texts:
I'm designing a circuit that steps down 230v AC to 12v DC and then uses an MCP73213 IC to charge a 7.4v li-po battery. There is also functionality to switch over to the battery supply if there is no 12v input detected (via Q1, D1, D2). The circuit is to output either 12v or the batteries 7.4v to some buck converters on a separate board.

I'd now like to begin making the single sided PCB layout. I'd like to get advice on how I should approach the layout of this board especially with respect to thermal considerations. I have placed the components on the board as below. The buck converter circuits (which will connect to the screw terminal on the right side of the board) can draw up to 2.5A so I was thinking I will need to make all tracks which carry this main current, that is the path through the diodes, the MOSFET, the full bridge, the transformer at least 75mil wide and to solder thick copper wire onto the tracks afterwards to make sure to meet the power requirements of that kind of draw. The charging IC tracks I was thinking of making 10mil wide. What sort of solid planes copper/fill if any would be recommended for this circuit? Are there better ways to arrange the components?


texts: Determination of System poles through open/short circuit time constant technique

texts:
I was reading about the open and short circuit time constant technique for estimating the dominant and non-dominant poles of the system respectively. For the dominant pole (open circuit time constant) we short all the independent voltage sources and replace all but one of the capacitors with open circuit. We then calculate the time constant of the resultant circuit and add the time constants for all the capacitors and the dominant pole frequency is given by:
$$p_{\text{dom}} = 1/\Sigma_i(\tau_i)$$ where \$\tau_i\$ is the is one of the time constants of the circuit.

Similarly for the short circuit time constant technique to estimate the non-dominant pole we replace each capacitor by a short circuit and the pole is given by:

$$p_{\text{non_dom}} = \Sigma_i(1/\tau_i) $$
(For details: http://paginas.fe.up.pt/~fff/eBook/MDA/Met_con_tem.html)

Consider the following circuit:

For this circuit the non dominant poles are calculated in Gray Meyer using the above procedure:

\$\tau_1 = C_fR_L\$ and \$\tau_2 = C_{gs}[R_S||1/g_m||R_L]\$ and \$p_{\text{non_dom}} = 1/\tau_1 +1/\tau_2\$
But suppose I add a load capacitor to the output as shown:

Now when I try to calculate the non-dominant pole from the above method, every other capacitor seems to be shorted making the time delay for each capacitor to be zero.
How should we calculate the non-dominant pole of this new circuit?


texts: How to characterize a lower node transistor?

texts: I am a fresh college graduate and have recently started working as analog design engineer. I am working on 22nm FDSOI technology, And characterizing this device has been trouble for me. The device is way too sensitive for every parameter. I have done this before with 180nm technologies and there, hand calculations and simulator results used to be pretty close. Please suggest how should I characterize the device and what current equation should I use as the regular one isn't helping.


texts: Simple and easy-to-charge battery for a DIY power generation project with varying voltages and currents?

texts: I'm converting a decorative windmill to a power generation device. I'm looking for a battery that can charge with wildly different voltages and currents and be simple and easy to charge. It doesn't have to be "plop-right-in" simple, I'm perfectly willing to do some work to get it to work.


texts: Audio feedback killer/audio delay circuit/bucket brigade circuit

texts:
Total noob here, please be gentle.

Back in 2010, this thread was started regarding audio delay curcuits: Audio delay using discrete components

After six years or so, I am wondering (hoping?) whether technology has caught up with this question, and that some expert in here (endolith?) can provide a simple and easy solution for building a delay circuit that fits my needs/fits the bill.  After some research online, it seems that the minimum standards for this type of circuit, is a delay of approximately .015-.02ms.  This is enough of a interruption in the microphone-speaker-loop, to eliminate most feedback issues, while still maintaining continuity between the speaker's mouth and the sound leaving the speakers.

Any takers?  Thanks in advance for any help and advice!


texts: Problems writing with I2C to registers in Allegro ACS71020

texts:
I am wanting to change some of the configuration parameters contained in registers in the Allegro Microsystems ACS71020. I am using an I2C version of the IC. Here is the datasheet: https://www.allegromicro.com/-/media/Files/Datasheets/ACS71020-Datasheet.ashx .  In particular, I would like to set a specific I2C address for the chip and disable the default analog voltage input selection approach to choosing the I2C address so I can use those pins for other purposes.  The datasheet suggests that I should be able to permanently make such a change by updating register 0x0F/0x1F.

I am able to read data from registers but I have been unable to write to any register including register 0x0F.  The wire.endTransmission() call terminates successfully but on reading back the register, nothing has changed.  I am clearly missing something. There are ECC codes for these registers.  Is that something I have to set?

I can post a sample program if someone has the patience to look at it.

Update: Problem solved.  See comments to Umar's answer below.

Thanks for the help.


texts: How impedance levels affect a non-inverting amplifier?

texts:
I need help understanding what the highlighted section means. I mainly want to understand how it determines the current drain when using difference resistance to get the same gain, and how it affects the op-amp.
I am reading this from Understanding Basic Analog – Ideal Op Amps from ti on page 3 at this link: https://www.ti.com/lit/an/slaa068b/slaa068b.pdf?ts=1607026009319


texts: Software to translate code description to PCB design?

texts: Is there an application available that allows you to define each component and it's connections in a circuit (kind of like Entity Relationship Diagrams in database design), and have the application generate the most logical use of space on a PCB for you?


texts:
I am a newbie and I am trying to understand how particular register (in lpc1347) works. Maybe it's common problem, maybe it's specific to lpc boards. I'd like to learn how GPIO and PININT register works, so I have started learn lpc1347 manual, but I am stucked in point while changing GPIO register. Let's take, for example GPIO register called NOT, which toggle a pin to opposite state. I can modify it in two ways:

pointerToGPIO->NOT[0] |= 1 << pin;

or

pointerToGPIO->NOT[0] = 1 << pin;

NOTE: Both of them works correctly.
The first way is called (surely) read-modify-write, because I must read NOT register, make OR operation and save it.
The second way is to save pin mask directly. I have made a simple research and LPCOpen use the second way:

STATIC INLINE void Chip_GPIO_SetPinToggle(LPC_GPIO_T *pGPIO, uint8_t port,
                   uint8_t pin)
{
    pGPIO->NOT[port] = (1 << pin);
}

Of course there are several registers in the GPIO that I have to modify with OR/AND masks...My question is How do I know when I don't have to make RMW operation and modify register directly? I have searched in the manual, but I didn't find any mention how to distinguish it. Is it any recipe how to do it properly? Should manual tell me the truth or this is general knowledge how to distinguish it?


texts: What are actual additional benefits of using high voltage

texts:
What are the actual additional benefits of using high voltage in transmission lines besides reduced material costs, power losses, and the fact that devices that use higher voltages for the same power  will be smaller and lighter?

Is there still something else, because it seems to me that the high voltage only achieves two things: reduce the cost of the materials and reduce power losses.


texts: Why doesn't this mosfet saturate in a configuration and not the other one?

texts:
I am playing around with Mosfet specifically irf 540.According to the datasheet ,Vgs is about 10 volt.I added 2 resistors to 2 different circuits to see if there is a difference in the component's saturation.
I applied then 3 volt to both gates .Surprinsingly the first circuit saturated and the other didn't.I have got then serveral questions:

Why did the Mosfet saturate in the first configuration  and not in both?
Why did it saturate with 3 volt and not 10 ?
Does  this circuit really need a resistor following drain or source?
What additional considerations to take in if i want to drive a load which draw at max 1 A at 24 V?

Here is a schematic of my simple circuit:


texts:
I am trying to increase the ON time of a Relay. The Relay is turned ON from ULQ2003 by a 1 Sec ground pulse on its OUT1 Pin. I am trying to increase it to approximately 3 Sec. The accuracy of pulse width is not important, even if  it varies within +/- 1 sec that is fine. But i don't want to use 555 timer or 74121 monostable for increasing the pulse time.

Is it possible to achieve this using some simple passive components or a  transistor or darlingtons from the ULQ2003 driver?

Edit:

I have improved the image and included the pulse-time in it.
The Relay is 12V relay now. In my earlier question it was a 9V relay.


texts: Two multimeters in continuity mode, only 1 buzzer

texts:
I have two identical digital multimeters both with new batteries.

I set both to continuity mode and connected the leads to each other.

Only one of the meters buzzers went off.

They both work independently.

I am puzzled.


texts: Best way to test a high current pcb design 70A @ 12V

texts:
I designed a circuit (MOSFET HBRIDGE) that Should Be able to handle 70A @ 14V. Now that the board is sent out I am on to thinking about how to properly test it.

Right now the most logical way I have to test it is to take a bunch of power resistors and hook it up to a SLA 12V Battery.

I would start w/ 15A then maybe 35A then 50A or something to that extent. I would monitor the temperature on both the fets and the traces themselves.

Any other suggestions would be appreciated.


texts:
I want to measure a current with Acs712 and my arduino.
I do some math before stating measuring.
I want to measure mA, 20 to 300. The arduino's analog precision is 1024 on 5V.
The sensor can measure 185mV/A, and it gave us 2.5 V when read 0A.

If i want to measure 20mA the sensor give me: 185mV: 1000mA= x mV : 20mA
X = 3.7 mV < 4.8 mV of analog resolution for arduino.... I can't measure it.

But if I want to measure 50mA -> X = 9.95 mV < 4.8 mV of analog Arduino's resolution.

Remember you must add 2.5v of offset! 2.5v + 9.95mV = 2.50995 V
Now you read at the analog: 1204 : 5V = x : 2.50995 V - > 514.03

I think if I measure this small amount of current, the sensor output still to noisy...
Is it a good idea if I add an Exponential moving average for stable the output?


texts:
I'm working with energia for the launchpad 430 and have a rather specific question to make: is example A the equivalent in power consumption has example B, or is it that B drains more power? Thank you.

EXAMPLE A:

void setup() {
  boolean flag = false;
}
void loop() {
  flag = true;
}

EXAMPLE B:

void setup() {
  boolean flag = false;
}
void loop() {
  flag = !flag;
}


texts: I'm new to op amps and I'm trying to grasp the concepts. Starting with a simple op amp buffer, with the output connected to the inverted input. One rule states that the op amp tries to keep the inputs at the same voltage, but before any voltage is applied, the inverted input would be at 0V if the voltage was sufficient enough wouldn't the output voltage be equal to v+ due to saturation? And if this was true, why wouldn't the inverted input equal this also? I'm trying to figure out where my understanding is wrong.


texts:
simulate this circuit – Schematic created using CircuitLab

Here's a little schematic I built for my 27MHz colpitts oscillator, which outputs approximately 120mVpp. Since the common base is less dependent on frequency, is less prone to distortion and has high gain I chose it over the CE amp. I used several different transistors in the place of 2n3904. Even some soviet ones with GBP pf 800-1000 MHz. I simulated the schematic in LTSpice and got this result.

