texts: Need to control 100 Watt Pump With 15 Watt Float Switch

texts:
I am an inexperienced hobbyist So My Question may be obvious, but thank you for the help.

I have a 12 V battery, which is powering two 12 V pumps. It is a 100 W pump which runs at 7 A on average (Depending on required Pressure), and another Pump, which runs at 3 A on average, but both pumps can peak under pressure to a combined continuous amp draw of over 15 A, and the current load also peaks on start-up.

My aim is to have the battery powering the two main pumps, the less powerful pump to be controlled on and off by an rf relay switch and a motor speed controller, and the more powerful pump activated by a mini water level switch as well as a motor speed controller.

My problem is that the mini water level switch is listed as having a 15 watt power rating, and 1 amp contact current. It therefore does not allow the more powerful pump to start or stop when open or closed. If the pump is running and the contact switch opens, the pump will cut out, but if the relay then closes the pump cannot restart again. It simply gives off a quiet click sound.
Is there a component I can use, like some sort of controller which will allow me to lower the current through the float switch, whilst allowing full power to the pumps?

Again I am aware that this is likely a very simple question but I very much appreciate your time and help as I have never studied electrical engineering and am learning as I go. Thank you so much for your time and response please let me know if you need further clarification. Joell


texts: Is there any major difference between using STM32F103C8T6 + ST LINK V2 and using Tiva c concerning debugging?

texts:
I have started learning ARM microprocessors and I just wanted some real board to get more comfortable with what i'm learning and I have two options : Getting tiva c launch board or using STM32F103C8T6 basic development board with ST LINK V2 for programming and "debugging".

I know that these boards use different processors (M3 and M4), but what i'm really worried about is the ability to debug using them. After some googling I knew that "st link v2" make the debugging stuff and I have actually found option in KEIL IDE that supports debugging using "st link" which seems OK but I still need to check if there's any difference or something i'd miss if I choose any of them over the other.


texts: Coaxial cable terminology : how to read?

texts:
I need to understand the nomenclature used for coaxial cable.

For example: UT-085-SS-SS, or UT-085-SS, or UT-085-NbTi

As far as I understood, the number 085 here is the total diameter of the cable in inches (thus 0.085 inches of diameter). The SS-SS means that the material is Stainless-Steel.

But how can I read it in general and not guess it ? I tried to find on internet but I didn't manage to find a place where it is well explained.

For example what is the difference between UT-085-SS-SS and UT-085-SS: both are in Stainless Steel apparently, but why one has it written twice?

What does the UT means?


texts: How to read data from an .mif file in Vivado?

texts:
My knowledge on the subject is bare-bones. I created a .coe file and used Block Memory Generator to get an .mif file. I need to store the contents in the block memory and then use it. Following is my code:

module read_file;
reg [15:0] music [0:255];
initial
$readmemh("blk_mem_gen_1.mif",  music);
integer i;
initial begin for(i=0; i<16; i=i+1)
$display("music[%d] = %h", i, music[i]);
end
endmodule

As you can probably tell, I have no idea what I am doing. Please guide me through and point me to some resources if you happen to know some.


texts: Inverting Opamp on Noisy Ground. Would an LC filter help?

texts:
Alright, say I have this Inverting Opamp, but it so happens the positive input to ground is also connected with another sub-circuit that happens to produce a lot of noise (no pun intended):

simulate this circuit – Schematic created using CircuitLab

Now, say there's nothing I can do about the noise source, would it help if I were to put an LC filter on the positive input to ground. I would also like to use a common choke for the inductor, with the other side going at V_DD:

simulate this circuit

Or would this just be detrimental to the performance of the opamp?

Would there be a better way to filter/stabilize the ground leading to the opamp? There's also those Crystal, Ceramic, Saw filters that I know nothing about... Can you guys suggest the cheapest solution?

EDIT:

In response to Andy's comment, the V1 above has been added to denote the voltage source of the black box (It was not there in the first diagram). I'm not a 100% sure, but the the black box has a Boost Converter and the inductor might be the one causing the noise.

The Opamp by itself works well when powered by V_DD. The black box does so when powered with V1. The output of the opamp only appears after I ground it with the black box.

EDIT:
It has been misunderstood by some that whole LC-common-choked filter are all at ground, so I'll clarify it:

simulate this circuit

simulate this circuit

but to think of it, I should've provided this diagram and not let the ground of the opamp "dangle" around.


texts: What does term "connectivity attributes" mean in AM3359 Cortex A8 processor (used in Beaglebone)?

texts:
Please explain the meaning of the term "connectivity attributes" in context of UART in AM3359 processor. I found the term while reading its Technical Reference Manual (TRM).

It is not defined in its TRM, neither could I find it on Google.

I am using BeagleBone (not BB - Black)

Link to TRM


texts:
I have a differential signal up to 1.5 MHz and have to transform it to a single ended signal.

I have found this amplifier which has a BW of 2.2 MHz and should therefore be okay for this task.

The manufacturer also offers a simulation program, where I've tested this
where \$R_f = R_g \$ and \$R_1 = R_2\$.

The input signals are 500mV pp and have a common voltage of 1V. Is this the right way of transforming a differential signal to a single-ended one?


texts:
I need to divide an integer by an integer in one clock cycle. how should I do this? I have a function for it I found on the internet but it always returns one.

function  divide  (a : unsigned; b : unsigned) return integer is
    variable a1 : unsigned(15 downto 0):=a;
    variable b1 : unsigned(15 downto 0):=a;
    variable p1 : unsigned(16 downto 0):= (others => '0');
    variable i : integer:=0;
    begin
        for i in 0 to b'length-1 loop
            p1(b'length-1 downto 1) := p1(b'length-2 downto 0);
            p1(0) := a1(a'length-1);
            a1(a'length-1 downto 1) := a1(a'length-2 downto 0);
            p1 := p1-b1;
            if(p1(b'length-1) ='1') then
                a1(0) :='0';
                p1 := p1+b1;
            else
                a1(0) :='1';
            end if;
        end loop;
        return to_integer(a1);
    end divide;


texts: How can FPGA differential signal use lower power when it has two lines instead of one?

texts:
I am a bit confused about differential signaling on FPGAs. I am trying to figure out how does power dissipation in FPGA differential signaling compare with power dissipation in FPGA single ended signaling.
As far as I am aware, the differential signal mechanism is emulated i.e we may not have a true differential signal buffer in the FPGA but rather drive two single ended buffers in opposite directions. How does grounding affect this mechanism?
I/O buffers dissipate power when they switch output state. With differential buffers, there are always going to be two buffers that are switching simultaneously. Shouldn't this cause the use of differential signal to dissipate more power than single ended signals?


texts:
I have a sustain pedal (which is just a momentary switch!) with the wrong polarity (according to the device I'm using it with) :

circuit is CLOSED when pedal is pressed
circuit is OPEN when pedal is released

I would like the opposite.

Is there an electronical solution to invert the behaviour of such a switch, with only passive components (without having to use a battery-powered component, etc.) ?


texts: Can I reduce volume of active buzzer with arduino?

texts:
I connected arduino's 5v pin to active buzzer's positive. And it makes a loud noise. I tried connecting arduino's 3.3 v pin and yet the active buzzer is making a loud noise. Is there a way to reduce this volume? I am new to electronics and I am playing around with programming and electronics and I don't want to disturb my neighbors with this sound. Should I use some resistor?

If nothing works, I will probably just tape the top of the active buzzer and hope the volume is less.

I am using the below circuit from a tutorial.


texts: Is there any statistics on processing time of printf statement?

texts:
printf is often used across the board in embedded systems for many different reasons. Besides just moving characters to an output stream there is a process involved to convert numbers into a specified format and also a buffer that is filled up from which characters are transmitted to a terminal one at a time.
Among different conversions e.g integer to string, float to string e.t.c and the time taken to write characters into a buffer and for a character to leave the buffer, how long does each process take?
I understand that the answer really depends on what hardware system we are using, I just need rough figures from any real world example. I find the printf calls to be REALLY slow on any system and wonder why they are so slow at all.


texts:
I've got a computer program that monitors an audio signal. When the audio signal drops below a certain threshold it triggers an email to the appropriate person.

This same program can either make a post request to an url or close a relay via serial.

I need to wire up a light in another part of the building that will become on when this happens.

I am going to use single led road flares I found on amazon to be the signal light. They require 3 AA batteries. I'd like to bypass the batteries or the button on the light and trigger the light from the serial port.

I've got 5 different sources to do this for.

Whats the best way to accomplish this?

I was thinking I would need a relay and then I would probably run cat5 to the lights. Cat 5 because I have tons of it here. But I could also buy some 18 Gauge 8 Conductor wire an use that instead to make one run.

So the serial ports would wire to the relay no contacts when it gets the voltage it would close the relays and trigger the lights. Thoughts or suggestions?

Thanks


texts: High-gain omnidirectional antennas for Wi-Fi mesh

texts:
Hopefully this is the right SE site a question of this nature.

Basically what I want to do is set up a wireless transmitter using a high-gain omni/directional antenna as a test-bed mesh network between my brother and I. The range is well within the 30+ miles I see advertised on antennas for sale. What I don't understand is the frequencies and channels they advertise. 2.4Ghz 802.11g seems to fit within UHF, but I haven't found any clear indication that this is true, and I can't escape feeling like I'm oversimplifying this, or missing something.

PS: I'm happy to read any material supplied if an explanation is too verbose to propose here.


texts: How to estimate the series resistance for this zener regulation?

texts:
There is a variable load that draws current between 1mA up to 1.5A.
I want to supply the load with almost constant 4.2V(precision not improtant).
If I only have 5V supply I thought I can perform the regulation as follows:

But how can a proper Rs be calculated in this case? Or will this never work?


texts: DC ripple stabilizer. 3rd order low pass filter. How to supply op-amps properly

texts:
I have a cheap ac-dc adapter, but it outputs DC with a ripple.
It has variable output, so it can output 12, 14, 17, and so on up to 32V.

I measured output of ac-dc adapter with an Agilent multimeter, and I was getting rather chaotic DC voltage. It would be around 16.9V to 17.2V, but it wouldn't "consistently" oscillate at some point or for the same amount of time.

Like it'd be around 16.880V and then jump around that value (±50mV), sometimes stay steady.

Or rise up to 17.120V and be there etc. I tried using a voltage regulator - and it worked, however it would output at fixed voltage level - 12V.

I don't need a fixed voltage output. As I would be using this adapter with various circuits, so buying a voltage regulator isn't an option.

For instance, I used this cheap ac-dc adapter on an old walkman audio player that needs 12V at the input, and there was a lot of noise in the headphones due to DC ripple.

