texts: Thermal Resistance, PCB Operating Temperature and PCB Self Heating

texts:
I want to understand a few terms.

My Questions :

What does Maximum PCB operating Temperature for a PCB in general depend upon?

Maximum PCB Operating temperature depends on Tg (Glass Transition temperature). Above this Tg value, the base material may deform or the properties of it may get changed. Am I correct?

If not, On what other factors does Tg depend upon?

If I am correct, how to find the value of Tg? Is it different for different dielectric materials?

What does PCB self heating mean?
My understanding - When a board is in normal working condition, the temperature of PCB increase due to the active working components and hence raise the temperature of the PCB. Am I correct? Please help me understand this with the correct definition of PCB Self heating and what would be default value that needs to be taken as the PCB Self heating temperature as a thumb rule for worst case calculations?
Thermal Resistance Parameter (Junction to Ambient & Junction to Case)

For example, lets take a part which I am using. TPS54260 - HVSOP Package.

In the above image, we have thermal information of Thermal Resistance between Junction to Ambient as 62.5degC/W and Junction to Case as 83degC/W.

Does it mean, if the IC dissipates 1W, the temperature at the Junction of the IC= (62.5+Ambient Temperature)degC ?

And the temperature at the case of the IC = (83+Ambient Temperature)degC ?

Is my understanding correct?

And what is the reason that Junction to case thermal resistance is higher value than junction to ambient temperature?

Junction to Ambient thermal resistance is just the sum of all the internal thermal resistances, right?

Please help to understand


texts: Inverting or Differential Amplifier? (Or neither?)

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I have been searching for how to calculate Vout in the following operational amplifier circuit, but so far I have come up empty.

I feel it is either an inverting amplifier or a differential amplifier. I have yet to find an equation for an inverting amplifier that incorporates an external voltage source between the non-inverting input and ground. Also, if this is a differential amplifier, then the just-mentioned external voltage source could be the result of a voltage division between R2 and Rg according the following circuit.

I should then be able to use the following formula to calculate an output voltage.

This gives a Vout of 100 mV. Does this seem right? It is interesting how Vout = V1 = VRg.

Can anyone shed some light of understanding upon this conundrum of mine?


texts: How can I safely power both an Arduino as well as an electromagnetic lock with the same power supply?

texts:
I work for an escape room business, I create tricks and props using arduinos. Most of the time the Arduino has to take input from a player using buttons, sensors, etc. and locks/unlocks and electromagnetic lock for either a door or drawer or something. The locks are always controlled via relays and their respective arduino.

The problem is that installation can get quite messy and unruly since we have so many locks and arduinos that need power supplies. So for now I've been using a 12V power supply that powers the arduino through a 7805 voltage regulator as well as the lock. .

Note: I am using a relay module board that has all the necessary components for reliability such as the transistor before the coil and an optocoupler.

However, I've been having problems with this circuit.

The voltage regulator gets very very hot, even with a heatsink on it.
When the relay disengages the lock, the arduino becomes unresponsive and requires a reboot to work properly again.
The power supplies I am using are 12v 1000mA. And the electromagnetic locks I am using use up to 500mA when engaged.

My question is: is there a more reliable or easier way to power both the arduino and electromagnetic lock using the same power supply.


texts: Replacing a logic OR gate with two diodes

texts:
I am trying to build some basic circuits to figure out how things work (mostly for fun). This one caught me off-guard today.
I want to build a module with three pushbuttons. Each one turns its own LED on and switches two other LEDs off. Initially I made a little simulation in Circuit JS:

I haven't tried actually building it, but I presume it works. So the idea is that each pushbutton activates two "reset" inputs of other buttons' NOR latches.
I thought to simplify this circuit by using diodes instead of OR gates. However, when I changed one gate, I got the following:

Why so? I fail to understand how voltage can make it through the upper diode. Initially I thought that even a resistor and a ground connection isn't necessary in this case, and I can simply connect two diodes to a NOR latch. However, it seems that even a "proper" diode OR won't work here.
(Of course, maybe Circuit JS is just tricking me, but I trust it more than my knowledge in this case).
UPDATE. Thanks to TimWescott I made it work on a simulator. It seems that additional pulldown resistors were necessary. Here is the final build.

P.S. Original schematic, Diode version.


texts: Does Autodesk Eagle 9.XX support project files sync like Fusion 360?

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I am using Eagle 9.0.1 and I have been searching about syncing project files and accessing my projects files from multiple places but I could not really find such a thing anywhere in the software and it is not happening automatically.

I am asking this question because when you open the program in the main window, you have this "GO ONLINE" so I thought it is the same as Fusion360.

My question: Does Autodesk Eagle 9.XX support project files syncing(similar to Fusion360)?


texts: What are the Advantage and uses of voltage follower circuit over emitter follower

texts: Can I use voltage follower and emitter follower for same purpose


texts: phase of current relative to voltage using a single resistor

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I am trying to simulate on Multisim the phase of current relative to voltage using a single 1k resistor. However I can't understand how can I do that.

In this example the oscilloscope shows me voltage different, but I need to see current relative to voltage, not volts to volts.

Thanks.


texts:
I have followed a process to make a PCB, whose link is given below. I have followed the every process as mentioned with correct proportion of chemicals. But, unfortunately, this didn't work (traces were not stick to the copper board). I have used glossy paper in this experiment. What could be the possible reason of my failure Or this process is a invalid process ?

LINK


texts:
I am looking for some advice or pointers as to whether I need to solve this problem and if so how difficult it is to do so. I have read a post which made an off the cuff remark about needing to using an OP-AMP to be able to use the full range of an ADC is certain circumstances. I think I am in this situation but I have never used an OP-AMP before.

I have a temperature sensor (thermistor I guess) that I am reusing from a pool heating system. I have tested and measured the resistance of the thermistor at 2deg C at around 493k and at 72deg C at 398k. When I hooked it up to my little voltage divider circuit that will feed into a MCP3002 ADC I used a 1M ohm resistor and this gave me 2.21V at 2deg C and 2.36V at 72deg C.

So the issue is that I will only be using a small amount of the ADC range. Using online calculators and reading other posts I see I should drop the fixed resistor to around 450k which I will do but this only increases the voltage range by a small amount.

I can probably get by with this range as I don't need much more than 2 degrees of precision but I thought if it isn't too difficult I might see if I can add to my currently simple circuit (voltage divider and ADC) to increase the used range of the ADC. Clearly I am new at this so please be gentle with your explanations! Thanks!


texts: Wake-Up Dormant Electric Motorcycle Battery

texts: I have a 2010 Zero DS electric motorcycle with a very depleted battery.  I estimate it has been off charger for approximately 1.5 years.  The bike has been stored inside a garage in a dry environment.  I have the original charger.  Is it safe to simply plug in the battery and charge?  Should I take some other steps to "wake-up" the dormant battery ahead of full charging?  Thanks in advance.


texts: At what internal resistance is a battery considered dead?

texts:
I got me a new fancy battery charger that measures the internal resistance (if that's the right term) of the battery and I am trying to learn how this works.

My current understand is a higher internal resistance means the battery will still work but it might not be able to provide enough power if the device draws more power. The fire alarm might look fine for example, since it needs little power, but it might not sound in case of a fire since the battery's internal resistance prevents it from providing enough power.

I am testing some old and new rechargeable batteries and indeed, my new AA battery has a 27mR (new eneloop) and the old one shows 127mR (years old Energizer). Meaning the old on has a higher internal resistance. Correct?

Now, I suppose the old one is so old I should throw it out but how do I know where to draw the line? 30mR might be really good but is 90mR? What about 100mR?

In short: how do I know at what threshold a battery should be considered "dead"?

Update:

I looked at the datasheet of the Energizer as proposed in the comments. It gives a "Internal Resistance" of 100 milliohms for a charged battery and an "Impedance" of 35 milliohms for the same charged battery. Which one is the the number I need here?

If I take the 35 milliohms the battery would be good if it read between 28 and 42 milliohms (+ and - 20% as shown in the sheet). Do I get this right?


texts: Concentrated Ozone Treatments for COVID-19 Sterilization: What levels and duration are safe for consumer electronics?

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Operating a critical IT service for necessary businesses brings some risks at this time that need to be mitigated. I have some powerful ozone equipment used to sanitize / sterilize rental property and am considering using this within some enclosures to facilitate safe drop-off and pickup zones of computers and various electronics for customers.

Are there any studies or solid experiences that demonstrate safe levels (and duration) of strong ozone exposure for consumer electronics?

I don't want to destroy any circuitry or even polymer seals for batteries, keyboards (rubber springs), etc. and thus want to make sure I research this option thoroughly before implementing this.


texts: How to use a transistor to pull a pin low?

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I'm trying to make a simpler approach to flash LPC1114 MCU.

If the MCU is reset while pin1.1 is held low it enters bootloader mode. I'm using a simple arduino sketch to drive reset & 1.1 pins via serial line.

It was pretty simple with reset:

simulate this circuit – Schematic created using CircuitLab

I've just replaced my button with a transistor and it did the trick.

Now, with 1.1 pin I have the following setup:

simulate this circuit

i.e. by default it's not connected to anything, on button press it's pulled down. Well, replacing the button with transistor doesn't seem to work.

Any hints on how to fix that?


texts: What's the difference between these plugs?

texts:
I'm not an electrical engineer, but I play one on TV. Can you help me be more realistic?

Our facility has three items that run on three phase 208 and plug in at a temporary building using CS (California Style) connectors. We are in the process of speccing a new building. To give the users maximum flexibility in where to put their stuff, I want to scatter five of these receptacles around the new building. I just realized that the three equipments do not have the same CS connectors, oops.

Two of them have a CS8365, and the other one has a CS6365. UH-OH! We have the competence to change out the connectors to match each other, but before I recommend that, I want to better understand the differences to make sure I don't create a safety problem.

Here are some data on both of these connectors:

https://www.hubbell.com/hubbell/en/Products/Electrical-Electronic/Wiring-Devices/Locking-Devices/50A-Twist-Lock/CS8365/p/1634245

https://www.hubbell.com/hubbell/en/Products/Electrical-Electronic/Wiring-Devices/Locking-Devices/50A-Twist-Lock/CS6365/p/1634242

I can see in the description that one of them claims to be for 250 "delta" power while the other claims to be for 125/250 power. That's all good, and I think I understand it, until the next sentence--they both claim to be "3-Pole 4-Wire Grounding". Now that does not make sense....the 125/250 one seems to be claiming to have a neutral, so how does that add up with still only four conductors?

Now, my bottom line questions:

Would it be safe to remove a CS6365 from a Harrington Hoist VFD246 series crane and replace it with a CS8365?

