texts:
I have a little bit of experience with PCB design and made a couple of small circuits for learning purposes.

I need to test out a new PCB designed by another person and its kind of a complicated board with a ton of components on it. It consists of an ADC and an FPGA and other components that go along with it. It's really similar to TI's  LM97600RB Reference Board and was based off that design.

The board was incomplete and I managed to solder what was left however, I have little to no experience on how to test it out.

Are there any guidelines I can use in order to test the board and the components on it ?
Do I test the FPGA separately first?
Would it be possible to just test the ADC separately ?


texts: Bootstrap a phase-tracking PV inverter without mains: possible? How?

texts:
This question is just out of curiosity.

Let's say I have a mains-connected PV system installed over my roof with a phase-tracking inverter. Now main's is out for some extended time and I need to live with electricity, but without the mains the inverter wouldn't work. Can I bootstrap this mains inverter with:

A diesel engine-generator set?
A wimpy-powered offline UPS with PWM-based sine wave output?

My intention is to feed the output of the equipment into the mains input of the inverter to make it track on something and push out power, which in turn can be used to power the house.

Is this possible? How to implement this?


texts: Is HC-05 Bluetooth adapter suitable for logging fast?

texts:
Just bought HC-05 bluetooth adapter from Ching and I wonder how fast HC-05 is if I can do logging with it?

Assume that we have a PC and a microcontroller. The PC have a FTDI232 connected to the USB port and the FTDI232 is connected to the HC-05 and I send values from the PC to the microcontroller, who also have a HC-05 connected to one of its UART:s.

Is that a proper way to logging wirelessly if I want speed? I have a 10 ms limit. Better to use USB cable directly to the microcontroller from the PC and replace the PC with a Raspberry Pi?

The goal is to have a equipment that are portable. But I will first check if HC-05 is a good choice.

What to do:

I want to setup a communication line between a PC and a microcontroller. The PC will have a FTDI232 + HC-05 connected and the microcontroller will only have the HC-05 connected to one of its UART:s.

Reason why I'm asking:
I plugged in the FTDI232 to the USB port of the computer and then I connected the HC-05 to the FTDI232. Then I send the text to the USB port "AT+HELP\n" and I did get a list of commands.

When I notice is that the list was displaying quite slowly. So that's make me wonder if the HC-05 is slow or is it fast and something else cause the slowness?

Because I'm used CuteCom for talking to the FTDI232 chip and CuteCom is really fast and the FTDI232 is super fast. So that leave the HC-05 as the only choice left. Can it be HC-05 is a slow product in communication?


texts: First steps in building Switching power supplies

texts:
I want to make a 50Amps switching power supply, I have already done 10A linear ones succesfully

This time it has to be a switching power supply one so, any ideas or tips of where to start are appreciated

IF I succed and works as intended this will end up being used to power a high power laser at a research center, but if I fail nothing bad will happen, I just want to have the chance to work in this project and as I said, I do this more for the experience than anything

I do know its not an impossible task, but not a trivial one, either however I need some ideas of where to start


texts: Circuit approximation of Induction in guitar pickups

texts:
I was trying to learn the way basic guitar circuits work, the other day, and I stumbled upon a thing that I couldn't fully understand.

According to this site, a simple guitar circuit can be made as shown on the image below.

As i understand the tone knob is represented by an LP filter with a variable cutoff frequency changed by the variable resistor, where higher the resistance is the brighter the tone is(higher frequencies in the signal). The volume knob on the other hand is a simple voltage divider represented by a potentiometer, regulating the voltage levels of the output signal.

Considering the way the tone RC filter is wired, it should only work if the pickup behaves as an AC current generator. I did AC analysis in LTSpice  and the results came out positive.

The thing is that it is quite counter intuitive to me since I have always thought that EMF is induced in the coil according to Faraday's law:
$$EMF = -N\frac{d\phi}{dt}$$
and then the current in the circuit depends on the load connected to the induction coil. According to this I should replace the pickup with an AC voltage generator but then the RC filter would not work.

Could anyone help me explain the way induction works in this process because clearly I have a mistake somewhere in my way of thinking.


texts: How does a number is saved in a register

texts:
I've tried looking online, but I still haven't quite figured it out - does a number, for example 0x100 saved in a register by some convention like little/big endian like thigs are saved in memory or maybe it is just casting every digit into 4 bytes from lsb to msb? e.g. if I'm writing the following line in assembly:

movq $0x100, %rax

will rax look like this: msb 00000000 00000000 00000001 00000000 lsb

or perhaps something else by little-endian convention or something like that?

thank you for your help


texts:
I've been in the habit of making vias on homemade pcb's by putting the leg of 1N4148 diode into a 0.5 mm hole, cutting it off to length and soldering both sides.

However, now my led controller broke and I traced the problem into a broken ground via. On closer inspection, the wire has separated from the solder:

There was about 2 ohms of resistance between the wire and the ground plane where it connects. During operation, there has been about 1 ampere of current going through it for a few hours each day. The device internal temperature stays below 50°C at all times, and has always been stored and used indoors.

Are there any obvious things that I'm doing wrong? I doubt it is a cold joint, because a bit of solder remains also on the wire.


texts: Can I place an electrolytic capacitor close to a solder point on a two sided pcb?

texts:
I’m designing a pcb, which is going to be installed inside a metal chassis. To minimize space I will make it a two sided pcb. (See pictures)

Because there will be parts mounted on the top face of the chassis itself, smaller components like resistors will go on top of the pcb and pretty much everything else will go below hanging from it, including electrolytic capacitors. My capacitors are radial but because the chassis is not very tall, I thought the best way to fit them would be to just bend the leads 90° and mount them sideways like axial capacitors and that way everything fits nicely.

My concern is that probably there will be points of solder from the resistors on top that will end up very close to the body of the capacitors below, probably in direct contact.
Could this be a problem in terms of some high voltage difference between the solder point and the inside of the capacitors that could break the outer layer of the capacitors? The circuit will be working with voltages in the 200-350 range.

My thinking process is that if the caps are designed to withstand high voltages inside, there shouldn’t be a problem with some high voltage touching the outer layer of insulation, right?

Top of pcb

Bottom of pcb

pcb inside of chassis

probable points of solder (grey dots) close to body of capacitor


texts: using Capacitors to block variations in source voltage?

texts:
I've seen several circuit diagrams having a 0.1 microfarad capacitor connected to the supply voltage.

How do capacitors work to prevent fluctuations in DC source voltage? Why don't they completely block DC and act as a sort of break in the circuit


texts: How to analyse the circuit performance of an electret microphone

texts:
I have a simple circuit that amplifies the output of an electret to drive a simple volume visualisation with an array of LEDs.

I didn't design the circuit (though I did build it - works fine), but ignoring whether this is a good circuit or not, I would really like to understand and be able to calculate precisely what is happening in the interaction of the electret and Q1.

Specifically I think this boils down to being able to calculate unexcited, nominal and peak AC signal across C2, and the effect this has on the current to the base of Q1.

Here's what I've got so far:

The Unexcited State

This is quite straight-forward. C2 is effectively open circuit, so Q1 is purely current-biased through R2, enough to have it on in the linear region. This grounds the base of Q2 and so LEDs are off.

The transistors used here are S9014 NPNs. From the datasheet, Vbe when on is 0.7V and typical beta(β) is 280. So:

Ic(sat) = Vcc / R3 = 3/10kΩ = 0.3mA
Ib(sat) = Ic/β = 0.3mA/280 = 1.07μA
Ib(actual) = (Vcc-0.7)/1MΩ = (3-0.7)/10^6 = 2.3μA

The operating curve for Q1 is along the line intersecting Vce=0/Ic=0.3mA and Vce=3V/Ic=0. Considering static characteristic chart in the S9014 datasheet, this line is in the unreadably small left corner of the linear region.

So I think that establishes Q1 is on in the linear region when no input from the electret.

Nominal Signal "loud and close" (94 dB SPL)

So now I get to the core of the question - how to factor in the electret signal?

I'm using an electret similar to CMA-4544PF-W. It is biased through R1. From the datasheet I find typical sensitivity of -44dB for reference 1V/Pa at 1kHz and calculate the transfer factor thus:

Transfer factor = 10^(Sensitivity/20) = 10^(-44/20) = 6.3mV/Pa

Now this is where I start to get lost. I think this means the amplitude of the signal will be 6.3mV: so C2 removes the DC offset and I'll have a 6.3mV alternating signal passing to the amplifier stage.

In practice, I believe the effect of this is to suck current from the base of Q1 on the down cycle, effectively trying to turn Q1 off and allowing Q2 to turn on in proportion (and vice versa on the up cycle).

If that is what is going on, I'm thinking I should be able to calculate at least the limits of Q1 operation with this signal. Specifically, how low/high would be the Q1 base current, and hence be able to calculate the limits of Q2/LED operation.

Does that sound correct? If so, what's the best way to calculate it?

Peak Signal?

I'm thinking I should also be interested in the absolute limits of the electret. i.e. what is the peak signal it can spike? Or is this in fact the sensitivity I'm already looking at?

PS: if anyone can suggest a good reference for methods of modelling an electret in a circuit, I'd greatly appreciate it! I searched but didn't come up with much. You can probably tell I'm still learning how to figure this out.


texts: Switching a millivolt gas valve with a low-voltage digital timer

texts:
I have one of those old gas heaters that has a millivolt valve powered by a thermopile. I want to control it with the brain of a digital programmable outlet timer (minus the AC switching components - this is just the controller board) so that I can program it to come on for an hour in the morning before I wake up, without having it running all night.

The valve runs on 0.5v, and when connected draws a current of 75mA. To actuate the valve, you simply have to make a circuit between two contacts.

The timer is powered by a 1.5v AAA battery. When it switches on, it makes a circuit between two contacts. I thought that I could simply wire these two contacts to the heater valve contacts to actuate the valve. Unfortunately, the amount of current that makes it through the timer is only 1.85mA, which is not enough to actuate the valve!

I'd like to keep this setup as energy-efficient as possible so I don't have to connect a power cable or swap batteries all the time. The valve is great because it's powered by the heater, and the controller is great because it draws like 5µA from a single AAA battery. Is there a way to use transistors or other components to give the valve the 75mA that it needs?

Thanks!!

Update #1:

Gas valve: https://www.grainger.com/product/ROBERTSHAW-Gas-Valve-6KXC7
Thermopile: http://www.emersonclimate.com/Documents/White-Rodgers/Catalog_2010/2010_Cat_pg_059.pdf (Model 101934F32)
Block diagram:

simulate this circuit – Schematic created using CircuitLab

I've tried simulating the MOSFET circuit on the left, but even when I set the gate threshold to 0.2v, I can only get the drain-source current up to 75mA if I pump like 100v into the gate, which obviously won't work. The circuit on the right would be great if I can find a relay with a really low coil voltage that consumes very little current. Any ideas for either one?