I managed to simulate a 3rd order low pass filter, and it seemed to smooth out DC, so I get this straight line of DC with ~0Hz.
360nF was chosen per article, so that cut off frequency is around 45 hz. I tried changing capacitors to 1.6uF which corresponds to cut-off of 20Hz, but it was the same.
Also, should I try to seek another formula, since I'm unlikely to have same values for all three capacitors IRL?

Anyhow, if I to build this circuit, how do I power up my LM358 op-amps?
I thought I'd just supply op-amps from the ac-dc adapter that has DC ripple, but then the filter stops functioning properly and I no longer get smooth DC at the output of the filter circuit.

Does 3rd order low pass filter require separate, external, smooth DC (like from a lab bench supply) power? Am I supposed to rely on passive low pass filtering then?


texts: Use modified USART for a one-wire bus, one master and 400 slaves on a 400 m wire?

texts:
I use the normal ATmega UART interface, but disable the TX part (make it high impedance). To have more push-pull power for a long bus, I use two I/O pins for TX; the PNP and NPN transistors will be actived in the order that prevent a short (I usually use this PNP/NPN pair to drive a MOSFET at high speed, and it worked OK). Only one device can drive the bus at a time, others deactive both BJT transistors to make it high impedance.

I have to bitbang the TX part, but I think it's not very difficult (correct me if I'm wrong). The bit rate doesn't need to be high, but the lowest possible the UART interfaces can receive.

Does this sound feasible? I need your thought.

The NPN transistor's emitter connects to GND, and the PNP transistor's emitter connects to 5 V. There is a 220 ohm resistor at the bases.


texts:
I'm in desperate need of help here! No matter what I try, I can't seem to get this working!

I'm trying to drive a signal transistor with PWM on an AVR ATmega32. My PWM signal looks as it's supposed to:

I have it setup so that I can vary the duty cycle of the signal, and my initial thought was, that I would be able to control the amount of current being piped through the transistor.
The idea is to use the small signal transistor in conjunction with two MJ15003 power transistors for regulating power in a high current power supply.

The crude schematic looks something like this:

All devices in the circuit share the same ground, but sometimes when I measure the base voltage on the signalling transistor (TIP50) it just sky-rockets above 15V! What is going on!?

The MJ15003's require 5V @ 5A base current, so I figure my signal transistor is too small.


texts: Operation of tuned collector feedback oscillator

texts:
I am trying to understand the following tuned collector feedback oscillator extracted from here using LTSpice. I understand that L1 and C1 creates the resonance at the oscillation frequency and L2 provides the feedback.

However, The voltage at the output (V(C3)) is not sinusoidal as expected. Please refer to the following waveform.

If I understand it correctly, transistor goes to saturation (edit: because of high gain).
When capacitors C2 and C4 are removed (as suggested in comment), output become close to sinusoidal (refer the following).

I am not sure why the circuit behave this way, and what is the need of C2 and C4?


texts: Loading effect question about transformers used in split-supplies

texts:
This question is about designing a split power supply from a transformer and a rectifier. I'm trying to understand why a full-wave bridge rectifier with a center-tapped transformer is not affected from loading comparing to a not center-tapped one.

In below schematics both configurations are simulated in LTspice. The only difference is the one on the left side uses the transformer as center-tapped and the one on the right uses the transformer the transformer as usual.

X and Y represents the terminals of the split supplies. Both supplies gives the same output at X and Y terminals without any loads. They both output around +8V and -8V when no loads attached. But as seen in the schematics, when I load both supply terminals with two different loads 1k and 100 ohm, the output voltages at the X Y terminals becomes as:

(please left-click to enlarge the schematics)

For the center-tapped configuration the output at X Y terminals:

For the non-center-tapped configuration the output at X Y terminals:

It seems like one should use a center-tapped transformer to create a split power supply otherwise the loading corrupts the output for non-symmetric loads.

My question is: I can verify this by LTspice but I do not understand the reason behind. How can we explain this difference logically?


texts: TRIAC turning on asymetrically by itself when it gets warm

texts:
I've got a simple triac phase angle controller which is very similar to the MOC3021 data sheet app circuit. Most of the time everything is fine. The circuit looks like this:

The triac is a BTA06-600B (ie standard sensitivity, not snubberless). The opto snubber circuit is the same, the triac snubber circuit has a 0.015uF cap and 270R resistor.

I've got a problem always occurs when the triac gets to about 75C - it turns on all by itself with a distored asymetrical waveform like below - turning on for part of one half of each cycle. This generates a waveform that the connected motor doesn't like at all - and it seems to stay there forever until the motor burns out.

Once it cools down a bit it turns back off. The load doesn't seem to matter - it happens with a 30W fan or a 4A fan.

There is no gate drive - I've tried shorting out pins 1/2 on the Opto but it makes no difference. Also, when I heat up the triac the opto isn't getting warm - and I can cause the problem to appear with heat.

I can make the problem occur by heating the triac with a hot air gun though I don't think that is the only cause - it happened this morning a few times without much heat but we then spent hours trying to replicate the output with no success.

In the field this "other" cause is what is happening to some units - the triac shouldn't get to anywhere near 75C in normal operation as it is driving a 50W/0.22A fan and is mounted on a heatsink.

Why does the triac turn on by itself?

[update 1] It seems the problem is restricted to some triacs - I pulled some more units off the shelf and they were ok with the heatsink > 100C (110C according to my multimeter and sizzling hot according to my wet finger!). The one that worked was a different date code.

[update 2] The high temperature testing was done with a hot air gun not from the load/lack of heatsinking. In normal operation it is dissipating about 0.022W and is mounted on a heatsink. I've been hitting it with spray freeze & a hot air gun trying to make it misbehave.

[update 3] I have tried 1k, 470R, 270R between the gate and A1 - makes no difference.

[update 4] I'm not sure it is dv/dt - the load is "off" (ie opto not driven) then when I heat up the triac it turns on by itself and stays on until it cools down again

[update 5] I know the 110C/etc temp is hot - perhaps too hot. My point with that comment is that even at that temperature some units are ok while at a temperature much lower than that others are not. The faulty one "fails" at something like 70C while the good ones are ok at 110C

[update 6] I have concluded that there is just something wrong with this particular triac - I've tried to replicate the problem with a heap of other units and can't. Asmyldof - it's not the spike causing the problem because the triac can be off, heated and then the problem occurs - ie the heating is causing the odd waveform, not any motor spikes.


texts:
I'm wondering why I don't see ESD protection for ground (can you even protect ground from ESD?) - If there is a large electrostatic discharge straight onto the ground plane wouldn't that voltage spike of the ground level damage all the electronics using that ground ? Wouldn't it be the same as zapping any other pin of the IC with a huge voltage spike ?

Thanks in advance!


texts:
In my robot, I plan to have a GPIO pin on my Raspberry Pi connected to the insertion detection pin (pin 3) of a barrel jack (schematic here) so that my code can tell when the robot is externally powered. The plan is to have the GPIO internally pulled up when the robot is on battery power and grounded otherwise.

The problem is that for power, the Pi is "grounded" to the negative output of a buck converter (link here) that's connected to the same barrel jack on the input end, meaning that the Pi's power and the GPIO are grounded to different things.

Is there a substantial voltage difference across the input and output terminals of the buck converter? If so, then I think this would mean that the voltage drop from the GPIO to the barrel jack ground could be greater than the 3.3 V the GPIO is rated for. This is because the Pi and its GPIO would be grounded to different reference voltages.

The buck converter will step 19.6 V down to 5 V in order to power the Pi, and the GPIO pin is internally pulled high.


texts:
Suppose I have a circuit with voltage 4V and current 1A. By \$P=I~V\$ the total power across the circuit is 4W.

I have a \$20~\Omega\$ resistor and want to calculate the power loss over the resistor. By \$I^2 R\$ that is 20W.

This doesn't make sense to me. If the total power across the circuit is 4W, how can I lose 20W of power over the resistor. Where is my understanding wrong here?


texts: Basics: Raspberry Pi Zero w with relay. Relay trips without input

texts:
I'm not quite sure how to word this so I don't know how to search for it to see if there's already been an answer. I am an uber basic noob can't even draw out schematics, so sorry in advance.

I have a Raspberry Pi Zero w with a 5v relay board. Pi is supplied with 5v. The relay is connected with 5v and GND to the 5v and GND of the pi. I then have a lamp spliced into the relay to be turned on and off via the pi.

Edit

There is more to my setup. This is when the issue started happening. I put in a momentary push button. It seems like the input is extremely sensitive.

Here is my issue: If I turn on or off the exhaust fan in the bathroom (for example) or if I turn on a hair dryer or another fan, it will turn on the lamp. It doesn't happen all the time. I assume it is some kind of surge. I just can't quite figure out how to make sure that doesn't happen.

I've tried adding resistors, but that didn't. I'm not sure if this is a capacitor thing.. That's about the time I realized I have no idea what I'm doing and so I figured i'd ask!

Edit #2

Ok, I did by best to draw up a schematic using fritzing.

Here is a picture

EDIT 3 And fix*

I accidentally my raspberry pi and caused it unsafe power off which corrupted the SD card. I had an ESP8266 laying around that I decided to use instead. The issue was indeed a floating state as I had the same issue with the ESP. Using a 10k resistor to ground fixed the issue. Also, using the ESP8266 is MUCH better for this application than the rPi!!


texts:
I need to review some physical layers used in OBDII, a very common interface communication of vehicles and used as interface in a automotive scanners. I don't need exactly to know how the protocol works, more precisely speaking, I need to know the ICs and actual panorama of these protocols, for example, actually, I use a SN65HVD251D as a transceiver for CAN physical interface, however, I read that in 2015 was published the standard ISO 11898-1:2015 that specifies what is called CAN-FD and allow data rates greather than 1Mbps and payload wider than the allowed in previous CAN standard. So I would like to know if there is newer updates to other protocols and and to the ICs that I use. I will put here a panorama of what I know about this at the moment:

CAN Physical Layer : In 2015 was published the standard ISO 11898-1:2015 that specifies what is called CAN-FD and allow data rates greather than 1Mbps and allow payloads wider than the allowed in previous CAN standard. I found ICs that allow up to 12MBps like the ADM3050E .

J1850 Physical Layer: J1850 allows for the use of a single or dual wire bus, two data rates (10.4 kbps
or 41.7 kbps), two bit encoding techniques PWM (pulse-width modulation ) or VPW (variable
pulse-width modulation). Actually, I use comparators together with a microcontroller tom implement PWM alternative, so a simple comparator is sufficiently. As a solution to VPW alternative I use the MC33390 IC, this IC is hard to find and I didn't found an alternative to it.