Alternatively, would it be safe to remove two CS8365 from a Toyota forklift battery charger and a Grainger Speedaire 13G709 air compressor and replace them with CS6365?

As far as I can tell, all three of these devices are straight 208 three phase, with no need for a neutral or 115 power, but I give the model numbers to let you all educate me if needed.

Thank you for your time!


texts: Smallest Magnetic Relay and how to choose the Ampere rating

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I am building an automation system, where I don't have much space, so I require really small relays, 3.3 or 5 VDC controllable relays.

I need to connect it to say a lamp, or a fan, equipment's that draw less than ampere and work at 230 VAC. The 5 V 10 A relays are really big, and I need some advice on choosing the smallest relay and want to know the minimum ampere rating they should have.

Please share your ideas, thanks.


texts:
I have a device that runs at 5v at 1amp. I am looking for a way to increase battery life without modifying the device itself.

I know that some electronics (for instance a 5v wall wart) allows for 2.1amp output at 5 volts and have 100-240v inputs which draw 0.3a. Could I apply a similar concept with a voltage regulator or some other device to work with batteries?

For instance if I was running off 3 lipo cells in series (11.1v), if I ran my device off a 5v regulator from the 11.1v battery source, would I draw less current from the battery source (and thus extending battery life) than if I were to use a 5v battery source directly?

Any explanations or math/logic behind this concept would be appreciated.

Thanks!


texts: Will the below circuit act as a one-way current restrictor to allow 100A to flow out of the battery, but limit charging current to 10A into the battery from the alternator?


texts: Voltage in a ring circuit with induced current

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Supposed I have 3 resistor, R1=1 Ohm, R2=2 Ohm, R3=3 Ohm. I connect them with copper wire to form a ring R1-R2-R3-R1
I used a device to generate changing magnetic flux in that ring. So there must be induced current flow in the ring.
The problem is if I measure voltage between two ends of R1, what would that voltage be ? Since it is closed circuit then Ohm law indicate that I  *R1 = I * (R2+R3)
EDIT: As suggested in comments, this question duplicate Can two voltmeters connected to the same terminals show different values? Circuit with induced EMF


texts: Weight measurement using load cell and process indicator

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I need to measure 0-200kg using a Baumer SAS PA418 process indicator. The manual is in french, I tried to use google translate but understand very little. A load cell is attached with the indicator which is PST-101 (200kg). The problem is I have no background on these device or process, I am a CSE background. Do you have any suggestion where I should look for or how to set the device step by step?

Thanks for your any help.


texts: Voltage gain in common emitter BJT amplifier (specific example)

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What is the AC voltage gain in the following common emitter BJT amplifier? We are also given that for the BJT \$\beta_{DC} = \beta_{ac} = 150\$.

simulate this circuit – Schematic created using CircuitLab
Full disclosure: this is question 19, p825 in Electronics Fundamentals, Pearson, 8th Ed.
I'm asking because my answer does not agree with that of the book, and I can't see the fault in my calculation:
$$V_B = 8\frac{3.3}{3.3 + 12} = 1.725V$$
$$  V_E = V_B - 0.7V = 1.025V $$
$$  I_E = 10.25mA$$
$$  r_e = \frac{25mV}{10.25mA} = 2.44\Omega$$
$$  A_v = \frac{R_C}{r_e} = 123$$
NB we are given the formula \$r_e = \frac{25mV}{I_E}\$ earlier in the book (without derivation).


texts: 8085 ; High impedance state of lower order address/multiplexed data bus during memory read and write machine cycles

texts: The two pictures are of memory read and write machine cycles . Could somebody please explain why in memory read cycle the lower order address / multiplexed data bus is in high impedance state at the positions I've marked with red in the timing diagram while in memory write cycle it is not ?


texts: KiCad how to export oval PCB hole as a drill file?

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Using KiCad, is there a way to have a pad with an slot shape (referred to in KiCad as "oval") be exported properly as a drill (.drl) file?
The pad in KiCad looks like Fig. 1 below.
But after exporting the PCB layout to the gerber and drill files, it seems to only process a single round hole, rather than the entire slot/oval, as shown in Fig. 2 (as seen from a separate gerber-viewing program).
I was previously able to work around this problem by modifying the footprint to have multiple smaller circular drills instead of a larger slot/oval one and got it successfully fabricated.
Are there more efficient alternatives?
(Fig. 1: pad in Kicad)

(Fig. 2: exported pad in gerber viewer)


texts: How can I check that the voltage output from this voltage divider is 2.25V?

texts:
I was learning about voltage dividers from here, and I decided to try a test circuit with my Radioshack learning lab. With an input voltage of 4.5V and two 1000Ω resistors, I expected the voltage output would be 4.5*(1000/(1000+1000)) = 2.25V.

After looking at this, I thought that the only way to measure the voltage output from the divider was to measure the voltage drop of a resistor (otherwise I'd just get a 0V reading), so I added a 1000Ω resistor to the circuit (R3 in the drawing below). I measured the voltage across this extra resistor, but I got 1.48V for an output voltage. What I found odd was that when I used higher-resistance resistors, the voltage drop output got closer and closer to 2.25 V (the highest I did, 1MΩ, led to the 2.25V reading I wanted).

Can I use resistors like this R3 to test the voltage output coming out of this voltage divider? If not, how can I check by measurement that this voltage divider gives an output of what I'm sure is 2.25V?

simulate this circuit – Schematic created using CircuitLab


texts: Why is the voltage drop created by a current source added?

texts:
A few days ago a similar question was asked for the simple circuit below consisting of three elements in series (voltage source, resistor and current source). Despite professional explanations, the OP could not understand why in the lower diagram the voltage drop across the resistor was added to the source voltage and not subtracted.

I was watching the discussion with interest because I have encountered this circuit in many interesting electronic circuits. I made a brief comment on the nature of voltage and current sources... and at this point the OP impulsively asked me to explain why VR1 was added to V1 to obtain Vo. How can you not respond to such a touching request? I started thinking about what the OP's problem with understanding was and how to solve it.
Unexpectedly for me, however, the OP removed his/her question. But I still decided to finish my answer and publish it under a more precise question...


texts:
I made a very simple circuit like so:

Both R1 and R2 have the same value (100K).
The capacitor is a 100u.
When it’s charging, it takes about 20 sec to get from 0v to 5.05V (measured at the capacitor) but when I press the button to discharge it, it takes more then 35 sec to get from 5.5 to 0V...
I would expect the charge to take longer as it goes throught R1 and the diode (which I guess has a small resistance too) while it only have to go through R2 when discharging.
Why is the discharge longer ?


texts: Atmel SWD. Enabling normal GPIO function on the SWO pin

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I'm trying to make a project using the ATSAM4LS2A microcontroller (Cortex M4), and i'm using the AtmelICE debugger. The thing is the pinout for the SWD mode also has, beside the SWCLK and SWDIO pins, also the SWO pin (which should be optional). The problem is that the SWO pin is the same as the SCLK pin that i'm using for the SPI (trying to talk to a CC1101 transceiver).
Even if i don't connect the SWO pin, when i'm debugging and trying to read a byte from SPI i always get 0, even though i'm pretty sure it should be different.
So, my first question is, how would i be able to test that the SCLK pin in working in SCLK mode and not SWO mode?
Second question: How can i disable the SWO pin in case it isn't disabled automatically when it is not connected? (if possible).
Thanks.


texts:
Like the title says, can I do this? I got two schematics in mind about how to wire these up, which  one is the correct one?
This one is straightforward, but will it actually work if connected to load?

I think this one will interfere with the MPPT of CN3722, but I am not sure

The CN3722 and XL4015 in the schematics are in module form not bare ic, but these are the datasheets:
http://www.consonance-elec.com/pdf/datasheet/DSE-CN3722.pdf
https://www.elecrow.com/download/XL4015_datasheet.pdf


texts: Measuring current output of a diode driver

texts:
I have a laser diode driver chip that can produce DC currents up to 200mA. The current is adjusted by a potentiometer on the driver chip. The driver chip has four pins:

inputs: GND, SUPPLY
outputs: LD+, LD-

My approach was similar to the suggestion here. But how can I measure the current leaving the outputs?
Can I connect a large (how large?) resistor between the LD+ & LD- pins and put a shunt across this load resistor, then measure the voltage across the shunt? Do I need a load at all? I don't want to connect the laser diode in case the current exceeds the diode ratings.

EDIT: Spec Sheet of the driver, if it helps.


texts: Why is a flip-flop also known as a latch?

texts: I am new to digital logic design and would like to know why a flip-flop is also known as a latch?


texts: What is the current rise time of a discharging capacitor?

texts: There are many questions about capacitor discharge rise time here on the electrical engineering board but all involve transistors or are oscillating circuits rather than a purely shorted out capacitor. The capacitor discharging equation assumes that current at time zero is at peak. However, I find it difficult to believe that the current rise time is effectively infinitesimal in real capacitors. Does the current of an RC circuit truly peak at time zero?


texts: How can I determine the charge voltage on my HyperMac battery?

texts:
I was gifted a HyperMac MBP-150 lithium ion battery about 1 year ago (150Wh) with very little information about how to use it. I was never was able to charge using a variety of 12V DC adapters (although it appears to accept standard 12V DC input). Finally I left it in a back room and forgot about it, only to realize today what a really nice battery it is ... if I could charge it.

I now suspect that the battery might actually charge using high voltage AC power.

See this FAQ where it says:
Can I charge my HyperJuice external battery with DC charger?

You need to have an inverter to convert 12v DC to 110v AC in order to charge HyperJuice battery.

Can I charge the HyperJuice external battery world wide?

Yes, every single HyperJuice battery comes with AC 110-240v power transformer, which allow you to recharge it in world wide. Plus, we also include the right power adapter in your reside country.

Although this FAQ sounds like promising information, I would like some more confirmation before I clip a spare 12V DC charger and wire it directly to the wall.  Since the battery has a CE mark, is there information about charging it available inside some sort of database?  The battery simply has a jack labelled "charge" and a jack labelled "dc out", as well as a "usb 5v out".  On the back it has a sticker saying "rated 14.5v~18.5v (4.5A max).  No info about the charging voltage.

Anyone have any suggestions?  Should I just go for it and plug it into the wall?  My gut feeling is that it is a stupid thing to do without getting more reliable information first.

EDIT 1:  I think the big question here is what is going on in the "magic box" typically supplied with these HyperMac batteries and used to modify the Apple charger.  Is the "magic box" really a DC to AC inverter?  If this is the case it seems so wasteful.  The design logic is what is throwing me off and causing me to second-guess my intuition here.

