texts: Why would a power supply mess with my scope?

texts:
I recently bought a 0-35V 0-3A (105W) CC/CV linear power supply, made by Takasago in Japan, second hand. It's a nice unit, and inside of it is a massive power transformer along with three pass transistors on a very large heatsink (it is interesting why there are three transistors but I can only suspect that they are to reduce the load on an individual transistor), and it weighs a ton. I've fully tested it to 105W, although only for about 5 seconds as even my 2x25W resistors were getting too hot.

I originally had plans to put it on top of my HP 54501A, a digitising oscilloscope with a CRT raster monitor (unlike a normal CRT scope which draws a trace by moving the electron beam - this sets pixels on and off representing the trace.) However, I found that when turned on, whether above the scope or on the bench below, the CRT would have a weird ripple effect or would shift position randomly. It didn't matter if the supply was loaded down or not. The trace was not affected, just the display (even text and graphics). Why would the supply cause this? I suspect it has something to do with the transformer because that makes a humming sound in operation if you listen carefully.


texts:
Based on figure.

Maybe a simple question, but I'd like to know why that if forced  response is zero, then

$$\omega L = \frac{1}{\omega C}$$

where \$L\$ is the inductance and \$C\$ is the capacitance.

Where in this case, \$\omega\$ can be solved for to obtain the answer.


texts: Better to use coil relay or remanent core relay for hi-fi audio switching?

texts:
I am working on a hi-fi audio component that needs to switch line level signal. If I am using electromechanical relays to do this, on the assumption that that will provide the least effect on the signal, then I would seem to have a choice between two different kinds of latching relays. One is the coil-based relay, and the other is the remanent core relay. Which of these would be the best choice to minimize any effect the relay might have on the signal?
Note that mainly concerned only about the steady state effects of the relay. Effects that would occur as the contact goes on or off are less important.


texts: 12 bit vs 14/16bit ADC for ph sensor interface

texts:
I am making a ph probe interface board for a project. What resolution ADC would you recommend? I am definately going with at least 12 bit, but is it worth it to go with any higher resolution?

What are the implications of using higher res? Does the input need be more stable? Obviously the cost is higher, but am I gaining anything to begin with? Would noise be too high for the extra resolution to be useful?

Are there any ADC's/ic packages that can directly read the small signal voltage from the ph probe(differential) and perform any gain/buffering of the signal as well as perform the digital conversion? Otherwise, I need to design this with opamps. Any recommendations in terms of design for this?


texts: GHz class sampling oscilloscopes on the cheap

texts:
I was recently perusing Picoscope's line up of sampling oscilloscopes, as they are all way outside my price range, I'd like to have a go at putting one together as a "hobby" project. ("hobby" herein meaning non-commercial, not breadboards and duct tape)

I would like to know from someone more well versed in this area if my idea is even feasible before I go spending $500+ on components.

The heart of the system revolves around a TI THS788 (a glorified 4ch stopwatch with an LSB of 13pS and a dedicated trigger input). Basically, the front end consists of several really fast comparators (most likely the HMC674LP3E). You set your trigger level on one comparator, which when triggered, starts the THS788 counting (or really sets 'zero time' as it's a free running timer).

The other 4 channels each have their own comparators and associated reference DACs, you set each comparator to trigger on a slightly different voltage and the THS788 records the time delay from the trigger. (with all differential signal lines properly length matched of course, we're dealing with picosecond delays after all)

By repeating this process over and over with slightly different setpoint voltages on the input comparators, you can build up a picture of the waveform (or at least it's rising edge). As the THS788 has 13pS time granularity, this would in theory give you an Equivalent time sampling rate on the order of 75Gsps (and the input bandwidth of ~10GHz on the comparators helps too). That'd allow for some pretty decent TDR measurements and/or eye diagrams provided that a fast enough pulse generator was available.

So should I dust off my box of K connectors and 40Gig semi-rigid or am
I getting ahead of myself?

simulate this circuit – Schematic created using CircuitLab


texts: Power supply BT-153 displays wrong voltage

texts:
I have a BT-153 bench power supply (0-15V, 0-3A, see https://www.conrad.com/p/basetech-bt-153-bench-psu-adjustable-voltage-0-15-v-dc-0-3-a-45-w-no-of-outputs-1-x-393647) which displays an incorrect output voltage when under load. I wonder if it is broken, just poor quality or if I am misunderstanding what this power supply is supposed to do or show me.

When measuring the output voltage without a connected load, the displayed voltage matches my multimeter measurement to within a few tens of mV, so all is good. When setting, for example, the voltage to 12V and setting the current limit to max, a 12V / 20W light bulb draws around 1.5A, and the power supply and my multimeter agree to within 10-20 mA.

However, after connecting the bulb, the power supply still displays a voltage of 12V, whereas my multimeter measures around 10.6V. When connecting another, identical bulb in parallel, the current increases to 2.93A (multimeter confirms), the power supply continues to show 12V, but the multimeter measures 9.4V.

I am confused as to what the power supply is doing: it appears to show the value of the desired voltage, and even though it should be able to deliver 12V and 1.6A, it can't, but refuses to inform me about this. I expected that (a) the power supply's voltmeter acts like a multimeter, showing the actual voltage, and (b) that the voltage will not break down when the supply is put under a load of 50% of its nominal capacity.

Is this simply poor quality or misguided expectations on my behalf or am I misunderstanding what is going on?


texts: Why does this common-source MOSFET amplifier work?

texts:
I have built the MOSFET amplitude modulator shown in the bottom right onto another class C oscillator tube circuit, and it does work. I am having trouble understanding why based on what Ive read.

MOSFET amplifier http://danyk.cz/avttc001.png

It seems to be a common-source amplifier, but doesn't seem to have any Rd, or Rs, or even any power supply rail for that matter (the centre point of the tube filament should be at 0V, no?)!! Despite the fact that it seems to use a potential divider to provide bias for the gate.

I also rebuilt it on a tube circuit that has a separate heater and cathode, and rectified the heater supply to provide the MOSFET a power rail, and took the output access an Rd that i added. This makes the MOSFET run much cooler (I assume this is by providing sufficient voltage for the divider to get the gate to a reasonable q-point.

If my interpretation so far is correct, what is the consequence of not having an Rs between the the source pin and ground? Should there be one, ideally? Can I still add a bypass capacitor (I guess it's not a bypass capacitor since there's no Rs) between the source pin and ground to increase high frequency gain?

(PS - An afterthought, does it make more sense to think of the whole circuit as a cascode?)


texts:
I work in developing software that integrates with GPS and Galileo receivers. I've struggled for years with inconsistencies in documentation for the NMEA emitted by such receivers, and I've decided to put it to bed.

