little brains).

I bought several cheap but amazingly good USB Bluetooth music receivers for several music outputs at home. Obviously, I had thought about the issue with having them all named the same and not being able to tell which is which upon trying to connect to a specific one. But I guessed that I would be able to solve that later in a simple way. I since realized that manufacturers give no option of this, even when the names of their apparatii are so little allusive such as H-163 or PT-810! And searching online I have only found two threads that ask this question (amazing!); one has the sole response: "NO, impossible" (which I always tend to question as a response); the other links to this explanation:

Bluetooth configuration

So I went online and bought me a USB To TTL Serial Converter:

USB to serial converter

According to this set of instructions, all that's needed is the serial converter connected to the computer. Not the Arduino. Although I think there probably is a way of going about this through the Arduino. Anyway, I disconnected my Arduino and proceeded to connect everything as you see in the photos (and as is instructed in the link above).

VCC on the BT receiver is connected to VCC on the serial converter. GND to GND. TX is connected to RX. RX is connected to TX. As per instructions.

Now, everything should be working according to what I've read in the above link. As you can see, at least both devices are receiving power and the serial converter is being recognized by my computer and by the Arduino EDI as being connected to a port. As it does seem like the above instructions are talking about a normal BT receiver, this should be a cinch; however, when I go through the AT test in the Arduino EDI Serial Monitor, I get no response. I've tried with all available Baudrates. I've tried switching the RX-TX cables to see if I had got the wiring wrong. I've also tried moving my connections up and down the breadboard just in case there was a dead row. Nothing: is the final answer.

At this point I've no clear idea as to what may be going wrong. Is my serial converter not working properly? How could I test this? Do these BT receivers have no real RX-TX connections? It seems they do, as I've already vivisected one, you can see it here:

(Yes, I have also tried connecting this franken-BT-receiver; as well as two other receivers and still no response. And yes, I did muck up the audio output on this one: my soldering wick was out and I tried desoldering the audio jack the brutish way and what I did was strip off the copper paths! I had to somehow undo this muck-job and this ugly beast is the result. Although I assure you it works 100%! It's the best receiver in my arsenal!)

And, therefore, it stands to reason that these are working RX-TX connections. This last again is evidence to me that configuration of these little devices should be possible, as in practice the USB port is only used to draw power, as there is no data transfer involved (these things work on a computer's USB port just as they work connected to a USB to power-plug adapter), so it only makes sense the manufacturer would hook up the RX-TX terminals in order to be able to communicate config. date from and to the device once it is fully built.

So I'm wondering what I'm doing wrong. Or if perhaps there's another way of changing the name on these devices. I'm sure there HAS to be a way of doing this. I'm amazed more people don't want to do it. But, anyhow, I'm glad to add another thread on this issue out there, because I'm sure at least someone else is or will probably want to do this at some point. And if I can get a positive answer on this, then now there'll be a source for everyone to find an answer to this question.

I thank you all in advance for your input! I'm sure it will be very useful and will help me understand these devices a little more!


texts: Can a Z84C00 CPU directly drive 74HCxxx series logic?

texts:
I'm getting confused by the datasheet for the Z84C00 CPU, while trying to work out if I can use it to drive 74HCxxx chips, or if I need TTL-compatible logic (i.e. either 74HCTxxx or 74LSxxx).  It's clear that the low level voltages are compatible, but I can't work out what's going on with the high level voltages.

74HCxxx chips require between 3.15V (at VCC = 4.5V) and 4.2V (at VCC = 6V); I don't expect my voltage input to range this far (I plan on keeping it between 5.2V and 5.5V).

The output for the Z84C00 is specified in its datasheet (p34) as:

Symbol    Parameter                   Min  Max  Unit  Condition
VOH1      Output High Voltage         2.4        V   IOH = -1.6mA
VOH2      Output High Voltage       VCC-0.8      V   IOH = -250uA

This seems to suggest that the voltage varies dependent on the input current on the pin, but isn't the input current entirely dependent on the internal circuitry of the chip itself?  How can I work out what the expected voltage of the output will be?

I'm also not sure what the subscript "1" and "2" in the symbol name here is used for.  I can't see any reference to them elsewhere, and the equivalent NMOS parts don't use the subscripts, just giving a single line (with 2.4V output level).  How should I interpret this?


texts: Constant current source with high Vce voltage

texts:
At the moment I implemented a current source with two FMMT560 for about 1 mA. These types allow -500V Vce. I expect startup peaks of 520 V which is too much. Are there any current sources which use PNP types but split Vce over two parts? I think I have to use four transistors for this.

Edit1:
Now I used the comments to produce a circuit like this and simulated it. . The problem is that Vce over Q1 is not decreased but that is what I want.


texts: Should I use a passive or an active filter?

texts:
simulate this circuit – Schematic created using CircuitLab

I need to design an am receiver as a project. On the front end I have three modules; BPF1 the "roofing filter" or the "pre-select filter", BPF2 to further "protect" the demodulator, and an RF amplifier between these two filters. Should my filters be passive or active?

The block diagram above shows what I am designing.


texts: Struggling to figure out why this capacitor voltage is huge

texts:
As you can see in this image from simulations on Matlab-Simulink:

I'm tracking the blue signal (reference current) using this circuit

Which is in this 400 kV HVDC link as "Snubber".

So basically the idea is to charge and discharge this capacitor inside the snubber circuit to track the triangle reference current, but the thing is that I don't know why there's too much voltage across this capacitor. If I'm correct, the snubber will always see the difference between 12-pulse rectifier output voltage and HVDC Link voltage, and this difference should be a bit closer than 1 million volts.

Any comment on this would be appreciated!


texts: MC1496 can be used as a DSB SC and AM IC, but their circuits on the datasheet are the exact same. What is the difference between the two?

texts:
I am looking at the MC1496 IC datasheet provided by ON here.
Figures 1 and 3 show that you can make an AM or DSB-SC signal using this circuit. However, the two test circuits listed on the datasheet for the two are the same circuit:

My question is, how can I implement one versus the other? I have followed this circuit schematic, intended to create a DSC-SC circuit:

When using the message signal as 8mVpp at 200 Hz, and the carrier as 2Vpp at 20kHz, the resulting output is an AM signal instead of a DSB-SC signal.