Update #2:

I modified dmitryvm's schematic to eliminate the 1.5V battery and add a resistor to represent powering the timer. I also added a switch that will hopefully work in practice when I use the timer as a switch. Here's the new schematic:

simulate this circuit

I did some testing of the transistor, and it seems to work, although I had to crank up the voltage to 10V because my multimeter's resolution is 10µA.

Update #3:

Success!! I discovered that the timer actually puts out 1.5v when switched on, so I was able to trigger the FDN337N with it. What a great little MOSFET! Thanks to dmitryvm for the recommendation. I even made my own PCB. The timer is now programmed and connected to my heater. Here are photos of everything:

Ugly but functional Eagle schematic

Eagle PCB layout

Timer and PCB

Timer powered by PCB

Timer connected directly to heater (temporary until I have time to hook it up in series with the thermostat).

Thanks again to dmitryvm and everyone else who contributed. This is my first time posting on StackExchange, and I am really happy that this project was successful.


texts:
Is there software out there that will take a schematic as input and simulate its functioning?

I don't have a lot of cash for components and tools, so this would be a cheap and easy way for me to learn more about electronics.


texts: Setting up an STM32F103 8 MHz clock source

texts:
I'm extremely new to the STM32F103 (just received it in the post today) and would like to know how (the best way) to set up one of its pins as a clock source for an external circuit.

Ideally, I would like it to be able to produce a 2, 4 or 8 MHz (software selectable) clock signal suitable to run an external microprocessor.

Can anyone point me in the right direction with some example code?

Thanks!

EDIT: Oops. Missed out an important part of the question - I need TWO clock sources - one as described above and the other fixed at 2 MHz (but synched with the first clock signal.)  Is this possible using one or two of the Timers?


texts: How to write this boolean expression using only NOR gates?

texts:
I'm having some trouble understanding how I can convert a boolean expression to a NOR-gate only expression.

What I'm working with looks like \$T = A B' C + A' B C' + A B\$. How would I go into implementing it with NOR gates?


texts: How to check whether a byte of 8 bits contains 1, assembler 8051?

texts:
I need to know how to check whether a byte contains a 1 for touch status in a MPR121 project, so if:

  00000010 then pin 2 is touched
  00000100 then pin 3 is touched

How can I detect it?
A set bit means that a pin is touched. It does'nt matter whether there are more bits set, I just want to know if there is any bit set, because that means that a pin is touched not caring which is that particular pin.

I tried
R1-byte container

CJNE R1,#0, hasone
hasone:
   ....

But I don’t know if this works since it is comparing a hex with a number, I can do it comparing with every single solution, but I don’t like the approach.


texts: L293D Motor driver 'braking' using input pins

texts:
I read the following on Wikipedia:

  Using pins 2 and 7 ( 15 and 10) to determine motor START/STOP or PWM duties it's dangerous, since there wouldn't be high impedance outputs: Current would flow back during the low semiperiod of PWM when the motor is turning.

Source: https://en.wikipedia.org/wiki/Motor_driver_L293d

I'm new to building electronic circuits and working on a small Arduino project. When I first connected my motor to the L293D motor driver my first thought on making the motor stop was setting both input pins low, which does indeed work. However, after reading the Wikipedia page; it seems like a bad idea.

What is the problem with not having a high impedance output and can someone explain what it basically means? Is it really that bad to brake using the input pins and should I use the enable pin instead?


texts: Flow of electrons when two charged plates are connected by wire

texts: I have kept two charged plates(one positive and one negative) in contact with one another.So excess electrons will flow from negative plate to positive plate.But then why  the wire joining the plates should also have free electrons?Aren't the electrons of the plates moving>?


texts: VCC on surface or inner layer on 4-layer board?

texts:
If I can get away with, I will use 6-layer design where I get two dedicated GND planes, L2 and L5, which creates strong reference plane for traces on L1, L3 and L6.

When you're working with 4 layers, you have no such luxury. If your board all runs from specific voltage, e.g. 3.3V, you're pretty much good to go, the n+1 bypass caps on all the devices tightly couple the VCC plane to GND. However, as often happens, you've got 5V, 3.3V, 2.5V, 1.8V and what not. That  obviously creates a mess of copper flood edges on the power plane. Sometimes you may be able to stitch the power planes together at point of traverse or route traces entirely around the plane gap but this is not always viable.. Ideally you'd also like a stitching cap where you change AC traces between GND referenced and power referenced planes.

Would using surface layers for power be a reasonable alternative to using dozens of stitching caps? The only downsides I see is some extra work creating the origami of copper flood carrying the power and perhaps some EMI issues if you're using e.g. cellular module.

Update
The stack-up is L1=>L2 0.1mm, L2=>L3 1.27mm, L3=>L4 0.1mm, which gives you 50R trace impedance with reasonable line widths.
Plane assigments are

Component / Signal /GND
GND
VCC (3 separate voltages in
this design)
Signal / GND

I have avoided traversing plane edges as a matter of course, but this still leaves the issue of signal X not being driven by voltage Y.


texts:
This is logical representation of gated S-R latch :

(source: ibiblio.org)
this is the symbol of it :

(source: ibiblio.org)
As seen on symbol, in Q complement output, there is an inverter. But in logical implementation, there are no inverters since we already got complement of Q. Why there is a inverter in symbol representation? Are both outputs supposed to equal to Q?


texts: Transfering RS485 data to server using ethernet

texts:
I'm extracting data from energy meters like V, I, KW, etc. Now I want to put this data in a dedicated server through Ethernet LAN so that meter user can monitor data from remote place by logging in to particular server address. I'm thinking to buy TIVA C series launch pad from TI.

My question is

Will the Tiva C series LP enough for it? or is there any other better option?
Refered http://forum.stellarisiti.com/topic/287-enc28j60-booster-pack/ Is it possible with Tiva C series?
How to transfer data to particular server? (Very noob in this section)


texts: How are LAN routers, WAN routers and eNodeBs connected to each other (TCP/IP)?

texts:
I'm new to telecommunication, and from what I understand, an user equipement is either connected to a LAN router or an eNodeB, and a LAN router is connected to a WAN router, and routers send the packets to the correct destination with a routing table. The part that I don't understand is how does all this work with IP/TCP? Let's say UE1 is a stationary device connected to a LAN router and sends a message to UE2, which is a mobile device connected to an eNodeB, how would that work? As far as I understand :

UE1 sends a message to the LAN router
the LAN router sees that the message is not intended for the local network, and sends the message to the corresponding WAN router.
the WAN router sends that message to the corresponding eNodeB
the eNodeB sends the message to UE2

Is this correct? Also, is I understand correctly, an eNodeB is basically a bounch of antennas with some software that can send/receive data from UEs in it's covered area, and a router does pretty much the same thing, so what are the differences between the 2 in terms of functionality (except that the eNodeB covers a wider area)?
Thanks


texts:
I am trying to understand how this older (~late 80's) vehicle sensor works in more detail.

It consists of a Air Flow Meter shown above... The copper arm rotates on a shaft connected to a flap, as the vehicle pulls in more air the arm rotates and moves along the voltage divider network.  All of the wires from this sensor go to the car's ECU.  What's interesting about this is the resistance across pins 7 and 26 aren't linear as you rotate but the voltage output is.

I was also interested in the current draw on the +5V source and output voltage wires.  So i utilized a current measuring tool and took measurements on two cars:

What I thought was interesting here is I expected the output signal (pin 7) to have very little current on it as I assumed it was going straight to the ECU's ADC.  The other odd thing is the large measurement difference here, used the same gauge, cars have the same ECU and AFM part #'s.

I decided to dig in and see what i could find on the ECU, picture below is the car's wiring diagram (left side) vs the Motronic 1.3 schematic.  Note that I believe on the schematic they have the two names flipped... Reason I believe this to be correct are two fold.  1.  The pin #'s are correct otherwise and 2.  I assume since the temp sensor (pin 44) is a NTC thermistor it would have a voltage divider as you see on the pin 44.

I'm not seeing anything on here that sticks out on why i'm seeing so much current on this voltage output (pin 7).  Any ideas?


texts:
What are the conventions for the direction of air flow for a fan? To state the question a different way, how can I determine the direction of air flow without actually applying a voltage to the fan? For instance, here's an image of a 24V DC fan.

From this perspective, I believe the direction of air flow is away from the table it is resting on (unfortunately this particular fan is dead so I can't test it). I've guessed this direction because the fan blades have a visible curvature to them that makes it seem like the fan blades would push air most efficiently if the fan spun clockwise (from this perspective) and air moved away from the table. The fan has a sticker on this side, but not on the other face. Is it generally true that if you're facing the side with the sticker air will flow toward you? I've also heard fans often have a small arrow on the side indicating the direction of air flow. This one doesn't, however. Are there any other conventions besides the 3 I've mentioned for determining the air flow direction without turning the fan on? Do AC fans have different conventions than DC fans?


texts: Help Duplicating Altium PCB Layout With Different Silkscreen IDs

texts:
I have the layout for a 3.3V switching regulator module and I also made a 1.5V switching regulator module. The 3.3V layout is very nicely done and I would like to replicate it for the 1.5V. However, the 1.5V has a different schematic sheet and the components have different names (start with 1 instead of 3, e.g. R115 instead of R315.)

I used a snippet to duplicate my 3.3V schematic and then added it to a new sheet and changed the designators hoping that it would preserve my layout but it did not. My question is, how can I duplicate the 3.3V layout but use the 1.5V designators and connect it to my 1.5V schematic so that when I make a design change it will update the correct section?

Thanks!

This is building on this thread: Altium: reuse schematic AND pcb layout

I have no experience using snippets so any help is appreciated!


texts: Questions regarding Triac Driver circuit

texts:
Sparkfun's EL Escudo Dos breakout board uses this circuit for an EL wire driver channel, with R2 = R3 = 330.
I was wondering what the function of  R2 and R3 is? Are they required? What would happen if they were simply replaced with a short?

EDIT: additional info
The HV lines are 110VAC and the channel will be driving EL tape (I think resistive and capacitive load?)


texts: Same Priority Interrupt on ARM Cortex M0

texts:
I have two two interrupts of the same priority; each has its own interrupt service routine: ISR_A and ISR_B.

When interrupt A occurs, ISR_A executes... what happens if interrupt B occurs while ISR_A is executing? Will ISR_B execute after ISR_A has finished? or will ISR_B never execute?

