texts: Wired MBus Design - Circuit and Communication

texts:
Been working putting a wired Mbus circuit for a while now for both the master and the slave.

For the slave, I am using the ON Semi NCN5150 Slave Chip and built the circuit just as the development board - NCN5150SOICGEVB.

I also have another MBus slave device (used to communicate with energy meters) and its working fine. This is just to test my master circuit. So we call this "Meter test Slave".

For the master, I got this attached Circuit from the MBus UA Website.

I also got this master circuit from a forum

For the slave circuit, everything seems to look good, and well as for the master. I am getting the required voltage for the Bus, and my slave device is powered on. Where I am yet to get an headway is with communication.

When testing, this is what i observed,

I connect my master circuit to the "meter test slave" and it powers on the slave. As this slave was programmed, it ought to send some configuration code for handshaking with a master once connected. My master received this information, and I view this Hex value on a Serial Terminal (1 start bit, 8 data bits, even parity, and 1 stop bit). So i can at least conclude that my master receives information. And this happens to both circuit above.

However, I can not test that the master transmits any information because I do not yet know data the slaves expects.

For the slave circuit i built, I observed a different thing. Yes! The bus master also powers the slave but communication does not look successful. Connecting both ends of the master and slave to separate serial terminal, I observed that when I send a string of information to the master, I get the information back on the slave serial terminal and not on the master terminal. Its like an echo as what i send out is coming back. And this only happens when the Mbus link is connected. And again this happens for both master circuit i built.

I need to know if I am doing something wrong here. How do I get this to work?

TEST UPDATE:
I observed that the Echo response was expected according to the datasheet of the  NCN5150. Its states that "Because the M-BUS protocol is specified as half-duplex, an echo function will cause the transmitted signal on RX or RXI to appear on the receiver outputs TX and TXI. Should the master attempt to send at the same time, the bitwise added signal of both sources will appear on these pins, resulting in invalid data".

Also I tested the "Meter test slave", and I observed that the echo also occurred on the receive line.

So i guess i need help as to why the information is not getting to the Master UART interface.


texts: Hall Effect Flow sensor output characteristic

texts:
The cheap and convenient hall effect liquid flow sensors available for a few bucks online nearly all cite the device output as being a square pulse train whose frequency is a linear function of the flow rate.

My application is a water flow indicator. No measurement of flow rate, no microprocessors needed - just an output that indicates whether water is flowing or not flowing.

All the devices have a hall sensor and a pinwheel and a conditioning/amplifying/shaping circuit internal to the assembly,  but I have not seen anywhere information that says if the output remains high (or low) when flow stops.

If the pinwheel magnet(s) are aligned away from the hall effect sensor when rotation stops then I would expect the output to go to logical 0. But what happens if the wheel stops when the magnet is aligned with the sensor? Does the output now stay high, or is the internal circuitry such that there has to be changing flux for there to be any pulse train at all, and there is a defined state for "zero flow"?

Anyone know from experience before I start breadboarding and prodding the pinwheel?

Thanks


texts: How to optimze a coil for needed voltage?

texts:
Faraday's law for a coil is :

V = A * M * N

Where:
V = Peak output-voltage
A = Area of the cross-section of the wire
M = Rate of change of magnetic flux in the coil
N = Number of turns of the coil

Question:

Whats happens when A gets very small and N very large?
I expect that in that case internal resistance gets higher and the output voltage drops??

If that's true, there will be a certain combination of A and N that will
be optimal for a needed V. Question: How to obtain this A and N ?

NB: By optimal I mean minimal space needed by the coil and minimal material costs for the wire.

edit: The coil is used as a generator like in a bike dynamo. So the coil is wound around a linear weak-iron core.


texts: Seven-segment display seems to draw little current

texts:
I bought a 1.8-inch seven-segment common cathode LED display from AliExpress. So no datasheet available.

I used a 1 kΩ resistor and a 5 V source, as to put a max 5 mA in the LED. I measured 1.6 V for the decimal dot, and 3.5 V for each segment. The measured current draw for one segment was 1.5 mA.

Now, I expected each LED to be quite dim at 1.5 mA, but it was the opposite, I could put a 4 kΩ resistor and still has a usable display.

I intended to drive the display using an ATmega328P and a MAX7219 (which would have been OK up to 500 mA per segment).

Does this measurement seem correct, and if so, I can drop the MAX7219 and drive the segment directly (with current limiting resistors) with the ATmega?


texts: Output Resistance of Small-Signal MOSFET Circuit

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I have some doubts concerning the calculation of the small-signal output resistance of a common-source stage with source-degeneration. This is related to another question I posted but I have refined my question in detail here as to exactly what is troubling me
The Problem
Calculate the small-signal output resistance of the following circuit including the effect of channel-length modulation and ignoring the body effect.

My Solution
I have two approaches to find the output small-signal resistance, they both involve,

Drawing the small-signal model of the circuit
Zero all independent sources (voltage sources = short, current sources = opens)
Applying a voltage Vx at the output and measure the resulting current Ix flowing.
Output resistance will then be Rout = Vx/Ix

This gives us the following circuit

Now from here on, I have two approaches - the first approach gives me the correct answer, however the second approach gives me an incorrect answer.
Approach 1 (KVL)

Approach 2 (Resistors)

Why does my second approach give me an incorrect answer? I suspect it is something to do with the fact that the ro now only gets a current Ix flowing through it.? Something that didn't sit well with me in the second approach was that after decomposing the current source into a resistor, I had to get rid of the negative sign of the 1/gm. So current flow direction is strange to me too.
EDIT:
Extra Info for Comments:


texts: Minimalist high speed 8051 microcontroller testing circuit on breadboard

texts:
I'm trying to come up with a circuit using the least number of parts possible to build on a breadboard that tests the basic functionality of a microcontroller, specifically the AT89LP4052 microcontroller.

This is what I have so far:

I omitted the coupling capacitors from the crystal because the speed I'm using is low and I think breadboards add capacitance.

I attempted to load the following hex data into the micro (so I think):

75h 90h 01h
   75h 90h 02h
   75h 90h 03h
   ...
   75h 90h 1Fh

What each line does is set the value of port 1 to the last value in the line. If programmed correctly, I should see at least both LED's blink at a high rate but none of them turn on, not even partially.

The interesting thing is when I was programming it, the micro had 12V on the reset line before any action, then I resetted everything and followed all op-codes as per instructions in the datasheet.

So before I can predict that the data entered into the micro is officially incorrect, is the circuit above good enough for minimal part count for proper testing to begin? or will I need to resort to adding a super low-speed oscillator (of say 2hz)?


texts:
Possible Duplicate:
  How can I detect if a garage door is opened or closed?

I'm planning to make something to detect if our garage doors are opened or closed. We have a server where I'm going to program a software which I can use to read the doors' status. I think the best way to do this is to use reed relays. But the problem is, how can I transfer the status of the doors from the relays to the server? How can our server detect if the doors are closed or opened?

I'm really a beginner, so I need very detailed information. Thanks.


texts: Any tricks to attaching a wire or pin to a testpoint?

texts:
More and more often, I find myself needing to tear apart a device to seek out and connect to serial pads. These pads typically give me access to the underlying operating system for research or tinkering, of which I'm perfectly comfortable with.

What I'm not comfortable with, though, is making the necessary hardware connections. That is, while I own soldering tools, I'm deathly afraid of using them. As a software guy, I really just want to get in, look at some bits, and get out, without any lasting damage.

Are there some tricks of the trade to attaching pins/wires to a testpoint or non-throughole pad without solder for short-term use? Perhaps a wire with a flat conductive circular tip that would yield nicely to, say, tape or hot glue?

Example pad site:


texts: Ways to connect Arduino / Microcontroller to the Web?

texts: What are the best ways to connect an Arduino or a microcontroller (PIC...) to Internet/Web. I would like to be able to send and recieve information from the Arduino/PIC to the Web and vice-verse even if there is no WiFi around. Maybe connecting to my phone using Bluetooth and using it's internet data (3G) is a good idea? What I am trying to achieve is Google Search and response from the results using Arduino, everywhere. (Carrying my phone with the 3G around is not a problem since I don't think it's a good idea to connect to the radio cells around and probably illegally get information from the internet? Any suggestions will be helpful.


texts: Can you use lower GBWP op amps for a filter requiring a higher GBWP by cascading op amps to get a higher bandwidth?

texts:
I was watching this youtube video EEVblog video on cascading op amps for increased bandwidth , and I was wondering if this can be used for 2-pole filters, including filters that are made up of multiple 2 pole filters?
Most 2-pole active filters are made using a single op amp , so for example if I want to use the standard 1 Mhz GBWP op amp , and I am making a 2-pole filter , that requires a GBWP of more than 1 Mhz, can I just cascade multiple op amps together until I get the required GBWP needed?


texts: QFN VS MSOP- Which is better for thermal performance

texts: I am having to decide between a MSOP package and a QFN package for a Buck controller that I am designing in. The Part number is LTC3603. The MSOP is called an eMSOP. I cant locate any further information on what is the difference between MSOP and eMSOP. What are some of the pros and cons of each package. Right off the bat the big flip side of using a QFN is the lack of ease for rework. A MSOP is leaded and hence can be replaced easily without a hot air rework station.


texts: Momentary Bosch Style Relay with Changeover

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I know this is probably really common electrical engineering knowledge, but I am not an electrical engineer so I am quite lost on this.

I have a 2004 BMW and the fog lights work something like this: They start off, and when I press the fog light button, it is a momentary switch that then turns them off.  They then turn off when I press the switch again, or high beams come on, or the lights are turned off.

Here is a really crude diagram I found online. (Ignore rear fog lights as I have none)

Also then here is a link to the actual relay which also has a quite sort of diagram.

http://www.realoem.com/bmw/enUS/showparts?id=BL93-USA-01-2004-E46-BMW-M3&diagId=61_3358

Ok, now on to my question or a couple of questions.  Am I right to assume that this is some sort of latching relay?  Essentially when 12v is applied between pins 85 and 86 it energizes closes the switch from 30 to 87 and completes its circuit.  But since the fog light switch is only momentary, it essentially latches the relay between the 30 and 87 pins until 12v is again applied between pins 85 and 86 OR power to pin 30 disappears (this would be why when you turn the headlights off or high beams on the fog lights turn off)???

A next question I have is, is there a Bosch style relay like this that is a changeover relay. To explain, instead of either switching on and off the switch from 30 to 87, switch between either 30 and 87 or 30 and 87a?  I am having a hard time finding a relay that does what I am looking for.  It is possible it does not exist.  In that case is there a combination of relays or wiring that I could do to achieve this effect?


texts: Oscillators with different configurations

texts:
I'm looking at the following two circuits:

circuit 1:

and circuit 2:

Both of these circuits are LC oscillators, the thing is that the first one, i.e the one with two inductors and one capacitor, converges nicely to a steady sine wave whereas the second circuit doesn't converge at all, it instead dies out after a few oscillations. This is what I don't understand too well... Both of the circuits run at the same frequency, have the same Q factor (I've added some internal resistance), same feedback mechanism..etc so it doesn't seem too obvious why only one them works.