Is it true that, since GPS is a digitally modulated signal, signal-to-noise and carrier-to-noise are equivalent values for any given receiver? Is this the case for other GNSS systems?

I have done some reading but I am not an electrical engineer.


texts:
I'm designing a 2nd order low-pass Butterworth filter using a Sallen-Key topology (for reminder) :

simulate this circuit – Schematic created using CircuitLab

Now, I am trying to find the optimum values for the components, given that :

\$ \omega_0 \$ is known
\$ Q \$ is known (\$ \frac{1}{\sqrt{2}} \$ if I am remembering well)
The input impedance should be maximum (with reasonable component values, of course)

Is there a tool available that is able to give the optimum values with these constraints, or am I better off coding a little program that can give me the answer ?


texts:
I have a set of laser-modules with integrated drivers that I want to setup in series. The datasheet says the maximum voltage for a module is 3.3V. Two run two modules in series I doubled the voltage from 3V to 5.8V, otherwise they would not light up. Does this damage the modules or is the voltage shared evenly between the modules?

The datasheet is available here http://www.egismos.com/laser-modules/IR-laser-module-D985030L.pdf


texts: What would be the best way to convert 20V DC to 9V DC? Can I use a simple potential divider network and regulate the output? If not, then what's the harm in it? I intend to use the output to power my AVR development board. I've seen people using complex DC-DC converters. What are the advantages of such devices over normal potential divider network? Please help.


texts:
I'm pretty new to electronics and the first thing I want to have on a PCB is a simple signal source (sinusoidal 12V RMS ; 100 Hz Frequency). To not blow things up I want a current monitoring circuit which should disconnect the source if the load exceeds about 500mA. I came up with the following idea, but since I'm new I'd like to have some review on this:

(Better resolution)

The circuit should output a LOW signal if the current on RL exceeds 500mA and a HIGH signal if the current is not exceeded:
$$I_{max} = 500mA$$

The root mean square of the signal is 12V:
$$U_{RMS} = 12V$$
The amplitude is approx. 17VDC
$$U_{peak} = \sqrt{2} \times U_{RMS} = 16.97V \approx 17V$$

The maximum load is therefore 34Ohms:
$$R_{Lmax} = \frac{U_{peak}}{I_{max}} = 34\Omega$$

I'm planning to use a one ohm resistor to monitor the current:
$$R_{shunt} = 1\Omega$$
$$P_{shunt} = I^{2} \times R = 0.25W$$

If current is exceeded, the voltage drop across the one ohm resistor should be around 0.5V:
$$U_{shunt} = 1\Omega \times I_{max} = 0.5V$$

I'm amplifying the voltage with the factor 5 to get exactly 2.5V if the current on the load is 500mA:
$$V_{1} = \frac{R3}{R4} + 1 = 5$$
$$U_{OPV1} = U_{shuntmax} \times 5 = 2.5V$$

The comparators have the following supplies:
IC1A & IC1C have +UB=5V and -UB=-5V.
IC1B & IC1D have +UB=5V and -UB=0V.

I know on the schematic all amplifiers have the same IC "name", I didn't bother to change this :(

The comparator IC1C inverts the signal to detect 'reverse' overload current (-500mA results in -2.5V).

Then I'm comparing the 2.5V with both comparators to check if the current is exceeded or not.


texts: Can a home security system be built with an arduino? (40 sensors maximum, usb interface to pc)

texts:
Considering these requirements:

40 modules or sensors (one movement/presence sensor or one windows/door open/closed sensor)
read state (boolean, or 0/1) of all modules as fast as possible (once per second would be ideal, but once ever 2 seconds is acceptable)
keep list of sensor states in memory at all times
send the status update via usb cable to a pc
receive commands via usb cable from a pc and reply
maximum length between the arduino and a sensor - 50 meters

can this be built with an arduino-based system? or are these too many sensors?

Sensor details:

hall efect sensors for doors and windows http://www.sparkfun.com/datasheets/Components/General/Hall-US1881EUA.pdf
motion sensor for rooms

Updates:
1 - hall effect sesnsor added, looking for motion sensor


texts: Negative voltage in Mesh Current Analysis

texts:
I am trying to learn about Mesh Current Analysis and have a question

I was reading this explanation on the subject from electronics-tutorials.ws:

http://www.electronics-tutorials.ws/dccircuits/dcp_5.html

and one of the equations is \$-20 = -40I_1 + 60I_2\$

I understand where \$-40I_1 + 60I_2\$ comes from, and I'm assuming -20 is taken from the voltage and it is given as negative because the loop goes clockwise, can someone confirm why -20 is negative, please?

Thanks


texts: To what extent are "pure sine wave" power supplies marketing spin?

texts:
Recently, I've noticed a trend in power supply manufacturers touting their PSUs (generator or battery inverter etc.) as having a pure sine wave output.

I've also seen people saying that warranties will be invalidated if devices/motor homes etc. are connected to anything other that a power source with a pure sine wave output.

I wonder what the world did before such power sources existed.

Is there science behind this? Surely a standard petrol generator with a good automatic voltage regulator (AVR) or an old-fashioned coil regulator will be enough to stabilize the output to run sensitive electronics like LCD televisions or computers?


texts: Indoor / outdoor solar cell (Amorton): maximum light conditions

texts:
I am currently searching for a proper solar cell to power an IoT device (just a simple logging device). Although it is just for my own usage, the sensor should be properly engineered.
My main requirements are the proper size and type of the panel. The size comes from the desired max. size of the PCB and the type (indoor/outdoor) is yet to be chosen.
The sensors will be used mainly outdoors, which is why I wanted to use an outdoor cell. Unfortunately, the standard sizes of the indoor cells provided by the manufacturer fit much better than the outdoors cell dimensions (as a private person I of course want to get away with a standard article, that can be simply ordered by e.g. mouser or digikey and no custom solution). 3
So, since I have only found an indoor cell that fits well regarding the form factor, I am investigations any reasons, on why I should NOT just use an indoor cell.
Towards this way, I found 1, and 2.
The answers provided more or less all say that the relevant difference will be durability (UV and water resistivity etc.).
I am not convinced yet - especially since the datasheet 3, the section for the indoor panel explicitely states:
"(Since Amorton is designed for indoors use, please it under 1,000 lux.)".
Now, that rather clearly suggests to NOT use indoor panels outdoors, because outdoor light levels will be much bigger in any case.
Can anyone tell me, why higher light levels are a problem or even critical for the indoor panels?


texts: What Is The Correct Way To Recombine A Split Serial Signal?

texts:
I am trying to replace the lamp and ballast assembly in an Acer P1500 DLP projector. The ballast is an OSRAM PT-VIP-05 COMPACT. It features a UART control scheme that allows the motherboard to query and set various parameters intelligently. I've been able to find the datasheets for both the ballast module itself as well as the specific protocol it implements via the UART. The issue I'm having is that I can't quite figure out how to "reverse" the weird way that the Tx and Rx lines are sort of split for lack of a better explanation.

