texts:
Recently I've been into the idea of hooking up a Bluetooth receiver to my car stereo via my car radio's aux input. I got a Bluetooth receiver module from an old Bluetooth speaker that I had laying around. I disconnected to speaker and, not surprisingly, it was a mono speaker output on the circuit board. I took an aux cable, cut it open, wrapped the left and right together and soldered it to the positive output and soldered the ground wire to the negative output on the board. I plugged it into my car, connected to the module with my iPhone and played Spotify... It worked, but audio only came through the left side of the stereo car system.

My question is: Is there anyway to play the mono sound through both stereo speakers?


texts: I am looking to isolate an inverter when power from a generator is applied- debounce relay?

texts:
I have tried to find specific info on this scenario with no luck
The situation is this;
Off grid power system 12v battery store runs 12v lights etc. and an inverter for things difficult to run or convert.
I have a relay which energizes from the generator output and disconnects the inverter (so I'm not trying to push two unsynchronized ac signals in the same circuit)
The theory seems good, but I have managed to fry two inverters and I think this is due to a quick on/off switching of the relay as the generator powers down causing spikes and knocking out the output stages of the inverter.
It would be good to isolate the inverter completely, i.e 12v input side and ac output side- but I feel like a debouncing type circuit is needed on both relays
Any ideas/suggestions as to the simplest (and cheapest!) way of sorting this would be greatly appreciated.


texts: How can I control brightness of a CFL with a microcontroller?

texts: I'm new to electronics and just turned on and off appliances with an Arduino and relays. Now I also want to control the brightness of a CFL with an Arduino as I controlled the brightness of a LED. So what should I add between the Arduino and CFL to control brightness because I know that relays will just turn the light on and off?


texts: How to connect multiple capacitors in a series?

texts:
Lately, I have been trying to learn how capacitors work and I stumbled across a device called a "USB Killer." From the information I have gathered, the USB Killer uses 5v from the host to charge its capacitors then outputs 10v when they are full. Since the capacitors are being outputted at a higher voltage, then that means the circuit must be in a series. Maybe something like this:

However, this confuses me as after capacitor 3 has fully charged, it will not allow capacitor 2 to charge. Lets say that the 5v battery is somehow able to power all the capacitors to 5v, why would the circuit be at 10v+? Capacitors are meant to resist change so shouldn't the circuit stay at 5v max?

Note: This could all be completely wrong as this is just how I imagine the USB Killer's capacitors would be organized.


texts: Changing the frequency to an induction motor

texts:
I am currently having an issue with an induction motor driving a conveyor belt too fast.
It the connected to a Frequency inverter which is connected to a plc.
The inverter is sat to output 50 hz.  But i need it to run in 4 hz or less.

Would it do any harm running it so low?
Anything i should be aware of before i change it?

This is the ratings on the Motor :


texts: Capacitor put the wrong way by manufacturer - is this on purpose or is this a problem?

texts:
I am about to change the electrolytic capacitors of a Soviet Selena radio from 1988. I noticed that a few of the capacitors are put with the oposite polarization in respect to the board, e.g. this one (the plus side of the cap is opposite to the plus side on the board):

And here another 2 capacitors that I think of being put in the correct way, or at least they are put in the opposite way to the cap from the above image:

(original)

I found a tutorial in Russian discussing this, but I don't understand out of it if this is a problem and what you are supposed to do.

My questions:

Am I right that the show capacitor is put wrongly?
Is this done on purpose by the manufacturer? If yes, why?
When I insert the new capacitors should I put them as indicated on the board or should I stick to the orientation of the original
capacitors, even if it is wrong?

FYI, a top view of the whole radio:


texts: is there any non-written convention for pinout of JST connector (2-pin) when used for power supply or can I freely invert +/- wires based on my specific convience?


texts:
The board connected to power supply with 50-100m cable. There is C1, 1000uF 50V capacitor on input of board, next to power connector. Schematic of power circuit is below. I think it is for  bypass or decoupling. It is really big in physically, so i think the purpose of it and any different solution instead of 1000uF cap.

Also, 20-30 board can be connected in same power line sometimes. All boards are same. Has any impact on purpose of that cap?

Thanks.


texts: Why were the phase currents taken instead of voltage as inputs in the space vector moduation method?

texts: Why is it that the currents (ia,ib,ic) are taken as inputs, instead of voltages (va,vb,vc), when at the end, you need to create 3 phase stator voltages for the rotor to catch up with?


texts: In what pattern does the electrons get emitted from cathode in thermionic emission?

texts: We have structure with an cathode and filament at the center. A cylindrical shaped anode with cavities surrounds the cathode (fig 1). When the cathode get heated the electrons are emitted from cathode and move towards the anode. This is the thermionic emission. Here my question is, do the electrons emitted in any specific pattern or they are emitted uniformly around the cathode (fig 2)?


texts: Design question regarding high current wires running below PCB

texts:
I am working on a layout that will look similar (not final) to the illustration below. There are three high gauge wires (red) 3x230VAC passing directly below the PCB (isolation touching the PCB) that will carry up to 63A (worst case).

I have to get some signals across that section to switch several relays from my control logic side. I am worried that I will get into trouble due to coupling between my low voltage side and the high current wires.

The white rectangle is an electrical meter mounted on top of the PCB. The three phases "go in" on the bottom side and leave the meter at the top, thus returning below the PCB.

I would tend to keep the trace width as small as possible, route them on top (obviously) and keep the surrounding area (below the meter) completely free of copper.

Or would you say routing those traces above that area is a no-go?

I would appreciate a second opinion about this.

PS: The PCB shape and component placing is pretty final due to space, case and mounting limitations. One possibility could be using external wires. Another though was to mount a separate U shaped PCB with several centimeters space to the base PCB on top of it. That could bridge the gap right above the meter and keep some distance to the wires coming out there.


texts: Would the FCA47N60F work for a ZVS flyback driver?

texts:
I have built a few flyback drivers from 555 controlled to the ZVS. I always have one problem, the power transistors keep burning out. For the ZVS driver, I used the IRFP250 and keep having the problem of transistor failure over about 24 volts for the input. Here's a schematic of the ZVS.

I recently ordered some FCA47N60F 600 volt 47 amp MOSFETs on sale at electronic goldmine. Would these transistors work with the circuit, or are there specific transistor properties needed for the circuit?


texts:
1) I am using this DC barrel connector in my PCB and I want to make sure that when connecting a Center-positive power supply, my positive pin will be (1) and my two negatives will be (2) & (3), am I correct ?
2) my 2nd question is, do I need to connect the two -VE pins together in the pcb, despite they will be disconnected when the power supply is plugged in ?


texts:
On an old-school RJ11-based telephone system,  which of these statements is accurate:

1) Each wire contains a waveform constructed from the sounds detected by one party's handset

OR

2) One wire is the signal and the other is a ground wire

?

I say #1, but this homeless man I'm arguing with says #2.


texts:
I just received a battery charger in the mail, but I forgot to purchase the power supply. I was wondering if it was possible to use a transformer from an old lamp to supply the charger instead:

The charger takes 11-17 volts as input, 50 W as max charge and charge current of 0.1A to 6A  [Link]

The transformer specification are:

My textbook says that the current in the primary circuit is related to the current in the secondary by:

$$
I_{1rms} = \frac{N_2}{N_1} I_{2rms}
$$

So N2/N1 must be:
$$
V_{2rms} = \frac{N2}{N1} V_{1rms} => \frac{N_2}{N_1} = \frac{V_{2rms}}{V_{1rms}} = \frac{12V}{230V} = \frac{6}{115}
$$

Is it possible to increase the load resistance so that I can draw 6A (the maximum of the charger) through the transformer?

$$
I_{1rms} = \frac{6}{115} 6A = 0.31 A
$$


texts: Relationship of antenna size to gain and directivity

texts:
This question is derived from certain answers I received for a previous question I posted.

Case :  Let's say I have two GSM antennas of the exact same shape, design and material. The only difference is that one is 10 times larger in size than the other.

Question : What sort of impact would this have in the second antenna's directivity & gain?


texts:
(Sorry, I am a newbie but here I go..)

I have a 5W 12V solar panel stepping down to 5V. The current then goes through a charger that already regulates to the required voltage for the battery. This then goes out to a step up from 3.7V-4.2V to 5V. Then this goes to a raspberry pi zero. I would like it so that whenever the solar panel doesn't produce more than 100mA to the charger then the current will be stopped.


texts:
I have an OSRAM 85W 450nnm laser array.
It's essentially a large 'chip' with 24 integrated laser diodes (break it down they're approx 3.5W diodes each.) The Chinese source I purchased it from also sold me a "laser driver" which I've quickly determined is just a boost converter of some kind with no current control whatsoever. I've already designed and produced a circuit (with current and case temperature feedback data) which has the array in a series configuration, meaning you could imagine the diode as one big diode with a compliance voltage of 105 to 110V and 2.5A maximum. The cooling part of the equation has been solved, powering the diode in the manner described definitely works - quite well infact.
I happen to have 3 N-channel 200V 30A MOSFETs (NTB30N200T4G) from an old project, so if they're usable in the design even better.
I've two trains of thought for this:

DC-DC approach, start with a 12V or 24V SLA battery or similar high current DC source and create a boost circuit to attain 110V. Then I build a laser driver fed by the power source.

AC 240V through a custom made transformer, nice and simple 1:2 ratio for a 120V output, bridge rectifier and DC cleanup then voila I have my 110V with plenty of current to spare. Then regulate voltage and current (MOSFETs might come in handy here?) to construct my laser driver circuit.

Does anyone with more experience with power supply design or more specifically laser power supply design have any input, ideas?

Partially answered my own question for those reading who may be interested in the solution i've found. Datasheet for diode below for further context:

Sourced a 300VAC Toroidal 240 primary -> 55V - 55V secondary transformer. With the taps joined provides an ideal 110VAC RMS output. This will be used to form a basic power supply with filtering to clean up DC, buck converter to reduce voltage to desired range. See datasheet for min (20.7V) to max (28.8V) forward voltage per channel, with all 4 channels in series this yields a requirement of lower bound 82.8VDC up to 115.2VDC (Perhaps this explains my earlier desire for a 110VDC supply..).
Datasheet for toroidal transformer: https://au.rs-online.com/web/p/toroidal-transformers/2238241/
My question remaining is: what is an ideal circuit topology for voltage and current regulation (110VAC RMS, 2.73A)?


texts: Reverse Polarity Protection: Is this method safe!

texts:
Consider the above circuit. The N-channel MOSFET has been used as a low side switch to provide reverse polarity protection. A capacitor charges to the 12V supply(battery) voltage and subsequently the supply terminals are reversed. Since the capacitor will hold its charge for a certain period of time, it is therefore able to keep the MOSFET Vgs well above the minimum threshold voltage of 2.8V. As such on reversal, the capacitor discharges and settles its voltage to 2.8V after which the MOSFET turns off completely thereby disconnecting the circuit.