ISO 9141 Physical Layer: Actually I use a L9637, I know another IC, the L9613, but as I culd see, they are similar and the difference is about Voltage tolerance of power supplly.

About CAN, was relativeley easy to find out that my approach using SN65HVD251D to CAN physical layer can become outdated soon. But I really don't know how to know it, in a similar way, about the others protocols.

Does someone has these informations or know a manner to get these informations about these protocols, like updated versions or something similar ?


texts: I have been seeing a video about how boost converters works. I was wondering why one would choose a boost converter system over a transformer to step up voltage (except the fact that boost converter is for DC and transformers are for AC->as I understood it).


texts:
I found a schematic which had this bit of circuitry between the +9 V (which apparently the author assumed to be > 9 V, more like 10-11 V) barrel connector and the +9 V supply rail.
I tried to simulate what's happening in LTspice, but I don't think I modelled it right, as even the forward voltage drop of the polarity protection diode is not visible in the output. My current guess is that the base-emitter voltage is driven to saturation (somehow) so that it's just a ~1 V linear dropdown regulator?


texts: How to make a voltage vs amp-hour discharge curve

texts: This is in regard with another question of mine, how do you make a discharge curve with the y-axis of voltage and x-axis of amp - hour?


texts: Need help with hardware and software config on PIC12F675 to light up an LED

texts:
I'm trying to get an output from a PIC12F675, but I can't seem to get it to work.
Here is my hardware setup that I breadboarded:

And here is my code programmed using a PicKit2:

#include <htc.h>
__CONFIG(FOSC_INTRCIO & WDTE_OFF & CPD_OFF);

void main()
{
    TRISIO = 0b111101;
    GP1 = 1;
    for(;;)
    {
        ;
    }
}

What am I missing here?

Any help is appreciated, Thanks!

EDIT:
fixed code, but still not functional

    TRISIO = 0b111110;
    GP0 = 1;
    for(;;)


texts: Saving component library preferences in KiCAD

texts:
I have a local component library that I use in most designs. I've been adding this to the library list in Eschema for each new design because I can't figure out how to add this permanently via preferences or something. Is creating a template the right/only way to make this permanent, or is there a better solution.
Thanks.


texts: What is the 'best' way of communicating with small microcontrollers/devices?

texts:
var best = "simple & cheap";

I have a server in my apartment that I have an XBEE hooked up to. I use it to communicate with another XBEE plugged into an Arduino. I am trying to hook up many things to my server, but I don't want to have 10 XBEEs hooked up to 10 Arduinos, because that's expensive. I also don't want to have wires running all over the place to hook up sensors/etc to my one Arduino.

My first thought was to buy some Arduino Minis, and wire something like these to them:
RF Link Transmitter
RF Link Receiver

Would there be a betters solution? Do you have any particular resources I should go read? The endpoint devices would have to do things like read sensors, trigger switches, and even display data. Also, I'm not sure if I would use batteries for these or try to get power adapters for these.

Please comment if I should include more information about anything! :)


texts: Festival light sculpture LED power question

texts:
Hi im looking for some guidance for a temporary outdoor lighting installation at a festival. I want to run 18 x 10m lengths of low voltage LED fairy lights these ones.

I have some large 12v batteries and a step up dc dc boost converter like this Can i just simply boost the 12v to 31v required by the lights and run all 18 strings of one supply? operating times will be no more than 6 hours in a 24 hour period. I was told each LED is 0.007W so with 100 leds per string i will have to run 1800 LEDS. Whats the best way to achieve powering this with 12v?

I have some basic electronic skills/soldering etc..

Many Thanks
Al


texts: What component would go Here in the image below

texts: please can anyone tell me what component goes into the PCB? it is from a DSL filter


texts:
I want to connect a NOCTUA NF-A4X10 5V PWM 4-pin fan to a Raspberry Pi 3B.
The below is the circuit I'm planning to use.

(EDIT: Flyback diode (such as a 1N4001) is not needed since Noctua already provides polarity protection, and a brushless fan typically already has it);
(EDIT: No need for voltage divider) From Noctua documentation, the RPM output is an open collector output (see page 3 of Noctua Doc.). This means that if the Vcc is 3V3, and R=1k5 Ohm, we should be fine (current is then limited to ca. 2.2mA);
Resistence R2 (2K2) and transistor Q1 (2N2222A) are used to drive the PWM signal.

In other words:

Questions:

Is this circuit correct? Am I making any mistakes? I'm an engineer, but not an electrical one, so be kind... :)
Noctua does not seem to recommend an open collector design (see below)... What alternatives do I have?

From Noctua:


texts: Art Of Electronics - Center Tapped Transformer Efficiency and Current Question, LTSpice Question too

texts:
In the above image, I'm trying to understand the statement that says this is center tapped transformer is less efficient and the current is twice what it would be for a true full-wave circuit.  I also have an LPSpice and inductor quesiton later?  I did not print the full wave bridge circuit that was on the prior page.  In that circuit, it looked like the transformer was 1 to 1 (not step up or down).  In figure 1.75, the center tapped transformer looks like it steps the voltage up 2X, except that each half the voltage is 1/2.  If this is so, the voltage would be the same as the non stepped up transformer in the full wave bridge circuit that the book might have refered to (and I tried to model below).  I was trying to use ltspice to see current and voltage to get a sense of why it is less efficient, but didn't see that?

In this LTspice sim, i did not show the transformer that looks to be 1 - 1 . I spent time testing voltages. When I test the voltage on either side of V1, it does not ever go negative, is this because of the diodes?  If so, what happens, when V1 tries to go negative and instead goes positive?

In this image, VI, tested between R2 and the + sign, oscillates between +160 and -160.  When I test between R2 and L1, the negative drops out.  I only get values between 0 and +160 through time.  Where did the negative part of the wave go?  I suspect that its because of the diodes on the right side of the circuit, but don't understand how this "decoupled " side affects the negative waveform on the left side of the image?  The above is the center tapped transformer.  If the negative part of the input drops off, then I can see how this transformer could be working harder.  Any ideas on what happened to the negative partof the wave?


texts:
I am building several types of radio antennas, and I would like to test which is the most effective.  I am wondering: What is the best way to measure the strength of the received signal?

It is at ~151 MHz and 2 watt transmission power, and I will be testing over a distance of at least a couple of hundred feet. The results don't have to be calibrated, only correct relative to one another. Any ideas?

Edit as per comment request:

I am transmitting from a handheld unit which is capable of 2, 4, and 8 watt transmission power, but I am using the 2 watt setting to comply with MURS regulations.

The ideal measurement device would be low cost or home made, such as the one described in the answer below.

Thanks in advance.


texts: Embedded Programmers: How deep down the EE rabbit hole?

texts:
So I know most Embedded developers are probably EE/CE with some CS sprinkled in. I've done....enough with Arduino to where I want to get closer to the hardware. I graduated with a C.S. degree, but have the desire to learn a lot more about interacting with memory/registers/etc...(im not sure if it'll ever get me a job....but it's more for personal knowledge)

However, im curious how far down most "embedded programmers" go. I mean electronics themselves is a deep field. I do want to know enough about interacting with memory/registers/etc.. (even in ASM). But.....would there be a need to go further?

Secondly, is this even a doable thing with a C.S. degree? I know most embedded jobs require an EE degree, but do any do C.S.?

If so whats the best way to move from something like arduino? Im not really looking to do stuff with say.....beagleboards or anything Unix related. Im really talking about REALLY low level (ARM/AVR devices and such). Enough to where i can interact with the memory/register components. (I feel like thats the closest level without having to know how to build the chip itself haha)


texts: Verilog module instantiation during synthesis?

texts:
I have written a testbench in Verilog which creates 3 copies of a module and passes data back and forth with my main module test as anticipated:

test Sen1(A,B,C,D,E,F,CLK);
test Sen2(A,B,C,D,E,F,CLK);
test Sen3(A,B,C,D,E,F,CLK);

Is module instantiation only valid for simulating behavioral/functional models? I'm wondering what I need to do to create a synthesizeable version of this. On the one hand it seems that my module called test could aggregate all of the ports like this:

test (A1,A2,A3,B1,B2,B3,....CLK)

but then I'll have single modules with a lot of ports which would clutter my code (CLK would need to be shared between instantiations BTW). I'd like to know your thoughts on the correct approach for reorganizing/reformulating my module instantiations into a code structure that I can synthesize and assign pins to.


texts: How to get higher frequency from DC power supply?

texts: I desoldered a component, HY-05 Electro-magnetic sound generator, from a broken motherboard. Its DCV is  3~8V, operating frequency 2400 plus or minus 200 Hz. I can get a small metallic sound with the operating voltage probably because the frequency is wrong. How can I adjust the frequency in the power supply of 50Hz? If the question is bizarre, it may be that the component is just broken.


texts: Confusion with Nyquist theorem when sampling cosines versus sines

texts:
I'm having different results when sampling a cosine wave versus sine wave at different scenarios. I used MATLAB to plot waveforms.

I will try to give some examples to make clear where I'm stuck at.

Figure 1 below shows a 10Hz cosine wave(top) and a 90Hz cosine wave(bottom blue) both sampled at 100Hz sampling rate. Black dots show the sampled resulting waveform. As we can see the 90Hz cosine is aliased as 10Hz:

Figure 1:

Now we change the waveform to sine, and Figure 2 below shows a 10Hz sine wave(top) and a 90Hz sine wave(bottom blue) both sampled at 100Hz sampling rate. Again the black dots show the sampled resulting waveform. As we can see the 90Hz sine is aliased as 10Hz. But this time there is 180° shift:

Figure 2:

In similar fashion, Figure 3 below shows a 10Hz cosine wave(top) and this time a 50Hz cosine wave(bottom blue) both sampled at 100Hz sampling rate. As we can see since we are sampling with twice the waveform frequency(2×50Hz), the bottom cosine wave is reconstructed without any aliasing:

Figure 3:

But now we do the same thing for a sine wave. Now Figure 4 below shows a 10Hz sine wave(top) and 50Hz sine wave(bottom blue) both sampled at 100Hz sampling rate. And again we are sampling with twice the waveform frequency(2×50Hz). But the 50Hz waveform is not reconstructed as in cosine case, the sampled waveform has disappeared:

Figure 4:

Regarding the above observations, I'm confused at three points:

1-) Regarding Figure 1 and Figure 2, what is the real signal here? Cosine or sine? Aliased cosine does not have 180° shift but the aliased sine has. What is the significance/meaning of this difference?

2-) Regarding Figure 3 and Figure 4, I thought Nyquist theorem applies any cosine or sine. But in Figure 4 what is going on? The sine disappears even though it is sampled at Nyquist rate.

