texts: Components necessary to automate hand crank

texts:
I'd like to automate a simple crank on a rotating hex bolt thingy so I don't have to manually turn the lever/knob.

I was planning on

bluetooth module -> Arduino (or some easily programmable MC) -> motor -> hex bit

as the component diagram.

I can learn the Arduino programming, etc I'm sure, but I wanted your help with the motor:

I think the torque required is a pretty important factor - the manual rotating handle has a ~3in length arm, and requires a hefty deal of force (scientific, I know, but I'm not sure how to measure this short of a force meter) to turn clockwise, but much less while rotating counter-clockwise.
I'd like to be able to have the motor sustain this at 5+ revs/sec (the more the better).
The whole setup should be as quiet as possible as it will run in an office environment

Thanks for your help!

P.S. Any improvements to / ideas for the entire scenario (raise lower my adjustable height desk without rotating the hand crank) are certainly welcome - this isn't mission critical!


texts: Multiple(five) alarm time setting in stm32f0 mcu

texts:
I am working on my hobbyist project and need to develop the alarm timings.
And RTC and Timer are new for me and I am confused in RTC Alarm time setting.
I need to make alarm with RTC for five different times(as we are doing in the mobile).
So, I am looking for the same thing with my mcu.
Looking forward for the kind support ...
(I am using STM32 Nucleo Board, KEIL-IDE, CubeMX)

Thanks


texts:
I have a 12V DC power supply which would be connected with a solenoid and a manual button as shown in circuit diagram image below.
The rating of solenoid is from 9V-12.5V. It takes 500mA at 12V.
My requirement is to put an LED so that it lights up when the manual switch is turned on. I've basic understanding but that's it. Can I linearly put the LED light without causing any problems? Where should the LED be placed in the circuit if at all? Can off the shelf LED be used or some specific LED be used?


texts: how do i program in c daisy-chained spi flash

texts:
where can I find information managing/programming daisy-chained spi flash
thanks in advance.


texts: Is my Bob Smith termination valid for Ethernet 100Mb/s?

texts:
This is my first ethernet circuit, and I am a noob in differential signal lines. That is why I want to learn with a "simple" circuit.

I use the reference schematics from the LAN9512 usb to ethernet chip (100mb/s).

My question is with the Bob Smith terminator. The reference schematic uses a rj45 with a transformer and the terminator included. But I want to test an external transformer (next project will be a "simple" ethernet switch).

So, I checked other reference designs, and I found different variations for the Bob Smith circuit. Some uses 51ohm resistors, others 75ohm... I am quite confused here.

This is the termiantor that I am using. It is the only one that I found that uses resistors on both sides of the transformer (i guess that to match impedance in both sides of the transformer)

This is my schematic:

What do you think?


texts:
When you look for "Arduino relay module"s, you usually see one form "SONGLE" that says on it:

10A 250 VAC    10A 125 VAC
10A 30  VDC    10A 28  VDC

My question:

Why do some Arduino relay modules can handle up to 250 VAC but not above 30 VDC?


texts:
Using a BC546 NPN Transistor to trigger an SSR from a current sensor. Sensor to give 1.5-2.7 V out to drive the transistor. SSR requires >= 3 V and uses up to 10 mA.
I want the transistor to fully trigger the SSR (V>3, I=10mA) when a current flows through the sensor.
With R2 = 470 Ohms and best sensor settings (D0) I can get:
Sensor off: V(CE) = 4.57, D0 = 0.29, V(BE) = 0.29
Sensor on: V(CE) = 2.4, D0 = 1.4, V(BE) = 0.62
Sensor on not connected to transistor has D0 = 2.7V
I'm getting 2.5 V(CE) across my transistor, which should have less than 1 V in saturation according to my reading of the datasheet.
I've attempted R2 = between 400-4000 with the SSR only partially operating.
Here's my schematic:

R1 is a possibility for a constant current circuit, which I don't fully understand (currently shorted/not used).


texts: How to share a VCC and a GND across to multiple relays

texts:
I'm working on my first electronics/Arduino project to control two pairs of motors.  Currently, the motors are controlled by a simple four-button, wired remote controller, where each button controls a pair of the motors.  I was hoping to replace this remote with an Arduino/Raspberry Pi and a 4-channel relay board to control wirelessly.  I already have everything set up to where I can control the relays wirelessly through my phone.

The issue I'm having is that I'm trying to figure out the proper way to wire up the relays to the motors.  Each relay has three terminals, and there are a total of 10 wires coming into the controller (remember that 4 of them being redundant as there are two pairs of motors):

Motor 1 up (M1+) x2 --> Relay 1 NO
Motor 1 down (M1-) x2 --> Relay 2 NO
Motor 2 up (M2+) x2 --> Relay 3 NO
Motor 2 down (M2-) x2 --> Relay 4 NO
VCC --> ???
GND --> ???

Wiring up the motors is easy enough.  But I'm unsure of how to connect the single VCC & GND wires to each of the four relays.  Should these wires be split into four?  Or is there something else I need?

I've attached two images: a simple diagram of the wiring, and a picture showing the remote.  On the remote there are four Toneluck MQS-1D microswitches, if that matters.  Thanks!


texts: Confusion regarding step responses of integrator and differentiator?

texts:
I am using matlab to study about step response of integrator and also of differentiator using transfer function modelling technique

But i have two confusion, one in case of integrator is that step response has negative slope as shown in below linked/attached photo

And in case of differentiator i am not able to get step response and matlab shows error as shown highlighted in below attached/linked photo


texts:
I am trying to flash the blink example from SDK v15 into my custom nrf52840 board, I am using pc10056 example.

I connected my ulink2 to swdio, swclck, gnd and vcc of my custom board and I can see on my debug settings but when I try to flash I get Invalid ROM Table error, I tried to change

Here are my settings


texts:
I am looking for some high voltage, high channel, analog multiplexers that I can change the configuration of very fast and I am just wondering if I am looking at this data correctly.

When I look at the IC on
mouser
 it says that the bandwidth of the circuit is 20MHz and when I then go and check the load time on the datasheet it says that the serial clock is capable of working at 5MHz which makes it much slower since you need to send a bit-stream in order to program it....

So I guess it's the serial clock which is the bottle neck for this component right? If you would compare it with for example this from Intersil which is adressed in parallel.


texts: I have built an oscillator configuration at 4-7GHz. At 5.29GHz, the output of the oscillator has resistance R=-189-j*51. How can I use impedance matching and a bandpass filter since I have a negative resistance, for my bandwidth?


texts: Switching between inverting and not inverting a small signal

texts:
I want to be able to choose whether an audio signal being fed into an amplifier is inverted or not via a TTL signal. What's the simplest, cheapest, best way to achieve this? My goal is to replace the mechanical DPDT switch in this guitar sustainer circuit with something silent, controlled electrically, and can be assembled with through hole components.

Here is what I am currently thinking. So you can invert a signal with DPDT switch pretty easily. Perhaps a DPDT solid state relay exists? I found one on digikey, but it was $170. I read I could make a DPDT switch out of an arrangement of two SPST-NO and two SPST-NC switches. SPST-NO switches are cheap, however SPST-NC switches are $20-$30. I can buy four SPST NO switches and one not gate so that I can flip the logic for two of them. Below would be the result. Here's the link to the circuit diagram: https://crcit.net/c/de4ea0a434f9430594dfb446a37e6f1b

The circuit diagram image for SPST SSRs makes them seem easy to replace with MOSFETS, but I wouldn't know which ones to use. Is this an avenue I should explore?

What I have is cheap and simple enough, but I don't know what effect it will have on the signal. I know the SSRs add 6 Ohms of resistance each, but no idea how it might end up filtering the signal. If you know a better way to do this, I am all ears!


texts:
I just discovered a Sainsmart 4-Channel 5V Relay Module for PIC ARM AVR DSP Arduino MSP430 TTL Logic, I don't know how to make links, so I copy the URL here. http://www.sainsmart.com/arduino-pro-mini.html .Maybe the moderator can edit it a little bit.
And I have a question.  I'm in need of an array of isolation relays for a project, and wonder if I can use this device by simply providing a +5v VCC and contact closures between GND and INx.

Thanks for your help a lot.


texts:
I want to control electronic train, using an H-bridge and a voltage divider to detect if there is a train or not.  (Whether the motor is connected to the wires or not.)
When the yellow wire is "+" and when the green wire is "-", this crcuit works fine, and I can detect the train.
But I want the train to be able to return.  When the green wire is the "+" this circuit doesn't work at all.
How can I solve this problem?


texts: Working out the safe continuous discharge current for a lead acid battery

texts:
I have a Numax DC25MF 12v lead acid battery with a quoted capacity of 95Ah (C20)

What is the continuous safe discharge current for the battery? By 'continuous' I mean a few hours without a break, and by 'safe' I mean without shortening the life of the battery.

I can't find the figure quoted anywhere (not directly anyway) and the only Numax datasheet I can find doesn't actually mention the DC25MF model.

Can I simply divide 95 by 20 and assume it'safe to discharge at 4.75 amps?


texts:
I'm fairly new to PCB designing, and it's my first board design.

If I want to add pin number silkscreen on the board, do I have to do it all manually on the board design page?

Can't I do it on schematic design page and pass it over to board page?
Like putting labels on connections and make Eagle automatically show labels on silkscreen layer.

Any help would be appreciated.


texts: How to identify pinout of 7 segment display when data for it is not available online?

texts:
I found some 1-character 7-segment LED display in my toolbox with unusual pinouts. There is one however I can't seem to figure out and I even googled the part number with no results.

The part number printed on the side of it is "MAN4840A350G82", and my camera was good enough for me to show you pictures of how the pins are arranged on each side of the display. There are no other labels.

If I can't find the pinout on google, should I just assume some generic pinout?

I want to be able to use this display in a schematic created with eagle (yes I'm using version 4.17) but I don't want to pick the wrong LED display.

How do I identify what each pin represents on this display?


texts: Would driving transformer with MCU's GPIO cause durability issue?

texts:
For making isolated power supply, I would like to drive a transformer  with two GPIO's of a MCU.
The center tab of the primary will be connected to Vcc. And each end of the primary will be toggled between Vcc and Gnd using GPIO alternatively.

The secondary side the center tab will be connected to the Gnd and each end of the secondary will feed a diode bridge which will be connected to the switching regulator for isolated power.

My question is, would the back noise from the the transformer damage the MCU over time or even cause the MCU to mal-function all together?

Thank you


texts: Controlling a series of LEDs ( AC->DC via bridge rectifier)

texts:
I'm working on a PCB (Christmas Present) to take in A/C to a string of LEDs and control them (with transistors? and a microcontroller). This is a bit out of my league, but it is making me learn quickly. As far as I can tell this should work, but that is a weak statement at best, I'd appreciate any guidance.