I am using a Freescale KL25z Arm Cortex M0+ with GCC


texts: Web-resources for learning how to read electrical circuits

texts: I would like to learn how to read electrical circuits. My final goal is to be able to develop some basic "smart" digital devices using microcontrollers. Could someone please suggest a nice web-tutorial on this topic. Thanks!


texts: What is the point of Buffers like this in Programmers?

texts:
So this is a schematic for an AVR Programmer seen here:
http://www.sparkfun.com/products/9825

On the bottom you will see a 74AC125 which is a Quad Buffer with Tri-State Outputs. I've seen quite a few buffers like this on programmers.....but im not exactly sure what they do? Im assuming whatever "CTL" is controls the "state" of the buffers.....but what exactly is the point? Why can't you wire it directly to whatever Port Line (Serial or w/e). Or does this have something to do with Impedance (Which Im not sure I STILL quite understand).

Is it because the Signals are coming out of the ATTINY2313 (or w/e MC is used) too fast and they need to be slowed down? I see this often when using a USB port of Serial Line....that one of these "Buffers" is used. What would happen if it wasn't there?

Or is this all just some sort of Serial Protocol Im guessing?


texts: Plotting a bode gain plot with the slope in Excel

texts: I am not an expert in Excel, and therefore, I want to know if there is a way of including the slope (dB/decade) in a bode gain plot in Excel or any free software (that allows to first input the frequencies and corresponding gain in dB, and then including the slope somehow)?


texts: Does "1KV" on this disc capacitor mean 1 kiloVolt?

texts:
One of my power supplies died. Investigation turned out that this capacitor is broken. "102" means 1nF, but does "1 KV" mean 1 kiloVolt or is that some sort of tolerance code?

I've tried several "capacitor code calculators" but none of them mentions "KV" (only K, which is indeed a tolerance code).


texts:
I have a special requirement on soldering which I do not know how to achieve. I now need to solder cable to large copper part, which require high solder power.

On the other hand, the temperature of the cable should never exceed 200 degree Celsius. Also, I cannot heat up the whole copper part to achieve melting temperature of solder because of it is fixed to another large object.

Does anyone have a hint to help me? Thanks a lot!!


texts: What is this adapter and what can I replace it with for simpler operation?

texts:
My church plant uses the D3540 pager - https://www.microframecorp.com/d3540-4-digit-wireless-visual-pager-display

We have to setup and tear down the pager system every week. We have to manually wire the 2-wire power connector into the green connector - shown below and at the link above - and it's a finicky/difficult process. The wire is always loose, and wiring is stressful for some of our setup team.

Is there some plug-in adapter replacement I can use to make this better? I'd love to convert it to just use a standard A/C adapter, but I'll take any improvements.


texts:
This is the first time I am building a DIY variable DC power supply using a SMPS and LTC3780 DC-DC Buck/Boost converter (5-32V input to 1V-30V 10A output). For most of my hobby projects 5-10A and 25-30V DC is sufficient. For the same power rating of 240W there are 24V and 48V supplies. I assume with 48V one I will have a bigger range of I & V combinations so it seems a better choice. However, I wonder about the voltage conversion efficiency. For 48V one, I will set it for 30V to be able to use it with the LTC3780 and then the buck converter will reduce it further as needed. So it will be 2x conversion essentially. Wouldn't it lose it's efficiency more than is needed?
On the other hand with the 24V supply there will voltage conversion once only and that will be by the step down converter. Besides if I need voltage higher than 24V the LTC3780 boost converter should accommodate it.
The price difference between the 24 & 48V supply is negligible. So which one would be a better choice? What do you suggest?


texts: What is the correct shunt size for the following ammeter and configuration?

texts:
I have the following ammeter:
https://www.aliexpress.com/item/Red-led-Display-Color-0-56-Digital-Ammeter-DC-0-100A-4-wires-3-digit-car/1301822575.html

The seller recommends 75mV 100A shunt be placed with it. I want to know what will happen if I change the voltage going through the shunt. Should I be changing the shunt as well to read amps correctly?

I want to build a 1-40V (or maybe 50V) adjustable DC power supply and use this ammeter to measure current. What the right value of shunt that I should use to get the right measurement? Changing shunts in a lab bench power supply is impractical, of course.

EDIT:
I am planning to measure only up to 5A or so. Sorry I forgot to mention this previously.


texts:
Here, the green waveform is the input waveform(V1) and the blue waveform is the potential drop across Vc1 and Vc2.
To me it seems like a peak detector getting clamped, but then the first half cycle and the second half cycle messes that up. Can this circuit be described as some basic electronic circuit?


texts: In the context of mains power, and wiring a light and switch. I thought I understood it, but what I'm thinking of I believe is something else called a "switch leg". Disclaimer: I'm a beginner with electrical.


texts: How to get rid of the warning "WARNING:PhysDesignRules:367 - The signal IBUF is incomplete."

texts:
I'm working on a simple neuron implementation on a Xilinx Spartan-3E starter kit and getting the warning in the topic. Can anyone explain me why I am getting this error?

My code:

module NeuronMdl #(parameter NUMBER_OF_INPUTS= 2) (
input wire[NUMBER_OF_INPUTS:1] x,   // Number of input bits.
output reg y    // Output.
);

reg signed[7:0] w[NUMBER_OF_INPUTS:0];  // Weights array, w[0] is bias so there's no input as x[0].
reg signed[7:0] yTemp;

initial begin   // Initial values for an OR Gate.
    w[0]= 8'h00;
    w[1]= 8'h01;
    w[2]= 8'h01;
end // initial

always @(x) begin   // Everytime there's a change in the input.
    yTemp= w[0]+ w[1]* x[1]+ w[2]* x[2];    // Need to find a way to generate this for varying input bits.
    y<= (yTemp> 0)? 1: 0;   // Output only 1 or 0.
end // always
endmodule

UCF file:

# slide switches
NET "x<1>" LOC="L13" | PULLUP;
NET "x<2>" LOC="L14" | PULLUP;

# leds
NET "y" LOC="F12";          # led 0

And the warnings I'm getting:

WARNING:PhysDesignRules:367 - The signal <x<1>_IBUF> is incomplete. The signal does not drive any load pins in the design.
WARNING:PhysDesignRules:367 - The signal <x<2>_IBUF> is incomplete. The signal does not drive any load pins in the design.
WARNING:Par:288 - The signal x<1>_IBUF has no load.  PAR will not attempt to route this signal.
WARNING:Par:288 - The signal x<2>_IBUF has no load.  PAR will not attempt to route this signal.
WARNING:Par:283 - There are 2 loadless signals in this design. This design will cause Bitgen to issue DRC warnings.


texts: Good ICs for receiving and decoding FM RDS

texts:
I'm interested in doing a project to read FM RDS data. Can anyone recommend good chips for both the FM receiver and RDS decoder?

For an FM receiver, I'd like to be able to control FM frequency (scanning of full range) from a microcontroller.

For the RDS decoder, I'm just interested in an IC that's readily available with a simple interface (e.g. I2C or SPI).


texts: Best way to step down (half) battery voltage for motors

texts:
I have a 4S LIPO battery 5800mAH at 14.8V and I want to use it to power some 7.2V motors I have.

The Rover 5 Chassis to be exact (https://www.sparkfun.com/products/10336), the only problem I have is I don't know the most efficient way to step down the voltage. I bought this battery to use with a quadcopter and I realy don't want to buy another one is there any way I can use this?

I know about regulators but that must be really inefficient.


texts: What is the use case difference/benefit of using a Gray code vs. Incremental rotary encoder

texts:
I am planning to build a small digital project where a rotary encoder would be ideal for sending "up/down signals" (e.g. scrolling through a list on screen).

Are there any benefits of using a Gray code vs. an Incremental rotary encoder for this case?


texts: absolute beginner: basic question - limiting the time of power output

texts:
I am completely new to Electrical Engineering (and english is not my mother tounge) so please be gently with me :)

take the following as given:

power source
LED
Switch (manual - nothing electrical!)

when the user presses the switch - event shall establish an power output for the LED, but it shall only output power for a given time (x milliseconds)

is it possible to accomplish this without a microcontroller?


texts: Is there a way to calculate the proper wire gauge?

texts:
I'm looking for the right copper wire gauge for my project.  I've found several charts listing the maximum current that various gauges, solid and stranded, can transmit.  The charts often disagree.  One says an 8 gauge wire with a stranding of "7" has an allowable ampacity of 95A, another says 40A, another says 150A, and another says 75A for a solid wire, but 20A for 43 strands.  I've found some charts that say stranded wire can handle much, much less current, and others that say that stranded wire "might not" be able to handle as much.  How do I know what the right answer is?  Is there a formula I can use to right the right gauge?

Specifically, here's what I'm doing:

Running a heater
12 volts (needs to be low voltage for safety reasons)
around 40 amps
maybe 10 meters of wire
on a mobile application, so must be stranded for durability


texts: Are Adafruit RGB 30 LED/m flexi-strips suitable to wear in large numbers?

texts:
I am working on a project that involves using a large number of LEDs on a single garment. According to my initial design, I would need as much as 1800 RGB LEDs. I have seen these LED strips from Adafruit https://www.adafruit.com/product/285. Since the strips draws 60mA 600mA per meter, and I would need roughly 60 meters, this amounts to a total of 36 amps. Using them would imply (I guess) either using dangerously high amps or distributing the current by using unacceptable numbers of battery packs. My questions are therefore:

I am correct in my assertion that using the LED strips linked to above is not realistic (i.e. 1800 ish LEDs on a single garment)? Or can I overcome this problem in any other way, as for instance by setting software limits to the PWN controlling the LEDs, thus limiting the current flowing through them?
Are there any other types of LEDs that would be more suitable? They need to be easily controlled by a microcontroller without additional circuitry, and ideally RGB.

(Updated text to show the maximum "current per meter" value, 600mA per meter, quoted on that Adafruit page, instead of the originally written value of 60mA per meter; this change has affected answers.)


texts:
I have a failed on EMC Test 300MHz and 500MHz due to crystal harmonics.
There is a lot of spike with a 25MHz harmonics.
The first picture is the Top of the Board and the 2nd is the 2nd layer underneath the Crystal and the third one is the Bottom FPGA.

My crystal supplies two ICs (CPU and FPGA).I suspect the problem was due to bad layout and long path of the crystal output.

I want to know if this is really due to the PCB layout that causes the crystal to radiate.
What are the parameters I violated? Your feedback would be helpful to debug this EMC issue.


texts:
I have a simple gadget (called "Fridgezoo") that talks when the fridge stays open. I always hated it, but my sentiments are with it (hey, it talks!) so I want to repair it.
What's the problem? It forgets the time. Normally, you set the time by a long button press, which tells it that it's morning. But it forgets it, and always talks like it's morning.
So I opened it up, hoping to see some parts numbers.
Overview images front and back:

As it's a timing problem, I suspect the crystal could have gone defect.
That would be this part on the PCB:

On the other side of the PCB, all looks fine to the eye (under a microscope, actually.)