I've even tried with different values of inductance and capacitance but end up with the same result, which is that only the circuit with the two inductors and one capacitor works.

So why does this happen? Why is it that the "configuration" on the first circuit works out fine as opposed to that of the second circuit?

Thanks

P.S: I've also tried changing the base resistor's value, but to no avail.


texts: Do electret condenser microphones require phantom power?

texts: I was under the assumption that electret microphone capsules do not require any phantom power an can be connected in the same way dynamic microphone capsules can be, due to the fact that they contain a small permanent static charge built in. I am trying to build a really simple mic to hook up to my computer via the 3.5mm mic jack, and after wiring everything up, it doesn't seem to be working. Is this because there is in fact supposed to be some sort of phantom power circuit, or should I just double and triple check my wiring again?


texts: Can you control the colors of a RGB LED strip with pots?

texts: I'm wondering if it's possible to control the colors in a LED RGB(W) strip without a device such as arduino? Just with electric components with pots for each color? Thanks


texts: Cyclone IV FPGA: How to use nCSO pin (101) as normal I/O pin?

texts:
(I'm new to this -- so sorry if this is a dumb question).

I've got a RZ-EasyFPGA dev board with a built in VGA port.
I want mess around with generating a simple VGA signal.

Dev board pin-out:

I need to assign PIN 101 as hsync within my Verilog module however, I'm running into compiler issues with the pin already being reserved for `ALTERA_nCEO'.

Error (176310): Can't place multiple pins assigned to pin location Pin_101 (IOPAD_X34_Y18_N21)
Info (176311): Pin hsync is assigned to pin location Pin_101 (IOPAD_X34_Y18_N21)
Info (176311): Pin ~ALTERA_nCEO~ is assigned to pin location Pin_101 (IOPAD_X34_Y18_N21)

I've had a look around for solutions & found pin 101 is a 'dual purpose pin'. I've tried to setting it as regular I/O within 'Device & Pin Options' with no luck.


texts: Multiple switches to independently control a light

texts:
I am looking to create a simple circuit to control a couple LED light strips inside a cabinet using two reed switches that turn on the lights if either or both doors is open and the lights to be off if both doors are closed.

Door 1  Door 2  Light
Close   Close   Off
Open    Close   On
Open    Open    On
Close   Open    On

Thank you in advance for any advice or suggestions!


texts:
I am trying to control some ws2811 pixels using the adafruit neopixel library. https://github.com/adafruit/Adafruit_NeoPixel

When I use an arduino uno they work fine but when I import the library and flash the code on udoo nothing lights up. http://www.adafruit.com/products/1426 these are the neopixels that I am using.

I have taken care of the basic things like power and connections. I basically set the exact same setup as in the arduino but they dont seem to light up.

I could post detailed pictures of my setup.

I tried with a basic led on pin13 shown in examples and that seems to light up. But neopixels don't work.

http://forums.adafruit.com/viewtopic.php?f=47&t=40547&p=258419#p258419 The forum from adafruit says the library works with the due and they dont mention anything about the level shifter, I even posted in the forum but no one responded back. If anyone can help me I will be thankful :)


texts: Choosing the right FET to switch between two sources

texts:
The circuit below is based on the answer to this  question, which i find to be suitable for my application.

3.3VDC is the main supply for the circuit, with 3.6V 1/2AA battery for backup, as defined by the product requirement. The load is basically three switches which should be powered by the main supply until there is an outage, in which case the battery takes over.

In seletcting the Diode, i picked the panasonic DB3X313N with a Vf of 0.55V, this will drope the 3.3V supply to 2.75V which will still work, as the logic input will detect a high.

For the FET, I choose Infineon-BSS84P-DS , with a Vgs(th) of 1-2V.

The load is basically three switches with 10k pull up resistors, so the currrent draw is minimal.

I would like to ask:

Will this circuit function as expected, i.e. to supply the load from the 3.3V source and only source from the 3.6V battery when the mains source is unavailable.
If so, then is my choice of diode and FET suitable for this circuit, expecially with the FET, as i've not worked with FETs before.


texts:
I have been struggling to get the ground plane to fill in Eagle. Basically I have a very simple schematic, it is just VCC, two LEDs and GND.

Now I went into Eagle, selected draw polygon and drew a polygon over it. I then renamed it to GND to match it as such. Then I click RatsNest and nothing happens.

In all the tutorials this actually filled the GND plane correctly. I don't know why mine does not! I get that I have to put the polygon on the top plane, but how?


texts: IR2110 driven mosfet H-bridge not working properly

texts:
I am using this below H-bridge circuit for wireless power transfer. As seen it uses 555 to generate square wave of 50% duty cycle and adjusted to generate frequency of 140 kHz. Clearly, Driver1's Hin pin in connected to Driver2's Lin pin and vice versa. Let's assume these two junctions are J1=D1_Hin+D2_Lin, and J2=D2_Hin+D1_Lin. If I connect 555 output pin (3) to either J1 or J2 the load (a dc motor) is driven fine with expected behavior, i.e., if J1 is connected to Pin 3 of 555 the motor runs clockwise, and when J2 is connected to Pin 3 of 555 it runs anti-clockwise. Now in the final circuit (see schematic) J1 is connected to pin 3 of 555, and inverted output from CD4049DE (pin 2) is connected to J2. When J1 goes high, J2 should go low, and vice versa causing the oscillation to happen across the load. Ideally at this state the motor should just vibrate and should not run to any direction, or if I connect a LC circuit as load, oscillation would occur in the coil, which is the actual purpose of this circuit.
Now the problem is output 3 of 555 can drive the circuit via J1 or J2, but when I use the inverted output from the inverted chip, it can't drive any side of the mosfet driver.

.

I don't presently have oscilloscope to measure peak to peak voltages of the oscillation but multimeter shows 2.5 at pin 3 of 555, and 1.5 volt at inverter output. The inverter chip is CD4049BE. I think pp voltage would be little bit high, but anyway it seems inverter output would be around 2-3 volt, so ir2110 won't be driven as it needs >3v (got information from here).

Why this is happening?

EDIT
Scope output:
The original circuit gave me 70%-30% duty cycle, never 50-50.

Then I found that setting a Vcc/2 control voltage can give ~50% duty cycle.

input vs Output plot

Driving via J1 means 555 output is connected to J1.

inverter output connected to J1:

Clearly it looks like while taking the output from inverter output the mosfets are not driven properly. It looks like though the voltage output is sufficient the current is insufficient. I will take output from 3 inverter in parallel to see if things get improved or not. Also I will try with original 74HC4049.


texts: Implementation of an AUTOSAR NM sequence diagram

texts:
I am planning to implement the CAN NM as per the above sequence diagram. My understanding of the diagram is as follows. A Message Cycle Timer will be running continuously which is a configurable parameter. Once it expires, I call the function CanIf_Transmit(Std_ReturnType, PduIdType, const PduInfoType*).

The next step is the dotted line with function CanIf_Transmit(). The question here is: It is showing as empty arguments, but actually it contains arguments; then why does it show as empty arguments? Similarly for CanNm_TxConfirmation(PduIdType, E_OK). Why is it so? What is the significance of the dotted lines?

Autosar CAN NM


texts: The input of the op-amp (DC power supply & function generator)

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What is the difference between a  DC power supply (PS) and a function grnerator(FG) as an input of an op-amp?
While trying to test my summing amplifier circuit, I figured out that the op-amp do not work when the PS is the input of the op-amp.
This is the part of whole circuit:

When I set the PS output to 1V in constant voltage mode and connected it to the inverting input of the op-amp, I expected the output of the op-amp to be 1V as same as 1V.
Also I expected that the voltage at the inverting input to be 0 because it is virtual ground.
However, when I did that, the voltage at the inverting input was more than 0V and PS was operated in constant current mode with a few amperes.
On the other hand, this circuit operates well when I connect FG to the input of the op-amp.
What is the problem when connecting the PS output to op-amp input?

To help you understand the circumstances, I will explain my entire circuit below.
This is the full sketch of my circuit

I supply the power to two op-amps(TL082) from DC power supply(Vcc+ and Vcc-).
Vcc+ is also connected to the input of voltage reference (MAX6250).
The output of voltage reference is 5V and it is modulated from 0V to 5V by resistors and potentiometers.
V_dither is connected to function generator which have 10Vpp amplitude with 100Hz freq.
Verr is the final output of this summing amplifier circuit which is sum of the modulated voltage, V_dither and Vlia_in
Vlia_in is the place where unexpected situation occurs.
I connected the another power supply to Vlia_in and found out that situation I described above happens.(nonzero voltage at virtual ground, large amount of current(a few amperes))


texts: Why do soldering guns use copper as a heating element?

texts:
According to Wikipedia;

  The body of the tool contains a transformer with a primary winding connected to mains electricity when the trigger is pressed, and a single-turn secondary winding of thick copper with very low resistance. A soldering tip, made of a loop of thinner copper wire, is secured to the end of the transformer secondary by screws, completing the secondary circuit.
  ... Since the tip has a much higher resistance than the rest of the tubular copper winding, the tip gets very hot while the remainder of the secondary warms much less.

So basically, it uses copper as a heating element.  The only reason the "heating element" part has a higher resistance than the rest of the copper wire is because it's thinner.

So I guess they must be made like either of the bottom two in this picture.  I figure that they must be iron plated like soldering iron tips, as I don't see why they would be any different.

But this must be quite inefficient, especially considering how easily it can be improved.  There must be quite a significant amount of heat generated in the wrong places, given that the "heating element" is the same material as the "conductor".  The transformers appear quite small for what's surely a very high current, which would make this more of a problem.

Another thing I see (for some tips, in the style pictured) is that the shape of the tip is too wide to have much relative resistance (if it's made of the same material), so it must rely on heat conducted from the thin wires attached to it.

So wouldn't it be better if the tip had a bit of solid iron in the current path (like the top one in the image)?  If that's too hard to manufacture, than how-about brass?  Even cheaper, why not make the entire tip piece out of brass?  These would surely all be more efficient, with the heat concentrated in the right place, and be easier on the transformer (which means a smaller, lighter transformer can be used).


texts: I would like to do SSTA analysis using Cadence SoC Encounter. This tool requires the SPICE netlist. Does the costumers have access to TSMC's or any other vendor's spice netlist?


texts: Implementing the Dynamic Payload Length Feature between two nRF24L01+ Modules

texts:
I have two prototype boards, each with a PIC16F690 MCU, SPI connected to an nRF24L01+ Module. I have configured one unit as a PTX and the other as a PRX. I have no problem passing ASCII data from the PTX to the PRX as long as I send the exact number of ASCII characters (from the PTX) as is defined in the RX_PW_P0 register in the PRX device.