Well the above case seems to be impractical, but consider a situation where a startup delay of few seconds is given, the user might unknowingly reverse the polarity. As circuits contain innumerable capacitor and magnetic components that will be able to keep the mosfet on till their energy collapses in the biasing and other circuit loads, for that period the circuit seems to be in conduction mode even under reverse polarity.

Can anyone explain what will be the effect on vulnerable components that are a part of such a circuit? Also is there any way to mitigate this effect?


texts: What is the metallic coating on these stranded copper wires?

texts:
The 5-colored wires's strands looks like aluminium, but it is basically copper wire at centre, with a thin conductive coating (my teacher shown it to me) of silvery-color, so that the copper doesn't get weathered .

If the rubbery insulator removed, and the metallic strands  Scrapped with a knife or a shaving-blade, the silvery-colored layer removed, and the red, copper-interior comes out.

Now, i want to know, what substance(s) used in this coating?

These wires sold as 5-color electronic wire (for low voltages). I've given a scale also.  Since nothing is printed on the insulator, and i buy in retail amount (1 or 2 yard) from a large spool, i've also no clue to the datasheet right now.  (however, these wires are not  very costly (around Rs. 10 per yard)).

The upper strands (with respect to photo) of the upper, yellow wire is scrapped with a blade and it shows red, coppery colour inside. the blue-one shown as reference or control.


texts:
The board which is made with Atmega operates on battery, it should turn on every 6 hours and log some data, then go back to deep sleep to save battery consumption. Atmega32 is used and not Atiny because of complexity of tasks and sensors connected to the circuit.

What I have found so far, is that I can keep track of time using an RTC IC.

I've read datasheets of some RTC IC's but they don't provide any such capability as generating a signal for Atmega's external interrupt at specific intervals, so it can wake up from deep sleep. (Something similar to cron-task in *nix systems is needed, if you are familiar with it.)

And of course search terms like "Atmega scheduled task" and alike did not bring up anything.

How can I efficiently (in terms of power consumption) wake Atmega up from deep sleep periodically?


texts: Can I rewire a 240 V 3 phase steamer to a 240 V 1-2 phase?

texts:
I have this steamer unit that came in as 240 V, 3 phase that I am trying to adapt to a 1 (2) phase household. The unit needs 60 A and generate 9 kW.

As per the manufacturer, and the below diagrams, I need to switch the wires from figure 12 to figure 11.

I am trying to have a confirmation from experts if this actually makes sense.


texts:
Why are some electronic devices rated for volts and some current?  Isn't total wattage what matters?  Most seem to be rated for amps, and Tesla famously ran hundreds of thousands of volts through himself, which certainly implies that current is what matters.

For instance, the Raspberry Pi's GPIO pins are 3.3V and 5V.  Why are these voltage-rated and not amperage-rated?


texts: tri-rail power supply from cheap buck converters

texts:
I'm looking to build a 3 rail regulated supply (+5v, +-12v) and I've got a bunch of cheap but functional buck converts from aliexpress. I'm wondering if I can run these off a single AC-DC converter (wall wart, etc) and get a common-ground 3 rail supply from this?

I'm thinking something like:

simulate this circuit – Schematic created using CircuitLab

Will that work? Or do I need to introduce a multi-tap transformer or similar solution? The buck converters are these.


texts: How does the inductor have an initial condition in this circuit?

texts: If the initial current in the inductor is \$i(0^+)= 0 A \$ why is it that when the switch occurs the initial voltage in the inductor is \$ V_L(0^+)=121.4 V\$


texts:
Please fix my tags.

I'm making a series of interactive puzzles for use in classrooms. One of them is an equation graphing. It will have a grid of screws stuck into wood, with the axis drawn on. Students will wrap flexible wire around the screws to complete the circuit. When the circuit is completed the latch should fire allowing a side drawer to be opened. The teacher can configure it with alligator clips inside the box. The other puzzles follow this same concept: buttons, switches, etc complete the circuit allowing power to pass to the latch. That's the general idea, here's the details:

The latch should discontinue the circuit after it opens, so that that current is only ever flowing in that moment. It will run on a few small batteries, so using power continuously to keep it open or closed is undesirable. It's fine if it has to be manually reset, like some kind of electric mouse trap. My question is what would this be called, so I can search for it on amazon ?


texts: Moving Door on Electrical Box Alters Signal

texts:
I have an experimental setup that I am building to, among other things, measure the flow rate of water through a tube. The flow rate is measured by a sensor that is powered by a 24 VDC source and provides a 4-20 mA DC signal. I am currently seeing an interesting issue where there is some amount of noise in the signal, but when I open the door of the electrical box by about an inch (the point to which it opens naturally when unlocked), the amount of noise drops by about a factor of 2.

Possibly relevant information (I am not an electrical engineer, so some of this may be irrelevant):

The electrical box is made of painted stainless steel
The 24 VDC power supply has a maximum current of 2.1 A (so a power rating of 50 W)
The flow rate signal is generated by an FTI LinearLink LA-5-C-MAF
The current is being detected by a NI cDAQ 9154 with a NI 9203 current card
I am using DIN blocks to make my electrical connections

This is what the electrical box looks like

What could be causing the change in noise when the door on the electrical box is opened or closed?


texts: Is Axial Gap (pancake) motor better for servo drive applications?

texts:
I heard from someone that axial gap /pancake motors (lynch or etek) are better for servo control (speed and position) than standard radial flux DC motors. Both motors are brushed type.

I don't really understand the physics behind this claim , although I know how each one operate.

So can anyone please state if it is really better, equal or worse motor technology for servo drive, and why?


texts: Is it possible to add automatically not installed libraries in Altium?

texts:
As the title says: Is it possible to add automatically not installed libraries in Altium ?

After I reinstall Altium all the libraries I have added are not there I have to add them one by one again looking through every component I have.

Is any way to force Altium to analyze Library directory and search for missing libraries in my project?


texts: Solar charging "12" volt nimh battery pack

texts: So, I have 3 parallel 8-battery packs of nimh batteries wired in series - a total of 24 AA batteries.  One battery is 1300 mah so I assume this should give me a total of 3900 mah.  This gives me 9.6 volts or 11 volts at full charge for a voltage of 1.375 for a single battery.  Can I charge this connected directly to a trickle charge 12 volt 5 watt solar panel with a current of .28 amps (280 ma) since this is lower than the 10% which would be 390 ma?


texts:
I just ordered an electronics hobbyist kit. It comes with a breadboard and a bunch of other components. Looking forward to work on my first project.

In my setup, an external device is connected to the PC via USB. One of the pins on the USB provides +5V to the device.

I need to keep the external device alive even when the PC is not on. Essentially, I need a battery backup circuit that kicks in as soon as the PC power is turned off.

Note that the external device can even take +1V to be kept alive. Ideally, I would like to send minimum current in order to keep the battery alive for a longer time.

Wondering if you can point me in the right direction. Is there even a name for such a circuit? Regards.


texts: Amplitude and phase spectra of fourier series

texts:
If I have even and periodic signal \$x(t)\$ that has cosine fourier series

$$ x(t)\sim\underbrace{\frac 12}_{a_0}+\sum_{n=1}^{\infty} \underbrace{\left(\frac{6\cos \left(\frac{n\pi }{3}\right)-6\cos \left(\frac{2n\pi }{3}\right)}{n^2 \pi^2} \right)}_{a_n} \cos \left(\frac{n\pi t}{3}\right)$$

because for even function my \$ b_n=0 \$ coefficient vanishes so \$ C_n = a_n \$

If I want to construct amplitude spectra I plot \$a_n\$ with \$n=0, \pm 1\, \pm 2\,...,\$ right? Like this?
$$\begin{array}{c|c}
n & a_n   \\ \hline
0 & 0.5  \\ \hline
\pm1 & 0.61  \\  \hline
\pm2& 0 \\ \hline
\pm3& 0.14
\end{array}$$

But how about the phase spectra. Phase or \$ \theta=\arg(C_n)=\frac{\operatorname{Im(C_n)}}{\operatorname{Re}(C_n)} =\arctan \frac {-b_n}{a_n} \$. But in my case there is no \$b_n\$. Doesn't my fourier serie have phase spectra?


texts: Multiple baud rate slaves to a single I2C Master

texts:
Can we connect multiple slaves with different baud rates to a master. For example, I am having a temperate sensor which would work at 50kbps and port expander at 400 kbps, Can these two slaves connect to my master(microcontroller) on the same I2C?
If you can add anything more why it should not be a problem, it would help


texts: Replacement for IDT70825S/L: Sequential Access / Random Access Memory

texts: I am building a circuit which needs to sequentially buffer pixels from a VGA signal at 25MHz (using TI's TVP7002) into RAM, and then needs to access pixels out of order given addresses. It looks like there used to be a chip which would allow exactly that (datasheet), but it is now obsolete. I am having a lot of trouble finding a suitable replacement; Is there one, and if not how can I duplicate this type of functionality?


texts: I try to drive a galvo-mirror with a dual OpAmp AD8532. No spec sheet for the mirror, but it is about 16 Ohm and takes about 50mA at 2Vp-p, if I measured correctly. The OpAmp starts malfunctioning after a while. I could not determine when/what causes it to malfunction, but it stops to provide all the required power. It seems like it gets fried up a little. The only thing I could think of right now, are the reversed currents caused by induction. I will try to add reversed diode to each of the outputs, but I am not sure if the problem will go away. Do not want to burn more OpAmps. Any suggestions what else should be added to the circuit below, to make it right?


texts:
Suppose I have a 1:1 transformer, just to keep things simple. The primary winding is connected to mains voltage (±170V peaks), with a grounded neutral. The secondary winding has an arbitrary load.

If we measured the voltage across the secondary winding, it would be a 120V RMS sin wave. So that's the potential difference.

But what determines the absolute potential of each terminal on the secondary winding? In other words, what will the potential be relative to ground? Or is the absolute potential not referenced to ground at all, and instead referenced to the local electric field in the transformer?


texts: what is causing this ring effect on my MOSFET testing circuit and how would I be able to calculate the MOSFET power losses?

texts:
So I have the following circuit
This is the data sheet for the MOSFET enter link description here
Using equations, I worked out what my Rgate to be 2.36 ohms.
where Rtest was a 470ohm ceramic block resistor (due to it getting quite hot when turned on)
Connecting the oscillator, I see that I have this ring effect on the square wave as shown here:

Just wondering what the cause of this ring effect is or maybe a little detail on what it is and how to fix it? I increased the resistor value to 47 ohms which does lower the effect but why?

Also any ideas how I can calculate the Power loss of the MOSFET?


texts: How to design 4-bit comparator using the below described logic?

texts:
Suppose we have 2 4-bit binary number represented as:

A3A2A1A0
B3B2B1B0

We use 1-bit comparator for it.