EDIT 2:

I think now maybe I understand the design logic with these photos.  The original 6.5V DC Apple charger is being used for convenience, not efficiency.  When the HyperMac battery is being charged, 6.5V DC is converted to AC to charge the battery.  The MacBook can still be charged with this original 6.5V DC Apple charger (wall AC to 6.5V DC).  The MacBook can also be charged using the HyperMac Battery.


texts: How long would the capacitors in an iPhone power adaptor hold potential energy?

texts:
I was curious as to whether one could potentially get a shock after touching, with sweaty hands, the prongs of an IPhone power adapter upon unplugging it. If possible, how long would this charge take to dissipate on it’s own? Do these small capacitors actually hold energy for longer than a few seconds?

Thank you


texts: Why is impedance represented as a complex number rather than a vector?

texts:
I am trying to understand why impedance is not represented using vectors.
I assume it is due to complex numbers having the property that
$$j = \sqrt {-1}$$
but with my limited knowledge I can't see how this relates to impedance or why this property would be desired. I'm not sure what reactance has to do with the square root of \$-1.\$
Could someone explain to me why complex numbers are used rather than vectors?
An intuitive answer is fine; I don't need a complex proof.


texts: How to use this latching relay to simulate button press?

texts:
I'm using a PIC on a 3v3 circuit to simulate a (normally-open) button press to turn on a machine. To do this, I have some Fujitsu AL3W-K relays. Mine appear to be the double-winding latching type. The nominal voltage is 3V, set voltage is 2v5, and reset voltage is 2v1.
I am new to electronics and I haven't used this type of relay before. It isn't clear to me from the data sheet which pins to connect to my ground and the output pins from my PIC to switch it on/off, and which pins to connect to my hotwired button. There's a diagram that shows a "+" and "-" end of the relay, but connecting those to gnd and 3v respectively doesn't seem to change the connectivity of the pins in between. Maybe I'm not reading the datasheet properly but I am not able to find which pins are which.
How should I connect the pins on my relay in order to simulate button pressing?


texts: PCB Stack-up Window in Altium on the plane layer

texts:
It is a common feature of multi player PCBs to have a small window where one can look in and see a number for each layer of the PCB. It's used in manufacturing to show that all layers are included I believe.

We use Altium, which is easy enough to put this window in a signal layer, as it just needs to be added. However, when we come to plane layer it seems to get complicated. We can put a window into the plane without issue, but we cannot find any way to get numbers written on it.

Talking to our Altium support, they don't seem to have any ideas either. Has anyone done this? Does anyone know how to add the required text to this window?


texts: How do I design a through-hole pad in Altium Designer?

texts:
I want to define a custom component (TO92 temperature sensor) in Altium Designer with through-hole pads (0.7mm hole diameter, 1.27mm pitch). What is the right way to do this? I I created the schematics (all fine) and PCB library entries.  I ran into the problem that I have no clue how to generate a pad with a hole in the PCB library, this is what I tried:

Approach 1 (using via):

Problem: Vias are not recognized as pads and therefore cannot be associated with a name/denominator resulting in vias not having a net in the final PCB document. I guess I cannot tell Altium "treat this via like a pad and give it a net"? Since it is not a pad, manually assigning is also no option via Design->Netlist->Edit nets

Approach 2 (using vias on top of pad)
Problems:

too big diameter of pad solder mask: It seems small pads are not possible when choosing Place->Pad since the pad is always huge, even when choosing a diameter of e.g. 0.1mm:

(note the tiny hole of 0.1mm in the center whereas the outer ring is still huge with over 1mm diameter).
unsure how to get hole: I put a via on top of a pad, this seems a pretty inelegant solution, what is the standard way to do this?

Thanks for any help/suggestions for directions!
Sebastian


texts: Controlling high current (1000A) with MOSFETs

texts:
I am currently designing a capacitive discharge spot welder and am running into the issue of switching.

I plan to use a few super capacitors in series to discharge around 1000A in a very short period of time (most likely less than 100 milliseconds). I plan on charging the capacitors to around 10V.

So I essentially need a device capable of delivering a short pulse of very high current. I do not want to dump the entire charge of the capacitor in one go, so SCRs are not a solution to my issue. I have been looking at MOSFETs, and this one catches my eye: http://www.mouser.com/ds/2/205/DS100728A(IXTN660N04T4)-1022876.pdf

However, I am unsure of how exactly to interpret the datasheet. Is the MOSFET capable of driving 1800A as its pulsed drain current states? Or is it limited to 660A (or even 220A), forcing me to wire a few of these in parallel? Or will one of these MOSFETS be fine? According to my preliminary calculations, a lone MOSFET connected directly to the capacitors without any other resistance would be dissipating around 900W, which seems to be within the range of the data sheet.

So essentially, am I interpreting the data sheet correctly, or do I need to order a few of these MOSFETs (and if so, how many would you guess?)


texts: How to detect multiple digital sensor with one micro controller input?

texts:
I would like to connect multiple TSSP4038 sensors together in such a way that I only have one output (let's call it Y_out), if any of the sensors output is HIGH then Y_out is also HIGH (regardless if some of the other TSSP4038 sensors are low).

According to the datasheet, the TSSP4038 output pin supplies a current of 5mA and a voltage of -0.3 to 5.5 (depending on Vs).

I am thinking the best way to do this is to connect a diode to the output of each sensor (so they don't drain into one another), then connect the nodes after the diodes together to a Pull-Down resistor. If any of the outputs is HIGH then then a voltage across the resistor will be detected.

Would this work? Any suggestions on a better way to do this?


texts:
I'm not good at electronic engineering.
But i have to make led transmitter(for visible light communication).
Now, i use arduino and mosfet like this picture.

I should choose proper power supply(external power) and COB(chip on board) led.
I will buy 24v power supply(output 23v, 52.8w, 2.2A | input 86~264VAC).
Then, what should i check when choosing cob led?
And, Can you give me some proper led list for me?


texts: CANBUS, understanding if a tranceivers is 3V compatible or not

texts:
I am looking for a way to tell if a CANBUS tranceiver chip I have is 3V-5V IO compatible or 5V-only.
There are many situation were this applies, like non-readable chip markings and "alternative" chip codes from "alternative" vendor (quotes to include "non-original" scenario).
TJA1051 datasheet distinguish between 3.3V (IO) compatible silicon, like TJA1051T/3, and 5V-only compatible ones, as TJA1051T/E.
Same applies for ATA6561, which is 3V IO compatible, and ATA6560 which is not.
This probably stands for other tranceivers out there, too.
These tranceivers, sharing the same form factors and pinouts, differentiates 3V-5V and 5V-only IO compatible versions through VIO pin.
For TJA1051, section "VIO supply pin" states: "For versions of the TJA1051 without a VIO pin, the VIO input is internally connected to VCC."
For ATA656x datasheet says:
Note 1: Pin 5: ATA6561: VIO
               ATA6560: NSIL (the VIO line and the VCC line are internally connected)

Question is: given VIO and VCC are internally connected in 5V-only versions, can I test continuity between VIO pin and VCC pin to be sure that chip is a 5v-only version and viceversa, knowing a tranceiver is 3V-5V IO compatible if no continuity is found?
This way a simple test with a DMM can help distinguish the chips without even powering them.
EDIT: Ooops, ater Jeroen3 answer I now realize that my question is about logic and not electronic, in addition to being impossible, I should have tought a little more about the problem before asking, thank you. I still wonder if there is a wat to tell a TJA1051T/3 from a TJA1051T/E without reading the markings, but I understand this is a different question.


texts: solar powered arduino USB link light blinks?

texts:
I have a OSEPP MEga 2560 R3 Plus. It's connected to a 7.2V200mA solar panel SC20072. I don't know fully what I'm doing, but the power light on the board lights up. However, the USB TX and RX lights blink like it's trying to boot and then the Link light just keeps blinking. The Arduino never actually seems to finish the boot and start running my program. It works just fine via USB and the USB light pattern is the same while using USB, but the link light eventually stops blinking. This makes me think it's waiting on the USB link, but I don't know.

What's the problem? Am I not properly powering my device? Do I need to circumvent USB boot-up somehow? Thank you.


texts:
I'm in a lab and for some reason I cannot replicate my results on LTSpice.
I have gathered data from an experiment where I built the circuit shown in Figure 1. I then took that data, plotted it in Excel and found the polynomial trend line, see Figure 2. However when I try to replicate this experiment in LTSpice, the plot does not match, see Figure 3. I believe my circuit is wrong, but I'm not sure what to change. Any suggestions?

Figure 1: Circuit built in the lab

Figure 2: Recorded values of the ammeter and voltmeter plotted showing polynomial trend line

Figure 3: LTSpice circuit and incorrect plot


texts: How do I calculate rise times for a push pull GPIO with load with hand calculations?

texts:
simulate this circuit – Schematic created using CircuitLab

This is a simplified example of a push pull GPIO found in most microprocessors, with a load attached.

Using the capacitance and current values from the datasheet that is usually given in a microprocessor datasheet, how can the rise time be calculated?


texts: Correct terminology for 'clock' that doesn't oscillate?

texts:
What would be the correct term for a clock input that isn't made to oscillate per se?

In an attempt to only allow input A to have any effect on a circuit at a chosen time, one could AND it with another input B.

Would input B still be referred to as a clock if it were to only be switched on and off manually?


texts: Isolated AC line voltage monitoring circuit

texts:
I found this https://www.edn.com/isolated-circuit-monitors-ac-line/ circuit in my quest for a low cost isolated AC line voltage monitor and constructed it. On testing however, I am not getting the correct voltage as expected from the formula provided.
Ve is supposed to be 48V but my calculation by rearranging the second formula to get Ve, is giving around 133V.
Is the formula wrong or have I made a mistake somewhere?
Additional information:
I changed the values of R1 and R2 to 100k each as I found the 10k 0.5W resistors were getting quite hot and the 200k obtained should provide enough current to turn on the optocoupler. I used EL817 as I had a few and the diode is 1N4007.
AC RMS voltage is 230V for which I got a low pulse width (Ttotal in the formula) of 0.0073s (it should be about 0.0091s if Ve is 48V).
I used an STM8S microcontroller's input capture for measurement. Unfortunately I do not have a DSO to verify the pulse width. I did verify that the pulse width was changing using a variac and an old analog scope.
Also are there design errors in the circuit which should be corrected?


texts:
So I'm attempting to diagnose what's wrong with my daughters light up fidget spinner after she dropped it on the floor (and if possible fix). But I seem to be having a failing at electronics 101 and am trying to work out what I'm missing!