3-) I cannot make sense of these observations. It is because when we apply sinusoidal waveform to a scope from a function generator, the scope or ADC does not know whether the input signal is cosine or sine. Yet sine behaves differently than cosine when sampled as in my question. What can be the cause for the confusion here?


texts:
I want to use my Raspberry Pi to turn on and off a 12V current for a certain amount of time. I've read a lot on Raspberry Stackexchange and I've understood that the 5V GPIO Pin is... Not GPIO, meaning that I cannot turn it on and off.

I am not an electronics expert, but I've already learned how to use GPIO to control stuff like Led, or simply closing circuits, using this tutorial (french) : http://blog.idleman.fr/raspberry-pi-06-utiliser-le-gpio-et-interagir-avec-le-monde-reel/

But now I need to turn on / off a 12V current for about 8 seconds.

I have a Rasberry Pi 3 Model B V 1.2.

I also have this relay : https://www.velleman.eu/downloads/29/vma406_a4v02.pdf

My question is : Could I use GPIO ports to open / close the relay safely ? I imagine plugging the relay into the 5V pin of the Raspberry and using another 3.3V GPIO pin to "activate" some sort of switch...

I really have no electronics background so don't hesitate to start from scratch.


texts: How are cell failures handled in large lithium battery packs?

texts:
In a large battery pack of lithium-based cells for an electric vehicle or grid storage system, how are failed cells handled?  Answers to another question indicate these cells are usually hardwired in parallel blocks (which are then connected in series and balanced) so that resistance isn't added in the path of high current.

What happens when a cell fails and acts as a short circuit?

It seems this would short out a block of parallel cells and decrease the capacity of the overall pack significantly.  If the dead cell could be removed from the pack by an electronic or safety system (power transistor, fuse, physical removal &/or replacement) the rest of the parallel cells could continue functioning with a much smaller decrease in usable pack capacity.

Lead-acid batteries seem to be replaced on a timed maintenance schedule, or when certain usage metrics are exceeded, say in data center usage.  With lithium batteries being so much more expensive, are there any typical electronic design features which handle failed cells automatically rather than by rotating out the entire pack before end of life?

Are chemistries such as LiFePO4, with 2000+ cycles to 80% capacity, reliable enough that cells failed to short circuit are rare enough to ignore as an electronic design issue?


texts:
I am trying to compile and synthesis a design wrote with sv2012 , I was able to use vivado2014.1 to compile fine but i got a problem in synthesis since as per Xilinx Vivado doesn't support hierarchical  instances:
http://forums.xilinx.com/t5/Synthesis/Synth-8-146-cannot-resolve-hierarchical-name/td-p/370713

I tried tools like precision and ISE but they don't support sv2012.

What are the Synthesis Tools supporting SystemVerilog 2012?


texts: Question about discrete-to-digital IC's output current

texts:
I am designing in a discrete-to-digital converter in my project (link)

and I am confused about the device's output current capabilities. I would like to know the maximum value so I can make sure I don't overdrive the LEDs that will be connected to the outputs.

Here is a capture of the screen shot that talks about the output sourcing.

My question is why does it have Ioh labeled as a minimum value and nothing for max? I was expecting it to provide a max value. Do they call it a minimum value because of the conventional current negative sign, or is there something else I am missing?


texts: why does the Stm32f103c8t6 Board need an ST-Link V2?

texts:
Well I am starting a course on embedded systems on udemy and it seems I need an M3 or M4 ARM cortex MCU so I can follow on the projects. The course itself recommend the Discovery board, but I was aiming for the stm32f103c8t6 Datasheet
It seems that there's no much information about the board in terms of programming on the stm32 IDE as everyone is using it with the Arduino IDE .
I was wondering If I will need additional hardware beside it like an st link v2 ( which I don't know it's purpose yet ,but that's what I got after some searching ). in order to be able to program and debug nicely along the course
The first part of the course is in the following link in case someone needed more details The Course


texts:
i have a print where i need like 8 PNP transistors. They are all connected the same: The Emitter is connected to VCC, the Base is connected to a GPIO and a Pullup and the Collector is connected to some LED.
The chip i want has an Input for each Transistor which connects to the Base, an Output for each Transistor, which connects to the Collecter and one pin which shares all the Emitters. Ideally it also has a Pullup on every Base.

I think the ULN series is something similar with NPN or a Darlington pair, but not sure.

I'v drawn a small sketch, on how the Chip could look like:


texts:
Until now I used Microchip PIC, to program this microprocessor there is MPLAB. I would like to make a step forward and learn about other microcontrollers.

I found the BeagleBone Black quiet promising for my DIY project because there is a 2GB flash and 1GHz clock.
I have a few question as a beginner:
On the eewiki I found a tutorial where they are describing how to start, but this tutorial is based on SD card.
If I want to use only the 2GB flash card than how can I load my software on it without using SD card?

I saw on that page that there is a bootloader(UBoot), what is this for? For example I just wan to blink a led, using PIC it is a few line of code which I upload and that's all, If I would like to do the same with a BeagleBone Black what I suppose to do?
Do I need UBoot? How can I write this piece of code to the eMMC of the BeagleBone?

If I have a board without any preloaded software(including bootloader) how can I start to upload a software?


texts: why when I touch the input cable or put my hand near it the LED comes on?

texts:
I am a beginner at electronics and recently got an arduino and the Arduino Project Handbook and I am having trouble with the push button led project.

I have followed the directions and have the correct resistors but every time I go to press the button the led stay on and if I touch the cable or put my hand near the cable the led comes on.

am I missing something?

Below is the Circuit and Code I am using....

const int buttonPin = 2;
const int ledPin = 13;
int buttonState = 0;

void setup(){
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
}

void loop(){

  buttonState = digitalRead(buttonPin);

  if(buttonState == HIGH){
     digitalWrite(ledPin, HIGH);
  }
  else{
    digitalWrite(ledPin, LOW);
  }

}


texts: Series resistor on VFB of LTC3652 solar charger

texts:
I use a LTC3652 solar charger from a given schematic for a solar powered microcontroller board and I want to understand the circuit a little bit more.
So why do they connect a resistor (R6) in series with the VFB pin of the regulator? I read the description of the VFB input and they write that the output voltage is only regulated with the voltage divider. So what is the function of R6?


texts: Proper soft starter for vacuum cleaner universal motor

texts:
According to this question:
Max startup current for vacuum cleaner motor
We have the problem of tripping the dental clinic circuit breakers during the starting the universal motor.
I am trying to test one proper soft starter for the vacuum cleaner universal motor 2200W 220v, so by googling find this video:

I tried to update it for 2200W 220v Universal motor, by this calculation:

According to the above universal motor use almost 2200w/220v=10A RMS and based of its ratio to the universal drill motor current which is around 6A RMS could be updated for my usage by adding one 12R 5W high power resistor  (3x12R 5w).

Is this soft starter good for my problem, and if not what is the proper soft starter to solve this problem?


texts:
Im using the SN65HVD233-HT CAN transceiver where it states that loopback is possible without data going out to the bus.

Im using LPC1778 uC and want to know,if i enable the loopback pin in the transceiver, will the data transmission from the uC be affected, because CAN works on sampling the Tx data and Rx data simultaneously(internal to the uC to identify bit errors).By shorting the Tx and Rx pins of the uC via the transceiver,will it cause any errors?

Or must i put the uC to self-test mode(no ACK required for a transmitted message to be declared successful) before i perform a loopback test,so that the Tx message wont be repeatedly sent when i perform a loopback?

loopback test will be used to check CAN module pin and transceiver integrity(i.e if TX data== RX data).


texts: 5050 led strip 60 led/m flickers when fading in and out of colors

texts:
I have to start out by saying I know just about nothing with electronics and it's very hard for my mind to get a grip on but I'll try my best.

I bought a 5m long 5050 led strip with 60 leds per meter. They are RGB leds. These are the leds:

This is the picture of what it came in:

The transformer link is here.

The infrared receiver looks like this:

The way it's set up is led strip to receiver to transformer to wall. Things are plugged into the transformer as shown. The white wire is for the receiver and the black goes to the wall:

But when I put it in fade mode (slowly fades between colors) it flickers transitioning from yellow to red to purple. Blue and green are fine and smooth. And the other mode (red fade in then out, then green fade in then out, then blue in and out) the red is ok but the green and blue flicker a lot. Is this set up wrong and what can I do to fix it? There is no flicker on one single color but I got it for the fading in between colors. These parts all came separate but from the same store. The employees helped choose it all out but I can't ask them questions because I'm an American in Russia with horrible Russian.


texts: What is the longest lasting (number of years or cycles) commercially available battery technology?

texts:
I'm asking this question because I felt that an answer would be useful to myself, and anyone else who might design a portable or other battery powered system that is meant to last several decades without requiring a new battery.
What is the longest lasting battery technology.  By longest lasting I mean the battery that supplies the required energy for the longest number of years.  Answers should either be based on practical experience, manufacturer data sheets, other manufacturer supplied literature including reliability estimates or other white papers or advertising claims.
To keep this from to broad...

The battery must have a capacity of at least 80 watt-hours.
The load will draw 10 W max from the battery.
The battery may take up to 8 hours to charge.
The battery must weigh 10 pounds or less.
The operating temperature range is 5°C to 40°C.
Once per day, the battery will be charged to 100% of its current capacity, and then discharged at up to 10 W for 8 hours.
The battery voltage is not important.  Assume we can place a converter at the battery output to make whatever voltage we need, and that the converter efficiency is factored into the 10 W load draw.

The best battery is the one that meets the above operating conditions for the most number of years.
If the battery is lighter or cheaper that's a bonus.  Naming a specific battery chemistry is better (rather than just saying Lithium, Alkaline, or Lead Acid, etc).


texts:
What are SPWM, CPWM, and DPWM?

I googled, and they are single PWM, combined PWM, and PWM is pulse-width-modulation, which I already know.

DPWM I am not sure. I don't know it is dual PWM or dual-phase PWM.