Comparison starts from MSB.

Compare A3 with B3 using above 1-bit comparator. If A=B give high output (logic 1) then only it compare other bits. If A=B is false (logic 0) then the final answer of comparison is same as the output of 1-bit comparator.
If previous A=B is logic 1 (true) then it compare using 1 bit comparator and again the same consequences.

Is it possible to design 4-bit comparator using gates with above logic? If, yes then how can it be?

As a find comparator in Google which is drawn using K-Map.


texts: Intel i7 Core CPU numbers on the front side

texts:
What is the numer at the fourth row on the front side of Intel i7 CPU? (pictured)

I saw two Intel CPUs in the store described as "Core i7-6700" but have slightly different prices (both OEMs). Only the difference I found is the numbers on the front side.

P.S. I'm already guessing it is kind of a serial number but not sure.


texts: Low-voltage cascode current mirror biasing circuit

texts:
On the left is a low voltage cascode current mirror and on the right is a circuit whose left branch generates \$V_b\$ for the mirror. Razavi (Design of Analog CMOS Integrated Circuits 2nd edition, page 144) says we want \$V_b\$ = \$(V_{gs,1}-V_{th})+V_{gs,0}\$, so we want a bias circuit which generates a gate-source voltage and an overdrive, which makes sense. The goal is for \$V_b\$ to force M1 to be near the edge of saturation for the most headroom.
Razavi says the biasing circuit on the right does this since "the diode-connected transistor M7 provides the necessary \$V_{GS}\$ and M6 creates a \$V_{DS}\$ equal to the required overdrive." I'm not sure why this is.
I see that by definition \$V_b\$ = \$V_{gs,7}+V_{ds,6}\$. Since M7 is diode-connected, it generates a gate-source voltage.
(Edit): I realized I made a mistake since M6 is actually in triode and not saturation, so the drop across it needs to be matched to the overdrive of M1. How is this done?


texts:
Could someone please tell me the difference between analog ground and digital ground on pcb?

It would be easier if you explained it with a example!


texts: NXP PCA9615 I2C differential buffer - failure on SCL line

texts:
I am using the PCA9615 part to extend an I2C bus. The PCA9615 converts I2C to a differential bus.

PCA9615  https://www.nxp.com/docs/en/data-sheet/PCA9615.pdf

There is a control box and a remote slave box. There are existing buffers in each box. (Analog Devices ADuM1250  I2C Isolators) The slave box normally would be within arm's reach of the control box. A short cable joined the two. This worked well but now we need to have a solution for larger distances between the control and slave box. I used the NXP PCA9615 to extend the distance.

What I have is the following.

Control I2C <-> ADuM1250 <--> PCA9615 <======> PCA9615 <--> ADuM1250 <-> Slave I2C

3.3v  ________| isolated |____________________________________________ 5 volt

The 3.3v side of the ADuM1250 is isolated from the right side. Everything to the right of that is powered from +5v from the slave box. I am using a cat 5 cable to join the two PCA9615. +5v and common are supplied (from the slave box) through the four wires of the cat 5 cable. The other four are for the differential SDA and SCL lines.

The problem I have is that the SCL line of the left PCA9615 is failing. A permanent low. With an Ohm meter I get 340 Ohms to ground, with the chip out of the circuit and not powered. With power applied to the failed board,(no other modules connected) the SCL line is low. This has happened to two different modules at the beta site. We are trying to schedule a trip to the site.

Has anyone been using this chip in a product? Any similar failures? The failure has been on the SCL line but I can't say it is only with that pin. The problem is on the single ended side and not the differential line extension.

The schematic shows a NLSX4373 buffer in the slave box. That was wrong. It really is a ADuM1250, the same part as in the control box, but not isolated.

Some further information. I said earlier that I measure 340 Ohms to ground on the damaged SCL pin. Then the circuit is powered the resistance will sink current from the pull up resistors. The voltage seen at the pin is 2 volts on one board, and 2.7 volts on the second board.

Grounding that SCL line with pass the low through to the differential side. And if I generate a low on the differential side, that low gets passed through to the single ended SCL line and it sinks the current on that side. So the failure has the affect of putting a ~300 Ohm resistance to ground/common. Still a fault but the signals are being passed through.


texts:
Here's an image of my Digilent Coolrunner II development kit:

Those connectors on the backside are 6x2, female, and seem to be on .1" pitch.  Are these standard, and where could I buy the male counterparts?  Much obliged.  Just a few words to search on is all I need. '6x2 electronic connector' didn't cut it.


texts: Placing a QFP 52 footprint on the PCB in KiCAD

texts:
I'm new to PCB design and want to make an adapter board from an SMD QFP52 package to DIP. Apparently QFP52 is not very common so I cannot find it in the library.

There appears to be no pre-existing footprint for this in the standard library in KiCad.

But is there an easy way of specifying that this is quad package, and the size is such and such and the pin size is this and pin spacing is that and it gives me a footprint? Or do I have to manually add the pads and align them?

I thought of going through the process of create a schematic first, generate a net list, generate the footprints which as far as I understand is a common workflow. But there's no 52 pin component in the schematic library and also this looks like an overkill for my simple breakout board.


texts: Parallel Primary Coils of Two Different Transformers

texts:
Attached below please find a figure1 which is what I want to achieve (i.e. split a balanced audio line into two isolated outputs in a passive manner). The transformers that I currently have are 10 kΩ:10 kΩ with a 550 Ω primary and secondary resistances.

If the transformer is 10 kΩ:10 kΩ, this means that for maximum power output a 10 kΩ load must be used at the secondary and at the same time the primary should not be loaded? For example an output source with an output impedance of 10 kΩ will definitely load the primary of the transformer.

If I parallel the inputs of the two transformers as seen in the figure, will the effective impedance become 5 kΩ?

If the effective primary impedance becomes 5 kΩ, this means that the secondary output impedance of each transformer is now 5 kΩ?

If the effective primary impedance becomes 5 kΩ, is maximum power transfer still achieved?

Thank you!


texts:
I've installed Proteus 8 and began to work with it. I've built a primitive circuit with oscilloscope. At first time visualization window (with graph of signal) was being got. I closed this window and stopped the simulation. But in the next time this window didn't open.

I try to solve this problem with the help of Google and found the answer: "You must to click right button of mouse at oscilloscope and find "Digital Oscilloscope" and problem will be solved". But it actually works in another versions of Proteus. I didn't find this in Proteus 8.

How to solve this problem in Proteus 8?


texts: What does an AC signal look like when it is grounded with a DC signal?

texts:
Sorry if something doesn't make sense, I am not an electronic engineer, if I need to clarify something, please tell me to :)
I am upgrading the light on my motorcycle to an LED light.
My problem is that the power for the light comes directly from the generator unrectified (I think.) This makes the light flicker at low RPM.
In the manual, I can see that the black wire from the light socket (ground) goes to the same wire as the negative terminal of the DC circuit.
Does anyone know if the signal at the headlight will be AC, going between a negative voltage and a positive voltage, or an alternating DC signal, since the ground wire goes to the ground in a DC circuit?
I need to know this because if the signal is a DC signal, I won't need to rectify it first, and since my full-bridge rectifiers have a high voltage drop, it would be nice if I could exclude them. :)
I have tried to draw on the wiring diagram, where the light is connected to both the AC side and the DC side.


texts: Need ideas for 5->3.3 voltage conversion for micro SD cards

texts:
I'm thinking about connecting a micro SD card to my ATmega162 perfboard, but for that I need 3.3 V source which can provide up to 100 mA.

Most obvious option would be to run the whole board at 3.3 V because all components seem to be working at 3.3 V, but I'd like to keep the 5 V input voltage.

Next option and the most obvious one would be to use voltage divider. The downsides of that would be need for high precision resistors, bad stability, space taken and power consumption.

Another option would be to use a 3.3 V regulator. After checking which regulators I can easily obtain, choice comes down to LF33CV or LP2950CZ-3.0.

The LF33CV fits from the electrical side with its dropout voltage of 0.45 V and very low power consumption. It can also provide up to 500 mA, which should be enough for most micro SD cards. I'd need two capacitors, one 0.1 µF on input and one 10 µF at output. On the other hand, the regulator is TO-220 and I'd like to save as much space as possible on the board.

The LP2950CZ-3.0 is under just acceptable category from the electrical point of view. It has dropout voltage of 0.38 V and is guaranteed to provide up to 100 mA, which is exactly the amount I expect to need. On the other hand it's much smaller and comes in TO-92 package. It also only needs one 3.3 µF capacitor at its output in order to work properly.


texts:
I'm looking into driving nixies and i came across this multiplexing circuit

I am a little bit confused about the chosen voltages. The 200v line I would assume is to meet the required strike voltage, if this is the case could it be reduced to the average 170v strike voltage?

My assumption is that the 110v line is to maintain the voltage across the tube. But that is considerably lower than the maintenance voltage for the zm1000. So what is the purpose of this rail?

Finally on the cathode side. It's connected to 75v then pulled down to the 0v potential, is 75v an arbitrary voltage, perhaps what was available from the supply? Why was this chosen?


texts:
I'm working on a 4x4 robot that is supposed to carry stuff total_mass=100kg (including the robot).
the robot should have average speed 20km/h
assume that inclination_angle=0 acceleration=0.5m/s^2 wheel_diameter=0.25m
direct drive (no gears) 4 motors 4 wheels

What kind of DC motors should i use (brushed or brushless or other)?
what are their properties? (torque, rpm ... combination)

I'm not so good at math and conversions.


texts:
There are no spare positive/negative charge carriers on the metal side of the diode, so the spare positive/negative charge carriers on the semiconductor side can not diffuse into the metal and recombine with spare negative/positive charge carriers. Therefore no potential barrier will be formed by ions on each side.

So how does a Schottky diode work?


texts: Charasteristic curves for a transistor working in a common emitter configuration

texts:
Configuration
According to my text book,

When we use a transistor as an amplifier, there  generally 2
resistors, one is input resister(R in) and the other is output
resister(R out). Normally these resistors are connecting as R out is
relatively greater than the R in.

I can't understand the reason for Why the R out should greater than the R in and what is the expectation of that?

Characteristic Curves
Output Characteristic

For a concerned IB at the start of the curve, it has a speedy variation (relatively high gradient) and after a while the variation is slow and becoming linear(less gradient).

What is the reason for have two gradients? Starting have a speed variation and then slow gradient... I tried to concentrate it with the Ohm's law but couldn't.(According to the ohm's law the R out should different at the two situations.)

Transfer Charasteristic

I can't understand the reason of why there is a saturated region after the activated region. Why does the activated region can't to be continue.

I expect  answers with theoretical descriptions and a deep view of the structure of the transistor.


texts: LM35 output varies when connected to microcontroller

texts:
I am using an ATmega16A in my project. I have connected the Vref pin to Vcc (5Volts). I have connected my ADC input pin A1 (ADC1) to output of LM35 IC (output connected to RC damper).