This is the schematic, per the OSRAM datasheet:

I need to replace the left hand side of the schematic with an Arduino or similar, the code and wiring and such I can absolutely handle. What is giving me trouble is correctly getting the Tx and Rx lines to neatly convert to the "standard" 3-pin UART interface we all know and love (GND / Tx / Rx).

Can anyone help me make sense of this?

For additional reference, I did find some information here but the forum is in Russian and there's a lot lost in translation I think. There are also some hints here, and here.

Those pages reference the datasheets for the OSRAM Standardized UART Protocol as well as the OSRAM 5-Pin Interface, both of which I've uploaded in case they're helpful to anyone who needs them or is willing to help.


texts: Switching cold cathode fluorescent lights on and off without relay?

texts:
I have a few sets of 2-in-1 CCFLs that are designed to be powered off the 12V rail of a computer PSU. I'm planning to build a large 7-seg display using them so I'd like to be able to switch them on and off independently using an Arduino and ideally a MOSFET. The problem is that two CCFL's share the same inverter so I can only wire a MOSFET in after the voltage has been upped.

I tried to measure the voltage coming from the inverter to no avail, I'm not sure if the supply even gets converted from DC to AC? The tubes draw around 500mA each.

I have experience with Arduino but am not well versed in electrical engineering, so my question to anyone that would answer is what would be the best way to switch these off independently?

Should I buy extra inverters and switch at the 12V or is there a way I can use the existing inverters and switch after the inversion? The cheaper, the better!


texts: What tests, certifications and labels do I need on my new electronic gadget?

texts:
I have designed a VERY basic lighting gadget -- it's basically a flashlight. It turns on and off with a switch and is powered by a rechargeable Lithium Ion Battery via USB cable. It consists of LED's on a PCB and has a switch to stop charging in order to keep the battery from overheating.

I know I don't need FCC as there is no radio transmission. I know I will need CE for Europe, but am uncertain about what I need for the USA and Canada? I have spoken with UL and gotten a quote, but they won't tell me what exactly I need until I pay and it's extremely expensive.


texts: Beginner question about measuring current using digital multimeter

texts:
I have a beginner question about using multimeter to measure a current. I have dc motor, attached to 2 x AAA batteries.
Which reading I should use, 200 m under DCA or 2000 mA?
On 200 m, the current reads 15
On 2000 mA, the current reads 150.

Which one is the correct way of measuring the current?
For batteries current, do you use 200m or 2000mA?


texts: Determine the PROM programming pattern for the memory system using TPB28L42, 512x8 PROM as an address decoder

texts:
Question

  The following figure shows a memory system using the TPB28L42, 512x8
  PROM as an address decoder. Determine the PROM programming pattern for
  the circuit.

My Problem

My classmates and I have very different understanding of the programming pattern of a memory system. I think that the following programming pattern is a kind of truth table. A15, A14 and A13 cannot be changed arbitrarily in this question since the real circuitry inside the TPB28L42 will not change according to what we think. My classmates just directly put the higher 7 bits of the address into the table. Why? It seems so odd. Is programming pattern not a kind of truth table?

F0  =  1111  000 0
F2  =  1111  001 0
FC  =  1111  110 0
C6  =  1100  011 0
F8  =  1111  100 0
FA  =  1111  101 0
F4  =  1111  010 0
FE  =  1111  111 0


texts:
I need to connect two circuits that use different PSU voltages.
The first is a microcontroller clock generator, it outputs a clock 0V to 3.3V at 150KHz as maximum freq.
I need to connect this clock to a CD4047 (pin.3) on the second circuit. But the second circuit uses negative supply voltage and I cannot change that. So the CD4047 is powered with -15V and 0V.
Obviously it won't accept my clock as is.
I think I need a level shifter that converts the positive level of the clock to -15V or lower (I don't mind about the phase of the clock).

I tried the circuit shown in Figure 2 here:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/4414
I used a LM393 instead of the comparator used in that schematic, and powered it with 0V on pin 8 and -15V on pin 4
But it didn't work, maybe I got something wrong

Do you have any example tha I could use, or a different approach to do this task?
Thank you


texts:
--Background--

I'm setting up a pretty standard RS232 interface from a digital caliper to a microcontroller, via a MAX232 chip (or in my case, MAX3222, which is the 3.3V-supply variant with 2 transmitter pairs and 2 receiver pairs).

The only thing non-standard about this particular caliper though is that it uses an Opto-RS232-cable, which specifies connections as follows:

The RXD and TXD connections are obvious.

And DTR is for [Power +] so I connected it to T2-OUT on the MAX chip, thus I can write a HIGH on a MCU pin connected to T2-IN ==> thus T2-OUT will be at +5-15V.

Thus, my connections so far look like this:

--Question--

Is there a simple solution for the one remaining connection: RTS?

It's for [Power -] and requires an OFF/LOW of voltage level -5 to -15V.

But unfortunately, there are no more RS232-receive-pins left (T1-OUT and T2-OUT are taken already). I could use a chip like MAX3246 with even more channels but that would add to BOM cost.


texts: How to test if a Near Infrared Emitter and Photodiode still working?

texts:
I suspect that my NIR emitter and Photodiode are not working.

Emitter http://www.thorlabs.com/thorproduct.cfm?partnumber=LED1450E
Photodiode http://www.thorlabs.com/thorproduct.cfm?partnumber=FGA20

For emitter circuit, I connect it to 5V and a 200 Ohm resistor, to try to achieve a voltage drop of 1.2V and current rating of 20mA (according to datasheet)

For Photodiode, I tried to bias it as the circuit in the datasheet also.