But, these is all I know. So far I cannot know what they really are. Web search result is vague. May these terms are too easy or rarely used, so I find it difficult to get a clear explanation on website. Please help me, thank you!


texts: How to convert noise to noise density in mic pre amps

texts:
I am trying to compare two low noise mic pres for the lowest noise, and I am looking at the

TI1012 and MAX9814

MAX9814: ♦ Low Input-Referred Noise Density of 30nV/√Hz
TI1012: Output Voltage Noise (A-Weighted): −89 dBV

http://www.ti.com/lit/ds/symlink/lmv1012.pdf
http://datasheets.maximintegrated.com/en/ds/MAX9814.pdf

I thought I could get some insight from simply converting the 30nV into dBV, but ~-150dBV doesn't make sense. I would expect it to be very similar to the -89dBV. I believe my lack of understanding is in the density portion (√Hz) and how it is calculated.


texts: LCD 16x2 (I2C) with FPGA (Altera Cyclone II)

texts:
this is the question, a few days ago I bought the FPGA Cyclone II development board from altera (I am a big fan of arduino and I have a variety of modules and others) at first I started studying Verilog, I provided some led onboards to learn how The clock works and others, but now I want to try something a little more difficult, an LCD. I saw several forums / pages but they use the LCD without the I2C interface and I want to use it with I2C for two reasons, first because that way I will also learn how to use the I2C protocol for other sensors, and second, I don't want to desolder the module.
If anyone can give me some piece of code or website / forum where I can learn how to use this and show a little text, I would appreciate it. Greetings!


texts: Does ISP mean that the chip has to remain stuck on the system PCB when programmed?

texts:
According to wiki "In-System Programming (ISP) is the ability of some programmable logic devices, microcontrollers, and other embedded devices to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to installing it into the system."

This means that if the device can be programmed after it has left the factory than it supports ISP. We can use JTAG with FPGAs to program them once they are in the field thus this is an example of ISP. Now consider that we have flash devices that need to be pulled out of the system PCB in the field, put into another programmer and once programmed we just put the flash device back onto the PCB. If all this is done outside the factory once the device is in the field, is this also called ISP?

I am asking this question because the term is making me confused here. The device is being programmed after it has left production, but it is being removed from the system when programming is to be done only.


texts: deriving the transfer function given bode plot

texts:
I have been given the following question on finding the
transfer function from the following bode plot

I know that the transfer function should look like this
\begin{equation}
H\left(jw\right)\:=\:\frac{k}{\left(jw+10\right)\left(jw+100\right)\left(jw+1000\right)}
\end{equation}
but I don't know if am doing this right, also how to find the value for k.
Thank you for your help.


texts: Transistor power dissipation, current, and voltage

texts:
Correct me if I am wrong, but from my understanding a transistor is current controlled in that the current flowing from Collector to Emitter is varied by the amount of current going from Base to Emitter. I initial though that a transistor was controlling the current flow based upon B->E and not changing voltage.

I recently was looking into transistors further and read the following:

  The
  power dissipated in the transistor is the voltage
   drop across the collector emitter junction times the
  collector current

http://www.physics.unlv.edu/~bill/PHYS483/transbas.pdf

I thought that there wouldn't be a voltage drop when using a transistor since B->E is controlling current flow, not voltage.


texts:
I have purchased this lithium polymer battery (11.1V, 5500mAh), to power a robotics project. The project uses a Raspberry Pi, three continuous-rotation servo motors, a couple of LEDs and a Sparkfun Geiger Counter.

I've also set up a voltage regulation circuit, as shown with the battery below.

The battery is behaving very strangely. Firstly, very loud cracking noises were made when I accidentally short circuited it. Is this normal? Secondly, when testing it with a multimeter, both the (fairly thick) wires got very hot. The ammeter setting (when I turned the dial to the one with the 200 on it) showed a ridiculously high reading - something in the range of 26A. When I plugged the battery into the voltage regulation circuit and turned it on, the LED (5V), came on dimly briefly and then faded out quickly. I thought that the regulator had failed and the LED was burnt out, but when I checked by connecting a power pack, it was fine.

What's gone wrong? Do I need to get a smaller battery? Is my circuit for voltage regulation wrong? Do I have a faulty regulator?

Thanks for your help,
Archie

simulate this circuit – Schematic created using CircuitLab


texts: ESP8266 12F doesn't work when programmed with arduino, but works fine with AT commands

texts:
So, I got this webserver running using:
http://arduino.esp8266.com/stable/package_esp8266com_index.json
V2.4.1

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>

#include "index.h" //html page

const char* ssid      "xxx"       // WiFi SSID
const char* password  "xxx"  // WiFi password

//Creat object
ESP8266WebServer server ( 301 );

void handleRoot()
{
  String getPage = MAIN_page; // read html contents
  if ( server.hasArg("dir") )
  {
    handleDir();
  }
  else if ( server.hasArg("spd") )
  {
    handleSpeed();
  }
  else
  {
    server.send ( 200, "text/html", getPage );
  }
}

void handleDir()
{
  String DirValue = server.arg("dir");
  Serial.println(DirValue);
}

void handleSpeed()
{
  String SpeedValue = server.arg("spd");
  Serial.println(SpeedValue);
}

void setup()
{
  //SerialCom
  Serial.begin(115200, SERIAL_8N1);

  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while ( WiFi.status() != WL_CONNECTED )
  {
    delay(500); Serial.print(".");
  }
  //Connection stable ok
  Serial.println("");
  Serial.print("Connected to: " ); Serial.println( ssid );
  Serial.print("IP address: "); Serial.println(WiFi.localIP());

  //????
  server.on ( "/", handleRoot );

  server.begin();
  Serial.println("HTTP server started" );
}

void loop()
{
  server.handleClient();
  delay(500);
}

After I updated the html page and flashed the esp8266 again (with Arduino IDE), for some reason, the esp8266 never connects to the wifi, therefore, never leaves

  while ( WiFi.status() != WL_CONNECTED )
  {
    delay(500); Serial.print(".");
  }

Another thing that's intriguing, is that I only get garbage in the Serial Monitor at 115200 baud rate, and at 74880 I get some information about the board, "Serial.print("Connecting to "); Serial.println(ssid);" is garbage too, but the dots are well received.

So I thought my board was damaged for something I did wrong. Then I tried to flash the firmware (ESP8266_NONOS_SDK-2.2.0) again to test it with AT Commands. And all worked really fine, I could change the baudrate to any I wanted and still works fine, connected and disconnected to my wifi without problems.

I tried again with Arduino IDE, but the same error keeps appearing.

The last thing I remembered to do was use the "WiFi101 firmware updater" that comes with the boards manager of esp8266, but couldn't even get past the first point "test connection".

Any ideas? (sorry any error in my writting)


texts: Is this the right way to mount a 2N3055 or any TO-3 form on a heat-sink?

texts:
Top view:

Bottom view:

This is the first time I'll be using a heat-sink on a transistor. Right now these are just placed together.

Is the mounting correct?


texts:
I am quite new to electronic and I'd like to build a setup plugged with a 12V PS (because there is a water pump in my setup).

But at the same time, I'd like to feed the Arduino VIN with the same power supply. Is it a good practice to use a regulator to go from 12V to 5V for a H24 setup? I mean, will it burn because of too much power dissipation?

If no, how can I supply the Arduino VIN in a more elegant way?


texts: Is this resistor for the base of the transistor calculated correctly?

texts:
I have a NPN transistor MMBT2222ALT1G which I want to use to control a red LED (Uf=2V, If=22mA).
VCC = 5V and my microcontroller is operating on 3.3V.

I calculated the R24 resistor for the LED - it should be about 136.36 ohm, so I picked 150 ohm.

I'm not sure if I calculated R23 correctly...
Are these values for my transistor correct?

Vbe = 1.2
Vce = 0.3
hFE = 210


texts: Analog logic circuit with adjustable threshold

texts:
I have a logic circuit currently consisting a few few AND gates and it's working fine (simulating) with if i use logic levels as the inputs. However my input levels might change in amplitude and I'd like to be able to control the logic threshold with something else (like and DAC or something). What would be the simplest way to do this?

if it helps, my inputs are very short pulses, that should have the same amplitude, although the amplitude may very from time to time.


texts: Why is wire's inductance inversely proportional to its thickness?

texts:
In all the formulas I could find, wire thickness is always in denominator, it seems. Of course thinner wire can have more loops in same space, but even in this monster of a formula for single wire:

Inductance seems to be reversely proportional to thickness somehow.

I just can't provide any logical/physical explanation for this.


texts: What difference of marked relays on scheme?

texts:
I have two relays that marked as red and orange.
What is the difference between them?

And what relays (SMD) I should use to create pcb?

Thanks for answer.


texts: How to change from audio-out to MIDI out from same headphone jack?

texts:
I am trying to add MIDI OUT capabilities to an audio device - using the same jack.  User will select in software if audio or midi is to be outputted.
Currently, the audio jack wiring is as shown (R1 is 1k).
I've thought about switching pin 1 of jack to GND and using pin 4 as active HIGH (to avoid possible sleeve-ring short) - but am unsure if this is best practice as midi specs are active LOW.   R2 would need to be low enough to allow 5mA current loop (i.e I can't reuse R1).
Priorities for design:

Use as few GPIOs as possible
Low cost/part list


texts:
We are using a Isolated Fixed-Ratio DC-DC Converter from Vicor (http://www.vicorpower.com/documents/datasheets/ds_BCM4414xG0F4440yzz.pdf)
that is powered through a 600VDC accumulator.

The DCDC powers the entire low voltage system of a electric vehicle. It's somewhere between 10-16 Amps depending on the state of charge and which systems are active. The DCDC has problems starting up and I believe it is because we are on the limit of the output capacitance for the DCDC and unplugging some systems at start-up seems to fix the problem. Usually we have to start it without cooling fans being connected, and then connect them once it has finished starting up.

I am waiting for parts to connect to the DCDC through the PMBus to monitor the current and other parameters at start-up.

I was wondering if there exist a nice solution for slewing the output current of the DCDC?

By the way, this is a student project if it seems like a strange issue.


texts:
What is the expression of V if V(0) = 4V?

simulate this circuit – Schematic created using CircuitLab

I am unable to proceed further after forming the following equation:
-v/R1=(v-V)/R2+C1dv/dt


texts: Connecting both ends of battery with a resistor is fine?

texts:
I recently just started learning about electronics and electricity. After a lot of reading this is my current understanding about a battery. If you buy a battery it is labeled + or - on each end. The + side is just a bunch of atoms with extra electrons(electrons are - but I guess they labeled this side + ?). The - side is a bunch of atoms with missing electrons(protons are + but I guess they labeled this side - ?). So + side of the battery flows to the - side side. Is this correct?
Resistors limits the current/amps but keeps the voltage the same. Correct?
You don't want to connect them together with a wire since there would be too much current flowing through, such that the battery heats up till it explodes or something. So connecting a high ohm resistor between a battery would be fine. Correct?
Can someone also explain to me WHY a voltage divider works? All websites just explain the formula and the circuit.
The main reason I asked these questions was since I was learning about arduino pullup pins. I noticed a voltage divider in the circuit. The digital input pin measures the voltage right? If the voltage is almost 0/ground it returns LOW else HIGH.


texts:
I'm new to VHDL and I cannot seem to get my code to compile. I've looked over the code to the best of my ability, but I do not see anything wrong with it from my current basic understanding of how it works and I am wondering if anybody could help. The code is supposed to model a NLX1G99 configurable multi-function gate (minus the enable bit)

library ieee;
use ieee.std_logic_1164.all;

entity multifun_gate is
port(
        d,c,b,a: in std_logic;
        y: out std_logic
    );
end multifun_gate;

architecture dataflow of multifun_gate is
begin
    y <= (a and not b and not c and not d) or
         (a and b and not c and not d) or
         (not a and b and c and not d) or
         (a and b and c and not d) or
         (not a and not b and not c and d) or
         (not a and b and not c and d) or
         (not a and not b and c and d) or
         (and and not b and c and d);
end dataflow;


texts: GPS L5C Differential? Max Update Rate(bits/s|Hz)?

texts:
The differential GPS chips use L1 and L2C to calculate the ionospheric interference.