My first crack at this, which I have successfully built and it runs stably is just lighting the LEDs. It looks like:

Now I'm trying to add another (far more complex) layer to this, by making the LEDs controllable. The design I've come up with is:

But I have a ton of uncertainty about this. These are my concerns / questions:

The voltage will be entirely difference for every connection on the microcontroller -> Transistor (base).
Is there additional protection needed for the microcontroller's GPIO. I think they would only be in output mode, I just need to pull to ground to switch off the transistor. I've seen suggestions of putting a resistor and/or Zener Diode inline, but that was only in the context of using the pins for input.

Am I even close to having a working design?


texts: How can I estimate reception signal strength for RFM12 or RFM69?

texts:
I want to use RFM69 or RFM12 modules for transmitting data within the house, controlled by Arduino.

How can I estimate the reception quality to adapt the transmission power?


texts: Different implementations of JK flip flop

texts:
I know following variants of SR flip flop:

Using NAND-NAND combination

Using AND-NOR combination

I was guessing how we can obtain JK flip flop for each of these variants. I found below approach showing how we can convert NAND-NAND SR flip flop in JK flip flop:

So, by above approach, we are getting,

S = J'Q and
R = KQ

However I did not find any text / website explaining how to convert AND-NOR SR flip flop to JK flip flop. So I tried myself as follows:

By above approach, we are getting

S=J'+KQ' and R=K'+Q'

I searched online for correctness of this. Didnt found anything. Only found this  page which shows JK flip flip using NOR-NOR gates as follows:

This flip flop comes with KQ and JQ' which definitely does not match with what I have got.

Can someone tell, if I was correct with S=J'+KQ' and R=K'+Q' or I was wrong and the above diagram is correct?

Edit

After some more thinking, I feel I got it.
As we have two implementations of SR flip flop, we are supposed to have two implementations of JK flip flop: 1st implementation replacing forbidden state in NAND-NAND SR flip flop with toggle state and 2nd implementation replacing forbidden state in AND-NOR SR flip flop with toggle state.
What I was trying to do is using AND-NOR SR flip flop to prepare 1st implementation of JK flip flop!!!
If I try to prepare 2nd implementation of JK flip flop with AND-NOR SR flip flop, I get something as follows:

The outcome looks more reasonable. I am getting S=J+Q and R=Q'+K unlike S=J'+KQ' and R=K'+Q' I earlier obtained.
Do you feel this correct? I believe last image before edit is anyway incorrect, right?


texts: Does length of wire to NFC antenna affect ability to read tags?

texts:
Most questions regarding NFC antennas pose the question if it's possible in increase the reading area of an antenna.

I'm curious: given a fixed size antenna, does increasing the length of wire between the reader and the antenna affect the ability to read tags?


texts:
What is the intuitive way of understanding concept of constellations in digital communication? I know the Gram Schmidt Procedure, Orthonormal basis functions and how to find the constellation but just wish to know the physical significance of constellations. Plus in case of QPSK- there are two variants- Offset QPSK and Coincident QPSK, the constellation of the two is the same except for the fact that the transition paths are different. What does this signify? And one more doubt is with Nyquist Theorem for Zero ISI: in this case we get the condition : p(nTb)=0 for all n not equal to zero, the most obvious solution for this is the delta function but why Sinc function is used?
Thanks a lot in advance.


texts: Substituting a capacitor of different capacitance

texts:
If a circuit calls for a capacitor with a specific capacitance, what happens if a capacitor with a different capacitance is substituted?

I have a circuit that calls for a 250uF capacitor to power a small speaker. What would happen if I substituted it for a capacitor with less/more capacitance?

Why can't I substitute it for a 220uF capacitor?

Why can't I substitute it for a 300uF capacitor?


texts: Design considerations for bifilar coils for Wireless Power Transfer

texts:
I found many different DIY videos and posts demonstrating the concept of wireless power transfer using inductive coupling, however, they have limited explanation on theoretical calculations and design aspects. Thus, I hope to find some guidance on this forum. I focused my attention on the pancake and bifilar coil geometries since they seem to be compatible with the design constraints of the receiving coil. Since the receiving coil has design limitations, all bets are on the transmitter coil, so it must be more powerful to compensate for the low receiving efficiency. The goal is to be able to receive at least 100mW of power.

The Receiving Coil

The receiving coil will be a simple pancake coil PCB printed with the thickness of traces being 300um. The width and the spacing of the "flat wires" would be equal and can be >4mm, and the outer coil radius 100mm. These parameters would dictate the number of turns in the coil. At this point I am not concerned about the N1/N2 winding ratios of the transmitting and receiving coils since I am planning on using a voltage regulator at the receiver to maintain the required voltage.

The Transmitting Coil

The transmitting coil would be the Tesla's bifilar pancake coil - I would just pick a random speaker wire and make as many turns as needed to approximate the outer diameter of the receiving coil. It is not clear, though, how to wind the double-stranded wire: two strands side-by-side on the same plane (left), or one strand on top of the other forming a stack of two parallel coils (right)?

I have also seen some speculations on how to connect the two coils of the bifilar coil, and it is not clear which one is suitable for my application: the one that connects internal end of one coil to the external end of another coil (left), or the one that connects two internal ends (right)?

The questions:

What are the design recommendations for the Receiving coil (given above constraints)?
What are the effects of the two winding approaches, and which one is more suitable for my application?
How the coil interconnection approaches affect the overall power transmission efficiency and which one is more suitable for my application?
Should I have thicker wire with less turns or a thinner wire with more turns for the transmitter coil?
In both connection scenarios I end up with three points (x,y,z) to which I could connect the driver circuit. What are the connection approaches and driving options that are valid? I found several examples that use a single transistor and a battery to drive the transmitter coil, but I was hoping for a slightly more complex and effective suggestion.
Is the spiral receiving coil (shown above) compatible with a bifilar type transmitting coil?


texts: So why aren't supercapacitors used more often?

texts:
I've recently found out that supercapacitors (C >= 1F or so) are actually a thing.

I went searching for their advantages and disadvantages.

They don't hold as much energy as a battery, but can endure many charge and discharge cycles.
They have a lower inner resistance, so they can output a great current.
Also they're not cheap, but they're not prohibitively expensive either.

From what i gather, they could be a great solution for many problems, and yet, they are rare and I've never seen them around.

Why is that? They seem so good. What's the catch?


texts: What is the ppm in the crystal oscillator?

texts:
I'm a student and I'm working on a low power communication project. I am trying to design a PCB using the TI CC2540 sample design. There is a MC-306 (32.768kHz, 12.5pf, and 20/50ppm).

I don't know what the 20/50ppm rating is. For me, the size is very important, so I decided to replace it with the FX135A, but its ppm is -20/+20. Will it cause a problem if I use this one instead?

What is the ppm rating in the crystal oscillator?


texts: Does an AC rated fuse blow at the same current DC

texts: Bought some 30A fast acting glass fuses. Thought they were rated 32VDC but I noticed when they got here they are rated for 32VAC. So would they still blow at 30A of DC current or would they allow greater than 30A?


texts:
I built the over and under voltage protection circuit based on the LTC4365 from the May 2017 QST page 32.  Works ok.  The LTC4365 uses an external resistor voltage divider to set the over and under voltage set points. In studying the block diagram, I don't understand why the over voltage (OV) external voltage from the external divider circuit is LOWER than the under voltage (UV) value from the external voltage divider.

The block diagram shows that the OV and UV inputs go to separate comparators with the other input of each comparator going to +0.5V.

How is the external voltage from the external divider circuit is LOWER than the under voltage (UV) value from the external voltage divider?

he LTC4365 data sheet is here


texts: Reason for USB power bank LED to be always on?

texts:
I hope this is somewhat on topic.

I received a free 2200 mAh USB power bank today and noticed that inside its casing it has a blue LED that is always on, even when not giving charge or being charged.

Are there any common design reasons for such behavior in a device of this kind? To me it just seemed peculiar for a device meant to retain energy.

(I don't have much experience in electronics)


texts:
I have a 12.3V power rail, which is sourced from a 2A 12V AC wall adapter.

The 12.3V rail supplies a 3A 4V SMPS, which sometimes sees large load fluctuations from almost 0A through to 2A instantaneously, and back again.

During the load fluctuations, the 12.3V rail can see a voltage drop between 100mV - 600mV depending on load, along with switching noise from the SMPS.

Example of 100mV voltage drop for 0.5ms on 'unfiltered' 12V rail with switching noise.

Originally, for a separate 5V supply I was just running a linear regulator straight off the 12.3V rail, for around 40mA @ 5V. Although some amount of high frequency switching noise was getting through the regulator and onto the 5V rail.

I decided to add a low pass LC filter, between the 12.3V rail and the linear regulator. That did an excellent job, and almost completely removed the switching noise, and slowed the dV/dt during the load transients sufficiently that the linear regulator could still provide a stable 5V. The transients were still detectable, although were reduced almost into the noise floor.

Example of implementation and testing of 'filtered' 12V rail, showing voltage drop, and effects of under-damped low pass filter causing the extra oscillation (ringing).

Despite this the 'filtered' ~12V rail still would drop 100mV - 600mV exactly like the 'unfiltered' 12.3V rail.

The problem is that I need to draw power from the 'filtered' ~12V rail to power a 12V sensor. The sensor has non-polarity variable current output and will be at the end of an 75m+ cable.

If I connected the 12V sensor directly to the 'filtered' ~12V power rail, then the 100mV - 600mV voltage drop occurs, surely would it not propagate in a wave down the length of the cable? and might (should?) affect the stability of the current output of the sensor, and any derived readings.

I'm struggling to determine the best approach to achieve a stable 'filtered' ~12V rail, from the 'unfiltered' 12.3V rail.

I've simulated a number of low pass topologies, and then build up the circuits, although I've been struggling to get the simulations to match the real world filters.

Approaches I've considered include 1st and 2nd order low pass RLC filters and extra stages, using high speed switching diodes to isolate the 'unfiltered' rail while it's at a lower voltage than the 'filtered' rail (during the voltage drop). I've also looked at emitter follower capacitance multiplier circuits and even looked at just simple RC low pass filters.

My (self imposed) constraints are to stick with ceramic capacitors (lifetime & reliability), although Tantalum caps can also be considered. I've used miniature SMD components (minimum 0603) to limit loop area and emissions.

The 'filtered' rail needs to run at a minimum of 12V, and I suppose the extra 0.3V could be dropped to achieve superior regulation if needed.

For my approximate model to simulate the 'unfiltered' 12.3V DC rail is to use a square wave with 300mV peak to peak at 12V DC offset, running at 200Hz with 90% duty cycle. Although, the load that causes the voltage drop occurs at a regular frequency, in reality it occurs after random intervals rather than continuously.