Would you please showing me how to test if they are still in good condition.(For the NIR emitter, my phone camera cant capture anything).


texts: Maximum length of Atmel AVR ISP ribbon cable?

texts: I recently picked up a cheap USB based ISP (in-system programmer) for Atmel AVRs.  There are two variants of the programming socket that are used with these devices, a 10-pin and a 6-pin.  Unfortunately my ISP only came with a 10-pin cable, whereas most of my devices use the 6-pin socket.  It is pretty easy to construct a 10-to-6 pin adapter (the signals are the same, they're just physically arranged differently on the larger 10-pin connector) and I would like to make a 10-to-6-pin ribbon cable.  What is the maximum length that I can make it?  (It came with a fairly short cable, about 8 inches, and I would like to slightly lengthen this if possible, to 1 or maybe 2 feet.)


texts: Solve for the current in the following circuit using superposition

texts: I understood why \$i_1\$ is equal to \$V_1/(R_1\parallel R_2)\$. But, I can't understand why \$i_2\$ became right that. Would anyone explain why \$i_2\$ is not \$-V_2/(R_2\parallel R_3)\$ (since I got this answer in my calculation)? Or, can you just describe why \$i_2\$ is \$-V_2/R_2\$?


texts: Do I need to connect the battery to send data to an ESP32 chip?

texts:
This may be a basic question, but I'm really new to electrical engineering.

I got an ESP32 chip with no micro-USB port. I got with the device a 3-Wire cable one side and USB other side. I have to connect these 3 wires respectively to TXD / RXD / Ground.

So, to transfer data to my chip, do I must add a battery (connected to 3.3V and GND) to power it up ? Or just this 3-wires cable is enough ?


texts: Bad Waveform on Output of Buck Converter

texts:
I have designed a buck converter (poorly) and have been getting terrible noise. I made a post here where I was given suggestions on how to do a proper layout for my buck converter. This post also lists my schematic, board layout, and external components used.

But when probing around more with my oscilliscope I noticed that the output of the buck converter that goes into the inductor doesn't look quite right. I compared it to a buck converter that I designed that I believe is operating well.

It seems I have this terrible "ringing" on the output, and I do not believe this is correct. I was wondering if anyone has any insight as to what is happening, and solutions to relieve it if not listed in the previous post. Thank you all for your help!


texts: Teensy 3.2 receives garbage values from HM-11 BLE module

texts:
Recently purchased an Hm-11 BLE module, and connected it to a Teensy 3.2.

I can see the BLE module (AnyFlite) on my phone using the MSMBle app.

The following code was used to initialize it:

#include <SoftwareSerial.h>
SoftwareSerial mySerial(7, 8); // RX, TX
void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
  Serial.println("Goodnight moon!");
  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);
  mySerial.println("Hello, world?");
}
void loop() // run over and over
{
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
  if (Serial.available())
    mySerial.write(Serial.read());
}

When opening the Serial monitor, I see the "Good Morning" text, however when sending AT commands there is no response. There is nothing received on the phone app either. (when connecting all I see is received text: 00

Upon sending commands from my phone to the module, I see garbage values in the serial monitor.

My understanding is that this is caused by a baud rate mismatch.. I have cycled through all the Baud rates and still face the same issue.

I checked the voltage between ground and vcc of the module and it is at 3.3v, which is what is required.

Exhausted all troubleshooting options.

EDIT

Changed to the following code when I was told about UARTS:

#define HWSERIAL Serial3

void setup() {
  Serial.begin(9600);
        HWSERIAL.begin(57600);
}

void loop() {
        int incomingByte;

  if (Serial.available() > 0) {
    incomingByte = Serial.read();
    Serial.print("USB received: ");
    Serial.println(incomingByte, DEC);
                HWSERIAL.print("USB received:");
                HWSERIAL.println(incomingByte, DEC);
                HWSERIAL.write(Serial.read());
  }
  if (HWSERIAL.available() > 0) {
    incomingByte = HWSERIAL.read();
    Serial.print("UART received: ");
    Serial.println(incomingByte, DEC);
                HWSERIAL.print("UART received:");
                HWSERIAL.println(incomingByte, DEC);
                Serial.write(HWSERIAL.read());
  }
}

When I send an AT command from the Serial Monitor, I get the following:

USB received: 65
USB received: 10

When I send a command from my phone (in this case AT+ADDR?), I get the following:

UART received: 12
ÿUART received: 8
ÿUART received: 13
î

Still, garbage is being output.


texts: Standing waves modes inside a cavity resonator

texts:
Follow up postI have researched the concept of a rectangular cavity resonator and have come across the term modes. For a given frequency one can have multiple modes. What do these multiple modes signify practically? Are some modes better than others?

In addition, when multiple modes do co-exist in a rectangular cavity resonator was does mean. I am not designing a but have got a metal container to which I have fitted an antenna to it. There are multiple modes that co-exist. Is this a bad thing?


texts: Limit the current being absorbed by a battery

texts:
I have a generator that supplies a constant DC 10A current to a NiMH battery pack with 240 cells in series (nominal voltage of DC 288V). This current is too high for any cell once it has reached 100% state of charge (SoC), but I am required to charge past 100% in order to 'top-end balance' the series string of battery cells.

I want to limit this charging current to 1A so that the cells that have already hit 100% SoC don't have to dissipate 10A, which would most likely result in hot electrolyte being vented, and permanent damage to the cell. At 1A charging current the cells that are at 100% SoC can dissipate the current as heat without venting.

I have no way of reducing 10A charging current as the generator's software and control system are locked down. The generator expects to supply 10A and uses a hall effect sensor to make sure that is what it is supplying.

The only way I can see this working is that I waste 9A if the 10A, all I want to know is how to dump this 9A of current, with the remaining 1A going to the battery.

Apart from the rare occasion I need to do a battery balance it is essential that the hall effect sensor is reading correctly. I also need this to be a permanent solution, so rewiring the sensor is not an option. I need a solution that can be bypassed most of the time (such as with a relay/switch), then activated on the rare occasion that I need to balance the battery.

It's a very rare occasion that I will balancing the battery so I don't care that 9A of current is being completely wasted into a resistive load.

Could I use a resistive load in parallel with the battery, or perhaps buffer the generator input current with a capacitor, then switch between a resistive load that will draw 10A for 9/10ths of the time, and then to the battery for 1/10th of the time using a relay/IGBT?

Added - RM:

Here is the lightbulb lighting (& car operating) information that helps put these questions in context. Helpfully provided buried in the comments some while after the question was asked:

The charger and battery is for a Toyota Prius NHW10
(the first Prius which was only sold in Japan).
Battery cells are Panasonic HHR650D.
These are 6.5Ah (when new) NimH "D" (33620) cells.
Data sheet here
They may be arranged in series parallel strings as they are rated at 6.5A max fast charge, but perhaps we'll get more on that at the next information (wiki)leak.