The PCB looks incredibly simple, 3 batteries in series, an LED and 2 components that sound like switches with a ball bearing inside - which would make sense, activating the LED when they spin. I've put together what I think the circuit looks like where SW1 and SW2 are those rotary switches. I've put a schematic for how I think it works, and a photo of the PCB below.

simulate this circuit – Schematic created using CircuitLab

I've tried checking a couple of things with a multi-meter. Using a connection test, that actually pushes enough power through the LED to confirm that it lights up OK. Using a volt-meter between A-B I read 0V and between A-C I read 3.1V.

What really starts to baffle me though, is that I've tried shorting the two connections at point C, using my multi-meter probe (and tried a screwdriver) neither of which light the LED - which I don't understand?


texts: How to dissipate a static charge from a 3D Printer?

texts:
I have a 3D printer, whose extruder I suspect is generating a static charge when the filament is dragging past other plastic parts (nylon). This is bad for the electronics. I want to try and dissipate that charge to earth however I am not sure how that is done. Once the PLA gets to the barrel, the barrel will conduct the charge to earth (as the machine is earthed), however those nylon surfaces do not contact anything conductive.

Question: How to dissipate a static charge on the nylon? Or How do you keep the electronics safe from this charge?


texts:
I have a PIC board that I want to power from my mobile phone when the phone is on and keep the phone topped up from a solar panel.

I think I want to:

access battery terminals in phone directly (with the phone back off) - I can see the battery terminals have 4 v
have a switch in the power lead between the battery terminals and PIC board controlled by the phone (working on this)
top up phone battery from solar panel - I'm not sure about this - can I just wire up a 5V solar panel?

What do the battery terminals want to 'see' voltage wise to charge?  do I have to prevent overcharging?


texts: Unstable Oscillation in Pierce Oscillator

texts:
Here is a Pierce Oscillator that I built to oscillate at 16 MHz. I put the parts on a breadboard (I know its a bad idea, but this is what I have with me). And here is the result:

As we can see I am getting a maximum frequency of 1 MHz, and if I increase the R6 resistor value to around 500 to 1k ohm, I do get a response where one moment I get 16Mhz frequency but the next moment it falls back to what I have in the above oscilloscope screenshot. And it keeps on moves back and forth between 16MHz and 1MHz frequency, i.e. the oscillation is not stable.

Increasing R6 value is going to contribute more phase (the crystal and R6-C13 combination must provide phase of 180 deg), which means the effective inductance value does not need to go higher, i.e., crystal is going to resonate very close to series frequency.

I have kept the load capacitance to be 16.5 pF, as breadboard is going to add around 3pF to that which should take me to 20pF, as required by datasheet.

Having said all that I can't understand why the frequency is not stable, one moment it is 1MHz and next moment it is 16MHz, and it keeps bouncing back and forth between these two frequencies. Any light on this would be greatly appreciated.

NOTE: Here is an answer something related to this, but this does NOT answer my question.


texts: Carry Look ahead adder Propagate & Generate Outputs

texts:
I am taking comp architecture course, and we are given a task to write 32 bit look-ahead adder in VHDL. Instructor provided the instruction and diagram.
While reading, Wikipedia article, I stumbled on the following diagram.
Since C4 is already available, what is the purpose of PG & GG outputs, ??? I am trying to find, if the instructors diagram is complete.
Thanks !


texts: Help identifying 6 position (2x3) computer connector

texts:
Need help identifying this connector. I am actually looking to purchase a 6 (2x3) position connector of the same kind, so need help with type and where to buy (Mouser, etc).

This is from an IBM server (USB front connector). I want to build one such cable, but with 6 positions.

Any help appreciated!


texts:
I want to drive a 12v inductive load with arduino (a motor) . This device has 3 wires a common GND and one wire to go in one direction an another one to go on the opposite direction, as it has a common GND If I understand it correctly I can't use a NChannel mosfet. following diferents ideas on the internet I came up with the following design:

A few questions :

Why is R4 really necessary?
What's the use for Q1 , I have seen diffent designs using only Q2, if I was driving a 5v device (the same as V as the arduino could Q1 being removed?


texts: Simulate Intel FPGA for software development

texts:
i'm currently working for a project for my university. It's about the Intel SoC Embedded Development Suite, and for this i need an actual FPGA board. Unfortunately i'm unable to buy a board, because it costs way to much, and my university does not have any(my mentor said it's being ordered now, but it would take a while before the board arrives); so i really want to simulate the board. Is there any way to do this?

Thanks in advance


texts:
So I had some question about the differences between Turnkey (they supply the parts) and kitted (I supply the parts) PCB assembly.

When I am making a batch of about 500-1000 PCB's, which option is cheaper, which option is more reliable, and how do I let the company know which part to put where?

Any information about the differences, advantages, and problems with each will be greatly appreciated!


texts: Calculate properties of electric generator?

texts:
I've got a miniature DC generator with 10 coils.

If I knew the generated power and the size of the rotor, how would I calculate its RPM?
Which other variables would I need?
Is there a general formula or some online simulating tool that I can use?


texts: Zero and pole of transfer function spaced for one octave

texts:
Here is my task:

Find ratio R1/R2 so that zero and pole of transfer function are spaced for one octave.

I found zero and pole, but what "spaced for one octave" means?


texts: Effect of PWM mode of DC to DC convertor

texts: When using PWM from microcontroller to control DC-DC converter I prefer fast PWM which basically saw tooth wavwform compare to PWM value for fastest frequency. But we also have phase correct PWM which is symatic triangle waveform that compare to PWM value. If we set both signal with same frequency are there any advantage or which mode is preform better in which situation?


texts:
I'm having some problems at my new girlfriend's house.
There was a extension cord that was giving shock and I changed to another. This one wasn't giving shock, but when I test it with that screwdriver that lights up a light on electricity, it lights up when touching the plastic part of the wire. The outside I mean.
And it is happening with all the extension cords of the house.

What I want to know is if it is normal to the outside part of the wire to conduct correct or if maybe there is a problem with the house electrical system.

English is not my primary language, sorry for any mistakes.

Edit: on the others extensions  of the house the light is on although it is very dim


texts: Will a faster rate of change of flux improve electricity generation?

texts:
From what I remember about electricity generation, a varying magnetic field is used, either the magnetic field  or the coil moves to generate electricity.

e = dB/dT

where

e = voltage induced

B = magnetic field

T = Time

Would more voltage be induced if both, the magnets and the coil, are mounted and geared to rotate at different velocity?


texts: Where does the system load go on a bq51051b charge controller?

texts:
I'm trying to use an integrated chip for Qi Charging + lipo management + overcharge protection and all the hard stuff basically.

The only one that is 'integrated enough' seems to be:
http://www.ti.com/lit/ds/symlink/bq51051b.pdf

In the 'Typical Application' circuit there is no system load, and i can't figure out where it's supposed to go from the rest of the spec either.

Am i supposed to connect the load in parallel to the battery? How is that going to protect the battery in any way?


texts: Deducing the equation of the circuit which is composed of batteries in parallel and the external resistor

texts:
We assume that the \$n\$ batteries have been connected in parallel, and the external resistor connecting the endpoints(terminals) of the parallel part.
\$n:=\$ number of the batteries.
\$r_i:=\$ith internal resistance of the ith battery.
\$E_i:=\$ith EMF of the ith battery.
\$I_i:=\$ith current which flows between the endpoints of the ith battery.
\$I:=\sum_{i}{I_i}\$ ;(The current which flows through the external resistor).
\$R:=\$external resitance.
My textbooks says that below equation is true.
\$R*I=r_i*I_i+E_i\$
I thought that the above equation is wrong and my below equation is true as applying Kirchhoff's law(potential drops).
\$R*I+r_i*I_i=E_i\$
Can anyone tell me what I have been missing or mistaking so that I can resolve the problem on my own.


texts: Does anyone know if I can use a Quam TBL 25 volt 4 watt audio transformer to step down 120 volts to 12 volts, later to be rectified to a 12 volt dc power supply? I know 12 volt power supplys are normally cheap and easy to come by, but in my current situation I have very few components to work with hence the unconventional application. Any tips or cautions would be greatly appreciated.


texts: How are such low op-amp input currents possible?

texts:
I understand that op-amps have low input currents; that's one of their defining characteristics. But looking at the datasheet for the LMC6001 (amusingly called an "Ultra, Ultra-Low Input Current Amplifier" because one ultra just wasn't enough), I have to wonder: how the <censored> do they get such low input currents‽

The LMC6001 claims a maximum input bias current at 25°C of 25 femtoamperes. With its rated input offset voltage of 10mV between the pins, that's equivalent to a 400 GΩ resistor between the inputs, which are two adjacent pins on an SOIC package. And the equivalent input-to-power resistances are even higher!

And then if you look at comparators, it's even more impressive. Take for example the TLV7211, where the equivalent input-to-input and input-to-power resistances are on the order of 100 TΩ, while being in an even smaller SC-70 package. How is this not dominated by leakage currents through the PCB and packaging?


texts:
I'm trying to do a simulation on Microcap 12 using vendor provided models.
The devices I'm trying to use in my schematic are the following:
2SA1312
2SC3324
I add the models via component editor as per this guide suggests.
After drawing my circuit, I try starting a transient simulation and this warning appears:

Warnings
Warning unknown parameter TNOM in model 2SA1312_BJT.
Warning unknown parameter TNOM in model 2SC3324_BJT.

These warning are easily fixed by opening the model and removing (or commenting) the line related to TNOM.
After doing this, transient simulation actually goes through, but a quick check on the voltage nodes shows that these transistors are simply open circuits, since the voltages shown at their terminals are simply the power rails values.
Here's a simple example with a built-in model (2n2222):

And here's the same circuit but different transistor (for which I imported the model):

Notice that the voltage on the emitter is the negative rail.
Any advice on how to try to fix this problem?


texts:
I'm new to VHDL and I'm trying to simulate an array multiplier.(I have used verilog before). However in the simulation results it shows 'X' for inputs which used to be '1'.Here is the result:
And this is the Testbench:

LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;

ENTITY array_multiplier_tester2 IS
END ENTITY;

ARCHITECTURE timed OF array_multiplier_tester2 IS
  SIGNAL A,B:std_logic_vector(3 DOWNTO 0):="0000";
  SIGNAL product:std_logic_vector(7 DOWNTO 0):="00000000";
BEGIN
 UUT:ENTITY WORK.array_multiplier(main)
    PORT MAP(A,B,product);
 A<="0000"; B<="0000";
PROCESS BEGIN
  WAIT FOR 23 NS;A(0)<='1';B(0)<=NOT B(0);
  WAIT FOR 23 NS;A(3)<='1';B(3)<='1';
  WAIT FOR 23 NS;A(2)<='1';B(2)<='1';A(0)<='0';B(0)<='0';
  WAIT FOR 23 NS;A(1)<='1';B(3)<='0';A(0)<='1';B(0)<='1';
  WAIT FOR 23 NS;A(3)<='0';B(2)<='0';
  WAIT;
END PROCESS;
END ARCHITECTURE timed;

I've also tried to use A<="0001" instead of A(0)<='1', but the result was the same. I'm using Modelsim for simulation.