Example simulation of low pass filter for 'filtered' 12V rail, problems include large over-voltage at startup, and unstable oscillations during changing load. Despite that, during steady state ripple is less than 10mV.

My question is are there any low pass topologies that I may not be aware of, or something that can be done to improve the existing filter?

Kind regards,

Edit: Potentially better solution. I've come up with the following circuit, which is a two stage RLC filter, that borders slightly on the under-damped side, although at maximum load will still provide atleast 12V, while also sticking to the restriction of only using Tantalum or Ceramic caps


texts:
Most Microcontrollers (uC) have an Analog to Digital Converter (ADC) as part of their peripheral set, which is phenomenal as this integrates two components into a single package.  These ADCs are usually register mapped as well, which allows the data to be extracted quickly and easily.

In spite of this tight integration, you can still purchase external ADCs.  I can see several cases for these:

The ADC needs to be isolated from the uC.
The bit depth of the ADC samples needs to be higher than the uC's ADC.
The voltage to sense is far from the microcontroller and long analog lines are not acceptable.
The voltage to sense is in a harsh environment not suited for the uC.
The external ADC samples much faster than the uC's ADC.
The reference voltage for some sample is different than for others, requiring multiple Vref pins (and thus multiple external ADCs).
The current uC doesn't have enough ADC channels and the cost of putting a new uC is prohibitive.
The external ADC consume less power than the uC's ADC (I would need an example to believe it).
The ADC channels must be sampled simultaneously (rare scenario).
The cost of programming firmware at manufacturing time outweighs the cost of the more expensive ADC part (unlikely).
The PCB has space constraint and no uC can fit (unlikely).

This is all well and good, but what strikes me as odd is that external ADCs are usually quite a bit pricier than their uC counterparts, yet provide equivalent functionality.  For instance, you can purchase a EFM32Z part with a 12bit 1Msps ADC (with internal reference) for about $1, or you could purchase an equivalent 12bit 200ksps ADC for about $3.50 (same speeds(ish), relatively same power numbers, etc) and perform the same task (extracting ADC data).

The question then becomes: are there compelling reasons an engineer would favor an external ADC over a uC's ADC when the latter can perform the same functionality?


texts: What would the output of a 7447 IC be if the input was above 9?

texts:
Since the input is four binary digits, the input could conceivably range from 0 to 15. If you had an input of, say 2 and 8, would you get hex, would you get a meaningless output, or would it not output at all?

We used this, along with a 7490 and a 7404 outputted to a 7 segment display for a intro to engineering lab, but we were not able to make the output meaningful, and I'm still confused as to what the output meant.


texts:
I have a circuit which currently runs off of either a 12VDC wall wart adapter, or it falls back to a 9V battery if the wall wart adapter is not connected. My circuit currently uses a chip which requires a clean 8VDC source in order to run.

Right now, I just have an 8V LDO regulator burning off the excess power as heat, but I've just realized that my 9V cells can drop as low as 7.8, and still have 50% capacity (mAh) remaining, and my LDO requires that the supply power be at least 0.2V greater than the output voltage, or it just shuts off.

What would be the best approach to constantly having an 8V low-noise output assuming a potential input voltage swinging between 7V and 12V? My initial guess would be to use a flyback or buck-boost switching transformer, which could handle the input swing being so large and the undesired circumstances where Vi < Vo.

However, I can't seem to find any 8V fixed output buck-boost regulators. Also, one thing that has me confused is that both fixed-output and variable-output regulators both require external components (diode, capacitor, inductor). Why do both require external components?


texts: Circuit for connecting externally power instrument to MCU

texts:
I have externally powered instruments that I need connected to the ADC inputs of an MCU. They output 0-5V analog, and the MCU accepts 0-3.33V. There is no guarantee of the voltage difference in grounding, although they should be connected to the same building ground (who knows where).

I'm stumped on the most efficient circuit for this:

Differential voltage measurement (to eliminate many sources of noise)
Voltage divider (5.5 -> 3.3)
Voltage clamp (to prevent overload to the MCU)
Are not connected to the same ground locally

With some tries, this is the best that I've come up with. However, I'm not sure it's even theoretically a good design to accomplish this.

Updated circuit using AD623


texts: Minimum separation between antennas in receiving

texts: It's known that there has to be a separation between antennas of same frequency to minimize interference. But this is really necessary when antennas are mostly in reception mode?


texts: Where can I find information on interfacing an MCU with an HDMI display?

texts:
I am just starting the process of creating a product that will have an HDMI display (not chosen), but I don't quite know where to start. I have never delved into the realm of Displays, and don't know where to look in terms of what MCU to choose, what supporting electronics I would need, etc. If someone could point me the the right direction/ offer some insight on their experience with the process, that would be great.
I am starting from ground 0, with nothing yet but an idea.


texts: How to cheaply switch between two sets of 7-input-wires?

texts:
I am trying to make a water level sensor.

I want to use a single circuit for two water tanks. For this I need to be able to switch between two sets of 7-wire-inputs to the circuit (the 7 wires that are in the water tank in the diagram below.

What is an simple/elegant/cheap/easy way to do this without having to use 7 switches?

Circuit diagram:

UPDATE:

Thanks for all the answers!
Some clarfications:

I will using a 9V battery source, not mains.
I thought of one more solution: the circuit inputs will be connected to a CAT5 socket, and the input wires (CAT5 cables) from the two tanks will have connectors. So I can simply switch cables and use the one circuit.


texts: Benefit of (logically/virtually) separate I/O and memory bus

texts: In my course on embedded systems, it is explained that memory inputs can be separated from I/O inputs using a "mode bit" for the address decoder. The most obvious advantage of this is that the amount of address lines need to be decoded can be reduced if you have a separate addressing system for your memory and your I/O. Are there any additional benefits? Does having these logically separated have other benefits such as being able to use different clock speeds or transfer logic?


texts: Automatic calibration of a zero cross detector latency

texts:
I have a circuit similar to this one (different component values, different uC):

I expect a large phase error in the ZCD. The load is purely resistive and of unknown value between 100W and 1000W.

I am reluctant to stick an oscilloscope in the mains, and do it for each device produced, and then program the measured latency in a special eeprom location.

Is there an algorithm, which through a specific test output signal and polling the input signal, the micro can measure the latency and thus estimate the true zero cross from the measured one?

EDIT:

This is the exact circuit, with a scope shot. Below is another shot with mains AC on CH2 and circuit output on CH1.

From both measurements, I conclude that regardless if the micro interrupts on a rising or falling edge, the error will very roughly be about 1.6ms (subject to temperature, mains voltage, component ageing, atmega silicon variations on the input).

As the laziest approach possible, I plan to hard-code this value in the triac control and see what happens.

In conclusion, I want to say that this worked out exceptionally well. Debounced interrupt measures the pulse width and estimates the true zc in the middle of the pulse, all in less than 200 lines of C.


texts: What's The Purpose of One Additional Diode Here

texts:
I'm trying to build a AC/DC buck converter and I've found an application note from ST. Two diodes are connected series at input to rectify the AC, but one is enough to have a half wave rectification.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj1sN3e483uAhUDnVwKHegCBboQFjAAegQIBBAC&url=https%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fapplication_note%2Fdm00286922-stevalisa178v1-5-v1-w-30-khz-buck-demo-with-viper01-stmicroelectronics.pdf&usg=AOvVaw0-4Brdx97P7k1oa_wdEtXu
What is the purpose of second diode here?


texts:
I am trying to use usb battery bank as a backup power source for my diy project.

Project is using arduino to control transistors and to turn few devices (like
pumps and lights) on and off. Power source is 12v 3a adapter.

I would like to have usb with battery connected always and if possible to charge
it when main power is available.

Controller must know when main power is not available that it is running on battery.

This schematic is based on answer of
Automatic Power Selection Circuit

simulate this circuit – Schematic created using CircuitLab

N Mosfet is added to detect if main power is not available.

Will battery charge if I remove D2 diode? If not how could I get charging to work?

Is there anything wrong with this circuit or is there better way to
do this?

Update:

I added voltage regulator from 12v and diode to 5v. Is there something
else required for battery charging? Battery is standard 2200ma usb battery pack for phones.


texts: What technology to use to send data/Ethernet (about 128 kbps) over copper cable (4km)?

texts:
What thechnologies can i use to send data/ethernet (w/ a symmetrical traffic throuput of about 128kbps) over copper cable (4km)?

1)SHDSL would be an option !!(but I couldn't find any chip with datasheet that would allow my design to go on)

2)On the other hand SHDSL rates are very high. Isn't there a simpler technology/solution that would allow low to medium rates over copper cable?

3)ADSL technologies could be attractive as their chips should be cheap. But the asymetric nature of the tranceiver makes it unlikely to be usefull, since the adsl modem chip@CPE is slinked to a DSLAM chip at CO side(as fas as I know). Is there any adsl(DSLAM) single channel chip OR any solution that would allow the xDSL variants to be used?

4)other technologies (any hint is highly appreciated)??

Regards


texts: Shift Register turning on Transistor for LED Cluster

texts:
I have a question concerning using 74HC595 with two transistors to power a LED matrix. My goal is to make an 48 x 8 LED matrix using a cluster of 5 LEDS per unit (as opposed to only using one led as shown in Ref 1). I am having trouble making Ref 2 work with the shift registers and I can't figure out why (I suspect that the shift registers are not supplying enough voltage to switch the transistors. I've attached a simplified schematic. Please let me know what I am doing wrong, thanks!

Parts:
NPN = 2n4401 w/ 1k resistor

Ref 1)
My template for constructing the matrix
http://www.instructables.com/id/48x8-SCROLLING-MATRIX-LED-DISPLAY-USING-ARDUINO-CO/?ALLSTEPS

Ref 2)
My reference for using two transistors
Using an NPN vs a PNP transistor


texts:
My local hackerspace has a CNC machine.  I can give them my Gerbers and they can print out the PCB.  The machine does not plate VIAs.  I need to do this after the CNC machine is finished.

What is the best process and materials to use?


texts: Mysterious Noise Issue in Automotive Ignition Coil Application, Arduino

texts:
I'm building a circuit to count RPM based on watching the negative pole of the primary coil in an old automotive ignition coil. I had no illusions this would be easy, but here I am stuck even though I saw it coming.

Background on circuit (Odd NPN Circuit behavior)

My problem is when I tested my circuit on a 1960's distributor tester, my card was acting as if it was getting a (consistent) 2.5:1 ratio signal frequency: My board would switch at 17.5 and 27 HZ instead of 42 and ~68 respectively.

I was getting the predicted 80V spikes, and found my Zener diode was clamping the voltage, but too slowly! I 'fixed' these spikes with some resistors and caps, my final input to the CPU was reasonable (and worked when tested with my simulated signal).