I still believe it's the crystal oscillator. But what value? There is nothing visible on it.


texts: How to Raise and Lower an Object via Arduino/Photon

texts:
Completely new to anything dealing with hardware (Programmer person) and have no real clue as-to how I can accomplish what I want.

The goal is to be able to move an object up and down (Specifically a light).  The light will be fairly light, so weight shouldn't be much of an issue.

I found that a linear actuator does what I want, but seems to cost a decent amount.  Because this is something we want to give students, we'd like to keep the cost low.

The other option is some form of a motor.  Precision isn't something we need to worry about too much.

I know we have stepper motors, servo motors, and I'm sure their are more.  But I'm not too sure what I'm trying to look for when reading about these.

For example, how can I figure out how much force one of these can spin/move?

Is their any other way you'd recommend raising/lowering an object?  Any examples that have been done in other applications?  I've found some standing desk examples, but these aren't the best.

Thanks!


texts:
How can I size the circled capacitor in order to get rid of the peaking?
Is there some formula?
Cheers


texts:
I'm working on creating a relatively simple project where I'm using an Arduino as a remote garage door opener. Part of this project has a reed switch near the bottom of the door to detect when its closed.

My issue is this requires a pretty long wire run for the switch (probably about 10-15 feet). My dad does a lot of ham radio communications and as such the house has a ton of HF radio being emitted. I'm wondering how I can protect the Arduino from any damaging interference and still reliably detect when the reed switch closes. I found this article but I'm not sure if it'll help me or not. I'm sure I would need a ferrite bead and probably a twisted pair for the wiring but not sure what else I will need to protect the Arduino. Thanks!


texts: SystemVerilog import statement outside module definition

texts:
What does an import statement outside of a module (|class|package) definition mean?

Does it apply to entire file?

Is it even legal?  I don't see it in IEEE Std 1800™-2012.

It seems to be tolerated by ncsim (15.10-s008) - this compiles/runs w/o error:

package myPackage;
  integer  count  = 0;
endpackage//myPackage

import myPackage::*;

module a;
    initial begin
        myPackage::count++;
        #1;
        $display("%0d: %m: myPackage::count=%0d", $time, myPackage::count);
        $display("%0d: %m:            count=%0d", $time,            count);
    end//initial
endmodule//a

module b;
    import myPackage::*;
    initial begin
        count++;
        #1;
        $display("%0d: %m:            count=%0d", $time,            count);
        $display("%0d: %m: myPackage::count=%0d", $time, myPackage::count);
        myPackage::count++;
        #1;
        $display("%0d: %m:            count=%0d", $time,            count);
        $display("%0d: %m: myPackage::count=%0d", $time, myPackage::count);
    end//initial
endmodule//b

module test_package;
    a a();
    a b();
    b c();
    b d();
endmodule//test_package


texts: What's the purpose of the resistors and capacitors in this latching push button circuit?

texts:
I am trying to design a push button that turns my device on upon a single press and turns it off upon holding the push button for a few seconds.
I found this circuit:

Aside from the 10uF capacitor and the 300k resistor which are used as a RC time delay for the press and hold to turn off effect, what do the rest of the components i.e. the 10k, both 100k resistors and the 1uF and 0.1uF capacitors do?
Also, my device runs on 3V3 power so I'm not sure if it will still work with these component values, which is why I'm asking the above question.


texts:
Can anyone explain to me why the node voltage between the collector of Q1 and R1 have its signal amplified while for Q2, the node voltage at R3 and emitter does not have its signal amplified? I read on internet, the Vce of transistor must be biased correctly, in both case, Vce across Q2 and Q1 is about 6V? Also I calculated the value of bypass capacitor by consider input impedance viewed from the signal side.
So far my understanding for the working principle is as below:
a) Consider Ib present at the base of Q1 and Q2 and by consider there signal source following across the base as well ie.,(Isinwt) then the resulting base current will be Ib+Isinwt, which we will get an alternating base current which will then amplify through Ic.
Am I correct? if so, why signal at Q2 does not get amplified?

simulate this circuit – Schematic created using CircuitLab


texts:
I need a sensor to measure the distance between itself and an object (which is my finger). What is a good sensor that can accurately measure such distance within about less than half a meter?

I think it would be an infrared sensor or an ultrasonic sensor.

Also I need it to sweep as much horizontal distance as possible. I need to stack them beside each other to cover a plane.

Edit: The horizontal distance is about 30 cm. Also note that it shouldn't be too expensive and the quality needed can be "not so perfect" it's okay. Assume it's for an experiment.

My question is mainly about what type of sensor should I look for

...if a finger is too small for most sensors, then it's okay to replace it with a bigger object so that the sensor can detect it.


texts: ATmega328 with Optiboot not compatible with Arduino?

texts:
I recently purchased a number of ATmega328 chips loaded with the Optiboot (Arduino Uno) for some projects I am working on, but I have noticed something strange with them. I already have plenty of Arduino boards in my collection, but this time I wanted to make a very barebone Arduino-based project with a small component count.

Think something like Arduino Sleep Watchdog Battery.

With all the chips I also ordered ZTT 16 MHz resonators.

But if I power the ATmega328 and connect an LED to D13, the ATmega328 will power up and flash the LED, but at an ever increasing rate, and then it stops flashing after about three seconds.

Thinking that it might have been my wiring, I tried using the ATmega328 chips in my other Arduino boards and noticed that same thing. Thinking that it might just be a a bad chip, I have tested three chips in different boards, all with the same issue. Just in case I had a bad component blowing the chips, none of the ATmega328 chips have touched a component that another faulty chip has.

If I try to upload a sketch I receive a "not in sync" error, and it fails to upload.

All chips look to have come from SparkFun/LBE. One of the chip suppliers told me that there is a bad batch from SparkFun, but I can not find anything to back that up.

Thinking that the bootloader might be corrupted I set up another Arduino as an ISP programmer, but it kept giving me errors and returning the chip signature as an ATmega168 (peeling back the label I have confirmed the chip really is a ATmega328P-PU), but as this was my first attempt at using an ISP programmer I put this issue down to user error (me) and ordered a ready-made ISP programmer (yet to receive).

How can I fix this problem?


texts: Is it safe to make common ground between multiple voltage planes

texts:
I have a system where I have two power inputs and a single power output. One input from a battery(13v, 10A max) and one from solar cells(19v, 10A max). Then there is an 12v output which I connect to a power supply that steps down that 12v to 5v to be used for single board computer and some LEDs.

What I want to do is connect the grounds together. So both the two input grounds and the output ground are connected. I want to do this because I'm creating a system where the power rails have to go over a power connector and if I can let these grounds go over a single pin then it will save me a lot of headaches with the amount of power pins I need.

In addition to this I wonder what kind of rated current I would need for my ground wire/pin. Would 10A(the max of each individual input) suffice or would I need 20A(Sum of both inputs)?

Any help is appreciated!


texts: What happens when a 4-20mA sensor is connected in reverse to receiver?

texts:
simulate this circuit – Schematic created using CircuitLab

I need to build a 4-20ma to 1-5v converter circuit.

I have a working model with a 24v supply and a 250 ohm resistor. Now I need to implement some protection features like reverse polarity protection.

I don't know what happens when it is connected wrong and how to protect against it.


texts: Is There a Way to Measure when a Ni-Cd Power Pack is Fully Charged?

texts:
For my battery-powered tool sets (drill, saber saw, jig saw, flashlight, vacuum, etc.) I have Craftsman and Black & Decker.  Both are 18 volt systems and both have approximately 20-volt "wall-wart"-type chargers.  Neither system would indicate when the battery pack was fully charged.  Both chargers have an LED that lights up to show "charging" but that does not indicate (by the light going off, or by any other means) when the charge is complete.  Instead, the owner's manuals say to "charge for at least 7 hours", or something like that.

The Craftsman charger died 4 months ago.  It suddenly went from ~20 vdc TO 3 vdc. The B&D charger died 2 weeks ago. 0 vdc.  This isn't the first, or even the fifth, time I've had a wal-wart-type charger die on me.
I bought an 18-volt WORX tool battery-pack charger (with a battery pack) for a buck.  It is a "desktop"-style charger and seems much more robust.
It charges both my Craftsman and B&D battery packs just fine.  The WORX charger has a (third-lead) thermistor so since the other 2 systems don't, I charge the Craftsman and B&D battery packs through the WORX battery pack so that the thermistor is happy.  That involves a spider-web of wiring:

It all works fine, but (finally, my question!) I want to know:  Is there a way to determine when the battery packs are fully charged, so I can plug in another battery pack to be charged?


texts: How do I calculate expected output voltage of car audio amplifier with given conditions?

texts:
I have a 4-Channel Amplifier rated at 800 Watt RMS per channel @ 2 Ohm load.  Channel 3 and 4 are preset to operate a subwoofer speaker while Ch 1 and 2 are set to operate mid-range speakers at reasonable operating frequencies:

Ch 1: Has a 2 ohm load (2 speakers @ 200 Watts RMS each wired in parallel) which is less than 800 Watt max for the channel
Ch 2: Has a 2 ohm load (2 speakers @ 200 Watts RMS each wired in parallel) " "
Ch 3: 2 ohm load (One 4-Ohm Dual Voice Coil Subwoofer rated at 800 Watts RMS and wired in parallel) - amp should be able to produce ~800 Watts RMS of power to this Subwoofer speaker that is also rated at 800 Watts RMS
Ch 4: Currently has nothing connected to it

First, is this the right way to calculate expected maximum output voltage per channel? (Assume no speakers are connected)

Ch 1:  Power=(V^2)/Resistance  -> V = sqrt(Power*Resistance) = sqrt(800*2) = sqrt(1600) = 40 V (I am expecting 40 V at the output terminal of this channel)
Ch 2: Is wired the same way as Ch. 1
Ch 3: Is wired the same way as Ch. 1

When I ACTUALLY measure the AC voltage output I get the following on a voltmeter that is set to AC Voltage and speakers are connected:

Ch1 reads [0V-6V] as I tune its gain from [nothing to maximum] at 1000 Hz tone
Ch2 reads [0V-6V] as I tune its gain from [nothing to maximum] at 1000 Hz test tone
Ch3 reads [0V-27V] as I tune its gain from [nothing to maximum] at 50 Hz test tone

As you can see, all of the voltages read are less than what is expected if I am correct. I am in fact getting sound from my entire system but I feel that I am not getting the maximum output before distortion for my subwoofer. In other words, I feel that I am not getting 400 Watts out of the subwoofer @ 50 Hz test tone. All power ratings given are in RMS.