With the new GPS satellites, the new band L5C is being deployed, and I am wondering about the following things:

Will L1 and L5C be used as new type of differential ionospheric error correction? Could L1 use both L2C and L5C as a kind of double correction at the same time? (Would it even be necessary or make sense, or are they still testing this and I’m getting ahead of myself)
Separately, could L1/L5 produce superior differentiation to L1/L2?
I’ve been reading documentation and cannot seem to grasp what the new nav data rate for L5C signal is (per each SV). Is it still the same 50Hz of L1 and L2, or is it 25Hz, or is it 100Hz? Whats throwing me off is the following line: “The 50 bit/s data is coded in a rate 1/2 convolution coder”
What update rate do the SBAS SV’s transmit? Is it also 50Hz?


texts:
Is it possible to measure waveform of current with current probe connected to analog oscilloscope? Or is that possible only with digital oscilloscope?

Are there any other instruments out there that can display waveform of measured current?


texts:
Datasheet - SN65HVD232
Full part no - SN65HVD232D
My schematic -

Hi all, there is a problem in my PCB where 5V track is connected to VCC pin instead of 3.3V. Actual input should be 3.3V as per datasheet.
So will it work?
One more thing - pins 5 & 8 are NO CONNECT pins but I have 3.3V and a GPIO pin connected to them respectively (to be compatible with another transceiver IC).
Will that pose any problem?
Please help me with this. It is urgent.


texts: Two same ADCs produce different result for same signal

texts:
I have two ADCs (the model AD9248BST/BCP-65, with the default configurations, not "cross-calibrated"), that are feed the same constant point-to-point voltage. The returned values, however, differ by an order of 7 bits.

The datasheet (see page 3) specifies that the effective number of bits is 11.8, so I should expect noise in the difference to be of the order of 2.2 + 1 = 3.2 bits.

What could explain that the difference between the two ADCs is greater than expected?


texts: Polarity of unmarked smt electrolytic capacitor

texts:
I have a kit with three capacitors, described in the parts list as "10uF 25V SMD 1206" and shown on the circuit diagram as polarised (an open rectangle and a filled one). Seen through the transparent side of the package they are pale brown or orange, and appear to be unmarked, although there is an offset hole in this side of the package. (Possibly a circle on the component itself -- I am reluctant to remove them from the packaging until I am ready to solder them in place.)

So, my question is: how do I determine the polarity of these items, or does it not matter, i.e. they are self-polarising in circuit? By the way I have no trouble hand soldering this size of SMD.


texts: How do I remove electrical interference when using same source power?

texts:
I have a microphone receiver and a raspberry pi. I'm trying to power them using one DC jack. The receiver uses 12v and the PI uses 5v. The PI is outputting music which goes into an IN port on the receiver and the receiver is supplying the microphone audio. The receiver then has an out AUX port which will send both the microphone and music to my amp/speakers.
I'm using a step down converter to convert the 12v to 5v and then power the PI. Then a ground loop isolator to remove the noise however I am still getting a large buzzing sound. When I power the PI and receiver on their own power source all of the noise goes away.
What can I do to not have to use 2 separate power sources and have clean audio?
Here is a very poorly drawn wiring diagram of my setup.


texts: Different results from Smith Chart and Transmission line impedance equation

texts:
I have the following question which I need to solve

Use a short-circuited section of air-filled TEM, \$50\Omega\$ transmission line
( \$\beta= k_0 , \lambda_g = \lambda_0\$ ) to create an impedance of \$Z_{\text{in}} = -j25\Omega\$ at \$f = 10\,\text{GHz}\$.

By using the transmission line impedance equation for a short circuited line, I arrive at the following
$$-j25=j50\tan(\beta l)$$
$$\tan(\beta l)=-0.5$$
$$\beta l=0.4636\,\text{rad}$$
$$l=\frac{0.4636\lambda}{2\pi}=\frac{0.4636(0.03)}{2\pi}=2.213\,\text{mm}$$

However by using the Smith Chart the value of \$l\$ is \$0.426\lambda=12.78\,\text{mm}\$.

What could I be doing wrong?


texts: Does a motor driver need a ground reference for logic signal with optocoupler isolation on logic pins?

texts:
I am using two power supplies, one for the motor driver (+24v), and the other one for my MCU (+5v).
My concern is that in the datasheet of the motor driver (DRV8871) it is mentioned that GND needs to be connected to the logic supply GND and PGND need to be connected to the high power GND, but I have connected PGND and GND of the motor driver to the same GND (GND 1).
So technically it should not work, but what if I use an optocoupler as isolation with two different GND (GND, PGND) on the logic pins of the driver; will it work?
All images related to my circuit


texts: Can someone explain how this Ratio detector circuit works?

texts:
I understand how a Foster Seeley discriminator works, but in this Ratio detector, which is a modified version of the former, I don't understand the purpose of having three transformer windings, or having a diode in reverse (why would you want a diode reversed if it can't pass any signal?) or how the signal flows through it.

I also don't understand the purpose of C5, but I understand there's a dynamic filtering function going on (how?)

And lastly, since I don't understand the purpose of three windings, I don't understand the purpose of R3, C6, R5, C7 and C8.

Can someone explain the whole circuit?


texts:
I have found many projects(digital timers) which use D and T flip flops.
In the left bottom pin we put the clock source, can this pin be always high or always low?
And if that's possible writing data to flip flop or toggling values is always when that pin is high correct?


texts: Problem Measuring Current in a High Voltage circuit with arduino

texts:
I 'm measuring a current in a resistor as shown in the picture below. There I'm using a voltage substractor with an LM324 Operational Amplifier. I'm having trouble in the real World when the voltage is grater than 12 V , the amplifier behaves strangely (I'm feeding the amplifier with 12 V ).

What can I do in order to properly measure this current with  such a high voltage in the nodes of the resistor. I need to get to 60 V. I'm planning to send this voltage signal to Arduino, so I need it to be beteween 0-5V .

Any Help is appreciated.


texts: Could an audio induction loop be used to transmit wi-fi?

texts:
A few months ago, I built an audio induction loop around my house using the existing dog electric fence, and had great results, and could hear the music a small amount even 2 neighbors away. I used a coil to pickup the audio and a power audio amp to transmit. I am wondering if it would be possible to transmit wi-fi for a device to pick up. This seems like a good idea because the wifi would be easily picked up around the house, and would reduce by exponential factors outside of the house, preventing people from picking up the signal. To reduce the power transformer noise, I am guessing a high-pass filter could be installed on the receiving device. Would it be possible to do this? I am not saying easy, just possible, and would it be practical? It seems like a lot of bandwidth could be transferred through the induction loop because all frequencies could be available (except under 100 hertz because of the power transformer interference). The only disadvantages I see is the setup of the large wire, which would have to be placed around your house and the orientation of the pickup coil ( maybe an external coil would be plugged into your laptop or a self-rotating coil inside)

Would this be possible? Has this been considered? And if so, why is it not done today?


texts:
I have 4 relay module originally created for Arduino (it looks very close to the image below) and I am little confused with the way how it works.

There are 6 pins ins this relay:

GND
IN1
IN2
IN3
IN4
VCC

So when i connect 5V to VCC and ground to GND - I get about 3V between each of the IN1..IN4 and GND. Why does it happen?


texts: How does the PIC's PMCON1.WRERR bit actually work?

texts:
I know from the datasheet that it gets set automatically on a rising edge of the WR bit and cleared automatically on a successful completion.  Thus, if it's still on, then something went wrong.  So far so good, but how closely should I watch it?

The chip that I'm using for this project (PIC16F1454) erases and writes its program memory in "rows" of 32 words each.  A write to this memory actually goes to one of 32 transparent latches that corresponds to the lower bits of the address.  Then, if the LWLO bit is off, the same operation then transfers all 32 latches simultaneously to the row specified by the upper bits.  So the procedure, given a memory image, is to erase a row if it isn't already, set LWLO, fill the row except for the last word, clear LWLO, and write the last word.

During this process, I'm setting WR for each word as part of writing the latch, so WRERR should be on also.  Then if the write is successful, WRERR turns back off again.  The datasheet doesn't say if the latch has the success rate of ordinary RAM or what to do if it goes wrong.  It does say that the latches are all reset to the erased value (0x3FFF) after being transferred.  Is it a problem to blindly fill the row and transfer it, then check WRERR and repeat the row if necessary?  If WRERR is good, then I'll verify the data itself and repeat if necessary.

In other words, is it possible to fail when writing a latch only?


texts: EMVA standard 1288 SNR formula (equation 11)

texts:
I'm trying to understand equation 11 for Signal-to-Noise Ratio in EMVA standard 1288 Release Candidate 3.1:
http://www.emva.org/cms/upload/Standards/Stadard_1288/EMVA1288-3.1rc.pdf page 7.

Using equations 6 and 8 I arrive at something similar to eq 11. However for me there is no

Instead I get

I have to say it makes more sense to me to find another noise term below instead of number of electrons.

Can anyone explain this?


texts:
I am curious, how important is a general understanding of electromagnetics to microwave circuit design?

I have looked at Pozars book which provides some background on EM and transmission lines in the first chapter and then goes on its way.

Would someone with little background in EM but a sufficient background in mathematics be foolish/stupid to start his book instead of doing an entire EM course beforehand? To what extent is a fullbackground in EM needed to understand a book like Pozars?


texts: Car stereo wired to computer power supply with backup battery to keep memory

texts:
This past Christmas I re-purposed an old Car Stereo and built a portable outdoor radio for my Dad. Ultimately what I wanted to do is have it to where it runs primarily off of a computer power supply (EVGA 500 W1 80+, 500W Continuous Power) when plugged into an outlet but when unplugged it can retain all of the presets and audio settings from a connected 12v battery source. I thought I knew how to achieve this but I was definitely wrong and now the radio draws all of its power from the battery instead of the Computer Power Supply. Hopefully I can describe my current setup and one of you can provide some guidance on how I can achieve this.