The output is 2.4Vpp, so the gain is 20. And here's the first confusing part: So far I've learnt that the gain of CB amp is

A=Rc/re

Rc= 5000

re=25/Ie

Ie, in the DC state, according to the same simulation is about 1.44mA, so re should be about 17 ohms. The gain in that case should be about 300. I am not expecting this kind of gain in reality however it is a huge jump from 20 to 300. I do suspect that on high frequencies there is some effect that I am not aware of. The CB configuration should basically eliminate the Miller effect, and I don't know what else might cause the drop in gain.

Anyways it's not where the problem ends. After building the amp on the desk the gain was even smaller than expected 20. The output Vpp was around 300 mV, a bit more than 2 times larger than the input (every transistor behaved like that, even high GBP ones). I should also note that the same high GBP transistors performed much better when used in CE configuration (around 2Vpp), although with quite a bit of distortion, which was why I decided to use CB.

I disconnected the signal source to check if the DC biasing etc was done correctly, and the voltages on each node were around the same as in the simulation.

I decided to make a frequency domain analysis in spice and here's what I got:
This is with the 2N3904. I suppose that transistors with higher GBP will have different curve (although not sure about that). Anyways the gradual roll-off is very visible.

Since I used the transistors in CE configuration effectively I highly doubt that the transistor is the problem here. I suppose the problem lies within the schematic itself, although I fail to find it. The question is: why does the schematic behave like it does in real life? Also how can one fight the gradual roll-off if it is possible at all?

UPDATE:

After reading the suggestions, reduced the effect of low pass filters by reducing the resistor values, which also increased emitter current. Ended up using this circuit, which gave a gain of about 5. It's probably very suboptimal but, it worked better than the last one. The output was about 700 mVpp with input of 120 mVpp.

simulate this circuit


texts:
I have a bunch of these, and I can't remember what I thought they were when I bought them. I've googled a ton of possible (yet conflicting) potential value options. Looking for some expert advice.

The only markings on them are: "0.1 K 100"


texts: Danger of inserting knitting needles into an electrical outlet

texts:
When I was a little kid (read: inexperienced), a friend of mine claimed (as his mother warned him) that putting metallic things into an electrical outlet is dangerous. Kids are curious. In order to believe in the claim, I had to insert knitting needles into a typical USSR electrical outlet with two holes and without ground (Type C - CEE 7/16 Europlug).
I think we had the following mains electricity:

Residential voltage 220V
Three-Phase voltage 400V
Frequency 50 Hz

The knitting needles looked like the image below: two metallic needles connected with a plastic tube. The length of the tube was about 0.5 meters (1.5 feet).

I felt how the current flowed through my arms and chest and I quickly removed the needles from the outlet. I felt "energized" (I assume it was just an adrenaline rush). During this dangerous experiment, the plastic tube burned right in the middle of its length.
Up to this day, I don't know the answer to the following question:
Why the plastic tube connecting the metallic needles burned right in the middle? I assume the plastic tube had zero conductivity.
Additionally, how come the little kid survived? Did the current split between two paths: hand-chest-hand and needle-tube-needle?
Please be an adult and respect others when answering.


texts: Can I run my audio mixer off the battery powering my amplifier?

texts:
Background info:

I have a small battery powered 25W amplifier/speaker combo. KustomSound CB25X, with two 6V 4.5Ah SLA batteries wired in series for 12V. Fully charged, the voltage seems to be close to 13V.

I also have a mixer - Yamaha MG06X, which runs off a 12V wall wart. The voltage off the wall wart is 12.3V.

The mixer is rated for 24W but it's unlikely I'll ever be using it at full power. Same goes for the speaker.

I also got myself a little preassembled LM2577 DC/DC switching voltage booster from online.

My question: Can I run the mixer off of the amp battery with the DC/DC booster? Can it tolerate a volt or so above its rated 12V e.g. when the battery is fully charged? (Because that DC/DC chip can't lower the voltage, unfortunately.)

Alternatively: can I wire the DC/DC booster across just one battery? Will that be bad for the amp or the batteries or the mixer? EDIT: I've been informed that's not a good idea, so ignore this paragraph.


texts: Need help regarding power use for an Arduino

texts:
I'm trying to build a rechargeable LED prop using Neopixel sticks.

There will be a lot of them, potentially up to 15 sticks (128 LEDs) if such a thing is possible, but at least 10. (80 LEDs) I'm a total newb, how do I figure out if and how I can safely power that much, and what does one need to do to drive a lot of an Arduino?

Pointers to other links where I can learn what I need would be fine!


texts:
my son and I are working through this book called The Thomas Edison Book of Easy and Incredible Experiments.

We are stuck on the first experiment where you make a switch to connect a battery to a light bulb.

We are using coaxial cable (removing the sheath and using the outer wires) since that’s what we have available as scrap.

We are trying C and D cell 1.5V batteries.

We also have an LED nightlight bulb (120V 50/60Hz 0.5W 30mA) and also an LED that we pulled out of a little toy light that had 3 LR41 button batteries.

We cannot get any combination of lights and batteries to light up, even bypassing the switch and just connecting wires to batteries and lights.

Any tips would be greatly appreciated.

Photo of stuff we’re using: https://share.icloud.com/photos/00aJ0FK-4LmXcBRfzoptr7M5w


texts:
The Melexis MLX90372 datasheet says that it can output either SENT protocol or PWM. I do not see anywhere in the datasheet how to put it into "PWM Mode" as they call it.  Nor do I see how to configure the PWM frequency 100Hz-2kHz.
Does anyone know how to do this?


texts: Is there a switch that can replace Voltage Controlled Switches?

texts:
This is the voltage controlled switch in the LTspice.

Is there a switch which can replace it? I need a switch for a schematic. At first, I used a transmission gate switch, but the simulation of the circuit was different than it was when using a voltage controlled switch. I want to convert a circuit from LTspice to Cadence Virtuoso, but I don't know if there is a suitable part.

I use the hspice in the Cadence Virtuoso

The size of NMOS and PMOS in the transmission gate switch is 18µ/180n and 36µ/180n. If this size is not good, please let me know. Thank you.


texts:
Why will the \$I_C\$ flow to the opposite direction for an ungrounded system? The red arrow means the current flowing direction at the when there are three capacitors connected the three lines(A,B,and C)

Now if there is some damage or problems about the capacitor which is connected with line C,so now there is no capacitor connected with C,we can find the direction of \$I_C \$ is opposite than the others,as the black arrow shown

Why does the \$I_A +I_B\$ flow into the line C?there shouldn't be a loop,even if there were,the \$I_C=I_A+I_B\$,so there should be no current,Why will the \$I_C\$ flow to the opposite direction for an ungrounded system


texts: Micro Watt Meter in Extreme Low Temperature

texts: I'm using a solar panel in the Arctic and I want to measure the power it delivers to the associated sensors. Is there any recommendation on a watt meter for this environment? The temperature is expected to be lower than -50 Celsius degrees. The voltage ~10V and current ~10mA.


texts:
I want to measure Li-pol battery voltage with STM32 MCU. I power STM32 with 3V so I need a voltage divider for battery connection (Li-pol max voltage is 4.2V). Moreover, I'd like to add N-channel MOSFET to prevent battery discharging through the resistors.

There are a lot of similar topics here, but most of the decisions use extra BJT to drive a FET (Low Current Battery Monitor Detail Question) or a capacitor to automatically turn off the transistor (Selecting low power mosfet for battery monitor).

I'd like to use only one MOSFET in such a way:

The only problem with this circuit (as I see) is the voltage at the source pin.

For example, if I use R1 = R2 = 10K then in open state there will be 2.1V at the source. MCU GPIO maximum voltage is 3V and 0.9V (3 - 2.1) will be not enough for FET to remain in open state.

But if I use R1 = 20K, R2 = 10K the maximum voltage at the source will be 1.4 V and 3V from GPIO should be enough (V gate threshold = 1.06V).

Are there any other problems with this circuit because of which it is so unpopular?


texts:
I have a PIC18F4680, and I want to interface with an Ecan module and UART at the same time. I am sending the UART message correctly and reading the CAN bus properly, but when trying to do both things at the same time the microcontroller stops working. Is the PIC18F4680 able to manage both communications without crashing?

If it is not possible to work with both communications at the same time, which microcontroller should I use? The programming code is done for MicroC so I would prefer a microcontroller that is supported by MicroC.

I have tried to simplify the firmware architecture, but still it doesn't work. Here is the code:

Msg_Rcvd = CANRead(&CAN_RxID, data_rx, &rx_DLC, CAN_Rcv_Flags);
id = CAN_RxID;
dato = data_rx;
UART1_Write('$');
UART1_Write(dato[0]);
UART1_Write(dato[1]);
UART1_Write(dato[2]);
UART1_Write(dato[3]);
UART1_Write(dato[4]);
UART1_Write(dato[5]);
UART1_Write(dato[6]);
UART1_Write(dato[7]);

I have saved the values read from the CAN bus in different variables to avoid using both communications at the same time, but it is not working. I am not familiar with interrupts, and I do not know exactly how to use them. Has someone done something similar with interrupts?


texts:
I try to measure Earth's magnet field with LIS3MDL. This chip is operable in (-40..+85) deg. When the temperature is lower than -10 deg, the chip measures becomes wrong. The plot of raw measures after soft-iron and hard-iron compensation are in the plot below. Yellow series is the temperature (right axis), blue series is X, orange axis is Y, grey axis is Z.

According AN4602, the chip can compensate thermal drift with internal temperature sensor. This sensor is enabled in my application (yellow series is obtained with another sensor). Why the chip provides wrong magnetic data?


texts:
I want to replace some timers with a PIC16F887 micro-controller. The problem is that the input voltages to the I/Os is going to be 24V which is too much. For the output part I was thinking about using a relay module. I'm stuck on the input part. How can I use the 24V as a input to the micro-controller?

The application is simple. When a input pin goes high the output will be enabled after a certain period of time (When 24V is received from the input the output will send 24V in other words). The time will be adjustable trough some push buttons. The times will be displayed on a LCD.

This question is tied to a different question I asked from the forum before. A user recommended a similar cheap solution which is already made but I want to build one just for a personnel project.


texts: Voltage Controlled-Phase Shifting Circuits

texts:
Forewarned: I have a somewhat good understanding of signals and systems but electrical engineering circuits aren't my strength.

Question: Is there a simple circuit that can introduce a voltage-controlled phase shift on a FM signal (especially for frequencies in the 10's of kHz)?

Complication: There are tons of results that pop up after Googling for voltage-controlled phase shifting (VCPS ) circuits but I can't be sure which are frequency independent and all the other potential limitations that might not satisfy the intent of my question.

