texts: calculating the size of a heating resistor

texts:
I'd like to use a ceramic heating resistor to keep a 4-5 cu ft insulated box above freezing on cold nights. A 15w heater belt is too much so I was thinking about using either a 5w or 10w heating resistor. Seemed like something I could eventually design a circuit to control the heat with a DS18B20 sensor and an Arduino.

Does the following look correct or am I missing something?

The resistor I looked at, a Riedon UAL-5, is rated for 1500 VAC. I assume I can run it at 120 VAC which is the RMS value for house AC.  I=P/V so 5w/120v = 0.0417 amps. R = V/I so 120v/.04a = 3000 ohms and that would be the size of the resistor I need to generate 5w?

Does the current need to be rectified?

PDF of a part I was considering which will mount nicely on a heat sink:

https://riedon.com/media/pdf/UAL.pdf

Thanks,
Dan

EDIT1: I've done some empirical tests with a 15w heater belt that I borrowed off of a friend and I know the insulation is good enough that 5-10w will be enough. It's the calculation for the resistor and question on rectifying that I was sure of. Not to mention that I can always move up in resistor wattage.

I appreciate the answers about area heating and insulation but I purposely didn't ask about that. I guess I should have said ignore the insulation and area heating as I can deal with that. What I really wanted was to understand the calculation and then I would buy the size of resistor I thought was appropriate. Now that I think about it I'll probably go 10 or 2x5 on separate switches.

I was going to use a grounded electrical box ventilation hold to contain the resistor and heatsink along with shrink tubing on the connections. I am aware of the cautions around using 120v.

I appreciate all the answers. Thanks Barleyman. Barley?


texts: Current transformer (CT) and potential transformer (PT) grounding

texts:
There is several documents say that for three-phase instrument transformers (CT,PT), there should be only one grounding point. With this argument, can I short the the secondary sides of current transformer and voltage transformer together on a bus-bar and then ground this bus-bar to create a single grounding point?

In fact, these CT and PT have already been installed at the substation and they are grounded, just not at the same point. My company will install a meter that uses their outputs. This meter have its CT and PT neutral wires connected on the circuit board and as mentioned, these neutral wires are grounded at their own points. So technically, the grounds of the said CT & PT are connected together. I'm asking if there is any potential danger to this.

Note that these CT and PT are used in measurement of High Voltage substation (110 kV).

Circuit to illustrate the idea:


texts: Maximum sample rate of Arduino Duemilanove?

texts:
G'day all!

I have an Arduino Duemilanove hanging around spare at the moment and thought I might try a few audio interfacing projects. I'm just wondering what sort of sampling frequency I can achieve using a single analog input and applying some simple algorithms on chip, then reporting using a few digital outputs tied to LEDs.

I'd like to sample in at ~44.1 kHz if possible.

For reference the first thing I want to try is a simple guitar tuner.


texts: 555 monostable circuit - triggering relay

texts:
I'm looking for a little help with regards to the logic required for a project I'm looking at undertaking soon.

I am looking at creating a 'quickshifter' for my motorbike. The way this will work is by breaking the ignition circuit(signified as M1 motor) momentarily using a 'normally closed' relay(RY1).

The problem I am facing is that the circuit will stay broken for as long as the switch (s1) is pressed. I am looking for a solution that will only leave RY1 open for a specific amount of time, in the 50-100ms range.

I would like the circuit to be broken for a maximum of 50-100ms; this is regardless of how long the button is held down. So for example. If I press and hold the button/switch, the relay will be trigged within the first 50-100ms, but not again until the switch/button is de-pressed and re-pressed.

What logic could be used in order to achieve this? Apologies for my incredibly crude diagram.

EDIT - I have tried to create a monostable 555 circuit as suggested, but I think I am missing something.

When I view data recorded when I run the circuit, I see some erratic current readings at Imeter1; and VMeter1 shows the voltage droping from 12v to 0v when the switch is activated.. nothing gets recorded across any other the other meter(IMeter0). Can anyone tell me what I've missed? Am I being an idiot?


texts:
I have designed a comparator with hysteresis using LT1719. When I apply no signal, at op_amp_2, I expect the output to be high. However I see a sine wave at the output.
This is the schematic of the circuit:

This is snapshot of the PCB layout:

I initially thought that since the DC levels at + and - are very near, this could cause oscillation when there is no signal, so I changed R19 to 10 Kohm. At first it worked as expected (output high 4.8V) then I applied a signal (at op_amp_2) and on removal of signal, the output started oscillating.

Could anyone suggest how I can fix this?


texts: WARNING: Can't resolve .param in LTspice

texts:
I am going to simulate buck converter using current mode control. I followed the circuit 2-80 from book
Switch-Mode Power Supplies: SPICE Simulations and Practical Designs, second edition written by Basso.
Unfortunately, I get an error from LTSpice WARNING: Can't resolve .param gi
does anybody knows how I can fix this error?


texts:
I am working on a project that requires the usage of a AD7656 16-bit high speed converter. This chip comes in a 64-LQFP package, which means the package is rather small. Because the prototype boards will be hand soldered, I'm using 100nF 0603 X7R decoupling capacitors in combination with 10uF 1210 ceramic, as a minimum recommended amount in the datasheet. I can't use smaller capacitors, furthermore the footprints are set on Medium density to make it possible to hand solder them.

Unfortunately there isn't a recommended layout specification of this IC available. I have problems routing the decoupling caps. It's impossible to place both the 100nF and 10uF together closely to the IC, whilst maintaining space for the signals (parallel bus, etc.) to get out as well.

Now I have got 2 choices:

I place the decoupling caps to the back of the PCB, which I don't use around the A/D and MCU for noise purposes.
I place the caps further away, but that might get to a distance of 5 cm.

Placing the caps to the back of the PCB seems like the easiest solution, maybe with paralleling 2 via's to the top to reduce the loss of the PCB. My question is, will this 'work' i.e. how will this affect the performance and noise? Or would I be better of keeping all of the capacitors at the top of the PCB?


texts: How does a lead acid battery accept more current when it is discharged than when it is charged if the resistance is higher when it is discharged?

texts:
I'm just trying to get my head around the above question. It doesn't seem to follow Ohm's law. Could someone please explain what I am missing in this?
Below is a chart I found of the changing resistance of a lead acid battery compared to state of charge, however, the charge acceptance is higher when it is discharged compared to when it is charged. How does this happen with a higher resistance that gradually gets lower?
I'm also assuming a constant charging voltage from an alternator.


texts:
I need to know why capacitor banks are rated in KVAr rather than Farads?

Suppose I have one capacitor bank of 10kVAr which is for a rated voltage of 400V.
Will this bank provide the same reactive power of 10KVAr at 200V? Ir will it change? If yes, how can I calculate how much reactive power it will provide at 200V?


texts: Finding functions for JK / D / T flip flops

texts:
I am trying to understand this concept of flip flops. Given some Karnaugh Map, all I need to know is how to find the functions of various flip-flop types:

sr flip-flop (\$s = \text{ ??} \quad r = \text{ ??}\$)
D flip-flop (\$D = \text{ ??}\$)
T flip-flop (\$T = \text{ ??}\$)
JK flip-flop (\$J = \text{ ??} \quad K = \text{ ??}\$)

I believe I know how to solve the sr flip flop but I am clueless about the others. I have created this random Karnaugh Map and solved for sr flip-flop.

If I wanted to explain it to someone I'd probably go with this:

In order to find s and r functions of sr flip flop, first mark all the bold 0s and bold 1s.

A cell is bold if the value inside that cell is different than the number of row that cell is in. (Here we consider only the a value of the row)

After you marked all the bold 0s and 1s, you need to group them.

All bold ones should be put into as large groups as possible. Only the bold ones need to be considered when grouping, however it is best to cover all non-bold ones if possible (as long as you don't introduce extra groups).

Here the result is one green group on the screen that covers all bold ones and as many non-bold ones as possible.

Then, the grouped ones correspond to s function. You simply calculate the Sum of Products.

--

Now the bit tricky part: do the same with bold zeros, that is group them into as large group as possible.

And now you can find the r function either as:

a). Product of Sums, and complement over everything

or

b). treat the grouped 0s as 1s (imagine they're 1s) and find
   the function using SoP, without any extra complementation over
   everything. The result is the same.

--

So to summarize: for sr flip flop s is function obtained by grouping bold ones (SoP) and r is function obtained by grouping bold zeros (PoS) and complementing everything afterwards.

I believe that's correct, Ph.D teacher confirmed that.

--

Now back to my question: can somebody explain to me like I am 5 years old how to find D, T, JK flip-flop functions from some Karnaugh Map?

For example maybe J = bold zeros complemented, K = bold ones. Or something like that.

Thanks~!


texts: Why is this relay turning on when booting up/down my raspberry PI?

texts:
I bought this relay from amazon https://www.amazon.co.uk/gp/product/B06XK6HCQC/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
I'm trying to use it to turn power on/off for a stepper motor I'm using. I've previously used a single channel relay for this which turned on when the signal was HIGH and off when the signal was LOW. It seems like this new relay works in exactly the opposite way. I'm guessing this is because the 4 channel relay is "active low".
It currently works if I just send LOW when I need to turn it on and HIGH when I need to turn it off, even if it seems counter intuitive to do it this way. My main concern is the relay is almost on when the raspberry pi is booting up for the first few seconds. By almost on I mean that the LED signalling me that the relay is in it's normal closed position is on, but not as bright as when I turn it on by sending the LOW signal to it. I don't think current is passing through it in this state. This almost on state also appears after I turn off the Pi with sudo shutdown now. As you can imagine, I would prefer the relay to be completely off in this state. Here's a diagram of how things are wired

I have also tried adding a pull-down resistor, although I'm not sure I'm doing it right. See diagram below. With this wiring, the almost on state mentioned above is turned into an on state, which is even worse because current is flowing through the relay from boot until I run the script and send a HIGH signal to the relay.

How should I wire things so that the relay doesn't turn on when the pi boots up/the script is not running/ pi boots down?
Less important: is there a way to turn on the relay by sending HIGH and turn it off by sending LOW?


texts: What are methods used to cool a small residential enclosure (cabinet)?

texts:
I have a cabinet in which I intend on putting the following:

A server
A switch
A MODEM
Other AV equipment

The cabinet is probably 30 cubic feet in volume. It doesn't have slots for ventilation - it only has the tiny cracks where the doors open. This is at a residence, not a business (therefore I only have 110/120 VAC).

I'd like to regulate the temperature of this cabinet, because I am sure stuff would otherwise overheat.