Is the value read from AC voltage on the multimeter Voltage peak to Peak, Amplitude, or RMS Voltage?
Is my method for calculating expected voltage per channel correct?

I can't find any resources online to help exactly help me figure this out. Any help would be much appreciated.  Please let me know where I could be going wrong with the mathematics, wiring or what the right way to set this system up might be.

Thanks.


texts: Relation between bandwidth, response time and disturbance rejection for a control system

texts:
I read the following line in a control system book:

Higher bandwidth corresponds to better command following, disturbance rejection and sensitivity to parametric variations. On the other hand, achievable bandwidth is limited by presence of noise and dynamic uncertainties.

Can you please explain how " Higher bandwidth corresponds to better command following, disturbance rejection and sensitivity to parametric variations"


texts: I need help with identifying connection scheme of this rotary encoder. I have no datasheet and there is nothing specified on the body except "CTR".


texts: placing hermetical packages on PCB and soldering

texts:
I stumbled upon some hermetically enclosed packaged - Link.
The package has a small bulge/projection on the bottom. This makes the package leads basically float without contact with the PCB. How do we solder such pads on PCB ?. Also, this bottom extension, how is it placed on the PCB ? Will there a small hole or slot or such thing to house this bulge ?

The screenshot is as shown below -


texts: Need help on a DC motor-PWM-SMPS setup (Does a PWM help overcome a DC motor's initial startup current surge?)

texts:
I am trying to build a DIY one-way peristaltic pump with a 12V 100W DC motor
(possible candidate :
https://www.ebay.com/itm/DC-12V-100W-13000-15000rpm-775-motor-High-speed-Large-torque-DC-motor/352550303190)

which will be controlled by something like this PWM controller (10-50V, rated for 40A continuous & 60A max current)
(https://www.ebay.com/itm/DC-10-55V-12V-24V-48V-30A-PWM-DC-Motor-Speed-Driver-Controller-Soft-Start-Switch/322616619257)

and will be powered by an SMPS supply such as this 12V 20A supply
(https://www.ebay.com/itm/AC-to-DC-240-Watt-12-24-Volt-20-10-Amp-LED-Driver-Switching-SMPS-Power-Supply/183703093948)

So my question is:

Will this setup work?
Is either of the PWM controller or SMPS supply overkill or underwhelming?
If this setup works, is it because of the PWM?

I ask because I've heard that DC motors draw 5~10 times their normal running current when they start up, so such setups involving SMPS power supplies may regard the initial current spike as a problem and may fail to 'turn on' properly, but a PWM helps with that problem.

But my understanding is that a PWM turns the flow of electricity on/off really fast so as to modulate the total electricity passed through but the current load (amps) stays untouched, so I'm not really sure what happens here.


texts: Regulating voltage so USB works with module

texts:
I recently purchased this GSM/GPS module.

I would like to power this module via a USB cable but can see that it has varying input voltages.

So bearing in mind that USB is 5V and that I'm an electronics newbie (I've only worked with evaluation boards that regulate the voltage for me), I'm not sure how to proceed.

On the site it recommends the following voltages:

GSM: 3,2 ~ 4,8 V
GPS: 2.8 ~ 4.3 V
VCHG: 5 V

I assume 'VCHG' has something to do with charging. I can't see any battery in the schematic below so I'm not sure what that's used for but I can also see that 'TEMP BATT' is pin 2. It also has an ON/OFF switch on pin 1, is this a red herring?

If VCHG won't help (I had hoped that would be some form of input that would regulate the voltage for me but I'm not sure), what's the easiest way to reduce the voltage down to the recommended amount? Should I aim for half way between the varying voltage values? Also, if I was to use GSM and GPS, do I only need to power pin 17 (GPS) as it appears that they connect after the R13 resistor.

The datasheet for the SIM928A can be found here.


texts: How would a NOT gate be implemented by Josephson Junctions

texts:
I'm interested in learning how Josephson Junctions can be utilized to create invertible logic gates. To me it's not clear how the Junctions provide any logical capability (they simply allow for a current flow across an insulating channel but lack any switch type mechanism).

Link to Josephson Effect: https://en.wikipedia.org/wiki/Josephson_effect

Does anyone have a circuit diagram of a NOT gate implemented purely using josephson junctions and wires? I'm hoping to find something similar to the famous CMOS not-gate diagram below: (source: https://en.wikipedia.org/wiki/Inverter_(logic_gate))


texts: Power consumption LCD display on digital watch 12h/24h

texts:
just a fun question:
When I was a child, I thought that displaying my casio F91w in 12h mode rather than 24h will make my battery last longer since there are fewer segments displayed.
when i saw this graph i realized it wasn't that simple.
Does the energy consumption depend on the number of segments displayed and does switching to 12h mode increase the battery life?
Was i wrong as a child?
on the graph, we can see that the consumption of an on or off segment seems the same. Is it true?


texts: Designing PSU: PSU Curent Limit Latching issue

texts:
The circuit below shows a part of a circuit that I am designing for a PSU. This is the first time I do anything even remotely this complex. Video playlist for context. Direct Link to the Testing discussed below

The problem I have with the circuit below is that as soon as the circuit goes into Current Limit mode, it pushes V-Out up to about 8V, and I cannot recover from this, even if I set the current limit much higher than where it initially latched. The only way to recover from this is to un-plug the circuit and then reset.

(Note: Original Schematic improved for better readability as requested by Rohat Kılıç and replete)

What I think is happening is that when we go into Current Limit mode, and Q1 turns on, OpAmp (IC3A) tries to compensate for its output being pulled to ground, and somehow drives 8V across... Actually no... If Q1 is on, surely the maximum voltage that it could show would be 0.7V, no? How is that OpAmp able to sustain more than 8V with its output shorted to ground?

Some context

I-Sense senses the Current over a shunt resistor and can be 0-3V.
I-Set comes from a DAC with an upper reference voltage of 3.0V
V-Set comes from a similar DAC with the same 3.0V reference voltage
V-Out is the input to an LT3080 Linear Voltage Regulator and could range between 0 and 30 Volts
CLIM is purely a digital input to a micro controller to let it know when we are in Current Limit mode.

Before we go into Current Limit mode, everything seems to be working as expected.

Note that I am testing this with no load but there is a 10mA current source connected to the output of the LT3080 as stated by its spec sheet to allow varying the voltage down to 0V.

Update

@user55924: The Image below is what I see of Pin 1 of IC3A when the output is at about 1.7V. Is that expected? I would not have expected the pulse. Does this mean the V-Set signal is not smooth enough? Testing with a standard Arduino Mega PWM smoothed (somewhat) with a crude single stage RC filter. IC3B is off until it latches and then goes to VCC (34V in this case) as expected.


texts:
I recently bought this wifi module.

Connected it to my pc and set it up according to the example provided. Thinking that it was just plug and play(as advertised) I hooked it up to my Arduino Uno, turns out this was not as easy as I thought.
I then tried to set it up according to the manual(found here), but I had no further success with this method.

On the wifi module, there are three leds. When led3 is blink, it's indicating that wifi link has been achieved. I can only get led3 to blink when using Auto Workmode when setting up the module.
As far as I can tell, even though led3 is blinking, there is no actual connection to the module.

Is there some way I can confirm that the module is infact online? I have tried to ping it, but it returns "unreachable host" but that could be due to some config error on my side.

TL;DR: I can't get my wifi module to work, how can I check that it is online?


texts: Trigger Relay Only from one specific grounding path?

texts:
I have a car wireless door lock system I want to modify. The basic operation is that when the key fob's button is pressed, a light relay is triggered, to flash some of the car's lights, to indicate the doors are locking. It does this by grounding a pin attached to the relay. This same relay is used on multiple systems.

I want to add a second relay, that only triggers, when the wireless door lock system triggers the light relay, not when anything else does. General schematic attached. (Red wires and New relay is what I know I'll be adding).

simulate this circuit – Schematic created using CircuitLab

Any of the nodes labeled "Switch" "Alarm" or "Misc" can ground the relay, turning on the lights. If I simply tap into the circuit as shown, that would make the new relay trigger as well, and I don't want a 24/7 horn blasting.

Obviously, I only want the New relay to trigger, when the WDI grounds the Existing relay. How can I do this?


texts: Is there a way of telling if the connector is male or female on a schematic?

texts:
For example, in the RS232 here:

or here:


texts: How to run a 6v 4amp motor at slower speeds for long periods of time (2 hrs)?

texts:
I am trying to get a project done for Halloween.  I am running a 6V 4A motor (from a powerwheels) but need it to run slower.  I tried using an adjustable charger and ran it at 3V to slow down the motor but it wasn't turning the motor because the amperage on the charger is less than 1.  I need to run the motor for a long period of time which is why I am not using the battery that is designed for it as it will only run for maybe 30 minutes.  What are my options for this.  The only charger I have found at 4 amps is a 16V charger.  How can I achieve this, what are my options?

thx


texts: Proper inrush current limiter 50A universal motor

texts:
We have one dental equipment with one universal motor  in 2000W and 220V range shown below:

And we gave two corruption in selled device to customers which have inrush current problem by switching the universal motor, so one of the switch poles has been burned like this ( 220V 16A):

And

So i searched the internet for solution and seen the ntc in this inrush current :

2200÷220=10A >> 3×10A ~ its inrush current!!

Like MS35 NTC with this shape:

But it is expensive (~5 €), so what is any other way with ...?