This IC would seem to be suitable but I'm not completely sure.

Here's another simpler example I found closer to the frequency range I am interested in.


texts:
With reference to my first question,  (+-5VDC to 4-20mA Converter), as you can see from answer from my first question, I have succeed to create 4-20 mA from 0-5 V with using three TL081 operational amplifiers.

Now, I have to create -1.25 V and -12 V from +24 V supply voltage. I have read all questions and explanations about negative voltage. I know I can pin my -12 V as ground and get over this problem but I cannot do it because of other parts of my system. So I have to invert voltage to -12 V and -1.25 V. I have tried to use ICL7660 but its output voltage is not stable. Also there is a 20-50 mV difference about aimed voltage values.

Also I cannot divide -5 V to -1.25 V accurately. I have tried to use basic voltage divider circuit but voltage drop on resistance is too high that I cannot take a stable -1.25 V. I had to lower resistance values so voltage drop had lowered, but I passed the maximum current value.

Do you have any idea about how I can achieve -12 V and -1.25 V accordingly and stable from +24 V supply?


texts: Low power design, choosing correct buck-boost converter for LiPo battery

texts:
I want your opinion on subject considering low power applications. I want to build basic loraWan tracker with Murata Lora module(3V3), and I want to use LiPo battery. What Im struggling with is power design circuit. I want a dc/dc buck-boost converter which can work from very low voltage input(to use maximum from the battery) and very low power consumption.
For now Im considering this IC(other suggestions welcomed):

https://www.analog.com/media/en/technical-documentation/data-sheets/3106f.pdf

What do you think about it?
Sorry about my bad english.


texts: Feeding a signal directly to an ADC or amplifying (active) it beforehand?

texts:
I am working on a project, where signals have the following characteristics (skip this if you are familiar with EEG):

amplitude in 10's or 100's of microvolts
frequency range: 1 to 100 Hz
Low SNR ratio

There is a open-hardware source for a device to measure these signals, called openBCI, which adds to the signal path a TVS diode presumably for protection, and a passive RC LP filter, which from my understanding is there to attenuate high frequency noise because of the low SNR ratio of the signal (not really sure about this though), and then feeds it directly to an ADC. Note the ADC is specific for this purpose (ADS1299)
My question is this, would this design be improved (by a margin), when you:

add a DC blocking cap
Use an active amplifier for each signal, this includes amplifying the reference signal (which the In-Amps in the ADC use as the negative input). I think that although amplifying the signals prior to amplifying it against the reference signal would also amplify the noise, but the amplified reference signal would take care of that in the In-Amps in the ADC.

Am I correct in assuming that step 2 would not give rise to more noise, or is amplifying the signals reference taking away the reference signal from them rather useless? Thus why the openBCI designers designed it that way, or is it purely a cost/space problem?


texts: Will a 5.1V adapter charge a device that currently uses a 5.5V adapter

texts:
Possible Duplicate:
  Choosing power supply, how to get the voltage and current ratings?

I have a device (a Geneva XS portable Bluetooth speaker) which is supplied with a power adapter that specifies the output as DC 5.5V and 2A with a concentric barrel output plug. Before I bought it, many of the reviews I read of this speaker commented that it was a shame that the device did not use a USB port for charging. I certainly agree with the sentiment, as I already carry around a charger for my various "iDevices" and other things, and it would be nice to simply use the existing adapter and cables that I already carry to charge the Geneva when I travel. To that end, I resolved that I would see whether I could buy a cable with USB to concentric barrel plug to see if I could indeed only add an extra cable to my load, rather than have to carry an entirely new charger. Anyway, I have found such cables on ebay, but before I buy, I am wondering if my 5.1V 2.3A iPad charger will actually manage to pass any charge to the 5.5V 2.0A hungry Bluetooth speaker...or am I just wasting my time? Cheers, Harry.


texts: LM35 negative temperature sensing circuit

texts:
I'm planning on using the LM35 temperature sensor to measure both positive and negative temperatures. The recommended schematic to measure negative temperatures without a negative voltage supply is this:

I understand that the role of the diodes is to lift/offset the negative pin from GND. What I don't understand is: What's the role of the 18 kOhm resistor?


texts: What is the practical limit/best practice for the average rectified output current of a diode in AC applications?

texts:
Background: As part of a little project I'm looking to add a diode to a hair dryer to cut the output in half.  This is the circuit:

The potential diode in question is at the bottom, and the simulated current through it is in the center graph: 2.184 A peak (edit: 3.1 A).  By my math that would mean right about 0.7 A average (edit: 0.99).  Technically, this would fall below the 1.0 A spec for average rectified output current of a 1N4004 diode.  However this sheet by Vishay states

  IFAV  decreases  with  an  increasing  value  of  the  reverse  voltage during the interval of no current flow.

In my case the reverse voltage is 120V sinusoidal; potentially 240V if used in another country.  Unfortunately the 1N4004 datasheet doesn't seem to indicate the reverse voltage for the IFAV spec.

So for my education, ultimately my questions are:

1) Practically, should a 1N4004 diode be able to handle 0.7A (0.99) IFAV with 120-240V reverse voltage for an indefinite amount of time?  Or is that too close to the spec, and reducing life of the part?  More generally, how close is too close to the IFAV spec?

2) If practically possible, would best practice be to use the 1N4004, or a 1N5404 (3A IFAV)?  A 1N5404 would be harder for me to fit but is probably doable.


texts:
so i firgured this might not be the right place exactly to ask for help about a thermodynamics type of question. but i found some electrical questions present so i decided to post it here too for some help.

so basically i have been doing an experiment on steam power

and have measured and calculated quite a bit of data:

voltage,
load resistance,
current,
power,
rpm of turbine,
angular speed,
k constant,
torque,
heater's power,
boiler's temp and pressure,
time taken for water mass to reduce by 100g

and now im stuck at this question which im not sure of the "correct way" to go about it.

The question was to find out the overall efficiency and plot it against resistance, so resistance is pretty simple, but the overall efficiency is puzzling me at the moment.

my guess would be that:

overall efficiency is = (power generated(calculated from voltage and current values) + mechanical power generated from the turbine (Pmech= torque * angular speed)) / (the total net power introduced into the system which is the heater's power).

i would like to know what you guys think of what i thought of to solve the question?


texts: If counter-emf is zero, why is COE violated?

texts:
I've been modeling this thought experiment a for a while now:

If in a electromagnetic system, the induced emf wasn't opposing the change, but increasing it, we're getting energy from nowhere, that makes sense when I consider conservation of energy & Lenz law.

What if a motor's coil has counter-emf = 0, and has constant current with increasing angular/linear velocity over time, or a current carrying rail & rod system, where the rod is moving without any counter-emf to reduce the applied constant power(constant voltage & constant current).

I don't see how this case violates conservation of energy.
Whatever kinetic energy gained by those moving components is from the power source, likewise, for the heat lost.

Unless, I'm missing something?


texts:
I've came across this tutorial purpotedly claiming to allow a CD ROM drive to read DVDs by changing the track pitch of the laser head on the drive;

http://www.haklabs.com/2007/modify-your-cd-rom-to-watch-dvd-movies/

Wikipedia states: "DVD uses 650 nm wavelength laser diode light as opposed to 780 nm for CD. This permits a smaller pit to be etched on the media surface compared to CDs (0.74 µm for DVD versus 1.6 µm for CD), allowing in part for DVD's increased storage capacity.", which does share some resemblance to the explanation given in the tutorial linked above, only the numbers are of by a significant margin.

  en.wikipedia.org/wiki/DVD

Then, an Anandtech user claims hogwash;

http://forums.anandtech.com/showthread.php?t=1378104

So, what's the conclusion on this?


texts: Do I need to program a USB-Serial FTDI chip before using?

texts:
I'm building a PCB with an ATMega chip.

In the past, I've used Sparkfun's FTDI breakout board to program the ATMega.

However, I'd like to implement the FTDI chip and USB port on my own PCB, thereby bypassing the need for the breakout board.

Can I simply copy the schematic from Sparkfun's model, plop the chip down on my board, and expect it to work? Or is there some firmware I need to load onto the chip before it is able to translate USB to serial?


texts: Generate a printed circuit board from code?

texts:
I'm just getting started with electronics by way of Arduino. My Arduino kit came with a little ad for a website that takes PCB designs and prints them for you for a pretty cheap price.

But how do I get from a program that runs on the Arduino to a circuit that can be printed on a PCB? This is probably wishful thinking, but is there a mechanical way to "compile" Arduino code to a PCB layout?

Or, would I need to get someone with real EE experience to hand-design the PCB?


texts:
I am trying to work out the order of a filter but can't seem to figure it out.
The filter characteristics are below

I also have the Equation

At = attenuation point (10^(-60dB/20)) = 1x10^-3

f = attenuation frequency = 3125MHz

fc= center frequency = 3000MHz

However i can't seem to get this in terms of N.


texts: Centre Tapped Transformer Full Wave Rectifier Output Voltage

texts:
I'm currently constructing a power supply for a small helium neon laser tube, based on this circuit:

The output of a centre tapped transformer (small neon sign transformer), is rectified by two high voltage diodes, smoothed by around 1uF of capacitance and fed through a ballast resistor which regulates current to the laser tube itself (due to it's negative resistance characteristic). I know this isn't the most efficient power supply design, with significantly more energy being lost as heat in the resistor than is consumed by the tube itself, however, the entire system into which this laser is being integrated is intended to resemble quite accurately, the early helium neon lasers of the 1960's, which as mentioned in the below link, used a power supply similar to this.

This brings me to my question. On the site where I found the original schematic (here), the author mentions a voltage of 7.07kv across the capacitors (5*1.414), but it seems to me, as both taps are being utilized, the voltage would actually be 14.14kv, the peak voltage of the 10kv input, is this correct, or am I missing something?

Thanks in advance for any help!


texts: K - Map essential and non-essential prime implicants

texts:
Here is the min terms for K - map simplification:

F = summetion m(0,2,3,5,7,8,10,11,14,15)

May i know, if i draw the graph means, what will i get Essential and Non Essential prime implicants?

Can anyone help me?

thanks,


texts:
I am having confusion regarding ROC of z transform of u(-n+1)

z transform of u(-n+1) is given by

$$X(z)=Z[u(-n+1)] =
\sum_{n=-\infty}^1 z^{-n} =\sum_{n=-1}^\infty z^n = z^{-1} + \sum_{n=0}^\infty z^n  $$

ROC given: 0<|z|<1

While I understand that |z| should be less than 1 so that $$\sum_{n=0}^\infty z^n  $$ converge, I don't understand why |z| should be greater than 0. Please clarify this doubt.


texts: What happens when I pass really high current through the gate of a thyristor?

texts:
I have a thyristor that requires 120mA(from datasheet) gate current  for triggering. I'm giving DC to gate and AC is connected across anode and cathode.