Added - OP:

I can confirm that the battery is one large series string. The car itself will draw up to 110A to drive the electric motor. The highest charge current i've witnessed is a touch over 50A for very short periods of braking.


texts: What is the anode to cathode voltage that corresponds to the holding current?And is the forward conduction current extremely large?I see no limitation besides the forward resistance of the device.


texts: What gives some flash memory a higher speed rating than other flash memory?

texts:
What gives some SD/MMC cards a much higher speed class rating than other SD/MMC cards?

Why are some solid-state "disks" (SSDs) much faster than other SSDs?

I'm hoping that I can take at least some of ideas for storing data faster, and apply those ideas to a data logger design I'm working on that stores (often bursty) data to a few flash chips.

(Ideas that involve re-designing flash memory cells and fabricating new flash chips to work faster are interesting, but are not as useful to me since, alas, I don't own a fab).


texts:
After opening an old webcam I found a lens with a magnetic socket, which is used for autofocus. A coil moves the lens in and out to adjust sharpness.

I recently mounted that feature onto the raspberry pi camera module. Now I want to control the magnetic field of the coil digitally with a PWM signal, which is translated to a analog signal by a simple RC low pass filter see here

At the moment I use a 30uF elko, and an adjustable potentiometer between 0 and 1k ohm, to filter the digital PWM signal. The digital signal from the microcontroller is not directly filterd, but first fed into a stepper motor driver to protect the pins of the microcontroller. The digital output of the PWM is then fed to the RC circuit.

Autofocus does work... although its a little slow. And the problem lies in the relatively slow actuator response. To be a little more speficic: using a PWM frequency of 8khz, and changing the duty cycle by 5 percent, the response is 0.4 seconds for the coil to adjust itself.

I know its difficult to get super fast response without a feedback loop, but I would be happy with 0.1 seconds, if this can be done just by changing some components and values.(Another option would be to find the right amout of overshoot) Basically the RC circuit shall just convert the digital PWM waveform to a certain voltage. It will take some time for the signal to settle to a certain voltage.  The more flattend the output voltage shall be, the slower the filter response. The output of the signal should be as flat as possible, to keep the lens still. So I have to find a tradeoff. What I also intuitively expect is, that the higher the PWM frequency, the better? Of course if its too high, then the power dissipation will also be high. And if there is no power at the coil, then the lens will not move.

Unfortunately I can not give you the data for the coil right now, the only thing I know is that is has a ohmic resistance of 30 ohms. But there is also the weight of the lens, the magnetic field of the permanent magnet, the actual inductance, the spring constant of the recoil spring etc... These are so many unknowns that it would be to difficult to predict an optimal setting.

Now my question to you is, whether it is possible to use variable resistor and capacitor, and just find the optimal setting by trial and error? And if so, what kind of components would you recommend?

By the way: The coil at the moment is quite noisy (8khz). Not that its tedious. But normally an autofocus doesnt make that noise, at least the one in my smartphone. Actually I would rather prefer a noisy but quick response, than a quiet snail.


texts: Control a solenoid position "in / out" with power only (no spring)

texts:
I'm going to use a < 5$ solenoid (vertically oriented) that has to press something.

If I understand well, a linear solenoid like this one:

moves to one precise position when powered, but when you turn the power off, nothing happens (in the case there is no spring ; I want to avoid / remove the spring for mechanical noise reasons out of context here - the system has to be very quiet).

Are there solenoids that:

can move to position "completely out" when a certain voltage/current is applied
can move to position "completely in" when another certain voltage/current is applied (or power applied to another pin)

i.e. are there solenoids that can move back-and-forth with power only and no mechanical springs?

How are they called?

NB: it's not a sourcing question (I can source myself) but I'm interested for the right terminology.


texts: What am I doing wrong when I try to set a switch voltage on LTSpice?

texts:
I was trying to set a switch voltage, I follow in according every tutorial that I've saw on the internet. However, I'm getting the warning saying : "Cant find the the model of SW." But it doesn't make sense, the  voltage switches are in the project and I've put in the spice directive exactly as in the tutorias

What am I doing wrong? Could someone help me?


texts: What happens if the BEMF generated while going downhill is higher than the supposed applied voltage to the motor terminal by the inverter?

texts:
If a brushless DC (BLDC) motor is moving fast ( the case of ebike going downhill,) what happens if the back EMF (BEMF) generated while going downhill is higher than the supposed applied voltage to the motor terminal by the inverter (for example applying low duty cycle pwm to the motor like 5% or 10%?)
Is the motor going to brake or it will go even faster?
EDIT :
as Charles said the motor will brake. I did a small test on my BLDC: I provided 10% duty cycle to the motor terminal and tried to pedal much faster but pedaling become much harder, so yes the motor will try to brake and operates at the speed that the controller is asking for


texts:
I have a NFC chip [Mifare Desfire EV1] which has input capacitance of 17 pF(pico farad).

I got ready-made antenna (Datasheet of Antenna) which has induction of 1.8 uH(Micro Henries).
So by simple formulae when i attach chip to antenna it resonates at 28.77 MHz(MegaHertz).

But I need it to resonate at 13.56MHz. So i am thinking of attaching a capacitor.

So my question is :

  To resonate at 13.56MHz, Do I need to add 59pF  capacitor parallel to Chip and antenna.
  Why 59pF :
   17pF of chip + 59pF c1 => 76pF which gives 13.56MHz


texts: Figuring out IC pinout from the datasheet

texts:
I have an OPA4353 IC, that i want to figure out the pinout from the schematic.
I know this is basic stuff, but since this is the first time I am doing this, and I will be designing a PCB from it, that takes time to arrive and money, I want to make sure I make this right.
This is the image from the datasheet:

And this is the actual IC:

I have labeled what I think is the pinout on the IC, with green numbers.
Is my assumption correct?
I came to this conclusion because the datasheet picture has a circle next to the pin named "1".
I think the actual IC has that circle on the bottom left, therefore I arrived to the conclusion that the pin 1 must be there.
Is my assumption correct?
What about pins 9-16? Are they in the correct order?


texts: Confusion about LiPo charging/capacity monitoring with micro-controller

texts:
I have a LP601730 3.7V 250mAh battery and ATMEGA328 micro-controller. These are the specs for the battery:

 Normal capacity:              260mAh (0.2C discharge)
 Minimum capacity:             250mAh (0.2C discharge)
 Charging voltage:             4.2V
 Standart charge:              Method: CC/CV
                               Current: 0.5C
                               Voltage: 4.2V
                               End current: 0.02C

 Maximum charge current:       250mAh
 Maximum discharge current:    500mAh
 End of discharge voltage:     2.75V

I'm new to electronics and normally if I have an 1amp power supply, the component that is connected to it will 'eat up' only the amount of amps it requires and I have to only worry about providing correct amount of voltage to the component, but as far as I understood, this is not the case for the batteries, correct?