Does anyone have any suggestions as to why this might be happening, and if so, have any suggestions for implementing a DSB-SC circuit instead of an AM circuit using this chip?


texts: Can a Solenoid be driven from one of the pins of a Servo controller?

texts:
Would it be possible to operate a solenoid (e.g. this Plastic Water Solenoid Valve - 12V - 1/2" Nominal, suggested for use with "a TIP120 or N-Channel power FET with a 1N4001 kickback diode to drive from a microcontroller pin.") from one of the pins of a Servo Controller (e.g. this Pololu Micro Maestro 6-channel USB Servo Controller)?

Or am I overthinking it- for my solenoid ought I just use whatever relay I need on top of a simple breakout board such as this:


texts: Need an expansive collection of schematic symbols

texts:
I'm trying to get into conponent level board repair, and to do so I need to have a good understanding of electronic symbols. I've been trying to find a pdf that would explain all the symbols I see on a schematic but, unfortunately, I've found nothing. I'm hoping that somebody could reommend a site or a pdf or something for me that would include ALL the symbols I might come across. Thank you very much in advance!

Also, if anybody could explain to me what the circled symbols in the image attached mean, that would be really helpful as well. These were the symbols I originally started seaching for...


texts: How does input pin voltage protection with schottky work?

texts:
I'm trying to figure out how the schottky diode D1 is supposed to work in this schema.  Besides a lower forward voltage and faster switching time, the schottky diode works like a silicon diode.  So it blocks the current from the microcontroller TXD to the pin2 RXD of the bluetooth module (EGBT-45MS), which is confusing to me since now we don't get the signal to the bluetooth module.

So am I understanding this wrong or is the schema wrong?

The complete pdf can be downloaded here: http://www.martyncurrey.com/?wpdmdl=2436

I saw a another circuit diagram that used a 1N5817 schotty barrier rectifier and nothing else on the RXD pin.  There the direction of the diode was reversed.  But even then I'm not sure what that diode is protecting against.


texts: Will a soldering tip from a WEP-70 fit an old WECP-20?

texts:
I recently found my old soldering station from 20+ years ago - a WECP-20

But the soldering tip need replacing and one alternative, that looks the same, is the one fitting a WEP-70.

Will the WEP-70 tip fit the WECP-20 station?


texts:
I've been reading J.White's High Frequency Techniques, and in one passage is says:

  If the two port is a passive network, one might expect that the insertion loss
  could range from 0 dB (no loss) to some finite loss (a positive decibel value).
  But this is not necessarily so. For example, if the load is 25 Ohm and the generator
  impedance is 50 Ohm, installing a two port that is a low-loss transformer might
  increase the power delivered to the load, resulting in a negative decibel loss
  value, or power gain, and this would be obtained with a passive two-port
  network.

I do not quite understand how exactly can a transformer or other not externally powered element provide gain. Does it mean that the power is just transferred more efficiently? But then again, I'm not sure if this would be considered power gain.


texts: STM32 SPI not working as I expect it should based on online reading

texts:
I am using an STM32F103C8 to connect to a Hope RF95W transceiver IC for the purpose of learning.

I am only trying to read the chip version register, then write a config register that has a 0x00 reset value and then read it to make sure my write code works.

The RF95W datasheet says about SPI transfer:

  SINGLE access: an address byte followed by a data byte is sent for a
  write access whereas an address byte is sent and a read byte is
  received for the read access. The NSS pin goes low at the beginning of
  the frame and goes high after the data byte.

  MOSI is generated by the master on the falling edge of SCK and is
  sampled by the slave (i.e. this SPI interface) on the rising edge of
  SCK. MISO is generated by the slave on the falling edge of SCK.

  A transfer is always started by the NSS pin going low. MISO is high
  impedance when NSS is high. The first byte is the address byte. It is
  comprises:

  A wnr bit, which is 1 for write access and 0 for read
  access.
  Then 7 bits of address, MSB first.

To me this means that reading a register requires only one transfer.  Sending the address of the register, then waiting for the SPI_I2S_FLAG_RXNE flag, then the value of this register will be in the SPI data register.

However what's happening is I need two sequences of these write/flag/read operations to get the value:

uint8_t read_register(uint8_t address){

  uint8_t data;
  GPIO_ResetBits(GPIOA, GPIO_Pin_3); // slave select (low)
  delay_ms(100);

  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE));
  SPI_I2S_SendData(SPI1, address); // send

  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE));
  data = SPI_I2S_ReceiveData(SPI1); // read received

  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE));
  SPI_I2S_SendData(SPI1, address); // send

  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE));
  data = SPI_I2S_ReceiveData(SPI1); // read received

  GPIO_SetBits(GPIOA, GPIO_Pin_3); // slave deselect (high)
  return data;
}

Only by having these send/receive and then another send/receive can I get the expected value from the register. If don't make the second send, the receive returns a 0x00.

Writing is a little more straightforward, because it's a write of address, followed by a data write.

void write_register()
{
  uint8_t numRead1 = 0;

  GPIO_ResetBits(GPIOA, GPIO_Pin_3); // slave select (low)
  delay_ms(100);

  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE));
  SPI_I2S_SendData(SPI1, 0x40 | 0x80); // send
  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE));
  SPI_I2S_SendData(SPI1, 0x7E); // send
  while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE));
  numRead1 = SPI_I2S_ReceiveData(SPI1); // read received

  GPIO_SetBits(GPIOA, GPIO_Pin_3); // slave deselect (high)
}

In this case, I expect numRead1 to be 0x00 which is the default value of the register I am writing to.  A subsequent call to read_register with the same address returns the value I wrote to it.

But I am sure there's a fundamental mistake in what I am doing which if not corrected will lead to bigger problems down the road.

Any thoughts?


texts: How can over 24 GHz communication be possible?

texts:
I read the article Google wants the US' wireless spectrum for balloon-based Internet. It says to use over 24 GHz frequency spectrum for communication.

Is it ever possible to generate that high frequency by using piezoelectric crystals? Or are they using a PLL frequency multiplier?