I have tried to enable the Enhanced Shockburst (ESB) feature in order to take advantage of the Dynamic Payload Length part of ESB. For the past few weeks, I have been communicating with a NORNIC Semi Technical Engineer trying to get the DPL feature implemented. We tried setting the ESB registers (EN_AA, FEATURE, DYNPD) and associated addresses every which way that we could. He has finally given up and so have I, particularly with the modules that I have purchased.

Now, I have read that there are Real vs Fake nRF24L01+ ICs on the market, and I believe that I have six of the fake ones. My NORDIC contact has told me that I can trust DigiKey and Sparkfun modules. DigiKey doesn’t sell the modules any more and two of the ones that I have came from SparkFun. I would hope that that module would have a Real IC! My question to the group is; does anyone know anything about the Real vs Fake, because my Engineer says that ESB works on their ICs.


texts:
I ask a antenna supplier about if his 433mhz antenna, if it is compatible with a 433mhz LORA chip, and his answer was "NO".
Is there any variantes when it comes to antennas with the same frequency? or any 433mhz antenna will work with any 433mhz radio chip, if we take 433mhz as an example.


texts: Is there a mathematical formula between wire size, current, temperature and wire type(Or resistance)?


texts: Why is home voltage value higher during the night?

texts:
I have been monitoring the voltage in my own home (Mexico 120V 60Hz). I have been graphing the values every minute and I'm starting to notice that during the morning voltage gets up to 127, and during the day (4pm) it can go as low as 118V — why does this happen?

The effect is quite similar to when I turn on the microwave for short periods, however these variations from 118V to 127V happen slowly during the 24 hrs of the day.


texts:
I'm trying to identify the manufacturer and component from a Belkin tunecast (Lightning) to FM transmitter device. I've searched through a couple of logo sites and Google and was not successful.

The part number being only numbers does not help either :(


texts: voltage, current, torque and speed in DC motors

texts: First off, please don't accuse me of not doing proper research before asking--I have done much research, but I could not find any answers that made sense to me. I have been playing with some DC motors, but I am confused as to the relation between voltage, current, torque and speed. I have noticed that sometimes, the motor seems to have little to no torque, yet when I limit the current to the motor, it seems to have a different behavior. Unlike this question, I want an answer that explains (preferably with formulas) what determines voltage, current, torque and speed, in simple terms. thanks!


texts: What Regulatory Requirements are Really Necessary for Sale in the USA?

texts:
I understand that unless you fall into some specific product categories that are exempt from FCC regulations, electronic products sold in the US are legally required to meet FCC EMC limits.  However, there has been a lot of debate recently with some colleagues about what, if any, testing at a NRTL to safety standards is required for the US.

My understanding is that safety requirements are driven by OSHA in the US.  However, my understanding is that they really only have the power to "recommend" and not really any legal authority.  I've also heard it be said that local counties / cities / states may require adherence to safety standards, but I've never heard of this before other than standard electric code type stuff.

Having recently received proposals from various regulatory agencies for European approval of a product, all of which suggested different standards to test to, sometimes not even having internal agreement about what we should test to, I'm thoroughly convinced that for anything but very established product categories no one has any clue about this stuff.  If you have a novel product, forget about it...  And now that functional safety seems to be becoming a bigger concern things seem to be getting even worse.

I'll try to stop myself from going off on a rant about how overambitious governments and regulatory agencies are destroying innovation and causing massive inefficiency in product development, but do any safety / legal experts here know if, for the USA, there is any "legal" requirement to worry about anything other FCC for consumer electronic products (e.g. not medical or anything special like that).  Does OSHA have any legal authority?


texts: Quartz crystal gasket, isolator, platform or whatever

texts:
Spent enormous time looking for these parts, and can not even find how they are called. Tried mouser, digikey, farnell, arrow. The best I found is "crystal insulator (thermal)" which is not what I am looking for.

By the way, last time I obtained them by desoldering old SMD quartz crystal assemblies.

Edit: yes, I want my THT crystal mounted to look this way, being held by this assembly

Why obsolete?


texts:
I'm trying to get my head around the DAC-08.  I have so far come up with this circuit as a test:

However - it is not producing the results I would expect.

Here's what it does:

U1 created a square-wave clock signal to drive U2 which is a binary counter.  The output of this heads into the DAC-08's (U4) data inputs.  I have buffered the signal through U3 because I noticed during my experimentations that the outputs of U2 don't always have the exact same voltage.  U3 should be redundant in this circuit.  I had it there mainly when I replaced the DAC-08 with am R/2R ladder to test the rest of the circuit.  The output of the DAC-08 is then fed through an op-amp in voltage follower mode.

Now, I'd expect a nice triangle wave form out of this, and that is (roughly) what I got with the R/2R ladder.

However, what I get from the DAC-08 is something more like this:

I have tried playing around with the order of the data pins, and it seems to always come up with the same (or similar) waveform.  Now, I'm new to the DAC-08, and I don't fully understand what all the pins do - and the data sheet fails to mention it either, so there is something I am missing.  I have gone through a number of example applications, but none of them have shed any light on this.

Does anyone have any experience with the DAC-08?  Can anyone point out where I am going wrong?


texts: Why would a LED datasheet specify a minimum operating current?

texts:
I am looking at the datasheet for the OSRAM Golden DRAGON® Plus LUW W5AM, a high power white LED.

It has a forward current of 20-1000 mA, surge current up to 2500 mA, and I think they want you to run it at 350 mA; that is what they use for most of the tests.

Notice that I emphasized the lower range of 20 mA. The forward current can not go below 20 mA. That is curious, but taken in isolation I would never have given it much thought.

Now, page 15 has a curious graph, titled Maximum Permissible Forward Current:

Here they iterate the minimum 20 mA operating current, even going so far as to exclude the area from the graph (it is covered with a grey block), and they use the strong words "Do not use below 20 mA".

Why can I not operate my LED at a current less than 20 mA?

Presumably they feel so strong about this that they have to warn me against it. Are there any electrical reasons, perhaps related to long-term reliability? Or is it just that they want me to use a more suitable LED?

I've tried to contact OSRAM about this, to no avail. Maybe it's not important to reply unless the customer is interested in a 100k purchase.


texts: Power transformer dual secondaries connection

texts:
I am new to electronics and want to build simple circuit.

I bought Radio Shack Power Transformer which converts from 120 V to 12 V or 6 V, it says on the back that if I connect two yellow wires it will be 12 V and if I use black and yellow it will be 6 V. My question is, can I use both at  the same time to power up two devices one 6 V and one 12 V?

Thanks


texts: Calculate equivalent resistance of the circuit

texts:
I am really confused with the above problem.

Each side represents a resistance R. How should I calculate resistance in case of infinite resistances.


texts: OrCAD doesn't yields same result for this difference amplifier

texts:
The question says:

Design an op amp circuit with inputs \$v_1\$ and \$v_2\$ such that
\$v_o = 3v_2-5v_1\$

One way to realize this circuit is to utilize difference amplifier which satisfies this equation
$$
v_o = \frac{R_2(1+R_1/R_2)}{R_1(1+R_3/R_4)} v_2 - \frac{R_2}{R_1}v_1
$$
for this circuit

Unequivocally, \$\dfrac{R_2}{R_1}=5,\ \  \dfrac{R_2(1+R_1/R_2)}{R_1(1+R_3/R_4)} =3 \implies R_2=5R_1, R_3=R_4\$. If \$ v_1=6, v_2=2 \implies v_o=3v_2-5v_1=3(2)-5(6)=-24\$. Using PSpice to realize this circuit, I'm getting different result


texts: Choosing the right voltage regulation - 12/24V to 5V

texts:
for my projects I always come across the power part which kinda bugs me. Usually i just open the TI webbench, put my parameters into and take whatever he gives me. But is that the right/good way?
Why and where do I choose linear vs step regulation? low heat low noise?
Example : Input Voltage 12/24VDC, Output Voltage  = 5VDC/3A max - pref. low noise > low temp
TI now gives me multiple choices:
TPS56339 - buck, seems good to me or the
LM604x0 - synchron step down -
LMR33630 - synchron step down  dont really seem to see a difference between these 2
Because all of theese are via switching I have to reduce the output noise, I didnt choose yet so I cant say how. Is there any way to choose the "best" one ?
Another questions about voltage regulation - is there a way to always get the desired output voltage even with 2 different input ? Same parameters as before, but I "dont know" which one is it, so I cant make a switch/jumper, but I always need a stable 5V output. ideas?
Thanks and greetings!


texts: Uninterrupted power supply for keeping arduino nano active always

texts: I have an Arduino nano running some CAN Bus program which does certain things on my car's instrument cluster. The Arduino board is currently powered from the car's 12V cig lighter socket using a 12 to 5DC adapter. I want the arduino to execute some code when the Car's ignition is turned on , the problem i am facing here is , when the car is cranked the power supply to the board is interrupted and the ardunio gets restarted again , i want to prevent this. The simplest solution i can think of is a diode isolated capacitor to prevent arduino from losing the power when the car is cranked. Is there a better way to do this? A reference image is as shown below. I am also not sure what values of diode and capacitor to be used here. Car's 12V becomes 13 to 14.x V when the engine is on too.


texts: Nominal Voltage with 18650 cells and DC-DC step up board

texts:
So I'm building a simple 12v router UPS and I have trouble with one concept - Nominal Voltage. So the build is very simple, some common 18650 cells, DC-DC voltage step up board, and a BMS (battery management system) board to charge and discharge (safely) the 18650 cells. Connecting them all is super easy too. Issue is, I need to determine how many cells I want to use. The build guide I followed used two batteries, but the only BMS board I could get my hands on needs 3 cells. Easy enough to adjust my build, but my question about the cells being fully charged and the effect of the higher voltage.