What are methods appropriate for accomplishing this? (If possible, I'd like to not make slots in the cabinet doors, for aesthetics).


texts: Is it possible to provide security in Passive RFID tags?

texts:
I am working on a project, where I am using RFID tags, and RFID reader for some sort of authentications.

But after searching for a while, I found that passive RFID tags can be cloned. Is there any way to make copy proof? (As far I know it is not possible.)

What logic should I use that won't allow duplicate card to not get access? (By using software or hardware logic.)

What is the latest happening in RFID and NFC technologies?


texts: What will be the behavior of this circuit?

texts:
i have a circuit for which i have simulated its output. But i can't seem to understand how it works.
Here is the circuit..

simulate this circuit – Schematic created using CircuitLab

For analysis purpose,
PWM source = 50% duty cycle with period of 20ms, and pulsed value of 2V.
Vin = 10 Vdc
Load = 1k
L1 = 1H
C1 = 1uF

Here is a snippet of waveform i got through simulation.

In above circuit,. I need to know the behavior of circuit. Like When Q1 is on what voltage appears at load and when switch is off then what happens??

I am stuck at;

1 - When Q1 is on, Vin appears at L1, and D1 will be open (reverse biased), so only path of current would be to C1 and Load through L1. But why doesn't any signal appear at load in this time?? why doesn't current flow from Vin to C1 or Load through L1??

2 - When Q1 is off, why does some voltage appear across Load, when there is no Vin because it is cutoff by Q1 switch?? and how does the current flow in C1+Load part, because there is only 1 wire connecting this part to L1 since D1 is open??


texts: Can I use a van battery with an invertor to power a food warmer?

texts:
I'm thinking of using an inverter for a food warmer (1700/2000W).

I'll be warming it up through the mains at first and then using the inverter for 30 min to 2 hours max.

Would be ok to run on a van battery (70 Ah)? Or will it flatten it very quickly?


texts: Powerline modem ST7580 single channel mode

texts:
I'm trying to implement a powerline module with the ST7580 modem.
There is a passive and active filter design in the application note laid out which I plan to modify according to my desired carrier frequency.

It describes a dual channel modulation, but i plan to only use one carrier frequency for my B-PSK modulation. Can I just adapt the filters to the same frequency?


texts:
I want to use a LM2940 regulator.
From the datasheet here , I can see that it needs a 22uf polorized capacitorfor Vout.
However the regulator is place before a 470uf tantalum capacitor, do I need to put the 22uf then the 470uf or can I just use the 470uf?


texts: DC/DC isolated supplies in series for higher voltage?

texts:
Can I chain two isolated DC/DC supplies together for a higher output voltage?  (Say, a 48V and a 12V to get 60V?)  They'd be fed from the same 24V DC source.

I've asked a related question before (Step up DC voltage from 12-24V to 60V), and I have a schematic from the NA Simple Switcher tool for a marginally adequate 60V supply.  (750mA, I will eventually need about twice that) I'm just getting back on this problem.

It occurred to me that there might be an easier solution, and it sounded like a good enough question on it's own...  so here it is.

The simplest thing I can think of would be to take a 48V 2A isolated DC/DC brick and put a 12V 2A brick after it. If I disable the 12V supply until the 48V is up, would that be good enough?  Would I even need to bother sequencing them?


texts: Is it possible to construct a voltage doubler that both powers an opamp and is driven by it?

texts:
I have an application in which I need to drive a MOSFET in saturation to create a constant current load. I'm using an opamp in a fairly straightforward feedback circuit for this, but the current the MOSFET can conduct is limited, since my opamp is running at 3v, limiting its maximum gate drive voltage to roughly the same (the opamp is the rail-to-rail MCP6002).

Since the current required by the MOSFET gate is effectively zero, it ought to be possible to use a capacitative voltage doubler like the Dickson Charge Pump to increase the gate drive voltage. However, I would really like to minimize the number of components in this circuit.

I know an opamp can be set up as a square wave generator to drive a charge pump. If I have spare opamp circuits in my IC, is it possible for an opamp to double its own supply rail?

I tried mocking up such a circuit, but I'm fairly sure it won't work:

If I'm correct, when the opamp output goes high, the opamp is effectively shorting C2, which won't have the desired effect at all. Is there a way to reconfigure the circuit that will work?


texts: Modifying ATX SMPS into bench-top power-supply

texts:
Due to low cost and high output current this project is pretty famous in DIY category, and I thought to give it a try too, but a lot of people are connecting so called Load Resistor on the terminal which give the most power as to keep the power supply constantly on, and here the confusion begins, in my SMPS the most power is supplied to 12V rail, but the fan used in SMPS is directly connected to it, and I've read projects in which the similar connection to fan and 12v rail was found.

Question wobbling in my mind is, if there is a load(fan) already connected to the rail with most power and it is constantly on(no temperature control) why you need to add some extra 'Load Resistor'?

Are other makers adding a load resistor just because "Everyone else is doing so I should too" or there is a hidden reason behind it, example- that there should be more than some specific Watts of load and because of that, you need to add a resistor.


texts:
I have several electronics books from which I am presently reading the subject of power amplifiers. I noticed two different approaches.

In the first book, the author claims that a power amplifier is one that delivers the most possible power that the transistor is capable of to a load. So, he said the Q point of the amplifier should be set on the power curve. Given that the transistor cannot handle currents above \$I_{C(max)}\$ or collector emitter voltage above \$V_{CE(max)}\$, tangents can be drawn on the power curve from the these two extremes. These tangents are the ac load lines and all the points between the intersection of the two tangents with the power curve are the permissible Q points such that the transistor is driven to its utmost limit. Also these Q points will always be at the center of the ac load lines (tangents). This seems very clear and intuitive.

In another book, the approach is different. Here, the author begins with the dc load line and shows that the ac load line is different. Then he goes on to explain that to maximize the voltage and current swing the Q point has to be on the center of the ac load line, which again seems logical.

In the first approach the amplifier can be designed with the load in mind. By this I mean, if you know \$V_{CE(max)}\$ on the characteristic curve, you can draw the ac load line and immediately get the Q point. From the slope of the ac load line we can easily find the ac collector  resistance and from there proceed with finding the biasing resistors.
In the second approach, locating the Q point seems to be very difficult because even if the Q point is at the center of the dc load line, it is very possible that the Q point is not at the center of the ac load line !

So here are my questions. Which method should I adopt in designing a power amplifier ? Also, suppose I chose the second approach how can I be sure that even if I manage to set the Q point at the center of the ac load line, it will be on the power curve ?


texts:
I have just started learning logisim, so i have a very simple question. My question is what does splitter do. Whats its function and how can we actually implement it(like on breadboard or trainer board)?
Thanks in advance


texts: what is 1 volt and 1 ampere? May sounds very basic but its deep. please help

texts:
Facts:

Charge, or more specific electric charge, on 1 electron is \$-1.6 \times 10^{-19}\$ Coulomb
One has to do some work to get electron from its outer most orbit. It can be room temperature as well.
Current flows only if there is potential difference.

Questions:

Ampere is defined as, 1A = 1C/1sec
My understanding is : “We can say 1A is flow of electric energy of \$(6.242 \times 10^{18} )\times (1.6 \times 10^{-19})\$ Coulomb = 1C in 1sec from cross section.” To generate this flow of electron, we need some energy. What is this energy? Is it volt?
Volt is defined as, 1V = 1J/1C
My understanding is : As mentioned in fact-2, one has to do some work to get electron from its outer most orbit and same electron will help to generate current. So, here we are doing 1J of work to get \$6.242 × 10^{18}\$ electrons (which has accumulative electric charge of 1C) out of their outer most orbits. If one says, free electrons are already there in conductor, then where are doing 1J of work.
With above details, how can we define potential difference.
Very basic, may be dumb as well, if electron pass through LOAD, Say bulb, will it loose its charge of \$-1.6 x 10^{-19}\$ Coulomb. If not, from which energy bulb is able to glow.

please help in building clarity.


texts: Can someone show this problem for this example step by step

texts:
Plot the magnitude and phase of the following complex functions:

G(w) = 1/(1+jw)

We never went over this in lecture but apparently I have homework on it. Looks pretty simple but just don't know where to begin. Could anyone maybe walk through the process of it rather than just answer?

edit: I apologize for my ambiguity here is the problem word for word:

Plot the magnitude and phase of the following complex functions:

(i)   G(w) = 1/(1+jw)

(ii)  G(ω) = −1/(1+jω)

(iii) G(ω) = j/(1+jω)


texts:
Many times I know the parameters of a part to choose and find hundreds of them, but I don't know which ones I would have to order, which ones I am likely to found in a local electronic parts store, and which ones are likely to be in every parts store and are much cheaper than the previous ones.

Say I need an NPN BJT with collector-emitter voltage of 1,5 kV, collector current of 2 A, collector peak current of 10 A and dissipated power of 6 W. Searching suitable transistors and checking each one whether it's present in a local store's price list takes a very long time. So how do I choose a suitable transistor that's likely to be found in most electronic parts stores?


texts: Interpreting the circuit diagram in the dataasheet of TGS2442

texts: In the basic measuring circuit given for TGS2442, in the datasheet Page 2 here can somebody help me in understanding how I can supply both Vc and Vh through the same input.  And how can i use the transistors to control pulse?


texts: Using capacitors to prevent surge current on lead-acid batteries?

texts:
I'm using a 300 Ah lead-acid battery bank, and a 12V->230V 1000w pure-sine inverter, to power a residential-type refrigerator. With a bit of experimentation, I've managed to reduce the starting power required to a peak of approximately 1500w for 400 ms, which is within what that the inverter can provide. So far, so good.

Unfortunately, this draws a peak current, I'm guessing, of about 100A on the battery bank, which causes the voltage to drop for a brief moment to 11.5V, even when fully charged.

Over several months of use, I've realized that the battery bank capacity is severely reduced by these peak currents, reducing the 300Ah capacity to something more like 100 Ah. Perhaps I've already damaged the batteries.

A more suitable replacement would be a battery type that can handle these surges, e.g. LifePo4 (designed for 3C peak, e.g. 720A). But the price for these batteries are simply prohibitive: my 300Ah, 80%/240Ah usable, lead-acid bank cost about 400 USD; a LifePo4 240Ah bank would cost approx 1400 USD).

Another option is to add some kind of additional capacitance. For example, ultra/supercapacitors. I'm not sure what kind of specification I would need. The voltage would be approx 12.5V, and should be able to release 500 J before reaching, I'm guessing, 12.1-12.3V. Wouldn't this mean that I would need more than 1000F?