Even if it is possible to generate that high-frequency signal, and if you want to send 1 bit on every period of signal, there must be a processor that is working much more faster than 24 GHz. How is that possible on a balloon?


texts: Problems initializing SD card with MSP430

texts:
I've been working on some code to talk to an SD card with the MSP430. I can't get the card to enter into idle mode, and I'm actually pretty stumped as to why. I've looked at the microcontroller output with a logic analyzer and everything looks as it should. I've tried a few different cards and SD card adapters with the same results so it seems like a code issue. I'm initializing the SD card with this code:

void MMC_initSPI(void){
//SOMI: 3.1
//SIMO: 3.0
//CLK: 3.2
//CS: 1.4
//chip select
SD_CSn_PxDIR|=SD_CSn_PIN;
SD_CSn_PxOUT|=SD_CSn_PIN;

UCB0CTL1 = UCSSEL_2 | UCSWRST;  // source USCI clock from SMCLK, put USCI in reset mode
UCB0CTL0 |= SPI_MODE_0;         // SPI MODE 0 - CPOL=0 CPHA=0
                                // note: UCCKPH is inverted from CPHA
//do I need to do this??
UCB0BR0 = LOBYTE(SPI_400kHz);   // set initial speed
UCB0BR1 = HIBYTE(SPI_400kHz);

P3SEL  |= BIT0 + BIT1 + BIT2;   // configure for USCI

UCB0CTL1 &= ~UCSWRST;           // release for operation
}

and then sending 0xFF within a for loop 11 times (well within the 71 clock pulses needed to awaken the card to new data) before using the mmc_GoIdle() function, which is as follows:

char mmc_GoIdle(){
char response=0x01;
CS_LOW();

//Send Command 0 to put MMC in SPI mode
mmcSendCmd(MMC_GO_IDLE_STATE, 0, 0x95);
//Now wait for READY RESPONSE
if(mmcGetResponse()!=0x01)
return MMC_INIT_ERROR;

while(response==0x01)
{
  CS_HIGH();
spiSendByte(0xff);
CS_LOW();
mmcSendCmd(MMC_SEND_OP_COND,0x00,0xff);
response=mmcGetResponse();
}
CS_HIGH();
spiSendByte(0xff);
return (MMC_SUCCESS);
}

but it always returns
MMC_INIT_ERROR. Can anyone spot anything obviously wrong? The logic analyzer tells me it's returning 0x00 and not 0x01 as it should. Any ideas?


texts:
I am trying to develop a GUI in MATLAB to allow the presentation of a tone.

One of the input parameters is the dB the user wants.

So the way I tried to do this is:

y = factor * sin (2*pi*500*t);

The "factor" parameter is: 10^(x/20).

I tried using the y values and do a mag2db conversion on matlab to see if I am getting the db back. And I do!

However, if I put in 0dB, I am still obtaining a tone.
I have to go down as low as -50dB to not get a tone.

So my question is : Is there some kind of a way to make it such that there is no tone at 0dB and below.

Thank you so much for your help.

Appreciate it!

Note: my PC speakers are at MAX level.


texts:
I need to measure solar Ultra Violet radiation index.

Is there any light sensor that would allow me to do this using an Arduino?


texts: for calculating the number of insulator disks needed for creepage is line to line voltage or phase voltage used?

texts: For example, I am calculating the number of disks required for a 330kV line. Assuming medium pollution (20mm/kV) and each disk having 405mm would my number of disks be 17 (based off line voltage) or 10 (based off phase voltage)


texts: Balun single-ended 50 Ohm to LVDS 100 ohm conversion

texts:
I have an LVDS differential 100OHM signal which I want to convert to a single-ended 50 OHM signal. I want to use a BALUN for this conversion.

What kind of BALUN should I use here?

Some BALUNs have 1:1 conversion ratio.
Some have 2:1 impedance conversion ratio.

Thanks


texts: Which precision rectifier should I use for a 60dB LM3915 Vu-meter?

texts: I want to make a 60dB Vu-meter with two LM3915 chips. In the datasheet is recommended to use an external precision rectifier and they give two type of rectifiers: half-wave and full-wave. My problem is that I don't know which should I use. I would prefer using half-wave rectifier because it's simpler, but this will produce results very different from full-wave ?


texts: Can I use a MOSFET driver to blink an LED

texts:
I was testing the MOSFET driver LTC7004 and tried to supply power to VCC and GND from an Arduino Mega with a PWM signal. The schematic resembles a Bootstrap circuit. I connected an LED between pins connected to Gate and Source but the LED doesn't blink.

Can I really drive an LED with a MOSFET driver?

  PS: We cannot :)


texts: Is it possible to charge 3 parallel batteries without sending charge to the UPS?

texts:
I have a UPS (uninterruptible power supply) with a 220VAC input designed to be used with 12V batteries. It has a rated capacity of 400 watts and I've placed three 12V car batteries in a parallel arrangement so it will last a long time.

The drawback is when used too long the UPS can't charge all three 12V batteries so I'm using a car charger to charge two batteries in parallel while one battery is still connected to the UPS. If possible I'd like to use a diode (or something else) to switch so that I can charge all three of them without sending the charge voltage back up to the UPS.


texts: IGBT destroyed. Help me identify any potential problems

texts:
I am trying to build an inductive oven control (for temperatures up to 1500 C), that controls the temperature by turning on the the inductive oven on and off like a commercial inductive hotplate.

The problem I am facing is, that the IGBTs (K75EEH5 rated for 75Amps and 650V) I am using for switching got killed twice with my schematic. The collector and emitter is permanently shorted, even after shorting gate and emitter.

Here is a short clip that I filmed for myself as proof that it is working with a 24V light bulb (not an inductive load!); sorry that its in german but it should give you a rough idea how it looks
The IGBT is isolated from the cooling body.

The first time It didn't work at all (no flyback-diode at the load). The second time it worked when running a test with 24V power (this time with flyback diode) but after shutting down and then starting with 36V it shorted like it did the first time.

My Arduino microcontroller controls the signal by applying 5V to the D0 pin when turning on and 0V when turning off.

Not shown in the schematic is, that the Arduino is connected to a computer which sends commands, that the microcontroller executes.

It says in the datasheet, that the driver module (1EDI60I12AF) and the voltage converter SIM-0512D is galvanically isolated.

What I will change next time is:

Swap places of load and IGBT (shouldn't matter though)
Add a 1k to 10k Ohm resistor between gate and emitter to slowly discharge when not in operation. (doesn't matter either)
Measure voltage across collector to emitter and gate to emitter to identify spikes. (Gate emitter voltage musn't be more than +-20V)

What I need now is some external input on what might be causing the death of my IGBTs. I will provide you with any further information that I can give you.


texts: Crystal Oscillator design with no data sheet

texts:
I am a newbie to circuit design and I need a 50MHz clock. I went to a local electronics store and got a 2-pin radial Quartz crystal. I do not have a data sheet for this. The only markings for the part are on top that says "FS50.00" [the double quotes are mine]. The packaging seems to be referred to as metal can (long rectangle with round sides).

