texts:
I'm trying to develop a board that includes I2C and SPI devices that are unpowered for the majority of the time to save power. I found that for these particular devices (Honeywell HSC pressure sensors) you definitely can't have the I2C ones unpowered because you end up sort-of powering them through the I2C lines and getting a weird voltage of around 1V.

However, I have unpowered SPI microsd cards on the same bus as some other things (a RTC etc.) and it seems to work fine.

Both devices say that the peak voltage on any line is something like Vdd+0.3V, which if Vdd is 0V is 0.3V (e.g. for microsd). So my questions are:

Do they really mean Vdd+0.3V even if Vdd is 0V?
Is there any nice way to do this? I've found an I2C buffer chip (PCA9515) but it draws 3 mA all the time which isn't ideal - I'd have to turn that chip off too, which I'm not sure it will like. For SPI I found this 74LCX125 chip, which seems to sip power as long as the inputs are not floating, so very weak pull-downs might help there. It all seems a bit complicated though.

Any suggestions?


texts: If I filter the output of a rectifier using an LC circuit on the output, the input source would have a current draw with a square wave shape. I know that a lot of commercial transformers like sinusoids. Is this considered bad power factor since square wave are kind of out of phase with sinusoids or are the two unrelated.


texts: How I can resolve the problem of conversion (to_integer(unsigned(variable))

texts:
I want to solve a problem in VHDL with Quartus II.

I made a model of VGA protocol 640/480. When I made the part of displaying
I made one two signal in integer.

  Error (10621): VHDL Use Clause error at dispGest.vhd(28): more than
  one Use Clause imports a declaration of simple name "unsigned" -- none
  of the declarations are directly visible

How can I resolve this problem?


texts: Choosing an input signal based on whether a driver signal is floating

texts:
I have three inputs: an analog microphone signal (M+), a push-to-talk (PTT) signal, and a ground (G). The PTT signal is connected to G when the button is depressed and M+ should be carried, and is floating when not connected. M+ is always live and referenced to G.
I want two outputs, namely the microphone and ground, with the PTT behaving as expected. I believe what I therefore want is something along the line of the following setup:

Output ground connected to G
Output microphone as the output of an analog SPDT multiplexer (e.g. the Maxim DG419DJ); the two signal inputs being M+ and G.

However, I'm not sure how to drive the multiplexer. PTT is either the same as G, or floating compared to G, but multiplexers seem to expect (sensibly, I admit) a voltage difference in their driver inputs.
I am, as you may well have guessed, not particularly au fait with electronics, so my question is essentially--how can I make this work? Is an analog multiplexer even the thing I'm looking for?


texts: Can stepper motor drivers switch quickly between full and micro stepping?

texts:
I am trying to turn something with a stepper motor very quickly, but have it end up in a very precise spot. I would like to use full stepping to get a lot of torque so it can accelerate quickly, and when it gets close to where it needs to be, switch to microstepping so I can position it precisely.

What type of driver should I look into for this? How quickly can I switch between full and microstepping? Do I need to bring the motor to a complete stop before I switch?


texts:
I've been wanting to start a project with the following requirements:

Be able to display a static image, composed of 19x19 RGB pixels (though I expect to have to use a 20x20 matrix).
Be small (in the region of 3-20cm along one side)
Ideally include wifi support to read data from a simple web service.

However I don't really know where to begin.  For a start I don't know where to source a 20X20 matrix (discrete LED matrix is fine), or if it would be better to use 4x 10x10 matrices and controllers (then I'm not sure how these could be used together.

I've been tentatively looking at Arduino, but also rasberry PI.

Could someone point me in a sensible direction as far as Platform, Matrix controller, or Matrix are converned? Thanks!


texts: Will this 3v3 level shift for arduino->avr programmer work

texts:
I'm trying to program an avr in a circuit that has other components on the same SPI lines that would be damaged with > 3.3 volt logic.

I figured I could just use an arduino (5v logic) with a level shifter I have laying around.

Does this circuit look like it could work? I wasn't sure how to deal with MISO.

I added leds on the MOSI and CS/Reset lines for added dazzle.

Updated schematic


texts:
I have been making a project involving a relay and an esp8266. Essentially a WiFi enabled relay. The issue that I have been having is that when the esp8266 boots it flashes all of its GPIO pins high and low a few times in quick succession. This of course has adverse effects on the device I have attached to the relay. Currently I have been trying to use a filter type circuit that I have designed using a capacitor and some transistors however I have discovered that this will work for some relays but I have to adjust resistance values and the like in order to get it to work for each different relay due to inconsistencies in their construction.

Here is what i have been using currently with approximate resistor values:

simulate this circuit – Schematic created using CircuitLab

Essentially what this circuit does is it prevents the relay from operating before the 470uf capacitor is charged. During startup the 7.5kohm resistor is trying to charge the capacitor (It takes about a second for it to charge to a usable level) but the filter line is unstable so it keeps being discharged. Only once the esp has finished booting and all the pins are stable can it charge and allow the relay to operate.

You might also notice that while fine tuning the circuit it is quite easy to adjust the resistor values so that things like the voltage regulator running the circuit start to get quite hot.

Essentially I am looking for a more reliable (less overheat-able) and all in all more elegant solution to this problem than I have already been using. I have considered adding an atTiny to the circuit to enable the relay due to the fact that its pins seem to be stable during startup but I figure there must be a simpler solution than having to add a whole other IC to my project!

Thanks


texts: Powering off a switching regulator causes MOSFET to briefly blip on. Arduino

texts:
I have stumbled upon a weird issue in my circuit below, that only happens when the DPDT slide switch, S1, goes from an upwards position(On) to the downwards position(Off). The issue is that when you turn off the switching regulator, U2, with the switch, it occasionally will briefly blip the MOSFET Q2 which is connected to a starter motor; the blip is so quick that the motor doesn't spin, but you can hear it. It seems to happen if you slide the switch past a certain point and speed.

After it happens once it doesn't happen again unless you turn the switch back on and repeat the sequence and hit that sweet spot where it does it again. You cannot get it to happen 100% every time but it isn't the hardest thing to try to trigger it again by playing with the switch.

In normal operation Q1 which is a pre-biased NPN (4.7K series base resistor, 4.7K base-emitter pull-down resistor), pulls the MOSFET gate low to turn On and Off the starter motor. I already ruled out that code is not the issue by removing all code that sets digitalWrite.

Is this a case of contact bounce or some sort of quasi-boot/reset mode where the ATMega328P-AU pin A1 is putting a little bit of current on Q1s base causing the MOSFET to briefly blip on? Some sort of weird tri-state I've never seen before.

What would be a good way to solve this problem?


texts: LTSpice transistor output capacitor not decoupling DC

texts: The circuit below shows a Darlington pair that is used to amplify an AM signal picked up by an LC tank.  As you can see in the input and output waveforms below, the signal is amplified but not decoupled from DC, despite using a 1u capacitor on the transistor output.  Why is this the case?


texts: How do I know the polarity of pins on a DC 2.1mm power connector using the schematic

texts:
So, I'm designing a PCB for a project I've been working on recently. I want to include a 2.1mm DC power jack, to power the components (LED strips in this case) I have found a suitable connector:
Kobiconn 163-179PH-EX
https://www.mouser.co.uk/ProductDetail/Kobiconn/163-179PH-EX?qs=Xb8IjHhkxj5l2UOaIqcGCw==?

Here is a recreation of what I see in EAGLE:

simulate this circuit – Schematic created using CircuitLab

However, using this and the other information in the library, I am unable to work out which wire is the live, and which one is the neutral, which I will connect to ground of my Raspberry Pi 3B

Here is a link to the EAGLE library containing the part:
 https://1drv.ms/u/s!Alkpzq1-4_ESg6oWE3KvkgNWk3Dg6w

Any suggestions?


texts: Unknown "2X" and "3X" markings on package outline

texts: I was checking the dimensions of a TO-263 transistor on its datasheet (page 8), when I saw something I could not understand. What do markings "2X" (over dimensions e and b) and "3X" (over dimension b2) mean?


texts: Why is my gate driver simulations are taking very long?

texts:
I want to turn on and turn off two mosfets from the asymmetric H bridge which is connected to SR motor at the same time.

I'm using IR2183 gate driver. The circuit connections from LTspice are show in the image. Why is my simulation taking very long? Is some thing wrong in my circuit?


texts: 555 timer based PWM fan controller does not PWM

texts:
So I've made a PWM fan controller based on 555 timer, but it does not acturally modulate any pulses, the output is exactly the same as the input so the fan works but does not react to changes in pot resistance.

The output of 555 timer does not have any pulses either, just a plain 11v DC signal, exactly the same as the input power.

Where should I dig?

Schematics:


texts: Am I supposed to ground the inverter or the battery? Or both? To vehicle chassis

texts:
I am setting up a solar system in a vehicle. I have 400W solar panels, a 12V battery bank, and a 2000W inverter. I've looked at the manuals and read online to figure out the wiring diagram below.

However I'm still not sure if I can ground the inverter and the battery separately (this would be convenient since they are 10 feet away from each other).

Or if I need to connect them to each other and ground just one device, which am I supposed to ground, the battery or the inverter?

Feel free to point out any other problems with my diagram, I'm just here so I don't set myself on fire.


texts: LTE Cat M1 vs NB-IoT : Building penetration

texts:
I browsed a lot search engines results to find any information (at "noob" level) about building penetration of these technologies.

For my IoT project, I'm now using LTE Cat.4 as I didn't know before about Cat M1 and NB-IoT. I'm facing a lot of issues because my systems are often installed underground (building basements). Since I don't need Cat.4 UL/DL speeds, I'm looking for better alternatives.

How better is the waves building penetration compared to LTE Cat.4 for LTE Cat M1 and NB-IoT + Cat M1 compared to NB-IoT ? From my searches on Internet, I know NB-IoT will be the best but the very low UL/DL speeds and the high latency may be a problem. Although I don't use applications with strict real-time needs, I should be able to synchronize the user data under (a few KB) under a reasonable delay as well to perform updates of some packages (< 1MB).


texts: Electronic Temperature Control Sound Light Alarm DIY Kit - how does it work

texts:
I bought a DIY Kit off ebay (the board says www.icstation.com ICSK061A), and lo an behold, it does not work. I could not figure out what the trouble was, so i simulated it in LTSpice, but i got no nearer to a solution.