Now, according to theory, with dc triggering the SCR should be on for the positive half cycle and open for the negative half cycle. Thus, if I connect an oscilloscope across anode and cathode, I see a negative half cycle sine wave.

Now if I keep increasing the gate current(above 120mA) , I see the negative peak of the (-ve)half cycle decreasing and at some current(~850 mA) the voltage across the thyristor becomes zero. Which mean the thyristor is conducting throughout the AC cycle.

Why isn't the thyristor blocking the negative half cycle of the AC?
What exactly is happening here internally?

EDIT:

This is a diagram I drew for this question. My actual setup is physical but is exactly the same. The DC source is a current source in my lab. The AC is given from a variac. And the DSO probes are at anode and cathode of U2.

The thyristor used is not available internationally. (HTT90N600D) I have my doubts about the availability of the datasheet. I have it personally, but I can't upload it on here I guess.

In any case, what I really wanted to know was what happens to the gate(and neighboring junctions) of ANY thyristor when large current passes through.


texts: What happens to the printf statements on a cross compiler for embedded devices?

texts: What happens to the print statements on an embedded tool chain where the micro controller has no display attached to it? Does the program crash? What about all the other several c dependencies when we use the standard header files on a microcontroller with features that a modern computer does not have?


texts:
Can anyone help identify connector type for A & C below or suggest site/keywords I could use to narrow search?  I have sent inquiry to several sites selling automotive connectors and Googled extensively but no success :-(

Update for anyone else interested:  Contacted Metra directly and they have no solutions. Poured through Mouser and no plugs which match socket.


texts: What is the best way to solder a large flat SMD shunt resistor so as to minimize joint resistance?

texts:
I have a BLDC motor controller that uses a high side 0.001 ohm current sense resistor (CSS2H-5930K-1L00F) and a MAX40201FAUA (50 V/V) to measure the current during motor operation via a Teensy 3.6 ADC. I am trying to calibrate the current sense hardware to the Teensy 3.6 microcontroller, but I am having issues with the MAX40201 outputting values way too high for the known current passing through the resistor. I measured voltages on each side of the resistor with my oscilloscope and it showed a voltage drop of 30-80 mV for a 2.5 A known load across the 0.001 ohm resistor!

So I am thinking that the solder joint is bad. During soldering, I used a stencil and a rework gun to solder the SMD components. For the high amperage traces, I later added higher temp silver bearing solder with a hand soldering iron to reinforce them. I thought this would help the traces hold up to the high intermittent current.

Since my process apparently led to either incomplete fusion of the large flat current sense resistor or capturing flux between the resistor and the PCB, what is the best method for hand soldering these types of components so as to minimize joint resistance?

Image of the PCB section housing the 0.001 ohm resistor:


texts: Does this still count as a class B amplifier?

texts:
The PNP's emitter terminal is grounded instead of  the collector terminal.

is the formula:Pi= (Vcc)(Vout peak)/(pi*loadResistance) still applicable for this?... the out put has crossover distortion and Im not so convinced that using the default formula for efficiency would give me the right answer for this circuit.I mean you cant use Po= (Vop-p)^2/8RL right? cause the o/p isn't a sinewave anymore?


texts: How can I calculate the frecuency of this circuit?

texts:
If RA=RC= 15Kohms, RB=44Kohms and C = 8.2uf, Which will ve the frecuency?

It's like a astable circuit with 555, but the resistence RC conected to Discharge is confusing me.

Thanks!


texts:
simulate this circuit – Schematic created using CircuitLab

simulate this circuit

Right now my configuration of my circuit is this:
http://i.imgur.com/2x5nGcf.jpg

The only difference is that now I have 5V being fed into the +Ve rail of the op-amp and 3.3V fed into everywhere else. This is within the specifications of the LM358 minimum voltage for the single supply rail (3V) and the offset difference from rail to input (+Ve - 1.5V or 3.5V in this case) as shown here:
http://www.ti.com/lit/ds/symlink/lm158-n.pdf

The circuit works and by adjusting the light of the opto-interruptor I can see a change of 3.35V (When light beam is unobstructed) to 1.53 (When it is), although I would like to have a larger difference so that the the system is more sensitive to changes in light levels.

So I decide to try to use this YwRobot 545043 breadboard power supply and measured 14.63V across it's positive and negative terminal. I have the +Ve (Pin 8) being fed from this, and all grounded nodes and other sections of the circuit going into the - pin of the power supply so I have one single common ground. In the circuit above all instances of 3.3V is replaced with 5V (so 5V being fed into the opto-interruptor).

However now the op amp will not output and there is no change due to the light level. Is there something I'm missing?


texts: Alternative to optocoupler? Other switching devices?

texts:
I have a part that classifies what kind of power I get on ethernet by presenting different loads. For example, the part needs to have a 100 Ohm resistor across two of its pins, and the part will output a high on its output pin if the power is good (Ethernet is able to supply power). The device then switches to a 30 Ohm resistor, and if Ethernet gives it power, it'll output another high. Then it'll switch to let's say a 10 Ohm resistor, and maybe Ethernet will not supply any power, so it'll output a low.

So, the microcontroller needs to be able to disconnect and connect different resistances. When testing the 100 Ohm resistor, the 30 Ohm and 10 Ohm needs to be disconnected. When testing the 30 Ohm, the 100 Ohm and 10 Ohm needs to be disconnected. So, I know that I can use an optocoupler to connect/disconnect a resistor from the two pins from this testing part. All I have to do is output a high from the microcontroller, and the resistor will be connected.

So, essentially, I need a way of switching on and off without affecting the resistance values. I don't want to use optocouplers because they're expensive. What can I do this with? Can I use a transistor as a switch? If I do, does this affect the resistance value that the part reads across its two pins?


texts:
Using proteus I designed this amplifier:

But I got this result:

I don't know what is the problem in my design. I've been changing the values of the linking capacitors but didn't get any result.


texts: How to derive the voltage equation of capacitor in a circuit?

texts:
Q2 b) in particular, my first attempt was use KVL:

Vs = Vr1+Vc

into

Vs/2 = dvc(t)/dt + vc(t)

I then tried applying into laplace domain ->
25 = s*Vc(s) - vc(0) + Vc(s)

Vc(s) = 75/s+1
vc(t) = 75(e^-t)
but the answer is vc(t) = 25(1+e^-t) V

What did I do wrong?


texts:
I am trying to replicate the circuit in this paper: http://chrisharrison.net/projects/electrick/electrick.pdf

I have followed the schematic in Figure 7 and utilized Howland current source as described in the prior post: Building a VCCS with AD8220 Instrumentation Amplifier

Currently, I have an AD9850 with a 1 Vpp 100 kHz output. This wave is passed through Howland current source, which should yield a current < 1 mA.

My question now is how is the EIT field established? I am trying to understand based on Figure 1 in the paper, but I do not know how that translates to my setup. Are all the adjacent electrodes connected to each other? When I establish a current receiving pair, is Iout going to one electrode while the adjacent electrode is connected to ground?


texts:
I have this weird issue. I'm currently hooking up a 6-pack of 18650 batteries in parallel. I'm currently hitting 3.8v using the whole pack at the connector (yes, I need to charge them up). If I hook up my 5 meters of LED strip to it, I get a voltage drop in the beginning, which is really weird! Here's how I've hooked it up:

The VIN on the ESP8266 board can receive a wide range of voltage, so it doesn't matter if it gets 3.3v or 5v. The batteries won't ever go below 3.5v, so I don't need to worry about that.

The VIN pin receives about 1.3v whereas the first LED receives the 3.8v. The terminal/connector that splits the cables is simply one of these connectors. So the battery pack has a male connector, that connects to the female, which simply has two cables running from it.

What on earth is wrong?


texts: How can I control timer555 source voltage with another timer555 frequency?

texts:
How can I control timer555 source voltage with another timer555 oscillator ? I want to make a oscillator and control it`s source voltage with another timer555 saw wave oscillator. I did a 758Khz timer555 oscillator and I connected another timer555 saw wave oscillator to voltage source transistor. But It can change another timer555 voltage source only 0.8 volt.  I need 3 volt voltage source changing. For example timer555 voltage source 12 volt 11.50 volt 10.50 volt 9 volt voltage change I need. How I can solve this timer555 problem ? This is my multisim circuit. Problem is this. It only changing source voltage 0.8 volt. But I need 3 volt voltage changing.

Figure 1

okay I changed two transistor and I put only p channel one transistor. Can it work with this circuit ?   It has 6 volt and 12 volt changing voltage.

Figure 2

Figure 3
okay I want to do this. I did it with easy way fucntion generator in multisim. Voltage is 6 volt 7 volt 8 volt 9 volt 10 volt 11 volt 12 volt after 11 volt 10 volt 9 volt 8 volt 7 volt 6 volt. I want to change voltage source slowly with another timer 555 trapezoid wave with connected to it a P channel transistor. Are you sure about mosfet use ? Multisim is giving error all of mosfets to me. Square wave can not do this because when it has 0 volt signal source , other timer 555 is stopping.

Okay I added my wanted result and studing result. I want to build a control oscillator that controls the amount of voltage of a 750Khz timer 555 frontier, and then gets up and down slowly. As in the figure, the voltage will slowly decrease to 12 volts 11 volts 10 volts 9 volts 8 volts 7 volts 6 volts. Then increase the voltage slowly. Example 6 volts 7 volts 8 volts 9 volts 10 volts 11 volts 12 volts. But the timer 555 control oscillator in my work does not provide this. I want the other oscillator to check its voltage but it just distorts its signal. It is disrupting the signal when the voltage source should be slowly up and down. I'm searching its fault reason.


texts: How to know whether filter is stable given in- and output shapes?

texts:
I have this filter with

$$H(z) = \frac1{0.5z^{-1}}$$

How can I know whether this filter is stable given that \$x(n) = a^nU(n)\$ and \$y(n) = -a^n U(-n-1)\$?


texts: How to rederive the formulas for parasitic capacitance of a spherical tesla coil topload

texts:
I wanted to prove, or rederive, the formulas for parasitic capacitance of both a toroidal topload, and a spherical topload used for a tesla coil.  I thought I'd start with the spherical because the formula for its capacitance and its surface area were simpler.  I wanted to use the formula that calculates the capacitance of a plate capacitor

A problem I knew I would encounter is the distance variable.  I thought I'd go along with it anyways though.  What I ended up with was this

capacitance is in pico farads, and radius is measured in inches instead of meters.  I still had the distance "d" undetermined, and it looked toadally wrong.  This is where I got stuck.  I'm not sure if I should be asking this question here on electrical engineering stack exchange, or physics stack exchange.  Any help will be greatly appreciated!  Thanks!
Just for fun, here's the formula for the toroidal topload!  (capacitance is measured in pico farads, while distances are measured in inches.)


texts:
I was studying a book on signals and systems where it says that noise disturbances which interfere with the transmitted signals are a source of information. And the original signals are not. It mentions that higher the uncertainty in the signal transmitted, more is the information.
How can an unwanted disturbance which has no link to the signal being transmitted be so important?