  I don't know why it shows 'X' for input!


texts: How many periods of a periodic signal are required to properly determine magnitude?

texts:
I have a pure sinusoidal test function. I am trying to determine the magnitude of the response through my circuit very soon after powering up with circuit. If  I am using a 1kHz test signal, I only get 1 period after 1ms. I am using an oscilloscope with a very high sampling rate (>1 GHz). It seems to me that by using an FFT, I should be able to get valid magnitude data after at least 1 ms. I know that averaging over more periods will reduce the noise, but I already have a sufficiently high enough SNR to not need to worry too much about noise.

Am I mistaken that I can get the true magnitude of my response using only 1 period?


texts: Why plug is polarized in the US? What are the benefits?

texts:
I could not get a good hold of it, I searched online quite a bit. This must have to do with safety but then non-polarized switches are used through out the world with no issues are risks, so my question why use polarized socket where one blade (neutral) is longer than the other (hot).

The best explanation I came across is, it has to do to with the lamps used in United States where you have to reach out to turn the lamp one and off and may accidentally touch the bulb part which in case of non-polarized socket could either be hot or neutral and can give a shock, but is that the only reason? Somebody could do the wrong wiring and that means you will still get a shock with polarized socket?

I could find other reasons like capacitor between ground and hot wires or making the chases connected to ground etc but I don't think they are the main reasons because again non-polarized switches are used through the world for appliances. So my question is why use polarized switch in the US? If electric lamp is the main reason, why not re-design the lamp and make it safer?


texts: Multiple motor speed control with a single triac

texts:
I have a requirement where I have to control the speed of 10 motors. The motors are 230V AC single phase motors. The speed of the motors need to be increased or decreased using a electronic controller (no varistor). All the motors need to run at the same speed. I am considering phase angle voltage control to control the speed of the motors.

Each motor consumes maximum 2A current.

I have identified BTA24 Triac which supports 25A load current. This is a snubber less triac.

My question is whether I will be able to control all the 10 motors using a single triac. i.e phase angle control using 1 triac and feed the output to multiple motors.

Whether this setup is possible or is there any drawback in using a single triac (any thing to do with induction current etc) or do I need to have a triac for each motor separately

Just to clarify on speed:

I am not worried about synchronised speed on all motors. All my concern is if I supply a chopped voltage to a set of motors connected to a single triac, will the presence of multiple motors on the same triac affect the output voltage or current at the triac output.

For ex:

Each of my motor is rated at 350W.

If I supply 240V via the triac I expect all of them to run at X rpm.

If I am firing the triac at 90 degree,I expect to supply 120V to all the motors assuming a 240V mains line. Can I expect all the motors to run at X/2 rpm (+/- few rpms is acceptable)


texts:
I am trying to flash Wemos D1 mini (ESP8266) using NodeMCU according to this video. Pins NodeMCU → Wemos:

RX → RX
TX → TX
D3 → D3
RST → RST
3.3V → 3.3V
GND → GND
EN → GND

When flashing Wemos LED is blinking (probably as a response for reset), but flash process does not start. VS Code writes to log the following:
Uploading .pioenvs\esp8266\firmware.bin
esptool.py v2.6
Serial port COM11
Connecting........_____....._____....._____....._____....._____....._____....._____
A fatal error occurred: Failed to connect to ESP8266: Timed out waiting for packet header
*** [upload] Error 2

P.S.:

I flash Wemos because there is a problem with flashing it using build-in USB (one transistor was not soldered by error). Hence I use NodeMCU as USB-TTL converter.
There is no problem in USB cable. I used it successfully to flash another Wemos board (which has no defects) using VS Code (same procedure/method).
I tried to power Wemos with a separate power, but that does not help.
Similar question: ESP-01 module unable to flash or communicate – suggests wire 3.3V → RST (Wemos).

What can I try additionally?


texts:
In the United States and Canada there are 11 channels available for use in the 802.11b 2.4GHz WiFi Frequency range defined by the IEEE.

But there are only 3 non-overlapping channels available in the 802.11b standard.These are Channels 1,6, and 11. Why is it that we couldn't define a large band width so that all channels will  have no overlapping?

If it were done, would we have better performance when using Wifi today?


texts: Input Protection for a Solar powered Microcontroller project

texts:
We have a PV-powered remote sensing project that has not been as reliable as we had hoped. Servicing the device is a hassle, and most of the problems have been around the power supply.
The present system has a PV panel, charge controller and 12V lead-acid battery, that powers a Particle Electron board and associated sensors. The Electron board has a small LiPo cell and charge controller already built in that has been more reliable than the lead-acid cell.
We are going to remove the lead-acid battery, and substitute a larger capacity LiPo instead.
Our requirements are;

Useable with a variety of PV panels, both 6 and 12V, of varying models. Tolerant of open circuit voltage of at least 24V.
Reverse polarity protection.
Low maintenance.
Tolerant of voltage transients - lightning storms are common in the area.
High efficiency - some of our sensors are power-hungry.

We have settled on using the Adafruit PM3610 Buck module, and this is what we propose for protecting it and the downstream microcontroller. The module runs on 5.5 to 21V, and has an inrush input current limit of 3A.

simulate this circuit – Schematic created using CircuitLab
Our question is;
Is this reasonable, are there any improvements that we could and should make to this circuit?
Thanks
Edit: Updated circuit diagram, thanks for the suggestions.


texts: Strange frequency of audio output voltage

texts: For a school science experiment, we have stripped an audio cable and hooked the right channel and ground wires up to a voltage graphing device. The audio cable is plugged into the audio output of our computer. The computer is playing a constant sine wave tone at 880Hz, and so we'd expect the voltage graph to have a period of 1/880 seconds. However, the voltage graph is instead showing a very slow sine wave with a period of 12 seconds. When doubling the frequency of the sound we were playing, the period halved to 6 seconds. Why would the computer be outputting a different frequency voltage than we were playing?


texts:
I have some brushed motors near to a 433 MHz RF receiver. They're controlled by a 490 Hz PWM signal. The electrical noise they produce is not a problem for the circuit, but it is for the receiver.

How can I reduce the noise, at least on the frequencies interfering with the transmitter?

I read that putting a ceramic capacitor across the motor's terminals and one from each terminal to the motor's case would help; if it's true, what size should they be? I unfortunately don't have technical information about the motors. I'm quite sure they're the same as those, but there isn't much data on that site...


texts: Over voltage protection without shorting the Output to GND during Over voltage

texts:
Here is the circuit diagram i am referring.

Vin_12v_ext - Max 12V;

Batt_V = max 5.4V;

Vin_ext_12v_gen is either Vin_12v_ext or batt_v;

5v_reg - is either generated by an on board regulator or switched from batt_v via M7 & D4.;

This circuitry is used to switch board power from Primary(Vin_12v_ext) to battery(batt_v).

M1 is the primary leg which switches power from Primary power source.

M2 & M3 are secondary leg which switches power from Secondary power source.

Whole board is powered by Vin_ext_12v_gen rail(which can be Vin_12V_ext or batt_v).

Few other regulators are powered by 5V_REG net on the right top.

Issue faced was, When Vin_12V_ext is OFF, we are seeing batt_v on Vin_ext_12v_gen net as expected. But when Vin_12v_ext power came back, Vin_12v_ext flows to 5VREG net via M1,M2 and D4 which is damaging regulators(whose max input voltage is 5.5V) on 5VREG net.

I can't change any architecture of this,

So, i am trying to add high speed PTC+Zenar diode protection at the Output of 5VREG net to Protect the regulators on the downside of 5VREG net.

But i saw PTC+Zenar approach to protect against Over voltages is used normally at the entrance of the power to the whole board. I have not seen PTC+Zenar approach inside of the boards power architecture.

Whether we can use PTC+Zenar/Schottky diode approach to limit Voltage on 5VREG net to 5V?


texts:
I recently bought a ZS-042 RTC module which communicates using the I2C protocol. The module includes a DS3231 (RTC) and an AT24C32 (4k EEPROM).

The ZS-042 module has no datasheet, but the Ebay listing (linked above) shows how the DS3231 and AT24C32 are assembled on to the module (ZS-042 is NOT an IC).

When I bought it, I had no idea what the I2C addresses where for the device, so I ran a quick scan and addresses 0x57, 0x5F and 0x68 acknowledged.

I am a little bit confused because the module only includes two I2C devices, but I am getting the ACK from three. I researched and the I2C addresses 0x57 and 0x68 correspond to the DS3131 and AT24C32 respectively, but I couldn't find a single device with the 0x5F address.

I tried running the scan with the module disconnected, and all three addresses disappeared.  When reconnected, all three addresses reappeared. To make matters worse, when I send a byte to the ghost device, the device ACKs!

I can physically see only two ICs soldered to the ZS-042.

Any ideas which device is responding to I2C address 0x5F?

P.S.
I am using an Arduino UNO with a custom library in order to run the I2C lines under 3.3V (not the standard 5V) from any pair of digital pins. I wrote the library myself using the I2C protocol guidelines and I have thoroughly tested it on EEPROM. This is a link to the library files:

https://github.com/JuaFMaldonado/I2C-Trough-Digital

I am using this simple sketch to scan for devices:

#include <I2CDigital.h>

#define WRITE 0b00000000
#define READ 0b00000001

I2CDigital I2C(12,11);

void setup(){
  Serial.begin(9600);
}

void loop() {
  for(int i=16;i<120;i++){
    if(I2C.startCom((byte)i,WRITE)){
      Serial.print("Device detected at address: ");
      Serial.println(i);
      if(I2C.sendByte(0b00000000)){
        Serial.println("Byte sent successfully");
      }
      I2C.stopCom();
      delayMicroseconds(5);
    }
  }
  delay(5000);
}

Thanks in advance!

EDIT suggested by @ChrisStratton:

To be able to use any pair of digital pins for I2C communication, the pins are only allowed to run in pinMode(pin,INPUT) (for logic high) or pinMode(pin,OUTPUT) and digitalWrite(pin,LOW) (for logic low). The lines can then be connected to any desired pull up voltage (as long as it is still recognised by the device as logic high).