What I could research is that 18650 cells have a nominal voltage of 3.6v, so with some easy maths we know that 3 cells (in series) will produce 10.3v nominal voltage for the whole circuit. Easy enough, I can still use the step-up board to boost the voltage to the desired 12v. thing is, if the cells are fully charged they will be at 4.2 v, which will result them all combined to provided 12.6v (too much). So what does nominal voltage really mean? and will the step up board still work when the batteries are fully charged because then it technically wont be stepping up the voltage, its already past 12v.


texts: Current Monitors for Avalanche Photodiodes

texts: I've come a across a document by Linear Technologies that suggests several circuit schematics to interface with an Avalanche Photodiode (APD). They are referred to as current monitors and placed before the APD (in the schematic, in practical terms it is irrelevant). Aren't these the same as transimpadance amplifiers? If not, what exactly are the differences/advantages/disadvantages, specially compared to the approaches suggested in this answer ?


texts: Summing Amplifier Zero Input Current/Voltage?

texts:
I have 2 questions related to a summing amplifier:

Why is the voltage at the inverting terminal of the input equal to zero?
Why is the current at the inverting terminal of the input equal to zero?


texts: Is there such a thing as a 'Constant Power Source'?

texts:
Academic question: Is there such a thing as an electrical constant power source, which delivers energy at a fixed rate?
Specifically ... there are voltage sources and current sources, which maintain (an approximation to) a reliable fixed voltage/current respectively. A current source will deliver electric charge at a fixed rate, charging a capacitor's voltage linearly; a voltage source will deliver magnetic flux at a fixed rate, 'charging' an inductor's current linearly.
I'm trying to figure out if there is a supply that could deliver energy at a fixed rate - a power source - so its voltage changes to whatever is necessary to deliver a current such that \$VI\$ is a fixed amount.
(I've tried Googling this, but the search is swamped by power supply ads, domestic power advice etc).
Guessing at its properties...

it would treat voltage and current symmetrically! So a fixed power source would charge up a \$1\mu F\$ at the same rate as a \$1\mu H\$ inductor.
it would charge a capacitor's voltage at a rate of \$ V \propto \sqrt{T}\$, because the energy is increasing linearly in time and \$E = ½ CV^2\$.
same with an inductor's current.
any resistor placed across it would dissipate the same heat regardless of the resistance - by definition. Doubling the resistance would increase the voltage by a factor of \$\sqrt{2}\$ and decrease current by the same.
its impedance is ... undefined! Open circuit voltage is infinite (like a current source); closed circuit current is ... also infinite (like a voltage source). Hmm.

For extra points: any other interesting properties? Are they actually a thing? What would they look like?


texts: How do the streetcars in Toronto draw power from the lines?

texts:
I've tried googling this but to no avail. I've been trying to figure out how streetcars can draw power from a short circuit.

For reference:

(source: roadstories.ca)

If I imagine the power lines simplified as a shorted battery like so

and we assume the streetcar acts like a resistor like so

Would it not just reduce back to the first diagram with the short circuit?


texts: Atmel SAMC21 microcontroller unwanted resets

texts:
I am using an ATMEL SAMC21 MCU on an ebike project. The MCU is involuntarily resetting every 30s to 1min. This causes a problem as it's controlling the bike in real time, giving noticeable gaps in power and resetting to defaults the power mode selection. I am inputting three analog voltages in it, I have an alphanumeric LCD plugged to it and I am outputting a voltage with a DAC. The program runs PID algorithms for control as well as battery capacity estimation ones. I also coded a timer in microseconds. Knowing this, is there anyway to know what are the different reasons these resets could be due to, so that I investigate?
Thank you for your help!


texts:
In the following circuit:

Ib is given as:

I don't understand how they arrived at this. I thought it would be a voltage divider between Rsig and Rb||Rbase divided by Rbase:

Can anyone explain? Thanks.


texts: Unusual resistor symbol: resitor with Z overlaid

texts:
I found this symbol in a vendor circuit diagram. What does it mean? It looks like they are trying to convey some sort of limiting.

It's a resistor symbol with a line over the top that has both the top and bottom ends flattened.


texts: In which cases should I use Z as output in HDL?

texts:
I created a simple multiplexer which feeds different input into output depending on statemachine.
Now there are states when I do not need the output so I usually set it to 0.

INST <= "01" WHEN fsm_state =  read_first_half
                OR fsm_state =  read_second_half
                OR fsm_state =  next_r ELSE
      "10" WHEN fsm_state =  write_first_half
                OR  fsm_state =  write_second_half
                OR  fsm_state =  next_w
                ELSE  "00";

As far as I remember there was a third syntetisable value 'Z'. I far as I remember it's floating value with high impedance.
When do I use it and is it safe to use? Will it be syntetisable on all FPGAs?


texts: Oscilloscope coupling and effects on the measured signal

texts:
I have a basic understanding of the of coupling settings on an oscilloscope, but I need some help to understand what I am seeing on scope.

I have a signal generator, with an arbitrary function set, a 20 us pulse HIGH with 80 us LOW. Amplitude is set to 10 V, and the signal generator allows me to set between -511 to +511 points to shape the signal. I set the first point at +511 (for 20 us) and the remaining at 0 (for 80 us).

When I connect to the oscilloscope to measure the signal, depending on the coupling chosen I get different outputs.

DC 1 MOhm, shows me the pulse approximately at 10 V peak.
AC 1 MOhm, shows me a similar approximately 10 V peak, but shifted down -2 V.
DC 50 Ohm, shows me approx. 5 V peak pulse

When I connect the output from the signal generator to my circuit, (I am using the signal to control a MOSFET,) if the DC coupling is ON on the scope, the voltage is not high enough to turn on my MOSFET, but if I us the DC 1 MOhm coupling then it works fine.

I would like to understand what is happening with the different coupling settings. Particularly why signal is approximately halved from the 1 MOhm to 50 Ohm. And why it effects my circuit in the way it does?

And any advice, in terms of coupling choice, when wanting to make measurements of signals and voltages across parts of a circuit, would also be appreciated?


texts: What happens on heating an intrinsic semiconductor?

texts: Suppose I have an intrinsic semiconductor and I heat it up on one side. What will be the changes that will occur? As far as I know it won't become an extrinsic semiconductor because that would need to introduce impurity (doping) so what will be the other possible consequences? Am i correct considering that semiconductor would remain an intrinsic semiconductor?


texts: Radio wave transmission and receiving antenna

texts: When you transmit signals at radio frequency why are the antennas open ended (open circuit)? I can understand that changing the electric field causes changes in the magnetic field and hence the wave will propagate. But what I don't understand is how you can have an electric field if the circuit is open ended in the first place because the impedance should be infinite?


texts:
I need to calculate the Block Check Character (BCC) via XOR of this array

byte data[] = {0x02,0x06,0x06,0x06,0x06,0x06};

and i'm under Arduino. Is there already any method out of the box to accomplish this?
Thank you


texts: Data logger using ARM 9 (Friendly ARM Mini 2440 kit)

texts:
I have been working on this kit for the past month and have simulated some basic programs using Keil (non os using just C). I was assigned a project of making a data logger which stores the data in SDLC (synchronous data link protocol) format on SD card.

Thus my project has 2 very straight forward parts:

Receive the data in sdlc format (TTL compatible).
Store on SD Card.

I have searched the forums of both Keil as well as Mini 2440 but still clueless
about the interfacing of an SD card interface using simple C. Everybody seems to be suggesting anything but C. I have read the manuals and other PDF regarding interfacing using both the SPI as well as SD bus mode and whatever I could make out of it was written in a code which is given below:

#include <S3C2440.H>
#include<stdio.h>
void sd_card_init(void);
void spi_delay(void);
int main()
{
    //pclk is 12MHZ
    GPECON=0x0a800000; //clk mosi miso 13 12 11
    GPGCON=0x00000030;//ss 2
    SPCON0=0x18;//set the clk & enable the master
    SPPRE0=0x0e;//set the clk at 400 khz
    SPPIN0=0x01;//derive the mosi level
    sd_card_init();
    return 0;
}

//**************************************************************
void sd_card_init()
{
    unsigned char x;
    unsigned int cmd0[]={0x40 ,0x00 , 0x00, 0x00 ,0x00 ,0x95};
    unsigned int cmd55[]={0x77 ,0x00 , 0x00, 0x00 ,0x00 ,0x95};
    unsigned int cmd41[]={0x69 ,0x00 , 0x00, 0x00 ,0x00 ,0x95};

    GPEDAT|=0x1000;

    //mosi=1;

    GPGDAT=GPGDAT|0x0004;

    //cs=1;

    spi_delay();

    //********************RESET COMMAND************************

    GPGDAT=GPGDAT|0xFFFB;

    //cs=0;

    for(x=0;x<6;x++)

        SPTDAT0=cmd0[x];

    //**********************check if card is ready or not.******************

    while((SPRDAT0==0x01)||(SPSTAT0&0x01==0))
    {
        for(x=0;x<6;x++)
            SPTDAT0=cmd55[x];
        for(x=0;x<6;x++)
            SPTDAT0=cmd41[x];
    }
}

void spi_delay()
{
    unsigned char i,j; //wait for 74 clk cycles or more

    for(i=0;i<255;i++)
        for(j=0;j<255;j++);
    }
}

This is my code which I am trying to simulate on Keil for SPI. I have even tested this using an oscilloscope but could not even find the clock, so if anything else has to be done please tell. I am in great need of your comments and help.


texts:
I'm sending data to and A/D converter and I need the command data to be delayed at least 50ns from clk_19khz. Here is what I have so far.
How do I insert a delay of 50ns which is a requirement for the A/D between the clk_19khz and my first Dout bit to the A/D?
I'm using a Xilinx FPGA in ISE. The completed project will use vivado as the IDE Thanks for the help!

         library IEEE;
           use IEEE.STD_LOGIC_1164.ALL;

            -- Uncomment the following library declaration if using
               -- arithmetic functions with Signed or Unsigned values
              --use IEEE.NUMERIC_STD.ALL;

            -- Uncomment the following library declaration if instantiating
             -- any Xilinx primitives in this code.
              --library UNISIM;
              --use UNISIM.VComponents.all;

       entity PSOL is
          Port ( clk : in  STD_LOGIC;
                 clk_19khz : OUT std_logic;
                 Dout :out std_logic);
          end PSOL;

      architecture Behavioral of PSOL is
         signal temp : std_logic;
         signal count : integer range 0 to 1301 := 0; --1301
       --signal temp2 : std_logic;
         signal dcount : integer range 0 to 11 := 0; --
         signal start : std_logic  := '1'; -- indicates the start of
         signal parity : std_logic := '1'; --used to varify data sent
         signal stop : std_logic := '0'; --indicate when word/command has
         signal enable : std_logic;
       --signal chip_select : bit :='1'; -- active low

    begin
         process (clk)
             begin
          if (clk' EVENT AND clk='1') then
            if (count = 1301) then --1301
                temp <= not(temp);
                count <=0;
                clk_19khz <= temp;
                enable <= '1';
            else
                count <= count + 1;
            end if;
             if (enable = '1') then

               dcount <= dcount + 1;
               parity <= '1';
               stop <= '0';
               start <='1';

                 if (dcount < 12 and start = '1' and stop = '0') then
                    CASE dcount is
                     when 1 => Dout <= start;
                     when 2 => Dout <= '0';
                     when 3 => Dout <= '1';
                     when 4 => Dout <= '0';
                     when 5 => Dout <= '1';
                     when 6 => Dout <= '0';
                     when 7 => Dout <= '0';
                     when 8 => Dout <= '1';
                     when 9 => Dout <= '1';
                     when 10 => Dout <= parity;
                     when 11 => Dout <= stop;
                     when others => null;
                    end case;
                 end if;
                  enable <= '0';
         end if;

        end if;
end process;

 end Behavioral;


texts: Is the hybrid-pi parameter hie really equivalent to (beta+1)*re?

texts:
I'm reading a book on feedback amplifiers at the moment and it makes comprehensive use of a simplified hybrid-pi model.  A parameter that keeps popping up is hie and I've always considered this to be equivalent to $$\left ( \beta + 1 \right )* re$$ in the re transistor model and for good reason too: previous stackexchange question and here (page 12).