I'm thus faced with a number of options:

a) replace battery bank (1000+ USD)
b) replace starter motor with Danfoss BD35F (15A peak, approx 450    USD)
c) add supercapacitor (how many Farads? 3F seem to cost approx 50    USD)
d) design a circuit that temporarily draws current from a standard    car starter battery instead (50Ah 12V car battery costs
about 75 USD)

I'm thinking that option D might be the simplest and most universal.
I could connect it in parallel only when starting the fridge, and disconnect it for the rest of the time, while allowing it to draw a charge through a diode. I'm assuming that the batteries would compete to deliver the current, but that the starter battery would maintain a higher voltage, thus winning the battle, and being the primary deliverer of current. Alternatively, I'd have to disconnect the battery bank temporarily, to ensure all power being drawn from the starter battery.

The easiest is obviously to spend 1500 USD for fridge that is designed for 12V, but, I like being hands-on.

Ideas are welcome!

Additional note: As I understand it, the surge current is only 100A x 12.5 V for 500ms, or 625 J. A starter motor battery with 50Ah/12.5V would have 112kJ capacity at a 5% discharge, which would allow for 180 starts.

Update: I've since replaced the lead-acid batteries with LiFePO4 instead. However, if you wish to improve the starting current performance, I believe that you could wire a small 6Ah LiFePO4 (e.g. motorcycle starter battery) in parallel, operating in a voltage range of 12-14.4V.
However, my realization is that I don't know why anyone would ever want to buy lead-acid batteries in the first place. An absolutely outdated technology.


texts: Can I run audio signals through a dimmer switch to control volume?

texts: I have long had a off/on light switch in my living room controlling whether the speakers in that room are on or off. More recently, I've wanted the music in the living room to be slightly softer than that in other rooms. I've thought about replacing the light switch in there with a dimmer switch, but I don't know if decreasing the voltage of an audio signal is safe, or functional to decrease volume. Is it? If not, what are some other solutions?Thanks,-A


texts:
Following up interesting discussion here with John Birckhead (@JohnBirckhead), I decided to ask separate question on the issue.

Here's my circuit

The circuit includes UDA1334BTS, DAC powered from +3.3 V, connected using its typical application diagram (see page 16, fig. 8) and AD8512 op-amp, powered from ±12 V. Initially we were troubleshooting the problem of my circuit not working with two new op-amp chips, with chips looking like defective or damaged.

John proposed that while circuit looks good, there's a problem when it is being turned off.

Capacitors C66 and C57, which are of 47 uF value, discharge too slowly through DAC output and 220k resistors of respective channel; when system is turned off, ±12 V supply is removed very quickly, but potential capacitors are charged to remains for next several seconds, violating condition explained in datasheet that

  [AD8512] have internal protective circuitry that allows voltages as high as 0.7 V beyond the supplies to be applied at the input of either terminal without causing damage.

Let's look what is going on in my circuit:

We can clearly see that power goes off exponentially (red), at the same time op-amp's input is about -1.2 V.

However further datasheet states that

  For higher input voltages, a series resistor is necessary to limit the input current. The resistor value can be determined from the formula (Vin - Vs)/Rs ≤ 5 mA.

I am confused here - what matters - over-voltage, or over-current? In my circuit there's series resistor of 100 Ohm, when power if completely gone current flowing through resistor (approximately) ( -1.2 V - 0 ) / 100 = 12 mA, higher than required by datasheet.

John has proposed putting negative voltage limiting diodes (manually drawn connections on the circuit diagram), these diodes would make caps discharging faster.

I want to know your opinion - is there any other way to mitigate this effect? I think I did not see many circuit diagrams having diodes before op-amps.

Probably it is a matter of tuning DAC's typical application circuit, C66 and C57 values (e.g. from 47 uF down to 1 uF), decreasing values of R29 to R44 (e.g. from 220k to 10k), and increasing value of series resistor (e.g. from 100 Ohm to 220 Ohm)?

As a side note, I have old computer with mixer (NJM4558-based)

and it also exhibits these issues when powering on or off, but, as far as I can see, voltage on its op-amp input goes down relatively the same rate as power voltage. In my case input voltage is too long outside of allowed range relative to power.


texts: probable cause of damage to small SMD part: ESD, heat, something else?

texts:
The part in question is a 2 x 2 mm LGA accelerometer.

1. First soldering scenario, 10% non working parts after the assembly:

no ESD protection gear
hot air gun smoothly brought near / away from above the part; low temperature & low air flow setting
care has been exercised in handling the parts

2. Second soldering scenario, 36% non working parts after the assembly:

wrist strap protection gear grounded to mains GND, nothing else
hot air gun not-so-smoothly brought near / away from below the part (from the other side of the PCB); high temperature & high air flow setting
care has not been exercised in handling the parts

I know ESD can damage such minute parts although I am not sure to what extent. 36% seems a bit high. Should I attribute this high rebuttal rate to the heating process ? Perhaps to something else ?

Responding to the comments

Care from the above paragraphs refers to directly touching the metal pins of the part or not. Probably not releveant ESD wise though. I should have been more clear on that, sorry.

As for the rest, I do not have a proper lab here, I am just hand assembling these PCBs at home. And the worst thing about this is that I do not have any temperature control. This is no bad soldering as re-soldering yields the same results. The rest of the circuit works OK once the faulty parts are removed. They have been kept in that special humidity absorbing bag they were shipped in.


texts: Voltage Divider or Step-down transformer for voltage sensing 240V AC

texts:
Hello I am trying to measure 240v mains AC as safely as possible. There seems to be 2 ways to do it, which of the two is better and preferred?
1. Voltage divider directly from the mains
I have found an schematic that seems to be form a data sheet of an adc where in the mains is directly voltage divided and connected to the adc

Rhi is 300k Ohm and Rlo is 750 ohm . I dont know why the 3 300kOhm are in series though. I do not know how to pick a appropriate varistor though i assume a 375 peak to peak voltage , would this be correct? Also is that earth or ground (adc ground) where neutral is connected because they sometime interchange the two and it becomes confusing in these situations.

Voltage divider After a transformer

This approach seems to be the safer one but not a space saving one using a very small transformer like this that can output 5v and voltage divide from that

Is the ground necessary? I only added it because the other circuit added one.
My Thoughts
The reason i like number one is because it can be made much more compact than the second, I cannot decide if is it worth the protection of the entire circuit for a compact size. How likely is circuit 1 more to fail than circuit 2?


texts: Identify a 24 pin QFP with the writing "024 14 09 SD426"

texts: I have these parts but I don't have any part number information for them.  They are 3x3mm, and the marking reads 024 14 09 SD426. I checked some online part finder sites but couldn't identify it.


texts: Simple data connection through powerline wires

texts:
In my home/office/business I have a 4 incoming electricity lines, (Government line, private subscription generator 1, private subscription generator 2, home gasoline generator)

I want to send through my wiring a signal indicating which source is 'on' at the moment. I would put a receiver near high consuming devices to work only when the government source is on.

I thought about a wireless solution, but I believe power-line solution is much more robust and better to the environment, and obviously cheaper.

Is there any simple circuit that allows me to send such small amount of data, without the use of a micro controller and serial data transfer? As far as I can tell, all I need is 8 bit parallel data transfer to send this data.


texts:
Does anyone know of power-estimation spreadsheet or tool, or have measured power data for the Atmel AVR32 UC3L Series when running heavily in a real application?

The datasheet itself is not very helpful, as it lists mostly minimum power numbers in few light configurations (e.g. spinning Fibonacci numbers, which is just adds and branches, with every possible MCU feature disabled) with statements like "These numbers are valid for the measured condition only and must not be extrapolated to other frequencies." [AVR32UC3L datasheet, table 7-5, page 44].

EDIT: I thought the question was quite clear, but to be specific: I'm interested in measured power data or a power estimation spreadsheet for this particular microcontroller, not microcontroller power theory in general.


texts: If i have a high current (12 amps) passing through my route is it ok to put via on it or to duplicate the route (150 mil on top and 150 mil on bottom)?


texts: Can I use Formula SP-30 self-cleaning acid paste flux?

texts:
I am a complete noob when it comes to soldering. I've only done a little bit in the past and it was years ago. Today, I bit the bullet after reading about how to solder and purchased some soldering supplies a the local Frys. When I got home I read the label for the paste flux I purchased and it said:

Kester
Self-cleaning Acid Paste Flux
Formula SP-30

I didn't see anything that said rosin, so I went online and read the manufacturers datasheet. It says:

  Like other inorganic acid fluxes, Kester SP-30 is too corrosive for
  electrical or electronics soldering applications.  In all cases, the
  flux residue should be removed after soldering to avoid any corrosion
  problem.

Did I just buy plumber's flux instead of electronics flux?   Does this product have any utility in electronics?  If not, why would Frys put something like this in the electronics soldering isle?


texts:
I would like to ask your opinion regarding NMOS test-bench as a varactor (voltage control capacitor). I am trying to find the properties of Vg,W for achieving a \$200fF\$ capacitor.

Here is my test-bench :

Calculated \$C\$ using AC analysis, where

\$C = \frac{I}{(V*2*pi*f)}\$

\$I = NMOS-Gate\$ point

and

\$V = voltage\$ on gate net.

Is this correct?

question - we are looking for \$Cgs\$ here, so can I just take the value from Cadence "Results Browser"?


texts: Rewriting this logic expression to NAND only ports

texts:
I have made a logic expression for the J2 input of a JK flipflop using truthtable and karnaugh map (see truthtable below), but now I want to rewrite it using boolean algebra to get an expression that only includes NAND-ports

Truthtable:

(1st expression is the one that needs to be simplified, 2nd expression is the solution)

EDIT3: found this expression and circuit, can anyone confirm that this is the most optimal NAND-gate solution (least ammount of gates)?


texts: Solder does not stick to tip of soldering iron?

texts:
Basic question here, but it's driving me insane!

The solder does not seem to stick to the tip of my soldering iron. After the iron heats up, the tip appears black (sometimes on all sides and sometimes on one side), then either it doesn't melt the solder at all, or it I fiddle around with it for a while; it melts the solder, but the solder rolls into itself into a ball and doesn't stick to the tip.

I've seen this many times while soldering before and usually it's solved by cleaning the tip on a soldering sponge or cooling it down and scraping the tip off with a blade, but I have scraped this particular one many times and still it's the same problem: it heats up and gets black, then the solder doesn't stick to it.

It doesn't help that this soldering iron has a very fine tip and I have to use it to solder very tiny chips and wires under a microscope (I'm just starting to learn soldering under microscopes).