Now the problem I am facing is when I have no microcontroller in place it measures perfect ~0.3 volts (room temperature) at the LM35 output pin but after soldering the microcontroller this pin voltage rises to ~2.5 volts (provided LM35 is at same room temperature). Also the ADC reading read by my software is higher and corresponds to 2.5 V and not 0.3 volts so what could be wrong?


texts: How to solder on a new USB plug/connector

texts:
I bought a USB WiFi card, but then the metal part broke and I had to take it off. I only have the board now and it is too small to fit into a USB port. Where can I find a new USB head/plug (the silver part used to plug it into the USB ports, sorry I cannot find a name anywhere). And how would I go about soldering on this new head?

Refer to the picture of the memory stick if you do not understand what I mean with the silver part

Thanks in advance


texts:
I have a TFT 2.2 inch Display. like this:

Its controller is ILI9341. I ported it to my MCU and everythings work fine. one of the most important things in using a display is Gamma. when you would use a display you have to adjust it because it effects on the brightness. I think I have to adjust the  Gamma of my display. the value that currently I use for Gamma is 0x01. I think that's the default value. when I looked at the datasheet. unfortunately as I expected that's weird to me. :(

also I have searched for finding a solution but none of the results was good. I have converted some part of the datasheet to jpeg for you that are about Gamma. links:

Image1
Image2
Image3
Image4
Image5

How can I adjust the Gamma with these datas?
there is an equation, When should I use it? how can I use it?
What's positive and negative Gamma?

Added1: For supply I use 5V for Vcc and 3.3V exactly.

Added2: two pictures of my LCD when show me 0x001F (blue) color in 16bit (65,536 colors) mode.


texts: Why are shunt resistors in BLDC motor drivers placed betweent MOSFETs and ground and not MOSFETs and the motor?

texts:
In all projects like that I found and in the application note of DRV8302 the shunt resistors for current measurement are placed on the ground connection of the transistors. Why not place them in between them and the motor, so that they could be used to precisely measure current in both ways?

A followup question:
When using a hall-based current sensor does it make sense to place it on the motor side? It is galvanically isolated so ground referencing shouldn't make a difference.


texts:
Can a relatively low resolution DAC (say 12-bits) be used as a precision voltage reference with stability much better than the \$V_{max} \times 2^{-12}\$. If a certain DAC is set to a particular digital code for all time, is there a specification that gives me the noise voltage of this source?

For example the AD5681 has 16.5μVpp output noise listed for all models from 12 to 16 bits. For 5V full scale on the 12bit ADC the LSB is 1.2mV. Does this guarantee that I can set any voltage I like in 1.2mV step but that the output will be stable within 16.5μVpp? Assume a high-impedance load.


texts:
I wish to understand more on power parameter needed to design the power supply of audio amplifier.

Which power parameter should we use when designing the SMPS? Is it peak power or rated power?

Lets take an example as below:

SMPS topology:

Flyback quasi-resonant type

Assume Class-D audio amplifier requirement as below:

Peak power : 250W (in short period, less than 5s)
Rated power : 50W
Speaker : 8 ohm

This is example I found on internet

Based on above example, the BTL output is 50W. This 50W is based on RMS value. Based on that, the minimum power supply voltage is 33.4V.

But if we use peak BTL output 250W, this will give minimum power supply voltage around ~70V.

Based on above calculation, I conclude as below:

If use rated power, the minimum voltage power supply is ~33.4V
If use peak power, the minimum voltage power supply is ~70.0V

Based on that, which voltage should I use for my power supply output voltage? Is it 33.4V or 70.0V?


texts:
I wanted to know if it's practically possible to use inductors the same way we use capacitors , in the sense of charging it using a charging circuit then discharge in another circuit.

I thought it could be possible but then i read on the web that when an inductor is disconnected the magnetic field starts collapsing inducing a very high voltage, wouldn't this voltage breaks down any transistors used in the switching from the charging to the discharging circuit? If i understand this correctly, this only happens when there is no way for the current to go so voltage builds up, but then again there is a small split of second between the switching between the 2 circuits, will that cause such a problem?

Edit:

If I used this circuit to charge and discharge the inductor, will there be any voltage spikes?


texts:
I'm working on a home automation/security system (Only in my head at this point) and stumbled upon RS-485 transceivers. using RS-485 with PoE seems to be like a great idea to keep cords to a minimum.

In a Cat5 cable, I'll have 4 twisted pairs, I'll need two conductors for the RS-485 bus, but I was hoping to use the remaining 3 pairs for a modified Power over Ethernet setup.

Can I run a long Cat5 and use 1 pair for a RS-485 bus, and the remaining 3 for a PoE bus?  So I'll inject 48V DC into the other 3 pairs, so at each node I'll have 2 data lines, and combine 3 grounds and 3 VCCs.

I'm going to use Arduino's that hopefully will be drawing very little current (under 10ma each is my estimation) but can you bus PoE the same way that RS-485 lets you?


texts: Powering a raspberry Pi using an ESC (Electronic Speed Controller)

texts:
I'm working on a quadcopter project using Motors/ESCs, an Arduino DUE and a Raspberry Pi.

I have 4 motors and 4 of these Opto ESCs.

At the moment I have the raspberry Pi plugged into the mains socket, with a USB connected to the Arduino to power it. I also have a 3S Lipo battery powering the ESC/Motors using one this power distribution board.

The red cable from the ESCs/Power distribution board isn't connected to anything.

What I'm wondering - is it possible to use this red cable to provide power to the raspberry pi in place of the mains so that the whole system would be powered by the Lipo battery.


texts: Possible to use FPGA to emulate TTL logic ICs in existing circuit?

texts:
Is it possible to use an FPGA to emulate and 'replace' a damaged 7 series logic chip on an existing circuit board?

For example, if I have a VCR or receiver that has a damaged 7 series logic IC, is it possible to remove the damaged chip, emulate its logic on my Cyclone IV, then connect my FPGA's pins to the pins on the PCB and have a working device again?

I would like to know if this is possible despite its impracticability. Hypothetical scenario, I would like to know if this is possible if you wanted. Google hasn't turned up any relevant information


texts: How does Synchronous Transmission provide synchronized clocks?

texts:
I was reading a textbook which says:
in synchronous transmission, the bit stream is combined into longer “frames,” which may contain multiple bytes. Each byte, however, is introduced onto the transmission link without a gap between it and the next one.

as the picture below shows:

and I was also told in Synchronous Transmission, the sender and receiver should have synchronized clocks before data transmission.

so how does clock get synchronized before data transmission? all I can see i the picture is, the sender sends many bits in frame, how could it synchronize the clock?


texts: How does input voltage ripple affect output voltage of linear regulator?

texts:
The problem starts with my 3D printer which is powered by a 12V SMPS. When it drives a heavy load such as heated base and hot end, it causes a ripple on the 12V rail. Also it affects the 5V rail with the same ripple as the image shows.
Note: My printer uses Ramp 1.4 with Arduino Mega2560

Note:
Chanel A is 5V from Arduino Mega, Chanel B is 12V from PSU.
For ramp1.4 , For Arduino Mega 2560
What I want to know is:

How does this happen? As I know, voltage regulator should regulate all above 5V+(dropout voltage), so it should be a flat 5V line.
How to fix or prevent this? (Do I need to add some component filter or change regulator ICs?)


texts:
I just picked up a face shield for in person labs and was wondering if it is ESD safe. In this scenario I'd be wearing a ESD strap, but it seems like the plastic is isolated with foam and an elastic strap. Attached is a picture of the shield and it's claim of "Anti-Static". I'm not sure if anti-static refers to dissipative or the flat prevention of an electrical charge. Below are pictures of the face shield in question.

[3


texts:
I have an RFID simulation that has an antenna, which generated power is 2 mT in a certain range.

If an RFID tag has a sensitivity of -10 dBm, can I use that information to evaluate if the tag will be powered on for example in the range where the magnetic field is 2 mT?


texts: Have I understood what Arduino is correctly?

texts:
Just before I go out and buy an Arduino starter kit, can someone confirm I understand what it is?

As I understand it, I can use a simulator to create the behaviour I want. Once I'm happy with the code I compile it, connect the Arduino Uno to my computer (with a "blank chip attached) and flash the chip. Then I can remove the chip, and put it on a breadboard, or Matrix Strip or suchlike and work it into a project.

Is that right?


texts:
A kWh meter (electromechanical induction meter) is installed in front of each room in our apartment to measure the electricity usage of each room. Each room has its own breaker box to set up the 110-V (hot wire & neutral) and 220-V (two hot wires) electricity. Before the breaker box is a single-phase 2-wire meter with two hot wires going in (from the 220-V city electricity) and out (to the breaker box). The city electricity neutral line is connected directly to the ground bar in the breaker box without passing the meter.

My question is: how does the meter measure the current when a 110-V home appliance is using the electricity? Since the current would alternate between a hot wire and the neutral wire, the other hot wire would be left unused.
Can a 2-wire 220-V meter measure the kWh value correctly when a 110-V home appliance is running? Should we replace it with a 3-wire meter?


texts: What is the minimum voltage required to operate an AVR MCU at 8Mhz clock speed?

texts: I want to run an AVR off the internal 8Mhz RC oscillator without any prescaller and want to make sure I have enough voltage for proper operation.


texts: LM317 vs series diode (1N4007) as voltage regulator?

texts:
I am using the SIM900A GSM module which requires 3.2V to 4.8V with max current draw of 2A.

In my board, I have a 5V, 3A supply which will be used to power the SIM900A.

Generally, in my search I found 2 ways to power it:

Use a LM317 regulator to produce around 3.9-4V
Just simply use a high current series diode (like the 1N4007, with forward voltage = 0.6v) to produce 5V-0.6V = 4.4V

My question is Is there any advantage of 1 over 2 (or disadvantage of 2 over 1 for that matter) as 2. is much simpler and cheaper.

I want to use 2 if there shouldn't be any major disadvantage.

I have seen both in commercial Chinese SIM900A modules, so I guess there should not be any problem with 2. But then why use the LM317?

Thanks.


texts: How overvoltaging makes graphic processing unit operate faster?

texts:
My teacher told me that we are trying to make transistors smaller so that they require less electricity to operate, hence make them faster (because changing form 1 signal to 0 or vice versa need less energy, or so he said). Meanwhile, cryptocurrency miners and gamers overvoltage their GPUs for better performances. Why are 2 points contradict each others? What's happening under the hood when we overvoltage GPUs for better performance?