But the switching would happen in the wrong spot. I kept adding more protection, and in desperation I found that even unplugging the input to the Arduino's pin didn't change the false triggers.

I'm at a loss of where to look. I am regulating the power down to 9V from "12", and the +9V, +5V (on Uno board), and Ground rails showed plenty clean even while watching the giant spikes elsewhere in my circuit.

Sorry for the long rambling post, but I'm kinda stumped. Any suggestions or things to test? About the best I can come up with is my scope probes were on "1x" instead of 10, and were somehow eating spikes, but it seems unlikely something that won't even show on the scope can cause these issues.... Doubly so since the effect didn't go away with the added load.

Notes:
I'm actually using an Uno board, will change to Arduino Nano once I get bugs out.

Bottom left circuit is a signal generator board I use for testing.

The circuit with the blue boxes is the input. Sorry there's so much on the schematic, but I'm not sure where the problem is so I'm erring on the side of completeness. R6 and R7 were replacing a single 12k ohm to allow me to keep my cap ahead of the CPU input.

Thanks in advance, I'm happy to provide any more info anyone wants... I'm not sure what's helpful here. I was thinking of a 20V Zener after the reverse protection diode (or in parallel with C4), but if the problem is that Zeners aren't fast enough, it won't really help, will it? Thanks again!!!!!


texts: What is the use of fast diodes vs rectifier diodes?

texts:
I read

https://new.abb.com/semiconductors/Diodes/fast-recovery-diodes

And it makes fast recovery diodes sound like it’s only for converting dc to ac while rectifier diodes are for converting ac to dc. At the same time it sounds like fast diodes are only for frequencies that are too fast for the rectifier diode. Which one is it?


texts: Detecting a very fast moving object with a photoelectric sensor

texts:
I want to use a photoelectric sensor to detect a ball that is moving past the sensor at 85mph, which also equals 136kph or 3800cm/sec. The ball is 7cm in diameter. If my logic is correct that means the ball will be in front of the sensor for 7cm/(3,800cm/sec) or 0.00184 seconds or 1.84 ms. Actually, it will be in front of the sensor for a few ms longer because of the width of the sensor eye itself but I think we can safely ignore that.

I am trying to understand what sensor would be able to detect the ball. Many list something called 'response time'. If the response time of the sensor is 2ms does that mean it would not detect this ball? If it is 0.8ms would it? I am going to call an engineer at one of the sensor companies but was wondering if anyone here might be able to enlighten me about how these sensors work in terms of fast moving object and what specification to focus on.

Thanks!


texts: Precision Full-Wave Rectifier: Why is the signal's biggest magnitude at DC?

texts: I built a Precision Full Wave Rectifier Circuit, like in the following figure( with better amplifiers) to rectify a sine wave of 1kHz. As expected i got a rectified wave with 2kHz but doing its FFT analysis i noticed that the biggest frequency component is at DC(0) can anyone explain me why? Also, I'm sampling this signal with an ADC at much higher frequency around (40 kHz), it order to measure its RMS. Do you find appropriate  to build an anti-aliasing filter to the rectified wave and which frequencies should i reject, everything above the 2kHz  ?


texts: EAGLE PCB, how to specify an out-of-board component?

texts:
This might be a very basic question. I have a schematic where some of the components are outside of the board.

For example, for a power supply, I have a switch and a transformer that are on the schematic, but I want them to be placed outside of the PCB, for this I want to place the appropriate pads to allow some wires to be soldered. What's the right way to do this?

Thanks!


texts: How far a 220V AC line should be placed to avoid EMI?

texts: In my apartment I have a control panel for a solar water heater, this panel provides AC for a water pump and an electric heater approx. 2500 W combined. Unfortunately this AC line is very close alongside temperature and water level sensors' wires, so when I turn on either one of them, the temperature reading starts fluctuating. How far the AC line needs to be placed from the sensors' lines?


texts:
German Wikipedia lists Transistors according to EN 60617-2 with the symbol

I wonder whether this symbol is correct, or it's actually the old one.

I don't have the standard available, but in most cases, EN 60617-2 is trying to simplify the symbols. Therefore I would expect

no circle
no pin descriptions (B, C, E)

Other transistors in that list do neither have a circle nor letters.

Can someone with access to an authorative reference clarify on how to design it correctly?


texts: How do I use the CA3306E ADC with Raspberry Pi 2?

texts: I have successfully run the MCP3008 ADC with both the Arduino and the Raspberry Pi, however, this ADC seems to be way beyond me. The connections are not the simple SPI ones as they were in the MCP3008. In the datasheet too, it mentions the connections, but it has an external comparator, I believe, to get it to work and there is no code (obviously). Every example code that I found online for this ADC uses Linux Kernel Module, and none of those codes are complete that I can copy and paste it to test and then make changes accordingly. How can I get this ADC to run?


texts: Phasor Measurement Unit (PMU) vs Synchro-check Relay

texts:
What is the difference between a Phasor Measurement Unit (PMU) and a Synchro-check relay?

I need to know if Synchro-check relay can be used as replacement for PMU in a Synchrophasor data system.

We will be incorporating this synchrophasor data system with Automatic Generation Control (AGC) of a Diesel Generation during grid synchronization.


texts: Error Connecting PIC12F683 to MPLABX with PicKit3

texts:
Disclaimer: I am a complete noob when it comes to programming chips with a dedicated external programmer such as the PicKit3, as well as writing code for chips (especially not in C) so bear with me :)

I am attempting to connect a Microchip PIC12F683 8-bit microcontroller to my PC with a PicKit3 and MPLAB X. My main goal is just to be able to do a basic "Hello, World" by flashing an LED on one of the outputs. I have MPLAB X opened up with a new program in C with the following code:

/*
* File:   newmain.c
* Author: Malachi
*
* Created on March 20, 2018, 7:04 PM
*/

#include <stdio.h>
#include <xc.h>
#include <stdlib.h>

/*
*
*/
int main(int argc, char** argv) {
    TRISIO = 0; // set as output
    while(1) { // infinite loop

    GPIO = (1<<4);
  }
    return (EXIT_SUCCESS);
}

When I hit "Run Main Project," it successfully builds (using the XC8 compiler I was instructed to install by MPLAB), but when it connects to the PicKit3, it says the following in the console:

Connecting to MPLAB PICkit 3...

Currently loaded firmware on PICkit 3
Firmware Suite Version.....01.51.08
Firmware type..............Midrange

Target device was not found (could not detect target voltage VDD). You must connect to a target device to use PICkit 3.

The PIC12F683 is wired to the PicKit3 like this:

simulate this circuit – Schematic created using CircuitLab

I'm not sure what this error means, or how to fix it. Does anyone have any advice as to what my next steps should be?


texts: How does sender and receiver clock time periods synchronize in data communication?

texts: In asynchronous data communication, Initiation of data communication between two stations(sender and receiver) involves synchronizing their clocks to ensure both stations are agreed upon same bit times. How does this process takes place? How do sender and receiver agrees on same clock period? If possible point me to some resources too.


texts:
I'd like to read data from a SD card using a microcontroller (through SPI protocol). Looking for a slot for the SD card, I saw two different boards.

https://www.adafruit.com/product/254

This one has apparently a digital buffer and other components

https://www.ebay.it/itm/Micro-SD-TF-Card-Breakout-to-DIP-Board-Module-for-Arduino-1573Z/163459088257?hash=item260eebbf81:g:VUIAAOSwsY1c9DJV

This one on the other hand looks like is only a direct connection to the SD card pins.
Why is a digital buffer needed in case? I didn't really get in general what digital buffers are used for.
Alternatively, would the second board be enough?


texts:
I am working on an application where I want to make wireless communication between two embedded devices. The core problem here is that I want to put one of these devices in a room that's totally built as concrete, even its door will be concrete.

Does Bluetooth 4.0 support that?
If not, Is there any solution?

Thanks


texts: PIC18 inline asm problem: error (195) expression syntax

texts:
I'm building a bootloader firmware, and now I want a simple app (LED blinks) to test calling bootloader from application itself.

I'm currently doing:

    #include <stdio.h>
#include <stdlib.h>
#include <p18f25k50.h>

#pragma config FOSC = INTOSCIO
#pragma config FCMEN = OFF
#pragma config BORV = 3
#pragma config CPB = OFF
#pragma config CPD = OFF
/*
 *
 */

int main(int argc, char** argv) {

    int i, j;

    TRISC = 0xF0;

    LATCbits.LATC2 = 0;

    while(1) {

        if(!PORTBbits.RB3)
         _asm goto 0x1C _endasm

        LATCbits.LATC2=!LATCbits.LATC2;

        for(i=0;i<1000; i++) {
            for(j=0; j<10; j++) {

            }

        }

    }
    return (EXIT_SUCCESS);
}

And, I get

newmain.c:33: error: (195) expression syntax
(908) exit status = 1

The error is showing me the one assembly line I have in my code, which is supposed to send MC's instructions to absolute bootloader entry point.

After trying to build. I'm using MPlab X, with XC8 PRO compiler.

Does anyone have any idea what in here is wrong?

Thanks in advance.


texts:
I'm trying to design a Solid state circuit breaker for a 3phase AC system with a rating of 690V, 1000A. As, the stray inductance contributes to the voltage peaks in the system I'm trying to protect the power electronic devices in several fault conditions. currently I'm simulating several topologies of the same with on Simetrix. However, it is getting difficult to find practical values like stray inductance, resistance etc in the system, to get more practical results on simulations. I've been simulating with a lumped inductance of about 10mH till now. What are the several factors that I need to keep in mind while designing the same? Also, Where can I find the required values to model the circuit efficiently?

Please let me know if the question is vague, I'll try to explain what I'm doing more clearly.
This is the single phase equivalent. Ignore the values of the devices for now.


texts: How to read polar coordinates of radiation pattern

texts:
I have a PCB antenna which datasheet provides the following radiation pattern graphs:

There seems to be a "weak" direction which the antenna signals is going to be very weak.

Which direction is the "weakest" in signal propagation for this antenna, especially corresponding to the 270 degrees coordinate of the XZ graph? Is it -X or -Z direction?


texts: Way to reset an MCU when it's GPIO output becomes constant HIGH or LOW instead of a low frequency PWM

texts:
In one of our projects, we are observing MCU hanging up supposedly due to EFT. WDT is not helping. The only way to get the device into working condition is to reset the MCU by reset pin or power cycle.

Resetting/power cycle is not the most convenient way of solving this issue. I have an idea which can solve the issue but I am not sure how to implement it or whether a standard IC exists that can do the job. This IC should not be an MCU because this IC itself can hang.