Does anyone have any ideas which part this might be and how to make this thing oscillate ? I have tried some circuits with a resistor at 3.3v but it does not look like I am getting anywhere.


texts: Alternate ways of measuring distance (lateral)?

texts:
I'm working on a micromouse, a small autonomous robot that traverses a maze.
I need an efficient way to measure lateral distance to walls and I'm looking at the
Sharp GP2D120
but looking at the datasheet, it has long typical response time of 39ms, is quite bulky, and has a minimum distance of 4cm.
Can you recommend a better sensor (that possibly has a lower minimum distance)?

I was wondering what are some alternate ways of measuring distance? I have seen other micromice use IR LEDs and it was interesting but I'm not sure how it works.

Any input is appreciated. Thanks!


texts: Earbuds with only 1 speaker working: will it draw less power from iPod battery?

texts: I want to test battery life (music play time) for my iPod nano 6, but my earbuds has only one speaker working (other has a broken wiring). Will my test be accurate, i.e. will my earbuds draw the same amount of power from the battery as if both speakers were working? And if not, how could I mitigate/compensate this using my current earbuds, to make test resuls more accurate?


texts:
What a near-perfect-accuracy yet dirt-cheap way for a drone or other miniature embedded computer to sense whether it's indoors vs outdoors? Some ideas:

Geo position sensor if small, low power, and cheap enough
Light sensor to detect the 60 Hz flicker of electric lights
Antenna and analog filter to detect EMI typical of occupied buildings
Echo generator & microphone
broad-spectrum UV-visible-IR photosensors to discriminate natural vs solar light
Thermometer, barometer, or other air sensors


texts: Effect of Gate-Drain Capacitance on Input Impedance of CS Amplifier

texts:
I am studying MOSFET amplifiers and came along the following interesting statement:

The gate-drain capacitance of the MOSFET in a CS amplifier decreases the input impedance of the amplifier.

I spent quite a lot of time to verify this which was unsuccessful until now.
Can someone please give me some insight?


texts: Ideas to smooth variable AC voltages/spikes reported to ADC circuit

texts:
I’m trying to integrate a 40+ year old ac motor and remote controller with a device using modern ADC controllers to remotely manage the motor turning process.

The legacy gear is an old CDE Ham-M amateur radio antenna rotator which converts maximum voltage (26 VAC) to a compass heading.  The tower mounted rotor includes a 500ohm resistor (wound on a 360 degree platter on the motor axis) which reports the voltage to a meter converted  to a compass direction.

The issue at hand is some of the windings on the 500 ohm pot in the remote motor aren’t in perfect condition.  When the rotor is turned with the legacy controller, the meter spikes in voltage around some compass headings, which gives the ADC circuit fits.  Apparently, the device with the ADC samples so frequently, that when the legacy devices reports momentary voltage spikes (1-2VAC), the ADC device gets so many different values so quickly, that it sends many different relay commands to stop, reverse or advance the motor.  The relays in the digital device chatter rapidly, sending  commands to turn CW, then CCW and then brake, that finally high current in the motor exceeds the fuse rating.  When this occurs, the motor is stalled/paralyzed, often resulting in a blown fuse.

The motor xformer is rated at 26VAC protected by a 3A 3AG (fast blow) fuse.

I’d like to implement a circuit change that will smooth these spikes/variations and reduce the ADC measurements that cause the relays to send CW, CCW and brake commands in rapid succession.

I’m wondering if a decoupling cap across the circuit reporting voltage would smooth the voltage reported to the ADC?  If so, what would be a likely uF  value?  This variability in voltage is for no more than 2-2.5 seconds and less than than 3VAC, until the swiper on the 500 ohm pot reports steady voltages and the ADC is “happy”.

Or do you recommend a different solution to smooth the voltage?


texts: I have a small project that I'm trying to figure the cheapest and most reliable method for. I. Wanting to measure various points along an outboard motor propeller to gauge the exact pitch to be able to make modifications. I need the difference between the leading edge and trailing edge measurements of each blade to gauge the amount of displacement, and then also measure the degree of rotation for these points so I can then measure pitch. I've looked at laser measurement but these are very expensive. And I've been having a look at LVDT but there are s many types and I'm unsure how I then get the information out of them. I wouldn't mind being able to read a display or have direct input to PC via USB. Any assistance is greatly appreciated.


texts: Will the following ATSAMD21 series code properly configure SysTick interrupt?

texts:
I haven't seen any examples of registering ISRs in Atmel Studio 7, but I've given the following code a go in my IDE.

/*
 * mainCode.cpp
 *
 * Created: 1/29/2020 11:30:58 AM
 * Author : tuskiomi
 */

#include "sam.h"
#define CPU_CLK 48000000 //CPU Clock Speed in Hz
#define SYSTICK_INTERVAL_MS 10 //System should always run at 100 Hz
#define SYSTICK_INTERVAL_CYCLES (CPU_CLK/1000*SYSTICK_INTERVAL_MS)-1
#define SYSTICK_CALIBRATION_VALUE (CPU_CLK/100)-1

void handleSysTick(){

}

int main(void)
{
    /* Initialize the SAM system */
    SystemInit();

        SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
        uint32_t CPU = SCB->CPUID;
        uint32_t CPU_MINOR_REV = CPU&0x000F;
        uint32_t CPU_PART_NO = (CPU>>4)&0x0FFF;
        uint32_t CPU_MAJOR_REV = (CPU>>20)&0x00F;
        uint32_t CPU_IMPLEMENTOR = (CPU>>24)&0x00FF;
        //uint32_t SCB->
        SysTick->CTRL = 0x05;
        SysTick->LOAD = SYSTICK_INTERVAL_CYCLES;

        __NVIC_SetVector(SysTick_IRQn, ((uint32_t) *handleSysTick));

    /* Replace with your application code */
    while (1)
    {
    }
}

My main concern is with the line:

__NVIC_SetVector(SysTick_IRQn, ((uint32_t) *handleSysTick));

My c++ is very rusty, and what the expression ((uint32_t) *handleSysTick) is supposed to be is a uint32_t representation of the address that the function "handleSysTick" starts from. If this is indeed the case, then it is safe to say that the interrupt is properly configured.


texts: Tips on ESD protection for hobbyist designs

texts: I'm finally getting into simple PCB design for my personal projects, and I'm concerned about ESD protection on exposed parts of my board like USB ports. I know how wrist straps work and I understand things like clamp diodes on modern CMOS IC inputs (and a lot of articles I've found basically only discuss those things), but I'm more curious about discrete ESD protection devices. How should I choose them and use them? Any general tutorials that discuss the spectrum of devices and how to apply them? I have found some pretty good articles discussing how, for example, TVSes work, but in what situations are they an appropriate solution, why would I choose them over other devices, etc.


texts:
Is there any issues with using low impedance mode on a multimeter for day to day testing on mains voltage 240Vac or if this mode should only be used when testing for phantom voltage?
Is there any risk of damaging a meter this way?