What happens if I apply the lowest acecptable Voltage (3V) is that Q1 gets really hot. Nothing else happens, not matter what happens at Rt.
In LTSpice, I had problems determining how to simulate the LS (which actually is a beeper), so i left it out, which might be a problem...
I figured the 'on' state of the LED would require Q3 to switch on, so i played with the resistances of the components i used for Rt and Rp, but while i managed to simulate the Q1=hot case (power disspiation in Q1 >500mW), i never got Q3 to budge.
Would anybody be so kind as to advise whether the circuit is at fault, or if i just messed up the soldering, and simulating?
(btw: the Rp that was included in the kit is a 1k Pot, not a 10k as listed.)
Here's a recreation of the LTSpice model (couldn't figure out how to attach LTSpice files):

simulate this circuit – Schematic created using CircuitLab


texts: What is this program called and where can I learn about it?

texts:
I've seen a video of someone who created an intelligent waste bin. It could catch objects you threw at it by observing thrown objects with Kinect and driving at the location of impact (YouTube).

He used a program to design the circuits to control the bin, but I couldn't find out what it is. I hope someone here knows it. Here are some screenshots from the video (sorry about the quality, the video is 360p):

These might be from an other application, I'm not sure:


texts:
Given the following square wave signal g(t) :

I'm trying to find the \$R(\tau)\$ of this signal, but I'm confused about how to solve the integral.
In the signal above, the red square wave is the shifted signal \$g(t-\tau)\$. I understand the autocorrelation function will be periodic because g(t) is periodic, and will be a triangular waveform.

$$
R(\tau) = \int_{-T/2}^{T/2}g(t)g(t-\tau)dt
$$

Trying to find the first integral for \$\tau < T/2\$ (first picture) I have:
$$
R_1(\tau) = \int_{-T/4}^{-T/4+\tau} -dt + \int_{-T/4+\tau}^{T/4} dt + \int_{T/4}^{T/4+\tau} -dt + \int_{T/4+\tau}^{3T/4}dt = (-\tau) + (T/2 - \tau) + (-\tau) + (T/2 - \tau) = T - 4\tau
$$

For \$T/2 < \tau < T\$ I would have the inverse I suppose since it must be symetric.

I'm confused on the first integral. I'm not exactly sure I'm correct. I think I must calculate both integrals (in the picture) on one period i.e. so that the combined integral interval for \$R_1(\tau)\$ is on one period. Or is it on a half period? In which case \$R_1(\tau)\$ would be \$ R_1(\tau) = T/2 - 2\tau\$. The fact the signal is periodic is what is confusing me. I want ultimately to get one period of \$R(\tau)\$. So my question simply is: is the expression I got for \$R_{1}(\tau)\$ correct or not?

Any help will be greatly appreciated.


texts: I saw this video on Vimeo http://vimeo.com/23507315 and am amazed. Does anyone know how this works? Dies it send a pulse or switch ground? What is the wheel he is turning? What is that big gray thing at the top of the screen? Why dies he seem to have to hold the wire at the bottom of the screen?


texts: Why do we not care about matching the input impedance of non-RF amplifiers?

texts:
Talking about BJT topologies: A common base amplifier is always given as an example of an amplifier with very similar characteristics to the CE amplifier but with the low input impedance.

simulate this circuit – Schematic created using CircuitLab

It is said that the CB amplifier is commonly used in RF amplifiers in order to match the impedance of the wire carrying the RF signal. With "perfect" matching, we get 50% signal voltage transfer and 100% power transfer due to the seamless(?) edge between the RF cable and the amplifier creating no reflection. Correct me if this is wrong.

My question:

Why do we not care about this with other types of amplifiers? I.e., all of other frequency ranges in the spectrum. But for specificity, say the audio range. We always want the highest input impedance for the amplifier in order not to load the signal. Why does the signal not reflect due to the change in impedance?

I guess what I'm really asking is:

What causes the reflection? Why doesn't it occur with other frequencies? (if it doesn't)


texts: Analysis of transmission lines and waveguides

texts:
While reading the transmission lines in electromagnetic field theory , I observed that while analyzing different transmission lines like co-axial cable, and two wire lines, we are using the electric circuit model where we take the circuit as a distributed network, but while analyzing the wave-guide we are mainly focused on the electric and magnetic field lines.

Why do we analyze the  two structures differently? One using circuit theory model and another using electromagnetic theory?


texts: Powering two 3-LED lamps with battery/Battery pack - Multiple questions

texts:
I have seen many questions along these lines but I don't think any is an exact match (if that's incorrect, please just point me to the right match, that would be great and save everyone some time). Apologies in advance for missing or incomplete information, I'll be happy to update with anything that is needed for a complete answer.

I've bought automotive "side rear clearance" lights to use in a Halloween costume. According to the Amazon description (https://www.amazon.com/gp/product/B01MEG40NI/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1) they're "3-LED" but I was not able to find any other data sheet information. I know nothing beyond 20-years-ago high school physics about electricity.

I want to run two of these red 3-LED lights from battery power, for as long as possible on Halloween night, without catching my battery/battery pack on fire, or constantly changing batteries.

Answers to similar questions seem to presuppose that I know or can find out the amount of current that these lights "want" to draw. Do I in fact need to know that, and absent information from the manufacturer, how could I find it out or estimate it?

Without knowing the current these lights want, I want to figure out how to power these lights with alkaline batteries - I have 9V and AA handy. I'd like a run time of say 5+ hours.

I notice that I can't seem to power off of 1 or 2 AA batteries in series, but can off of 3 or more in series. Is that of any help (other than knowing I will need say 4AA worth (=~6V) (or more) voltage)?

I expect the wires connecting the lights to the battery/pack will be longish - about 4 feet. Is that length of wire going to bring its own considerations like extra resistance due to the length of wire? How can I judge ahead of time whether the wiring or battery/pack will get dangerously hot?

I have a lot to learn, and appreciate your patience - like I said I'm happy to clarify as needed or seek out resources on my own. Would greatly appreciate any guidance, information, answers, etc. Thanks!

Edit: Here's the opened unit. The black box in the lower right is labeled R1 and written on it is "221". I don't see what I think of as LEDs, but these square dealies across the center are labled LD2 and LD3 (middle and right, the left I might have obliterated the label).


texts: I need 2 power supplies for a low power project, a battery and a 5v USB. I need one of them to power the circuit at a time. 2 diodes circuit (right) seems work, but Q1, will there be a leakage from lower voltage to the circuit when 5v is presented? Other than that worry, that simple circuit only draws power from higher voltage, which something is not desirable, although it's fine for my case, but I want more control. Q2, is my left circuit a better choice? Somehow I think it's problematic.


texts: Obtaining 4-4.2V rail from 5V output of LM7805 voltage regulator

texts:
I'm creating a numitron clock with 4xIV-9 tubes (seven-segment filament displays) and have decided to illuminate them using shift registers controlled by an arduino. Each segment takes a voltage of 4-4.2V and around 17-20mA of current.

My voltage I have available is a 5V output voltage from an LM7805 voltage regulator IC. I need to power 4 high current shift registers (TPIC6B595), each with an expected maximum output current of 200mA. Owing to this, the 4-4.2V rail needs to be able to handle a maximum current draw of around 800mA.
I was considering using a simple potential divider however calculated that the required power losses greatly exceed that of the standard resistors that I have available.
I was also considering using a diode to drop the voltage however the forward voltage is a function of the current; therefore as the current can vary from the extremes of 0mA to 800mA I did not think a diode would be appropriate.

Any suggestions on how to obtain 4-4.2ish V rail would be much appreciated.
Many thanks.


texts: How to get impulse response plot of RLC cicuits

texts:
I want to plot impulse response of different RLC circuit.
Which software is easy and situated for it? as i am a starter.


texts: What's necessary to properly decouple/filter a PWM-controlled fan from an Arduino?

texts:
I've got a small problem I could use some help with. I am using an Arduino to control a cooling system I am building for a DSLR. Primary goals are to use PWM and some pots to control TEC power, as well as fan power. There will likely be two TECs and two fans, both attached to a long 98mmx40mm heatsink. Another goal is to keep the whole cooler unit as simple as possible, so I would like to use a single power connection, and preferably a standard connection (i.e. 5.5mmx2.5mm power jack if at all possible) that is frequently used with astrophotography gear.

The problem is that if I power the fans off the same +12V as the Arduino, could the fans inject a lot of noise onto the power lines? I have done some electronics tinkering, but I've rarely used motors, so I don't know a lot.

I do know that I need a diode (I plan to use Schottky diodes, since the fans will be controlled via PWM) across the positive an negative leads to the fans in order to avoid voltage spikes when power to the fans is cut off.

I also have read that a small capacitor parallel to the diode and fan can also be used to filter the noise a bit. It sounds like the capacitor should be QUITE small...anywhere from 100pF to 10nF? I don't know if there is an easy way to determine what size capacitor should be used. I am also not sure if a simple small capacitor like that would be sufficient to filter the noise generated by the fans, especially when using an Arduino.

I know that an opto-isolator (or opto-coupler) could be used instead of a MOSFET with the PWM signal to totally isolate the fan power circuit from the Arduino. I believe that would require using a totally independent power connection for the fans, though. That goes against my design goals of standardized simplicity. So, I am wondering if there is another way to isolate the fans from the Arduino enough that an opto-isolator would work well enough. If that is not possible, would using an LC or LRC filter on the fans be enough to filter out the noise and protect the Arduino?

Thanks!


texts: Rearranging transfer function for Bode diagram

texts:
Hi, I have been given this circuit and need to find its transfer function for then realizing its Bode diagram.
The problem is that I don't know how to arrange the terms to find the asymptotes of the diagram.
After some calculations I found : \$\frac{j\omega*R3*(R1+R2)Ca - \omega^2*R1R2R3CaCb}{j\omega*R1*(R2Cb+R3Ca) + R1 - \omega^2*R1R2R3CaCb}\$

I don't know if I am correct about this equation and even if I am I don't know how to find the cutoff frequencies of this transfer function can anybody help me please ?


texts: Switch ON with PushButton, Switch off with GPIO

texts:
I am looking for a schematic which is capable to switch ON a power Supply to supply a micrcontroller. Then switch off the power supply with a GPIO of this microcontroller.

I have found a lot of schematic on internet. But I have some constraints like (Power supply 0,8v to 1,8V and ultra low power <2uA and load = 200mA)

Another things, if I press the push button a second time, it does not shutdown the power supply.

Edit: The goal is to use a AAA battery (1.2V), but I need 3.3V for microcontroller. So I will use a Boost (30uA without load...). I want to be able to cut OFF power Supply.