My current setup:
My car stereo has two 12v leads on the harness. One is the constant/battery (yellow) which also keeps the memory for the radio. The other is red which is labeled as Ignition. I took all of the 12v Yellow cables from the Computer Power Supply and connected them to the Red (Ignition) cable thinking that would power the stereo unit. Meanwhile I wired the Car Stereo's Yellow Constant/battery wire to a 12v/7aH battery in order to maintain all my settings when the Power Supply is not plugged into the wall. Based on everything I read online the Computer Power Supply should power the Radio all by itself as long as both the Red (Ignition) and Yellow (Battery/Constant) wires coming from the radio are connected to the 12v yellow wires from the power supply. But as soon as you turn off the power supply or unplug it all the radio settings and stations are gone. Hence why I tried to wire in the backup 12v battery to retain memory.

My Problem:
The Stereo unit draws all its power from the Yellow (Constant/battery) wire and only uses the Red (ignition) wire as a switch to let the radio know when the car is on so that it can turn on when the engine starts. Well needless to say the first time out with the radio it played flawlessly until my 12v/7aH battery got too low to power the Radio (4 hours of play).

Question:
How can I wire the stereo to where it pulls all its power from the Computer Power Supply when plugged into an outlet but then switches over to the secondary power source (12v/7ah battery) when its unplugged in order to keep all the settings and memory. I do not plan on running the radio when not plugged in if that helps. I just would like to find a way to where I can configure all the settings and then have it to where my technology deficient dad can just turn it on and have everything work.

I've ready about switches, and diodes and other possibilities but my understanding of how they work is just to limited for me to grasp it and conceptualize a solution. Thoughts?


texts: Installing a bootloader on an ARM Microcontroller

texts: I have purchased this LPC1788FBD144,551 MCU and  this LPC1313FBD48/01,15 MCU and I want to install a bootloader in assembly on them which can call a function in C. How can I install the bootloader on the ARM MCU? Would I install it directly on the MCU or on a separate component (if so can you show me which part on the newark website)?


texts: Simulating an IP core in Modelsim is delayed by one clock cycle

texts:
I compiled the IP core library in Modelsim. The library from Xilinx is installed on my computer and I also created a ROM using the Xilinx tools. However when I simulate the IP core I find that fetching data from the ROM will delay the simulation by one clock cycle. How can I deal with it?

I don't want to write a second set of code, one for the simulation and one for downloading into the Spartan-3E. I program in Verilog and the following is the test bench for the IP core:

`timescale 1ps / 1ps
module InstrMem_tb  ;
    reg    clka   ;
    reg  [31:0]  dina   ;
    reg  [7:0]  addra   ;
    wire  [31:0]  douta   ;
    reg  [0:0]  wea   ;
    InstrMem
      DUT  (
             .dina (dina ) ,
             .addra (addra ) ,
             .douta (douta ) ,
             .wea (wea ) ,
             .clka (clka ) );
    initial begin
        wea = 0;
        dina = 0;
        addra = 0;
        clka = 0;
    end

    always
        #50 clka = ~clka;

endmodule

I can only fetch the data at address in the IP core named InstrMem at the second posedge.


texts: Sample externally powered analog sensor with TelosB

texts:
This is a newbie question so forgive me for its simplicity

I have a FIGARO TGS 2602 Air Contaminant Sensor and would like to sample its analog output using TelosB which is powered by 3V-3.6V max voltage by batteries or USB.

The TGS sensor must be powered by a 5 volt min external power supply.
Is there a way to sample its output (its output will never exceed 4 volts) with the TelosB without destroying the Telosb? That is, can I use a common ground for both the sensor and Telosb?

For example, at page 23, you can see that pin 9 is the analog ground:
http://www4.ncsu.edu/~kkolla/CSC714/datasheet.pdf
I can not power TGS 2602 with Analog VCC (pin 1) so I have to drive it with external source (5 volts min)

So my question again is, can I use pin 9 (analog ground) for common ground for Telosb and TGS 2602?

Thank you in advance


texts:
I have a piece of instrument made around 2000 with a connector to computer that I cannot recognize. Can someone help me out? It is a 20-pin connector, with 10 pins on each row. Pictures are here: https://photos.app.goo.gl/ZF6i9fdpoevncE5j8
The connector in question is marked "Computer". I suspect it is some kind of scsi.

Apologize for not saying anything of the instrument. It is a Thermo-Nicolet Nexus 670 FT-IR Spectrophotometer, made in the USA. It was the work horse of the infrared spectroscopy community. It is not one of a find. I thought it is not too relevant, since "computers" that worth interface to in year 2000 are limited to IBM PC.


texts: Today I've soldered my clone of ZVEX Wooly Mammoth and when I started testing, it didn't give a sound. Hours of visual and multimeter inspections gave me no clue about a mistake. So, I appreciate any help given about how to detect possible problem. Thanks!


texts:
I'm set on using a single Li-Po for a whole 10-servo robot, splicing the power with those Wago connectors into three step-down converters:

5V for Arduino Uno & PWM driver with 7 servos (6V would be acceptable as well for both, I believe),
6V for 2 servos for that precious torque,
7.4V for a higher range (6-8V) servo.

I can't quite imagine though, if the current distribution will be so convenient to just feed everything with what's needed. Cases of voltage drops and interference with Arduino seem to be mentioned frequently. I don't have the whole setup yet to see how it behaves, but even at this stage I could use some guidance on what would be the measures against potential problems. Also, how would one go about adding possible capacitors or forming the often-recommended star ground when the current could be above the capacity of a good ol' stripboard?


texts: What is the RMS current going through this fuse?

texts:
I'm chose a fuse to for a transformer, and now I'm trying to calculate the cross section of the cables. I'm using the following formula:

Where Tk is the protection time, Ik the short-circuit current and k the constant of the cables. Ik = 20.2 kA, Tk =0.3s and k=94. What I got is s=117,7 mm2. And since the fuse is a current limiting fuse, I want to calculate the cross section of the cable after the fuse using this graph:

The transformer is 10kV with 400kVA, so the manufacturer recomends 80A fuse. And from what I understand of the graph, the maximum current that goes through is roughly 9kA with 3.53 kA rms. Using this values and that formula I think that s=20.6 mm2 but according to the example my professor showed s = 38.3 mm2. I can't understand how he got that value. The fuse is a Schneider Electric Fusarc CF 80A.


texts: Correct way to measure power consumption in AC

texts:
Just in case: Sorry for the bad English.
I'm trying to do a power consumption data logger. But I don't understand the calc behind this. I got more confused reseaching on internet.
Firts, there is three types of power: Apparent, reactive and real.

Which of these do I have to consider?
How do I measure each one?

I took this class many years ago, I don't remember anything. I know tha power is P = V * I, but the type of power keeps me insecure.
Also. If my sensor registers 500 watts every second:

Do I need to sum to get total power in one hour and get watts per
hour?
Make sum and make average per hour?
Convert watts per second to watts per hour and sum?

I will use an ESP32.
For the sensor of current and voltage, I'm still considering the model.


texts:
I'm sorry if this question seems extremly dumb or/and pathetic. I'm quite new to electronics.
For one of my electronics projects, I want to buy a power supply like this one, but it says Output: 12V 2A and I know that 2 amps is dangerous for the human body.
So what does it mean? Will I hurt myself if I touch the two cables or is it fine? I don't really understand this.
I'm sure you all know the answer and if so, please explain why.
Thank you!

EDIT: My question has been marked as a duplicate but it's different. The other question is about what voltages / currents are dangerous but I do now that. However, I'm asking if the 2A power supply always outputs 2 amps or if it is the maximum current it CAN output.


texts:
I have this scheme.

I have calculated the resistance of coil and capacitors. This is the source:

And here are my equations about the upper node(U1). Are they right?


texts:
Using CMOS inverter with crystal and cpacitors, we can make a oscillator. And i find many docs mention the method 'negative resistance'. But, they are not all the same.

The method from TI's doc: Use of the CMOS Unbuffered Inverter in Oscillator Circuits, it separate the circuit as below:

The method from ST's doc: Oscillator design guide for ST microcontrollers, it separate the circuit as below:

Beside the differences above, there are some other differences:

TI's method use the voltage gain of the inverter, ST's method use the \$g_{m}\$ of the inverter.
TI's method has some limitations on \$R_{f}\$'s value, but in ST's doc, it only say \$R_{f}\$ is used to bias the inverter, but it seems it has no clear 'limitation' on \$R_{f}\$'s value.

I'm a bit confused, what's the 'source' of the differences?


texts: TRRS 3.5 mm Audio Plug (male) into a printed circuit board

texts:
Have a device I'd like to plug into a headphone jack of a cell phone. Wanted to start making some more professional prototypes; print my first circuit boards, etc.

I'd like to be able to implement a male headphone plug like this into my PCB:

Note that this is male.

Notice how the places to solder are super fricken tiny. What's the best way for me to connect this to a circuit board with the least amount of effort? I don't have the manual dexterity to solder DIP pins onto these areas in a quick and efficient manner (do I need a better soldering iron?).

Or is there an SMT way to do things (I don't see how there could be given the barreled nature of these components)?

Lastly, maybe there is a breakout of some kind for these somewhere out there? I can't find any.


texts:
Can anyone explain the given circuit.
I seem to have done it and its perfectly working. But can someone explain the principle/theory and working behind this circuit from when the switch is turned on..
And I also didn't connect the LED

If I bring a fluroscent light near it.. It glows

Pls explain that phenomena also..


texts:
Currently I have a project that consist in the following:

We have 2 USB Led lamps. (e.g 13 leds, 5V, ~200mA)

To these lamps, we would like to control the intensity of the light, through a Raspberry PI.

My main question would be what would be the simplest and cheapest way to achieve this?

So far from what I have seen in internet a digital potentiometer would work on this, maybe using a DS1669 or a AD5204.

Sorry if this question is too stupid, but I'm out of my field here, and I would like some suggestions as how to go about this. So if anyone is willing to put me in the right direction.


texts: Making Daughterboard Symbol and Footprint With Multiple B2B connectors

texts:
I am using Allegro/OrCAD.

Suppose I have a PCB module like the one below, which contains multiple B2B connectors and is meant to mount to be plugged into a larger PCB:

Each B2B connector has its own footprint on its own (when used individually). However, in this case, both need to be associated to the same component symbol with a fixed relative positions.