The meter manual describes the LoZ mode as,

And it's function is,


texts: IR emmiter and reciever layouts for custom sensor

texts:
I'm having a hard time designing a PCB for a sensor array that need to detect if there is a small reflective object (3-20 mm section) in the way. That object can slowly rotate around a shaft.

I have tested several sensors,sharp GP2Y0A21YK0F, EE-SY410, HSDL-9100-021... and all have some zones where my uC is unable to detect if there is an object or not because most of the light is reflected. I still have to test opb9000 (not done yet because of the communication protocol) and vl530x (TOF sensor), but I expect to get similar results.

With the custom PCB i have used discreet emitter/receivers.
The emitter is optoisolated with a small barrier. There is some crosstalk but I can detect in most of the cases if there is a key with a decent threshold.
I'm able to do analog measurements and filter it on software, buy I prefer to make my life easier and pulse the IR emitter at 10 kHz, make an analog narrow bandpass filter and recover the signal without the DC component, induced noise and amplified to the full range of my ADC.

Now the questions:
Someone can recommend me a cost/effective layout to detect the object without adding sensors in a different plane?
I know that there is some math and optics involved to get it exactly right but some layout ideas might help.
I can pulse up to four IR emitters independently.

Shall I try a different sensing method? I think that the bandpass is quite nice method to improve noise immunity at low cost.

Image to help to understand the question. When the small side of the object is in the red area the sensor fails to determine if the object is in there. (The measurement is too close or the same that the one without the object)


texts: Can commercial 9v batteries deliver 2 amps?

texts:
Are these commonly used, cheapish batteries able to deliver 2 Amps of current continiously and safely?

I know that assuming 200mAh capacity the battery will be dead in 6 minutes or so.

Example batteries:

https://www.hepsiburada.com/varta-power-accu-ready-2-use-9v-pil-e-200mah-56722101401-p-OFISVAR56722101401?magaza=infstore&wt_gl=cpc.6803.shop.nelk.ofis-ofis-teknolojileri&gclid=Cj0KCQjwuZDtBRDvARIsAPXFx3B_oZsxHNskuf7E82mbtejUbONWIwsSxC2bBX2XlHX82fS7oRs51XwaArz8EALw_wcB#reviews

https://www.hepsiburada.com/varta-2022-superlife-9v-pil-shrink-p-HBV000002B6KL?magaza=pilstore&wt_gl=cpc.6803.shop.nelk.ofis-ofis-teknolojileri&gclid=Cj0KCQjwuZDtBRDvARIsAPXFx3BOo0VFOX4w69U08zstTlcjGltLX2qWlco37IklfYpOs4wDDT8L-QcaArdfEALw_wcB


texts: 3 Loop Circuit-Kirchhoff's Voltage Law(KVL)

texts:
I am struggling to solve the circuit given in the attachment. I have found the current values in the circuit and I am not sure about it(I do not have the answer sheet). I would like to ask whether it is true or wrong. If wrong, where have I done wrong?

---Edit---:

\$9V-90\Omega I_{1}+90\Omega I_{2}=0\$

\$12V-210\Omega I_{1}-90\Omega I_{3}=0\$

\$9V+120\Omega I_{1}-30\Omega I_{2}=0\$

I tried to convert these equation to matrix as follows:

\$A=\$\begin{bmatrix}90 & -90 & 0\\210 & 0 & 90\\ -120 & 30& 0\end{bmatrix}

\$b=\$\begin{bmatrix}90\\12\\9\end{bmatrix}

And solved the equation in MATLAB by the command x=A\b an got the results:

\$I_{1}=-0,1333\$

\$I_{2}=-0,2333\$

\$I_{3}=0,4444\$

I do not get 0 when I put the values back to the equation nor when I run A*x-b on MATLAB.
I am still struggling on where I do wrong. Is the problem on the assignments of the currents or the equation or some numerical errors while solving?

I know that my handwriting is not really clear but I have added my paper which I solved on just in case as attachment with the name "Attachment 2".


texts: Marvell Ethernet PHY unstable link status

texts:
We are currently testing the copper link from Processor RGMII interface through Marvell 88E1510 Ethernet PHY. The PHY registers shows Cu link as unstable with the link going up and down randomly. Here are the tests already done:

The power supplies to the PHY are correct.
The clock supply is a crystal that is supplying the appropriate clock.

The same PCB routing and schematic has already been tested in previous prototype.
Any help regarding the above is appreciated. Thank You.


texts:
I designed and simulated a tone generator of some sort using multism. I got some parts of the circuit online. When I tested it on a breadboard, the speaker didn't make any sounds. ere is the circuit:

Here is the resulting wave across the 8 ohm resistor(speaker):

Here is the simulation results:


texts: VHF: power resistor to replace dummy load

texts:
I need to check a VHF radio installation @ 155 MHz. For these purposes there exist fairly expensive dummy loads. Can I just use an ordinary power resistor soldered with short wires (3cm) to an appropriate connector instead?

What are the possible problems?

inductance of the resistor?
standing waves due to impedance mismatch caused by the wires between the resistor and the connector?


texts: Atmel ARM, USB, and an SD Card as a MSD?

texts:
I'm currently trying to run the SAM L21 as both a CDC and an MSD over USB. Thankfully there is example code here to get me started. I can move files into the on-board ram just like any other storage device. I can also send and receive data from a PC through a virtual COM Port created by the CDC code.

However, this is not the full implementation I have planned. I need to use a fat32 formatted SD card to save collected data. Usually one would connect an SD card to an MCU via SPI. However, I'm not sure that will work with my setup.