I hope found a solution with you !
Sani300


texts: Will this ADC be able to drive the GPIO inputs of my Jetson Nano?

texts:
The Jetson nano Dev Board uses a voltage level translator on the GPIO (TXB0108) to convert from 3v3 to 1v8. (As given in the reference document.) I would like to drive this ADC, the AD7091R-4, to measure some analog voltages over SPI.
Now I've read that the JN devboard GPIO inputs need a rather strong pull-up to work. I've tested and verified that, to pull up a button it needs a 1.5k pull up or stronger.
The datasheet of the ADC states that the logic outputs lose .2 to .4 volt (depending on source or sink) when driving something with 200uA. (page 3)
This corresponds to a 16.5k load resistor at 3v3.
Does this mean that it won't be able to drive the logic inputs of the Jetson Nano dev board? If not, what schematic would I need if I want to make this work? (Add FET's to make it stronger?)
For reference, the simplified schematic of the voltage translator looks like this according to NVIDIA:


texts: 7-bit data mode in bluetooth module rn-42

texts:
I have bluetooth module rn42
I need to configure it to 7-bit data mode. Data sheets says that I should use command S7,1 to enable 7-bit data mode, but it does not work.
I receive ERR when sending s7,1 or s7,0.
Also, i noticed that command SB,1 also returns ERR.

Module lists all available commands when you send him "H" command, and in my case commands S7, and SB, are not in the list…
Maybe anybody has some more info about this strange case. I really need to make it work with 7 bit data mode.
Firmware version is 6.15
Other commands works fine.
Thanks for answers.


texts:
For a sensor device such as a positioner, do they sense 4-20 mA from two wires and supply from another two wires, or is this done with only two wires?
If only two wire, how can I do this?


texts: what is the equivalent circuit for battery in charging process?

texts:
OK I know a little bit about battery discharging process that is, I know that the open circuit voltage of battery decreases as SOC goes down, and the voltage is less than the Voc when connected to a load (so we have an internal resistance which rises as the battery gets emptied) I also searched and found more complex equivalent circuits (considering diffusion voltages). but these all model a battery acting as a source but How does a battery behave (in terms of circuit elements) in charging process (as a load) and what is it's voltage? I mean is it the open circuit voltage (disconnected from charger) or the charging voltage?
I'm asking because I'm a bit confused about solar charge controllers. as we all know they are not voltage sources and behave somehow like current source so if we connect a battery directly to a solar panel (like Self-regulating PV systems) how can we determine the operating point of the system?
Thanks


texts:
I'm a new hobbyist, I need a tip 121 transistor and a 2N4148 diode. I'm using the site taydaelectronics.com. This site doesn't have these items. A friend tells me that there parts can probably be substituted for others. Can someone help me figure out what parts I can use in their place?

Tip 121

2N4148 diode

Thank you

edit:

Here is the schematic I'm working from.


texts: Need help finding smallest possible 8 digit 7 Segment LCD TN Display

texts:
I can find a number of LCD TN 8 digit 7 segment displays but they are far to big. The kind of size I'm looking for is the ones you usually find in mini calculators.

The size im looking for is around 10mm by 50mm. The smaller the better really. The other specs of the LCD are not really important at this time other than getting the smallest possible. Maybe I'm wrong in my search for an TN LCD?

Any help is greatly appreciated.

Thanks

Scott


texts:
These are two resistors that were in series with a transformer on the mains (120 V AC) input of an audio amplifier power supply. The PCB under them has become discolored with heat after being in service for 22 years. I removed them from the board and measured them. Surprisingly, they are both 2.81 kΩ, but the color bands would suggest 10 kΩ ±10%.
I am surprised that they measure much less than expected. Further, I wouldn't expect the measured resistance to be so similar to each other if indeed they have failed over time (2.815 k and 2.813 k).
Either I have interpreted the color band incorrectly, or they have managed to degrade very similarly to an out-of-spec resistance.
They measure 11 x 5 mm which I think may be rated for 1 W but I am not sure. The color bands are faded.
What value would seem reasonable for these resistors? I don't know what purpose they serve in a linear power supply where they are between fuse and transformer (current-limiting? soft start?).
Here is a partial schematic. There is a TRIAC and opto-isolator after the resistors in question (R1, R2).

simulate this circuit – Schematic created using CircuitLab
And here is a picture of the resistors:

Edit:
I updated the schematic after one of the answers indicated that I had not sufficiently probed the board to see that the TRIAC is in parallel with the resistors.


texts: How to interpret this drawing (diode circuit)?

texts:
I need help how to interpret this drawing of a diode circuit.

I don't understand the voltage \$V\$ after the resistor.
Does it mean that \$V\$ is a voltage source connected to the ground (right picture)?

And is \$I=\frac{3V-V}{10k\Omega}\$ or \$I=\frac{3V}{10k\Omega}\$  ?

Thanks!


texts: Are there better alternatives for these buffers?

texts:
I'm building a circuit that extract the DC component of an input signal, ,divide the DC component by 5, and finally add 2.5V it.

Here is the schematic of the circuit (the last op-amp is to invert the inverted signal):

As you can see, I've added a voltage-follower buffer between the low-pass filter and the voltage-divider sub-circuit, and another similar buffer between the voltage-divider sub-circuit and the rest of the circuit. Without those buffers, the result would be wrong.

I want to build the circuit on a breadboard using LM741 chip as op-amp. So, I was wondering if there another way to implement those buffers that uses less physical space on the breadboard?


texts:
Source
I am trying to simulate this circuit before setting it up on breadboard.
I have downloaded this model for simulation.
And set up the circuit.

After transient simulation what I get from vout:

What am I missing here? I was expecting an amplified sinus wave. Is this because there is no load at the end of capacitor? If so how should I simulate it properly to see it before actually setting up the circuit? Thanks in advance.


texts:
I am trying to measure distance using LVDT sensor and AD698 IC. I don't have data relating the sensor I am using. I am simply tried to copy the distance measurement with device I already have. I matched the AC input and output of my system with the device that I already have. My input AC excitation is 5 Vp-p and 17 KHz. The output is alright. But I am facing problem in my DC output. The LVDT sensor that I am using is Half bridge type. I found this out after repeatedly checking sensor terminals. Circuit I used is exact one in page 6 of AD698 datasheet. http://www.analog.com/media/en/technical-documentation/data-sheets/AD698.pdf

My DC supply is +/- 15 V. I want my voltage to swing from 0 - 5 V centered at 2.5 V. I tried varying resistors R1, R2 and R3. For this I put variable resistor in place of feedback resistor R2 and offset resistor R3 and AC voltage R1. Adjusting feedback resistor R2 increased/decreased offset voltage but also changed voltage swing accordingly. I managed to get 5 V swing but offset voltage is very high (~10.8 V, voltage swing 13.5 - 8.3 v). Adjusting offset resistor has no effect on the offset voltage. Referring to other forms, I connected 1M across +15 v and -AIN, and 1M across Gnd and -AIN but still did not change. I have tried many resistor values (8K, 3K, 20K) for R3 but offset voltage is unresponsive to R3. How do I change offset voltage ?


texts:
This is a follow-up to Is this line detector safe?

I'm re-designing the front-end based on some great feedback from the community. I've decided to move to the following topology:

The phase of the source is set to 90º to model the worst case where a user closes a switch at the top of the line curve; in this case the caps would not yet be charged and R1 + R2 would have to absorb all surge energy
The surge current would be \$168.6 \text{V} / 1.6 \text{k} \Omega / 2 \approx ~ 53 \text{mA} \ll 150 \text{mA}\$, so the opto would be fine
During surge, the TVS would still not conduct, because
\$(168.6\text{V}/2)+1.1\text{V}=85.4\text{V}\$, which is smaller than Vbrmin=86.5V
During surge, each resistor would see a peak power of ~4.5W. If I use the
CF14JT1K60, based on its pulse derating curve, it would support 4W for ~0.1s, or 50W for ~1ms. Since we have 4W for less than 1ms, we should be quite OK.
D2 is shown disconnected - in reality it would be connected but I wanted to simulate the circuit as if the protection zener never quite conducts under typical operation. I intended for it to only conduct if there's a transient above the usual line voltage.
R1 absorbs energy in the event of a transient spike if D2 conducts.
C1 and C2 are chosen to relieve the burden on R1 and R2 so that their typical non-surge power dissipation is small, and decrease typical current to the opto while still keeping it on. The intent is to provide about 10mApk to the opto. At 60Hz, the total impedance is about

\$2 \left( 1.6\text{k}\Omega + \frac 1 {2\pi j \cdot 60 \text{Hz} \cdot 300 \text{nF}} \right)
\approx 18.0 \text{k}\Omega \angle -79.4º
\$

which allows ~9.4mApk.

This equates to ~6.7mA RMS; the resistors each then dissipate about 53mW RMS of power each. This is well below the 250mW for which they're rated.

Transient Simulation

Voltages:

Current:

Resistor peak power:

Have I missed anything? Is my method sound?


texts: Use a 15µf capacitor instead of original 12.5 µf for a water pump?

texts:
I have a 0.5 HP water pump. It's having trouble in starting and I have noticed the capacitor is damaged. It had a 12.5 µF 450V capacitor. When i went to buy a new capacitor the seller gave me a 15 µf 450V condenser and he said we can fix a 15 µf in place of 12.5 µF and nothing will go wrong.

I just want to make sure that this will not be a problem.


texts:
I need help identifying this component on the board of my car amp that has burned out. Electronic circuit board knowledge is pretty much zero for me. But I’m good at fixing stuff so I want to try to repair this if possible. The component in question is a little brownish square. It looked like the 2 brown squares next to each other in the pics. Is it a resistor and where can I find this ? Also is the burn on the board too much to re-solder a replacement ? I apologize if I’m asking in the wrong place but maybe someone can point me in a direction here..
Thanks in advance!


texts:
Below circuit is an emitter follower supplying current to an LED. A DAQ board is outputting 0-10VDC voltage to the base and cannot supply more than 5mA. Thats why the LED is not directly hoked up to the DAQ output. In the below circuit increasing DAQ analog voltage output will increase LED current hence the brightness. But I want to invert this adding another transistor or using another transistor.

How can I invert this so that 10V DAQ output will make LED dark and 0V will make it bright?

How can we invert it by adding another transistor? Or maybe a PNP? But DAQ should be safe not loaded.


texts:
How is the (dis)charging process of capacitors in series calculated?

I know that
$$C_{total}=\frac1{\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}+...}$$
$$Q_{total}=Q_{1}=Q_{2}=Q_{3}=...$$
$$V_{1/2/3}=\frac{Q_{total}}{C_{1/2/3}}$$
I also know that
$$V(t)=V_0*(1-e^{\frac{-t}{R*C}})$$
$$I(t)=\frac{V_0}{R}*e^{\frac{-t}{R*C}}$$
My goal is to calculate the voltage progression while (dis)charging two capacitors in series. Is that even possible or is this process too random to be calculated?