Any ideas on what I can do?

PS: Is scraping the tip a bad idea? I have been doing it with my other bigger soldering irons and it seemed to work (at least in most cases) but I am not sure whether it is a good solution or not.


texts: Can I use a Bus Pirate to drive this VFD?

texts:
So a few months ago I asked the question on how to analyze a display. Since then I have found out much information about this board.

From some trace following it seems that

Brown  - DATA
Red    - CLK
Orange - CS
Green  - GND
Gray   - 5v

Datasheet

Now the datasheet doesn't really say anything about having a Chip Select, but that little chip right below the input wires is a NOR gate and provides the functionality.

Here is my problem. I cant seem find any consistent way to communicate to the board using a Bus Pirate.

My setup is based on this post from Hack-a-Day. Which admittedly somewhat works, but is not consistent and works more like magic guessing. Could someone give me some insight on how to tackle this? Is the 2-wire mode on the Bus Pirate the best way to test this display?


texts: A question about an instrumentation amplifier and common mode currents

texts:
Regarding my previous question, an unbalanced(single-ended) source Vs is connected to inputs of an instrumentation amplifier and ground as follows:

I have seen above connection in many texts.

For simplicity let's assume Vs is DC and common mode voltage Vcm is DC. And all impedances are real and they are resistances.

And regarding the above diagram, let's say the line resistances Rl1=Rl2=100 Ohm. The input impedance of the inAMp is Rx=10 MegOhm. And the source impedance is 200 Ohm.

What I understand is the common mode current Ic1 loops through the following resistances:

Rs-->Rl1-->Rx

and Ic2 loops through the following resistances:

Rl2-->Rx

If I'm not wrong the impedance seen from the hot terminal is: Rs+Rl1+Rx
and the impedance seen from the negative terminal is Rl2+Rx.

My two questions are:

1-) It seems like Rx>>>Rs in an inAmp because of its buffers, does that mean the source impedance matching is less important than in a difference amplifier? Can Rs in practice can be neglected when using an inAmp this way? Let's say Rs is 50 Ohm and Rx=10Meg, would you still add a series 50 Ohm resistor to the negative terminal? Or would you neglect it because Rx dominates?

2-) Look at the third wire at the bottom from the negative terminal of the source to the ground of the inAmp. There is no resistor on that wire. In practice should there be a resistor there not to cause a short circuit?

Edit:


texts: Signal and power cable over long distances

texts:
I am working on a hobby project where I am trying to build a ROV (Remotely Operated Vehicle) for underwater use. The ROV will have some electronic parts, that are powered with 12v and 5v, that I have not selected yet. (Brushless DC motors, servos, LED lights, video camera, microcontroller,...)

For mobility I am concidering to use one or more 12v batteries (car bat. or lead bat.) on land and a laptop with an  microcontroller for controll.

So I want to use a cable that has 4 cores, two for power and two for data.

I would like to have at least 100 meters of cable, but a range from 200 to 300 meters or even longer would be much better. Is this possible ?

What cable should I choose (low cost is priority) ?
Whats about the voltage loss over distance ?
Is it better (and safe) to invert the 12v DC from the battery(s) to AC and transform back into DC at the ROV ?
And what would be the best way to design the data transmission ?

The data that comes from my laptop to the ROV will be mainly control signals that a microcontroller at the ROV will interpret. The data that is coming from the ROV back to the laptop, is video and sensor data.

If the data (mainly the video data) transfer would be a problem, I was thinking of only using a cable for power but using rf communication for sensor data, control and live video. I don't want to mess with underwater low frequency transmission (since I think this is way to complicated) so I was thinking of using an antenna that floats on the water surface. (Connected to the ROV over a fixed length cable, that would limit me in operation depth)

I am happy to hear all of your ideas and advises.

Thanks.


texts: Is shielding the entire circuit with a faraday cage a good idea?

texts: Let's suppose I have a circuit which contains a 3.3V MCU and a buck converter (let's think that its frequency is higher than 400 kHz). I'm wondering if shielding the entire circuit would not a good idea because I think that the shield may reflect the noise generated from buck converter to the MCU. Is this a valid concern?


texts: Identifying unusual three terminal component

texts:
I was desoldering some components from a board and found this three terminal device I have no idea what it is. The labels on the PCB were F1, F2,... which is usually reserved for fuses, but I've never seen a fuse that looked like that. My guess is that F stands for filter or something.

That 223 is literally the only label on the package, and it's a small rectangular box about 0.8 x 0.8 x 0.3cm.


texts: Fly-back dc/dc converter connect to external ground

texts:
I am making a PoE design with a silvertel AG5200.

This design has two inputs, PoE and a 'aux' power input. The AG5200 is a flyback and is isolated from the ethernet, so it has a isolated ground. When the PCB gets power from the AG5200 and I connect the 'aux' power source I get a ringing effect. This ringing effect kills my Ethernet switch IC. Because it bounces through the whole system.

I noticed I get the ringing of 3V above of the 12V when I am connecting a external ground. (I removed D1 and D2.)
I think it is because the ground is isolated and "floats" and when I am connecting a external ground the AG5200 has to adjust his output because his reference is changing.

I added a resistor of 8ohm between the external ground and the ground of the PCB. The ringing effect is then smaller, but I need a better solution.

The AG5200 is a blackbox, so i have to do it externally.

What is the best approach to fix this problem?

simulate this circuit – Schematic created using CircuitLab


texts: What's the name of signal encoding used by WS2812 LEDs?

texts:
The WS2812b color LED uses some kind of duty cycle encoding to encode three states:

one
zero
reset

This can be seen in the following figure:

(Source: https://cpldcpu.files.wordpress.com/2014/01/ws2812_protocol.png)

What's the name of the used encoding?

It's not classic Pulse Width Modulation (PWM).

Edit:
While this question What encoding is used in this signal? asks for a name of a similar modulation, it does not give a name for the modulation.


texts: Very Basic 555 Timer oscillator not working

texts: I've been trying to make an LED blink. My first approaches were without the 555 timer, and they were unsuccessful. I decided to make an Astable multivibrator circuit. I'm using an NE555, and I'm using the circuit on this video. For R1, I used a 680ohm resistor, and for R2 I've used 1k, 10k, 100k, 500k, 1M ohm resistors, and none of them have proven succesful. For my capacitor, I'm using a 100uF capacitor. I've tried 1uF and 1000uF aswell. Please help!


texts:
I have done a LDO circuit at https://github.com/promach/LDO

I have few questions :

Why in the second bode plot (which might be problematic PSRR), gain going up near unity-gain frequency is often a sign of instability ?
Why is there some initial noise disturbance around 10us during start-up ?
What is the purpose of M2 and M26 ?
Could anyone explain the mechanism of transient performance enhancement circuit consisting of M19, M27, M23, M24 and M25 ?
Any suggestion on suitable test circuit for load regulation metric check ?


texts: I'm working on a project for which I need to use a 7805 voltage regulator. I feed 9V to its input pin and power a 5V board with the output. However, when the board is connected to a computer, the board outputs 5V through the same cable: even if I turned off the 9V power supply before connecting the board to a computer, would the voltage regulator be hurt by the 5V input to its output pin? Can I fix this with a diode?


texts:
My current project does involve some DC motors which I have to control the speed of. I'm will probably use the PWM pins of my arduino mini for this.

Currently I am building my first prototype of the setup so I can test the PWM. I have the motor connected to a 9V block battery, so my motor has enough power to run. The main control mechanism would be a NPN Transistor which would get its base from an optocoupler, since I want the arduino be isolated from the 9V circuit.

So this leads my to this setup:

[

My problem with this setup is that my transistor is not working and I'm not exactly sure why.
Just to specify the way this circuit is not working.
When I am activating my optocoupler nothing is happening. So I tried to identify the problem. I cut the optocoupler in order to see if the transistor is the problem.
Since it is somehow still not working I figured out that the transistor has to be the problem. But looking at the spreadsheet of the transistor it looked good so right now I'm at the point where I do not have any idea what the problem is.

The interesting thing about all this is that it all worked out when I tried it with an LED instead of the DC motor.
Probably it is something simple I'm missing but I do not spot the mistake.

//EDIT
So first of all thank you for all the answers. I know these are stupid mistakes, and I'm kinda hating myself for them, but still thank you for helping me with my first major project outside of high school physics.

With all the help I got to this circuit. Should it work now?

I also wanted to ask how I would calculate the different values for the resistors, sice we didn't had any resistor math in class yet.


texts: SPI with multiple slaves working on different voltages

texts: Is there any way to hook up two slave devices in SPI mode: one working on 3.3V and another on 5V level, using a micro controller without using a logic level converter to interface between them? Suggestions of any micro controllers which would allow this would also be great.


texts: MAX485 half duplex Atmega communication problem

texts:
I want two atmega32s to communicate over a range of 1000ft, so I decided to use a serial wire for it. I know rs232 is not a good way to communicate over this large range, so I decided to use RS485 which is a balanced pair. For this I want to use MAX485 chips like these.

Now I wrote all the code to use it and got it working for short wire communication with a battery powering my ATmegas (and the MAX485 chips) (I cannot produce the code here as it is for a company where I am just an intern, but as it works in short wire the code is not the problem). What the program basically does is, one atmega sends "Paresh" on serial, the other atmega receives it, does a strcmp if it is indeed recieved as "Paresh" it sends out "Mathur". If the first atmega receives "Mathur" it again sends paresh and the cycle continues.

All this works just fine for serial mode, short wire and on a 6V battery. But as soon as I switch to a CAT-5 cable I get packet loss. I printed what ever one receives on an LCD and after a few cycles (and sometimes even for the first transfer) there is strange strings received. The problems are:

It works for short wire but not a 30ft CAT-5 cable
It works for 6V battery but not for 12 volt battery or a 12V adapter.
It works for normal serial wire upto 10ft but not more than that.

The things I have tried are:

Added capacitors to fade out any ripples in the supply. (470uf caps).
Increased delays between switching from transmit to receive modes ( _delay_ms(3); ).
added caps to the supply to the modules.
Adding 120ohm terminal resistance to both modules.

What should I do? Please do no suggest any alternatives to the the thing, it would hurt the hacker in me. Why cannot I use an RS485 communication for exactly the purpose it was designed .i.e long distance communication over serial.

Update 1: I used 120ohm terminal resistance.
Update 2: I am on a 9600 baudrate.


texts: How can I interface with arduino mega2560 to detect the presence of a 48 V without pulling down the voltage by more than 0.1 V

texts:
How can I interface with a microcontroller to detect presence of a 48 V supply with a source impedance of 10 kΩ without pulling down the voltage by more than 0.1 V?