Now, I could make a completely unique footprint dedicated to this component symbol, but it would be convenient to be able to make use of the footprints for the individual B2B connectors.

I do not believe there is a way to have a schematic symbol associate with multiple footprints (or multiple instances of the same footprint). But is there a way to make a "super footprint" that internally uses the footprints of the individual B2B connectors?

If there is, that also raises the issue of how to associate pin numbers between symbol and footprint since the same pin number would appear multiple times in both the symbol and the footprint since the individual B2B connectors appear multiple times.

Are footprints and symbols just the wrong approach to this? Is this something for hierarchical design instead? As in:

make a schematic with the symbols for the B2B connectors, and turn that into a block.
Then export that netlist into the PCB layout and properly space the B2B connector footprints.
Then somehow turn that PCB layout into a block or footprint that can be dropped into other designs?


texts: How to choose what a power supply to drive 2 x 10watt RGB LEDS?

texts:
I'm trying to figure out how to determine what power supply I should be using for different types of LEDs for this and future projects.

I have 2 x RGB LEDS:

Forward Current: 350mA

Forward Voltage:

RED: 6V - 6.6V
BLUE: 9.6V - 10.2V
GREEN: 9.6V - 10.2V

I want to run these in parallel with a power supply and was thinking something along the lines of using an LED Strip power supply as my main power source that is 12V - 2Amp - 25 watt.

I'm going to use an arduino and attempt to dim them using PWM with a transistor.

What's the best way to gauge a power supply unit for high powered LEDS including putting them in parallel?

My understanding is that if I'm drawing 20 watts of power, ideally a power supply should be able to output slightly more than you're drawing. The same goes for the amperage?

Is using this LED Strip power supply a bad idea?


texts: boost converter with overvoltage protected output

texts:
In my device 6.5V is generated from 5V USB. This can be done by boost converter, but if something goes wrong (external resistor voltage divider break up), due to overvoltage output condition (for example 16V) all parts connected to boost converter output will be destroyed. Output should never go over 7V.

I am looking for bullet-proof solution (low cost and minimum number of parts, of course). Required current is about 100mA, and efficiency is not so important, because this part of device is used very rare, and it is active during short period of time (1 second).

Closest one that I found is tps61220, but per datasheet, maximum output voltage is 6.0V, while overvoltage protection threshold (internaly) is in 6.0-7.5V range. I am afraid that due to output voltage close to 6.5V, overvoltage condition will be fired non-stop.

I am not interested in boost converters where overvoltage protection treshold is defined by external resistors, because again there things can go wrong.

I can use (100 mA) voltage doubler (charge pump) from 5.0V (USB) to 10V, and then regulate it down by LDO to 6.5V. Or regulate 5.0V (USB) to 3.3V by LDO and than double it by charge pump to 6.6V.

Edit:
Let say that due some reason one of 0603 on board resistor fail. Board will not work anymore, but failing of this resistor will not cause any other damage. After replacing this resistor board will continue to work normally. There is LDO (5V from USB to 3.3V or lower voltage selectable by user) on board that can fail, but 5V passed from USB directly will not destroy the board. With boost converter this is not a case, and failing (because of any reason, with overvoltage on output) will destroy board (almost) completely.


texts: Why are digital oscilloscopes still so expensive?

texts:
I'm a beginner in hobby electronics and I am wondering
why digital oscilloscopes are still so expensive?

In times of cheap GHz CPUs, USB 3, ADSL modems, DVB-S receivers, blu-ray players which all of them have remarkable clock frequencies/sampling rates it makes me wonder why a digital oscilloscopes which is capable sampling signals of a bandwidth of 10MHz are still very expensive, 100MHz is already high-end.

How can this be explained?
What differs the ADC from an digital oscilloscopes from one of the devices mentioned above?


texts:
I am working on an amplifier based on 555 triangle generator, a comparator and the IRAUDAMP1 as a guideline.

My problem is that i have high DC offset voltage at the output (-1.6V).
What is the cause of this?

Is the problem right at the beggining, on the comparator circuit?
Is the only way to fix this to use separate inductors for filtering for each mosfet?

LATER EDIT

The problem was the 555 generator. The exponential triangle causes DC offset problems.


texts:
I was trying to implement the watchdog functionality using ASF in an SAMC21 xplained pro and after flashing the code the device started behaving oddly. If I try to run any code it looks like it is not doing anything.

If I try to start debugging it goes directly to Reset_Handler function.

I tried erasing the hole code and also disabling the watchdog timer in the fuses but nothing changes.

What can I do, or what other information should I provide to get help with this issue?


texts: When -EMF is induced can we keep current the same?

texts:
I'm confused at how Back EMF or (-V, -EMF) reduces current, and conserving the overall power. Let use the following simple example to help my understanding:

A solenoid produces a magnetic field B, it consumes 300W to produce it. With 100Amps flowing at 3Volts, it has 100 Turns. A magnet with B = 0.5Tesla moves around very quickly at 0.100 Seconds, now the area of the solenoid is = 0.15 m^2 so we can use Faraday's law to predict the EMF induced within the solenoid, EMF = -N (BA)/t, thus EMF = -75V, what will happen to the input voltage and current and power?

Even if there is change in B, can we still stabilize the power at 300W? Or keep the current the same? In order to keep I stable at 100 A, what must be done?

If it is possible.


texts: I am considering a dual-Vdd circuit design, Vdd_H is 0.6V, Vdd_L is 0.35V. I understand that I need level-up shifters to convert the Vdd_L domain signals to Vdd_H signals, to have enough drive. While I am not sure do I also need a level-down shifter to convert the Vdd_H signals to Vdd_L ones? Any help will be much appreciated.


texts: I am diode testing Zener diodes and getting conduction in both directions. Does this mean that the diodes are bad or is the diode test just allowing the breakdown voltage to be reached thus causing conduction?


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If anyone has worked with the CAN MCP25625 chip in the past I would like to know if in the loop back mode if we load and send data on the TXB0 buffer are we supposed to receive a RXB0 buffer ready and filled with data in the TXB0 buffer?

If yes, following are the steps that I am doing,
1) Send MCP25625 to LOOPBACK MODE by setting the bits 7:5 for sequence 010, given in the datasheet. I reverify by checking up the CAN Status bits and the bits 7:5 show me a 010.
2) After I successfully load and send the data onto TXB0, I don't receive a message ready signal which is why I am unable to check the RXB0 buffer. On force checking it I find that the data is junk i.e. the LoopBack functionality did not perform.

Does anyone have an insight on what else I should check to debug this? Has anyone run into trouble with this earlier.

Additional information: The way I am checking this is with the USB MCP2210 SPI behaving as master and using that to drive the MCP 25625 slave device.


texts: Floating ground when mosfet is off - is this a good design choice?

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I am designing a simple circuit for weight controller and I am not sure where I should connect the drain of N-channel mosfet. My goal is to design a circuit that when powered off (both when button BN1 and pin B6 are low) should be inactive and drain nearly zero amperes (few microampers is fine).
One of my attempts look in a following way:

+12V and FGND is where a 12V acid battery will be connected to, and VCC (3.3V) and +5V are outputs of voltage regulators. The R25 and C23 duo form low pass filter to prevent double clicks when clicking the buttons. R22 is there just to provide a way to discharge capacitors C28/C30/C27/C25, but I am not sure if it is helping much.

I am not confident about this design choice. Especially what happens when both MOSFETs are turned off and ground slowly reaches 12V - what exactly will happen to the outputs of the voltages regulators? Will The PD across VCC/GND go negative? Can this negative PD cause damage to the unipolar capacitors C27 and C28? How can I improve this design?

My second design, which looks a little better to me:

12V battery is connected to +12V/GND, RelativeGND is connected to the voltage regulators.

I don't like how the voltage regulators work with two different grounds. For input, the relative ground is used, and for output the real GND should be used, but I feel like this is not how the voltage regulators work, and that this may give me slightly increased PD across VCC/GND and 5V/GND pairs than the datasheet describes. Any feedback?


texts: I'm trying to learn how to use a VNA to get the impedance and smith chart for a given antenna.  I'm working at 2.4Ghz do I just need a VNA that operates up to 3GHz or is there some reason that I need a higher input bandwidth?  I'm trying to play along with this article here.


texts: Is there an equivalent EE term for "homeostasis"?

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In biology, homeostasis is the state of steady internal physical and chemical conditions maintained by living systems.

Is there an equivalent term for a circuit or electronic device?  So that would be constant supply voltage, surrounding EMI field, ambient illumination, temperature etc., etc.


texts: Measuring the mic signal of a computer headset

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my colleague and me have hit a brick wall - and are hoping somebody can help us out here :)

Following scenario: We record some data using a computer with an NI card and some signal transducers. We need to record audio from a mic of an headset synchronously. First thought: Build a patch cabel for the headset. Measuring the mic signal to GND - no problem. However, the signal is offset by about 2.65V. My guess this is the necessary voltage for an electret microfone.

To get rid of the offset we then thought to measure the voltage between supply and mic signal. However the difference is 0 - a look with an oscilloscope confirmed that. Can anybody help explain, why supply as well as mic signal on a headset carry the signal information?


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I would like to inject 10 μA into my load, and to be able to switch the current on/off at up to 10 kHz. My first attempt is just based on the transistor current source in Horowitz/Hill.

simulate this circuit – Schematic created using CircuitLab

The relay switches the base between ground and a regulated 5V supply. The load current would then be (Vb-0.6)/R1, which is ~10 uA.

Two questions:

(1) First, since I have little experience in this area, is this approach even reasonable?
(2) If so, how can I predict what switching speeds I could achieve?


texts: How to control cd-Rom 3 phase Sensored BLDC Motor with arduino

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I have one of these cd-rom bldc motors:

I would like to control it using a mcu. However, I am not sure how I would wire it up. I found this post doing exactly this, however a 3-Phase BLDC motor bridge is required to drive it, which can be built using a few mosfets and transistors. But I am sure there is something like this already available but I couldn't find anything suitable for my application.

Are there any simple 3-phase bridge bldc motor bridges available and if there are how do I wire it to my cd-rom bldc motor?


texts: Detecting which IR detector was triggered using one pin

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I have a project that has 6 IR led's and detectors.

The project needs to detect when any of the 6 beams get broken, and exactly which one got broken. I would like to be able to use only one input pin to detect if any of these have been broken.

What kind of hardware setup would I need to achieve this?

Some more notes:
Currently a high is read when the beam is interrupted.
The actual breakage in the IR beam is extremely short. (A falling coin)
My preferred method would be to use an interrupt if this is even possible.