Note that i do not want to calculate the behaviour of the capacitive electronic component the two capacitors form together. Instead I want to know the voltage drop at each capacitor (, their charge and the electric current flowing through them) at any point in time.

Hopefully this is an achievable task and not connected to excessive testing and measuring.

Thank You in Advance


texts:
Having no past experience on RF design I have recently been taught that placing stitching vias is a good practice. Reading the "definition" of stitching vias I am not sure that I can distinguish stitching vias from common vias. The definition I have read is from Altium:

  Via stitching is a technique used to tie together larger copper areas on different layers, in effect creating a strong vertical connection through the board structure, helping maintain a low impedance and short return loops. Via stitching can also be used to tie areas of copper that might otherwise be isolated from their net, to that net.

Is there a difference in functionality between the two types of vias?

  --------EDIT---------

Thank you both for the replies. You are very helpful. My design is based on RN2483 package which includes a MCU and a RF IC. If you check RN's bottom layer it is obvious (or I make a guess) where the RF IC is located because there are stitching vias.

On my PCB should I place similar vias?

Here is my current layout:

Now all the vias are connected to GND on top layer. Ignore the one that is overlapping the RFH trace. Now I will add a ground plane to bottom layer as well.

I am open to suggestions/corrections because as I stated it is my first RF design and I lack knowledge.


texts:
I have very basic knowledge in electrical engineering.
I'm wondering what is the best schematics to use SRD-03V-SLC relay with ESP-12 module?

Here is what I have now:

I use input form AC-DC 3.3v 0.9A supply to bring power both to ESP12 and relay
You can see ESP-12 is connected through 1K resistor to PC817 optocoupler which drives relay coil.
Relays is intended to switch 220VAC not more than 5A

So is such schematics correct/safe?


texts: Converting analog stereo to digital stereo

texts:
Analog stereo has two channels. One for every speaker.
Now, when can sample and convert the two streams of data from analog to digital.

But the problem, is what we will have is two streams of digital data.
But digital audio is one stream of data.

So is there a way (or a protocol, or specification) to convert the two streams of data to one?

I am talking about raw sound, not encoding and complression algorithsm (like mp3)

Is there a thing called digital stereo? And how are the two channels mixed into one?

This is what i am trying to do btw. Create digital stereo (one stream), from analog stereo (two streams)


texts: zener diodes, different voltages, and using a relay to control its opperation....will this work?

texts:
Ok so I am going to admit that I am an idiot when it comes to circuits. However, some advice would be appreciated with regard to my idea. I am trying to control two seperate circuits, each with different voltage requirements, and hoping to use two relays from one inital push to make switch...so here goes my attempt at the explaination. There is a zener diode in there also, which I need some help with because I may be placing it in the wrong position within the circuit for the outcome that I require.

Background information: The aim of the project is to have two actions take place simoultaniously, with one circuit controlling them both.

Circuit one is using a reference voltage (vehicle ECU) at 5v, this is passed through a POT (throttle pedal position sensor) and then returned to the ECU (0.25-4.75v dependent on POT position). After the POT but before the ECU, there will be a 3.5v zener diode in reverse bais mode, leading to ground, so that the maximum voltage the ECU ever recieves back is 3.5v.

Circuit two is much simpler. It is 12v constant voltage, controlling a solenoid valve, with full open and full closed positions.

Control circuit would be a push to make switch with 12v, the pushing of which button would allow the 12v to pass through to two relays, one of which completing the circuit with the solenoid valve, the other breaking the zener effect on the ECU circuit, and allowing the ECU to recieve more than 3.5v if the POT allows this.

I hope I have explained this enough so as you can understand.

I did have another idea, where the push to make switch would control the initial 3.5v zener only, and then have another 4.5v zener further down the line, so that this 4.5v zener leaked off the voltage to a relay which completed the circuit for the solenoid. This would then only open the solenoid valve when two requirements were met, one being if 4.5v or more was output from the POT, and the other being the push to make switch was activated.

I could be talking complete gibberish, but it kind of makes sence in my head lol

.
.
.

EDIT

OK so here is what I have come up with, given your helpful inputs.

simulate this circuit – Schematic created using CircuitLab

As you can see, when the push to break switch is pressed, the voltage the voltage sensor receives is not limited, when the push to break switch is not pressed, the maximum voltage the sensor receives is 3.45v or there abouts.

My next step is to incorporate the solenoid activation in to this some how, so that either:-

A) solenoid is activated when voltage is above 3.45v at the sensor (this would mean the push to break switch must have been pressed)
B) much simpler i think, simply using a double pole ( on/on ) switch so that the solenoid is activated, or the zener is activated, never both

I have cracked it!!!
PLEASE READ CAREFULLY BEFORE ANY ATTEMPT TO TEST!

There are two variable resistors, both of them (R1 & R2) are connected to the same sensor on the throttle pedal. This is to ensure the ECU can tell if one is faulty, by having voltage linearization between the two, one raising the voltage, one reducing it. Whatever happens to one POT must also happen to the other. SW1 is a push to break switch. The solenoid valve will be wired in after the lamp, I could not find a solenoid sign so I thought why not incorporate a lamp to indicate when this was activated, and also for the purposes of the simulation.

If anyone finds any faults with it, I would be more than grateful if you could bring these to my attention.
Thank you.

simulate this circuit


texts: Is there a way to tell what frequency I need a PWM to be?

texts: I have a 12V DC motor that turns at 60 RPMs or 1 Hz. Do I need a PWM that matches the frequency in order for it to work? Most of the ones I've seen are around 25 kHz for a 12V 20A motor.


texts: Filter noise from a high voltage DC-DC converter

texts:
After finding a couple of triodes lying around I decided to build a valve preamp. I've built a simple boost converter based on a 555 timer to generate anode voltage.

The circuit is powered from a 9V mains adapter. VR1 is adjusted so that I get approximately 200V output.

'HV' output goes directly to the anode of the valve through an RC-filter (R=33 Ohm and C=220uF).

When I probe the output of the amplifier I get a lot of noise from the boost converter (here is example of the noise superimposed on a 4.4kHz sine wave):

When I disconnect the power from the boost converter, the noise disappears and the signal is perfectly clean (while there is some charge left in the output capacitor).

How do I filter out this noise? I thought that the RC-filter would be sufficient, but apparently it's not.

edit:
I removed a 33 Ohm resistor from the RC-filter and added an LC-filter. Here is the schematic of the output:

The amplitude of the spikes now decreased, but the noise is still present.


texts: How is SNR (Signal-to-Noise-Ratio) related to receiver power?

texts: If I have the instantaneous SNR (of the receiver) but no other information, and I am interested in the instantaneous Powerreceived, is there any relationship between these two terms?


texts: How to calculate \$R_{\text{in}}\$ in this circuit?

texts: I know for an ideal inverting op-amp, the equation for finding gain would be \$\frac{-R_1}{R_{\text{in}}}\$, but how can I find \$R_{\text{in}}\$ in this circuit?


texts: Identify Single wire communications protocol

texts:
Hi guys
I  I have uploaded pictures from an oscilloscope.
 This is the signal that an indoor AC unit sends to the outdoor unit. It uses a single wire for communication and Seeing the PCB it looks like it is attached to a temperature  sensor through optical  isolation. Can someone suggest me the communication protocol it might be using? Also as far as I have looked CAN BUS can be used in a single wire mode. If this is CAN how should I start decoding it?


texts: Purely Solid-State Circuit Withstanding 1kV, able to source 125mA

texts:
I'm looking to design a purely solid-state circuit that can perform the following:

Handle an AC Source with Vpk=1kV and act like an open circuit. (Schematic 1)
When the source is removed and replaced with a 10Ohm load, source 125mA from a 2.5V Source. (Schematic 2)

I realize the most obvious choice for this problem would be a mechanical relay, but I am trying to find a purely solid-state solution. There are 1.5kV solid state relays (extra 0.5kV is for safety measures), but the highest current I've found for these is 45mA and their internal resistance is too high (300Ohms). Have been simulating various combinations of BJTs, Diodes, and SCRs for about 4 hours so far and still have not been able to find a solution. Main limitation has been that P-Type MOSFETs and BJTs max out at 600V.
Any help you can provide would be greatly appreciated, and I realize that 'no solution' is a potential answer. Thanks


texts: TVS for CAN lines protection need to be bidirectional?

texts:
I'm using a line that is multiplexed to be used with digital 0-5V, 0-7V and CAN. I don't know very much about CAN swing voltages, so, I have some doubts:

Need CAN protection to be bidirectional? If I use a unidirectional protection will interfere in the communication ?

I'm affraid that during a negative peak, using a bidirectional TVS diode, the voltage at the pin of the device will be negative and it can damage the devices that are not CAN, the CAN transceiver can tolerate negative voltage, but the others don't.


texts: Voltage wave form across a DC motor driven by a transistor with pwm

texts:
Above is the simple implementation for a DC motor control with pwm.

I was expecting to see a square wave with a Vmax when Q1 is ON and zero when Q1 is OFF like the one here:
standard pwm

But what I saw in oscilloscope is different. The OFF stage is not zero and even increasing when pwm is increased. And when I stall the motor with my hand the OFF stage then really becomes zero. But not when rotating.

Here is the video where i adjust the pulse with frequency:
DC motor voltage on scope

Why is the voltage is not going to absolute zero during Q1 OFF, instead it is increasing when duty cycle is increased. Ok Q1 is on the volatge should be there but why still there is voltage when Q1 is OFF and why it is increasing with pwm's duty cycle? Plus as I said before the wave form becomes exactly a pwm with zero for OFF stages "when I stall(stop) the motor with my hand" (when stall a bigger current passes and voltage decreases).


texts: Selecting a MOSFET for driving load from logic

texts:
I'm looking to drive a magnetic door lock from an Arduino. I've found a question about driving a solenoid from an Arduino, which includes a circuit that looks perfect for this kind of situtation:

What I don't understand is how to select a MOSFET for the job. What properties should I look for, if I know my logic level, device voltage and device current?

In this case it's 5V logic, and the load runs at 12V / 500mA, but it'd be nice to know the general rule.


texts:
N=200
I=N*8A
l=20cm=2*10^-1
d(delta)=1mm=10^-3
M=?