I need to step down the output voltage (48V) at the drain of the IRFZ44N power MOSFET to within 5V so that it can be read by an Arduino without loading and causing the voltage to drop below 48V.

The MOSFET is acting as a switch. In the end I need to be able to tell if the switch is on or off based on the output at the drain terminal of the mosfet. How do I go about this?


texts:
I'm an amateur at electronics circuitry and concepts. I have designed a simple capacitive power supply using few web images and brief lessons. I understand that this type of transformerless power supply is highly dangerous. So i will take the utmost care while working with it.

The motive of the circuit is to charge a 4-4.2v battery (mAh capacity unknown) to operate a single 1 watt white LED when needed (basically a simple cheap flashlight circuit).

I tried to simulate the circuit in Falstad circuit simulator but it isn't the easiest and doesn't render at times( or renders different values at different times )

I have few questions, some of which might seem to be very simple(noobish) but please bare with me. Any kind of knowledge will be much appreciated.

Questions
1. If the mains are disconnected and the SWITCH OFF, can the battery discharge through resistor R3 then capacitor C2 through the 1n4007 Bridge rectifier and back to the negative terminal of the battery?

What effect does the values of resistors R1, R2 have on the overall circuit in terms of current and voltage output at capacitor C2?
Still need to calculate values for resistor R3, R4
Suggest any circuit/component modifications with basic electronic components along with some explanation or information.
Recommend an extensive circuit simulator with pcb design.

Thank you


texts: Is it possible to use 2-way walkie talkie to locate position?

texts:
Basically, given no GPS is allowed, can we use walkie talkie to locate the position of a car / a person?

I am assuming the walkie talkie is using radio, not GPS-based.

What equipments will be required to capture the signals in and out to approximate the location (within 2 miles range)?

Thanks.


texts:
I have a load that I am trying to switch with a relay. The load to the relay is an autotransformer. The wiper output of the autotransformer is (2) 120:30 step down transformers with each having 150W light bulbs on the secondaries.

The legacy system had a 3A relay (field point module). I measured the steady state current to be 3.5A Irms to the autotransformer. How can the relay in the field point module support this measured current?

When trying to spec out a relay, a lot of reasonable relays only give a resistive rating, but don't I need an inductive rating for this application?


texts: HIP4086 Driver Failing After Connecting to BLDC Motor

texts:
Update:

A Renesas Tech pointed me to the documentation for the HIP4080, which is basically a two leg version of the HIP4086, but with much more thorough documentation. I now have three working theories for the failure:
1. My bootstrap capacitors are too small for the PWM frequency.
2. The diode that I used are not fast enough.
3. PWM frequency was too high.

All can, apparently, cause insufficient power to be available to handle the high side MOSFET gate charge, thereby causing more of the current to be drawn from the HIP4086. Also, given that (3) is known to cause heating issues with the 4080, I think a redesign is warranted.

I am at my wit's end on this one and am really hoping someone can point me in the right direction.

I have a custom designed 3 phase motor driver using the HIP4086A driver chip, the schematic is based heavily off the driver/MOSFET section of the demo board, found on page 17 of the demo board manual. Only four differences exist between that design and the one I am using, all other components are identical those used on the demo board:

Substituted MBR2H200SFT1G for the ES1B diodes
3.3v logic is used instead of 5v.
High and low inputs are linked so as to require only 3 inputs.
Dead time is permanently enabled via 30K resistor from pin 7 to Vdd.

My problem is that when I power the board with 12v to the HIP4086A and 24v to the MOSFET bridges, everything works great. My scope shows well defined 3ph output waveforms from the bridges of the correct period, timing and amplitude. Nothing heats up (I inadvertently left it running for an hour like this and no problems once so ever).

BUT when I connect and power a motor via PWM at low RMS current (<1A), the following occurs:
1. Motor operation is sporadic at best, but this may be due to the test motor being a fairly cheap motor with high torque ripple. This lasts about 30 seconds on average before (2).
2. HIP4086A stops output to the MOSFETs. HIP4086A shows an increased constant current draw of 0.35A @ 12v. MOSFET bridges show zero current draw @ 24v.
3. Usually this is where I catch the error. The HIP4086A is dead at this point. I did not catch it as quick the last time and the HIP4086 actually melted the solder on its pads and a small bubble formed on the top center surface of the IC, adjacent to pin 19. No other components or traces show any noticable temperature increase.

Can anyone offer any advice as to why these driver ICs keep self destructing as soon as an inductive load is connected?

Schematic (Please forgive the roughness, I am not in-office right now)

PCB Layout images, latest version. 4 layer board, first image is composite, each additional image is one layer only.

Added reformatted partial schematic. I hope this is more readable.
Note: Current Sense resistor connections omitted. Current sense not enabled, currently.


texts: How can I set the pad spacing and size of the footprint of the PQFP package?

texts:
I'm beginner in electronics.

I want to make footprint of HV5622 shift register using Eagle cad. But I don't know how to set the pad spacing and pad size of the footprint.

There are three values in the datasheet: min, nom, max. I don't know which one to use.
And, in the datasheet, the leg length of the chip is 1.95mm, but I don't know how to set the length of the pad.


texts: If a diode is rated at average forward current at 1 ampere can it stand 1 A from the circuit, or to withstand 1A current should the diode be rated for average forward current of at least 1.5 amperes?


texts: Replacing a battery pack with a mismatched DC source

texts:
I have a PCB which is nominally powered by a custom battery pack.  Specifically, this battery pack:

So five cells connected in series, at 3.6V each, which I assume means that the nominal output voltage is 18V.

Speaking generally, would it be possible to do away with the battery pack and replace it with a mains-driven DC power supply?  And assuming so, what would happen if a slightly mismatched power-supply is used (for instance, one that provides a 19V output, or one that provides a 15V output)?

Could the PCB generally be expected to function, or does the input voltage from the power supply need to exactly match the 18V provided by the battery pack?


texts: Buck-Boost Transformer with Three Phase Wiring

texts:
I live in a residence with 120v / 208v electrical service.  (Measured as leg1: 124v, leg2: 125v, 215v across legs)
I am nearly certain that the service is the result of two legs of three phase power.  I live in a city near apartment buildings and other commercial structures.
Can a single phase buck-boost transformer be used to raise the voltage?  I’m concerned because the transformer wiring diagram connects the two legs across the two primary windings (leg1-h1-primarywinding1-h2-h3-primarywinding2-h4-leg2) and I know it’s not advisable to short between out of phase legs.

I have found a couple sources that say this should work, but nothing that tells me why it will work and I’m unsure as to the quality of the sources.  Many thanks for your help!
Matt


texts: Circuit Analysis Problem, KCL Nodal Analysis with Supernode

texts:
I'm trying to understand how to correctly set the KCL equation for this type of problem that is explained in this ebook at page 19:
I'm following the procedure of the guide, that provides a wrong formula (because it swithces the resistors \$R_1\$ and \$R_2\$ in the formula, this is a minor error that I corrected easily, this is not the problem itself) and not very intuitive; considering a supernode for the voltage source. Since the \$V_{S_1} = 10V\$ we can derive that \$ V_2 = -10 \$. Also for the supernode we can say that \$ V_3 =V1-4 \$. Also the value of resistors are \$R_1 = 4\Omega\$ and \$R_2 = 5\Omega\$.

The KCL formula for the supernode provided by the author is (I'm not considering the resistor switch error): Eq: A.1 $$-I_{S_2}+\frac{V_1}{R_1}+\frac{V_3-V_2}{R_2}-I_{S_1}=0$$
For me from this formula (the results are correct anyway: \$V_1 = -\frac{44}{9}\$) it is not clear how the author is setting the equation:

The first term  \$-I_{S_2} = -(1A)\$ is a current that it is entering the supernode, the author is putting negative sign so is should be a current that is leaving the supernode
The second term \$\frac{V_1}{R_1}\$ is a current that has a positive sign so it's entering the node, but it is structured as if the current is leaving the node (because the voltage drop is "towards the ground node \$\frac{V_1-0}{R_1}\$" that is different from \$\frac{0-V_1}{R_1}\$).
The third term has exactly the same structure as the second one, positive sign and the voltage drop "towards" \$V_2\$ so leaving the node.
The fourth term \$-I_{S_1} = -(-2A)\$ is a negative current that means it is naturally leaving the node, but with a negative sign applied it will have a positive sign that means it is entering.

So the first term is leaving, the second one and the third one are entering with non intuitive voltage drops and the fourth is entering the node
So form this is not clear at all. So I tried to simplify this circuit in the following way: I inverted the \$I_{S_1}\$ current source so that now the negative sign will not confuse anymore and I wanted to set the KCL equation for the supernode assuming all the currents entering the node.
So now the KCL equation for the supernode that I setted is: Eq: M.1 $$I_{S_2}+\frac{0-V_1}{R_1}+\frac{V_2-V_3}{R_2}-I_{S_1}=0$$
In this case we have that:

The first term \$+I_{S_2}\$ has a positive sign and considering the direction of the current we can say that the current is entering the node.
The second term \$+\frac{0 - V_1}{R_1}\$ is a current that has a positive sign so it's entering the node, and has a voltage drop "that is towards the supernode" so the current is entering the supernode.
The third term has the exact same structure as the second with positive sign and the voltage drop "towards or entering the supernode".
The fourth term \$-I_{S_1}\$ it's normally leaving the node (considering the direction of the current) so now applying a negative sign the current is entering the supernode. Substituting the numbers I got the correct result in Eq: M.1: $$+1+\frac{0-V_1}{4}+\frac{V_2-V_3}{5}-2=0$$ $$+20-5V_1+4(-10)-4(V_1-4)+20(-2) = 0$$ $$V_1 = -\frac{44}{9}$$

My doubts come now: since with KCL and nodal analysis I can make the wrong assumptions about the direction of the currents and still getting the correct results, this not seems the case infact:

Considering all currents leaving the supernode, the equation Eq: M.2 should be the following $$-1 -\frac{V_1-0}{4} - \frac{V_3-V_2}{5} + 2 = 0$$ the result it will give \$V_1=-\frac{4}{9}V\$. The same will happen if I consider any other approaches that are different from considering all the currents entering the node.
We can see that we have a different solution also from a calculator

My question is: why is this happening (I can normally set KCL equation as I like and always get the correct result)? Is there something that I should consider when dealing with supernodes)? Why the ONLY correct result is when I set all the currents ENTERING the supernode?
Any suggestion are welcomed. Thank You


texts: I want to discharge a capacitor with an Arduino digital pin. Which of these two circuits is safer for the board?

texts:
I have made a capacitance meter with a 555 timer and an Arduino. It's mostly complete except for the digital pin that triggers the 555. I have narrowed it down to two possible solutions. Both of them use a differentiator to make sure the trigger pin on the 555 returns positive, even if the Arduino is interrupted with a timer. One solution uses Arduino digital pin (clk) to charge and discharge one leg of the trigger cap (10nf).