In my particular case they are connected to the 3.3V regulator on the Arduino through 4.7k resistors.

EDIT suggested by @ElliotAlderson:

simulate this circuit – Schematic created using CircuitLab

EDIT sugested by @Janka

DS3131

AT24C32


texts: what are the best practices for bolting a ring terminal to a steel panel?

texts:
i have made several new bolted grounding points in project boxes and in my car. i don't have data on how long they last, but i been following a strategy like this to connect a ring terminal:

drill a hole in the steel
grind or sand off any paint or detritus around the hole (ideally both sides, but sometimes only one side is accessible)
deburr the metal with steel wool or a file
line up the terminal with the hole and secure them loosely with a bolt and nut,or two nuts in areas of high concern
spray those parts with De-Ox-It
tighten the nut(s)

This mostly works, but should I use washers? How many and what kind? Is another conductive solution better suited than De-Ox-It? What should I know about the amount of torque applied? Does it matter if the bolt tarnishes over time?


texts:
I need to provide a reasonable amount of power (40-50W) for a heat pillow, how should I design the power supply circuit if the load (Enamel Insulated Resistance Heating Wire) is 2,5 ohm.

I can't wrap my head around how to feed such a load without getting short circuits on one hand and voltage divider taking all the power on the other hand.

Thanks in advance!


texts: AND, OR gates: 3 transistors. NAND, NOR gates: 2 transistors. Why?

texts: Why do NAND and NOR gates require two transistors each, whereas AND and OR gates require three each?


texts: Why do some motors have both 50Hz and 60Hz on their nameplate, and some do not?

texts:
I have seen some induction motors have information on their nameplate listed for 50hz and 60hz. While I've read a requirement that the Voltage/Frequency ratio be consistent, using these nameplate numbers you can come up with examples like 380V/50Hz = 7.6, and 440V/60Hz = 7.33. These are not the same. Are they close enough that it doesn't matter? Does this mean all induction motors can be run in either frequency? All 3 phase induction motors can be run at either frequency? Only motors designed used in at both frequencies?
Edit:
I see the nameplates. I'd just like to have an idea of why - I'll take any direction you can point me in. Did marketing de-rate these motors so they can run slow enough or cool enough at either frequency? Did accounting let them use better materials? Do I need to take a graduate level FEM course in order to understand, and I'm asking the equivalent of how to measure the current across and the voltage through?


texts: I wanted to know if there is a method/circuit to half the frequency of a triangle wave, in the same way a flip flop can be used to half the frequency of a square wave. Any help would be appreciated thanks.


texts: While under DC current capacitors cause open circuit as time goes to infinity but under AC current they flow through capacitor. As I know Maxwell described this behavior as "Aether current". Is this current under AC source actually caused by microwaves or how is it possible for current to pass through it and how AC current can pass while DC can't?


texts: How can I get 225mA of current from a 5Vpp sine wave at 150Hz using BJT's? I've been playing around with common emitter's and emitter followers but havent been able to get a high current output.


texts: Compensate Temperature with pressure sensor?

texts: I'm using this pressure sensor and when I submerse the pipe inside the liquid the pressure should be held constant ,but due to the temperature the sensor keeps giving different values after certain time.How can I compensate for this ,Mathematically and programmatically  ?


texts: How to ground PCB to chassis using mounting hole with vias in Kicad?

texts:
Hi I have 4 layer board layered as follows.

Signal
Power
Ground
Signal

For the power and ground planes I have done zone fills...
I want to attach the PCB ground to my chassis using a screw. I initially just had a padded mounting hole, but someone suggested to fortify the hole with vias incase the screw somehow damages the plating and the connection no longer happens, but he's not sure how it works in KiCad.
I noticed there's a mounting_hole_pad_via footprint/component. And I used that. Is that enough, or do I need to do anything else special? The mounting hole is already attached to the ground fill. The surrounding holes are through-hole and marked as all copper layers.
I attached a picture...
Pink is the ground pour, yellow is the power pour.


texts: Bluetooth power saving mode for ArduinoBT

texts:
I'm trying to get my ArduinoBT to be a bit more power friendly, I have it running in a sensor network and it is constantly drawing power.  I want to be able to turn off or put the Bluetooth module to sleep for durations when it isn't in use.
I've tried

Serial.println("SET CONTROL CONFIG 103d");

In my setup method which should put the module into deep sleep mode but it doesn't seem to do anything in terms of power consumption (still draws about 30mA).
Am I not waiting long enough for it to kick in?  Does the WT11 iWRAP version not support deep sleep? Am I putting it in the wrong spot in my code?  Am I doing something else incredibly ditzy that is stopping it from working??


texts:
There's some basic flaw in my understanding of how LED's or diodes in general work so hope someone can help and forgive the simple question.

So generally when one has an LED in series with a resistor, it seems the LED will always have voltage drop corresponding of around 2V (more exact value can be read from datasheet). This means the voltage drop across the resistor will be the voltage drop of the source minus the 2V, and the resistor should be chosen simply to limit the current to, say, max 20 mA or whatever the datasheet says. But the relevant point here is that the size of the resistor won't impact the distribution of the voltage drops (over the resistor vs the LED). The LED has a "hard-wired" voltage drop and the resistor takes the rest.

So what if we have a different scenario, where a Zener diode is used to convert the voltage. So in this case, I have a Zener and a resistor in series, connected to the power supply. Let's say the Zener diode is 5V. It's connected "reverse" to take advantage of this reverse breakdown voltage.  The resistor is such that the max current drawn can be 20 mA for the whole circuit. The circuit is seen here:

The Voltage drop across the Zener should now be 5V (assuming the voltage source has a higher voltage than that) and the resistor limits the current.

Now the question is: What happens if I connect an LED in parallel with the Zener, without any resistor? A resistor shouldn't be necessary for current-limiting purposes since the resistor (in series with the Zener) is already limiting the current so we know there's never be an excess current. But since the LED is in parallel with the Zener, the voltage drop across it will be 5V, i.e. higher than before. So this is different from the case before where the circuit ensured the voltage drop across the LED was 2V. Here it seems it cannot do that, because there is only the LED to take the whole voltage drop.

Will this setup damage the LED? What value should I look for in the datasheet to find out what max voltage drop I can apply when there's no resistor? In the sheet I have for a typical LED, such a voltage is not listed under absolute max ratings. But I suppose I couldn't just put a drop across 1000V even if I assured the current was < 20 mA?

I'm also thinking if the wires will start acting as (small)resistors in series with the LED and somehow take the excess voltage.


texts: For my RF circuit (868MHz), I need 50-ohm impedance. When I calculate the impedance as PCB manufacturer layer stack-up,  the impedance would be 66 ohms. How does this affect my RF circuit performance? What are the limits of impedance matching?


texts:
I need a circuit which will automatically disconnect the battery from LOAD when ext. DC power is connected so that the battery won't get damaged.

Theoretically a pair of diodes can solve this but since voltage drop is not a good thing for a portable device, so after reading few topics about an "ideal" diode (first and second) I came up with simply rotating MOSFETs (connecting SOURCE to actual drain and DRAIN to actual source) so body-diode will block unwanted reverse current flow:

Q1 Is preventing battery from discharging to DC IN when e.g. 5V source is connected and isolating DC IN positive wire from battery, so we can detect a ext. power supply is connected.

Q2 Is preventing DC IN 9-24V from going to battery and damaging it.

But probably a small amount of current will flow thru Q1's body-diode to battery at first moments after ext. power is connected (or contact bouncing) before Q2's gate has triggered, but I'm not sure if it's something to worry about.

Anyway I have a strong feeling I'm reinventing the wheel here, so I need  other standard solutions/ideas please. Requirements are:

Automatic and fast switching. Actually a 2-position toggle switch
can be a good solution here but it will require manually selecting
the source:

Loads up to 6A, voltage range: 4-30V
Small, but as simple and cheap as possible (so two relays/SSRs @6A is too big and expensive)
No diodes at load current flow please, since 0.4V@6A is 2.4W of heat and ~5-6% loss in efficiency (which is bad for a battery-powered device).

Or, if first circuit seems to work just fine and there's no significant errors I made, maybe I can use it?
Thanks for help!

Oh, it seems like I found a problem – Q1 won't open after external power supply is disconnected, because current from Q2's body-diode can flow thru Q1's SOURCE-DRAIN to Q3 BASE, keeping Q2 from closing and Q1 from opening.
Adding a diode can fix this. Yes, it will drop some voltage, but since it's true just for external power source, we won't lose any portable efficiency :)


texts:
I am trying to get a live connection on my mcu using a simcom (7600) modem. In order to get grip on what I am doing, I feel the need to get some general understanding of ppp first.
I read through the first parts of RFC1661 which details about LCP (link control protocol). I read about LCP here as well:

Am I understanding things correct when I state the following:

The modem enters PPP mode after sending the AT command ATD*99#
After entering PPP mode, the client (in my case, my microcontroller) must send some LCP packets that negotiate an IP Address and DNS (default gateway) with my ISP.
Once all that is done, and only then, I can start opening TCP connections to the internet

Or, is the LCP negotiation part of enabling PPP mode via ATD*99# command?


texts:
While learning 3-Phase scalar control of ACIM using STM32F407 MCU I could not clearly understand the diffrence between the following terms:
1. SPWM
2. 6-step PWM
3. SVMPWM

How do they differ from each other?
Do we get the same 3-phase sinusoidals from each of the above PWMs and they are 3 different ways to implement it OR Do they differ in the output that we get from them also?
Someone told me that SPWM is used to generate Phase-voltages while the other 2 techniques are used to generate Line-voltages. Is this the only difference between them?


texts:
I've made this circuit on a breadboard. It doesn't work properly.

I hear the sound of an oscillator (similar to the sound of 555 timer).

I changed C6 and L1 to change the frequency but I hear the same sound.

When I use 3K ohm instead of R2, the frequency increases (the tune of the sound is higher).

The transistor in the circuit is not available for me. so I used other transistors (general purpose, switching transistors and amplifier transistors).

I'm using 5 volt instead of 3 volt.

I want to know what is the problem? and should I use a zener diode or an ordinary diode?


texts: Difference between more batteries and boosting voltage

texts:
For example if i need 18V for a project, what is the difference if i use 2 9V batteries and 1 9V battery boosting it to 18V?