M=(B/μ)-H

How can I get the vector of magnetization? The relative permeability is not known. Everything I tried so far needs this value. There is no "shaking" of the magnetic field in the air gap.
Is this true Hm=-Ha (H magnet =-H gap) ?


texts: Switching between 3 power sources using a microcontroller

texts: I am doing a project in which I use 230V mains to charge a battery. If mains power is down, I have to use solar power for charging; and if the solar power is not good I have to switch to the diesel generated power. I have to do this using a microcontroller. Also, I should display the the source with which the battery is being sourced on a lcd  display. How do I do this?


texts: Frequency Measurement using FPGA and VHDL

texts:
I am not very experienced at VHDL coding. I want to measure the frequency of my input signal. It varies between 1 Hz to 150 kHz. And my clock frequency is 250 MHz. I wrote some code but it is not working properly. Could someone help me please? How can i handle this?

Thanks.


texts: How can I connect more than device on the same Isolation transformer?

texts:
Why isolating transformer should be used to protect only one item of equipment at a time?

I tried to search and I found this answer, but I could not understand it.

  This is why, ideally, an isolating transformer should be used to protect only one item of equipment at a time. With one item a fault in the equipment will probably not produce a dangerous situation. The transformer has done its job. BUT with N items of equipment - if one has a fault from neutral to case or is wired wrongly this may defeat the transformer such that a second faulty device may then present a hazard to the user.


texts: Powering my 5 volt project with AA batteries

texts: I am thinking about using 1 AA Battery with these battery holders and this boost converter to power my 5 Volt arduino project, My project will pull about 100mA. Is there any problem with doing this? I don't see any issue with using these together to power my project, but I wanted to get other's opinions that before I buy these products. Thanks for the help!


texts:
I was measuring the voltage at the intermediate frequency output of this tuner http://superkuh.com/gnuradio/R820T_datasheet-Non_R-20111130_unlocked.pdf using the oscilloscope. The tuner has a differential output with the impedance of 2kOhm/5pF.
Let's say that I measured 5 mV at the positive dif. output. Now I need to somehow calculate the power. According to the equation that P[dBm]=10*log((Vrms^2/|Z|)/10e-3) the resulting power is about -26 dBm. Can I say that the power transferred through the positive differential rail is -26 dBm or not ?
I am not sure whether it's correct because the voltage I measured is referenced to the ground of the oscilloscope and differential lines have floating grounds.
Another question is: assuming that positive and negative rails (with same amplitude but inverted phases) are subtracted at the end, the resulting voltage should be two times greater. Thus the power at the subtracted output should be greater by 3 decibels ? Can I make an assumption like that ?

Thank you for your replies


texts: Use a li-ion battery at two different voltages

texts:
I scavenged a li-ion battery from a broken laptop. It is made of 6 Samsung ICR18650 cells (3.75V 2800mAh), parallels two by two so that the total pack is in fact the sum of 3 cells at 3.75V, so 11.25V (it's written 11.1V on the pack).

I have a raspberry pi which can run out of only one power boosted cell to 5V.
But I also have a TFT screen which runs on 7-12V (consumes less battery near 12V than near 7V).

I would like to know if I can actually plug the screen to the full battery, and the raspi to only one third of it.
I know cells have some kind of "balance" so I am wondering if that could make the battery unstable as one part of it would discharge at a faster rate.

As another solution to my problem, would it be possible to powerboost 5V to 7V or 12V so that everything runs from the same number of cells ?


texts: Why do I have voltage on Collector and Emitter when NPN transistor turns on? How to get rid of it?

texts:
I have a 2N3904 NPN transistor. I'm feeding the base 5V. the transistor turns on just fine and it shorts the collector and emitter. However, when I turn my meter on volts, I read around 1- 1.5 volts across E and C. I am using this transistor in a project as a sinking output. Why am I reading this voltage and can I get rid of it?

I'm controlling the transistor with an arduino. Im writing HIGH for 4 seconds, then LOW for 4 seconds. I'm only showing 1.5v across the E and C when the arduino writes LOW!! What is going on??

EDIT: I attached a drawing.

Here's some more info:


texts: Propagation delay in shift register - in the context of a serial adder

texts:
The first figure (from Fundamentals of Logic Design, Roth/Kinney, 6th Ed, p.404) shows a serial adder which feeds in operand bits and stores the sum, and uses a D flip-flop to store the carry-out from each bit pair and load it back in as the next carry-in.

The second figure (from Fundamentals of Logic Design, Roth/Kinney, 6th Ed, p.405) shows a timing diagram for this same serial adder.

My question is: is there a good reason why the delay in loading the operand bits (x_i and y_i) would be depicted as being longer than the delay in loading the carry-in (c_i)? This seems important, because (as shown in the timing diagram) it leads to glitches in the sum, s_i.
I have assumed (though the textbook does not absolutely confirm this) that shift registers made of D-type flip-flops (like the one for the carries) would be used to feed in the operand bits and store the sum. If so, surely the delay for loading x_i and y_i would be identical to the delay for loading c_i?
If not, can anyone cast light on another reason why the timing diagram depicts things this way? I have searched unsuccessfully online for an answer, and one is not contained in the textbook itself to my knowledge.
To be clear: my suspicion is that the authors made a mistake (I am guessing they did not allow for flip-flop propagation delay in loading c_i) -- but I'd like to get a knee-jerk response from more experienced folks indicating whether they would tend to agree with me, or whether I'm missing something really obvious? Thanks!


texts: Interfacing a keypad with a microcontroller

texts:
I am using a PIC16F877A, running at 20 MHz.

I have two paralleled, 3 columns, 4 rows keypad. My setup is as follows:

KR1 to KR4 are rows, KC1 to KC3 are columns, and they all go to the microcontroller.

In the program, rows are set as digital outputs and columns are set as digital inputs. Other peripherals of the pins are disabled. The way I scan the keys is as follows:

I make the first row bit HIGH, then I check column 1, column 2 and column 3. If any of them is HIGH, then I wait a little and check again to de-bounce. If it is still HIGH, the program decides that a key is pressed. This routine follows for the other 3 rows.

I check the keypad about every 100 ms, and for each row, it takes about 2.4uS as I measured with the oscilloscope. That, I guess, means, for a specific digit; set it high then try to measure for about 800nS, if nothing happens, move on.

So the problem was weird. Every digit worked, except from '0'. It worked randomly and that random means rarely at the same time. Also, when I tried to measure its voltage to the ground with a multimeter in DC volts mode, and then pushed the button at the same time, it worked for every press.

Then I added a delay of 5 uS after making the specific row HIGH and then I checked the columns. It worked!

Now, what is the problem here? The keypad wires are about 30 cm (~12 inches) long. Is it some kind of a transmission line problem, like it is adding a delay? Or is the problem is sourced from the microcontroller; the microcontroller is not fast enough?

Here is a portion of the code that is relevant to the issue:

...

KEY_R4 = 1;
delay_us(5);
if (KEY_C1)
{
    scan_keys.waitstate = 10;
    goto c4r1;
}
else if (KEY_C2)
{
    scan_keys.waitstate = 11;
    goto c4r2;
}
else if (KEY_C3)
{
    scan_keys.waitstate = 12;
    goto c4r3;
}
else
{
    KEY_R4 = 0;
    presstime = 0;
}

...

c4r2:
if (++presstime >= PRESSTIMEVALUE && !KEY_C2)
{
    scan_keys.waitstate = 0;
    KEY_R4 = 0;
    return '0';
}
return 'n';

...


texts: BJT Veb matter & use of the Ic-Veb Exponential Relationship

texts:
In the following circuit Ic must be found.

I begun by open-circuiting the 3 capacitors, and finding the voltage at the base which is 2.5V (from the voltage divider).
By assuming that Vbe=0.7V it's easy to progress, however no such thing is stated (the only data given is that β is very large), so i was wondering if there is a way to find Ic without that assumption.

If we do assume that Vbe=0.7V, then when is the Ic=Is*e(Vbe/Vt) formula used?


texts: How to physically connect AS3933 to 3D antenna?

texts: I'm trying to breadboard LF frequency receiver circuit using AS3933 receiver chip IC and CAS143-147 3D antenna chip. However I don’t understand how can I connect AS3933 pins to CAS143 on a breadboard. CAS143 seems to be a SMD chip but it uses it's own weird pad spacing. I'm wondering if soldering breadboard jumper wires directly to chips pads would work and if not what is a recommended solution besides ordering custom PCB (I'm looking for a cheap and quick solution)?


texts: Is the current in reverse biased PN junction due to drift or diffusion?

texts:
Wikipedia says

The saturation current (or scale current), more accurately the reverse saturation current, is that part of the reverse current in a semiconductor diode caused by diffusion of minority carriers from the neutral regions to the depletion region.

Another site says: http://www.ece.utep.edu/courses/ee3329/ee3329/Studyguide/ToC/PNdiode/currents.html

When the diode is reverse biased diffusion is negligible, but drift remains constant.

I am confused, should we regard the reverse saturation current as a drift or diffusion current?
I'd be glad if you could explain. Thank you.
Wikipedia:https://en.m.wikipedia.org/wiki/Saturation_current


texts: Question regarding PCB design layout of Raspberry Pi

texts:
I have query regarding PCB design layout of Raspberry Pi (RPI). I wanted to know how LAN9512 chip is connected to Ethernet RJ45.

I found one of PCB layout picture which suggests there is line on PCB which goes from LAN9512 chip to Ethernet RJ45 which I guess mark as R23.

What does R23 represent in PCB design, is it some kind of system bus or USB bus?

Same way how CPU/GPU is connected to component like D2 & D3 (RAM)?

(Original Image)

(Original Image)

PS: I'm not at all familiar with PCB design.


texts: Calculating number of coil turns for a generator

texts: I'm building a generator for a school project. I'm planning to use N42 neodymium magnets with performance of 5100 Gauss, How do I calculate what diameter of copper wire I need to make the coils and how do I determine the best number of turns for that particular set up?


texts:
The following periodic function, \$x(t)\$, is the input to a linear, time-invariant system  The impulse response of this system is $$h(t) = \frac{\sin t}{t} $$ which I converted to $$H(\mathrm{i}\omega) = \pi\,\mathrm{rect}\bigl(\frac{\omega}{2}\bigr).$$ I want to determine an explicit expression for the output \$y(t)\$. I have determined that the period \$T_0=3\$ and \$\omega_0= 2\pi/3\$. I know the equations for the fourier series transform is
$$x(t) = \sum_{n=-\infty}^\infty C_n \mathrm{e}^{2\mathrm{i}nt}$$ and similarly I have $$y(t) = \sum_{n=-\infty}^\infty D_n \mathrm{e}^{2\mathrm{i}nt}$$ where \$D_n = H(\mathrm{i}n\omega_0)C_n\$ but I don't know how to proceed.


texts: Choosing a correct transformer for a power inverter?

texts:
How does one choose a proper main output transformer for a power inverter? Is enough to simply use a "standard" transformer "in reverse"? Also, do toroidal transformers convey any special advantages to inverters?
This would be for a North American system with a 120v/60hz output, but the DC input voltage is negotiable, and could be 12v, 24v, or something else.


texts: How to determine low and high threshold levels of a Schmitt Trigger for a known input?

texts:
Imagine I have a pulse train input which goes into a Schmitt trigger for getting sharpened. Imagine the HIGH of the input pulse train is around 8V and LOW is around zero volt.