However, what's confusing is the size of the "typical" resistances given to hie (if you're lucky enough to find it!): 1k to 10K.  Really?  Lets look at an example, using that classic hFE of 100 and an Ie of 50mA.  $$101 * \frac{26mV}{50mA}\approx  52\Omega$$

I'm clearly missing something, because those figures don't compare at all.  In this thread a correspondent makes the same point (that the actual input resistances are much smaller).  However, there's a suggestion that maybe hie is a small signal AC parameter that's distinct to the hybrid-pi model and I'm left wondering if the corresponding re model equivalent equations are correct?

Can somebody set me straight on this? Is the comparable equation justified and why are those typical values so out of whack?


texts: An intuitive question on the meaning of bins in a power spectrum of FFT

texts:
In Fourier analyses and FFT we see the power spectrum with a frequency resolution.

I'm trying to understand the meaning of it. What is binning? What does power spectrum indicate.

To expound my question I give the following example.

Lets say I add cosines at different frequencies and phases as:

1Hz with amplitude 4

2HZ with amplitude 2

3Hz with amplitude 1

4HZ with amplitude 0.5

5Hz with amplitude 2

6HZ with amplitude 0.8

7Hz with amplitude 1

8HZ with amplitude 2

9HZ with amplitude 3

10HZ with amplitude 0.1

11HZ with amplitude 0.3

12HZ with amplitude 0.5

And lets say I want to create a power spectrum by binning with frequency resolution 4Hz, so I will have 3 bins as:

So for the first bin I will have 1Hz 2Hz 3Hz and 4Hz

for the second bin I will have 5Hz 6Hz 7Hz and 8Hz

for the third bin I will have 9Hz 10Hz 11Hz and 12Hz

So my first bin will correspond frequencies between 1Hz and 4Hz and the power be quantified by squaring amplitides and adding them as: (4^2  + 2^2 + 1^2 + 0.5^2)

my second bin will correspond frequencies between 5Hz and 8Hz and the power be quantified by squaring amplitudes and adding them as: (2^2 + 0.8^2 + 1^2 + 2^2)

my third bin will correspond frequencies between 9Hz and 12Hz and the power be quantified by squaring amplitides and adding them as: (3^2 + 0.1^2 + 0.3^2 + 0.5^2)

Did I understand the meaning of power spectrum and the frequency resolution? Before digging in to FFT I just want be sure about the big picture.


texts:
I am thinking about designing a radial flux permanent magnet generator. However, I could not find any information about determining the tooth width. Should the tooth width be all the way the same as the magnet width, or can it be thicker?

So I am interested in lt and lv relation.


texts: TOSLINK UART, limited to 9600 baud. Need ideas for improving speed/stability

texts:
I've built a UART transceiver with a FC684205R and FC684205T pair. Both use TTL logic levels and I thought it would be a straight forward case of [optic lit = logic high].

However this wasn't the case, the signal off the receiver seemed to be inverted when simply applying 5v to the transmitter Vin. I tried to invert the signal coming out of the receiver module however the transistor was only held open momentarily, which I figured was because the receiver module couldn't provide enough current to drive the NPN (S8050.) So I inverted the input to the transmitter module.

When probed by my oscilloscope the receiver module output a very nice UART signal. But when I disconnected the oscilloscope the amount of noise and garbage I got was crazy. The "resting" voltage was about 2.00V and I got peaks of 5V and lows of 0V, outputting a load of nonsense to my PuTTY terminal.

I read somewhere that these modules use NRZ encoding. However when crossing the Vout with a 47uF & 15pF and GND the signal cleans up a lot (however not as clean as when attached to the oscilloscope.) It's workable but I was hoping someone could explain to me what might be going on here.

Why did adding the capacitors or oscilloscope in parallel eliminate this NRZ looking encoding?
How can I improve my circuitry as I would like to get speed better and cleaner than I can at 9600 baud.
I'm using this as a way of transmitting UART data across a workshop (20m) to a CNC machine that is used as a llasma cutter (the plasma cutter is blasting out a lot of RF noise that was knocking out the vanilla USB solution.)


texts: a microcontoller pin stuck permanently at 0

texts: Is it possible in general to have a pin of any uC stuck at 0, including when the power is off? Particularly I'm interested in stm32f3


texts: Pass power to components on a high speed spinning motor

texts:
I have a small Emax RS2205 2600kv 16v DC Motor that is turning a PCB with IC chips that needs to be powered.

I want to send 2 power cable (VCC and GND) from to stationary battery to the rotating PCB.

Here's what I am trying to build:

I can't use slip ring because of the engine will be hitting some high RPM. Though if you are aware of a miniature high RPM (2000+) 2 channel 5v slip ring please recommend.

I couldn't find brushless slternators, nor rotary transformer that are small in size that can pass 5v either.

What is the best miniature lightweight solution for transferring power for such system?

Thank you

EDITS

I found a wireless charger, it might work, though I'm afraid it might damage the arduino which is going to be placed on top of it, or right next to it


texts: 10 million switching cycles with a hall effect sensor

texts:
I am trying to build a pull switch for my invention that can survive 10 million cycles, and in a previous question here I recieved advice not to use a mechanical contact.

The other problem is size. The sensor assembly cannot be larger than 1x1x4 centimeters and the sliding distance can't be larger than 2 centimeters, otherwise I would need to do a mayor redesign of my invention.

There won't be more than 3-4 switching cycles per second, usually less, and the 10 million cycles is my extreme worst case scenario after several years of use. The sensor assembly will be sealed so there shouldn't be any problems with moisture, but perhaps some loose material from the casing due to wear and tear.

I've searched the net for a suitable pullswitch but found nothing that would work.

My questions are:

I tried using a hall effect switch with a permanent magnet and it worked fine, but wouldn't magnetism cause problems with EMC testing, CE and FCC rules?

I need to use a non latching hall effect switch, are there any reliability issues with those?

Do permanent magnets loose some of their strength over time? The sliding distance needed to close the switch cannot change more than a few milimeters.

Are there any other good alternatives besides hall effect sensors? Perhaps some form of piezo sensor? Preferably one that can work with the voltage levels of Arduino, though I have plenty of room on my PCB for resistors so wrong voltage shouldn't be a showstopper.


texts:
I have got a control board with TMS320F2808 DSC. This
control board was designed by someone else. I need now
to connect an emulator XDS100 to mentioned DSC. My
problem is that I don't know where to connect JTAG
connector. There is no 14 pin header on the control
board and I haven't any schematic to this board. Can
somebody give me an advice how could the connection
point for JTAG look like? I have been trying to find
some 14 "holes" organized in "matrix" 7x2 pattern but
without any success. Thanks for any suggestions.


texts: What is the purpose of R2 in this discrete voltage regulator circuit?

texts:
I understand the general working of the circuit - R1 biases Q1, Q2 acts as an error amplifier closing Q1 just enough to get 1.4V at it's base. What is the puropse of R2?

simulate this circuit – Schematic created using CircuitLab


texts: Declaring vector variable in the Verilog not starting with the MSB(e.g,. reg var[0][20])

texts:
I am familiar to the syntax described in here

net_type [msb:lsb] list_of_net_identifiers;
reg [msb:lsb] list_of_register_identifiers;

For example, to declare the 32bits memory address, I could use the syntax like
reg [31:0] address;

Also to declare the memory comprised of the 16 elements which consist of 32 bits each,
reg [31:0] mem [15:0];

However, I could frequently face the syntax like below to declare multidimensional arrays.
reg [31:0] mem [0:15]

I've googled it and found one related article in here.
It seems that whether the larger number comes first or not, the first number before the colon (:) is the MSB and the LSB follows. It seems like the difference comes from the preference of coding.
However, I think mixing [31:0] and [0:15] style is little bit count-intuitive and confusing even though it depends on the preference. I could see a lot of mixing especially in the declaration of multi-dimensional arrays. Why is it allowed to be used? Is there any advantage that I couldn't notice?


texts: I'm using an ATmega32u4 (Arduino-board) and internal reference to measure the VCC voltage (handheld device with LiPoly-battery). For a very long time I'm getting 3.27V before it drops when it is near the end. How usually the measured battery voltage is converted to a state of charge in %?


texts: As a general rule, should input pins be protected with a series resistor?

texts:
I have read this article about why and how protect input pins. The article mentions the specific scenario of industrial electronics, with the input pin conneted to a long wire.
However, if the input pin is connected through a short wire to a sensor or a pot. do the rules in the above article be applied as well?


texts:
I want to implement a Mesh Thread network on Sub-1GHz especially on 868MHz using the Semtech's SX1276 as a radio chip.
I bough two modules to do some tests.

I'm trying to find out how these kind of networks are formed.

I mean, how are they really formed at the beginning.
What happens when all of them are powered at the same time? Which does decide to be the router, which does the node? which does the parent and which does the child?

Is this frequency suitable for that kind of networks? I want to spread over many nodes in an agriculture and/or industrial area.


texts: Spice Simulation of EMI in Long Parallel Wires?

texts:
I was thinking about using an external power supply for multiple pieces of analog audio gear. But it occurs to me that even if I use separate grounds for power and signal, because the wires would run alongside one another, changes in current on the power ground (from a power amplifier driving a 600 ohm load for example) would electromagnetically induce currents in the supposedly clean signal ground. Is this correct?

If yes, how can I model this in LTSpice? I assume it would just be two inductors coupled to some degree. Can someone explain roughly how to model EMI in long parallel wires?


texts: Measuring battery voltage and saving energy

texts:
We have a pcb with an Atmega (MCU) on it, that most of the time is in sleep mode, consuming 50-100 uA .

When it wakes up, and only then , we need to take a sample of the battery voltage to send to the server .

I was considering few options and wonder which is the "right" if we dont want to loose current .

Voltage will be 3.6-4.2V when its full via 3.6V regulator .

connecting the battery with serial resistor(>50k ?? ) directly to the ADC.
take 2  large resistors(100k?) and create voltage divider of the battery voltage , and connect the point between them to the ADC .
connecting the battery directly to the ADC ?