P/s: I had some thought whether i should ask this in SuperUser or ElectricalEngineering before making up my mind and ask this question here.


texts: I'm using a 3.3V output from a pmod port on a digilent Basys3 board. I have the circuit working IRL but I am required to provide a diagram and simulation. I'm not proficient in LTSpice and not 100% confident with MOSFETs. In my circuit, I'm using an IRF2708 MOSFET. The goal is to show that when the 3.3V is low, the 12V will power the electromagnet, and when it is high the magnet will be off. Resistor 3 is a 15ohm 25W power resistor. The inductor and resistor are to represent the electromagnet. I'm wondering if anyone could point out where I have made a mistake, thank you.


texts: How might I increase incircuit voltage from 2.5 DCV to 3 DCV

texts:
I'll cut to the chase, an about me is at the bottom of this post...

I have a standard NE555P fader circuit powered via a 1.2V battery boosted by a QX5252 with 220µH axial inductor (which according to the datasheet should be giving output of 3.5 DCV @ 15 mA to the NE555P). The net max output from the 555 circuit is about 2.5 DCV after an NPN boost, which is OK for my red, yellow & green LEDs but only dimly lights up Blue LEDs.

I wish to boost final power output from the NE555P circuit of 2.5 DCV to 3.0 DCV (or there abouts) @ around 10 to 15 mA.

I'm unsure how to approach the increment problem at such low voltages.

Previously, I didn't provide a schematic, but did provide a description...here is a schematic...

Power supply:

Typical solar garden light circuit. 1.2V 2100 mAh battery boosted by QX5252 with 220 uH axial inductor between pin 2 & 4.

According to the datasheet should result in an output of 3.5 DCV @ 15 mA.
QX5252 Datasheet
QX5252 Datasheet

I've modified the output of pin 4 with a shockley diode & a small 603 capacitor = same mod I created via instinct to get RGB functioning in another project, maybe there is a better way (?). Anyway, NE555P doesn't trigger without this mod.

NB: Yes I know the 555 datasheet recommends 5 DCV in. However, other peoples research and my own experimentation proves the 555 can work fine down to 1 volt (which is all well and good if not playing with LEDs which may need between 2 to 3 volts at respectable mA levels to get desirable brightness).

Fader:

Standard 555 fader circuit. pin 3 (output) via 50k pot plus pins 2+6 to BC547 base, pins 4+8 to BC547 collector. 100 µF cap between pins 1 & 2. LED between BC547 emitter and pin 1 (optional mod for red & yellow LED = appropriate resistor between BC547 emitter and + lead of LED). Power + to pin 8, - to pin 1.

NE555P Datasheet

Options:

Playing with pin 5 on the 555 seems to be a possible option to increase the DCV output of pin 3, but I could not find any examples on the internet, just a throw away comment that pin 5 is rarely used in circuits but can be used to modify the 2/3 output of pin 3. Somehow I don't think that is going to solve my problem. Instinct is telling me that a simple mod around the BC547 might be a better option (?).

Any pointers to websites or preferably the provision of schematics to advance my project would be most appreciated.

About me:

I'm just a retired old fart with limited resources who last played with solid state electronics when SCRs had just become available but didn't get the opportunity to play with them (late 1960s?). I have a fair amount of catching up to do in understanding ICs etc. Apart from the basic VRI formulas I'm at a bit of a loss.

My current aim is to make low powered & solar powered toys and novelties for my grandkids (and me!), and share whatever I create on the internet (once I figure out how to edit videos and have something worth sharing).


texts:
I am trying to find the transfer function \$\frac{V_{out}(s)}{V_{in}(s)}\$ of an electrical system that operates according to the diagram below.

\$V_{in}\$ is switched between 0 and 13 Volts (i.e \$V_{in}(t) = 13u(t)\$)

It also assumes that initially the Capacitor and Inductor are de-energised initially.

I am assuming that the first step is to apply a KVL analysis to the circuit. I have attempted but can't seem to get anything correct. Was hoping someone could help me clarify this problem and the steps taken.

Any help would be appreciated.


texts: Instantiating multidimensional array in system verilog

texts:
I want to create an array in systemverilog which has n entries of m bits.

logic [n-1:0] arr [m-1:0]; (a)

Is this the right way to do it? What if I change the order of placement of the range?

Eg. logic arr [n-1:0] [m-1:0]; (b)

Does it represent the same array as (a)?

I also want to create an array of state machines having n entries each entry representing
a a state out of 4 states.

typedef enum logic [n-1:0][1:0]{S0,S1,S2,S3} statetype;
statetype state,nextstate;

Is the above correct way to do it? If it is, how exactly I will access the elements
of this array.


texts: Do i need a LED driver to drive 32 mosfets?

texts:
Im trying to use two 16 channel LED drivers to drive 32 mosfets, im not understanding the datasheet about current sinking, maximum voltages etc.

Are they meant to drive the LEDs by themselves?

Basically im trying to multiply number of PWM pins on my MCU, and want to use 32 mosfets 5A current each to drive bigger lamps.

I know there are basic shift registers, but I cant use PWM with them??
Are there other ICs to achieve this?


texts:
I'm trying to read data off a Hynix NAND Flash chip.

Ive soldered the NAND Flash onto a break out board and connected it to my FT2232H FTDI.

I'm using the following software to read the NAND Flash:
https://github.com/ohjeongwook/DumpFlash

However, I get the following output when I run it:

C:\NAND>python DumpFlash.py -i
Name:           NAND 128MiB 3,3V 8-bit
ID:             0xf1
Page size:      0x0
OOB size:       0x0
Page count:     0x0
Size:           0x80
Erase size:     0x0
Options:        1
Address cycle:  4
Manufacturer:   Traceback (most recent call last):
  File "DumpFlash.py", line 93, in <module>
    flash_util.io.DumpInfo()
  File "C:\NAND\FlashDevice.py", line 314, in DumpInfo
    print 'Manufacturer:\t',self.Manufacturer
AttributeError: NandIO instance has no attribute 'Manufacturer'

C:\NAND>

I have double checked my wiring and I believe it's all correct.

Would anyone have any advice to explain why it's not being recognized? Have I busted the NAND Flash?


texts:
I'm a helicopter pilot. I'm thinking of buying a headset Bose A20. My problem is that the Bose headset comes with a high impedance microphone, but the helicopter I'm operating is using a low impedance 5 ohm system. The most common systems use high impedance.

My question is...

Is there any chance to build an adaptor to convert the signal of the headset to a low impedance microphone signal?


texts: RC Schmitt Trigger Debouncing - Cap discharged but there is a voltage across it still

texts:
As you can see in the image, I'm running the example given in here where I would debounce the limit switch. I'm running the SN7414 with the given resistors in the diagram. The problem here is that with the calculated resistors, I'm still getting a 0.818V across the capacitor, and from the datasheet, the SN7414 will only switch to logic high when the voltage is at the minimum 0.6V.
The guide talked about input leakage current (Ii), which turns out to be 1mA for the SN7414. I measured the current going towards the SN7414 when the limit switch was closed turns out to be 130uA which causes a theoretical biased voltage of 1.066V but the measured voltage is 0.829V. This prevents the SN7414 from reaching it's negative going threshold... which prevents the SN7414 from triggering a rising edge.
In the guide, they used a 74AHCT14 where the Ii = 1uA... this is substantially smaller than in the SN7414.

Am I looking at the right place as to why there is a potential across the cap after the switch is closed?

How do I compensate for this? I can lower the value in R2 by using a 10uF cap.
Note: ignore the "0.733V when switch is closed" in the diagram, that was when R2 = 4.7kohms


texts: What is sitting inside LED array so that I can create my own drivers?

texts:
I have a LED array and an app to drive it:

https://itunes.apple.com/US/app/id1431362600?mt=8
https://play.google.com/store/apps/details?id=com.yskj.led&hl=en_US

I connect to WiFi and I'm able to upload an image or some text to the thing.

I would like to write some clever software that runs on Raspberry Pi (or similar) and I can stream data to the LED array in real time, say stock exchange ticker.

Because it is from China it does not have any brand name, it's difficult to tell what sits inside.

Do you know - just looking at the app - what sits inside so that it is possible to create my own (real time streaming) drivers?

I think I'll have to dismantle it and check what is inside but maybe you'll know...


texts: Using an Arduino module for moisture monitoring as an analog device

texts:
My friends and I are currently working on an automated watering project , and we still have to find the fitting sensor. The easiest solution would be to use a humistor, but since we are measuring the moisture of soil, we figured to use one of these. Can such a device be used outside of Arduino, requiring only sufficient supply voltage.
Note: This is the first stage of the project and we intend to use only discrete components now. Later on the arduino will be invoked, and these hygrometers could be used again.


texts: Can i replace One big transformer with two

texts:
My LCD screen is noisy and the source of that noise is that big transformer inside the red circle, i want to change it but i cant find it anywhere,
so im thinking if i can replace it with two little transformers from an old lcd screen (green circle) ??


texts: PWM input specs of Hobbywing Quicrun WP-1040 ESC

texts:
What are the controlling input specifications of a Hobbywing Quicrun WP-1040 Electronic Speed Controller (ESC) for brushed motors? I assume it should use the standard PWM with 1 kHz frequency as stated in its manual? Do I have to find the "pulse length to motor speed/direction translation" by myself or are there any common conventions?
I want to use the ESC directly without a radio receiver to drive a Himoto RC540 26T motor in an RC car (Himoto Short Course Corr Truck 4WD RTR 1:10).


texts:
I am really intrigued in the idea of designing a remote start using an Arduino and Bluetooth connectivity.

I plan to wire a relay to the starter switch of a motorbike. I have chosen to do it this way instead of directly wiring it to the motor because the bike already has built in safety to make sure it wont crank whilst in gear and will cut off once the engine is running.

Here I have a rough diagram of what I plan to do, please keep in mind I have very little experience on how electricity 'really' works so besides splicing some cables I have no idea if this would work.

Would this setup work?
Would this allow for normal fail-safe functionality in-case the relay failed or some other malfunction?
My primary concern having little electronic knowledge is would this kind of 'bypass' work where the starter switch skips past the relay, what if they were both activated at the same time?


texts: How do random number generators in calculators work?

texts: I have a TI-30xIIs scientific calculator. I was playing around with some of the functions, and I discovered it had a random number generator. I became curious as to how it worked. My first thought was that it used avalanche noise or noise generated by the diodes in the solar panel, but then I realized that they could be using some sort of algorithm like a Mersenne Twister


texts:
Can anyone find a data sheet for what I think is a relay? It has the code cr730-a-24, 7.5A 250V on the case and I've found this picture:

Are the three circles, 3 coils in parallel? How does this circuit relate to the pin-out? In what sequence do the normally open, relay contacts close?


texts: Change memory content of FPGA SoC (DE1-SoC) using software while .sof (EPCQ) is running on FPGA

texts:
I am new to FPGA and FPGA-SoC world. I have a DE1-SoC board. I am doing a project. Hardware design of the project contains a memory block which is initialized using .mif file. I know that we can use assigned address by qsys (platform designer) to control any block on FPGA side using ARM (Linux).