Can my MCU be made to write data over SPI into a fat formatted SD card? If this is possible, will the computer still recognize the SD card as formatted and usable?

If this is not possible with SPI, does anyone have experience integrating full SDC compatibility into an MCU? Links to documents or example code would be fantastic!

The end result will be a single usb connection that can sends and receive communication/data, as well as allow a user access to a formatted SD card for direct access to all data collected.


texts: How to protect equipment from voltage anomalies

texts:
My refrigerator makes some short anomalies in electric network in my apartment whenever it starts/stops its compressor. I'm not sure if it's a brief frequency change or voltage drop. I can notice this by hearing loud bang in my guitar amp (when it's turned on). Also I can hear it in my headphones when they're connected to my PC - both desktop and laptop when it's plugged in.

How can I protect my equipment from that?
I have tried line-interactive UPS with AVR (APC BX950U-GR), but situation stayed the same.
I cannot afford an online UPS.

What kind of equipment can solve my problem?
If that's an AVR, what specification it should have?


texts: How close can BGA packages be placed to each other?

texts:
I'm wondering if there is some rule of thumb about how close different BGA packages can be placed to each other.  What limits that besides pick and place accuracy?

I'll ask a few board assembly places for their recommendation but I was wondering what the lowest common denominator recommendation is (similar to how 6 mil trace and space is a pretty standard thing most pcb manufacturers can do without adding extra cost).

Are there any similar rules of thumb about passives near a BGA? and anything on the opposite side of the board under a BGA?


texts: I found this schematic online for an audio amplifier and I noticed the 100k was some sort of feedback system between the base of the first stage and the emitter of the next. How would you describe this feedback mechanism? What is its effect on the gain and bandwidth of the system?


texts: Closing a circuit a predefined number of times

texts:
I have a bunch of cheap rope lights with a built-in controller with a single button to change the light effect. When the rope lights are plugged in, they turn on and start cycling through the default effect. When the button is pressed, they switch to the next effect, and so on.

The problem is that the lights have no memory. When the power goes off, they default back to their original effect. I'd like to try and construct a circuit to interface with the lights, so that when the power is turned on, the circuit simulates the number of button presses to reach the predefined light effect.

Since the button on the controller just closes some circuit, I assume that all I need to do is find and build a schematic that is able to close the circuit a set number of times. I could probably do this with an Arduino, but I would like something a bit more bare-metal, since I want to replicate this for 5-6 different rope lights, which would be a bit pricey with an Arduino.

Suggestions?


texts: Are Inclinometers/Angle Gauge's independent of gravity

texts:
To give a bit of background, I am working on a DIY wheel alignment just to save some money and possibly learn a thing or two. The camber/caster involves measuring an angle that is parallel to the force of gravity (pitch or roll or X or Y axis). The toe involves measuring an angle that is orthogonal to the force of gravity (yaw or Z axis).

I have a dual-axis inclinometer (this one) that measures pitch and roll. I was able to get very accurate readings for the camber. However, my thought was that rotating the inclinometer 90 degrees would allow the X/Y axes to become a Z axes. However, when I rotate it the screen itself changes to only provide measurements in the pitch/roll axes. After much more thought and looking around, I am starting to think that this inclinometer is not capable of measuring yaw because it depends on gravity to measure tilt.

How do these inclinometers typically work?
Are they independent of the force of gravity?
Are there particular models or methods that can be independent of gravity?


texts:
I built an SMPS (see here for details), and so far it's been working good. But I noticed a strange oscillation (or ringing?) at the output.

Here's what it looks like, with a 4 amps load:

Now, you'll see a HF oscillation when the switch turns on (right at the center of the image, for example). I measured this at 15MHz and figured the MOSFET needed a snubber. I added one (10nF + 10R in series, across D and S), and the 15MHz ringing went away completely.

But I still have that "larger" ringing that can be seen in the picture, around 3.5-4MHz.

What is this ringing?

Is it harmful?

If it is: How can I fix it?

EDIT:
Here are some measurements (transient response, voltage across MOSFET and diode, etc). http://imgur.com/a/Qs351


texts: Pulling down positive voltage to limit negative voltage current

texts:
Below circuit is the negative rail of a dual tracking power supply.
How do I detect voltage drop on Node1 and pull down Node2 to limit the current without using an op-amp?
Edit: I just want to define a limit that U1 couldn't output more than 200 mA for example, when shorted to ground.

simulate this circuit – Schematic created using CircuitLab


texts:
simulate this circuit – Schematic created using CircuitLab
I am making a fan that shuts off after a minute or two, but is this circuit safe for the fan? It runs at full power at first, but as the caps discharge, the fan should slow down and eventually stop when the caps are fully discharged. The button resets the circuit.


texts: PIR Op amp circuit voltage gain question

texts: I have come across this circuit on a mock paper, which is asking me to find the overall voltage gain of the circuit, it is a bit of a scary looking circuit and i'm not quite sure where to start, any help would be massively appreciated!


texts: How to count bike wheel Revolution by 3-axis acceleration

texts:
I want to use MCU and BMA250E 3-Axis Acceleration for count bike wheel revolution.
and I can read the x-axis datas without vibrate.

and I want to ask how to analysis sine wave datas


texts: How do you find accurate slope for these two hall effect sensors?

texts:
I'm looking at two current sensors.

ACS712 and L18P005D15

At this stage, I'm just trying to understand how the Vout is related to Iin.

Looking at the ACS712 sensor, I see the following

Does this mean that for each 1A, my output will increase/decrease by 185mV ? So for each 1mA change, my output changes by 185uV ? Is that how I can understand this particular sensor ?

The second sensor, I don't understand at all. The datasheet doesn't explicitly say how to accurately relate Iin and Vout together (or maybe I'm just not realizing it). The following two images are really all thats on the datasheet for this sensor.