The higher the uncertainty about a signal(or message) to be received, higher is the information content. If a message to be received is specified beforehand (i.e., it is known beforehand), it has no uncertainty and, consequently, cannot convey any information.

-Principles Of Communication modern digital and analog communication systems by BP lathi


texts: What could have gone wrong with my TLP222A?

texts:
I'm using a TLP222A to switch a 24V load that never pulls more than about 200mA. My circuit looks like this, ignore that the chip name is wrong.

I have 4 of these connected to 4 GPIO pins. 2 of them have, for no reason I can discern, stopped working. They show 1.15V at the input, which to me implies that the diode inside is conducting normally. The GPIO seems fine. But the output is floating, like the chip is broken.

I'm confident that I did not pull more than the on state current of 500mA nor anywhere near the peak 1A. I also used 220ohm resistors to supply 10mA to the diode, which is also well below its maximum rating.

Not really sure what else to look for, here. :/

Edit: as requested, here is a link to one of the industrial LEDs I am driving. This is the load. There are 4 of them, each on separate SSR's.


texts: How do I drive an ultrasonic transducer with an Arduino?

texts:
I am attempting to build a cat deterrent with an Arduino, something akin to this. I have figured out detection, and now realize that I need to use an ultrasonic transducer to produce the 'blast' that I need.

However, I am clueless as to how I would interface one of these with an arduino.

Does anyone have any advice?


texts: How can i trigger this watering timer manually

texts: I have a automatic watering timer that I purchase from the internet. I'm attempting to hack it into something that I can either trigger from a micro-controller, or sense when the solenoid has been opened, and respond accordingly with the micro-controller. The unit runs on 2 AA batteries, so I'm assuming its 3V, there are a number of components and then 4 leads ( two for each solenoid ) that run to a coil. I tried measuring the voltage across the solenoid when the valve opens but the way the components are configured, it makes it impossible to power, control and measure it. I also wonder if the solenoids are solenoids all at or some other mechanism. I realize that my question is some what vague, but perhaps someone has had experience taking one of these garden watering timers apart and can give me some place to start.


texts: How do you carry non-circular drilling with an SMD part in gEDA pcb?

texts:
The recommended pattern for some components might include non circular drilling, like this one:

Here's the pad layout:

As per the datasheet (bottom of page 2), there has to be one circular outline and an oval one for the notches. I'm interested in how you'd carry that along with an SMD component: gEDA pcb footprints don't include an outline layer, just pads, round holes and silk lines and arcs. Is there a standard way other than storing the outline in a separate file — the process which I still need to figure out how to make non-boring...

Carrying a round hole with an SMD component is easy and only requires a pin with flag 0x100 (IIRC). That flag tells the program it is only a drilled hole, non-plated if my memory still serves me right.

Note I still wonder why there has to be an oval hole instead of a round one, which wouldn't cause any trouble at all! The notch doesn't seem to be able to move along, right?


texts: I want to make a TV transmitter (http://electronics-diy.com/electronic_schematic.php?id=851). There is an RF transformer on it (T1:4.5MHz 1F-can-style RF transformer) that I want to find it from old radio circuits. There are a lot of transforms with different colors and different numbers on them, but I don't know which one I must use? What's the meaning of colors and numbers?


texts: Find the 4 pins for i2c on printer consumables' chip - konica minolta

texts:
I just saw this video https://www.youtube.com/watch?v=Wwd5UCi9Huw about forcing an OEM (= original) printer consumable chip to reset its lifespan counter.
However the chip on that vid has 4 distinguishable pins, whereas some other brands/newer chips for consumables don't have necessarily 4 pins, as shown here in the example of konica minolta bizhub C2X8 to C4X8 series (X being an integer variable) and many more series from that manufacturer :

(from left to right - toners chips, drums chips, developper unit chips)

How could I figure out where to wire my Vcc/Ground/SCL/SDA cables on these slave chips to do investigations with a master microcontroller such as some arduino board?
Would I burn the chips if I try any random combinations?
How to remove the black physical patch from the small chips to potentially get the micro controller model and search its datasheet? I assume it's only here to remind for what color it is suited, but I'm afraid to damage the microcontroller if I heat/scratch it.

Regards


texts:
I need to build supply for ~20 laser diodes (~150 mW each), and the question is why can't we just use a constant current power source for each of them?

A similar question for pulsed mode operation: if I would need, let's say, 50 ns pulses, is it correct that I just need to stabilize the current in these periods or is it again more complex?

Can it work this way: We start from, let's say, a 1.5 V supply, use a FET to connect diode to the supply for 50 ns and sense the peak current. Then we slowly increase the supply until we reach the required peak current. Will that work?

Any practical experience? Any comments on the last paragraph?


texts:
I need to splice out the audio feed from the hand set line (4P4C jack) to a 3.5mm audio port on a computer to interoperate the call via speech recognition. I do not meddle around too much with analog signals, nor have I messed around with phone lines. I have found several pinout guides for the 4P4C connector, but not the technicalities I need to abide by. The primary guide I was referring to was:

My overall plan was to cut a pre-existing handset coord and splice out the green and red lines. The mic lines black and yellow are not needed and will be left alone. The red wire will be tied to a potentiometer for varying volume and to satisfy the schematic (a \$500  \mbox{ } k\Omega\$ one is laying around). The audio will then be supplied to a 3.5mm jack red on the center ring with the green on the ground ring (the ring furthest from the tip). This will then be feed into the light blue jack on a computer.

Any advice? I would not like to plug this into my sound card and trash my audio in, or the whole sound card.


texts: Is the MOSFET source always connected to bulk?

texts:
I'm trying to understand all the basic connections of a MOSFET. These questions may seem very basic but I have flipped every single textbook I own and googled every single website and never found a clear cut answer to the following questions. I would appreciate all the help I can get.

1)Why is the MOSFET source connected to bulk? Is there any specific situation where the bulk isn't connected to the source? From what I have gathered, the bulk is connected to the source to establish a stable threshold voltage. If so, could we connect the bulk of a PMOS to ground and NMOS to Vdd? What difference would it make?

2)A MOSFET can function as a diode when the gate is connected to the drain. I don't really understand the physical operation behind this. However, this does make sense mathematically, as the MOSFET will always be in saturation. The current is given by, uCox(W/2L)(Vgs-Vth)^2, which means that the current graph will be quadratic which is ALMOST but not identical as the exponential equation of that of a diode. My question is, how does the performance of a MOSFET connected diode compare to that of a PN diode?

3)Of late I have seen many Rectifier circuits in IC design use MOSFET connected diodes instead of PN diodes. Is there a specific reason for this? Wouldn't a MOSFET have a relatively large area overhead when compared to using PN diode in IC design?

Your help is very much appreciated. Thanksss!!!


texts:
I have an DC motor connected across a 12V supply, I got the rpm around 200 rpm.  Armature Terminal Voltage of 9V. Winding resistance = 1ohm
How can I find the torque of the motor and the Input power without using an external device.
EDIT:The External Device is stalling the motor in this case.


texts: Trying to Build a voltage-driven smart shunt/threshold switch

texts:
I'm trying to build a smart DC switch that measures the input voltage (3V to 40V)1 and determines to which output pin to send it, similar to this threshold switch idea or a SIP3242 for Vin, not load current.2 It should be based on the below logic:

If (Vin > 35V OR Vin < 3v) Then send to GND (via a crowbar circuit?; too high or low)
Else If Vin > 9V Then send to buck circuit
Else If Vin >= 7V Then send to Vout
Else send to boost circuit

I'm not sure what components I need and how to arrange them (schematic), if I can't buy such a device in IC form. (What would such a thing be named?) I am thinking of using a level-shifter to supply shifted Vin to a micro-controller (such as an ATTiny) as analog input, calculate the value of initial Vin and activate an appropriate relay. Is this a reasonable starting point or is there a better/simpler approach using transistors, op-amps or other devices?

I already have the buck and boost circuits designed (using MC3X063As from TI).3 The initial design uses a manual SPDT to send Vin to the buck or boost branch of the circuit. I'd like to replace that with something that doesn't rely on a human to decide what path must be taken (id est, what I'm trying to design/build).

simulate this circuit – Schematic created using CircuitLab

SW2 is what I currently have. SW1 is what I'm trying to build/buy.

3V to 40V is the range a MC33063A can cope with (according to the data sheet), although I'd like to limit it to 35V to be safe. (That's the rating of my caps, although some are rated for 50V.)
I'm not trying to immediately pull the voltage down to 7V (as would be done as per this answer, which I think would waste a lot of energy as heat), although that is the ultimate goal, but determine to which switching regulator branch to send it.
From what I understand, a MC3X063A can be wired to either buck or boost (but not switch between them of its own volition).


texts: Proper Windows 8-64 bit driver for Arduino Yún (Yun)

texts:
I am trying to setup Arduino environment under Windows 8-64bit running on VMWare Fusion 6.0.2 host machine.
I connect the Yun to my windows machine and the device get detected under windows but windows is unable to find proper driver for my Yun Board.

So I have opened the windows device manager to select a proper .inf file for my Yun Arduino.
So I have gone through following steps:

1-Going to Device Manager
2-Selecting OtherDevices (Arduino Yun)
3-Update Driver
4-Browse my computer
5-Let me pick from a list of device drivers on my computer
6-show all devices
7-picking the "arduino.inf"  file that exists in the x86 (32-bit) version of the windows Arduino IDE 1.5.4r2 under drivers folder.
8- Few seconds of progression and then BOD Windows crashes!?! (Error message is BAD_POOL_CALLER)

I can not collect information on the reason of that fatal crash under my virtual machine.

I am wondering is there something wrong with my Win8-64bit machine or there is a problem with its drivers !? smiley-sad-blue

It is noteworthy that in fact I programmed my Yun board in my MAC system via Arduino 1.5.4Beta IDE and it seems it works  perfectly in my MAC system so maybe there is nothing wrong with the Yun board itself.

What is the chipset that is used Yun board for USB communication and the board programming which is attached to board's small micro usb connector? I could download proper drivers from its vendor.

(I have asked a very same question on Arduino.cc but not reply I hope I get an answer here)

Thanks


texts: What kind of gate(s) can I use for this logic?

texts:
I'm trying to combine two digital inputs to get the following output. What kind of gate(s) can I use to get this? I know that no standard logic gate would work. 'X' means doesn't matter.