If I understood correctly, I have to provide 4.2V and 130mA based on
C rating of 0.5 or maximum of 250mA, correct? if I connect it to
1AMP power supply, will it:

1.1 - Charge 4x faster
1.2 - Blow up
1.3   Eat only the 250mA it requires?

I want to use ATMEGA's ADC to measure the capacity while the circuit
is discharging. As far as I understood, for LiPo batteries I can
only detect 'rough' estimate, ether it's full / mid / low based on
this diagram if I take voltage as the indicator:

How would I measure current to detect capacity in greater detail without using any special components?

When charging the battery, it seems I can't use the voltage as an
indicator to tell when the battery is charged, since it seems it
stays constant as in this picture, correct? Also, I see that in the
picture the voltage starts off at 2V, does this mean after I connect
the battery to 4.2V, the voltage will drop to 2V 'automatically' and
then take off to 4.2 or do I have to control this voltage with
micro-controller from 2V to 4.2V?

Same question for the current, as far as I understood, the more the
battery is charged, the less current is going to go through and this
current drop is 'set' by the battery, correct?

Thank you for your time!


texts: I am using a bridge rectifier power supply with a 7805 regulator IC for a microcontroller application. A capacitor (2200uF) is used for removing additional ripple. But when the microcontroller uses more power the DC output shows some ripple, the entire circuit draws about 150mA. How can I remove it completely?


texts:
I am currently routing a PCB. I have several chip and several LDO and DC-DC to power those chips.

I am shared between trying to group all those LDO and DC-DC in one area of the board (in the corner) and then distributing the power using some rail on the power plane or to each chip, or to bring the LDO or DC-DC close to each chip they supply without making an area on the boarder being specifically dedicated to the design. What woudl you recommend ?

Here is a picture of the layout board at the moment (I plan to reduce the width of course)

The red rectangle is curretly where I have "parked" all the power management units : LDO, DC-DC etc..

The square chip in the midle around is a MCU TIVA C in 3.3V, The rectangle big guys is a GSM module in 3.8V, the little tiny chip on the left side of the big guy is a audio codec in 3.3V, on the extreme left the horizontal blue dot are pin for jack 3.5mm that will go to audio codec (I have voluntarily separated the analog part on this left bottom side of the board to isolate it from any potential noise and reduce EMI. The square footprint up in the board (which i plan to move on up the MCU) is a GPS module. On the right part of the board, the DM 9 conector one is for RS232 in 3.3V, the other for CAN 5V. Between those connectors and the MCU there is an EEPROM in 3.3V and an accelerometer. On the other side of the board I have a sim card which I plan to place not very far from the GSM module and I have placed also a TF card in 3.3V on the extreme left corner (you can not see it as it is on the other side).
The connector in blue you see in side the PMU area is a connector for a Lipo battery (back up battery). At the extreme right bottom corner in the main power supply connector (9-36V). I have a protection circuit, then a buck converter to bring this 9-36V to 5v, then a battery charger with a power path who go to 3.3-4.2V, then another buck boost converter who bring back to 5V, then another LDO who go to 3.3V and another LDO who go from 5V to 3.8V.
As I suppose the question coming, why I go from 5V to 3.3-4.2V then again to 5V , then again to 3.3V, here is the answer: As I have a power path for back up battery the charger power path can only be a buck converter (this is how they made it in TI), hence it will never output more than 4.2V, still I need 5V somewhere and the LDO who power the GSM module is already selected by manufacturer to transform 5V to 3.8V (and I prefer avoid changing it as it is already stable in the reference design). I am aware we are dissipating may be a bit but this device is not power sensitive in term of battery life so we don't care too much.

Below a few more pictures of the placement of those elements

9-36v becoming 5v here

5v into power path with battery lipo become SYS voltage betwee 3.3v and 4.2v

boost converter Voltage systeme into 5V again

5v to 3.8V for GMS module

3.8V to 3.3V for audio codec

5v to 3.3v again this is to separate the audio codec from other elements


texts: Need help with use of LM358, microcontroller and +/- power supply

texts:
I have signal in 0-5V range and would like to amplify it to 0-10V. For that I am using LM358, but I have a bit of trouble with that.
I have naively designed the circuit like so:

I tried to supply this amplifier with 9V battery and with +/- 12V source (not stabilised), but none of them worked. Also, I'm not so sure when yo use which ground - where should be the output 'grounded' to? To op amp or the orginal ground? And the resistor on inverting input?

Other question is regarding to powering of the whole circuit from +/- 12V supply. Here is the whole scheme:

I would love to power up the whole thing just from that one source, but there is weird noise at the end of it (without opamp), probably because of missing ground (?). Is there way how to fix that or I must use symmetrical supply with ground?

Thank you very much! I am kind of desperate.


texts:
can anybody help me how to build a SIPO (Serial In Parallel Out) register just from the RS or RS edge triggered flip flop circuit?

I have tried to build this, but I think its not working. I simulating it in a LOGO!Soft Comfort, and I can not use a different program because its a school project


texts: Can someone tell me what types of microcontrollers are used in modern keyboards. I would like to make my own keyboard and I think the best for me is something from AVR like atmega32u4, but I want to know what is used in large scale production.


texts:
I am looking to buy a switch for 85Vdc and 16A.

https://www.alliedelec.com/m/d/dbd1a0ffce5b4bc03b21347df857ba1b.pdf

I was looking at this datasheet and it appears to be ok for 20A @ 125Vdc.
Can someone give me a second opinion?  I ask because usually there is an ac rating that is drastically different than the dc, but here it says they are the same and I want to confirm if this is correct.


texts:
Would wearing white latex gloves(doctor gloves) protects you from getting shocked when repairing electronics?
And is there a reason why you seldom see anyone wearing gloves when dealing with electronics?


texts: Why do variable frequency drives (VFDs) need so much information?

texts:
I'm an electricians apprentice at a mine. I understand the basic operation of variable frequency drives (VFDs), rectification, filtering, and pulse width modulation. But, at the heart, all they're really doing is changing the incoming voltage into a frequency controlled replication, right?
When I'm setting up VFDs in the field though they all need the name plate information such as number of poles, full load amps etc. I can't get a good explanation of why.
Can't it just change whatever demand it gets from the motor? I know frequency is related to the number of poles in alternators but it doesn't make sense me that it would matter to a VFD using IGBTs.
Can you help me understand how the drive uses this information?


texts: Measuring high frequency current with Adrunio

texts:
Is there a way to measure the current of a high frequency signal (100Khz) with an Ardunio? I am thinking that some form of analog circuit could be made whose input takes AC current and whose output is DC current (or voltage), and that this would be readable by any uM's analog to digital inputs.