So the main question is, how can I determine an accurate relationship between Iin and Vout for these two sensors ?


texts:
Assume I have 2 flipflops FF1 and FF2 which are driven using multiple clocks. What might be the possible violations that we would come across? I was asked this in an interview for which I answered telling the difference in skew or the clocks would cause timing violations and metastability and further explained how to solve setup/holdtime violations . But in the end interviewer said these issues come into picture only when we use a single clock with skew/delay between the clock inputs of the 2 flipflops. So I was wondering if anyone can tell me what happens when I use multiple clocks

simulate this circuit – Schematic created using CircuitLab


texts: Creating SRAM array digitally using Verilog

texts: As a part of my Cadence based project, I chose the topic 'Optimising power, area and timing for a 32x8 SRAM unit'. Though this is possible using NC-Verilog or by manually constructing the schematic and simulating, we have been instructed to use the Encounter Tool alone. Is it possible to create the SRAM array digitally using Verilog? Is it possible to specify for analogue parts such as transistors their widths etc. by writing a Verilog code?


texts: What to do with an interesting idea about sensor design?

texts:
I think I've had a cool idea to replace the Bayer pattern in sensors with something better, but I'm not even sure if it's definitively an improvement.

It's not something too complicated, just a different arrangement of the photo diodes with an array not made of equal squares (I drew inspiration from Fuji's Super CCD and X-Trans sensors, plus sensors with panchromatic diodes); so it might have already occurred to somebody else and was discarded because it was technically unfeasible or impractical.

So my possible options would be:

Give up and forget about it (I'm not that smart after all).
Go for it:

Research more the state of the art, read patents, etc. to see if it has been tried already.
Make simple computer model and simulate to see if there are any improvements, at least under optimal conditions.
Fill a patent and try to sell it.

Give it away for free: I think It's better that somebody else makes profit of a good idea than letting it go to waste. Maybe send an e-mail to the R&D department of a camera manufacturer telling them the idea and asking them if it was worth at least to consider.

Any other ideas?


texts: determining the start and run capacitors for single phase motor

texts: I have a 5 hp Ajax single phase AC motor. When i got it the start and run caps were missing. Is there anyway to determine the proper start and run cap values based on the info on the nameplate? Thank You.


texts: Serial LED driver with individual PWM, compatible with common cathode bargraphs?

texts:
I bought one of these circular bargraphs from Sparkfun. A 16 LED bargraph with two common cathodes.

I'd like to drive it from a single chip to free up I/O on my micro, and not take a bunch of cycles running soft PWM. There are many chips, like the TLC5940 that can do this, but they can only sink current, not source it. A 74HC595 solves the first, but not the second, and is limited to 70mA total.

I've tried every combination of search term I can think of and have only come up with 7 segment drivers, which are overkill and never have individual dimming. So does anyone know of a chip I'm looking for? Or am I better off tossing this and making my own out of individual LEDs?

Thanks.


texts:
Hello this is my first post.
I have a question regarding the circuit diagram of the Roland 606.
I'm currently redrawing the hihat circuit with noise unit.

The symbol behind R6, and elsewhere in the schematic this bulky explanation.
Can someone tell me what that means?
Thanks,

Petunia


texts:
So I bought a SEGA CD off ebay and everything was fine until I decided that the duct tape that was holding the battery is was a poor substitute for a battery holder.
So I took my Model 1 apart begun to unsolder the joints that held the battery down. However, one of the parts snapped off and my attempts to empty the hole and remove the remains may have damaged it in the process. Below pictures of the hole that may be damaged.

I've tried applying more solder and removing, solder wick, solder sucker, nothing. I will admit I put my iron directly on top of it hoping it would melt the solder inside causing the pin to drop out but that didn't work.
At this point, I'm considering using a small drill or a jewelers filer to clean out the hole however I'm only considering this last option which I will probably put off for a while due to how uncomfortable I am of using them on a PCB.
So basically,  what are my options? What can I do to save the PCB? Can I simply drill or clear out that hole with a drill/filer and fill it with solder to fix it?
Edit:I'm using a 25W Soldering Iron. Picture was linked in comments.


texts: Water heater power cable has changed color

texts:
Couple of years ago I've installed an electric water heater in my toilet room (a model similar to this one). It's a kind of water heater that has a big tank of water with heating elements inside.
Recently I've noticed that the power cable which once was pure white is now having these regions of brownish rusty-looking color:

It's definitely not dust or grime as it can't be wiped off / removed, looks like the insulation material has changed color.
What can be the reason for this? Is it dangerous, can it affect insulation properties? It's quite possible to touch the cable when using the toilet.
Thank you in advance for your answers.


texts: LM13700 control current appearing as voltage at output?

texts: I've got an LM13700 in this VCA configuration, and for whatever reason the gain control input (I'm applying a triangle LFO, ranging from 2-7v) is appearing as a voltage at the output. Does anybody know why this could be happening? :


texts: Ethernet 25 MHz and 50 MHz harmonics cuases radiation emission during the EMC lab test

texts:
My PCB has been suffering with 25 MHz and 50 MHz harmonics radiation emission.

I am using STM32F207 microcontroller operating with 8 MHz crystal.

I am interfacing MAC in microcontroller to PHY (LAN8720A) through RMII.

LAN8720A PHY operating with 25 MHz crystal. It generates 50 MHz reference clock to microcontroller.

Even though CAT5 cables were not connected to RJ45 connector, PCB is generating the radiation emission.

How can I arrest this radiation?

We followed LAN8720 layout guidelines, but we faced radiation emission. Even though LAN8720A development board also generated radiation emission.

Please suggest how to route 50 MHz reference clock from PHY to microcontroller.

How do I arrest the radiation emission? My PCB is exactly the same as the LAN8720 development board.

You can see in the below link:

http://www.microchip.com/DevelopmentTools/ProductDetails.aspx?PartNO=evb8720

Observed points: When 25 MHz crystal pins are shorted with wire, there is no radiation.


texts: Can the voltage drop of an LED driven at a constant current be higher than the supply voltage?

texts:
So I've been working on a constant current LED driver project, and I've run into a weird situation. I'm driving 3 parallel rows of 8 LEDs in series (Luxeon 2835 color, green) using a Sparkfun picobuck with an AL8805 in it, configured to supply 330mA. The input voltage is a 24V power supply. According to the datasheet for the LEDs I'm using, at 110mA, the voltage drop across a single LED should be ~3.1V. Since I am driving 3 parallel rows of 8 in series at 330mA, the combined voltage drop of the series LEDs should be 3.1 x 8 = 24.8V, which is higher than the input voltage. However, if I measure the drop across the LEDs with my multimeter, I get 24V, and if I measure the current, I get 330mA. The LEDs appear to light up fine.