Idea is to generate a low frequency PWM by toggling a GPIO which is then fed to a circuit/IC. The circuit/IC resets the MCU if it doesn't receive a PWM. I specifically need a PWM instead of constant HIGH/LOW because when the system hangs, the PIN can either get stuck to a HIGH or a LOW position.


texts: Some questions on optimizing a Schmitt trigger to eliminate possible glitches

texts:
Above is a Schmitt trigger circuit using a LM2903 open collector comparator. On the left side the incoming pulses are mixed with noise. Before the noise the desired clean 5Hz incoming pulse train looks like:

After adding up to the incoming pulse the 5000Hz noise itself is 3V and looks like:

And at the non-inverting input the noisy signal becomes as:

The noisy output pulse train becomes:

And here is when we zoom a "rising edge" you can see the glitches:

I have used similar easier circuits before but there are some points to optimize and improve this circuit.

My question is:

To eliminate the glitches at the output, it seems to me there are two options here. A low-pass filter which blocks above lets say 500Hz freq. or a higher hysteresis which is 5V between upper and lower threshold.

1-) But if the noise is not known and is a "possible noise" what would be the safe improvement to this circuit to eliminate possible glitches from a better design perspective? A low pass filter? A higher hysteresis? Or both?  Is C1 already forming a lowpass filer?

2-) Although I know the hysteresis concept and its benefits I'm unable to see that in simulation. How can I see the upper and lower thresholds of the hysteresis in simulation? Can it bee seen by looking at the voltages at point X or Y? But X is the non-inverting input and Y looks like fixed by voltage dividers. How can I increase the hysteresis and see the actual lower and higher thresholds? I tried playing with R1 and R4 values and couldn't succeed.

edit:

I attempted to create noise with a concerned citizen's suggestion. But I guess I didn't get it all right since I get the following error when trying to simulate:


texts: Best options for operation of rotary incremental encoders with micro controllers

texts:
At my workplace, I found a measuring device with six rotary encoders. The device is from the early 1990s. I wanted to reactivate the encoders, I even found software for it on floppy disks. However, to operate the device you need a so called DRC-Card, which reads the encoders (see picture 1). Exactly this card is now unfortunately not to be found anymore.

So I thought about the possibility to use a microcontroller instead of the DRC-Card to read the encoder signals and transfer them via USB to a PC. I would have to rewrite the software.

I should be able to write the software, but unfortunately I do not really know anything about electrical engineering.

Therefore I turn to you with the request that you give me advice if you think this project is possible and how I can best start with this project?  Maybe you also have some advice on which micro controllers or other components are suitable for my project?

Below, I will list some more information about the encoders I have found so far. (The manufacturer did not respond to my request and a data sheet is no longer available online. But I found the data sheet for an encoder, which is probably the successor model, see picture 2.)

Manufacturer: Gurley Precision Instruments
Model designation: 8211-1800-CCPA
Encoder Type: rotary incremental optical encoder, quadrature 2 channel
Max. number of Lines on Disc: 1,800
Max. pulses per revolution: 14,400
Max. frequency response with highest interpolation factor: 600 kHz
Input Power: +5 VDC
Encoder output: sin (phase A), cos (phase B), index

if possible all six encoders should be read simultaneously or with as little delay as possible. The rotary position of all encoders is used to compute a position and orientation.

Thank you very much, I am looking forward to any feedback from you.

Picture 1: Encoder connections to the (now unobtainable) DRC Card

Picture 2: Description of the successor model

Picture 3: Advertisement for the Encoder


texts: How many amperes can pass through drain-source of a FQPF9N50C if 3.3v are applied to gate-source?

texts:
I a playing around with this N-channel mosfet I found at home (FQPF9N50C). Using this simple circuit:

I am able to turn on an off the 12v load using by connecting 3.3v to the mosfet. The load is a small motor, was the first 12v thing I found, the real application will use a 12v 20w lamp. And that triggered my question.

How can I know how many amperes can pass through the mosfet when using 3.3v to switch?

Im clearly not very experiences on this field, just doing this for a hobby project. Tried reading the datasheed but I find it a bit hard to understand.


texts: It is known that formula for skin depth is only applicable if waveform of the voltage is sinusoidal. So, i have an smps which works at 83khz frequency (square wave). What is skin depth for such frequency? I have heard something about equivalent sinusoidal frequency concept, but i dont understand how to apply it.


texts:
I am using STM32F051 MCU in my project. System requirement is minimal current consumption. The signals that I am processing are very low frequency (almost DC)
I decrease the system frequency from 48 MHz to 8 MHz (turn off PLL)and barely see any decrese in the current of my board. Approximately 5 mA decrease.
In the datasheet they talking about ~25 mA of decrease comparing 48 MHz to 8 MHz.
Do you know why?

I am using GPIO, 3 timers, UART and ADC (3 channels)


texts: Is it a good idea to connect the Neutral point to your common ground in your PCB?

texts:
I am making a PCB that uses AC Mains power where 120VAC is converted to 5VDC with the help of AC/DC converter. The 5V output is then supplied to my digital circuitry. The main confusion I have is to whether to connect the neutral point of the Mains power to my common ground of my PCB or not. In theory, it shows no harm. I have shown the example circuit below where I=0 between mains's circuit and my digital circuit but I am still not sure if its still a safe thing to do.

If I did not connect my common ground to the neutral point, would there be any EMI/crosstalk issue on my digital circuitry?

simulate this circuit – Schematic created using CircuitLab


texts: What exactly is the signal strength seen in API for BT/WiFi receivers?

texts:
I understand why dBm is used and how it's calculated and what the usually negative value means. However what I'm interested is of what exactly this measurement is ?

Is this the absolute signal strength of the transmitter in a certain position ?

Is this the signal strength in receiver considering it works at lower Watt than transmitter (100mW in WiFi) ?

Is this the difference between the noise and signal ?

Is it related to receiver or transmitter ?


texts: MPPT Three-Phase Rectifier - BLDC Generator Project

texts:
I'm building a MCU controlled 3phase rectifier that allow voltage and current control.
The generator is a BLDC motor (Kv=100, Imax=30A, Poles arrangement=36N42P).
It will produce from 16v to 50v depending on rpm.
This unit will charge a 16s li-ion battery (67.2v) and/or feed another BLDC motor.
The whole setup is mounted inside an E-bike and the generator is replacing the pedal drive train.
In order to produce a decent voltage to feed the DC bus we need a DC-DC converter.
I've chosen to use a boost-converter circuit directly from the rectifier and motor inductance. This is often used in electric regenerative braking.
I build this schematic below and it worked as intended. I could get an adjustable voltage depending on the duty cycle and the motor rpm.

simulate this circuit – Schematic created using CircuitLab
The current will be controlled through an N-Mosfet depending on the user demand. (User controlled torque or MPPT Mode)
Now I've designed a closed-loop circuit that allows me to regulate all this stuff.
A Voltage that match the DC Bus and a current that match the demand.
Because I'm a mechanical engineer and not an electrical engineer I need help with mosfet drivers and proper design of such a circuit.

Do not pay much attention to the 12v supply and Amp sensor of my circuit. They are pre-assembled board based on the chip drawn.
What are your impressions ?
Does the MOSFET drivers are correctly implemented ?
Thank you for your attention.


texts: Can you combine two 12v DC 600mA adapters to make one 12v DC 1200mA adapter by combining the wires together and plugging both 600mA adapters in?

texts: Can you combine two separate 12v DC 600mA adapters to make one 12v DC 1200mA adapter by simply combining the wires together and plugging both 600mA adapters in?


texts: Is this bandwidth calculation exactly correct?

texts:
Calculating bandwidth for a data bus is like the following in a text I read:
"The bus cycle speed is 200 MHz with 4 transmits of 64 bits per clock cycle. The bus bandwidth is then 200*4*64/8=800*64/8 MBytes per second which is 6400 MBytes per second."

But isn't this an appromixation since MHz is 1000 Hz and MBytes is 1024 bytes?


texts: Is wire-wrap spacing and consistency important in electromagnets?

texts:
I'm creating an electromagnet (several, actually) to test a hall effect switch. I understand that more wire wraps (turns) increases the magnetic B-field, as does more electric current. Adding more turns of course increases the resistance because there is more wire. I can specify the voltage and change wire gauge to accommodate whatever current is needed, so I have some flexibility.

My questions are, for a given length of core (ferrite rod):

Do the wraps need to be fairly uniform and consistent, or are small gaps of little consequence?
How do 2+ layers of wire affect performance? I assume that as layers are added and radius from core center increases, the effectiveness of those layers diminishes. Is this correct, and is there a "rule of thumb" as to how many layers I should consider a maximum?


texts:
I would like to automatically poll and log certain memory locations on the STM32 I'm working with through the j-link debugger I am using to debug the system. Is this possible through the JTAG or SWD interface? Where should I start looking for more info?

Is it possible to redirect stdout or similar to a file through the j-link?

(STM32F0 w/ IAR IDE)


texts: Connecting a single-colour LED strip to a RGBW controller

texts:
I have a RGBW strip that is connected to a RGBW controller; Is it possible to connect a single-colour strip (rated at the same voltage) to the same controller? If so, how?

Thank you for your answers.

PS: I don't have access to the power supply of the controller.


texts: What happens to the flow rate of water through a hydro electric generator when the electrical load changes? This question refers to what happens in the absence of human intervention.


texts: How to get the 741 op amp to work as a linear amplifier?

texts:
I'm trying to run the 741 as a non inverting voltage amplifier.

I did the circuit in proteus simulation and it works well to get 2x the input signal.

For example, if input voltage is 1V, then I get 2V on output pin.

So for this implementation, I the same circuit on the breadboard:

But on the breadboard, I connected the exact circuit but it doesn't work as expected!!

This is my video on YouTube explaining the problem:

ua741cn non inverting amplifier problem

==============================================================================
I have another question:

Can I use 12V source and split that by two 10k resistors and supply +6V and -6V to the op amp like this circuit:


texts: STM32 SysTick timer - Doesn't run the alarm event

texts:
I'm attempting to write an interrupt to keep basic time measured in ticks on an STM32F407VGT (Discovery Board.)

My interrupt appears to run once (though I cannot be sure), but it then crashes/locks up the processor completely. All UART output stops...