--- should we measure after or before the regulator ??

A 100k resistor will leak about 50uA of current which is no that good ,because the Atmega itself should be the only and main consumer on sleep with 50-100uA .


texts: "Increase" of a register in VHDL and hardware synthesis

texts:
Suppose you have already defined a register (for instance called "reg") in VHDL, for instance as a vectors of 4 bit.

Now consider the operation: reg <= reg + 0001; it is like reg ++ in C.

My questions are:

1) how can reg store the result of the sum between reg itself and another number? The result is expressed by 4 sum bits and 1 carry bit, so there are 5 bits...

2) how will the synthesis be? An adder which takes 0001 and reg as input will give 5 output wires... How will they be connected to reg  (which has only 4 input wires)?


texts:
This us for a liquid-cooled computer or server.

Is it at all possible to ”daisy-chain” (possibly not the right term) multiple Arduino boards together for the following inputs?

Multiple different types of thermocouples (minimum of 8).
Multiple flow rate sensors (minimum of 8).
Fan control with rotational sense for each (3 pin, minimum of 4).
Pump control with rotation sense for multiple pumps (minimum of 1 pump).


texts: Is the NAND logic gate perfectly symmetrical?

texts: In other words: if we swap A and B, will Q behave exactly the same in DC and transient analysis?


texts:
Our prof. at the university asked why the LMV324 is particular. Which is the characteristic that made this component so common in the modern electronics. He was talking about the ring gain or something like that, but I’m not sure if the answer is in there.
My question is: in your opinion, which is the main characteristic of this amplifier and more important how was designed (the scheme solution adopted)?

Maybe is something related with PMRR


texts: AGND and DGND connection using flash ADC, totally stumped

texts:
So, I am designing a PCB with the classic scenario of having both sensitive analog signals and noisy digital signals...

Analog and digital regions are separated. the have their own gnd
planes and isolated supply's.
A flash ADC is the information bridge from the analog side to the
digital side.

I have tried to find the answers to this but I keep seeing the same thing. which basically this photo in summary:

Now this shows the star ground at the ADC.

Why does it have to be close the ADC?
I would think that you would want the connection between the regions as far away as possible from any kind of noise if in fact the connection is just there so the digital and analog reference don't drift apart and damage the ADC...

My thought is that depending on the ADC, like a SAR or Sigma-Delta ADC, you really need the DGND to be exactly the same as AGND for it work correctly... hence why the star is near the ADC.

But for Flash and Dual-Slope ADC, AGND does NOT need to be in reference to DGND. the only the thing going from the analog to digital portion is small leakage current on the comparator/opamp inputs (photo below shows configuration or the ADC I am using).

Do I still need to put the star near the ADC this case?

Thanks for your help,my brain hurts from thinking about this.


texts: Can avrdude address individual usbtiny programmers?

texts:
I'm envisioning a panel programming jig. In my mind, it consists of a Raspberry Pi, a powered USB hub, and a collection of usbtiny clones each connected to a pogo jig and a target on a panel.

The only question I haven't yet worked out is, when invoking avrdude, I can use -c to tell it to use usbtiny... but how can I tell it which usbtiny I want it to use? The plan is to use a script to go through them all one at a time, and IMHO just attaching a bunch of programmers is easier than trying to come up with a bolt-on to multiplex the SPI bus from one programmer to all the targets.


texts: Fisher Scientific T-30 Metal Detector - Circuit schematic

texts:
Looking for service manual for this old thing or a very similar detector it is from 1965 with germanium transistors .. I didn't think there was any real use for it until someone asked
.. some photos
https://imgur.com/a/0fV72w5
board photos
https://imgur.com/a/BlseVfS


texts:
Thanks for your support in this forum.
Currently I have a couple of PCB that I need to provide a double input power supply and transient protection.
The specs for this couple of PCB are Vin= 9 to 17.5V. (12V nominal), consumption is about 18-24W/each (working mode dependent).
Long cable runs and hot plugging could induce transient voltage spikes which may exceed the input voltage limit and I need to protect it.
The system will have 2 VDC inputs, and will be capable to have a hot-swap between them. As you can see in the attach schematic, the 2 Schottky diodes allow to do this, besides reverse polarity protection.
The input battery used could provide up to 16.8V max (10-16.8V range).
I am looking for a TVS Diode (see it in the attach file).The problem I am facing is about the specs in TVS diodes. As far as I understand, Vclamp should be 17.5V, but then, Vr and Vbr are too low.(should be 17V minimum)
Any idea how to solve this short margin between Vr/Vbr and Vclamp? Could I place a Zener to clamp it to 17.5V?
Any tip will be welcome. Thanks a lot.


texts: Inductive kickback when applying PWM to the output of an alternator

texts:
simulate this circuit – Schematic created using CircuitLab

I've got a fairly odd LED setup whereby a vehicle's alternator is being used to generate the power (rectified to DC) required to run said LEDs, which will be used for it's headlights.  I would like to use PWM to control the brightness of the LEDs and bypass that pesky LED voltage-to-brightness curve.  However I'm not sure how to handle the inductive kickback when the inductor is the thing generating all my power!

edit I have included a rough diagram.  There will be voltage control circuitry to regulate the alternator (3 inductors) to the 36V i need, and the part numbers & values are not what I plan to use at all.  But you can see now where I intend to apply the PWM much more clearly.  I apologize for my previous ambiguity.

Do i treat it like any other inductor circuit or are there special concerns that i don't know about?


texts:
I need to know the maximum clock frequency of my design. But RTL compiler does not give me the max frequency if I dont give a timing constraint. (Actually I am not sure if it will give me the frequency if I specify a timing constraint)

I read the RTL compiler manual and it gives two possible ways to define clock period.

The first one:

set clock [define_clock –period <periodicity> –name <clock_name> [clock_ports]]

The second one

define_clock -domain domain1 -name clk1 -period 720 [find / -port SYSCLK]

Here is my script. I put the timing constraint after "elaborate".

set_attribute lib_search_path /opt/cadence/local/FreePDK45/osu_soc/lib/files
set_attribute library {gscl45nm.lib}

read_hdl -v2001 ccm.v

#timing constraint
set clock [define_clock –period 2000 -name clk [clk]]

#synthesis
synthesize -to_mapped

#generate results
#netlist
write -mapped > ccm_synth.v

#statistics
report timing -lint > timing.txt

I tried several options below, but cadence keeps complaining about my syntax:

Command:

set clock [define_clock –period 2000 –name clk [clk]]

Error info:

invalid command name "clk"
Encountered problems processing file: rc.tcl

Command:

set clock [define_clock –period 2000 –name clk]

Error info.:

Error   : A required object parameter could not be found. [TUI-61] [define_clock]
        : An object of type 'pin|port' named '–period' could not be found.
        : Check to make sure that the object exists and is of the correct type.  The 'what_is' command can be used to determine the type of an object.
  define_clock: defines and apply a clock waveform

Command:

set clock [define_clock –period 2000]

Error info:

    Error   : A required object parameter could not be found. [TUI-61] [define_clock]
            : An object of type 'pin|port' named '–period' could not be found.
            : Check to make sure that the object exists and is of the correct type.  The 'what_is' command can be used to determine the type of an object. define_clock: defines and apply a clock waveform

Command:

define_clock -name clk -period 2000

Error info:

Error   : A required object parameter could not be found. [TUI-61] [define_clock]
        : An object of type 'pin|port' named '–period' could not be found.
        : Check to make sure that the object exists and is of the correct type.  The 'what_is' command can be used to determine the type of an object.
  define_clock: defines and apply a clock waveform

Command:

define_clock [-name clk] -period 2000

Error info.:

invalid command name "-name"
Encountered problems processing file: rc.tcl

Could someone please suggest the correct syntax?


texts:
So I was solving a CIE Physics (9702) past paper and came across this question:
[9709/41/O/N/09 // Q.7.B.]

The questions were:

7.(b).(i) On the axes of Fig. 7.2, draw a graph to show the variation with time t of the potential difference across diode A.

7.(b).(ii) On the axes of Fig. 7.3, draw a graph to show the variation with time t of the potential difference across diode B.

I did draw the graphs such that, for 7.(b).(i), when the  alternating voltage is positive in figure 7.2, the voltage across diode A is also positive and  when the alternating voltage is negative in figure 7.2, the voltage across diode A is 0, essentially drawing a half-wave rectification graph.

And for 7.(b).(ii), in figure 7.3, I drew the same graph but with a phase shift of 180 degrees showing that when the alternating voltage is positive the voltage across B is 0 and and when the alternating voltage is negative the voltage across diode B is positive.

Now the problem is that apparently this is wrong and the graphs will be drawn the other way around i.e. the  graph that I've drawn for question 7.(b).(i) was actually the graph that was supposed to be drawn for 7.(b).(ii) & similarly the  graph that I've drawn for question 7.(b).(ii) was actually the graph that was supposed to be drawn for 7.(b).(i).
I can't seem to understand why it'll be this way though.

The examiner's report says this:

Question 7(b)

(i) Many candidates did not seem to realise that, for an ideal diode that is forward biased, the potential difference across it would be zero. There were many poorly-drawn sketches with peak values shown above those on Fig. 7.2.

(ii) There were very few correct responses here. In many answers, an inverted voltage was indicated.

I don't understand his explanation for it either.

The guy/girl from physics-ref.blogspot (He/She makes solved solutions for 9702 papers and more. Highly appreciate his/her help.) also answered this question along with an explanation for it. Their answer is correct but I didn't really understand what he/she meant by their explanation for it so if one of you readers do understand please try explaining it to me in simpler words I guess.

Here's his/her solution:

Please help soon my exams are in less than a month.
Thanks.


texts: How are phosphorescent displays used as monitors?

texts:
I've recently been looking into old displays such as the ones on the tektronix 4010. These displays "draw" on a phosphorescent screen in a way that is really fascinating, and I want to recreate it. My goal is to use an Arduino controlled blue laser and glow in the dark paint to mimic one of these proto-crts.

There are a few abilities of the tektronix displays which I don't fully understand though. The first is the ability to clear the phosphorescent panel simply by emitting a short flash. As far as I know this should just flood the screen, not clear it. The wiki page on storage tubes says that in order to make the panel light up you excite it with energy above a certain threshold and then to "erase" it energy is applied above a second threshold. Practically speaking, does this just mean that I can flash a bright bulb at my makeshift screen and have it clear (I find this unlikely) or is this some flaw in my setup.