So what should one select the lower and upper threshold voltages in this case? Does that depend on the desired HIGH output voltage? And what is the logic behind determining these threshold levels?

I found this calculator which one needs to decide about the low and high tresholds: http://www.random-science-tools.com/electronics/schmitt-trigger-calculator.htm


texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to get the hang of power flow analysis and I can't figure out how to measure the power (P and Q) between two inductances.

[E source] ---> [L inductance] ---> measurement ---> [L inductance] -----> [U source]

Q   =   ((E^2)/(X))-((E*U)/(X))*cosd(PhaseE-PhaseU);
Q   =   ((E*U)/X)*cosd(PhaseE-PhaseU) - (U^2)/X

[Edit to be reviewed by OP.]

$$    Q   =   \frac {E^2}{X} - \frac {E \cdot U}{X}cos(phaseE - phaseU) $$
$$    Q   =   \frac {E \cdot U}{X}cos(phaseU - phaseE) - \frac {U^2}{X} $$

[End of edit.]

These formulas doesn't cut it because they give the result for either end but not the middle.

Do I need to add something to my formula?


texts:
simulate this circuit – Schematic created using CircuitLab

First up I don't know if the direction of Ib is right for the pnp transistor in the circuit ( I need to know the active region relation so, as the emitter-base forward current will be more than the collector-base reverse current, I have given this direction for Ib ) . I want to know how Ic increases with increase in Ib. I have seen a lot of explanations based on equations but I need to know what causes the relation between Ic and Ib.


texts: STM32F3 Discovery + GNU ARM plugin + OpenOCD - cannot load the binary onto the board

texts:
I'm using the GNU ARM plugin for Eclipse with Open OCD as a debugger. This is on Windows 10 x64. The problem I'm facing is the following error when trying to debug or run the sample program:

  Error in final launch sequence
   Failed to execute MI command: load C:\Development\stm32-test\Debug\stm32-test.elf
  Error message from debugger back end:
  Load failed
  Failed to execute MI command: load C:\Development\stm32-test\Debug\stm32-test.elf
  Error message from debugger back end:
  Load failed
  Load failed

There are several kinds of STM32 project templates that the ARM plugin offers. Most notably, there's the "STM32Fxxx C/C++ project", and it works out of the box no problem. But it's bundled with the old version of STM32 library. I wanted to use the latest STM32F3Cube, so I used the other template - "Hello World ARM Cortex-M C/C++ project", as per the recommendation of this article. It's designed for use with the STM32F3Cube, and it's the one I can't load onto the board.

Please tell me what further information is needed for dealing with this issue, or how I can collect more detailed logs etc.

P. S. I have compared the debug configuration settings between the working and non-working projects, and found no difference. Same .cfg file, along with everything else. Is my .elf being rejected because there's something wrong with it?


texts: Programming an ATmega328 with Arduino bootloader via a FTDI USB-serial adapter

texts:
I would like your advice relating to using the Arduino IDE and avrdude to program an ATmega328 which is preloaded with an Arduino bootloader. I am using a USB to TTL-serial breakout board based on an FTDI chip.

I bought a "FTDI Basic Program Downloader USB to TTL FT232 for Arduino ACC" off ebay

I followed exactly this setup:

Connect the DTR pin to pin 1 on the ATmega through the 0.1uF capacitor.
Connect the RX pin to pin 3 on the ATmega (TX)
Connect the TX pin to pin 2 on the ATmega (RX)
Connect the 5V pin to the 5V rail of the board to supply the board with power from the USB interface.
Connect the GND pin to the GND rail of the board

 (from instructions being followed)

When I try uploading a sketch, I get this bad boy :

avrdude: stk500_getsync(): not in sync: resp=0x00

Here's what I have tried so far:

Connecting the header pins of the Arduino "shield" to the chip on the breadboard. In doing so I am using the ATmega16U2 on board to send the program. Result: Flawless! the program boots and everyone is happy.

Back to the FTDI breakout board. Switch RX and TX (never know?) still nothing so switched back to initial TX - RX configuration.

The DTR pin out of the FTDI board is successfully resetting the ATmega328 for sure as it goes through its magical blinking sequence when I try to upload something.

Now, I've tested to see if the ATmega328 can send serial info through the breakout board to by computer. It can.

I've noticed a few interesting things:

Both the TX and RX lines are always at 5 V. I know this because if I connect a LED in parallel with the lines, they light up.  But, the little tiny LEDs on the breakout board labeled TX and RX are not always on... why is that? Could that explain my problem?

If you'd like any more info, let me know, I'll get it for you.

---------------------------------------------EDIT------------------------------------------

Hello again,

OK I've added a 100uF electrolytic capacitor along with a 0.1uF one between 5v and GND. This isn't the suggested 47uF and 0.1uF but I guess it`ll help filter out none the less. ( while at it. What would it change?)

I've replaced my 1k pull-up resistor with a 10k one

I still am not able to upload a sketch and get the same error. DTR line calls a reset and I still get serial output. (I have a sketch on it that sends incrementing integers through serial every second)

Also interestingly, (although I was still unable to send a sketch before this happened) any LED I plug on pin 13 (aka 19) is now much dimmer... maybe that utlra bright white LED I had earlier was pulling to much current with a 270 ohm resitor... -_- )

To popular demand here are pictures of my board and the USB to FTDI breakout board I am using.


texts:
I want to make a 0–300V variable DC power supply (max current 100 mA). I found this design,

which features a 1:1 transformer across the mains for some sort of safety reasons. However, I couldn't find any 1:1 120 VAC transformers that weren't incredibly expensive. Next I looked at this circuit,

which uses a light-bulb "in order to provide ultimate safety in case of a short circuit or a component failure."

I'm not myself able to ascertain if the correct design precautions are being observed in either of these circuits. The second claims to be lethal to the touch.

My question is: does this second circuit exhibit any obvious safety-related flaws in its design (besides, perhaps, contact lethality)? If so, what is the cheapest method of achieving a 0–300V variable power supply while observing all relevant safety considerations, and will any DIY implementation be, to some extent, inherently dangerous?


texts: What happens when you fall off the end of main() in a PIC?

texts:
Another question included this program:

void main(void){
    TRISD = 0x00;
    PORTD = 0xFF;
}

Let us assume that it does exactly what was intended up through the last line of main().

My question is, what happens in a PIC18F4550 when the flow of control falls off the end of main()? I assume any decent PIC programmer will fill the instruction space after main() with either all-1s or all-0s, but I don't know which.

I can see from the PIC instruction set docs that an all-zeroes instruction is NOP, which is harmless in itself, but what happens when the program counter hits the end of the instruction space? Does it wrap around, halt, catch fire, emit monkeys...?

If PIC programmers fill program space with all-1s instead, as in an empty EEPROM, it appears that that will be an ADDLW instruction that adds 0xFF to W. If that is correct and we don't care about what happens to W, is this the same as the NOP case?

Do the answers to the above questions argue for doing something else, such as running an infinite loop to prevent execution from leaving main()? I don't think we can sleep the microcontroller here, since that won't keep the port D lines up indefinitely, as the OP wanted.


texts:
In my earlier question at  this link , i asked a question on how to use minicom in linux to communicate between two Xbee's in API mode and got the answer. While i tried the same with XCTU on Windows one one side and AVR + Xbee on the other side,i was able to communicate between 2 Xbee.

On the AVR side, i had written this code to receive the char and store it in string.

#include <yuktix.h>
#include <debug.h>
#include <uart2560.h>
#include <util/delay.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <debug.h>

/*for sensor readings*/
#include <AVRI2C.h>
#include <spi.h>

//char Id;
//char cmd;
static char ch;
static char *frame;
static uint8_t index = 0;
int main(){

    init_processor();
    uart_init(0,B9600);
    uart_init(1,B9600);
    uart_init(2,B9600);

    for(int j = 0; j < 1000 ; j++)
        _delay_ms(1);

    uart_puts(0, " \r \nstarting Xbee Test \r \n");

    while(1){

    while(uart_available(2) > 0){
        KDEBUG("Inside uart_available");
        KDEBUG("\n");
        ch = uart_getc(2);
        uart_putc(0,ch);
        KDEBUG("Saving it in frame \n");
        *frame++ = ch;
        KDEBUG("saved in frame \n");
        //if(ch == '\\');
        }
        KDEBUG("COming out of While loop");
       *frame = '\0';
        KDEBUG(frame);

   }
}

As per my last question answer, i am receiving char on the AVR side. As every frame of XBEE API mode start with 7E, where 7E is equivalent to ~, i am receiving it, but some of the chars were unreadable and data which i send in the API frame is totally readable. My question is

How can i store received API frame in a string as my code don't seems to work.
Should i convert the string into HEX via some binary_to_hex code and then parse it , as i need to know from which address this data is coming, what kind of frame it is, what is the number of the bytes in the frame, so that after excluding the source address , i can take out the data.
Am i missing anything. Data on the AVR side will always be in Binary, but how can i process the data?


texts:
Long time lurker and relativly new to electrical engineering but this is the first time I've had a question so I just made an account.

I would also like to start off by saying that I tried to follow this thread but none of the solutions seemed to help my problem. The audio can only be heard if you hold the speaker to your ear.

I followed this schematic from http://www.circuitbasics.com but the output of the speaker is quieter than when I directly attach the audio jack to the speaker.

This is a picture of my circuit

I'm not sure if all the extra wires is increasing the resistance to the point of muffling the output sound but it made connecting the battery and speaker easier and the 10K ohm potentiometer's pins were bending a lot to fit in the board so I just took it out and connected it via jumpers. The 9v battery is outputting roughly 8.3v and even if I add another 9v battery to the circuit in series the speaker doesn't get any louder, just more distorted.

Also the LM386 chip was getting very hot to the point where it burned my finger on contact and one solution I found was to connect pin 1 to pin 8 and that seemed to have solved the overheating problem but no difference to the audio output.