The code is essentially the same as in "The Definitive Guide to the ARM Cortex-M3, 2nd ed." (Joseph Yiu, Newnes.) Could the fact that the STM32F4xx is an ARM Cortex-M4 be a problem? If so, how do I fix this? I initially tried using TMR2, with similar issues, which makes me think it's something I'm missing. I've also tried using SysTickConfig, with the same problems.

uint32_t ticks;

void SysTickAlarm(void)
{
    SysTick->CTRL = 0;
    SCB->ICSR = SCB->ICSR & 0xFDFFFFFF;
    ticks++;
    return;
}

/*
 * Initialise system timer
 */
void tick_init(void)
{
    ticks = 0;
    *((volatile unsigned int*)(SCB->VTOR + (15 << 2))) = (unsigned int) SysTickAlarm;

    SysTick->CTRL = 0;                  // Disable SysTick
    SysTick->LOAD = TICK_DELAY;         // Delay for 10 ms
    SysTick->VAL = 0;                   // Clear current value to 0
    SysTick->CTRL = 0x7;                // Enable SysTick+exception and use processor clock
}

/*
 * get_ticks: Get the number of ticks since processor initialisation.
 */
uint32_t get_ticks()
{
    return ticks;
}

main() calls tick_init() then starts spitting out printf("ticks=%d\n", get_ticks()); in a loop. But it stops fairly quickly, I get around 10 lines before it crashes.

I'm very new to ARM processors, so it's probably something very simple, but I can't see it.


texts: RaspberryPi + TowardPro MG996R DIGI HI TORQUE +PWM

texts:
I am trying to control this servo from a RaspberryPi.
https://skippy.org.uk/wp-content/uploads/MG996R_Tower-Pro.pdf

I sort of figured out that a servo needs a specific pulse for a specific degree.
www.youtube.com/watch?v=ddlDgUymbxc

I am using this https://github.com/hybridgroup/pi-blaster for PWM.
I already confirmed this PWM works as expected by lighting an LED, but no matter what pulse I give to my servo, it just goes wild.
It goes like either keep moving from left to right or shakes at one point continuously.

The youtube's servo moves +/- 90 degree, but my servo does +/- 60 degree.  so maybe the pulse I need to give is different from 0.5ms/1.5ms/2.5ms?

Has anybody used this servo with RaspberryPi?  What are the pulses to give?

updates

I changed the source code to have 50Hz frequency.

diff --git a/pi-blaster.c b/pi-blaster.c
index 2e15ee1..d7d8af2 100644
--- a/pi-blaster.c
+++ b/pi-blaster.c
@@ -70,8 +70,8 @@ static uint8_t pin2gpio[8];
 // will use too much memory bandwidth.  10us is a good value, though you
 // might be ok setting it as low as 2us.

-#define CYCLE_TIME_US          10000
-#define SAMPLE_US              10
+#define CYCLE_TIME_US          20000
+#define SAMPLE_US              20
 #define NUM_SAMPLES            (CYCLE_TIME_US/SAMPLE_US)
 #define NUM_CBS                        (NUM_SAMPLES*2)

and now pi-blaster shows this.

$ sudo /usr/sbin/pi-blaster
Using hardware:                   PWM
Number of channels:                 9
PWM frequency:                  50 Hz
PWM steps:                       1000
Maximum period (100  %):      20000us
Minimum period (0.100%):         20us

but my servo still goes wild.  Since Minimum period (0.100%): 20us, to have 0.5ms, I did this.

0.5ms(500us) / min period(20us) = 25
0.1% * 25 = 2.5% = 0.025

$ echo "17=0.025" > /dev/pi-blaster

It seems it is always going back to 0 degree point whichever the % I give it to.

It goes like this.
For 180 degree, it is 2.5ms.  When I give

$ echo "17=0.125" > /dev/pi-blaster

servo goes to the 180 degree point, and it soon goes back to 0 degree point.  It goes like this back and forth, back and forth, as long as I give the power to it.  same goes to any degree.

why?


texts: What it means when we say that some component or device is inductive or capacitive? How these terms are related to capacitors and inductors?


texts: Transistors: Switching a higher voltage at the source (not the drain) side

texts:
TL;DR: I want to use a lower voltage (5V) to switch current from a higher (12V) voltage source at the source end instead of the drain end.

Longer story: I'm trying to control some large seven-segment displays with an Arduino by multiplexing across the digits. This presents a few design considerations:

Vf on the segments is 8V-10V (because each segment is actually 5 LEDs in series), so I'm going to drive them with 12V.
The displays are common-anode, so control of the segments happens at the cathode/drain, but control of the digits happens at the anode/source
The multiplexing will be such that all segments of an individual digit will be lit at once, and then we will switch to another digit. So, we have to allow for multiple drains to be open at once, but not for multiple sources.

There are many other posts asking for controlling higher voltages with lower, but the ones that I found all advise to put the load in the collector of a BJT. Indeed, this is what I've done at the drain side, to control the segments, but I also need to control the supply to the common anode of each digit.

The simplest way I've found is to use a PNP/NPN pair (Q1_1 and Q1_2 control digit 1, Q2_1 and Q2_2 control digit 2), but this seems like overkill. I feel like this can be done with only one transistor per anode (but maybe with more total components... resistors, capacitors, etc).

Here are the questions I have about this circuit (note: I only included 3 LED's per digit, for simplicity):

Primary question: Is this PNP/NPN pairing a sensible way of doing it, or is there a more-standard way?
Secondary question: Note that both of the transistor pairs share the same emitter resistor (since only one is enabled at any one time). I suspect that this prevents the NPN from getting to saturation since that resistor would pull the NPN's emitter voltage up above 5V. My solution for this would be to move the resistor to be between the PNP's base and NPN's collector, but this would require one resistor per digit (which isn't a big deal here, but, for a larger project, it could be, and I'm curious if there's a way to get away with just a common resistor). Is is just a matter of setting that resistor to a lower value so that the PNP can, at least, saturate?


texts: Is it safe to use a soldering gun when attempting solder repairs to a PCB with IC chips and other processing units?

texts:
I have a laptop that needs to have a part repaired. I have a roughly 20 or 30 watt soldering iron, but it seems to take so long just to melt the solder onto the eyelet. Holding it there for so long causes me to wonder if I might be damaging sensitive components nearby.

So I got this idea. A soldering gun heats and cools very quickly, which means I can apply the tip to the eyelet, put the solder onto the eyelet, or whatever metal contact I have to apply solder too, and then compress the switch to turn on the heat. It heats up pretty quickly, so it'll melt the solder, and once that is done, I can immediately remove the soldering gun tip and solder string, allowing the gun's tip to cool before applying solder to the next part.

I was in Job Corps, and I did electrical assembly. I had chosen to build one of those hobbyist electronics assembly multimeter kits as the part to the class, however, it didn't work properly, and I couldn't figure out what I did wrong. My conclusion was that I must have damaged the IC chip when applying solder. I probably applied the iron for too long to the eyelet in order to melt the solder to it.

Since then, this has always been a problem. I have to apply the soldering iron for several seconds just to get the solder to melt onto the eyelet. By that time, I fear I am destroying components. I know, I could try and melt the solder onto the iron, and let it flow onto the eyelet that way, but I distinctly remember reading that that is the wrong way. The solder must melt onto the contact in order to ensure proper melding with the contact metal.

This is why I thought the gun my help me. It will surely allow the solder to melt rather rapidly, and I can remove it as soon as the solder has melted. It should be far quicker than a soldering iron.

Feel free to make recommendations, as I am not by any means skilled nor experienced in soldering components.

However, my primary question that I'd like answered is whether a soldering gun is safe using it in the manner that I have illustrated above. BTW, the PCB is a laptop motherboard in which the CR 2032 battery housing has become detached from the contacts, and I must reattach it after drawing a new metal lead with a PCB pen.


texts: Precision mini winch (with position feedback) for kinetic lighting?

texts:
I am trying to create a kinetic lighting installation for my home, above the dining table (see example here https://www.youtube.com/watch?v=-DZ18DNbjTQ ). Obviously I will use max around 20 lights.

The solutions I have found either cost above 100K (!) or are based to huge, theatrical stage oriented fixtures from China.

So I have decided to attempt to create such a system by myself (with the help of an experienced friend).

The first thing I would need is a DC servo motor / winch which would give some form of position feedback (so that I can keep the lights in sync) or even better a winch that will allow me to roll down the light by 20 cm or to a specific position and do it accurately. The whole idea is to have a system where I will be able to set the position of each light with ease and accuracy. The weight of the light will be slow - in essence a led strip within a 15 cm glass bowl.

Any ideas where I could find parts that could help me implement this? I am open to any control methodology - e.g. dmx, custom arduino control etc.

Many thanks!

ORBIS-FLY - the inspiration:


texts: LM388 (or LM317) Torque (current) limiting motor driver

texts:
I am designing a small handheld electronic screwdriver for a university project. The motor in this screwdriver requires a torque limiter to stop it stripping screws out of plastic parts and i am currently looking to use an LM338 to do this, hoping to use as few components as possible to keep size and complexity down (atleast for V1).
I was going to do it similar to the specification sheet as seen here:

However, this clearly has some issues! 1, my motor can pull 1.45A of current and my small 100ohm potentiometers can not and 2, this also creates a varing potential divider between the LM388 and the motor, slowing the motor down. I just want the motor to be torque limited, not speed limited.
This lead me to a design like this:

However I have not been able to get this working using R1 - 1k ohm, R2 10ohm.
The 1km was calulated as shown here:

The 10 ohm is just to prevent shorts and therefore small.
Would anyone be able to give me a hand who has experience with this?
The only other info should probably mention is the motor, which is this:
https://www.servocity.com/81-rpm-mini-econ-gear-motor/
and has a static resistance of 9ohms (I think).
The datasheet for the LM388 is here:
https://www.ti.com/lit/ds/symlink/lm338.pdf


texts: Power Distribution for multiple 5V consumers

texts:
I'm a newby in the field of Electrical Engineering (only basic knowledge from school).
Nevertheless, I need to power up to 10 Raspberry Pis (5V, 2A) with Dupont Connectors and AWG24 cables over GPIO header.
I have a power supply unit giving me max 30A at 5V.

My question is, can I just etch e.g. two lanes on a PCB and solder a Dupont header (10 by 2) with 10 output pairs (each for one device) to them and powering those lanes at the end with one input pair coming from the psu (with stronger wire gauges, maybe AWG18)? Of course I would apply solder masking, to prevent short circuits and oxidation.

This seems a bit naive, so I'm asking your opinion. Maybe you are aware of other neat solutions?


texts:
When I learned phasors I learned we passed from sinusoidal to phasor this way:

$$\sqrt{2} V\cos(\omega t+\phi) \rightarrow \sqrt{2} Ve^{j\phi}$$

However I'm now studying for a book that does this:

$$\sqrt{2} V\sin(\omega t+\phi) \rightarrow Ve^{j\phi}$$

Is this some kind of notation that I am not familiar with? Can I accept this as correct? I«m facing this notation studying three-phase systems, while the first notation was used in the context of circuit analysis.

Thank you!


texts:
I'm looking to extend two USB 2 devices with one 5 meter long cable.
From what I've read, one can run USB 2 fine over Cat5e cable (as long as it's <5m).
My question is whether it really matters if the cable is Cat5e or regular Cat5. I couldn't find much on the matter.