Edit: The waveform is a sine wave; the output of a chopper stepper driver. The average current is required and I don't expect more than 2 amps of current.


texts: Effect on opamp lead length for non-functional wien bridge oscillator

texts:
I've built two diode stabilised variable frequency wien bridge oscillator circuits according to this schematic:

(source). Both are on the same stripboard and connect to a single LM324.

One of the oscillators works beautifully, the other doesn't. The oscillator which doesn't work connects to the opamp with around 3cm of shielded wire (my original stripboard layout wasn't designed for two oscillators, so this was a hack).

I have checked my breadboard around 20 times and am fairly certain I haven't just made a silly mistake in the non-functioning oscillator.

Is there a possibility that the length of these wires may be preventing the oscillation? I understand that the successful functioning of the wien bridge can be sensitive to things being just so, but I don't know if the inductance in shielded wire this length could be enough to stop it from working.

Unfortunately I don't know enough about electronics yet to properly troubleshoot the circuit apart from simple continuity and resistance tests. FWIW, the dual gang pot for the dud circuit is better matched than the functioning circuit (~1Ω vs 10Ω).

Update

I'm using the same power supply (two 9V batteries) for both oscillators and have   connected the +9V to both circuits, as per the awful diagram below:

(the -9V and ground connections have also been made directly to the batteries in both circuits).

Is this naive? Have I now made the two oscillator circuits dependent on each other as the two 10k resistors are now connected?


texts:
I have a transfer function for G(s) and need to rearrange for G1(s).

After a LOT of playing around I have worked out that the correct answer is as shown in the image.

My problem is that I need to know the steps required to rearrange from the first form to the second. I can get most of the way but think I am missing a rule of rearraging equasions allowing me to complete this task. I have only managed to complete it through trial and error. I have even tried rearranging backwards, to no avail!

Is someone able to provide a step through of how to do this?
I will be eternally grateful! :)


texts: How long can PIC18 keep RAM after being powered off?

texts:
I've noticed unusual behavior from PIC18F4680.

I have declared following matrix: char [7][5] and I have function which loads the data into the matrix. Data is then read from the matrix and shown on two 5x7 displays.

During debugging, I've commented out the only call to the function which loads data into the matrix and after I reprogrammed the PIC, I was surprised to see that the shown image remained.

Just to make sure that there isn't some partially charger capacitor doing something strange, I shorted the power input and left it like that for maybe 5 minutes. After powering the board again, I've noticed that only 4 dots on the displays had wrong value.

So my question is: how long does it usually take for the RAM in PIC18 series to reset?


texts: CE certification: battery-powered LED lights

texts:
There are lots of products on the market that are LED lights which don't all seem to carry CE markings. I'm looking at designing little ornamental things with embedded LED lighting, and trying to work out if this will require EMC testing or whether I can just happily self-certify (or should leave off the CE mark entirely!).

Does anyone have a definitive answer? My reading of http://ec.europa.eu/enterprise/sectors/electrical/files/emc_guide__updated_20100208_v3_en.pdf is that LED+battery+current limiting resistor is "inherently benign", under "Pocket lamp
s without active electronic circuits", but if I were to include a switchmode power supply or Joule Thief circuit that would trigger the requirement to EMC test it.


texts:
I have a Arduino Pin connected to a Logic Level MosFet (IRF3708) to switch a 12V led strip which should consume 1A. The Ugs(th) voltage of the MosFet is 2V. That I don't accidentally kill one of my MosFets I put a voltage divider at the output of the arduino. It should give me a voltage of 2.04V but I just get 1.6V. The arduino pin and the MosFet gate should be high impedance and I don't understand why?

Schematic

simulate this circuit – Schematic created using CircuitLab


texts: Building a board game, not sure what to use for the "computer"

texts:
My brothers and I are building an interactive board game that will require a central device to keep track of the number of players,  player resources, turns, location, etc. I have an idea of how I'm going to build this program wise (some form of bare bones linux).

However hardware wise I don't know where to start. It would preferably need to be smaller and on the inexpensive side because this is a prototype and we hope to produce the game, along with that, battery powered is a must. It doesn't need to be some god machine, just something that can keep track of letters and numbers and spit them out onto a screen.

I think I will be fine on sourcing the buttons and screens, but if you have suggestion for those I'm open to it as well.

Thanks in advance for the help!


texts:
I'm trying to understand this schematic of this differential probe:

I marked some blocks. I have some questions about the block I marked "Long-tailed pair" (LTP). I have no experience with LTPs so excuse ma noob questions.

I have simulated this LTP (just the LTP without all the other blocks in the schematic) in LTspice and it's bandwidth is around 26MHz. How to increase it's bandwidth (beyond 100MHz)? What are the main limitations here in this LTP?
What is the purpose of BJTs (U2B, U2C) there? The only thing I could think about it is that it offloads the JFETs from the current. Is that right? Or is there another reason for that? When I remove BJTs (U2B, U2C, and their resistors R8, R9) then bandwidth increases to 52MHz. So I'm curious what is the purpose of them, because they alone halves the bandwidth.
I understand that R12 and R13 are emitter degeneration resistors (or better say "source degeneration"?). Anyway, how to determine overall gain of such long-tailed pair?
What is the output resistance/impedance of this LTP? Is it R14, R16 or is it R12, R13?

Simulation:
These are the parts I have used in simulation (LTspice does not have the exact transistors used in that schematic):
JFET SST441
BJT 2N2222

Now as I see these charts, it is weird. I considered it is a 26MHz bandwidth, but it looks like a high-pass filter. Because lower frequencies are at -13dB, and higher frequencies are at 0dB.

simulate this circuit – Schematic created using CircuitLab


texts: Why aren't homopolar generators more commonly used?

texts: In particular with the advent of HVDC(high voltage direct current). Using mercury(metal), the resistive losses can be greatly reduced. There has even been some experimental research into neon plasma based electrical contacts. They have been used to supply the large currents required by particle accelerators. What is interesting is that AFAIK it is the only type of electric generator that can produce pure, ripple-free DC current(and very large currents as well). One could build a high current output rotary converter using an AC motor coupled to a homopolar generator.


texts:
How can I determine the switching speed of a MOSFET, with given Qg (gate charge), Vgs (G-S junction voltage) and gate resistor ?
How should I determine the required value of the gate resistor?


texts: How can a Zigbee coordinator send commands in large networks (greater than 240 devices) to nodes?

texts:
If the maximum amount of endpoints on any ZigBee device is 240, how could it send and recieve commands in large networks of more than 240 devices?