Secondly, how are these displays so readable even in daylight as well as having very long persistance with almost no noticable fade? Is this just some very powerful phosphor or is there something else? It doesn't seem from any of the videos I've seen that the displays are refreshing at all, though I do wonder what you would see if you killed the power. Anyway, can someone more knowlegable, maybe even with experince with such display shed some light?


texts: Where do the power leads attach to this simple sound circuit?

texts:
This is a really simple circuit that goes to a speaker in a clock that my friend wants fixed.
The power lead broke off.
I just need to know where the positive power lead gets attached.
It is powered with 2 AA batteries.
The pair of yellow wires attach to a button, presumably for testing.
The pair of black wires go into the clock, presumably to be switched on when the hour strikes.
The pair of red wires goes to the speaker.
The epoxy blob appears to just be a stand-off so that the circuit doesn't hit the bottom of the enclosing box.
No idea what tags to use on this question.  Please edit :)


texts:
I have made an input mod to increase the input impedance of my Creative T3100 speakers.

But now even if the potentiometer is at the lowest level some sound from the input is coming off from the speakers, distorted and at constant low volume (not affected by the potentiometer level). Normally (e.g if I bypass the mod) there is some clean sound coming off the speakers bit is nearly inaudible even if you put your ear next to the speaker. Here are the pins I used (photo taken before I did anything)

And here is a schematic I found of the speakers

UPDATE:
Apparently the output of the mod is too loud (measured after the filter):

Without the mod:


texts:
I simulated this circuit using Qucs:

With Vin = 5V, VB = 0.746V and VC = 0.024V which means that the BJT is operating in the saturation region.
But I don't understand why. Vcc = 5V and Vin = 5V. RB = RC = 1k ohm. So I expect that VB = VC and the base-collector junction is reverse biased which means that the BJT is in the forward-active region.
What is the wrong with my analysis? and is there a "trick" that I can use to determine the mode of operation of a BJT?


texts:
I am trying to make small data logger project with STM32F072 as an opportunity to get more familiar with STM's HAL.

With CubeMX I generated HAL code that has SPI and also includes FatFS.

Right now I am having issue gluing SPI low level drivers to FatFS.

Can someone please point me in the right direction or post some examples on how to glue HAL SPI functions to FatFS? Right now I see that there is following declaration generated by HAL, but I can't seem to find any actual implementation that works.

Diskio_drvTypeDef  USER_Driver =
{
  USER_initialize,
  USER_status,
  USER_read,
#if  _USE_WRITE
  USER_write,
#endif  /* _USE_WRITE == 1 */
#if  _USE_IOCTL == 1
  USER_ioctl,
#endif /* _USE_IOCTL == 1 */
};

Any examples or documentation on how to implement this would be very much appreciated.


texts: Delay in turning on two different start buttons in Star/Delta starter on PLC

texts:
Currently I'm working on a university project based on Star/Delta Starter on PLC.
I wrote program using LD, that switches on the circuit with a motor rotating forward (of course with star/delta starter - here I've used TON timer), then with another start button called "Start back" after pressing "STOP" I can turn the motor on backwards. Everything is working fine. Now I'm trying to figure out how I can set the delay after pressing STOP button (let's say 8 seconds) to block user with pressing START button with another direction.
For example, motor has been started forward, then we press stop and we cannot press "START BACK" until 8 seconds will elapse (to secure the motor).
I was trying to use TOF timer 2 times (one timer for Forward and one for Backwards) but it doesn't solve the problem.
Is there any logic way to solve this problem?
Thanks in advance,
Cheers


texts: Beginner Question - Solder won't stick to a certain wire

texts:
I am trying to tin some wires as they won't stick to the IC pins that I'm soldering them to. The problem I am having is that the solder won't stick to the wire.
My iron is fine as can solder other things just fine. I also tried a different wire and the solder stuck very well and I was easily able to solder them to the connectors, this wire is just too thick so I have to use the other one. I have tried to get the solder to attach to the wire with and without flux but no luck.
These are the wires I'm using:
Specification:

Type: 30AWG
Total length: 280m/11023.6"
Material: Tin Plated Copper, Plastic
Outer diameter of single core wire: - Approx. 0.55mm
Diameter of copper core: Approx. 0.25mm
Temperature resistance: 80 degrees

Wire. (Dead link, also not available on the Wayback Machine.)  Similar to this wire.

This is the solder I am using:

Can anyone give me any tips to get it to stick? It's giving me a headache.


texts: How do I determine the fastest time between pulses I can measure?

texts:
I need to calculate the elapsed time between the rising edge of one pulse to the rising edge of the next pulse. This needs to be in a mobile environment, but I am not attached to any solution as long as its mobile. I have 3 questions:

What is the best way of calculating this time? I have thought about using PICs capture module, is there anything better out there?
How do I determine the fastest delta between rising edges that I can measure?
How do I determine the resolution (ie. 1 second compared to 1.0001 seconds between edges) that can be obtained, is it related to point 2?


texts:
Sorry if this question is a bit broad, or too part-suggestiony. I've been trying to find a good solution for over a month (and three board revisions) now, and I hope someone has an idea I haven't thought of.

I've got a sort of UPS system, in which I need to charge (at ~1a) a 12v, ~50ah lead acid battery (which has a continuous load of about 0.15a). I have a 15v or 12v supply that I can tap off of, and I have a micro that's monitoring the battery voltage anyway, so I can output a charge termination signal. Pretty basic, right? I first tried an LM317 CC system, but that dissipated way, way too much heat. Also it caught fire. I then spent way too much time trying to find a switchmode battery IC, but I never found one that was:

less than $20 all told
Not huge (pcb footprint wise, I only have about 1 cm^2 of board space).

I then tried to use a standard switchmode regulator with an adjustable current limit (the LM3663), but that didn't work, and I haven't found any other switching ic that met my requirements.


texts: What is proper power / driver size to use with an Osram Oslon Black Flat Led board?

texts:
I am trying to determine the proper power to send to my specialized LED board. The board consists of 6 Osram Oslon Black Flat Leds. I currently have 4 of these boards, 2 in each headlight. I have each headlight currently powered by a 12v 5amp buck boost regulated DC to DC power supply. I do not want to be sending too much current or power. This is a headlight LED board and thus will be used intermitted.
Here are some specs to the Osram Oslon Black Flat LEd:
Type: single die (lateral)
Binning: 8M7N (250 - 355 lm min.)
Rated voltage: typ. 3.05 V (min. 2.75 V, max. 3.75 V)
Forward current: 50 to 1,500 mA
Surge current (10 µs): 2,500 mA
Viewing angle: typ. 120° (at 50 % Iv)
And the data sheet can be found here
And here is an image of the board:


texts: System Generator: How to make an implementation a mathematical function through a ROM

texts:
I want to put in a ROM a vector of values I have in the workspace. Does anyone know how to do it?
Thank you to all possible references, articles or comments.


texts:
I want to learn about analogue circuit design and thought I'd start of reeeaaally simple, with a circuit where you connect the battery and the LED turns on. I've been looking on digikey.nz for the right components but they don't seem to offer the kind of LED I'm looking for.

I want a small LED that's simple to work with, something that looks like this:

Does anybody know what the name of this kind of LED is, and where I can get one? I've been trying to find a place to order one online but can only find lines of christmas lights, LED bulbs, or weird complicated circular things.


texts: PAM2804 Lithium-ion single cell LED driver fails

texts:
UPDATE (2021-Jan-16) - All working as expected - Project link for anyone to build or do as they please.
PAM2804, I've been trying to use this chip for a single Li-ion cell flashlight project, but it does not work for me. I've designed 2 PCBs so far, but both failed.
I'm driving a Cree X-Lamp XML @ 1A.
I can see voltage on the output, but the LED does not light.
1st PCB was a 2 layer; 2nd PCB was a 4 layer with 2 inner ground layers.
Anyone kindly point out what I might be doing wrong please?
Components used;

My schematics:
**

For testing I have only solder the PAM2804 side. For now ignore reset of the circuitry please.
Direct power injected from a charged Li-ion battery at C1.
Sorry I have no oscilloscope at the moment. It's on it's way.
**

My 2nd PCB:

Voltages at;

U1 Pin 1 - 4.092v
U1 Pin 2 - 3.258v strange this is GND
U1 Pin 3 - Starts at 3.3v and goes down to 3.089v and stables.
U1 Pin 4 - 4.092v (same as C1 voltage)
U1 Pin 5 - Starts at 3.475v and goes down to 3.369v and stables.
C1 - 4.092v
C7 - Starts at 3.3v and goes down to 3.085v and stables.


texts: Signed representation of negative numbers in Verilog HDL by Samir Palnitkar

texts:
I'm reading about signed number representation and the book says

-6'd3 // 8-bit negative number stored as 2's complement of 3

Is there a reason as to why a number declared as 6-bit is stored as an 8-bit?

I don't think it is the "sign bits" taking extra bits, as it clearly says 2's complement is used. Even if it is sign bits, then only 1 bit would be required.


texts:
Through-hole components are not designed to be busbar mounted. But I have the need to use "laminated" busbar because of some factors (among others):

High current
Small parasitic inductance

Power PCBs are also not available for small production, or even not manufactured at the thickness intended. Also they will present some problems to mount too.
Using modules or packages like SOT 227 is not an option now because of the cost, and the added terminals inductance of modules.
I have TO-247 IGBTs and I'm studding ways to mount then to the busbars.
Some of the options:

Soldering: As the busbar will conduct much more heat it seems to be difficult to make a good solder without overheating the package (at least with cost effective soldering methods).

Pressure: Making some pins in the busbar and pressure mount the pins. But with what method? Also it should be removable to allow for maintenance, even if the connector needs to be cut.

Terminals connectors like in this project:

(from http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-i/)
This project uses the connectors only at some components.
The problems applying that to the TO-247 package transistors is the spacing between leads. The TO-247 has near 5mm pin to pin spacing, so the connector should be small if not to bend the terminal.
(Yes this will add a little parasitic inductance, but probably less than modules).
Any suggestion? Thanks.


texts: Net names aren't shown in EAGLE PCB layout

texts:
I created a PCB in EAGLE Cadsoft but Net names are invisible in PCB layer though all layers are selected to be visible. Any suggestion?
 (I need names to be shown like the "jp1" on top left corner of PCB layer as in below image)


texts: Current regulation - oscillation problems

texts:
I'm playing around with opamps trying to build power supply for lead acid battery charger, but in general I want to learn a bit about opamp based design. I'm stuck with constant current mode.

I'm trying out various current sense amplifiers to sense current on the high side. I'm not using OA2 and M3 per se - they are packaged into current sense amplifier IC such as LTC6101, LTC6102, MAX9938. I've tried differently designed voltage output current sense amplifiers like AD8218 too.

So, OA2 and M3 are here to designate current sense amplifier IC that outputs voltage proportional to voltage drop on R1.

I've tried LM358, LM8272, LM8262 as OA1.

My problem is that whatever I do, it either oscillates or does not limit current from some point.