Thanks for your attention.


texts:
I have been trying to build a simple PWM power supply to use a 3.7v battery to drive a small heating element with a DC resistance of about 1 ohm.  I have built a slightly modified version of the following LT3759 based circuit:

(source: linear.com)
I modified the circuit for an output voltage of 5.0V.
I have no problem getting the expected behavior from the circuit on my scope with a large load, in the kOhm range.  When I try to drive the heating element I want, the voltage drops to about 400mV.
I suspected this might be some sort of impedance issue, so I put a simple voltage follower with a mosfet at the output, but this failed to resolve my issue.
Does anyone have any insight as to why this is happening?  I am guessing it is something trivial that I am missing due to my lack of background in this area.


texts:
I was attempting to make a mini UPS for a raspberry pi. The (relevant) bill of materials goes as follows:

250V/50Hz AC to 5V/5A cctv power supply
A 2-port mobile powerbank (i.e. it can charge two phones simultaneously)
A 5V DC sugar cube relay
A capacitor - 4700 micro farads

They are connected as per this schematic:

The working principle is as follows: When there is AC supply, the 5V DC will activate the relay. This closes the circuit wrt the cctv powersupply device; the rpi should boot properly; and the powerbank should charge. When the AC powersupply is offline, the relay deactivates (i.e. enters the NC state). In this state the circuit should be (theoretically) closed wrt the powerbank's output; the rpi should boot properly. During the "switch" there is a momentary dip in the rpi's powersupply. This is taken care of by the capacitor.
Somewhere during breadboard prototyping phase, I noticed that I didn't need to ground the output of the powerbank. In other words, the powerbank's output was grounded through the GND of the powerbank's charging port. At the time, this made me assume that this is the norm. I decided to design the circuit likewise, and, implemented on a stripboard.
However, on the stripboard, my experiment failed. I observed the powerbank wasn't supplying output to the target device. Since, the circuit wasn't closed like I thought it would. This could be because of the powerbank being used was a different one - not the same one used during the prototyping phase. Perhaps this could be a feature of powerbanks with passthrough charging feature.
Hence, moving on, I decided to make a connection between my target device's GND to the powerbank's output GND. I connected pin2 of j2 to pin2 of j4.
Now when the mains supply is offline. I am unable to observe the actual order - but the following happens:

The relay momentarily jumps to a NO state.
The rpi momentarily tries to power on, but as soon as I hear the relay's click the pi looses power supply.
Same is the case with the powerbank output.
The powersupply device, has, an indicator LED on it. In its normal operation (i.e. when it is supplying DC from the AC mains) it turns on. But in this case, there is not AC supply. But it turns on momentarily.
I am unable to discern whether the actual number of relay clicks. (one or two).

I am still unsure why this happens. Hoping someone can correct the defect.


texts: Can I use a multilayer ceramic capacitor instead of a ceramic disc capacitor with the same capacitance (0.1 microFarad)

texts: I want to build a 'Drawdio' Musical Pencil,(link to the make-project) but my local shop doesn't have the correct parts as originally used in this project. He doesn't have ceramic disc capacitors of 0.1 micro Farad, but he does have multilayer ceramic capacitors of the same capacitance. Can I use these capacitors or are the functionalities of both capacitors much too different?


texts: Regulated Cascode TIA using a voltage amplifier with negative gain

texts:
I am reading this article.
Why in the article is it said that the v_sg increase when vx increases?
well, why does it use v_sg instead of v_gs for NMOS in the first place?
As I see it, VY must be larger than VX to keep M1 and M3 in saturation.
So, when VX increases --> VY decreases --> v_gs M1 decreases --> ID M1 decreases.


texts: Is it possible for snow covering a car battery to drain the battery?

texts: We had a snow/ice storm last night, and somehow the snow got into the engine area. Is it possible that the snow covering the battery was the case of draining the battery?


texts: What is the name of the following cable?

texts:
Instead of wrapping cables I will like to make the connection by using the following type of cable:

what is the name of the female and male cable with this circular end? I will like to buy this type of cable so that I can connect and disconnect cables in an easier way. Without the name I cannot seem to find it on google.


texts: What's the purpose of adding a parallel impedance to a relay circuit?

texts:
This is the relay section of a PIR Sensor I have taken apart.:

L_FUSED is 240VAC, and the relay is intended to turn on a light bulb from "OUT" (standard edison screw), so it could be incandescent, fluorescent, or LED.

What is the purpose of the designer adding an impedance parallel to the light bulb load, which is purely resistive? My thought is that in case there is no load connected, switching the relay on may cause arcing if there is no impedance connected - however I'm not sure.

Thoughts?


texts:
I am trying to create a D Flip Flop to use in a bidirectional 4-bit shift register, using Logisim. However, when using my D flip flop the shift register acts just as a normal register setting the bit for all 4 D flip-flops outputs instead of one by one. It works properly when using the D flip-flop provided by Logisim but I am wondering how to achieve this using my own D Flip-Flop.
This is the design of my D Flip Flop

And this is the shift register (with the boxes representing the D Flip Flop)

Any help would be greatly appreciated


texts: Would an RF amplifier be required for an indoors antenna connected via coaxial cable to an outdoor directional antenna (900/1800 MHz)

texts:
Sorry, couldn't make the question title any shorter without losing meaning.

So, I'm looking to build an outdoors yagi antenna that's connected to another indoors antenna via coaxial cable. The purpose is to get better cellular coverage inside the house. The outdoors signal strength is about -81 to -73 dBm, while the indoors signal strength goes as low as 103 dBm to no coverage.

I've looked at several commercial solutions, but all of them have a bidirectional RF amplifier between the two antennae.

I was wondering if this would work without an RF amplifier between the antennae.
I've looked at several DIY projects that are related to (but not exactly) what I want to achieve. Here's one: http://my-homemade-diy.blogspot.com/2012/07/diy-cell-phone-gsm-3g-signal-booster.html

The above linked project is delivering the cellular signals only to a small area inside the house. I want to do essentially the same thing except with the signals spread out over a larger area, say, 20 cubic feet. Is it doable?

Apologies if my question is missing any information that I should have provided. Any response is appreciated.


texts: Charging battery with external charger while powering load

texts:
I am building a device which I would like to be able to charge with several different types of external battery chargers (different Icharge within spec of battery, of course). If I understand everything correctly, I won't need an extra charge IC on my board with this setup.
Now, while this device is charging I would like to still be able to power the loadside logic.
What is the best way to do this? Should I add a source selector and only use current provided by the charger to put in my on-board DC/DC during charging? Should I add a load sharer?
Or is it sufficient to just power everything from Vbat even with the charger plugged in and pull the 20W required for the logic from the charger like that?
Either way, isn't the charger constantly detecting current draand "thinking" the battery is not full yet potentially detrimental for the battery?
Thanks!


texts: I'm new to PCBs and I'm working on a project in which I'm dropping ~22.8V across a resistor. I'm using 0.5W resistors (they'll be dissipating about 0.43W with my application). In my prototypes the resistors get fairly warm, and I'm wondering if a heat sink wouldn't be a bad idea. Additionally I could end up with up to 5 of these resistors and if several are on at once, it concerns me that they'd be able to overheat each other. What's the best way to sink the heat off of these guys? Would a something like this be appropriate?


texts: ESD sensitivity of P-channel MOSFET vs N-channel

texts:
It is well documented that N-channel MOSFETs are extremely sensitive to ESD damage.  I've personally killed more than one.

Are P-channel MOSFETs just as sensitive?  I'm thinking that, since the gate sources electrons rather than sinking them, it wouldn't be, but I don't have the background to confirm that.


texts: How can I make an ideal comparator in LTspice?

texts:
For fast simulations I sometimes need an ideal comparator.
I guess it is not a built-in component.
How can it be implemented by ideal sources or VCVS ect.?


texts: I have this circuit and I am not sure how to create the bode plot and the actual bode plot.


texts: Xilinx XPS : On what bases the AXI master changes AWSIZE/ARSIZE....?

texts:
I have built my system with AXI interface using AXI4 From XILINX PLATFORM STUDIO(XPS).

I used 32 bit data and address buses.I am facing problem with respect to xSIZE.

In firmware(SYSTEM C), I have 8 bit, 16 bit and 32 bit Read/Write operations.Based on the Read/Write width, The AXI xSIZE has to be changed. i.e For 8 bit(type- char), 16 bit(type- short) and 32 bit(type- int) Read/Write's, the AXI xSIZE has to be changed to 2'b00, 2'b01 and 2'b10 respectively.

My question is- Why AXI xSIZE is always set to 2'b10 by the AXI Master, Since we can't change/modify AXI Master...????

Please help us to solve this problem..


texts:
I am trying to communicate between 2 arduinos using 2 xbee shields. I am trying to configure the Xbee shield with PAN ID, address etc. I am using X-CTU utility on a windows 7 64 bit operating system. I am able to configure one of the XBee modules with all the necessary parameters. I am not able to repeat the same for the other module.

I able to communicate to the Xbee shield for the first 20 seconds. During this 20 seconds, the light on the Xbee shield is ON. The xbee shield responds to the communication query test and the serial number is verified. I am not able to repeat the query test after the light goes OFF. Is my XBEE shield broken?


texts: Part Identification, Board says C32 but it looks nothing like a capacitor and has 6/9 marking on it

texts:
First, I understand that you have to remove the components to fault find but this is just something to play with.
It's an internal HDD SATA adapter to USB3 with additional 12VDC for 3.5" HDDS. It worked for a day but then it failed. Now from what I can tell a short cct exists with the additional 12VDC cct. Doing a quick continuity and I get 0 ohms between +12V rail and negative rail.  Power pack has 12VDC, plug it into adapter no 12VDC.
The 12VDC seems to be straight through but with a few capacitors and I think the one 'C32' may be at fault. The problem is it doesn't look like a capacitor and has the markings '6/9'
Any ideas what it is or what I could replace it with .


texts:
I’m working on a project where a 7 bluetooth modules need to communicate with each other simultaneously. But i am unable to pair two bluetooth modules. Please guide me on how to make simultaneously communication between 7 bluetooth modules.

P.S. I am using hc 05 bluetooth modules.


texts: Is placing the ground in this small signal model wrong?

texts:
There is an example in a text where it shows the small signal model of a circuit.
Below on the left there is a transistor circuit and on the right its small signal equivalent:

I'm a bit confused whether I'm not mistaken about a point since in all editions they have the same example. Is the ground connection where I put red question mark wrong? It seems to me there shouldn't be ground there, is that correct?


texts:
I've got the output of a CMOS IC (74HC4017 1-of-10 decade counter). It's output pins are either 0V or VCC.

The counter is driven by a slow clock (say, 1Hz). Now I want an LED on one of the output pins to flash, but only briefly (say, 1/10th second) when an output becomes high (or when it becomes low, whichever is easier; it doesn't matter).

I tried putting a capacitor in front of the LED (Q0 -- C -- LED -- R -- GND) and of course the LED does flash… once. Then the capacitor is full and can't discharge, even when the output becomes low again.

I've been thinking and experimenting about this for a few hours now but can't come up with a solution.


texts:
I've finished designing my STM32f401 board, but I can't get the GPIO to work.
After looking for an answer on forums I still can't figure what I'm doing wrong ( Everything worked fine on the SMT32f103CEU6).

My "hello world" is just blinking a led :
http://pastebin.com/hCszBL3G

and here's the led pinout

Any idea ?


texts:
I'm trying to replicate this design and I cannot find the 6K/1% resistor in any online store (Digikey, Mouser). What can I do? the design I'm trying to replicate is this

As per @Huisman request, all the resistors on the board are SMD, it also seems to be a 1005 package


texts: Is it ok to use a car battery to power an inverter?

texts:
I need a battery for low power inverter application but it seems that it's not easy for the following reason:

If i need 100 W output from 12v battery then i need to pull about 10A out of it(considering the losses). So if i need it to work for about 2 hours then that's 20Ah and considering the discharge rate of batteries then the final battery rate will be higher than 20Ah.