Thanks in advance.


texts: Is this Non-Inverting integrator correct?

texts:
I've seen time again the formula for an inverting integrator. I was wondering if I could swap the configurations on the inverting and non inverting inputs of the op amp to make the circuit a non-inverting integrator. I did the math, but when I searched online to make sure my math was correct, I found nothing supporting my derivation. So I'm wondering if my math is incorrect or if I have a conceptual gap with the functionality of an op amp. Here's my work:

I called the non-inverting input to the op amp \$v_{+}\$ the inverting input \$v_{-}\$, the amplification \$A\$, the output voltage \$v_{out}\$, and the input voltage \$v_{in}\$.
$$ v_{out} = A\times(v_+ - v_-) $$
Because I grounded \$v_-\$, $$v_{out} = Av_+$$ $$v_+ = \frac{v_{out}}{A}$$
The current going through resistor \$I_R\$ is the same current going through the capacitor, \$I_C\$. Where \$I_R=\frac{v_{in}-v_+}{R}\$, and \$I_C = \frac{dv}{dt}C\$. Therefore, by equating these equations we can solve: $$I_R = I_C$$ $$\frac{v_{in}-v_+}{R}=\frac{dv}{dt}C$$
$$\frac{1}{RC}(v_{in}-v_+)=\frac{dv}{dt}$$ $$\frac{1}{RC}(v_{in}-\frac{v_{out}}{A})=\frac{dv}{dt}$$ $$\lim_{A\rightarrow\infty}\frac{1}{RC}(v_{in}-\frac{v_{out}}{A}) = \frac{1}{RC}v_{in}=\frac{dv}{dt}$$ $$\frac{1}{RC}v_{in}dt=dv$$ $$\frac{1}{RC}\int v_{in}dt=v(t)-v(0)$$ $$\therefore v(t)=\frac{1}{RC}\int v_{in}dt + v(0)$$ The inverting integrator follows the same formula, except it has a negative tacked on infront of the integral: $$v(t)=-\frac{1}{RC}\int v_{in}dt + v(0)$$


texts: Can the frequency of an electrical current be heard and distinguished from other frequencies just by connecting circuit to a speaker?

texts: I have a circuit that I want to be able to detect the frequency of the current going on it (part of the circuit is AC, the power supply is going to be at least 3v, probably 5v, and 6v DC at most).  I don't need to know the exact numerical value of the frequency, just be able to tell when it changes to a different frequency.  I have a very basic knowledge of electricity, so this may be a very overly simplistic interpretation of how it works, but could I connect the circuit directly to a small speaker, with a constant sound frequency indicating no change in current frequency (I imagine a constant hum), but with a change in the sound frequency (the hum becoming higher or lower pitched) indicating a change in the electric frequency?


texts: What does the RNF pin do on an H-bridge?

texts:
The H-bridge in question is a BD6212FP. Pins 7 and 8 are marked "RNF". Below is a link to the datasheet.

http://www.farnell.com/datasheets/46169.pdf


texts: How to power 12V fan and 3V LED with a 9V battery?

texts: I am trying to power a 12V fan and a 3V LED with a 9V battery, but I do not know where to begin. I want the light to automatically be lit up when the 9V battery is connected to clip but the fan will only run when a switch is activated. I have a 330 ohm resistor for the light, but that will cut down the the power for the fan and I was wondering how could I accomplish such a task?


texts: RMS value calculation of 3 phase line voltages for power calculations

texts:
In my textbook in the power calculations section of the balanced three phase circuits, a part confused me a little bit, it is this part:

Why are we dividing by \$\sqrt{3}\$ to find RMS values of \$V_{\phi}\$ and \$I_{\phi}\$? As far as I know, we are dealing with sinusoidal sources and in sinusoidal sources, RMS transformation was done by diving to \$\sqrt{2}\$. In the same textbook in the previous chapter, power calculation for sinusoidal sources were shown like this;

I didn't understand where this \$\sqrt{3}\$ come from in the 3-phase power calculation.


texts: Stepping down DC - maximum current capability

texts:
I'm looking for a bit of a sanity check here (I'm a hobbyist) --
I want to use a 12v regulator capable of outputting 600mA
It's required that it be able to provide enough current to power a 12V to 5V regulator outputting 1000mA.
12 / 5 = 2.4, so theoretically the 600mA @ 12V should be able to provide 1440mA @ 5V, right?


texts:
I am installing a home UPS system of 1400 VA. The UPS is a 24 volt system and, based on the batteries available on the market for the UPS segment here, will need 2 x 12 volt batteries for it.

Based on what the UPS service engineer told me, and my own research on the internet, I had nearly settled on getting a 150 AH battery.

When I was talking with a battery dealer, I mentioned that my UPS was 'solar compatible', and I also planned to connect a 500 watt solar power system (PV panel + charge controller) to my home UPS in another 6+ month. He then said that I should purchase a C10 battery, as these batteries were recommended for solar power uses.

Since I didn't know what C10 or C20 ratings meant, I looked it up. Basically, all sources said that battery capacity in AH weren't meaningful as they change based on the load (current drawn). Thus, the C rating - C5, C10, C20 OR C100 - rating help with this by defining some standard hours, making it easier to compare the capacity of the battery in the market.

This is where I am getting confused, and need some clarification.

A 150 AH battery at C20, will last for 20 hours on a load of 7.5 A.
A 150 AH battery at C10 will last for 10 hours on a load of 15 A.
A 150 AH battery at C5 will last for 5 hours at a load of 30 A.

In terms of backup time, which battery - C5, C10 or C20 - is better and will last longer?
Why is a C10 or C5 battery considered more suitable for solar power use, than a C20?

(Be kind if my flaw / idiocy in reasoning is very obvious to you!).


texts: How to deal with "peaks" voltages in mosfet in boost converter?

texts:
I'm designing a Boost Converter to go from 5 [V] to 12 [V]. The design I came with is the following:

To understand better the design, please note the following:

1) To drive the mosfet I'm using a PIC4550 with an opto coupler (TLP250, http://web.itu.edu.tr/yildiri1/mylibrary/data/tlp250.pdf) so I get a PWM of 15 [Vmax] at a frequency of 40 [kHz]

2) I didn't find the model I'm using in the real converter in PSpice, so I put a rectifier diode there but the one I'm using is SBL2030CT (http://pribor-systems.ru/fromoremax/PDF/Diodes/SBL2030CT-SBL2060CT.pdf) which is a Schottky diode.
3) All the other values and components are correct with respect to the real converter

The problem is: I can't get 12 [V] in the load because when I'm raising the duty cycle, the current goes crazy. At approximately 53% duty cycle, the circuit is asking the power source about 3 [A]. Since it can't give more than that, I can't raise the duty cycle anymore so I can't get 12 [V]. The max output voltage I get is 10 [V]. One of the problems I've found measuring and seeing the waves in the oscilloscope is that the square wave in the mosfet has peaks like this (This picture IS NOT from my actual circuit, but the waveform is EXACTLY the same as the one I'm getting. I took this picture from another related post, please see EDIT 2):

The peaks at the maximum current that the power source is able to give me are of about 30 [V] (while the output voltage is 10 [V]). When I touch the components, the mosfet is really hot (in comparison to the load) so I think it has to do with the peaks. Is there any idea about how I can deal with this problem?

If there is any missing information please tell me so I can add it.

EDIT1: The circuit for the moment is mounted on a breadboard (I tried there first because I want it work property then I have to move it to a PCB). The input doesn't have any capacitor across it. It is just as it is in the diagram above.

EDIT2: The waveform I get in the MOSFET is exactly the same shown here: Hot MOSFET DC-DC Boost Converter . However, the answer there doesn't seem to answer mine because I'm using an enough voltage to turn the mosfet on.

EDIT3: This is the diagram for the optocoupler and the R and C used:

where R is calculated as $$
R = \frac{V_{CC} - V_{OL} - V_{EE}}{I_{OLpeak}}
$$
I came up with a value of R = 24 Ohm and yes, I'm using exactly that value of capacitor shown in the schematic for the bypass.

EDIT 4: Added images of the circuit and real images from oscilloscope from the actual circuit:

Also I tried: changed the frequency of switching to 150kHz, added (not shown in picture) a dissipator for the mosfet and changed the amplitude of the PWM to 20 [V] (it was of 12 [V] before. Did that because one of the answers suggested it). None of them worked and last measurement showed an efficiency of 47%.


texts:
We had our Digital Systems class today, and our professor kept throwing around the word 'canonical' around a whole lot, but I'm very confused as to what this is.
What I understood is that it's the way of representing an expression uniquely (i.e., two non-equivalent functions cannot have the same canonical form) Is my interpretation correct.
So would Sum of Minterms be canonical or not? If we simplify the SoM form, would it still be canonical?


texts: Calculation of the input resistance of an op amp circuit

texts:
After I calculated that $$v_s=v_u\left(\frac{R_1}{R_1+R_2}\right)$$ I have to calculate the resistance seen by the voltage generator \$v_s\$.

My book, without any calculation, says it is: \$+\infty\$. Now, I am trying to figure out why.

I thought that the resistance seen by \$v_s\$ is $$\frac{v_s}{\frac{e_1-v_s}{R_s}}$$ (with the nodal analysis).

I tried to do algebraic calculations, but the results doesn't come out as \$+\infty\$. How should I calculate it?

simulate this circuit – Schematic created using CircuitLab

EDIT: If ideal op. amplifiers have infinite input resistance, so should be in the following circuit:

simulate this circuit

My book says in this last circuit it's \$R_1\$ (without any calc. too). Why?


texts: I am trying to route connection on a board. However much I try there is always a via dropped below the IC. It is an SSOP package. IS this okay or is it an issue?


texts: Distribute 5V 16A over Multiple PCBs: One Cable

texts:
I want to power a set of WS2818B (datasheet) and White LEDs (datasheet).
18 RGB and 9 White LEDs will be mounted to seperat PCB Modules, for which I calculated 0.648A and 0.8A  per Panel. Though I am planning on running the white leds on half brightness with PWM and only when 2 of the 3 RGB channels are of, which should reduce the required current for when the white LEDs are in use. I would like to run a Powerwire for the WS2818B Leds and one the White Leds, so that I can use PWM. I could of course power form multiple points, but that wouldn't be suitable for my case.
How would I safely transfer the power required for at least 21 Modules, which is around 16A when accounted for 80% Power Supply use, without multiple connection points or 2cm wide PCB traces?


texts: Over Voltage Protection circuit without being affected from temperature

texts:
I need adding an OVP circuit for my converter circuit.
At the 100Vdc the Brown-Out pin of my PWM controller IC will be pulled down to the ground. I did this with the circuit shown below.
But, at 80°C, the transistor is conducting too early. At 80Vdc input voltage and 80&degC, the transistor is conducting.
How can I improve this overvoltage protection circuit without temperature effects?