The other uses the 5v rail to charge, and the Arduino pin to discharge the trigger cap.

My questions:

Is one safer than the other for the Arduino pin?
Is there a better way to do this in general? Perhaps by using a transistor to switch the cap to ground?
Are the RC values the correct size for what I'm doing?


texts: Switching a 3 phase pump using a solid state relay

texts:
I made a remote (GSM) controlled module for a 3 phase pump close to my friends house. The pump should run at night, and walking the 1km to the switch while they are sleeping is the problem.

The manual switch, switches 3 phases which is put through a 4 wire cable (no ground) to the pump 50 meters away and 20 meters down from the manual switch.
At the pump there is a fusebox and a small box which switches off the pump in case there is no water output detected (the water pressure box). The pump pulls a max of 16Amp, the actual amount I don't know (the fuse is 16amp)

My module switches the 3 phase power using a solid state relay ( Eurotherm RS3DA 30A ). I see that the GSM part works and switches the Solid State Relay on, but the pump does not start.

I am not sure what this causes, I had no way to measure the output, just having a voltage screwdriver to test there is voltage on the output of the relay.
At some point the pump after some resetting of the water pressure box) did work but it would never by just powering the whole thing via the relay. Pulling out the 3phase connectors out of my module and connecting them directly will start the pump without a problem.

(there is some waiting involved after running the pump, you cannot just switch it on and off).

At home I could not realy test the relay except for the GSM module (based on Arduino)

I am not sure why this does not work. Could the solid state relay change the 3 phase in such a way that this happens because of power loss (less Voltage?)
Next time I am there (it is a 12 hr drive) I can bring my voltage meter, but it does only do one phase.
Any other things I should buy and take along to test en compare the module in the real world?
Would it help to put the relay after the fusebox?
Should I look for a mechanical relay for switching the 3 phases? Will that solve my problems, or is it just neater (there is a fuse at the switch uphill as well).

If necessary I could hook into the water pressure module but that costs something in the order of 800 USD (my module was about 120 all in) so if I break that I might loose a friend (and my right to visit their remote place).


texts:
Hello and first of all sorry for posting a screen, I don't know how to make my own schematics.

This is one of the excersises from previous year's electrotechnics. The formula to calculate the result is already derived.

$$T = \frac{L}{R_{t}}$$
However, may I ask, how to find the
\$L\$
value in this circuit? Because it's not stated in the task's description...

Thanks


texts: Need help to identify this component from an LED driver module

texts:
I got an LED driver module(LDM) from a truck that drives the headlight of the truck.

The PCB has a strange component which I have never seen before. I have added a picture of that component. The component is used in the input side so I think it may be a TVS diode or MOV.

It is a 2 terminal device.
One terminal is connected to the input line and another terminal to the ground.
The LDM has 24 volts DC and 960mA current input supply, 23 watts rated power on LDM

note:- position of the component is highlighted


texts: How do you cover up exposed high voltage pcb traces?

texts:
This is my PCB:

The thick lines should be able to pass a high voltage (230VAC) signal through it. The board will be kept inside a enclosed box.

In my case, the signal on the board is only one polarity so unless someone is purposefully trying to kill themselves, I think it's relatively safe. However, my question still stands - what are some ways to cover up exposed signals?

These traces are on the bottom layer, and it is not possible to sandwich them in between.


texts: Comparator doesn't swing, is there problem with circuit?

texts: I made this circuit to switch signals based on the 3V regulator sourcing current out VDD (out connector J2), or seeing 3V on VDD coming in on J2. I put the diode to prevent back current into the regulator. I had hoped when sourcing current, R4 would drop 10mV for 10mA, and this would send the comparator high. But it is stuck low. Does anyone see any mistakes? The offset voltage of the comparator is 2mV.


texts: Identifying Value of Burnt 5-Band Resistor

texts:
I've been having trouble identifying the value of this resistor (see picture below) as the color codes in position does not make sense. It looks like a 5 band coded resistor. The 3rd band seems to be my cause of confusion as I can't make out the color. It looked like silver, or is it a gray?

But still, regardless of the reading direction (which I thought I got it wrong originally) and whether the 3rd band is silver or gray, the value produced is not in any of the standard/preferred resistor values.

Or maybe there's a band visibly missing (blackened or discolored or whatever)?

Or somehow I got it wrong, and it might not be a resistor but an inductor or others?

If possible could you let me know:

What is the value of this resistor?
What is this if its not a resistor?
Is the 3rd band is a silver or gray?

I can't depend on my multimeter readings as its just a cheap one but is the only one I have at the moment.


texts:
I don't really understand what the phase shift in a bode plot means. Is it the shift of the output compared to the input signal? And how can I intuitively interpret the meaning of the second diagram in this bode plot? I don't really understand why the shift goes to zero as the angular velocity (omega) goes to infinity (and why the amplification goes to zero as omega goes to infinity). What's there relationship?

This is the bode diagram I'm talking about:

This bode plot corresponds to this circuit:

I used these values for the plot:
Rl = 100, C = 10^(-6) and L = 0.1


texts:
I have downloaded 65nm models for TT, FF,and SS from ptm website(http://ptm.asu.edu/). I want to test these on a cmos inverter using hspice. Kindly tell me how should i proceed. It is for the first time that i will be doing such simulation so kindly also tell me what result should i expect.
Previously I have done Monte carlo of RC filter in LTspice, is corner analysis different from Monte carlo ? If yes, how?
Thanks.


texts: What is load on an antenna? Is it safe to short the antenna port?

texts:
On the readme page of https://github.com/pwarren/rtl-entropy, it says:

  If you're serious about the cryptographic security of your entropy source, you should probably short, or put a 50 Ohm load on the antenna port, and put the whole assembly in a shielded box. Then you're getting entropy from the thermal noise of the amplifiers which is much harder to interfere with than atmospheric radio.

How do I put a 50 Ohm load on that port? Do I just put a resistor of 50 Ohm on the port? Can I safely short the port (connecting both parts with a copper wire)?


texts: Changing noise level with 24-Bit A/D Converter

texts:
I work on a 8 Channel 24-Bit A/D-Converter. I have an issue with the noise level of this converter. There are some "quiet" periods where the noise is low and acceptable and there are other times where the noise increases by a factor of 5.

Y-Axis is in mV, X-Axis in minutes, sample rate is 2Hz, the pcb board electronic is in a aluminum case to reduce the general noise. The A/D conversion part of the electronics looks like this:

The AD converter is the AD7190 from analog devices. Prior to the A/D conversion part we use the following electronic to scale the incoming signals to the A/D converter range:

I tested the electronics connected to a function generator, with open inputs, in a case and without a case several times at different locations and i always get a behaviour like that...
My Question is what is the reason for this behavior and how can i "fix" it?  many thanks in advance!


texts: Help understanding negative feedback & bias design on audio amplifier

texts:
Please take a minute to look at the audio amplifier diagram below:

In case it helps, the diagram comes from a do it yourself Velleman 7W Mono Aplifier (K4001) kit. The amplifier is based around the TDA2003 amplifier.

My question is: Are R1, R2, R3, C1 and C5 forming some sort of negative feedback network? If yes, how does this setup work?

The reason I ask is because so far, I have only seen negative feedback on op-amps and the setup always consists of two resistor that can be configured to provide negative feedback and adjust the op-amp gain. This particular audio amplifier looks like an op-amp to me but I don't see the usual two resistors... heck, I don't even see one of the input biased to half the voltage supply.

Whats going on here? Am I missing something obvious?

Thanks.


texts:
This circuit should work as part of DC servo circuit in audio amplifier with single power supply, maintaining power amplifier stage working point at Vcc/2 (output is AC coupled).

Intuitive approach is to get generic non inverting integrator and replace all ground connections with stable low impedance reference voltage source of Vcc/2.

But the network at op amp non-inverting input is just an RC circuit, so it can sit on any low impedance source, regardless of its level. So I returned it back to the ground. This gave me a freedom to replace voltage reference with simple divider. Am I right?


texts:
I've recently been transliterating some old schematics for a friend of mine (Basically taking paper schematics from the 40s and drawing them in a modern EDA package) and have come across some very interesting/old electronics terms that are not in common parlance anymore.

Since I didn't know what they meant, I had to ask.

Therefore, I figure having a list of interesting/esoteric/old electronics terms would be useful, so here we are.

(Note: Try to stick to terms which were/are at least somewhat common, not things which you or someone you know thought up)

Note:

Please provide a short description for what the thing you are describing is, and a little historical info would be a positive. Just listing an Acronym or the name of an oddball instrument is not helpful if someone has encountered one of the things you are defining, and is trying to determine what it is/how it works.


texts: Can i make a stepper motor stop at 120° increments?

texts:
I have another project, but being much less than a beginner with programming chips I am coming to you fine people for help.

The basic premise is that I want a motor to turn within a full 360° cycle but stop at precisely 120° with a press of a single button. So in simple terms I'd like :

Button press
120° turn, stop and hold
Button press
120° turn, stop and hold
Button Press
120° turn, stop and hold

and on and on...

Could someone please explain to me in layman's terms how I can do this as it is essential to my project.

Many, many thanks in advance.


texts: Current source improves linearity on collector BJT

texts:
I'm learning about analog electronics. I'm looking into amplification stages at the moment.

Question 1: Single BJT C-E Amplifier. Usually you put a resistor between collector and V++, so as \$I_b\$ changes, the collector current changes and causes a voltage drop across this resistor, which then is the amplified signal.

I found circuits that use a constant current source instead of a resistor to improve linearity. How does this work? I don't get it, doesn't the amplification arise from the change in current in the collector/emitter path? How does a constant current do any good for this? (Actually the universe should explode when the current through the transistor is fixed, while \$I_b\$ tries to control it... Thank god we have supply rail limits:-))

Then I have a second question which might be related: How do current mirrors in differential pairs work? Isn't the point of the two current paths (\$I_{c1}\$, \$I_{c2}\$), that the difference in current causes the difference in the output voltage at the usually used resistors? How can they change \$V_{out\;diff}\$ if they are cemented to be equal? Again, the universe should explode...


texts:
I'm trying to understand a schematic of an RFID reader.