The stereo audio jack connector I purchased had two "3" connectors from the schematic (not sure what the technical term is but the datasheet showed 2 downward ports) so I had soldered them together before realizing it wasn't necessary and disconnecting them.

I looked the datasheets of the parts and nothing stood out to me as causing the problem but if someone who knows more than me could have a look I would greatly appreciate it.

The parts I have are as follows

10K ohm potentiometer (part # 296UD103B1N)
LM368 Chip (part # LM386N-1/NOPB)
1000uF polarized capacitor (part # EEE-FT1C102GP)
0.1uF capacitor (part # FG26C0G2A104JRT06)
10 ohm resistor (part # CCF6010R0FKE36)
3.5mm audio jack connector (part # SJ5-43502PM)

The 8 ohm 2 watt speaker was the only one I have on-hand so I'm not sure if the speaker is the problem but I'm planning on connecting this to a 555 audio modulated fly back driver so the speaker isn't necessary.

Any help or pointers would be very appreciated for this newbie engineer. If anyone has any questions or concerns I will try to answer them.


texts:
I am new here and I don't know if I have chosen right stackexchange but anyway.

I am making a little toy, just for educational purpose. I would like to understand how light strike works. It is a gun which lights some light, sensor somehow detects it and count the points.

I am wondering because it works even in day light.

It is similar to Laser Tag, which I understand, because you must be in dark place and you "shoot" laser beams. But how come that Light Strike doesn't shoot direct light. Is it some radio wave?

Even if you can't answer the question, don't you have any advice how to shoot something what can be received by some sensor?


texts: ON/OFF strobing multiple high-power LEDs (500mA+)

texts:
Goal: I have an application requiring strobing of many (30+) individually addressable, high-power (500mA+) LEDs. Each LED sequentially will be switched ON/OFF at a rate of about 10Hz, switching from one LED to the next in sequence at a rate of about 100Hz. Full ON/OFF would be sufficient, but some means of dimming would be nice.

I have three main ideas about how to implement this:

A constant-current buck driver (e.g. PicoBuck).
A linear voltage regulator / MOSFET approach.
A high-amp constant-current driver chip. I have been looking through the Texas Instruments driver catalogues, but I haven't found any multi-channel LED drivers with similar functionality above about 120mA output per channel. So I may need to use a single-channel driver like the TL4242. But if I need to use many single-channel constant-current drivers, how would I go about synchronising them? Could I "drive these drivers" with some daisy chained TLC59711 drivers or similar? Is this even vaguely sensible?

Is there an obvious chip choice or implementation that I haven't spotted? I'm fine with having a few dozen chips on a breadboard/PCB, if that's the most sensible way to do it.

Thanks


texts:
The following are two possible grounding schemes for a sensitive instrument that contains high gain analog circuits and potentially noisey digital circuits:

This circuit is connected to an external power supply over a 1M cable. There are 3 separate ground conductors in the cable running back to the star ground of external power supply PCB.

The scheme in the first illustration above has an issue. The digital noise can be significant enough to bleed into the analog circuit. Originally I theorized that with a large bypass capacitor connected close to the ground of the digital circuits, that any noise would be minimal and leave the analog circuit unaffected. Normally this works because the analog ground has it's own conductor. Unfortunately, this is not always true. Specifically, an LED driver (like CAT4016 or TLC5925) can generate very sharp currents. No amount or combination of local bypassing seems to have much of any effect on the voltage spikes generated by these chips. If I remove the LEDs and leave the digital communication there is no noise. But the load of the LEDs creates large 100mV spikes in the power ground wire. If the analog ground is connected locally to the power ground, this noise will bleed into the analog circuit (it is sometimes desirable to connect the output of an amplifier generating larger currents to the power ground instead of the analog groung for example).

In the second illustration above, the digital ground is given it's own dedicated conductor. In this case, the digital noise problem is completely resolved. LED drivers and digital noise are completely isolated. My test circuit has a SNR of more than 100dB and I suspect it's better than that but my analyzer is a cheap codec-in-a-box thing that runs on 5V so it's dynamic range is limited.

However, here is the problem:

To give the digital ground it's own dedicated conductor, I moved the chassis ground to the power ground conductor. So electrical discharge into the enclosure it will cause a significant spike in the power ground. Also, the power ground is potentially a source of noise that might be coupled into the analog circuit through shields and adjacent traces.

So the question is, is sharing the power ground with chassis ground a good idea? The enclosure would actually be grounded trough this conductor. It should only have power bypass capacitors and maybe some larger AC currents. But there shouldn't be any DC.

Note: Only ground wires are shown in the illustration. The cable would of course have other power wires but I'm reasonably curtain that the problem has to do with grounding and as such only the ground networks are shown in the illustrations. So there are numerous other power lines that have been omitted.

So what do you think? Is it ok to use the power ground as chassis ground?


texts: why does a x100 oscilloscope probe grant a wider bandwidth than a x10 probe

texts: I was asked in an interview the question                                          "why does A x100 oscilloscope probe grant a wider bandwidth than a x10 probe? How much does it widen it?".


texts: Understanding PLL VCO Integrator Phase-shift

texts:
In many PLL phase loop theory discussions, it's often said that the VCO acts as an integrator and therefore has a 90 degree phase shift.  I've seen derivations of the VCO transfer function and this image (taken from here) is particularly enlightening:

Here we see the integrating behaviour of the VCO where Vcontrol is integrated to produce a phase that rotates forever around the time axis.

So, $$\theta(s)=K_{vco}\cdot \frac{V_{control(s)}}{s}$$

What I'm having problems with is the "90 degree phase shift" part.  I understand that integrators have a 90 degree phase shift and the classic example is the RC low-pass filter.  Here the phase shift between input and output voltage can be understood by the voltage/current phase relationship of the capacitor.

But, I'm struggling to understand the 90 degree phase difference of the VCO in a similar intuitive way (especially since the product of the integration is phase).  I assume it's between the phase output and some reference.  But, I'm struggling to see what that reference is.  Is it the control voltage?  But, then that's a DC voltage, right? Can anyone help me out?


texts:
I am designing a 4 layer smps (low noise) and I have a some design philosophy questions .

Under the transformer (that separates primary from secondary) should I extend the ground planes ( one primary side and second secondary side) all the way to mid transformer ( I keep a few mm of creepage between the 2 grounds) or should I extend the ground only to the pins of transformer (both sides) ?

Output (secondary side) I have a  common mode choke on DC output. Should I make a ground plane for the CMC and wires output (small ground plane in addition to secondary ground) or I should keep the main ground as big as possible and output of CMC + wires with only traces ?

Bridge rectifier has a capacitor on output and after capacitor, 2 ferrite beads on positive and negative. Should I create a ground layer (small) for bridge rectifier + C and then declare the main primary ground (much bigger) after those ferrite beads ?

On AC side, I have a CMC , Y capacitors etc. Should I use a ground layer on the AC or traces (hot and neutral) without ground layer .
Sorry for so many questions but I have read a lot of articles and I am still unclear on whats the best way to design ground planes for ultra low noise smps.


texts:
I need to monitor approximately 25 sensors, none of which is greater than 80m from the monitoring device.  The monitoring device will be a single board computer, e.g. beaglebone black, (yet to be decided).

I will be monitoring conditions such as temperature, lux, etc.  It will be sufficient to take one sensor reading per minute, (i.e. 25 int total per minute).  Because of the variable distance, I do not want to monitor potential noisy and attenuated analog sensor signals. I2C/ SPI are not suited for long distance so this leaves protocols such as CAN, RS485 or Onewire.

I am looking for a protocol that is support by CE marked sensors that can be plugged directly into the SBC.  I don't want to have to build and certify each sensor we devise.  For example, I could easily build a CAN sensor board but it would cost thousands to run such a sensor through compliance testing.  If I negate compliance testing and the building burns down I will be at fault.

I have seen elsewhere a recommendation for CAN for use with wired sensor networks but I cannot find suitable sensors for sale.

So, any ideas for a communications protocol for wired sensors that has industry support?


texts:
There is a device which has output impedance 150ohms. If my headphone has either lower(30ohms) or higher (400ohms) impedance can I use it or sound will be too low/high and it will be unsable?

Also, the volume higher/lower is being done by the device by changing the impedance or by changing voltage?

Thanks

EDIT: device outputs: 35mW in headphone output jack, impedance 150ohms.

-Can i connect my headphone of it will damage it?

-Will it work?

-When it says 35mW what does it mean? 0mW no sound, 35mW volume max?

EDIT2:

If output is 50mW, impedance 150ohm then P=V^2 / R , so V= 2.74 ??


texts: Where can I find a transistor similar to a 2n 3904?

texts:
I have what I believe is a 2N 3904 638 transistor.

It measures 50MΩ at around 70°F.

How can I find a data sheet on this?
How would I go about finding a similar / replacement thermistor?

PS: I did try Google Searching for those numbers but didn't come up with anything definitive, so this is partially about learning what the right way to identify / look up components is. Also, if I need to graph the resistance over a temperature range I can do that as well.


texts: How to drive 32-by-32 (or more) LED matrix?

texts:
I have a matrix of 32-by-32 LEDs that I need to control using a driver. The largest driver that I found was a 16-by-16 driver by Linear Technology, and there is no driver that goes higher than 16-by-16.

Here are the requirements:

monochrome LEDs (color not needed)
LEDs just need to go on or off, no greyscale required
pixels cannot be addressed individually, need to use column/row method

Is it possible to use two or more drivers together for this purpose? How? If not, what could be the alternative?


texts: Is there a relation between the voltage of a Li-ion battery and its charge?

texts:
I have a Li-Ion battery-powered device (Wemos, an ESP8266 based) and I can read information about the voltage applied to its input.
Is there a relation between this voltage and its remaining charge?


texts:
I had my plumber change the PCB of my boiler last year. Last week it stopped working and I tried to troubleshoot the problem. The circuit board just doesn't show any sign of life, the ON LED doesn't turn on at all.

On the board I see a brown area. I suspect it has burnt but the damage doesn't look really important, so I would like to check with you if this indeed looks like burnt damage and if that could make the whole PCB dead:

Thanks in advance


texts: I'm trying to make a NOT gate, but with a PNP transistor instead of NPN.  What would a wire diagram look like for a NOT gate with a PNP transistor?


texts: Hello, Im trying to identify this Resistor

texts:
This is from a surgical operating table. I believe this resistor is bad. Im not 100% sure. I test it and it gives me no reading at all, no resistance reading nor contuinity reading.