IN-1    IN-2    OUT
0       0       0
0       1       1
1       X       0


texts: How does multimeter AC measurement work?

texts:
How does a digital multimeter measure AC voltage? My guess would be that the AC voltage is rectified and filtered into a DC voltage which is then measured, giving the peak voltage of the AC signal. Am I correct?

A follow up question: I remember reading from somewhere that multimeters cannot very well give accurate AC voltage measurements if the signal is not a sinusoid but a square wave for example. Is this true? If so, why is this? If AC measurement works by rectification into DC as I assume, shouldn't they measure other types of waveforms just as well?


texts: Current Rating of a device (how does this change when changing the voltage)

texts:
Let's say you have a device that is rated at the following:

550 amps @ 12Vdc  (heat)
Max Voltage = 48Vdc (insulation material max voltage rating)

I am mainly concerned with the heat, we could say the device is able to handle:
550A x 12V = 6,600 Watts

So if you use the same power to determine how much current it can handle at 24Volts, would the statements below be true?

Current x 24V = 6,600 Watts
Current = 275A

275Amps @ 24Vdc?

Current x 48V = 6,600 Watts
Current = 137.5A

137.5Amps @ 48Vdc?


texts:
I am trying to connect an AC line filter (rated for 115/250VAC) on the load side of a 24VAC transformer (part# BPD2G, datasheet here).

The first filter model I used is Delta's 03DBAW5.

From the datasheet, I couldn't really figure out what each wire was. I assumed the green/yellow cable is the neutral line, so I connected that to the ESD cable on my workbench to ground it. I also figured, since this is supposed to be chassis mounted, that the metal shield of the filter should also be grounded, so I clipped one of the side mounting holes to the ESD ground cable as well.

I then connected the input brown and blue wires to the output screws of the 24VAC transformer, which was plugged into a 120VAC wall socket. The output brown and blue wires of the filter I connected to the power input of my device (which can take up to 60VAC/DC and has a full-bridge rectifier plus step-down converter and LDOs to power the device at 5VDC and 3.3VDC).

I measured the voltage at the output of the filter (input to my device) and saw 12VAC across it. Before I could measure the voltage at the input to the filter (it should read 24VAC from the transformer), I noticed that the outlet/transformer had started smoking and immediately unplugged it.

What have I done wrong? Is this filter only usable on the high side?


texts: Why is the Digital 0 not 0V in computer systems?

texts:
I'm taking a computer system design course and my professor told us that in digital systems, the conventional voltages used to denote a digital 0 and a digital 1 have changed over the years.

Apparently, back in the 80s, 5 V was used as a 'high' and 1 V was used to denote a 'low'.
Nowadays, a 'high' is 0.75 V and a 'low' is around 0.23 V.
He added that in the near future, we may shift to a system where 0.4 V denotes a high, and 0.05 V, a low.

He argued that these values are getting smaller so that we can reduce our power consumption. If that's the case, why do we take the trouble to set the 'low' to any positive voltage at all? Why don't we just set it to the true 0 V (neutral from the power lines, I guess) voltage?


texts: Is it harmful to touch only one point in a 200V circuit

texts:
Consider an LED setup where several modules are connected in series so their forward voltages (~20V each) add up to something around 200V. The setup is driven by a Mean Well HLG-480-C2100 driver.
Now I wonder if touching any one point in this setup is dangerous or not (I know that there is only voltage between two points). My assumption is that touching e.g. only the positive terminal of the led driver is harmless. Same principle as why birds can sit on a power line.
One concern that I have is that the capacity of a human body is large enough to cause a reasonable current flow right at the moment of contact, but I don't know and I'm not going to try.
In case it matters: there is no continuity between the negative output of the driver (LED-) and protective earth.
My thought: if there was continuity between LED- and earth, then touching one point is in deed dangerous. Pretty much the same like touching one terminal of the mains, but with the difference that the residual-current device wouldn't protect you due ro the galvanic isolation from mains.


texts: How to compensate voltage drop on a wire

texts:
I'm using a 12v power supply with 12 meter cable ( 0.5mm ) to feed 4 small motors that use around 3A.

My problem is that when I turn all the motors the voltage goes to 7 volts. I need it t stay around 10-12V.

I need to use the power suplly away from the motors 6 to 12 meters.

Any solutions to avoid this voltage drop on the cable?


texts: Relay or Transistor for DC Resistive Load?

texts:
I'm building a circuit that includes a resistive load that I have to switch, which is going to be supplied with ~200 VDC and 0.1 Amps.

I've looked at different mechanical relays, and typically they are specified as "30A@240VAC or 30A@30VDC.".

Ideally, I would like to use one of these. Would they be safe to operate at 200 VDC, since I am using a drastically reduced current?

There is also a range of solid-state relays, but they are only specified at (for example) 250 VAC and 2 A, making no mention of maximal allowable VDC.

As an alternative to the relays (which I guess are generally targeted at AC applications), I suppose a power MOSFET might be usable?

Thank you for any assistance....


texts:
I have no clue what I'm doing but I want to prevent anything down the line of my car battery draining it, so I was thinking of somehow disconnecting everything down line while it is off. Pretty sure I finally kinda sorta maybe understand amps volts, ampere-hours, and how to power and use a relay switch receiver. What I know for sure I don't understand is what to actually disconnect the batter with. All I could find were things that you manually use at the battery to disconnect the negative terminal. The battery is 12 volts and outputs up to 810 amps.

Links:
https://www.amazon.com/TalentCell-Rechargeable-12000mAh-Multi-led-indicator/dp/B01M7Z9Z1N/ref=sr_1_3?dchild=1&keywords=12v%2Bpower%2Bbank&qid=1587279333&sr=8-3&th=1

https://www.amazon.com/Solidremote-12V-Universal-2-Channel-Transmitters/dp/B01JGDV8UM/ref=sr_1_2?dchild=1&keywords=Remote+Control+Relay+Switch+receiver&qid=1587280585&s=hi&sr=1-2

https://www.autozone.com/batteries-starting-and-charging/battery/duralast-platinum-battery-35-agm-group-size-35-650-cca/377104_258029_25698


texts: Automatic power switching between two DC sources with a switch to charging in the second position

texts:
I am designing a circuit which will automatically switch to be powered by a single 18650 when the other voltage source is disconnected. It will use a DPDT switch, the second position of which will shut off power to the Arduino from both sources and power a 5V charging module for the 18650.

I have scoured this site for info, and found an IC which I believe is perfect for the automatic power switch, an LTC4412 which drives a P channel MOSFET.

I have modified an example circuit found on the datasheet for my purpose, and have several questions:

As the MOSFET gate will be closed, will the IC have any affect on the circuit in position 1?
Can COUT be any capacitor, so long as it is rated for >5V?
Does any of this stand out as being terribly misinformed?

Many thanks.


texts: Can a cheap transformer be used for twice the rated voltage?

texts:
Can a step up transformer designed to step up from 110v to 220v be used to step up from 230v to 460v? (I'm thinking one of those cheap Chinese auto transformers from ebay, in the 1kva-2kva range)

I expect it will tolerate a small over voltage, such as 10% or 20%, but could it do double (or more), or will it overheat pretty much instantly?

The application is to step up single phase to input into a motor VFD to get the most out of it and drive a motor which can't be re-wired from Y to delta to run at 230v. I'm aware that this will only work with a single phase input VFD, or a three phase VFD de-rated appropriately.


texts:
I'm really trying to understand my voltage regulator (LM350T), but I think I'm still missing a few things. If I add cap C3 (I've tried 0.1uF and 10uF) to the output in the circuit below (note that the regulator should be LM350T), I get a rapid voltage rise (e.g. from 11V to 16.36V, or 6.4V to 9.8V), then a verrrry slow drop after that.

This shouldn't be right: the cap is not "part of" the regulator circuit in that it doesn't pass information between the adjust and out pins as far as I can see. The effect I describe should be in the capacitor itself across the plates, not in the regulator output. So I don't think it should have any effect. But it does.

Beyond that, it increases my minimum voltage out from ~1.25V to nearly 1.5V, and this doesn't appear to be discussed in the datasheet. I mean, I guess they don't have to include in the applications that the addition of an output cap will significantly change the minimum circuit voltage, but it seems like the TI sheet would have at least mentioned it, as it is very complete otherwise.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm playing with a BroadLink module with a MT7681 IC onboard and I have found this IC marked C55 in the path of the UART_RX line. Any ideas of what it may be? Counting from the dot pins are RX_OUT, 3V3, ?, RX_IN, GND, ?.

[UPDATE]

I'm not sure which one is the first pin. Today I think it could be the other way around, if the mark in the silkscreen shows the "head" and the first pin would be the one that's closer (the bottom left one on the pic).

I'v also followed the traces and this is what I found:

PIN 1 -> input
PIN 2 -> GND
PIN 3 -> GND via a 1k resistor
PIN 4 -> output
PIN 5 -> 3V3
PIN 6 -> LDO_RST_N in the MT7681 via a 100k resistor, cap to GND

LDO_RST_N is pulled low to reset the controller, so it's normally high.


texts: Sensor to measure small amounts of tension?

texts:
I would like to measure the a small amount of tension (less than a newton) in a line. I've found products that do this for much much larger amounts of tension. I've also seen "stretch sensors" but they don't seem to provide an easy way to convert "amount of stretch" measured in ohms to newtons.

I suppose I could buy a stretch sensor and a spring scale, come up with some kind of regression to convert inches to amount of stretch and then I can convert ohms to inches based on the data provided, but thats a good deal of work, and I'm also worried the stretch sensor can degrade over time.

Anyone have any good suggestions on how to sense small amounts of tension?

The device I'm building is designed to measure thrust output by a quadcopter propeller. I'm sure I could rig it to push down into a scale or something rather than pull, but I would much rather have a system where the prop creates tension in a line. That way I can also have the propeller free rotating and could potentially measure p-factor


texts:
I have some questions about using capacitors with an L7805CV

According to the datasheet, on page 4, it shows I need:

C1 = 0.33 uF
C0 = 0.1 uF

I bought a few sets some time ago with 'common' values and what I have (amongst others) are 100 nF ceramic capacitors.