Can someone explain what's going on here? How can the LEDs draw more current than the voltage drop across them in series should allow?


texts:
I’m working on a motorcycle here. I have a 12v battery to work with and a stator that produces (limited) power. I have a throttle position sensor that I believe needs 5v input and outputs up to 5v.

The question is: how do I convert ~12v to 5v? The 12v may not be exactly 12v and if my understanding of motorcycles is accurate it may fluctuate as I ride. Is there something that can take let’s say 11-13v and always output almost exactly 5v? Minor fluctuation is fine but any fluctuation would be seen as a changing throttle position. 10% is a huge error. More like 2-3% error would be nice.

Whatever device it is, if it doesn’t use up too many amps that’d be nice as my stator can only handle so many amps drawn.

Thanks!!


texts:
I faced some errors while trying to simulate a circuit. I tried to simplify it, but errors still stayed in place :|

The following error message is what I get:

                    *************** PROCESS COMMAND ***************

/usr/bin/ngspice -n -b /home/rasakereh/Desktop/sharif/9602/EEC/test/test.ckt

                *************** PROCESS RESPONSE **************

Warning: singular matrix:  check nodes v3#branch and v3#branch

Warning: singular matrix:  check nodes v3#branch and v3#branch

Note: Starting dynamic gmin stepping
Trying gmin =   1.0000E-03 Warning: singular matrix:  check nodes v3#branch and v3#branch

Warning: Further gmin increment
Trying gmin =   5.6234E-03 Warning: singular matrix:  check nodes v3#branch and v3#branch

Warning: Further gmin increment
Trying gmin =   8.6596E-03 Warning: singular matrix:  check nodes v3#branch and v3#branch

...

Warning: gmin step failed
Warning: source stepping failed
doAnalyses: iteration limit reached

run simulation(s) aborted
Error: no such vector v(4)

Circuit: ********************************************************************************

Doing analysis at TEMP = 27.000000 and TNOM = 27.000000

CPU time since last call: 0.009 seconds.

Total CPU time: 0.010 seconds.

Total DRAM available = 7880.691406 MB.
DRAM currently available = 4678.652344 MB.
Total ngspice program size = 14.774414 MB.
Resident set size = 1.865234 MB.
Shared ngspice pages = 1.638672 MB.
Text (code) pages = 1.333008 MB.
Stack = 0 bytes.
Library pages = 404.000 kB.

I  am using gEDA gscheme to generate the schematic, netlisting it using gnetlist and spice-sdb backend, trying to simulate it in gSpiceUi.

Thanks


texts: Calculating voltage on inverting and non inverting pins for an op amp

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How does he calculate Va and Vb here:

I understand the rest of the stuff after he figures out what Va and Vb are. But how do I figure out Va and Vb when not given the values ->


texts: Matching Audio Amplifier with Speaker (Watts Rating/Output)

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Background

When selecting an amplifier and speaker, you are usually provided ratings or output in watts. For a speaker you get maximum and nominal watts rating, while for an amplifier you get output in watts.

I am confused, because I have read that you want your amplifier to have a higher output in watts than you speakers watts rating, as this means it does not need to work so hard to power the speaker, so will avoid clipping.

I have also read, that you only want to supply the speaker on average its nominal rating, while only supplying its maximum rating in bursts. If you exceed these numbers you will damage the speaker.

Question

So, which is it? Should my amplifier have a higher output in watts than my speakers maximum or nominal power rating? Or should my speakers have a high maximum or nominal rating...and if so, which one, nominal or maximum?

Which of these configurations is recommended?

1. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (3W Output)
2. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (2W Output)
3. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (1.5W Output)
4. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (1W Output)
5. Speaker (Max Rating 2W, Nominal Rating 1W) and Amplifier (0.5W Output)

Context

To provide some context, I am designing a solution for a low cost consumer product that does not require high fidelity audio or high volumes. The amplifier will need to run off 3.3v or 5v, which will be provided by an adapter connected to mains power. Audio will be provided by a line-level input, most likely the audio device will be a phone, mp3 player or computer.

I am currently looking at these ICs, as I just need a low cost mono amplifier (class AB) to drive a small speaker (most likely 8 Ohms, unless I can be convinced otherwise) - http://www.ti.com/product/tpa6211a1#parametric


texts: Capacitor behavior in oscillating circuit

texts:
I've been making my way through "MAKE: Electronics: Learning Through Discovery", but have gotten stuck on Experiment 11, where I am making an oscillating circuit.

The book calls for a 2.2uF capacitor, but I only have a 1000uF capacitor. I decided it would be fun to try to create a circuit that functions similarly with the parts I have (or at least to understand why doing so would be impossible)

The circuit specified by the book is this:

R1: 470K Resistor, R2: 15K Resistor, R3: 27K Resistor, C1: 2.2uF electrolytic capacitor, D1: LED, Q1: 2N6027 PUT

The first thing I did was replace R1 with a 6.7K resistor so it wouldn't take so damn long to charge the capacitor. Next I replaced R2 with a 26K resistor and R3 with a 96K resistor so that the PUT would only let charge through when the capacitor was near the peak of its voltage.

I was expecting the LED to turn on once the capacitor charged to ~5v, and turn off once the capacitor discharged to less than ~5v. Instead, the capacitor charges for a few seconds, and the LED remains dimly lit while the capacitor's voltage remains steady at ~2.7v.

With my very limited knowledge of electronics, I am stumped by this behavior. Am I misunderstanding how a capacitor works? Thanks in advance for your expertise!

UPDATE: I still don't exactly understand the relationship between the resistor values and the LED/capacitor getting "stuck" (where getting stuck means the LED will stay lit and the capacitor voltage will stay constant around 2.5v). After some more testing it appears that:

The larger R2 and R3 are (keeping the R2:R3 ratio approximately constant), the more likely it is the LED/cap will get stuck
The smaller R1 is the more likely the LED cap will get stuck.

For example, with R2 at 15K, R3 at 21K, and R1 at 66K, the LED/cap will oscillate properly (although slowly). If I change R1 to 46K the LED/cap gets "stuck"

Does anyone know of an explanation for this behavior?

I believe Mark has the right answer (based on some testing) so I've accepted it. If R1 has much less resistance than R2 and R3, the cap charges much faster than it discharges so that it oscillates quickly while it appears to the multimeter that it is "stuck" at one voltage.

However, I would appreciate if Mark (or anyone else) can explain how to come up with that insight about Rg from the datasheet