Circuit:

What capacitors are used - electrolytic or ceramic capacitors?

I've seen schemes of RFID readers that use electrolytic capacitors, but in this scheme I can't see the "+" side of any capacitors.


texts: Maximum Typical and minimum into datasheets. What is the distribution?

texts:
What is the probability of having a component with the minimum and maximum specified value into the datasheet ?
I suppose this follow a normal law and the typical value is the mean :

Have a nice day !


texts:
With Bluetooth 5 becoming available on consumer devices such as the Samsung S8, I was wondering if it will offer any benefit if you use it with for example a wireless headset using a Bluetooth 4.1 chip?

As far as I understand it will offer quadruple the range and higher speeds, and as it is backwards compatible, will it offer any benefits for 4.* chips?


texts:
I am currently using an AD620 to amplify the signal coming from my load cell. I am supplying it with single supply of 5V and 0V. Below is my preliminary circuit.

I am feeding half the supply to the reference pin so i am getting an output of 2.5V to 3.7V. I also tried feeding the reference pin of 1.5V and I am getting an output of 1.5V to 3.7V as expected from the information provided from the datasheet. What can i do to have a 0 to 5V rail-to-rail swing? Do i have to feed this output to a rail-to-rail op amp like an AD822?

************************************UPDATE*****************************************

I have modified it by using an AD822 "rail-to-rail" op amp to subtract a voltage so I could scale down my output from the AD620. is there something wrong with this? Because I am having some inaccuracies regarding my AD822 output.


texts: Explain differences in SWR meter circuits

texts:
I am trying to understand the detailed operation of a VSWR meter, and found an excellent account in the article "An Inside Picture of Directional Wattmeters" by Warren B. Bruene W0TTK in QST for April 1959.

However there is an unexplained difference between the two circuits (attached) from that article. In Figure 7 the two voltages ev and ei add (for the measurement of the forward component) and are then rectified by the diode and available for measurement by a d.c. meter. Figure 8 shows another design -- which is used in a commercial directional coupler, the Collins 302C -- where the current sampler is a current transformer, but here the diode comes between a resistor that has ei across it, and the capacitive voltage divider for ev. Can anyone please explain why this change is made?

Neither an extensive internet search, nor poking about with an oscilloscope in a Collins 302C, which a friend has kindly lent to me, brought any enlightenment.

(Sorry, I can't find a way to do the subscript characters for ev and iv)


texts: Is this voltage rating relative to ground or differential?

texts:
A transducer has this datasheet.

What is meant by Bu,g?

The amplifier I use applies +10V and -10V to excitation terminals so the difference between the terminals will be 20V and the excitation voltage relative to ground will be 10V.

So Im not sure here what is meant by Bu,g.

Does anyone have experience or idea about this?


texts:
When I studied how AC mains power works, I learned that one of the wires is connected to the ground or a body of water so that it can get back to the power station. The concept baffles me. Every source of information I've come across fails to explain how it works or quickly glosses over it as if it is self explanatory.

If power can travel through the water or the earth back to the power station, then why aren't we getting vaporized when we walk on the ground near power lines?  Also, how does an isolation transformer prevent you or your equipment from getting fried? If I touch both terminals of the secondary, am I going to get fried?


texts: Measuring VPP and DC offset of a 1Hz - 1MHz signal using MCU

texts:
I need to measure the peak to peak voltage and DC offset of a 1Hz to 1MHz sine/triangle wave. The  signals amplitude varies between 0 and 2Vpp and the offset can vary between -2v and +5v. I will be using an Atmega16 to do the A/D. The Atmega16 has an 8 channel 10-Bit ADC with 50-200KHz sample rate @10-Bit resolution. Taking multiple samples for cycle is obviously out of the question.

What I was thinking of doing was to sample two different versions of the signal eg connect the signal to both a negative peak detector and a precision rectifier and connect those circuits outputs to two different ADC channels and then from result of these conversions (ie the  negative and positive peaks) calculate the the vpp and DC offset. Obviously the signals will need to scaled and level shifted before being applied to the controller.

Im not really sure if this will work at all, there must be a far simpler and more sophisticated way to do this that I haven't thought of.


texts: What is the component I am going to find the voltage for?

texts:
I recently found the following circuit from an old exam:

We are supposed to find the voltage V. But... I don't really understand what component that has the voltage V over it... will the V we are seeking be the voltage over the resistors that are vertically positioned, or the ones in series(the ones that are horizontally positioned)?


texts:
When a page fault occurs in a Linux system, the interrupt-handler has to figure out the reason why the page fault happened. But how ?

Is there anywhere a special number for that !? If yes, where is that number logged ?
Is it possible to know the reason for the page-fault before raising the exception ? Eg.

Step-1 Look for the reason by the CPU
Step-2 raise the exception


texts: How large can capacitive sensors be if made of tin foil?

texts:
Based on a similar version of this: https://www.instructables.com/id/DIY-3D-Controller/

What are the limits to the size I can make this foil area?

And the larger I make it, what does the area need? More power? larger resistors?

How would you make a 70cm x 100cm foil sheet good enough enough to detect if you're touching an area of it?

I'm using an arduino nano, is this going to power in it to detect?


texts: Is depth and number of stages the same measure for a CPU pipeline?

texts:
Is it true that the depth of a CPU pipeline and the number of stages of a computer pipeline are different measures? There is not much info about it if I google or look in my books. I think that depth is a measure of the overlapping of instructions while number of stages is a hardware constant. When you increase the number of stages, you usually make the CPU faster but it is with dimishing margin. I looked at Almdahl's law about this and the book "Computer Organization and Design" by Pattersson and Hennesay.

The more stages, the larger the depth but it is stated that there can be optimal number of stages or optimal depth:

According to (M.S. Hrishikeshi et. al. the 29th International Symposium on Computer Architecture)

  The difference between pipeline depth and pipeline stages; is the
  Optimal Logic Depth Per Pipeline Stage which about is 6 to 8 FO4
  Inverter Delays. In that, by decreasing the amount of logic per
  pipeline stage increases pipeline depth, which in turn reduces IPC due
  to increased branch misprediction penalties and functional unit
  latencies. In addition, reducing the amount of logic per pipeline
  stage reduces the amount of useful work per cycle while not affecting
  overheads associated with latches, clock skew and jitter. Therefore,
  shorter pipeline stages cause the overhead to become a greater
  fraction of the clock period, which reduces the effective frequency
  gains.


texts: I have a output of .03v from my logic gate but i need it to be 5v to enable my dc motor. How can i amplify it into 5v using a transistor?


texts: Converting the 0-10V output of a PMT to a +- 10V dynamic range

texts:
I am trying to convert the output of a photomultiplier tube module (Hamamatsu HC120) which ranges from 0 to 10V to  +-10V in order to fit the full dynamic range of a ADC (MCC USB-205). To do so, I've implemented the circuit below using a TI TL074CN op-amp in order to substrat 5V with a gain of 2. The following values are used:
V1: signal 0-10V
V2: 5V
R1: 1.5 kOhm
R2: 0.75 kOhm
R3: 1.5 kOhm
R4: 3 kOhm
U1 : 12V
U2 : -12V

Initially, the signal voltage was set from 0 to 10V using an ajustable DC power supply, the output gave the correct +-10V range. However, when connecting the PMT module, the output of the circuit will only range from -10V to 5.5V.
At this point I've kind of run out of ideas to what could cause this. Some hypothesis I have included grounding problem or some current limitation from the sensor that saturates the output. I however lack the theoretical electrical engineering background to properly assess the problem.
How can this problem be solved?
Edit:
Here are the full connections schematics. As shown, I've grounded everything together. Could this be a source of the problem?

Datasheets:
USB-205 ADC https://www.microdaq.com/downloads/dl/file/id/79/product/900/measurement_computing_usb_200_series_data_sheet.pdf
Hamamatsu HC120
https://mi-lasers.com/wp-content/uploads/HAMAMATSU-HC120_series.pdf
TL074CN
http://www.ti.com/general/docs/suppproductinfo.tsp?distId=26&gotoUrl=http%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Ftl074


texts:
I have some experience with Arduino, but for one of the devices I want to use something with more power (RAM/CPU power).

I already found out that some STM32F4 or STM32F7 models really with what I need, however, since I have no experience, I bought a (very cheap) STM32F103C8TT6 evaluation board.

I don't have it yet, but I'm reading information about it. I encountered mbed which seems a very easy way to program it.

However, in the list of boards I don't see any evaluation boards, mostly NUCLEO's or Discovery versions.

Is it possible to still use it? (like by selecting the 'similar'NUCLEO F103RB' or is mbed only supporting NUCLEO's (and lots of other ARM core devices) ?

The reason is that if the evaluation board does not support mbed, it's not really a good alternative to try if I can use mbed later anyway on the actual STM32 version I want.


texts: I need the RX line of my UART to be delayed about 1 ms, so I receive my data a fraction later. Are there simple, cheap components who can do this? Or would I need an extra external UART with a FIFO, etc.?


texts: Can I add output capacitance to a dc/dc boost converter to help with current spikes?

texts:
I have been playing around with achieving better power in my 30-year old RV. I want to create both AC and DC systems to provide power. This has essentially 3 routes from my battery to device:

Samlex 300W AC Pure Sine Wave Inverter. - Solid system.
12v to 12v or lower (USB). This works great too, pretty standard setup.
Greater than 12v via Boost Converter for me and my wife's laptops. This is where we are having issues.

The issue seems to be voltage drop as the computer draws more power. Most of our electronics work fine, but my 'beast' of a laptop is troublesome. It works perfectly fine on the inverter with the power brick it came with (which is rated 19.5v, 9.23A). I am currently typing this on the laptop and i have a current meter hooked up, and its pulling 2A. The boost converter is rated for 600W and doesn't seem to break a sweat, its maybe a degree about room temp.

When it hits about 5A the boost converter cannot seem to keep up (im assuming just momentarily), and the laptop disconnects from my power system and goes to battery. I initially thought the voltage was dropping but I cannot confirm this. This feels like an issue that could be fixed by adding more capacitance? IE, just slap a big car audio-style capacitor between the computer and the boost converter? Is this even worth it? I wonder if I should just use the inverter for this laptop, since none of our other electronics have issues.

Also, I am not an EE, but I will do my best to follow along with the more technical answers.


texts: Guide in choosing good overall PIC dev board

texts:
Our department getting grant to buy development board and I do not want them to buy same old FPGA board which we have 100 of and only 10 uses so far.