I want to change the content of the memory block in FPGA part using ARM part (With a software program) while the FPGA part is configured. How can that be done?

The HW system on its own works (it was tested and simulated), but the memory content cannot be changed after the HW system is configured. I have to change .mif file, compile and reconfigure the HW in order to change the memory content now. I think there must be a software solution for that which I don't know yet.


texts: Whats is the angle precision of a 3 phases bldc motor?

texts:
I have a small BLDC motor and I would like to use it in a project of mine.

Is there any relation between the minimum angle (precision) I can move the motor and its number of poles?

How could I calculate the minimum step I can move the motor, considering that it has 12 poles?

Thank you in advance for your answers!


texts: This op-amp configuration is giving me trouble

texts:
I came across this configuration earlier today and can't for the life of me figure out the equation for Vout:

It looks like a unity-gain differential amplifier but the ground resistor on V2 is before the series resistor.


texts: What am I doing wrong in finding the phase angle of power?

texts:
Consider a voltage supply \$V\angle \phi_1\$ and a circut with impedance \$Z \angle \phi_2\$.
Now the Apparent power(\$S\$) is given by: $$\bar S =\frac{(\bar V)^2} {\bar Z}$$
Thus phase angle of \$S\$ is \$(2\times\phi_1)-(\phi_2)\$ but shouldn't it be just \$(\phi_2)\$? As \$\cos(\phi_2)=\frac R Z=\frac P S\$ .
Can someone tell me where I made a mistake?


texts: Driving LEDs directly from microcontroller pins

texts:
In the circuit I'm designing, I'm using an at91sam7s128 which is a micro-controller with an ARM7 core.

Its PIO0 to PIO31 provide 8mA max which is low to handle direct driving of LEDs like this:

simulate this circuit – Schematic created using CircuitLab

UPDATED: thanks to jippie and Olin Lathrop for telling me about the resistor in series with the LED.

So some designers use a safer method, connecting PIO to the base of a transistor that acts like a switch:

simulate this circuit

Others just make a simple trick. They connect the anode of the LED to the power supply and the cathode to a PIO:

simulate this circuit

In the last method the LED will turn on when the PIO goes low - acting like GND - and current will be taken from power supply, not from the PIO like in the first method. So do I have to take care of maximum current of the PIO, although it just acts like GND, not like a power supply (like in the first method).

When I set the PIO low, does the pin really get connected to GND or something else?

NOTE: In this Atmel evaluation kit they use the last method, but I need to make sure.


texts: Op Amp with positive feedback (hysteresis) driving N-MOSFET oscillates

texts:
I have a Supercap voltage control circuit that is based on a On Semiconductor NCS333 Op Amp that's configured with hysteresis (using positive feedback) that drives two N-MOSFETs - one that is actually discharging Supercap when voltage goes over some pre-defined limit (~2.5V in my case) and another one to indicate that discharging is active now.

I've used DMN1019U MOSFET to discharge the Supercap as it can tolerate up to 10.7A of current with a very low \$\mathrm{V_{GS(th)}}\$ and \$\mathrm{R_{DS(on)}}\$, so it won't overheat at high currents. Current through MOSFET is limited by 2512-case resistor, \$\mathrm{R_S}\$, so most heat would be generated by resistor and not MOSFET.

When I'm using any resistor down to ~1.8Ohm - system works fine and correct, but if I want to increase discharge current by placing two 2.2Ohm resistors in parallel resulting in 1.1Ohm total resistance (for example) - output of Op Amp starts to oscillate and MOSFET starts to act as a variable resistor and heats up very quickly as its resistance becomes higher than \$\mathrm{R_S}\$ one.

I have tried to use snubber circuit for Op Amp, it helped a little bit, I was able to reduce \$\mathrm{R_S}\$ to ~1.5Ohm but if I go lower - oscillation starts again.

Is there any way to stabilize this circuit? I know that DMN1019U has a very high gate capacitance of 2588pF @ 10V, but I need to choose a MOSFET with lowest available resistance and \$\mathrm{V_{GS(th)}}\$ so power dissipation would be occurring in \$\mathrm{R_S}\$ rather than MOSFET.


texts: What is the origin of the capacitance formula?

texts: Everyone knows capacitance is defined as C = Q/V, but why? Sure I understand the utility of it and its use, but can someone provide a motivation or historical context for this definition? I'm unable to find one on the internet. What I am is asking is if someone can tell me who came up with this definition? When did they do so? What problem were they confronted with? etc...


texts: Are D flipflop inputs and clock thresholds the same for a given logic family?

texts:
I'm using an SOIC20 74ACT574 octal flipflop in a design.

Vcc is 5 V, and GND is 0 V. The datasheets give V_IH (logic high input, guaranteed minimum) as 2.0 V and V_IL (logic low input, guaranteed maximum) as 0.8 V.

A rising edge on the clock pulse ("CP") pin latches in the inputs when OE is low.

The datasheets don't give a nominal threshold CP voltage, and I originally assumed Vcc/2 to be the threshold. That said, I appear to have some nuisance latching. After thinking about it, it seems like the flipflop inputs and the clock input must look largely the same to the signals because they're of the same logic family. In this case, I might be clocking in my signals at a threshold as low as 0.8 V.

My question: Does the rising edge threshold at which latch-in occurs match the V_IH or V_IL figures for this logic family? If not, why? And does this change depending on logic family?


texts: Low Source Voltage: Driving 2V LED with 1.8V Signal, 5V Supply

texts:
I am trying to get a 2V LED to to turn on. The CARRIER_STB# signal is a 1.8V signal. I have a 5V supply connected to the drain. Below is a screenshot of my that part of my circuit. EN_3V3_1V8 has been disconnected for the purposes of testing, but will have to be part of the design. Though that does not seem to be a problem.
I am measuring 1.4V at source, which is not enough to turn on the LED.
I have already tried 4 different N-channel MOSFETs.
The first one I tried was the DMN62D0U-13. When that didn't work, I checked and realized that I might have to pick something with a lower Rds.
Then I tried three more, and none of them worked. The FDN327N, NTR3C21NZT1G, and the NTR4501NT1G.


texts: AP1509 DC-DC Power Supply calculating Inductance?

texts:
I'm working on an embedded system which I want to enable USB Host on for a few devices. As I'm supplying USB Devices with current and am not sure of my own on board current requirements I decided I'd aim high and go for the Diodes INC AP1509 which can supply up to 2Amps. Along with the data sheet there is an Application note ANP013 which shows how to calculate the required Inductor and Capacitor.

My question is that the formula used to calculate the Inductance required uses Time on (Ton) in the formula. But there is no indication as to what Ton is. I know that this DC to DC converter will turn on and off at high frequency to give the required output Voltage and current but I've no idea what Ton or Toff will be. Am I missing something? How do you calculate Inductance and Capacitance? I'm a Software Engineer really so I'm sure there might be something very basic here I've missed.


texts: DC motor selection criteria: number of poles

texts: I’m designing a system to measure an arbitrary motor torque curve. As an active load, I’m searching for a brushed DC motor that is able to withstand some degree of torque and speed as well as comply with some other requirements in my system. I have already evaluated and narrowed down the possibilities based on the manufacture datasheet. However there are still some options with very close specifications but different number of poles in the rotor. My question is, what kind of system parameters should I use to determine the best number of poles in my application? Do they influence vibration? Smoothness when measuring torque? I really appreciate your insights!


texts: Why do they usually make comparators open collector?

texts:
I never see open collector opamps while I frequently see open collector comparators. What is reason for preferring open collector output in comparators?

(Inside of LM193.)


texts:
I'm trying to find these two metal connector parts to make a bulb socket on my device's :

It's a common part in bulb sockets and I don't know why I can't find them on the internet.
How can I find and buy these parts and parts like this ?


texts:
I need to multiplex 16 I2C sensors which all have the same I2C address.
Can I multiplex those by multiplexing SDA signal only? And having SCL signals connected to all 16 sensors all the time time?
I have read some scattered information that it should work, but not definite answer.
Any considerations about HW? Or SW?


texts:
I'm using a lm555 IC in monostable mode. When my input varies from 5v to 0v the output goes from 0v to 5v. But this only happens perfectly if it happens just a pulse at the entrance, in case my input changes from 5v to 0v and continue at 0v for the rest of the time the output does not work correctly. What I want is the following, when my input changes from 5v to 0v and continue to 0v, I want my output to remain high only for the time I have determined.

What I have:

What I need:

I thought I could do that with transistor input, but I did not find a way to do it. If anyone knows something similar thank you.


texts:
This may be on the limit of ATTiny13 possibilities, but still: is it possible to connect ATTiny13 to USB to get ADC readings (one way)?

According to this article http://www.vk2zay.net/article/211 (and my understanding of it) it seems doable, though the size of the serial communication program takes a lot of memory.

However, instead of max232 I have Micro USB to Serial Adapter from microbot (http://www.microbot.it/products/mr002-002-1.php ). (Well, I also have max3323 chip, but I would like to spare it for something else).

I am aware of this question:
How can I communicate between micro-controller and PC without the use of RS232/USB Adapter?

but can't quite understand why max232 is needed in between?

UPDATE: I can't find any better datasheet on the adapter, but it uses MCP2200 chip.

UPDATE 2: as Passerby answered below, one can connect attiny directly to the microbot's adapter. For the record, these are changes I made to above mentioned project to make it work:

Line 52 of the code needed "const": const unsigned long mags[10] PROGMEM = {... to make avr-gcc happy.
Pin 6 of the attiny needs to be connected to RX of the adapter (attiny can use Vdd and Gnd for 5v power)
I have not set any fuses with avrdude (removed them in Makefile)
Baud rate in my case was 1200, and all it took to see the output of attiny was cu -l /dev/ttyACM3 -s 1200 (I guess, cu does some magic to the adapter in the beginning to set the baud rate). Baud rate has been calculated by looking at the pin 6 output with oscilloscope, which gave about 0.8 ms min pulse width. (cu is Linux/Unix serial utility, another one tried is minicom)
The datasheet for the adapter is not enough. I needed to look up MCP2200 chip's specs to make better guesses


texts: Does FFT plot in an oscilloscope indicates the division or span of the frequency?

texts:
When measuring voltages V per division is indicated. If the scope shows 10mV/div it means each square's horizontal edge represents 10mV.

Is that the same with FFT graph?

Here is an example:

The reason I'm asking is that in my previous question it was said that this might belong to a 80kHz switching device.

I thought in the above FFT picture each square represents 250kHz before.
But now I'm confused. Is 250kHz per div(per horizontal square) or the entire span which is 10 horizontal square edges?


texts:
I'm considering evaluating the NXP BGA28xx series MMIC for my application, a fixed-frequency special purpose AM receiver, because

they're cheap
they're very simple to wire up
they claim to be internally matched to 50 ohms without even specifying what frequency that would apply to
they claim operation down to 0Hz, and I'm between 1-10MHz which is too low for some MMICs

Is this too good to be true? How is it possible for this device to be automatically matched over its entire range? Would it be suitable for a basic, low bandwidth LNA?


texts: I need to convert +5V to +12V with minimal components and PCB space

texts:
I need a +12V reference voltage for an op amp circuit, so it doesn't need much current. I just want a simple surface mount device that takes up little room, and doesn't need a ton of passives or large capacitors to work.