Thanks


texts: Is \$V_A\$ or \$V_B\$ the inverting input here?

texts: Is \$V_A\$ or \$V_B\$ the inverting input and why?


texts: Can I use an electrolytic capacitor with a MCP1826S voltage regulator?

texts:
I have a MCP1826S and according to the datasheet, I should use an output capacitor of 1-10uF and with an ESR of lower than 1Ω. I have some 4.7uF electrolytic capacitors, but I think they have an ESR of +-5Ω. Is it a bad idea to use these caps? I just want to regulate a USB 5V source to 3.3V and I don't plan to use a lot of current, I only want to have a 3.3V supply for some arduino projects.
Here is a link to the datasheet.


texts:
Do we need any protection on the contact side of the relay (Ex: form C 240V 3A) if the contact side is not powered by the circuit.

if we have to protect, then how(Please provide an example).

Also, do we need to have any EMC/EMI protection such as saftey Cap, MOV, or etc?

simulate this circuit – Schematic created using CircuitLab


texts: I have (had, actually) an El Cheapo pocket LED flashlight powered by 3 AAA cells. It was shipped with very low quality "salt" cells (regular, low weight - someone please suggest a proper English name for them). I tried to beef-up this flashlight by installing powerful Varta alkaline cells but flashlight blinked couple of times and gone dead. Now I have slight memories about what I read somewhere what LED drivers does not allow alkaline (higher current) feeding. Are my memories correct? Can I actually install alkaline cells to LED lighting devices? (Yes, No or Sometimes depending on driver)


texts:
I am powering a few op-amps from a split supply made from a 7805 and 7905. Before connecting the amps, I measured the outputs from both regulators and got 5V and -5V, respectively. However, after I soldered down the amps, I observe -0.9V at the 7805 output pin (the 7905 functions properly). The 7805 is not getting hot, and I am not measuring any shorts between 5V and -5V, 5V and GND, or -5V and GND. I am measuring 7.5V at the input to the 7805, as expected. I tried replacing the part as well, but this behavior persisted. When I remove the 7805 and connect a benchtop supply in its place, the circuit functions as expected and my supply reads a current draw of about 100mA. I am not sure what else to check. How can I go about solving this?

The schematic is as follows, duplicated 5 times:

Edit: Yes, I know the pinout for the 7905 is wrong. I have rerouted the pins to the correct traces on the board itself, and the 7905 functions properly.


texts: Is it inefficient or bad style to build std_logic_vector out of std_logic inputs?

texts:
I'm learning VHDL, and there are a lot of exercises where they give you an entity and you have to write the architecture, where a lot of the inputs are separate:

entity m is port (
    A, B, C: in std_logic;
    Y: out std_logic);
end m;

Now I could try to come up with some combination of operations but I find it pretty easy to just make lookup tables:

architecture b of m is
  signal together : std_logic_vector(2 downto 0);
begin
  together <= A & B & C;
  -- now do: "with together select" and then write out all the possibilities
end architecture b;

Is this bad style? Does the creation of the "together" signal cost anything or is the compiler going to synthesize the same thing it would dealing with A, B, C separately? I'm basically only making the vector so I can match on all 3 values at once.


texts: Will PWM on 50% duty cycle cut the current in a DC motor in half

texts:
I have a DC motor that is controlled by a PWM output on an Ardiono and I want to know if I can safely assume that by setting the output to 50% duty cycle, the current in the motor will be 50 % as well
The output is connected to the base on an BC338 transistor through a 1K resistor that I use as a driver.


texts: Can I transfer Ultiboard files to other PCB layout software packages via DXF export/import?

texts:
I have an extensive library of PCB layouts in Ultiboard format. If, hypothetically, I wanted to switch to another software package, this would pose a problem, as the Ultiboard layout format appears to be proprietary and not documented. (Could be wrong about that.) Ultiboard supports export to:

Scalable Vector Graphics
Gerber
IPC-D-356A Netlist
3D IGES
DXF
NC Drill

I'm thinking DXF is the most likely format to be supported by other software packages. What other layout packages, if any, support DXF import?

Related questions:
Importing Drawings ( DXF ) in Altium
Gerber to DXF converter


texts:
I'm simulating a passband amplifier (some 80 - 200 MHz) stage with two transistors. I'm using LTSpice. When I simulate the transfer function I get a maximum gain at a given frequency, let's say 100 MHz. Then, as a way to measure stability I'm running a transient analysis with an input frequency sweeping from 5 to 500 MHz and I found two weird things:
- the maximum gain is at a different frequency from the transfer function analysis, the question is, which one is right and why do they differ?
- if I run the transient for a number of frequency sweep cycles, the max gain frequency changes (the sweep is, I think, slow enough to allow an almost static response)


texts:
I use a wrist strap with 1 MOhm resistance connected to a ground Plug Adapter with 1.5 MOhm, so total series resistance is 2.5 MOhm.
Is it OK for ESD protection or would it be better to connect the wrist strap directly to ground?

I know that this resistance is to protect the operator. However, is there an upper limit on the value of the resistor so that it doesn't affect ESD protection?

Thanks


texts: What/How many devices to put in one local ground net?

texts:
I feel that this is a stupid question but I have really no idea how to answer it.

Looking at this answer first part and of course the other answer it's pointing to, I understand that high frequency current loops should be kept on a local ground net.

But the first link I've put here suggest joining the ground of devices close to each other. While I understand that a ground net is a net and so should contain multiple devices, how to decide which devices belong to the same net ?

At first I though about distance, but then all the devices get connected together on a dense board. I also though about uniting devices that were close and had similar switching speeds, but on a synchronous system that thought doesn't work, so is there any rule of thumb about that ?


texts: Can spy bi wire launchpad be used to program 4 wire JTAG MSP430

texts: I have  MSP430F5529 USB LaunchPad and MSP430FG4250IRGZR-16-Bit Ultra-Low-Power MCU. So is there a way to program the mcu using the launchpad.


texts: I know EE.SE isn't about economics, but the fact that a typical MOSFET can cost as much as a microprocessor, raises the question of why?  Are they that difficult to make?


texts:
This transistor ignition circuit for a model petrol engine is built from a proprietary kit. I have made it up and it works.

Now I want to take a signal from it as an external interrupt to an Arduino Uno based tachometer. But I don't know how to connect it. Ideally I would like the signal timed when the hall sensor switches off, as this is when the plugs are fired. (It is a wasted-spark system on a 2-cyl 4-stroke engine, so both plugs fire every revolution.)

Initially I thought I might be able to take a signal off pins 4 & 5, parallel to the LED, but now I don't think that would work. How do I do this?

There is a connection at the cross (UK convention) and the bottom rail should be marked "ground".


texts: Length of transmission line for maximum power transmission

texts:
in this question i tried to find the solution like this but i could'nt get the success

What's mistake i am doing can anyone help?


texts: What should be the voltage rating of bootstrap capacitor?

texts:
BST_1P is the bootstrap capacitor connection pin for high-side gate driver of TAS6422.
In the datasheet it is suggested that, this capacitor should have minimum rated voltage of 16 V.
What is the factor deciding this rated voltage.
Consider the maximum supply voltage is 16 V.


texts: Drawing 2.0 A from 9 V battery for 5 seconds

texts: I'm building a launch controller for a model rocket, and I've worked out that I need to draw 2 A for no more than 5 seconds. Given most commercial 9 V batteries can give me ~500 mAh, would a 9 V alkaline smoke alarm battery give me what I need?


texts:
How should I route USB Connector shield on PCB? Should it be connected to GND plane right where USB is placed, or should  the shield be isolated from GND, or should it be connected to ground through ESD protection chip, high resistance resistor or fuse?

PS. Should I put the shield connections on schematic, or just route it on PCB?


texts: How to write the Kirchoff's voltage equations for this complex circuit?

texts:
I am trying to develop a way of finding out how a black box is wired internally, based on multimeter readings of its terminals. I have recently posted a thread about this (here), but I thought I would narrow the problem down to solving an example, in the hope of extracting a pattern applicable to my initial problem.

Consider the following example circuit:

simulate this circuit – Schematic created using CircuitLab

Now, imagine the following variants of this circuit:

Circuit A: a voltage V12 is applied between terminals 1 and 2, the other terminals are open.
Circuit B: a voltage V24 is applied between terminals 2 and 4, the other terminals are open.
Circuit C: a voltage V45 is applied between terminals 4 and 5, the other terminals are open.

Note that I need to study any combination of terminal pairs, but this is a subset which should be representative.

Let's solve each circuit using Kirchoff laws. There are N=5 nodes and b=10 branches, which means we need to write 4 current equations, and 6 voltage equations. The current equations are easy to write, I don't have issues with that.

However, I struggle with the voltage equations. I need some kind of method to write those equations, otherwise I end up writing random loop equations. As you can see, there is a pattern in how the resistances are laid out. I'm hoping that when a method is found on this circuit, I can extract an algorithm to generalise to any number of terminals/nodes.

How would you write the voltage equations for these circuits?

Implementing Ben Voigt's answer

I only used as many equations/test cases as I needed to build the square matrix, because I don't remember how to add more equations and do a pseudo inverse (I have looked around on the web a bit, still is unclear).


texts: Negative sign of collector current (Ic-Veb characteristic curve) of pnp BJT on LTspice

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In the exact same circuitry with a npn transistor i get the same curve but with positive sign. I didnt expect the Ic to turn out negative since on Sedra-Smiths book its also positive.
Shouldn't it be positive?


texts: Power Supply for two 50V/12.5A Solenoids

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I'm in the planning stages of building a custom pinball table and one of the sticking points is powering the flipper coils. They're 50V DC coils with a resistance of only 4 ohms during the stroke. That's 12.5 amps, and there are two of them so potentially up to 25 amps.

However, they are only high power for the length of the stroke, when an "end of stroke" switch uses the full coil resulting in 133 ohms resistance bringing it down to a much smaller 0.376 amps which is all it needs to hold the flippers up.

"Real" pinball machines use a massive transformer with a full bridge rectifier. They're unregulated (I believe), which is fine, and have several taps for other voltages I'm not concerned with generating (much easier ways). But I'm not having much luck finding something similar for the 48-50 volts that isn't several hundred bucks.

Trying to design something though I'm not sure what to aim for. The 12.5 amps (each) is for such a short duration it seems like overkill to design something that can handle that much power continuously. However, I don't know how a modern switching power supply would handle such an impulse. I feel like it would think there is a short circuit and shut down to protect itself.

I've heard of people using ATX power supplies from PC's, just daisy chaining 4 of them together to get the +12V rails up to 48V (which is close enough). These can be had for fairly cheap (~$15/ea) and have a lot of power (25+ amps).

How would these handle an impulse load like that? Can they be connected serially without other issues? Is there a simpler solution?