Edit* Added a picture of the underside.


texts: Powering high power LED modules/plates (series parallel internally)?

texts:
I am trying to build a high power RGB LED light. I am looking for 50W-100W range for the LED (all colors combined). 100W RGB LED desn't seem to exist so I am left with 50W, 60W, or 90W options. I would prefer higher wattage single LED module as it's cheaper than multiple lower wattage modules.

There is a suitable 90W LED module. There is no datasheet only this spec:

  Voltage: R: 20~22V; G: 32~34V; B: 32~34V; Current: R: 900mA; G: 900mA;
  B: 900mA; Product size: 45mm x 51mm; Power: 90W; Wavelength: R:
  620~625nm; G: 520~525nm; B: 460~465nm; 10 series and 9 in parallel;

I heard that for LEDs in series/parallel you need some additional components for current sharing etc... Do these LEDs have the required circuitry built-in making them essentially the same as a single LED in respect to powering them? Or do I need a special LED driver to power this module? Reason I am asking is because  most LED drivers don't mention any specifics about series/parallel LED but I did recently see an LED driver with PWM control that specifically mentioned it's application was for LED module 1 x 50W multichip(10 Series x 5 Parallel). Does this driver have special circuitry or is it just a suggestion for what it can be used?

What do I need to look for in an LED driver in general other than constant current, min/max voltage range and power rating to be equal or lower to that of the LED. (For the 90" RGB LED, each color would use it's own 30W driver).


texts: How to keep capacitor from discharging in/through regulator

texts:
I'm currently working on a project where I need the MCU to be able to keep running for at least a few seconds after the power have been interrupted (in case of power outage for example).

So I choosed a 470uF cap for the output of the regulator (AP7333-33), but unfortunatly when the power is interrupted, the cap discharge quickly in the regulator (and through the regulator, in the wall adapter).

I'd like to prevent this phenomenon, but I can't find a satisfying solution...

I tried to put a schottky diode between the regulator and the cap, but this is far from an ideal solution, as voltage drop and reverse leakage current lower the time my MCU have before shuting down.

I also tried various mosfet and BJT configuration, but could not find anything good.

I feel a bit stupid, ok I'm a beginner, but I'm sure such a simple problem have a simple solution !


texts:
I asked this question over at stack overflow but found this in a few of the comments on some of the microchip questions,
https://stackoverflow.com/questions/3276297/communicating-with-the-pic-16f913

Here is my issue, it appears that all the communication lines for the PIC 16F913 reside on the same set of pins, this is convenient in that I don't have to sacrifice GPIO pins just to do comms, however the problem I'm having now is if I'm using the SPI on the chip, how can I send information to the RS232?

The reason this issue came up, is that I just bought a CAN bus chip that communicates over SPI, and I would really like to see the data on RS232, so I can see messages. (I really don't know much about CAN yet, so who knows if this even makes sense yet).

Here are the options I see, and maybe someone else has better ideas that I'm just simply missing.

Somehow setup a time scheme that will switch between SPI and RS232 every time I get data,
-- This doesn't seem hard and should work, but supposing I don't want to miss a message, what if a message is written while I'm writing to RS232, is it possible I'll miss it?

2.. I can always use SPI, but then build my own comm bus over 8 of the GPIO lines, to another PIC 16F913, using only the GPIO lines and then since the RS232 lines are free on the second PIC I can simply read the data and spit it out.

-- This one is doable but now we're wasting 2 chips, AND all the GPIO lines,

There has to be a better way. Or is there?

Any help is greatly appreciated.

I would like to also clarify, obviously one solution is using a completely different chip (which may in fact be what I end up doing, if I can get the 18F programmed), however, I'm interested in worst case scenario, in which I am limited in resources and only have some 913's, is the way described above the only way to do it with this chip, or is there a better way?


texts: PIC16 - MSSP Peripheral I2C Master Halting In Middle of Clock Sequence?

texts:
I'm using a single PIC16F18857 as an I2C master to talk to five PIC16F1615's on the bus. All is working great, for the most part, however, I've been experiencing a "lock up" where the master is stuck in a loop waiting for a read to complete. I managed to catch it on the analyzer and here's what I'm seeing:

The third signal is an async UART input to the master PIC16, I was trying to see if the timing of it with relation to the  was somehow related, but I've seen nothing to support that so far.

There are currently only two slaves on the bus, and the read always fails during the read to the first slave.

What's curious to me is that the master (which is controlling the clock) seems to stop clocking the slave after three clock cycles (I'm seeing three cycles consistently) and I'm missing an interrupt -- most likely because the clock sequence is not finishing all of its cycles. I would be less puzzled if the clock was being held low by something, but it seems the clock is stuck in the "unasserted" high state.

Under what circumstances may this happen?

I have checked the silicon errata for both parts, nothing that pertains to this issue is listed for either part
I've tried to see if its correlated with another peripheral interrupt firing, none of the data I've collected seems to point to that being an issue

Thanks!


texts: Turn Node MCU into a PLC which is integrated Lora module for IoT application

texts:
I've built a PLC that supports Lorawan and Modbus protocol using Node MCU. I managed to make it possible with Modbus by using OpenPLC. Everything worked well apart from its limitation in the distance of data transmission or receipt. Thus, I thought of using the Lora module to overcome this weakness but still keep the Modbus function for some necessary cases. Some tough problems arise along with this idea were:
1. How to link Lora end node with OpenPLC when they are far away?
2. If Lora gateway takes the role of the station to intake data so how are we able to take them for handling in OpenPLC Editor?
I've been being stuck in both ways for days. How should I deal with this problem or are there anyway else for me to accomplish this? Someone who has experience with this could give me a suggestion?


texts:
I'm quite new to electronics and I'm having a hard time understanding the "pull-up resistor" principle. I have read a lot of articles about that, and I think I've got it but I'm not 100% sure so I have a question. In this article, after the first image, it says:

  When the momentary button is pressed it connects the I/O pin to Vcc and the microcontroller would register the input as a high.

But I don't get it. Where is VCC? From what I see, there is no power source on this schema, just a microcontroller wired to a button that are both wired to ground so how can there be any voltage at all in this circuit?


texts: Altium - How to Convey Pin-In-Paste Technology in Design

texts:
I am working on the first board design I've done with a connector that requires pin-in-paste (aka. "paste-in-hole") soldering. We are trying to expedite the manufacturing process so we are leaning away from wave soldering and hand soldering. How is pin-in-paste technology conveyed in an Altium PCB design? I can't imagine it is as simple as adding a polygon on the paste layer over the hole, as that does not convey how much is pushed into the hole. Does Altium have a feature for this already, or should it simply be called out in the mechanical fab drawing along with the board stackup and drill drawing?

Pin-in-paste/paste-in-hole technology:


texts: Output rectifying diode burning up in LED driver

texts:
I am trying to design an isolated LED driver with primary side sensing. I want my output voltage to be 48-56 V and the current to be 350 mA. The current and the voltage are controlled by current sense resistors and feedback resistors which have correct values according to my calculations.

The problem is that every time I start the circuit the LED panel lights up correctly but after some time the output rectifying diode (in my case ES2J) burns up. The ratings of the diode are up to the marks which is 1A forward current and 600V blocking voltage which should be more than enough for this application. I've tried a single diode and two diodes in parallel but the results are the same. What am I doing wrong here?


texts: Dangers of analog levels on digital PIC inputs?

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I'm intending to use a PIC16F675, because it's what I have laying around, for a very simple task that involves turning on or off LEDs in response to changes in a pair of photodiodes. It really could all be done with basic components, but I'd much rather spend my time writing Assembly than tuning transistors.
At any rate, the 16F675 does have an ADC, but I don't want to use that, because I want the chip to sleep and respond to "digital" interrupts instead. This would normally be pretty straightforward, just drop in a potentiometer and turn it until the chip sees a "high" value when the correct amount of light is hitting the photodiode.
However, the datasheet has a warning I've never seen before:

Analog levels on any pin that is defined as a digital input, may cause
the input buffer to consume more current than is specified.

This raises a few questions, most notably, what does this actually mean, and also why? According to the specs, 3V is well within its logic high range, but is this going to damage the chip by causing too much current draw? Or is it actually just a warning that the overall power consumption may go up compared to what the datasheet indicates? What if I instead wanted to connect a 3.3V digital output from another chip to it, would the same issue apply?


texts: Which fields of physics should I know in order to understand how diodes and transistors work?

texts: I want to learn principles of work of devices like diode, bipolar junction transistor and MOSFET. I tried to find answer on google and I found it, but problem is I don't understand branch of physics dealing with pn junction and other things. Which field of physics is neccessary to understand in order to be able to understand principle of work of devices I mentioned? Just to mention that I have not problems understanding mathematics behind it, I have problems with physics.


texts: STM6600 voltage divider on VCC for high voltage applications

texts: I'm evaluating the STM6600 on/off controller. My application has a 2-series LiPo battery with a voltage range of 6 to 8.4V, so I need to put a voltage divider before VCC as described in AN3271 (Chapter 12). The calculations for the divider provided in that document tell me I should use 26K and 34K resistors to get the recommended 100uA current through the divider.. However, when I use these values and press the power button, EN doesn't go high (I use an EN active high STM6600), instead VCC goes down from 3.4V to about 2.8V. When I use resistor values 10 times as low (2.6K / 3.4K) it works fine, but this means the standby time of my application becomes ten times as low. What can be the cause of this? I am evaluating on a breadboard with the STM6600 on a DFN to DIP breakout.


texts: Can I use serial port and RFID reader on Arduino Pro Mini?

texts: I have Arduino Pro Mini, HC-06 bluetooth module, and Mifare RC522 RFID reader. Bluetooth module connects to serial port, and RFID connects to SDA, SCK, MOSI, MISO, ground, reset, and 3.3V pins. I want to know if there might be a conflict between RFID reader and ATmega serial port. The reader will be used for reading and wiring cards. Bluetooth is there for monitoring.


texts: H-Bridge driver: external current sensing

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I'd like to use a DRV8870 H-Bridge driver for my circuit. According to datasheet it does not have a current sense output pin like its neighbors (DRV8701 etc.), but has ISEN pin for current sense resistor which internally connected to a current limiting circuit.

In my application I need to measure driver load current so could I just connect this ISEN pin to my MCU's ADC? Would it interfere with internal circuit? Do I need a buffer opamp here (I probably do not want that)?


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I am just trying to detect if an object is within 7-10 feet from my phone. What device would you recommend?
I don't care where it is or anything I just need a way of detecting that that device is at least 10 feet away from me...