Also, I take it doesn't matter if I power both devices from a single USB power line (saving me 2 lines from the ethernet cable).

Running two USB cables over one ethernet line saves me from having an ondevice powered USB hub (lighter) and having two USB cables running next to each other.


texts: Hold-On-Hold-Off Soft Latch Power Switch Circuit

texts:
I'm trying to make a "hold-on-hold-off" type soft latch switch circuit, but I'm having a little trouble. I've found tons of "press-on-hold-off" types, but I haven't been able to find a single example of a "hold-on" type anywhere.
I found/have been experimenting with this example "press-on-hold-off" circuit, and have a working model in falstad circuit simulator:

I was wondering if there was a simple way to modify it to work as a hold-on type. I thought maybe another capacitor could be added at the switch to act as a "debounce", making it take longer to turn on, but that hasn't worked in the simulator, so I'm not sure if I'm just misunderstanding how the circuit works, or if my idea is just wrong.
Any thoughts or wisdom would be appreciated, thanks for taking the time to read!


texts: VHDL state machine using different clocks

texts: I have a state machine inside a process. I want to base the process on two different clocks. Is it possible to use clock1 to clock state1 and clock2 to clock state2?


texts: At what range can I transmit with this antenna?

texts:
I would like to transmit data at 125 kHz frequency. I'm wondering what is the realistical transmission distance that can be achieved with this antenna:
It's a rectangle shaped 9x12cm coil antenna.
Transmitter frequency: 125kHz
Inductance: 1.04mH
Resistance: 15ohms
(https://www.electrokit.com/en/product/rfid-antenna-9x12cm-125khz/)
In the description it says 'long-range'. I understand that LF transmissions usually take place in centimeter/millimeter measured distances, so I'm not sure what is meant by 'long-range'.
I'll be using Arduino to drive the antenna for now, and I'm wondering how far I can transmit signal/data and what can be done to increase the LF transmission distance?
I’m looking to transmit at about 1 meter range*


texts: How to calculate voltage drop across multiple wire gauges?

texts:
This seems like a googleable question, but I simply cannot come across anything.

I'm working on a 12v system (aluminum boat), trying to supply power to a motor 12ft away from the circuit breaker.  Through online sources, I was able to determine that at the 45amp max, 6awg wire could handle it, with a 5% voltage drop.

The confusion enters when I try to calculate the voltage drop with this 6awg wire, plus the potentially 8awg wire that runs 1.5 feet from the battery to the circuit breaker.

How does one correctly calculate the voltage drop over two different gauged pieces of wire?


texts: How to interpret data sheet for an RF 50 Ohm terminator, is it 2 Watt or is it 0.1 Watt

texts:
I am trying to find a suitable RF 50 Ohm terminator for my application. I think the following will work:

http://www.amphenolrf.com/media/downloads/7034/132360.pdf

I am a little uncertain though as it states in the "Electrical" section that the impedance is 50 Ohms, the frequency range is 0-18 Ghz and the power rating is 2 Watt. This all fits with in my parameters.

However it has a "Material and Finishes" section and it lists resistance as 100 Ohms and 0.1 Watt. Should I be concerned with this section of the data sheet, is it telling me that really it can only handle 0.1 Watt and 2 Watt is only peak power as opposed to continuous operation? Which if so would put it outside my applications parameters.


texts: Combinational circuit to check if two four bit numbers are equal

texts:
Right now, I've got:

(x1 and y1)
(x2 and y2)
(x3 and y3)
(x4 and y4)

So the outputs from these gates will give me 1 when the bits from both numbers are the same. The issue here is that I will get positive results when they are the same and when each bit is different from each other bit (because 0,0 will still give a 1 in an and gate).

I'm probably missing something very obvious here.
Thanks


texts: Reading an LDR array with a Raspberry Pi

texts:
I am trying to repurpose a replica GPO 746 using a Raspberry Pi, however the rotary mechanism is rather different to that in an original 746. The circuit has 12 LDRs arranged in an array (3 columns, 4 rows), a shutter attached to the dial, and an LED above the shutter. The shutter is arranged so that when the dial is rotated, a single LDR is illuminated by the LED. The finger stop incorporates a microswitch which powers the LED. I've included a rough circuit diagram below.

The row and column wires were previously connected to an HM9102D, however I cannot reliably replicate the setup using a Raspberry Pi. Reading the GPIO pins via multiplexing seems to have inputs triggered at random, even when the LED is off.

How can I reliably read the inputs from the dial?

simulate this circuit – Schematic created using CircuitLab


texts: High current drawn by 3 phase 90 KW Induction Motor during the last part of batch mixing in a toilet soap making factory.

texts:
I am currently dealing with a problem of high current drawn by a 90KW three phase induction motor towards the end of the batch mixing process for a toilet soap factory. The no load current is around 50Amps (which is 33% of the rated current : 156Amps). I have also reduced the batch size to reduce the mechanical load. But the motor is still drawing high current towards the end.
Kindly pour in some suggestions that what might be the possible reason.


texts: Should a freewheeling (flyback) diode be used on the coil of a 2-coil latching relay?

texts:
In an automotive 12VDC application, I want to use a pair of 2-coil latching DPDT relays such as Panasonic TXS2-L2-12V (https://www.panasonic-electric-works.com/pew/eu/downloads/ds_61022_en_txs.pdf), and connect the Set coils in parallel and the Reset coils in parallel, such as is shown in Figure 16a and 16b of Panasonic's "Relays Caution for Use" note (https://www3.panasonic.biz/ac/e/control/relay/cautions_use/).

In that note, when the coils are connected in parallel, they recommend placing a diode in series with each of the Set and Reset coils as shown in those Figures.

Question #1 is:  Should I also place a coil suppression rectifying diode (e.g., 1N4007 or similar) in parallel with each of the Set and Reset coils?

This posting, while not concerning the connection of the Set and Reset coils in parallel, does suggest using a rectifying diode across each of the Set and Reset coils: How to protect bistable latching 2 coil relay with diodes?

Question #2: I plan to activate the Set and Reset coils via a manual SPDT momentary (On) toggle switch.  Coils will be 12VDC. I plan to put the switch on the ground side of the coils (between the coil series diodes and ground).  The relay data sheets I've read say that subsequent latching pulses after the first pulse on either the Set or Reset coil have no effect, so is it reasonable to expect things to work OK with a non-debounced, manual SPDT switch controlling the coils?

Thanks,
Doug


texts:
I bought an inexpensive battery-operated door alarm that works using a reed switch and sounds a small buzzer when triggered.

To beef it up, I'd like to swap in a louder separate siren/strobe light to replace the buzzer. The new siren operates at the same voltage, but I'd imagine it draws a lot more current.

Can I simply swap it in if I also replace the batteries with a power adapter capable of handling the new siren's current requirements?


texts:
The circuit below supplies 3.3V to an antenna (3.3VGreen), which then gives GNSS info to a control module (ANT_GNSS). The attached antenna is datasheet and only consumes about 10mA

I'd like to be able to switch the antenna on and off to preserve power, as this application uses a battery.  So I thought the circuit below would accomplish this.

But I am wondering what resistor value I need at the BJT's base to bring the transistor to saturation?  The transistor's datasheet is linked here datasheet.  I am thinking that if h_fe is 100 @10mA (collector current) then base current needs to be at least 10mA/100 or 0.1mA to drive to saturation?  Following this BJT Tutorial, but I have no practical experience.


texts: JFET - transconductance, gain(mu) and internal resistance at the drain

texts:
Hello guys, here is such assignment: to determine gm, internal resistance at the drain and maximum gain (mu).

1) If Transconductance gm can be found from the formulas and graph.
2) How to determine graphically internal resistance a the drain? as I understand it is r'ds = delta V(DS)/delta I(D).
How to determine from the graph the delta V(DS)?
3)  in the end it is: A(v) = gm*r'ds. But how to determine mu with the given data?

Thanks in advance!


texts: To my understanding the thevenin voltage is the potential difference between a fixed circuit and the ends in which we can add a load. I am going in circles with this problem. I was able to find the thevenin resistance, but it's the thevenin voltage I am having problems with. I applied KVL to the circuit thrice (inner 2 loops and the outer loop) and I get equations that cancel each other out. Can anyone do a quick help on this problem of mine?


texts:
I'm looking for a connector. Ideally it would be a one pin connector mounted on the back side of a board and the pin would come through the board into connector.

Here's an illustration:

Does such a thing exist? And if so what's its name and where can I buy one (or actually about a hundred).


texts:
Googling this hasn't given me much information. I've heard numbers ranging from 30A to 300A.

My question isn't how many amps a car battery does supply in normal operation, it's how many amps I would measure if a car battery is shorted across a multimeter (assuming the multimeter doesn't explode).


texts: Outsourcing chips manufacture; do they get pirated?

texts: When Intel or Apple outsources their electronics to Asia, what prevents the outsource vendor from copying the design and making a knock-off product?


texts: Help Identifying Small 4 pin male connector

texts:
I'm trying to identify this connector so I can get an appropriate female connector for it. Its found on a Pico PSU (picoPSU-160-XT) next to the 12v input. There are 2 different ones on opposite corners. Mine is about 4 years old so it may be different than newer ones.

The dimensions of the connector are 12.5mm x 5.65mm and the pins are spaced 2.5mm apart.

UPDATE: For anyone looking for the female component for this connector, I found this:
Digikey has the components (empty connector & pins), part #'s:

455-2267-ND
455-1135-1-ND

Or you can get this pre-made female connector with pigtails:
JST-XH V2 4 Pin Adapter


texts: Wireless, battery operated web cam for mobile robot

texts: I'm working on a Netduino based mobile robot that's controlled by software on a PC or phone (WP7).  One goal of the project is to be able to steer the robot from another room of the house.  Is there a small wireless (wifi) web cam that runs on battery that may work for this situation?  I don't think the Netduino has enough processing power to stream video, though technially it could using a wifi shield.  If that's out of the question would it be possible to sporatically take pictures using some other camera sensor & the Netduino (photos could be stored on the SD card and later served up over wifi to the client)?


texts: Using NPN transistor as Thermistor emulator

texts:
Premium motherboards (Asus Crosshair Hero VII) have T_in 2pin header for 10k thermistor temperature monitoring. Probing around reveals internal voltage divider with ~12KOhm rTop resistor (as per attached picture).

Goals for sensor read @ T_in:
25C (aka 10K) when GPIO is off or disconnected.
60C+ (aka ~2K) when GPIO is high.

Rough calculations, voltage drop T_in-1 to T_in-2 be ~1V for ~2k rBottom equivalent resistance.

I thought I could use NPN transistor as a simple switch, plus some resistors to act like a programmable parallel resistor network (10k at low, 2k at high). Really its much more complicated.