Need your enormous experiences in helping make good choice of development boards.

Friends with me interested in learning following PIC parts:

PIC18F4550
PIC18F46J50
PIC18F46J53
PIC18F47J53
PIC24FJ256DA206
PIC24FJ256GB106
PIC24FJ256GB210

In time we will also be interesting in dsPIC and PIC32 but all these right now together too much load, so beginnning only above.

I see Development Tools Home

Of all this the Explorer 16 100-pin board is interesting.

At $130 Explorer 16 Development Board has the nice option of interchangeable Plug-In Modules.

I assuming this means we can make our own PCB with the above PICs also and just pluggin them as Plug-In Modules?

Also finding the following boards, but confused if it possible to replace the PIC already present on the board?

$65 PIC24E USB Starter Kit
$60 MPLAB Starter Kit for PIC24H
$60 MPLAB Starter Kit for PIC24F

Development board from Microchip is recommended as easy to make dean agree, budget of around $200 or less per board


texts: Recommended Mosfets for switching purposes

texts:
I'm looking for common MOSFETs to do some experimenting with. They should be able to switch at least 3A at 15V, have a low on resistance for power efficiency and also be quite cheap.

I require all four types, that is P & N channel, both depletion and enhancement mode.

So far I've found the following enhancement mode MOSFETS:

N Channel: IRLML0030 or IRLML6244 (any recommendation
here?)
P Channel: IRLML9301

I think these MOSFETs will do the job. However, I'm struggling to find comparable depletion mode MOSFETs. Can anybody make a recommendation?

In general, is there a preference between using a N channel or P channel for switching purposes? I understand with a P channel the source is connected to positive while with an N channel the source is connected to ground. Practically does this make a difference?


texts:
I've bought a generic TEC1-12706 Peltier module and I'm having trouble making it work.

I wired it to a 12 volts DC, 8-amp power supply, and connected the hot side to a fan & heatsink with thermal grease. Turning it on, I noticed that condensation forms on about 70% of the cold side, but the rest is dry. Most of the cold side feels really cold, but one spot in the dry corner is too hot to touch! An infrared thermometer says the coldest corner (near the negative input wire) is about 2.5°C (36°F), and the hot corner diagonally opposite it (but still on the cold side) averages 46°C (115°F).

Having zero familiarity with these devices, I don't know if such a thing is normal, if I'm doing something wrong, or if the module is faulty. Is there anything I can try before I buy another module and wait weeks for it to come from China?

Picture (sorry for potato quality):


texts:
I am designing a system with a variety of sub-systems.
The voltage input is 24 VDC from a power supply (wall outlet).
For now, I try to compose it from mostly 5 V sub-systems:

SBC
relays
comms modules (interchangable WiFi, cellular, Ethernet via PCIe)
Small microcontrollers
Small sensors
LEDs
USB hub
RS422 drivers

Overall, the power consumption is estimated at 17 W. I don't see a need for high efficiency. Complexity is not very important but cost and noise immunity are. Low cost is important.
How do I determine the stability and configuration requirement of the power converter's output?
Should it be a DC-DC converter or (multiple) linear regulators?
Is it the data rate of the comms lines, the controllers' clock, the size of the board and the distance between the sub-systems and the DC stage?
Is there a methodology for determining it?


texts: Maximum current draw from 12v sealed lead acid battery?

texts:
I am currently building a "battery box", for camping, and kayaking, etc. It has a few different features on it, such as a 150W inverter, a 48W spotlight, 12V accessory outlet, and strobe lights. The inverter and the spotlight seem to draw quite a bit of power, 7 Amps and 3 Amps respectively. (correct me if that doesn't sound right.)

This will all be powered by an ExpertPower 12v 8ah sealed lead acid battery, however I do not know if it can handle the load that I will put on it. I tried looking around, but most people were using this battery for some sort of home security system.

I found a datasheet on the bottom of their website that I think would tell me that (http://www.expertpower.us/exp1280), but I cannot interpret it because of its complexity. If someone could also show me the process of calculating this, that would be great, as I am very eager to learn.


texts: Alternatives to breadboards for high-current applications

texts: I've read that solderless breadboards cannot handle more than 1 A of current or so. What kinds of alternatives exist to a solderless breadboard? Would a soldered board make a difference if I want to handle something like 5 A of current? What other options are there?


texts: Not able to view my code in MPLAB X IDE..!

texts:
I am trying to open my project (.C file) in MPLAB X ide (v5.15), but i cannot see my code, instead it opens up a rather weird window. It shows some history tab (of which i have no idea). I have attached a Screenshot. Could someone help me figure this out? How do i view my actual code in the editor?

PS: I took a backup of entire Hard disk of my old pc to new one and now I am trying to open those old .X projects in IDE installed on new PC.


texts: What is the reason for yellow tape on top of USB mini-B?

texts:
I have noticed that occasionally some USB mini-B connectors have what looks like a transparent yellow tape on their top.
It might be Kapton tape, but I am not sure.
As an example, please see the below image:

(source)
Usually, I leave this tape on.  I am wondering, does anyone know what this yellow tape is for?
All I can think of is for protection during soldering, but I am not sure if that's applicable for machine-soldered circuits.


texts:
So it's me working on a pedal again. I would like to add some equalizer effects on the pedal and found a fascinating circuit "Smash Drive":

As far as I know, maximum power with lowest effect is attained with high impedance input and low impedance output. However, I see in the circuit using 500kOhm pots up to 1MOhm pots. Do they result in a high input impedance? I have numerous 10kOhm pots. Are they better alternatives, with suitable capacitance values calculated to have same RC?


texts: Charging a Phone With a Lower Current-Rated Power Supply

texts:
My friend's iphone charger exploded. She was charging an iPad with it.
Since the iPhone power supply has a current rating of 1A while the iPad charges with a 2A current, many are blaming her that she didn't use the iPad charger since the iPad drew more current than the rated of the supply thus causing it to overheat and explode.

As far as I know the current rating of the charger used is simply the maximum current that it can deliver to the device. If the device can draw 2A, fine but it doesn't mean it needs to draw 2A by force. If the charger can only supply 1A than it is going to charge the device with 1A which obviously takes slower for it to charge than if the charger could provide 2A.

What is the correct reasoning please?


texts: 2 NPN Transistor Square Wave Oscillator?

texts:
I have built the circuit found here.

I substituted with 22K resistors at R2 and R3, and substituted C1 and C2 with .022uF capacitors. These are all the components I have lying around. Everything else is the same. Even the transistor part number.

I realize that these substitutions will affect the frequency of the square wave. However, scrolling through every possible time interval I don't see a square wave. I see a sawtooth wave.

I don't quite understand how this circuit works, so it was my intention to build it, then dissect exactly how it works, but I can't seem to even get it working correctly.

Current Waveform:

I'm unable to dissect the circuit and see exactly how it works, therefore I can't determine why I'm getting a sawtooth wave instead of a square wave. I'm sure that it has something to do with the substitutions but the reason this effects the waveform is my interest.

My time interval is at 20uS. The period of the wave is very nearly 18uS. That makes the frequency of the wave 55.555kHz? That can't be right, can it?

It also seems that what I have done by accident could be used on purpose to integrate a square wave into a sawtooth wave?


texts: Choosing accelerometer or displacement sensor for system

texts: I am working on an electro-servo motor system which can be seen as a similar in here! It is a shaketable system which converts acceleration input to displacement output. My question involves a bit theory; what kind of sensor should be use on these systems for feedback? Accelerometer or displacement sensor as LVDT? Question is totally based on sensor specifications but if we assume all specifications are same, is there any advantages to use an accelerometer instead of LVDT. In my opinion it is pretty sensible to use an accelerometer for feedback but i can not sure. I want to know your opinion.


texts: Eagle CAD license board limitation: area or edges?

texts:
I am deciding on which license to get for the currnt Eagle Cad 7.x (December 2015). There are a few options to consider regarding the PCB size limitations:

Standard: 160mmx100mm routing area
Pro: 4mx4m
Make Pro: 160mmx100mm routing area with variable height and width

This is as per their pricing webpage

My question is: what if I want to make a board 200mm x 50mm, do I need the Pro version, or can I do with the lesser versions in one design?
The dimensions are larger than Standard, but the area is smaller.

The question boils down to whether the license limits by the edge dimensions or the area size? The confusion comes in because the Make Pro version says something about edges being variable heights and width...

Anyone has experience pushing the license limitations?


texts: Can infrared cameras be used in the presence of light or is it compulsory it has to be used in the dark, to get a thermal image of the desired object?

texts: The question I asked could seem silly but I was wondering if there was a way of capturing the heat signatures of objects or people even during the day time. Also if we were to use an infrared camera, should we maintain the camera at a much lower temperature in order for it to capture the thermal information; i.e a cooling system?


texts:
I am working on GPIO external interrupt on LPC1769 board and having problems getting it to work. I have connected pin 2.11 to a push button and interrupt must be generated when the button is pushed. Any help is greatly appreciated. Thanks.. Below is the code,

#define EINT0      0
void EINT0_IRQHandler(void)
{
  LPC_GPIOINT->IO2IntClr = (1 << 11);
  printf("0interrupt\n");
}
int main(void) {

LPC_PINCON->PINSEL4 &= ~(3<<20);
LPC_PINCON->PINSEL4 |= (1<<20);

LPC_GPIO2->FIODIR &= ~(1<<10);
// LPC_GPIOINT->IO2IntEnF |= (0x01 <<10);
LPC_SC->EXTMODE = (1<<EINT0);

LPC_SC->EXTPOLAR = (1<<EINT0);

NVIC_EnableIRQ(EINT0_IRQn);

while(1)
{

}
return 0 ;


texts: Is there a special name for a potentiometer whose A-W or B-W resistance can drop to zero? I have a 1k +/-10% pot and I can only vary A-W or B-W resistance from 118 ohms to 1.2k. Note A, B refer to the outer pins and W the wiper pin.


texts: HM-10 Bluetooth: How to read characteristic data via serial commands

texts:
I'm programming an Arduino to use an HM-10 BLE device in Central mode to read a BLE Peripheral.  I'm able to discover and establish a connection with the Peripheral (via AT+CONnnnnnnnnnnnn command) but once the connection is established (received OK+CONN), the HM-10 does not respond to any further AT commands (including "AT") until the peripheral times out and I get an OK+LOST from the HM-10.

Can anyone shed any light on what I'm doing wrong?  I've searched all over and can't find a reference that details this low-level procedure.

Thanks for any help!