Questions:

Can I use as C0 ceramic capacitors (since 0.1 uF = 100 nF) ?
Why are ceramic capacitors typically shown in nF and electrolytic in uF? (because of the range differences I assume)


texts:
I am using a 1.3' 128x64 OLED display bought from a site I don't remember(probably no-name), using the SSD1306 drivers, with an Arduino Nano. I have connected the SDA->A4, SCL->A5, as indicated by the datasheet, then booted up an Adafruit sketch included with the SSD1306 library.
After changing the I2C address to the corresponding one, I notice that only rows 2-8 inclusively are being changed/used. I have tried using the U8Glib library, as was advised on another post in this community, but to no avail, and now i have the incomplete "hello world" message(in Chinese as well) stuck on the display instead of the semi-blank white screen.
This is what it looks like now when trying to run the Adafruit sketch a second time. Any help is appreciated, as I cannot seem to find anything about this online. It does not seem to be broken, as the screen was mostly white at first run of Adafruit code, but after uploading U8Glib code, it was all black with the white text, alas still not aligned properly.
Edit: I am sorry for weird angle of filming, but the behavior can be seen either way


texts: Using photodiode to measure onset of screen refresh

texts:
Background:
I currently have an ATmega AVR microcontroller development board and hope to use it to measure the moment a screen changes from black to white to determine the time when a screen refresh occurred. This is in the hopes to accurately determine when someone sees something for EEG research. My ideal is to attach the dev board and breadboard to the back of a computer monitor and just have a photodiode attached to the corner of the display via cables. I purchased a bunch of OP950 side-view flat photodiodes (http://optekinc.com/datasheets/OP950.PDF) to lay flat against the screen.

Question:
My question is how do I properly use this photodiode? I read the spec sheet forward and back and researched how to use these, but I feel like I'm missing some crucial aspect to make sense of it all.

From what I've read so far:

I want it reversed biased for speed.
I need to determine the resistance based on it's reverse light current.
I might need an OP AMP to boost the signal (although I only really want a binary response of no light vs. light)

I know this is a pretty general question, but after looking through books, learning about semiconductors and photodiodes at a micro level I still don't know what exactly I'm looking at with the spec sheet.

In my attempt to solve this alone, I've come up with this:

The spec sheet lists 60V as the reverse breakdown voltage, which I want to stay away from since it would result in damaging the diode.
The spec sheet lists Reverse Dark current as 60nA Max, which is the current it always has when connected due to leakage.
The spec sheet lists Reverse Light current as 8μA-18μA, which is the range of current that is created by shining light on the photodiode when provided a 5V reverse voltage.
The resistor needs to come between the 5V pin on the arduino and the negative pin on the photodiode.
The resistor needs to account for the reverse light current and the 5V power supply.

I assume many of my assumptions are incorrect, and researching others' similar questions were too divergent to make sense of my component's spec sheet. Also, I would include a diagram, but I feel very uncertain how it would look and would prefer to think this out with better information from anyone who can help.

Thanks in advance for anyone's support!


texts: Understanding battery voltage detection circuit

texts:
I am looking for some battery voltage monitoring circuit and came across this one (I don't have reference now, will add once I get it.)

It uses complementary MOSFET pair DMC2400UV to enable the circuit and then one can read the voltage through voltage divider which lowers the voltage.
I don't understand how the resistor values are calculated in this circuit (all R1, R2, R3 & R4.) I have a Li-Po battery through which I want to measure the battery voltage. The battery voltage will  range from 4.2 - 2.7. The microcontroller connected operates on 3.3V and will be using a 12 bit ADC. I want to sense the voltage for a small time and turn off the MOSFET to reduce the current drain.
It is a battery operated device, so I want to keep current consumption to a minimum and extend its battery life.
Can you please help me in calculating the resistor values and whether this circuit will work for my case or not?


texts:
I'm a mechanical engineer who's recently gotten into electronics, and I'm a tad stuck with this new design I'm working on.

The idea is to have two separate batteries powering two separate lines, but if one battery were to cut out, the other would take up the supply of both loads. (Table in image with L A and L B being loads A, B).

The circuit I have now is using depletion MOSFETS for their normally open mode of operation. I've been having trouble finding good info on depletion MOSFETS, and have a feeling that my circuit isn't quite right. The resistors might not have to be there, and may actually have to pull to ground, but again, my understanding of depletion MOSFETS is shaky.

The idea behind the circuit is that when the battery is active (let's say B2), it turns off the normally open MOSFET, and supplies it's own power to load B. But if B1 is off, Q1 is open, so power can flow from B2 to Load A.

Another question I had was with grounding this circuit, I should just tie both negative terminals together, as well as the load lines's ground right?

Nominal conditions are 2S lipos or 9V batteries for power, with nominal loads of 200 ma, with possible 1-4 A spikes for ~ 2-20 ms every now and then (9V batteries themselves are able to handle those spikes very well).

Current parts are:
MOSFET - Digikey
Diode - 1N5817-TP

(MOSFET very subject to change, just one that I found in a TO-220 package with ~1A current capacity (800ma)).

Any help would be appreciated,
Thanks


texts: What rating of constant current LED driver do I need?

texts:
I've recently finished building some understairs cupboards.

I fitted a 9W LED light into the cupboard which comes on when the cupboard opens. It is driven from this LED driver.

I've measured the DC voltage on the output of the LED driver with the light on and it is showing as 27VDC.

Unfortunately, the shelves are really dark as you can see.

So I had the idea of fitting rigid LED strips into them.

I thought I could just buy 30VDC LED lights and they would work. I found the following strips on eBay.
Rigid LED lights

Unfortunately, the seller of these has said that the 30VDC capacity is only really for 'spikes' and they are more designed to run at 24VDC (for caravans etc).

I also looked for a 'beefier' LED driver and found this on Amazon.
1500mA LED Driver

It was then I read about the difference between "constant current" drivers and "constant voltage" drivers.

At this point I was completely lost so thought I would ask the experts for some advice and guidance.

I'm looking for help on what LED driver I would need to achieve this. I wondered if a "constant current" driver would just inject that current (1500mA) into it's output at all times and potentially damage the existing light and the new LEDs?

Also, whether 24VDC LEDs would be suitable?

Any help would be appreciated. Thanks.


texts: Determining whether piecewise function y[n] = {x[n] if n even, -x[n] if n odd} is time invariant

texts:
$$
y[n] =
\begin{cases}
 x[n], & \text{if }n\text{ is even} \\
-x[n], & \text{if }n\text{ is odd}
\end{cases}
$$

My usual way of solving time invariance problems is to do this:
$$y[n-m] =  x[n-m]$$

but I have no idea how to deal with the function splitting off into 2 cases.


texts: What parameter of this sensor necessary to decide about the required ADC resolution?

texts:
From the datasheet of this accelerometer, I need to decide about the adequate ADC resolution.

If my reasoning is not wrong the output noise floor of this accelerometer will decide the adequate ADC bit depth. So if the accelerometer output has 1mV noise floor then a 3.3V 10-bit ADC would not be adequate because 3.3V/1024= 3.2mV. On the other hand a 16-bit ADC would be an overkill.

Is my reasoning is correct? How can I refer find such parameter(noise floor) from the datasheet of this accelerometer and make a conclusion about the adequate ADC?

I also cant figure out the outputs' voltage ranges from the datasheet as well:(( Is it mentioned in the datasheet what output voltages corresponds to -3g and +3g?


texts: Relation between Output voltage and current in a transresistance amplifier

texts:
I need to show that for the above current to voltage converter,

  \$\frac{V_0}{i_s} = -R_1(1+\frac{R_3}{R_1}+\frac{R_3}{R_2})\$

assuming that the op-amp  is ideal,
Voltage at the negative input terminal =  \$V_n\$
Current through the negative input terminal  = \$i_n\$
Current through the positive input terminal  = \$i_p\$
Voltage at the positive input terminal =  \$V_p\$
\$V_p\$ = \$V_n = 0V\$
\$i_p = i_n = 0A\$
Using voltage divider rule,
\$V_1\$ = \$\frac{R_2}{R_2+R_3}V_0\$
\$i_s = \frac{0-V_1}{R_1}\$, So , using these two equations ,
\$\frac{V_0}{i_s} = -R_1(1+\frac{R3}{R2})\$
Why my answer is wrong ?

EDIT:
I think have figured out the error on my previous calculation . The voltage divider rule still works here like this.

Let, \$R_p\$ be equivalent for R1 and R2

\$R_p = \frac{R_1R_2}{R_1+R_2}\$
\$V_1 = \frac{R_p}{R_p+R_3}V_0\$
\$I_s = \frac{0-V_1}{R_1}\$
\$I_s = \frac{0-\frac{\frac{R_1R_2}{R_1+R_2}}{\frac{R_1R_2}{R_1+R_2}+R_3}V_0}{R_1}\$
After solving this the proof comes.Is there  any discrepancy in this?


texts: Can I connect a Bluetooth module without a microcontroller?

texts:
I am completely new to electrical engineering and was wondering whether or not I can connect a Bluetooth module to my phone without a microcontroller...

Is it possible to hook the module up to a power source and connect it directly to my phone without a microcontroller?

Thanks!


texts: How Replica Feedback bias circuit rejects supply noise?

texts:
I attached the circuit diagram along with a short description of its working principle. However, it's not clear how the circuit rejects supply noise. It will be great if someone can brief about what exactly happens when-

The supply voltage goes up
The supply voltage goes down.


texts: I am using LTspice as opposed to P-spice because I have a Mac. I've been asked to simulate a circuit using 1N914 and 1N4729 diodes, but LTspice doesn't have those diodes. What are equivalent diodes to the ones previously mentioned on LTspice?


texts:
So today I assembled a little circuit to test my new shift registers (74HC595).

I took three breadboards and connected them as  shown on the drawing here.

It is supposed to work as  a user controlled shift register with buttons for CLK, DS and LATCH. I was too lazy to write a program for it to work so decided to make a hybrid one.

After going through a TEST #1,  I encountered a problem. When I hit the button on clock, it can glitch and actually give me 2-3 clock pulses and read DS pin.

It was the first positive outcome in my experiment. I didn't even consider it in my primitive design.

So I reconsidered the design and thought that this could also happen due to the to many wires and loose connections.

So I rewired the project with less wires. Exactly as it is shown on diagram but with less jumpers.

At TEST #2, I realized that I have super powers. I have no idea what happened, but I didn't even need to press buttons anymore. All I had to do is put my hand above the circuit and it would live its own life. Th shift register would blink like crazy.

So after all my questions is:

Why did it happen ?

Wire electromagnetism caused an induction in a circuit that cause current the bad manufactured buttons ?


texts: LCD controller works with adapter but not with batteries

texts:
I started making a "case-top" as I like to call it. Raspberry pi 3-based laptop. Took an electrician's case emptied it and started putting the components in.

https://www.sparkfun.com/products/12711 connected to 4 18650 3400mah protected batteries which are in parallel, and each one has a TP-4056 JUST to avoid explosions. An XL6009 takes the power from the charger and drops it on the pi @ 5V, and another XL6009 takes the the power from the charger and drops it on the LCD CONTROLLER @ 12V.

The afformentioned board is similar to this http://www.ebay.com/itm/NJYTouch-M-NT68676-2A-HDMI-DVI-VGA-AUDIO-LCD-Controller-Board-for-LTN170X2-L0-/282420095187.

When I use the 12V 4A it requires instead of the batteries it works perfectly. Power, sound, light. The screen works like a treat. But when I try to power it from the batteries, one small LED on the button board flashes once and I get nothing. No power, no light, no nothing.