I am currently using this device.

I no longer need the -12V rail, and this one takes up a lot of room. Anyone have any ideas?


texts: Sharing negative terminal ("ground") between 2 LiPo batteries and UBECs / paralleling 2S LiPo packs

texts:
One of my projects require a hefty amount of amperage - and as such I want to use 2 LiPo 2S batteries, in parallel. In addition, I am regulating the voltage using multiple DC-DC step down converters ("UBEC" - https://www.hobbyking.com/hobbyking/store/__4319__TURNIGY_3A_UBEC_w_Noise_Reduction.html).

The 'trivial' approach would be to use parallel the batteries while being used (and charge them separately). Does this present potential cell imbalance issues/dangers? How does this behave with the multiple DC-DC converters?

Since I am using at least 2 DC-DC UBEC converters, I was thinking maybe I can get away with just connecting the 2 batteries negative terminals together, having each battery power half of my load. Would this work? Do I need to join the negative/"ground" terminals at the battery or after the DC-DC converters?

Thanks!


texts: Transistor differential comparator threshold

texts:
It seems that the circuit bellow acts as a differential comparator. I confirmed it by simulation on LTSpice.

simulate this circuit – Schematic created using CircuitLab

I remark that output flips when VA=VB. I can easily determine Low to High transition by neglecting base current of Q1 (the results are close to simulation value): $$V_{LH}=\left( 1+{\frac{R_1}{ \left( R_4+R_5 \right)//R_2}} \right) *V_{ZD1}$$
How can I determine High to Low transition?

Can someone explain how Q2 is passed/blocked?


texts: Accelerometer raw data output to measure vibration,and do a frequency spectrum/ amplitude spectrum?

texts:
Ive used an Arduino to measure vibration on a washing machine and have up to 100 raw data out putvalues. I want to present an amplitude/frequency spectrum with these values, i have matlab and simulink , but dont know how to start?

And example of how i think

Ax=[1 0 6 25 1 51 51 81 81 51 1 51 51 511 1 551 51 1 1 51 51 10 51 05 1510 15 5 8 0 8 0...]

time= 0-100 seconds.

plot(freq/amp specturm).

Regards,

Volkan


texts: How to interpret TI Chronos watch accelerometer data

texts:
I've been trying for an embaressing amount of time to figure out how to interpret the wireless accelerometer data from the TI Chronos. From my laptop with the usb-radio included, I read it into python basically following this recepie, then I throw it into a pyglet application to display the 3D acceleration vector. Its read in as unsigned chars, but I can't make any sense of the data. Neither have I find it documented anywhere. Here is an example printout from holding the watch still, while rotating it among 1 axis smoothly.

[253 245  24 255   6   7   1]
[  0 241  20 255   6   7 255]
[255 229  28 255   6   7 255]
[255 229  25 255   6   7 255]
[  1 229  19 255   6   7 255]
[249 224  21 255   6   7 255]
[254 219  17 255   6   7 255]
[255 218  11 255   6   7   1]
[247 211  15 255   6   7 255]
[251 209  10 255   6   7 255]
[251 212 255 255   6   7 255]
[243 194  16 255   6   7 255]
[243 200   7 255   6   7 255]
[247 197   3 255   6   7   1]
[246 190  10 255   6   7 255]

Obviously the first 3 bytes are the accelerometer data, and also clearly the numbers needs to be signed somehow. But why aren't the force vectors smooth? It's more obvious in the opengl visualization, but even in the small dataset above, one can observe for instance jumping from 255 to 1 in no time. Finally I want to get actual Gs from the data, but for now I'll settle with getting a smooth force vector that seems somewhat coherent with the rotation of the watch. Bonus points if anybody knows what the last 4 bytes means. Hopefully this is a chiphacker type question.


texts:
I am trying to measure a DC signal in the mV range.
Below is the waveform I get after I connect the oscilloscope to its probe and without connecting it to anything:

I am getting a ripple like waveform of 50mV peak to peak. Why and from where am I getting this unwanted 50mV peak to peak ripple noise even when the scope and its probe is not connected to anything?
Why is there this noise and how to eliminate this noise ripple for proper and accurate measurements?


texts:
Let's consider this simple circuit

simulate this circuit – Schematic created using CircuitLab

with

$$V_S = 15 \ V$$
$$R_S = 500 \ \Omega$$
$$V_Z = 5.1 \ V$$
$$R_L = 1 \ k\Omega$$

It can be described by the system of equations

$$V_S = R_S (I_Z + I_L) + V_Z$$
$$V_S = R_S (I_Z + I_L) + R_L I_L$$

where \$V_S, R_S, V_Z, R_L\$ are constant and only \$I_L, I_Z\$ are unknown.

Supposing that the Zener diode is inversely biased, voltage at node A will always be the Zener voltage \$V_Z = 5.1 \ V\$ and with these values \$I_L = 5.1 \ mA\$ and \$I_Z = 14.7 \ mA\$. If the resistance \$ R_L \$ is decreased, the value of \$I_L\$ will raise and \$ I_Z \$ will be lower. The limit condition is when \$ R_L = R_L^* \$ is so small that it requires \$ I_L = I_S \$ and the Zener branch has no current.

What does happen if \$ R_L \$ is lowered beneath \$ R_L^* \$ ?

What assumptions should be followed to write new equations? How would the Zener diode behave and how can it be considered?


texts:
I am designing a mechanical attitude indicator for the avionics simulator. I need a pancake slip ring, that drives servo (max 500mA at 5V) and some backlight.
My idea is to use a gold-plated PCB and brushes mounted on the other PCB.
But I am struggling heavily, to find suitable brushes, that can be PCB-mounted.
The only thing I found is EMI gold finger contacts and pogo-pins, but they are too stiff for this application, what I am looking for is similar to the wiper of the potentiometer. Any help?


texts:
I am trying to amplify the signal from ACS712 to read it better. The problem is that I am using an 8-bit ADC, and what I want to take measure are things like energy-saving lights, or other things with low consumption. So what I am trying/what I want to do is
1) Rectify the signal (from a sinusoidal signal, with range 0-5V, to a signal not sinusoidal 2.5V-5V).
2) Lower the level, from 2.5V-5V to 0-2.5V
3) Amplify the range, from 0-2.5V to 0-5V (there is an alternative: amplify to 0-10V but saturate on 5V)

In this way, I will take advantage the 256 step better (in the case of saturate the signal the ADC will read better the low consumption... no?)

Here is the schematic I copy from the ACS712 datasheet, I was making some test with operationals on proteus, but I get no good result.

simulate this circuit – Schematic created using CircuitLab

Thank you.

EDIT

Finally, after an infinite number of tests I get this circuit:

The signals on the oscilloscope are:
-Green: GND
-Yellow: the signal from the source without the DC signal (after C3).
-Blue: the rectified signal (it loses some signal).
-Pink: the amplified signal (it works perfect between 0V and 1.6V... but only amplify until 3.5V, it makes different pictures if source is on 1.7V or if is on 5V, but the max value is 3.5V).
I was trying to remove the first LM358 and put a diode and a capacitor... but testing, and removing all circuit for the test, and let only C3, R9 a diode and other resistor (parallel with R9), I get a 1V constant signal after the diode. The circuit was like this:

simulate this circuit

The capacitor is not connected because it would be the next test, but the first failed.


texts:
I wish to drive a set of NEOPIXELS (ws2812b) using the STM32F4 discovery board, so far i managed to get a 800 kHz PWM signal using the CubeMX.

And

And the following code:

/* USER CODE BEGIN 2 */

HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1);

/* USER CODE END 2 */

But when i add these lines of code

/* USER CODE BEGIN Init */
uint16_t pData[25] = {8,8,8,8,8,8,8,8,4,4,4,4,4,4,4,4,2,2,2,2,2,2,2,2,0};

/* USER CODE END Init */

...

/* USER CODE BEGIN 2 */

//HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1);
HAL_TIM_PWM_Start_DMA(&htim1, TIM_CHANNEL_1, (uint32_t *)pData, 25);

/* USER CODE END 2 */

My PWM signal just disappears, what do i need to do to control the PWM with DMA?

edit:
It is posting the DMA sequence, but the DMA needs to be changed to circular to see it on a scope


texts:
I have a USB Tester like this one:

https://www.amazon.com/KCX-KCX-017-Power-Capacity-Tester/dp/B00WBHQJ8W

I have connected it by mistake to a 23 volt power source and the item stopped working. When I opened the item I found that a component was burnt (See the picture below the item marked by the red square):

I found a picture of the same board with the component clearly marked V2MJ (See the picture below):

I've searched the internet and I couldn't find what is this component.
Can anyone help me identify this component and if there is a replacement for it?

P.S. The board is marked with a KCX-017-20131222 marking:


texts: Converting LED fairy lights from battery to power

texts:
I have a set of LED lights that I like that only have a battery pack option.
To make it work, I cut the battery pack off and wired it to a 5V power supply. Only half the lights turn on at a time. If I reverse the polarity, the other half come on.
How I would fix this?


texts: Linearization of nonlinear plant with system identification in Matlab

texts:
I hope this question fits in here and there is someone who can maybe help me.
I am new to control theory and I have a very complex Simulink model which is nonlinear. I want to have a linear approximation of this model to design a controller for this system. I tried to linearize the model with the Model Linearizer of Simulink but this did not lead to any results.
Now my question is, can I approx this model by using the System Identification Toolbox of Matlab by trying to fit the input/output data to a linear model and use this approximation for control design?


texts: MOSFET (N) On resistance much higher than datasheet under load

texts:
This is my first post on this forum and I am hoping to be much more involved in this forum. I am currently designing  circuit that needs to switch a load of 200 mA by controlling its GND via a MOSFET (N). I chose a MOSFET with very low \$ R_{ds} \$ (On) of 25 mΩ (DMG6968U) but when the load switches on the ON resitance goes up to 12 Ω causing  a large voltage drop. I am really confused. anyone know why is this happening.

Edit: I am simply tying the gate to +5v or GND to do the switching
Added the schematic.


texts: What is high side current limiting? While google searching for the term I have found ICs that describe their application as "high side load switching". Is this the same thing or something utterly different? Furthermore, the term implies that there is low-side current limiting also? What is this?


texts: Can a pic drive a 5 volt relay directly without a transistor switch?

texts: Can for example this microcontroller drive this relay without additional circuitry, now I read a bit and I know that the current required by the 5 volt relay (40 mA) is more than what can be sunk by a single pin(25 mA) so can I connect all pins of port A for example to sink enough current for the relay.


texts:
Is there a way to use Altium to automatically generate test points on an already routed board? When there is no usable via, I'd like to place a pad on the net.