I've tried slowing down OA1 by adding a capacitor on negative feedback path or a low pass filter after current sense amp output, but then, either oscillations become worse, or, when I increase the load, OA1 stops decreasing its output at some point, voltage at output of M1 becomes fixed and I have no regulation.

The best I could achieve was by using high speed opamp such as LM8262 as OA1 and small (1nF) cap across the current sense amp output. On the maximum load, the system was oscillating a bit, but average current was somewhat right.

When I've tried doing low side current sensing using the same type of opamp for current sensing and for regulation, it just worked.

My suspicion is that mentioned current sense amplifiers are not designed to work in linear regulation, but rather as current feedback for some ADC to read (at least, all of them have such application as typical in their datasheets). What I suspect is that phase shift from them is too big. Am I right?

Can anyone recommend a better option for high side current sensing/limiting or some procedure for stabilizing the circuit?


texts:
I bought this nixie clock kit and it is partially working.  One of the issues I'm having is that the 6th hour does not light up so if the clock is at 06:00:00 to 06:59:59 the 6 will not light up for the duration of the hour.  At one point after fiddling around with the positioning of the tubes, it is the 9th hour that has this problem.  The 6 (and the 9 at one point) works in the minutes and seconds.  No it is not the tubes.

The other issue is that the time starts lagging by a second every other day.

I've followed the instructions and built the kit but I'm not too well-versed in electrical components.  What exactly is controlling the time functionalities? I am thinking it is software related and thought it was the MOSFETS IC2 and IC3 that controlled it but apparently all the MOSFETS do is regulate the voltage... I may have dropped the IC2 MOSFET at one point and thought that it may have been damaged which caused this abnormal behaviour but since it only controls the voltage, that can't be it...

I have contacted the seller but he is not offering much help.  If any one have experience with nixie clocks or this kit in particular, any help/pointers/advice would be greatly appreciated.


texts: How to solder large gauge wire to terminal

texts:
Apologies if this is not an appropriate question or if there are answers elsewhere, I am looking for a definitive answer which I have been unable to find.

I want to solder some heavy gauge, insulated, multi-strand copper wire (8 AWG) to a tinned terminal.

What would the correct tools and technique be for this?

I have tried 10's of combinations of solders, soldering irons and fluxes, but always end up with what looks like a dry joint, and/or not all the strands could be soldered, presumably because of what appears to be a residue on the strands from the soldering.

I would like to avoid using a flame torch if possible to avoid damaging surrounding parts. (Or perhaps some how shield surrounding parts from the flame.)


texts: Non-mechanical load suggestions for a 12VDC / 6A PSU?

texts: I need to provide a load for the 12VDC/6A power supply. I used a small motor before, but something less mechanical (more reliable) like a light or (anything that's not mechanical) would be ideal.


texts:
I read the Chris Basso APEC 2010

I don't understand why the C1 can connect the Op amp output directly when using the TL431.
Because the TL431 output has a BJT.


texts: Questions on connecting and using the RS485 MAX14783E transirver

texts:
Task:

Using Arduino UNO, obtain various parameters from the ABB B21 112-200 electric energy meter, as well as send settings to it.

This meter has an RS485 interface (ModBus RTU) with terminals A, B, C

To connect, I will use the MAX14783EASA+T transirver.

The distance between the meter and the transirver is within 50cm.

There is no ready-made module with this transirver, so I will design my own.

My wiring diagram:

As a basis, I took the design of the MAX485.

The questions are:

Pull-up resistors are placed on line A, B to protect against
floating contact.
     What determines the choice of the nominal value of these resistances? There are 20k resistors on the MAX485 board, although
the line length is not known there. I found various options used:
560 Ohm, 1k, 20k.
     The datasheet indicates:

  True Fail Safe The MAX14783E guarantees a logic-high receiver output when the receiver inputs are shorted or open, or when they
  are connected to a terminated transmission line with all drivers
  disabled. If the differential receiver input voltage (A–B) is
  greater than or equal to -10mV, RO is logic-high.

The lines RO, RE, DE, DI are pull-up by 10k resistors. This is a
good decision?

I learned that RE and DE can be combined together and switch the
transirver from read mode to send mode using a single contact of the
microcontroller. Why is this done? To save contacts or increase
reliability?

The MAX14783E has built-in hot-swappable circuitry. I would not want
external pull-up resistors to somehow influence this.
Does the -7V + 12V range comply with the A-B voltage standard for
the RS485 bus?

This transceiver is rated at -8V + 13V. In the counter passport I
did not find the voltage range on the RS485 line.


texts: Hardware-level detection of USB3.0 vs USB2.0

texts:
I'm designing a USB battery charger, and I'm trying to use simple hardware (ICs are fine, just nothing that I have to upload firmware onto preferrably) to detect whether or not the USB socket I'm plugging the device into is USB3.0 or USB2.0, so I can safely determine how much current I can draw. I'm using a BQ2439RSER chip to determine if the socket I'm plugged into is a Standard Downstream Port, Charging Downstream Port, or a Dedicated Charging port. However, I'm running into trouble coming up with a simple way to check whether or not the host port is USB3.0 or USB2.0.

My initial thought was to check for pullups/pulldowns on any of the extra USB3 pins not present on a USB2 socket, however in all of the schematics I've looked at, the superspeed differential pairs have blocking capacitors on them (see page 11 of this datasheet http://www.ti.com/lit/an/slla329/slla329.pdf). My next though was to just check to see if the GND_DRAIN pin was connected to the common USB GND pin, but this post (USB3 with fewer wires) says that GND_DRAIN and GND are not necessarily going to be the same.

I don't need any of the RX/TX pairs to work or transmit data, I'm only interested in identifying maximum allowable current, and drawing it. I'm aware that some devices will limit me to 100mA, but in my experience these seem to be few and far between these days, so I'm willing to test the prototype without enumeration (worst case scenario I'll ad an FT232R host controller to take care of that later, but I'm trying to keep this as simple as possible).

Thanks for the help


texts: I am making a prototype of a Clip-on Christmas tree light.  It has two lights with a 3v battery attached to the lights (because the lights are 3v) and a clip in the middle.  I need to find a smaller battery to make it more attractive and salable.  Can anyone tell me what the smallest battery I can use for these two lights would be.  P. S.  I am not an EE nor do I understand anything about electricity or electrical math, so please answer in very simple language.  Thank you.  I intend to market these to commercialization through a small business development center and I need to make a unit that is more presentable than a battery with electrical tape on it.  Any ideas on that would be appreciated as well.


texts: Charging 35V 470uf capacitor with coin cell

texts:
I want to charge a 50V 470uF capacitor up to 35V with the smallest battery possible. Can a coin cell do this 3000 times? Possibly a 2450 or 2477 coin cell? Also, can the capacitor be fully charged from 0V to 35V in 6 seconds.

Edit after some discussion:

How to boost from 2V-3V to 35V (acceptable range 30V-35V) with 24ma load (6 seconds recharge or better), with AAA or AAAA?

By now i'm using this scheme, PIC impose Q1 period .135 and Duty .12, up to 32V, i read with the meter 25ma charging and 12ma when fixed on the top.
There is somewhere a heavy load on the battery, that goes down in few cycles and don't restore.  L2 is the solenoid, S2 is the switch that discharge the capacitor into the solenoid. Led blink when fully charged.

This is the pic program i'm using:
Pic Program

I uploaded the asm code i'm using: VRCON set V limit (0xa4 is near 30V-35V). When connected to 3V coin cell battery, i must increase VRCON value to 0xa6 to arrive to 30V, .35period, .12 DUty; on the meter i read a current flow of 25ma charging and 10ma while on top; i think it's not good for coin cell battery.
12F683 has function down to 2V so i need at least 3V to start with, an di'm not sure if 3V it's enough to fully activate Q1 (i'm asking why i have to double the voltage reference from pin6 to gain the same V)

With 9V battery i used this board:

With .14 Period, .3 Duty i obtain a 34V recharge about 14seconds or less, 14mA while charging, 9mA while on Top, less than 5mA when not recharging.
Applied the load, 9V battery has 9,20V, after 80 cycles spaced into 2 hours the battery is 8,60V. imho it's too much. I cannot read the initial current draw with the meter, it's too fast.

Thanks to the courtesy of another user, Bobledoux:

  FET drive frequency = 1,000,000/Period.  So you are using 7.4Khz.
  That is a very low frequency for a converter. Q1 gate should be a
  perfect square wave, coming from the PIC PWM. Q1 drain depends on
  whether you are fully turning on Q1.  To see that you need to be
  looking at the wave on an oscilloscope.


texts:
So, here's the scenario:

I have an Arduino and an SD card.  Unfortunately, I don't have one of the fancy shields, and I don't have the time to order one.  As we know, Arduinos run on 5V, and SD cards run on 3.3V.  I was thinking that I could use a series of voltage dividers to get the data going from the Arduino to the card (MOSI, Clock, SS) down to the correct voltage, but I'm not sure about putting together a step-up circuit.

Would I even need a step-up circuit for the MISO line, or could I just feed it directly into the Arduino?  Does anyone have any ideas other than the ones I mentioned?


texts: Change the rotation of single-phase (split-phase induction motor)

texts: In order to change the rotation of the single phase induction motor, the connection to one of the stator windings(starting winding and main winding) is reversed. But later we cut the starting winding ,so how is it possible to reverse the direction of rotation of the single phase induction winding?


texts: Are USB protocol and connector free or are they patented?

texts:
For a hobbyist developing a device, certification is not pleasant.

I am wondering if implementing USB in any way is patented or needs a certification?

I am concerned about both protocol (USB-2,3) and headers (USB-A, B, C).

I am also curious if the processor producers should pay to use USB output for their chips?


texts: diode equivalent circuit model AC analysis

texts:
I've understood the small-signal analysis for the diode, like how is the value for rd derived. But here are somethings i don't understand:

How is capacitance of the diode dependent on the frequency of source?
Why is capacitor in parallel with the resistor? Why not is series?
How is all this different for reverse biased? With operating in high and low frequency?


texts: Altium Designer: Is it possible to switch layers in an entire library at once?

texts: I am using some integrated schematic/footprint libraries that I downloaded from the internet in a PCB project I am working on. In these libraries, they put 3d component bodies on mechanical layer #1, while all my other libraries have 3d bodies on mechanical layer #13. Is there an easy way to take everything in the library that is on mechanical layer #1 and move it to mechanical layer #13 without having to edit each individual footprint?


texts: reducing(or stopping)the pop when a speaker is switched

texts: Is it possible to stop or reduce the popping sound which is emitted from the speaker when you turn on and off an amplifier? i am using a PAM8403 connected to a 4ohm speaker. i am switching using a low side mosfet connected to an arduino. Thanks.