I know the XL6009 WORKS, because I did measure the out volts and i do get 12.1V constant on the plug, not on the board. So both the board and the cable/plug I have soldered have power.

What am I missing, (apart from a brain)?

 please notify me if it is not readable. Thank you

The batteries are these http://www.keeppower.com.cn/products_detail.php?id=375

and these are the step up modules http://www.gearbest.com/other-accessories/pp_227265.html


texts: How to program an ATMega328 using a Serial Port without using programmers such as USBasp

texts:
I am currently learning electronics. I recently bought an ATMega328 and an USBasp programmer to begin my learning. But I couldn't use the USBasp to program my chip. So I researched on other ways to program a AVR and I stumbled upon the idea of using a serial port to program it. I have a RS-232 port on my old desktop. I figured I could use it to program. But I couldn't figure how to do it. I have searched through the Internet. Some advise me to use a Max232 chip. I couldn't understand all of them. Below is a list of sites I have researched on this question:
Programming Atmega with serial port
http://www.hobbytronics.co.uk/arduino-atmega328-hardcore
I want to know how to program the chip. Answers are appreciated.


texts: Switching positive and negative voltage with npn transistor (or multiple npn transistors)

texts:
I need to switch negative and positive voltage with npn transistors, but I am not sure if npn transistors work in both ways.

How to do something like this with transistors?


texts: How do I figure out the equivalent resistance of a network of resistors on a microcontroller?

texts:
I am trying to figure out what the equivalent resistance would be at a certain point in a resistor network given different conditions of the GPIO pins they are connected to.

Configuration 1 is when the OUT pin on the micro is driven HIGH: In this case I know R1 and R3 are in parallel to one another, but I'm blanking on whether or not R2 would be a factor to the overall resistance seen for a device plugging into P.O.I? also blanking on what the voltage would be as seen on the IN pin.

Configuration 2 is when the OUT pin on the micro is driven LOW, this case I have the same questions as above with the added question of can we consider R2 and R3 as parallel resistors?


texts: How to properly open and close files "inside" a member function?

texts:
I am using Arduino Uno and the Ethernet Shield with a 2GB SD Card. I have the following working code intended to be used to write data on the SD Card (note: the SD Library is properly initialized and I just hide the reated code in order to keep things smaller):

class Logger {
  private:
    File myFile;
    char *myFilename;

  public:
    Logger (char *myFilename = "text.txt") : myFilename(myFilename) {
      myFile = SD.open(myFilename, FILE_WRITE);
    }

    void writeAction () {
      if (myFile) {
        myFile.print("Sample text.");
        myFile.close();
      } else {
        Serial.print("Error opening the file ");
      }
    }
};

void setup() {
  Logger logger;

  ...

  logger.writeAction();
}

However, if I change a bit the above code as made in the following one, it will not work as expected: the "Sample text." is not written / saved on the SD card.

class Logger {
  private:
    File myFile;
    char *myFilename;

  public:
    Logger (char *myFilename = "text.txt") : myFilename(myFilename) {
      // Note: Here is the change. File opening statements are moved
      // "inside" the writeAction function.
    }

    void writeAction () {
      myFile = SD.open(myFilename, FILE_WRITE);

      if (myFile) {
        myFile.print("Sample text.");
        myFile.close();
      } else {
        Serial.print("Error opening the file ");
      }
    }
};

void setup() {
  Logger logger;

  ...

  logger.writeAction();
}

Why does it happen? How can I make the myFile to be properly opened and closed "inside" the writeAction function?


texts: RS485 + Power over twisted pairs, still need isolation?

texts:
I need to communicate with a piece of hardware on an elevator car. I have a few twisted copper pairs available, but it's not CAT5, so Ethernet is out. Instead I'd like to use RS485.

I've been reading and ground level difference can really mess up 485, I'm also passing power along with the RS485. ( So 6 conductors: A,B,X,Y,5V and GND ). Since the unit in the elevator will draw power from the copper pairs is ground level difference still an issue? Do I need to go full out on the isolated 485 or is that overkill?

note1: These cables can be as long as twice the height of a building ~100-200FT

note2: Communication speed is not critical, it can go slow.

note3: LDO takes 5V to board 3.3v so we have some room for voltage drop on wire.


texts: MAX 6675 module not working shows 0 degrees celsious 0 fahrenheit

texts:
This isn't a problem, rather a solution. I have a MAX 6675 module connected to an stm32 development board which at the beggining it worked perfectly and suddenly, it just showed 0C and 32F. Always those values.

Then to try in a different board and program, I've used an arduino UNO and the adafruit libraries for this module. The same results.

Wandered around the internet with many people who was with the same problem, but no responses.

Suddenly tried to solder all. Stop using dupont cables. And it worked again. So, this is for all the people who are in the same situation, use the solder!!

I'll be posting this on reddit to


texts: sampling rate and bit resolution for Scanning Probe Microscopy

texts:
I am trying to compare two products and see which one offers higher performance in terms of sampling rate and bit resolution.

Below are the specs I was able to gather from product1  and product 2. (I am not sure if I am looking at the relevant specs though.)

Product 1:
Input: ADC @ 400 kS/s, 18 bit
2 HF ADC inputs @ 50 MS/s, 16 bit
Output: DAC outputs @ 200 kS/s, 16 bit

Product 2:
Input: 20-bit @ 60 kS/s, 22-bit @ 1 kS/s (oversampling)
Output: 20-bit, 1-ppm precision, 1 MS/s

I think it's true that higher resolution in bits is going to result in better performance. However, it seems product 1 has a higher sampling rate.

Could someone tell me which product will result in finer resolution in both input and output and why?


texts:
I am making a water fountain feature and want to install a changing colour display that is variable in a laminar water jet.  The unit has to be stand alone and start when the power is applied.  The fountain is in the middle of a dam and is connected by a utility supply.  Will the BlinkM MaxM do. I am able to do basic electronics and was hoping that this unit is suitable for the job.  I am attaching acrylic rod to the LEDs as a light transmitter and this is insert into the water stream. I need bright LEDs. Can you recommend the electronics required for the job.

Doug


texts: Is it necessary to opto-isolate a darlington array output?

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I've got the following circuit going:

A Vishay opto-isolator (CNY74-4) that takes input from buttons that work on 24V, and outputs to microcontroller pins (an Olimex ESP32-PoE-ISO in my case).

A ULN2803 darlington array connected to the microcontroller, +24V and GND, driving LEDs.

Initially I had designed the circuit so that the 24V of the buttons had its own separated GND. But to use the ULN2803, I need to connect the GND of the microcontroller to the GND of the 24V power supply, or it won't work.

This entire setup works perfectly, but I'm wondering if I should also put an opto-isolator between the microcontroller and the ULN2803. It might be overkill, but then the 24V power supply is completely separated electrically from the microcontroller.

I discovered the Vishay ILQ30, an opto-isolator with darlington output. It could take care of this in one DIP. Or the Toshiba TLP627-4, that one is in my KiCad library :)


texts: Limiting the pulse width of a PWM by using voltage divider and a single power supply

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I'm using a Tl494 PWM and I want to limit the pulse width from 0% to 80% of the signal as maximum. How can I achieve this using a SINGLE 5v reference supply (I know it can be achieved  by using two supplies) and a voltage divider?
I tried many combinations of potentiometer and resistor and I end up getting a pulse width out of this limit, that is, the duty ratio always is allowed to exceed the  80% limit. I want to prohibit the possibility of the device user exceeding that limit.

Thanks very much in advance!


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I am given the following circuit:

Thanks for any help.


texts: How to route at non-45° angles in KiCAD?

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Is there any way to route a track in KiCad 4.0 at a non-45° angle? I've searched for half an hour now and all I could find was this bug which mentions a "routing options" menu that I can't find, and a "Free angle mode" inside that which I can't find any mention of either.

All I want to do is draw a track between any two points on the grid without the 45° bend in the middle, but I just can't seem to figure it out.


texts: What can I use to increase efficiency of inductive wireless energy transfer instead of factory manufactured ferrite plates?

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The Context
I am a hobbyist with no education in electrical engineering. I am working on a DIY project trying to make water resistant rechargeable bicycle lights. I am doing this as a hobby for fun and learning so it doesn't need to be commercially viable or to pay off. The device will be cast in silicone and will be completely covered so it needs wireless charging. Because of the size of it I cannot use any coils or wireless charging solutions I can buy, so I am attempting to make my own. As far I have come up with etching the charging coils in layers on copper foil that seems to work for me surprisingly well(as far at least):

The Problem
I understand I could improve the energy transfer by having many layers close to each other and the right AC frequency and I am trying to improve there, but as I understand having ferrite plates beneath the coils could improve things dramatically. Unfortunately the plates need to be very specific size and shape for my project and it is not practical to buy or order them. I am looking for a way to make something similar at home. My main question is: what are my options, if they exist at all? In this context it doesn't need to be perfect, it needs to be better than nothing.
Research as far and ideas
I have looked into making ferrite at home and found this: Make Your Own Ferrite to Improve Magnetic Fields, however on further reading about making ferrite I got the impression that crystals of iron oxides and a small amounts of some other metal need to be formed so I started to doubt that this really works without high pressure and temperature. Could someone confirm if this DIY method really works or is this nonsense?
I also have an idea to buy ferrite beads, crush them into powder and then cast my needed forms from that using some adhesive like silicone or PVA glue. Would that work?
Are there any other options?


texts: Resistor or no resistor between this IC and the pmos GATE?

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I'm using this IC (https://www2.mouser.com/datasheet/2/609/ADM1270-878589.pdf).

This IC controls the GATE of a pmos. I'm thinking about using this MOSFET (https://www2.mouser.com/datasheet/2/389/sts10p4llf6-956791.pdf).

The GATE pin on the IC has a typical current value of 25uA.
MOSFET gate has a fair amount of charge (Total gate charge = 34nC) and it has Input capacitance (Ciss)= 3525 pF.

Do I need to use a Resistor to limit the current out of the pin? How do i proceed?


texts: Second order transfer function with second order numerator?

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I was wondering if this is even possible.
For example, if the standard form of a transfer function is

is it still possible to have:

I've only ever seen this done in one place where they said this had  to be the equation for a high pass filter, but every other place I've seen has said the standard form should have less of an order in the numerator.
Would this even be correct, and would it have to be a high pass filter or could it also possibly be a low pass filter?


texts: Practical Implementation of Smith predictor

texts: I am now dealing with Smith predictor and I understand that it's based on model of the controlled plant. This model I can get by some identification method, but such a model will never be absolutely precise. Thus I have following question: How can I provide, that my model won't diverge with the reality? Would it be possible to use some "corrective" term based on comparison between actual plant output and estimated plant output? Thanks for any ideas.