When reviewing Altium API reference documentation, especially for the IPCB_TestPointStyleRule object, I see this statement :

  The auto-router includes a test point generator, which can identify existing pads and vias as test points, as well as adding test point pads to nets which cannot be accessed at existing pads and vias.

This sounds super promising, but looking at the auto-router, I see nothing that refers to test points placement. I assume that the net would need to be routed by the autorouter to get a testpoint added.

Anything I could use? I am considering scripting the feature, which I'd like to avoid.  I found a script on GitHub that creates the test points but does not place them.

Thanks


texts:
For two input AND gate what will be the output if one input is 3.3v and other input is 5v?
Ref: VCC=5v, GND=0v.


texts:
I am designing a 5V digital circuit and I want to make it generic so the user has some flexibility in the VCC input limits. The problem is, since the MCU has to run at 5V, I have to ensure it will get the 5V, and to do so I can place a LDO or a Linear Regulator (I am avoiding switching regulator because they require more components, and usually not small SMD ones), but both of them CAN NOT be driven at 5V since they have a minimum voltage that has to be greater than the regulated voltage.

Is there a way to still have a regulated VCC input and if the user connect the voltage I just want I wont have any problems?

To be more clear, this will be used in R/C (Remote Controlled), which already have a shared 5V wire, but some R/C use 6V, which could be fine for a LDO, but not if the user connect a 5V directly.

If you need more details, please let me know.


texts: What exactly is meant by 'CompactFlash' in the context of flash memory?

texts:
I've been doing some inquiry about flash memory and I do know how flash memory works and I do know about the different layouts (nand/nor) and how the reading and writing processes function.

My question regards the term 'CompactFlash'. I would like to know exactly what is meant by it, and by extension, if there are alternatives to it. All I've found googleing either explains the basics of flash memory (which I am aware of) and then jumps to different memory cards you commonly find or is too detailed to follow.

So, to restate my question: What is the relationship between NAND/NOR flash memory technology and CompactFlash?

Thank you!


texts: I have the diagram below, but I don't understand how the switches are hooked up. Is that an special switch, or I can achieve that with an special connection? Thank you!


texts:
I am trying to simulate an op-amp integrator with a high bandwidth op-amp LTC6253. When I apply a 2mv-p2p signal centered at zero voltage, the integrator settles with an exponential voltage envelope centered around -224mV.But the integral of the square waveform settles around -25mV by calculations i.e. $$V_o =-10^6\int1mV dt =-10^3t$$.
So if we start from zero initial conditions, for 50us, which is the on time of op-amp, we reach -50mV and then again go back to zero as shown

This gives a waveform centered at 25mV.
From the this question,I know that this happens due to the feedback 25Mohm resistor.I have added this so that the op-amp does not saturate.I did not want to go through the trouble of using a reset circuit , because we would need again to find some way to reset it at particular times.I think feedback Resistance is the usual cure of this DC drift. And it is suggested to use it as large as possible.For clarity my doubts are:
q1) Why do we see this exponential envelope? Does feedback resistor has something to do with it?
q2) Why is the output not centered at -25mV?
q3) Can we improve the response time?


texts: How to add custom 3d packages path to pcbnew

texts:
I'd like pcbnew to find my custom .wrl files for my custom footprints without having the absolute path hardcoded in the .kicad_mod files. I can manipulate the KISYS3DMOD environment variable but then, or course, the standard 3d models are no longer found.

I've also tried to set the path to the model in the .mod file to ${KIPRJMOD}/../packages3d/MyComponent.wrl but that doesn't seem to work. Also putting multiple paths into KISYS3DMOD separated by a colon has no effect (well, the effect is, that neither path works).
I don't want to put my custom packages on every system to /usr/share/kicad/modules/packages3d/, or course.

Any help is greatly appreciated.


texts: Vertical ghosting on 64x32 1/16 RGB LED matrix panel

texts:
I have been working at driving some of those generic LED matrix panels found all over the web for sale (such as this one), 64x32

I've struggled a lot with the lack of real documentation, but I've managed to create a pretty decent image using an FPGA and binary code modulation. However, I've got a problem with vertical ghosting that I can't seem to fix.

In the image above, all of the dim pixels within the circled area are supposed to be off, but as you can see the ones in the first row are not. Because these LEDs are half off, they don't ghost into the 2nd row.

If I turn the LEDs in row 16 off, the half-lit LEDs on the top row turn off completely, suggesting that the 16th row was "bleeding" over into the first (row 16 being the last row in the top half). In the image below, notice how row 16 (circled) is itself dimly lit despite being written to zero:

I didn't want to post my verilog code in full as I was worried it'd make the post too long, but I'll happily provide it if it helps. Regardless, the basic process I'm following to draw each top/bottom row pair is:

Clock out a row of data using RGB and CLOCK signals on panels
Blank display by taking OE high
Latch out the row data by taking LATCH/STB high
Take LATCH low
If we're on the final (5th) BCM iteration, increment current row (row address pins A,B,C,D) to set up for the next pair of rows
Take OE low to enable display again
Delay up to a value required for the current iteration of BCM output
Double the delay value for the next pass and repeat until the row has been output 5 times (5bit BCM, 15bit colour)

I'd be really happy if somebody could enlighten me as to exactly what causes the ghosting in the first place, and how I might go about reducing/eliminating it.

I've tried slowing the process down, moving the row/address increment timing so that it occurs slightly earlier and before, but nothing seems to help.


texts: PCB Board disappeared in Altium after redefine shape

texts: I tried to change my board size and potentially misclicked as I was redrawing the board. Is there a way to get the board back? I redefined the shape again and it shows up in 2D view but is missing in 3D view as you can see in the 2nd picture linked. (Undo did nothing to bring the board back)


texts:
I have to replace a faulty SPDT 895-1C-C relay so now I'm looking to buy the product. The problem is that this model it's not the most popular in the world so I thought that I might use something equivalent instead.

I wrote a list with few properties that I consider are important when searching the equivalent relay:

to have the same PCB terminal type (eg. 1C => SPDT)
to support the same resistive load (eg: NC=10A/14VDC, NO=20A/14VDC)
to support the same coil voltage
max carry current per unit of time

Other props that I regard as optional are insulation type, shock resistance of life expectancy.

Since the relay would be soldered on a PCB its size should be also considered, for obvious reasons.

Btw: on the PCB board there are 4 such identical relays. I want to replace only one. This should be also taken into account.

What do you think that is most important when searching for such equivalents (specifically for relay equivalents) ?


texts: Maximum cable length for 5V or 3.3V I2C, UART, or 1-wire signals over Ethernet and how to increase it?

texts:
I know similar questions have been asked before (Maximum cable length for 3.3V UART signals) but I would like to know the answer more specifically for a hobbyist.

I've been experimenting connecting various devices to an Arduino via I2C, UART and 1-wire. I have an adapter the goes form pins to RJ45, so I'm using them on both ends. I keep getting data errors when I use certain Ethernet cables, mostly in lengths over 10 feet. While I understand in principal the signal loss due to interference and resistance. I'm finding little information on how to quantify or overcome it.

I'm trying to figure out a way to boost the signal or utilize the Ethernet cable in a different way so that the lengths of cable can be longer.


texts: 5v Solar Cell Charging a 3.3v Battery while in use will the circuit see 5v instead of 3.3v?

texts:
I have a tiny arduino type project that needs 3.3v that needs to run off grid and I have some tiny 5v solar cells, now I plan to put a battery between them to keep it all working 24/7.

I was thinking nicad as I get the impression that Lithium batteries would be the cheapest, but maybe a pain to charge.

So my two questions are really, what is the best battery option (cost is the top priority), and if the battery needs more than its own current to charge, then do I need to do something clever to limit the voltage into the circuit?

EDIT added a schematic...

simulate this circuit – Schematic created using CircuitLab

The sensor in this case is a soil moisture meter and bluetooth (low energy) beacon. The solar cell(s) are 5v 30ma units, I'll be looking to add a timer so it does a reading/transmission for (say) 30 seconds every hour - I'll work to what the solar panel can manage! A server device (with real mains power) will be listening and keeping track of what sends what and when.

Thanks for the answers here, I also found pretty much what I described here...
http://www.robotroom.com/Solar-Recharging.html


texts:
I have a Lepai LP-2020A+ audio amplifier and a König FM Pocket Radio.
My problem is that the pocket radio works really well on its own, with the headphone plugged in, but when I connect the radio to the amplifier through a 2xPhono to jack cable, the radio signal disappears.
I suspect this is because the radio uses the cord of the headphones as an antenna, but do you guys have any suggestions on why this is not working for the amp, and how to hack the setup such that the FM radio gets a strong signal, even when connected to the amp?


texts: Using old components stored in a damp cold shed for decades?

texts:
I have tons of never used electrical components like resistors, capacitors, coils, transistors from 10 years back and tons more of my fathers stuff (made in the Soviet Union) from 20..30+ years back.

They've never had anything rain on them, but they've spent only 4 years of that total time in a heated house and then went back into a shed.

Most of the resistors, capacitors and coils are in matchboxes or bigger cardboard boxes and most of the transistors are luckily packed in waterproof (and airproof?) plastic. All of the smaller boxes have been packed tightly into larger non-weatherproof cardboard boxes.


texts: Circuit with a main switch that powers on/off 4 different switches with LEDs

texts:
I've been searching for a circuit that has a centralized switch, with 4 different switches for separate groups of LEDs.. and all I get for a result are diagrams without a centralized switch.

Well, to elaborate what I'm talking about, here it is:

I'm looking for a schematic that has an on/off switch for the main LED. When the main switch is turned on, the main LED is switched on, and (say we have 4 different switches connected to it, with 4 LEDs connected to one switch) I can pick which group of LEDs I want to light up, hence the different switches. And when all the switches are switched on, all LEDs will light up.

When the main switch is turned off, all the LEDs will be turned off too.


texts:
I am working an ATmega32u4 based custom board.
I think I am done with majority of the routing. Now I need to work on the proper shielding of EMF. So I began putting ground pour on the top plane.

Now the question is, I have a couple ground traces (in blue) on the bottom layer, and was wondering if I should also have a ground pour on the bottom layer too?


texts: Connectors for quick swapping PCB components

texts:
I'm working on a project that uses a bunch of "hobbyist" components (regular components mounted on breakout boards) that I would like to mount to a main PCB. I want to make the components swappable by putting headers on the main PCB so that you can simply pull off and plug in a new component should one fail (not that they are likely to fail, it just somehow became a requirement). This would work fine however some of the components don't come with any presoldered pins and I don't want to have people soldering pins to them to swap the components.

Are there any kind of connectors that allow you to plug PCBs into them that have nothing than standard 0.1" spaced predrilled holes?