I don't have exact datasheet, only markings on transistor C945, scavenged parts bin.

I have a background in software engineering but its been a while for transistor logic. I built attached circuit and IT WORKS! 1.08V vCollector to Gnd. Asus reports 68C at GPIO high, and 25C at GPIO low. 10Kohm resistors were chosen mostly because they were convenient in my tickle trunk.

Questions:

I fudged around with the resistors until I got what I wanted.  How would I go about calculating the values?
What if I wanted 60C(~2500ohm) instead of 68C ?
Am I over complicating this / easier circuit to build ?


texts: How to get fine DC brush motor speed regulation?

texts:
I want to get a fine speed regulation of Pittman DC 24 V brushed motor with 10,000 RPM for a hobby project. The voltage I will use is battery 12 V DC, so does that mean the speed will be 5,000 RPM?
I will try to find ready gearbox combination with 400 : 1 ratio because I want to  get around 12.5 RPM at the shaft.  The load will be pretty constant during the use of the motor. Motor will work continuously just rotating the load at very slow speed, so in several  hours the load will only rotate 90 degrees. Mow I want to FINE control the speed of this gearmotor with PWM around 0.0133 RPM! Is this  possible to achieve at all and is this possible to achieve with PWM?
I never did any electronic project in my life, so here my knowledge stops. From reading the internet, I suppose I need to use PWM. How I will regulate the speed with the PWM? Does PWM offer some sort of potentiometer or something else?
I see PWM images on Amazon and I can only see input and output connectors. I don't want to regulate and command the PWM with a computer or something similar to computer or computer program or something complex, just as simple as possible, just PWM and I suppose potentiometer.
If using a potentiometer, it is obviously that regulation needs to be logarithmic, because I want a lot of potentiometer movement around 0.0133 speed let's say 0.010 - 0.015 RPM, and a bit at 0.10 and not at all at 1 and 10 RPM. But I want also to push the potentiometer or whatever will regulate the speed to maximum from time to time, let's say every 10 or 15 minutes so to use that maximum speed at the shaft of 12.5 RPM. That maximum  speed can be 10 or 15 RPM, it is not at all important. I just want this maximum speed to be also available for several seconds or a minute, nothing else.


texts: how to find thevenin equivalent of this circuit via source transformation?

texts:
I can understand how it is done on the left side(150/5k and then 5k||20k then 4k*150/5k and then 4k+4k) but I just cannot figure out how to do it on the right side.

Can you please help?


texts: Making a Darlington transistor (eg: TIP120) with D882 to drive 12V LEDs with 3.3V or 5V input RPi

texts:
I am getting into circuits and trying to improve my knowledge but even though it might sound like a silly question but here is my story short:
What I am trying to do
I am building a circuit to drive an LED strip (12v) out of a Raspberry Pi using PWM output.
It worked out perfectly using a TIP120 on the breadboard using the following example:

My goals
Now that it is working, I am building a PCB to send to JLCPB to have it printed and assembled so I wish to use basic parts as much as possible and ended up selecting a D882 transistor which is not a Darlington.  I heard that it might cause issues to my actual circuit and not expecting the same result as with the TIP120.
So a using D882 transistor I kind of recreated the schematic of the TIP120.
Am I silly to say that this will do the same thing as the TIP120?

Am I in the wrong way and another SMD component would do the trick?
Update
Channel 1 at 100%, seem to get alot of noise but Channel 2 at 50% is quite stable.

Here you can see the quick simple prototype


texts: Why are bipolar transistors used for switching applications?

texts:
I noticed that many sites targeted at hobbyists recommend bipolar transistors (mostly NPN) to switch things on and off. Bipolar transistors definitely have their purposes especially in analog circuits, but if you want to switch a relay for example, a MOSFET is a lot easier to work with a lot less downsides.
They can easily switch many amps of current without requiring current themselves.
They (almost) don't drop voltage across source and drain which means they won't get hot even at high currents and they are as cheap as bipolar transistors.
Are there any pros to using bipolar transistors in switching applications I am overseeing?
UPDATE:

The sites I was talking about where Adafruit and similar sites.
I never really looked into THT parts since I only work with SMD parts at work. I just checked Digi-Key and although they have very good and cheap SMD FETs their selection of THT FETs is very limited much more expensive and with higher drive voltages... I suppose THT FETs are commercially only used to drive really high currents.
Summarized you could say that since hobbyists are normally limited to THT, suitable BJTs are more easily accessible and a little less sensitive to ESD while tinkering.
Basically I just wanted to know if I was missing something and should use BJTs over FETs at work in some cases.


texts: Different bus representations on schematics?

texts:
Here is an excerpt from a sample "data flow" diagram:

Now both lines in both circles represent buses but in #2, there is no bus arrow that goes to the IC.

What is the difference between them? Does #2 means that this IC never reads from that bus but only outputs to it, whereas #1 means this IC both reads from and writes to this bus?

If that's the case, what about if we wanted to represent: "This IC only reads from that bus but never outputs to it." How would we represent that?


texts:
I am hoping I am doing something dumb here. I know there are other posts about this but everything I have found leads me to believe my circuit should be working. Yes this is for homework. No, I am not looking for "here's the file so you can cheat. I feel either I my BCD converter is not working properly or I have my switches set up incorrectly.

Construct a 4 bit 2’s complement adder circuit using discrete
components (and, or, xor etc)
Display the result on 2 seven segment displays, one for sign and one for number
If the number if positive, use BCD to seven segment to display output
If the number is negative, invert every signal, use another 4 bit adder and add a one, then use a BCD to seven segment to display output
Describe operation of the circuit. Capture output of seven segment for max, min and in between values.

I have attached my schematic and truth table. I will also post my circuit in the comments. Any nudge would be greatly appreciated.


texts: I replicated the schematic of a cheap LED strip that I bought. Can someone explain me what does the transistors do in that circuit? It has a input voltage of 12 volts.


texts: Odd reading when replacing an LED with a voltmeter on a PNP's collector

texts:
I am using a simple circuit to drive a 12V LED with Arduino. I have used this circuit successfully in past. I am using NPN-PNP combination to drive a load which needs more Voltage than Arduino's HIGH voltage (i.e. 5V). Today, I noticed that my voltmeter reads 10.2V on Arduino LOW and 12V on Arduino HIGH OUTPUT. I had no load attached to it when I measured the behavior. Well, it serves my purpose when I put the LED in place of voltmeter - since the LED has a forward voltage of 12V, it turns ON and OFF with Arduino HIGH and LOW signal.

But, my question is why do I see 10.2V when Arduino output is LOW? I am a newbie. So may be I am expecting something wrong. Shouldn't I get 0V when Arduino is LOW? Or is this switch only good for Controlling Current, not Voltage? Or is it because I was measuring the Collector Voltage with No-Load attached?

simulate this circuit – Schematic created using CircuitLab


texts:
I have an Arduino that I am running two DC motors off of. I have the L298N motor shield that I am using to power the motors. Now that I have the system hooked up and running, I want to add the next step.

My end goal is that I want to create a robotic 'arm' of sorts and write some code that can move the different 'joints' independently. I just want to be able to code an action directly so I don't need functionality where I manually control the movements.

I've been trying to find DC motor 'attachments' or 'heads' that I can build on top of the motor so when it spins, it will move the piece but I can't seem to find anything that fits the little DC motors (some of the heads are for Servo motors). I'm really attempting to build this from scratch so I'm trying not to use any 'kits' and am trying to learn about the different components that would go into building this. Everything I find seems to point me towards a kit or something which sort of defeats the purpose of building it from scratch.

Are DC motors ok for this or should I be looking into something like a servo motor?

Also, I'm aware there is a robotics stack exchange forum but this seems to fall under this a little better because I'm basically just trying to get an idea of what kinds of attachments can go with a DC motor and what exactly I can be using them for.

Thanks for your help!


texts: Can I use polarized capacitors in a location where they shouldn't be polarized?

texts:
I've been in the process of restoring a jukebox. Recently I figured out that the junction box, which holds quite a bit of resistors fuses and capacitors, has three large capacitors from the 60-ies... Needless to say they have to be replaced with more recent ones.

They are:

50 WVDC 100 MFD wurlitzer part no. 73862

50 VDC 500 MFD wurlitzer part no. 71816

400 VDC 0.5 MFD wurlitzer part no. 73099-140

This replacement thing however has prooven to be quite the challenge.

I have bought the replacement capacitors which are on their way, however I overlooked an important bit...
According to the schematic drawing (see attachment below) only one capacitor has to be polarized, the other two simply have the icon for capacitor with their respective values.

Yet two (possibly three) capacitors that are currently inside the jukebox are polarized, and I bought the replacements based upon their values.

The 50 WVDC 100 MFD (paper), also has plus signs next to the word AMCON,
The 50 VDC 500 MFD (yellow), carries plus signs, and a ribbon,
The 400 V 0.5mfd (wax) has a ribbon, I assume this is negative.

Any thoughts on polarity, replacements and my original question if polarized caps can be used in these locations, are very welcome :)

I've attached a complete schematic and pictures of the current caps in place below:

Currently the 50 WVDC 100 MFD cap that is in place looks like this:

Currently the 50 VDC 500 MFD cap that is in place looks like this:

Currently the 400 VDC 0.5 MFD cap that is in place looks like this:

The electrical schematic:


texts: Should RF output of (30+j10) Ohms be matched to 50Ohms for antenna matching network?

texts:
I'm designing a matching network for a 2.4GHz inverted F antenna. I am using an ESP32-D0WDQ6 MCU, and reading from the datasheet, the output impedance for the RF pins is (30+j10) Ohms. (DATASHEET in section 2.5 on page 7)
Should the matching network be set to 50 Ohms? Or should it be set at (30+j10) Ohms?
EDIT: anyone reading this should read the further comments with Andy AKA's answer for completeness.


texts:
Given a device that incorporates an embedded processor (MIPS), MMU, small RAM and larger flash memory, is there an RTOS with small memory footprint that has a built in support for "virtual memory", where some RAM can be used as a cache for the larger flash memory?
(This implies a non-flat memory model, where page faults trigger an interrupt that performs the page swap)

Thanks


texts:
How do I find the value of VT and RT such that TS will be VCC/2 at 40 deg Celsius?

Datasheet link.


texts:
I have been forced to use only the lm358 as my op-amp choice for an electronics project. I have tried setting up a simple inverting pre-amp..using a 10k and 30k resistor. i am feeding a stable 9v to the op-amp.

It is incredibly distorted! Whatever song/sound i feed to it becomes incredibly distorted. my input signal is set as 5v.

What can I do to reduce the distortion? Btw, when nothing is playing in the sound input, there is no noise so it is clean signal to begin with..