The problem is it's hard (for me) to get a battery with that amp rating with a good price and the only solution(as it seems) is to use a car battery since it has a high amperage capacity with a reasonable price.

Is a car battery is a good idea for this application?


texts: Why in 8085 microprocessor, the clock frequency is divided by two?

texts:
Why is it that the produced clock frequency is 6.144 MHz, but internally it (8085 processor) uses only 3.072 MHz. Also what leads to the specific value of 6.144 in a clock.

I found an answer at yahoo.... http://answers.yahoo.com/question/index?qid=20080810090119AAurr2i

but I must admit I didn't still get it it well. Could any of you guys throw out a few lines on this, please?


texts: This lamp require 12V AC and i am trying to supply power to it safely. When testing with 12V DC adapter it seems to work but i also have unused 12V transformer that i hope to utilize for this project. Besides the transformer, is there anything else i need in order to provide the adequate power to the lamp safely or is it completely fine to just use the 12V transformer directly?


texts:
I am looking to solder this 19 pin hdmi cable with small wires (possible a single wire) to convert it to another connector.

I expected the connector to be a have bigger spacing between the pins. How do I proceed with soldering this? If I can get a PCB Board, how would I actually solder this without touching one another?
I have never done soldering this tiny before. Any help would be appreciated.


texts: VHDL Use of variables vs signals inside a process

texts:
I'm implementing the double dabble method (https://en.wikipedia.org/wiki/Double_dabble). Every cycle if a BCD(binary coded decimal) digit is > 4 then add 3 to it. Regardless of the addition there is a left shift, but the left shift is after the addition.

Because this seems too cumbersome to put in one statement I want to break it up. AFAIK breaking up a single statement should be done with a variable as I have done below, but I think a signal will also work as well. Is there a general guideline that says one is better than the other inside a process.

--this is a binary to BCD(binary coded decimal) converter
--it uses the double dabble algorithm from https://en.wikipedia.org/wiki/Double_dabble

--it takes a binary input of any length
--the length of the BCD is determined as 4*BCD_digits because every decimal digit in BCD takes 4 bits to encode
--it takes bin_len+1 cycles after go is asserted to convert
--first cycle pulls data, then the data is added and shifted bin_len times

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.numeric_std.all;

entity binBCD is
    generic(
        bin_len : integer; --length of binary input
        BCD_digits : integer --number of decimal digits in BCD
    );
    port(
        clk  : in  std_logic;
        go   : in  std_logic; --pulse to start dd algorithm. if asserted while dd is running it will restart and the previous data will be lost
        done : out std_logic; --pulse to signinfy data is valid

        bin  : in  std_logic_vector(bin_len - 1 downto 0);
        BCD  : out std_logic_vector(BCD_digits*4 - 1 downto 0)
    );
end entity binBCD;

architecture RTL of binBCD is
    type reg_type is record
        bin : unsigned(bin_len - 1 downto 0);
        BCD : unsigned(BCD_digits*4 - 1 downto 0);
        count : integer range 0 to bin_len;
    end record;
    signal r, r_next : reg_type;
begin

    sequential : process(clk)
    begin
        if rising_edge(clk) then
            r <= r_next;
            if go = '1' then --register inputs
                r.bin <= unsigned(bin);
                r.BCD <= (others => '0');
            elsif r_next.count = bin_len then --register outputs
                BCD <= std_logic_vector(r_next.BCD);
            end if;
        end if;
    end process;

    combinational : process(r, go)
        variable add3 : unsigned(BCD_digits*4 downto 0);
    begin
        done <= '0';
        r_next.count <= r.count + 1;
        if go = '1' then
            r_next.count <= 1;
        elsif r.count = 0 then
            r_next.count <= 0; --count = 0 is waiting state (1 to bin_len is run)
        elsif r.count = bin_len then
            r_next.count <= 0;
            done <= '1';
        end if;

        --if any decimal (four bit piece of BCD) is greater than 4 add 3
        for i in BCD_digits - 1 downto 0 loop
            add3(i*4 + 3 downto i*4) := r.BCD(i*4 + 3 downto i*4);
            if unsigned(r.BCD(i*4 + 3 downto i*4)) > 4 then
                add3(i*4 + 3 downto i*4) := unsigned(r.BCD(i*4 + 3 downto i*4)) + 3;
            end if;
        end loop;

        --left shift the result of add3 (and msb of bin)
        r_next.BCD <= add3(BCD_digits*4 - 2 downto 0) & r.bin(bin_len - 1);

        --left shift bin (lsb doesn't matter, but i use '0')
        r_next.bin <= r.bin(bin_len - 2 downto 0) & '0';
    end process;

  end architecture RTL;

I'm specifically asking about the variable add3, but other comments are welcome.


texts: Can a person suffer mild electrocution if he answers a charging phone with wet hands or sweaty palms?

texts:
This texas girl got electrocuted and died while using her cellphone in the bathtub. Can a person with wet hands or sweaty palms face mild electrocution if he answers the phone while it is being charged?

https://www.usatoday.com/story/news/nation-now/2017/07/11/texas-girl-electrocuted-while-using-cellphone-bathtub/467225001/

  A 14-year-old girl from Lubbock, Texas, died Sunday after being
  electrocuted in a bathtub while using her cell phone, according to
  local reports.

  Madison Coe was electrocuted after she either grabbed her phone that
  was plugged in or plugged in her phone, her grandmother Donna O'Guinn
  told KCBD-TV.


texts: replacing ceramic capacitors in a wifi router

texts: We had a thunderstorm a few days ago and our Asus DSL-N14U modem router stopped working. I opened it up and as far as I can see everything on the PCB is in good shape except two ceramic capacitors which have burst and on further inspection it also seems as if the inductor pictured in the second image also got damaged. I have looked for a datasheet or some piece of information as to what specification capacitors I should replace the damaged ones with but I come up with nothing. What type of replacement capacitors should I get?


texts: Questions involving Injecting power into WS2811 RGB strands

texts:
I'm currently using an Arduino UNO (but may need to switch to a MEGA due to memory issues) to control about 20 strands of WS2811 RGB LED Strings(see similar product here). I'm Using the FastLED library to send all of the data at once through a central data line. My questions are in regards to properly and safely injecting power.

I'm more of a programmer than an EE, I've done similar before but it has been years. For my safety I have a few questions:

When injecting power do I want to splice the positive and negative in so that the end of one strand is connected to both the new 5v line and the next strand(is this series with injection?)? or do I want to cap off the first strand and simply run the 5v from the power supply to the next strand(straight parallel correct?)?
What effect will the series vs parallel from the last question have on Amps?
I'm using a 5v 60 amp power supply. It has multiple positive & negative terminals. Does it matter if I run all of the injection wires off one positive and one negative terminal? or should I split them evenly across terminals?
The previous question probably effects the setup of my fuses? If I split the injection wires into 4 channels, should I then use four 15 amp fuses?
Am I missing any important safety factors?
I remember finding a simple (for kids) browser app that let you place nodes than showed the difference between voltage and amps. Does anyone have a link to this?

Sorry for all the questions at once, especially since I'm sure they've been asked before. Since this will be going on our Christmas tree, I'd like to be thorough.


texts:
We are designing a device with a USB 3.0 Type C port. It is a pure UFP device, so no role changing.

But I got confused when trying to understand how much logic there is needed. On a lot of reference designs there is shown a data MUX on the superspeed lanes on both sides (host and device), and the data MUX is controlled based on the cable orientation, which can easily be found using the CC pins.
But is a data MUX always necessary on the device side?
Or can we just connect the device superspeed signals to USB Type C superspeed lanes1.


texts: Digital command problems with AC/DC Common Ground

texts:
AC/DC Common Ground

On a model railroad layout I want to have an LED show "track occupancy".
The train (Maerklin) uses AC, both sides of the track are 'ground', the center is 'hot'.

I also want to connect a DC Regulated Power Supply with DC negative to the track, the positive to the LED.

By isolating one side of a section of the track a car completes the negative circuit through the wheels and the LED should light up.

The questions are:

Any problem with having AC and DC ground connected? The trains receive digital operating commands through the AC power connection.
Will the DC Ground have any detrimental affects on the train control?

Please note: Keep your answer simple. My understanding of electronics is minimal.


texts:
Basic question, but I have a doubt!

I have a pool heater that works from 240 volts. In order to calculate the annual operating cost, I installed a device that measures amperage and adds up the total consumption. The device measures by induction amperage and is connected to one of the 2 hot wires.

My question is: unless I'm wrong, the calculated total will only be for one of the two wires, so to know the total consumption of the water heater I will have to multiply by 2?

Say the appliance has calculated a total of 1000 kW/h, that would mean that my water heater actually consumed 2000 kW/h because it is connected to 240 volts?

Am I wrong ?


texts: Why don't capacitors have a minimum voltage rating?

texts:
First, this question is different than Does an electrolytic capacitor have a minimum voltage? since that question is about circuit analysis.

So, my question is the following:

Let's pick two voltages, a high one and a low one. Let's say 5kV and 30V.

Let's imagine a capacitor made for a circuit operating at 5kV; if the dielectric is too thin, the charge may jump across; so the capacitor is designed to keep charges with a 5kV potential apart.

But if the dielectric is thick enough to handle higher voltages, how can a lower voltage, like 30V, attract a charge on the other side?


texts:
I am trying to precisely measure cell voltage of a LiPo battery using a differential amplifier. The idea is to use an op amp to measure each cell voltage. I need to get a precision of about +-5mV considering that each cell differential voltage goes from 3 to 4.2V max but the input voltages in the op amp are from 25.2v (sixth cell) to 4.2v (first cell). Here is the circuit I am using with a LM324:

The output of the op amp goes to a micro-controller ADC. In this circuit the gain is 1.2 but I know resistors have tolerance so first I have a calibration step where I put a precise know voltage in the inputs of the op amp, I get the output voltage with the ADC and Vout/Vin = G so I get the real gain because of resistances variations.

But now I have a new problem, if I put 8.4V and 4.2V I calculate the gain that gives me for example 1.22. If now I put 9V and 4.2V gain is the same (1.22) but if I elevate or reduce the voltage even more let's say 15V and 10V the output doesn't responds to 1.22 gains, the total gain is now 1.29! I think this offset voltage I am getting (despite 2 to 3mV input offset of LM324) is due to bias current that are increasing as I increment input voltage is my assumption correct? If so, is there any relation between input voltage and offset voltage at the output according to the resistances in the circuit?

If my assumption is wrong, is any other way to reduce this error despite of using a precision amplifier? Because here are very rare and cost 5 times the price of an LM324 :/


texts:
After erasing the flash of a typical microcontroller with an ARM Cortex, I assume the flash contents to be all ff.

What is the behavior of the microcontroller after reset, especially that of its processor, in this case?

The only things I am reasonably certain about are these: Upon reset, the inital PC and the initial SP are set to 0xffffffff.

I am unsure what happens next: Is there an exception because the stack pointer is unaligned? Does the processor fetch an instruction from memory address 0xffffffff? If the instruction is fetched, is it taken from the two bytes (I think it should be a Thumb instruction because the initial PC has the low bit set) at 0xffffffff and 0x00000000 or does the instruction fetch access wrap around the "System" section boundary from 0xffffffff to 0xe0100000?


texts: How to ensure my device is safe for every day use?

texts:
I have put together a simple wake up light. It has an external powersupply, at the moment rated 7V and 600mA. Inside it has Arduino and bunch of LEDs controlled by a MOSFET.

It works fine at the moment but I would like to ensure that it wont burn my flat down while I am away. So far I have been thinking following features:

Fuse, rated somewhere below max output of the power supply
A decent heat sink for MOSFET. It gets warm without but doesn't burn my finger.

Anything else to consider?

Edit: The device is used in a bedroom. Not too much gas during night time.


texts: Data transfer from Cortex M1 to AHB slaves

texts: I am working on ACTEL Fusion platform which provides Cortex M1 softcore. Is it possible for AHB-lite slaves to access Cortex M1 memory. For e.g If my main C file has an array of unsigned_int 's. Is it possible to just pass the start address of array to a slave and the AHB slave can access multiple elements of the array at same time? All I want is to minimise memory writes to my custom hardware peripheral else it would mean 10 memory writes for passing uint x[10]. Is there any other workaround? The AHB-lite system contains coreMemCtrl,CoreAhbSRAM and CoreAhbNvm.


texts: Sparkfun QWIIC JST connector part number?

texts:
Sparkfun promotes and I2C connector defacto standard dubbed QWIIC®.   I'm looking for an orderable part number for the JST connectors that QWIIC is based on. I want to put them on a board I'm designing.
I've heard that these may be 4-pin SH connectors, and those seem close, specifically the 1mm spacing.   However, the Sparkfun pictures always show these connectors in black, while the JST SH datasheet says they come in natural (off-white).    Does anyone know for sure what I should layout for?
SparkFun Humidity Sensor Breakout - SHTC3 (Qwiic)


texts: I am building a plasma speaker using a 555 timer to generate the audio tone.  I am driving a mosfet with the output of the 555 timer, which in turn powers a flyback transformer to generate a plasma arc.  I have heard conflicting information about putting a resistor in between the 555 and mosfet.  I have heard that the resistor prevents over drawing current from the 555 timer.  On the other hand, I have heard that a resistor keeps the mosfet in a transition state for a long time causing the mosfet to dissipate additional energy as heat.  My mosfet is an IRFP460.  Should a resistor connect the 555 to the mosfet?


texts: Source transformation brings out a different result compared to other methods

texts:
High schooler here that just recently found out about source transformations. I wanted to try it out on a previous circuit we did using the good ol' KCL/KVL/Node/Mesh methods, but somehow, it gave me a different result. The circuit on the top is the original set up, with the voltage measured at R3 being -3.75V (correct answer). However, doing a source transformation around V1 and R2 results in the voltage at R3 changing to 24.5V!
I am stumped and may need an explanation on why the voltage changed when the source transformation technique was done properly. Or perhaps my technique was actually done improperly?


texts: What is meant by the term "galvanic contact" in this sentence?

texts:
Simply speaking, a switch or circuit breaker are two metallic contacts (electrodes) that are in GALVANIC CONTACT with each other when closed and separated by a certain distance when open.

I don’t really get what galvanic means in this contest. I thought the term galvanic was used in relation for a production of a direct current by chemical reaction (galvanic cell), but in a circuit breaker there is no DC electrical production, so what other meaning has galvanic?


texts:
Took apart an Apple TV due to no power from the smps and its like 80% covered in a white rubbery adhesive.

I'm used to seeing this stuff (or similar) on bigger components like electrolytic caps to minimize vibration but I'm curious it's purpose on the bottom of the board where it's all smd? Other than to make it really annoying to chip away to test components


texts: What transistor should I use to power a motor from an xbee

texts:
I have a small motor what operates at 3.3V at 50mA (sorry no documentation) and a Xbee radio which outputs 1mW.

I would like to allow the Digital I/O pins output on the Xbee to drive the motor though it is currently to weak. I've thought of these two solutions though I need help on either of them.

The Xbee Documentation says the 1mW output is "software selectable." I have XCTU which I've been using to get the Xbee's to talk. Is there an option is XCTU to change the Xbee's output to >1mW ?
Design a amplifier. I thought that maybe using a simple amplifier curcuit might work. I'm just not sure how to amplify the 1mW signal properly.


texts: I use eagle-cad 6.0. when I print the circuit layout onto PDF, it prints one circuit per page. However, my board has a small size and 4 layout could fit a A4 page without any problem. Could anyone tell me how I can print 4 copies of the layout onta a A4 page without changing the actual dimensions?


texts:
I have been messing around with TLC5917 LED Constant Current Sink Drivers and I don't fully understand how they work.

Because of how I was taught how Voltage/Current works, to my understanding, a voltage of 5V should be able to be measured between an active pin on the driver and a 5V source going through an LED.

What I measure however appears the be the forward voltage of the LED.
It is my understanding that current is drawn and voltage is "applied".

Since the driver is constant current, the behavior makes sense but how exactly does the driver supply the correct voltage?

Or is my conceptual understanding of how voltage/current work misguided?


texts: Does a universal motor run better on flat DC as opposed to pulsed DC?

texts:
After reading this:

Is there any advantage in running a universal motor on DC power?

I want to know, does it improve the motor characteristics if you supply the motor flat DC instead of pulsed (fully rectified) DC?

And what happens when you want to speed-control (e.g. PWM) these two methods, is there a significant advantage in those cases?

To conclude: what's the shape of voltage and thus switching-type that you can best use to speed-control a universal motor to maximize motor characteristics (less heat/noise/friction/wear, more efficiency)?

Thanks.


texts: The NCP51460 20mA Precision Voltage Reference with it's wide input voltage range of up to 28V seems interesting for our current project, more-so considering the very competitive current price at Mouser/Digikey/RS. However, I am worried whether the part will be available (Location Germany) in the future. I have I also have not found a replacement part of a different supplier yet. Can someone suggest a similar part with input voltage range of at >=28V, output >=3.3V @ 5mA and similar or better accuracy?


texts: Parallel inductive coupling approximation - coupling coefficient

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I have the problem of a few independent current loops (wires) that on a portion of the circuit are close to one another so there will be inductive coupling between them.

Each wire, on the portion of interest, has its self inductance and the mutual inductance will add to that because the currents have the same direction in this case (aiding inductors).

The problem is that there are many wires and any single wire will have partial inductances, with every other wire. The formula for partial inductance is:

Can the sum of the coupling coefficients exceed 1 ?  That is, can wire nr. 1 have a coupling coefficient of 0.6 to wire nr.2 , 0.4 to wire nr. 3 and 0.2 to wire nr. 4?

If the sum of the coupling coefficients of a wire to the rest can't exceed 1, then for this case of aiding inductors and same self-inductance for all wires, the maximum equivalent inductance (self partial inductance + mutual partial inductance) for one of the wires can't exceed two times the self inductance.

So, one could avoid calculating all the partial inductances and just use two times the self inductance as an upper limit of the inductance that can be on that portion.

Is this true?

EDIT: it's obvious now that the above assumption is not correct. I think this can be explained with the relative permeability of the materials, which is almost 1 for both copper and common insulators. Basically, the magnetic field goes through wires as if they weren't there.

In this case, could one calculate the mutual inductances for two wires as if the rest weren't even there? That would be a useful approximation, which I hope is the correct one now.


texts: PWM speed control of 24V DC Brushless Pump

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I would like to PWM speed control a 24V 2A DC Brushless Pump using an Arduino for my nano-brewery project. I've been searching for a Speed controller on Amazon or Ebay. But, i either find brushed motor controller or three phase controllers. I have only 2 wires on pump. Any recommendations on what I need to purchase? Thank you.

I need to control 3 pumps.

Pump I have: https://www.proflow-dynamics.com/media/catalog/product/cache/1/image/1200x/040ec09b1e35df139433887a97daa66f/w/h/whole_set_with_adapter__1.jpg

Power Supply I have: https://www.amazon.com/gp/product/B077XDC487/


texts: Diode bridge rectifier convert 13.5v ac to 17v dc

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i just make a voltage rectifier as shown below

Four IN4007S diodes

one 15k ohm resistance

one 25v 2200uF capacitor

I have a 220v->13.5v transformer, and transformer output is supposed to convert to a 12v DC signal by the rectifier circuit. everything just went fine, but strange thing happen about output value, it's 17.97v DC!! do you have any idea why output is so hight, while it must be about 12vDC!
I remove the capacitor and measure voltage of resistor and it was 12v, but when i put the capacitor, voltage change to about 17v! why is that?


texts: Some basic questions about an accelerometer's unexpected behavior while tilted

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I have an ADXL335 accelerometer connected to my Arduino.  Here is some code that I am running based off a tutorial:
    xaccl[a] = float(analogRead(xpin) - 345);
    yaccl[a] = float(analogRead(ypin) - 346);
    zaccl[a] = float(analogRead(zpin) - 416);

    float length = sqrt((xaccl[a] * xaccl[a]) + (yaccl[a] * yaccl[a]) + (zval[a] * zval[a]));

    Serial.println(length);

When the accelerometer is flat on my desk, the vector length is around 128.  When the accelerometer is tilted, the length of the vector increases even if it is not moving.  The 3d vector length should stay constant regardless of the angle.

Could someone explain what is happening?
Also, what unit of
measurement does the accelerometer output?  I assume m/s^2.
Lastly, some sample code I found for reading values:

    xaccl[a] = float(analogRead(xpin) - 345);
    yaccl[a] = float(analogRead(ypin) - 346);
    zaccl[a] = float(analogRead(zpin) - 416);

Why is the code subtracting 345, 345, and 416?


texts: PSpice model 1SMB5914BT3G temperature coefficient

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I'm simulating a circuit with a on-semi 1SMB5914BT3G zener-diode (3.6V) using LTSpice. If I increase the temperature from 27°C to 47°C the zener voltage increases from 3.6V to 4.26V @100mA.

PSpice Model from onsemi

Isn't that far too much? If I have a look at the datasheet page 4 I would expect approx. -1.5mV/°C. Is there an error in the spice model or am I using it wrong?