I know that if a device only wants to send periodic data to the coordinator it does not neccessarily need to bind to it. But if the coordinator was to lets say, switch 300 lights on and off from a connected PC. How could I do this within a ZigBee Pro network if I did not know the endpoint ID at compile time.

I have read that I can poll a device for information for what clusters it has available and perhaps it could provide me with the endpoints associated with these clusters. If this were the case, does that mean I would have to go through this query, processing, transmission loop everytime?


texts: Doubt regarding dual channel MOSFET datasheet

texts:
I came across a dual channel MOSFET link for dual channel MOSFET

But I am confused about the drain current of 0.63A. Do they mean drain current of each channel is 0.63A or for both channels combined?


texts: i have a transformer with 0V and 220V(neutral to line voltage) in the primary side. I want to know if it is possible to use a 220V single phase(line to line voltage) as input in the primary side? Thanks!


texts: Is there a way for a laser to work across a range of colors?

texts:
For lasers used for free space / mirror steered / diffuse beam communications or LIDAR scanning, would there be some way for a single laser to be able to selectively transmit across a range of colors, to a receiver that can similarly distinguish between colors?

This would be similar in operating principle to a radio transmitter that can adjust its transmitting frequency up or down across the radio spectrum, to a radio receiver that can distinguish what frequency it is receiving.


texts: Unable to use IR receiver and motor shield together

texts:
#include <IRremote.h>
#include <AFMotor.h>
AF_DCMotor motor(1);

int RECV_PIN = 14;//The definition of the infrared receiver pin 11
IRrecv irrecv(RECV_PIN);
decode_results results;

void setup()
{
  Serial.begin(9600); //Open serial
  irrecv.enableIRIn(); // Initialization infrared receiver
  motor.setSpeed(255);
  motor.run(RELEASE);
  Serial.println("start");
  motor.run(FORWARD);
  delay(1000);
}

void loop()
{
  if (irrecv.decode(&results)) {
    if(results.value==0x3D9AE3F7)
    {

      motor.run(FORWARD);
      delay(2000);
    }
    else if(results.value==0x1BC0157B)
    {
      motor.run(RELEASE);
      motor.run(BACKWARD);
    }
    Serial.println(results.value, HEX);//Wrap output in hex receive code
    Serial.println();//For ease of viewing the output to add a blank line
    irrecv.resume(); //Receiving the next value
  }
}

The motor shield is not working when I use an IR receiver.
I tried connecting the IR receiver to different analog pins but it didn't work. I guess it's due to some error in my code but I am unable to figure it out.


texts: transistor or an SSR Relay as a Switch ? PCB

texts:
i want to create a switch that will turn on/off the power to my OBD Port on my car when i turn engine on/off. reason being i have an OBD wifi dondle plugged in all the time. problem is the OBD Port has a constant 12v power so will always stay on.so the wifi dongle will drain he battery plus its not a good idea to leave it on as someone else could connect to it.

i am going to de solder the 12v pin inside the wifi dongle and put a switch in between . i was thinking on using a transistor. so when i turn engine on 12v from the cigarette lighter goes to the base of the transistor. that in turn will complete the circuit of the 12v into the wifi dongle.

i have bread boarded the following. 12v from car cigarette lighter goes to a 5v regulator. then 5v to 2.2k resistor to base pin of a MJD122G transistor collector pin is connected to OBD PORTS 12V then Emitter pin connects to the 12v  inside the wifi dongle. This all works fine and turns the wifi on/off as expected. problem is if i run more than 500MA the transistor gets very hot. maybe all it needs is a little heat sink ?

i then thought why not use a small solid state relay like the  12v G3MB-202P DC-AC i could simply just connect 12v from cigarette lighter to the input of the relay. would this solid state relay get hot too ? im not sure what route to take with this.

iv started designing PCB for the transistor

so which one would be best to use ssr or transistor ? my transistor design is smaller which is a plus and i do light building my own things


texts: Is it possible to integrate a signal in LTSpice and plot the result?


texts:
I found BCR421 driver and want to ask how to properly drive TSSF4500 LED. All the parameters seem to make sense if look separately, but where do I start to determine the necessary parameters?

It should be a continuous mode with voltage supply of say 3.3V. I would like to be able to adjust the current through the LED from 10mA to 100mA.

For that, I am planning to use the trimmer resistor in series with a 10 Ohm resistor in place of the Rext, where the 10 Ohm on its own will drive the Iout to about 90mA, and additional resistance from the trimmer will allow to drop the current to 10mA, according to the plot below:

Should I care about the Vout value? It seems to me like a chicken and an egg problem. Vout depends on the voltage drop across the LED and Rext, and determines the current Iout, according to the plot. It the same time, the current through the LED  depends on the voltage drop across the LED, which also dictates the Vout that determines the Iout. Well, I can not seem to get out of this loop. So, what determines all the other?
How do I determine the current through the Rext, or the Vdrop? Is it correct to assume that for low Rext values the current through it is ~Iout?
What is the advantage of this circuit as opposed to simple resistor-diode in series (except the EN pin that allows fast switching)?


texts:
Is there any standard color code available for IF transformers?

Generally in most of the Japanese radio receivers I see red color slug for MW oscillator, white and yellow slugs in AM IF stage, orange color slug for FM oscillator, blue, purple and pink colored slugs in FM IF stage, etc.


texts: Would this be considered an internal node?

texts: n1 was the only internal node the textbook talked about, but would the small upside down L shaped node connecting B's node to E1 be considered an internal node? As well as the other upside down L shaped node directly below n1?


texts: How to rotate several parts with respect to origin without changing its (x,y) coordinates in KiCAD?

texts:
Say I have a part located at coordinates (50,50) and I want to rotate it 10 degrees w.r.t. origin. To do so, I will select the part and press "Move Exactly" and key in these values:

Now the problem is I have 50 seperate parts that I need to rotate in this manner. Viewing each part's coordinates individually and rotating them manually is very repetitive and I'm sure I'm missing some shortcut. Is there a better way to do this?

EDIT:

Before photo:

What I'm intending to do link:

Now I am unable to simply rotate it then position it afterwards, as I need the pcb to match with my keyboard switch plate, which is generated from


texts: Is there a scale drawing of SMD package sizes as a design aid? This could be useful in schematic/layout stages of a project in when deciding to trade off size vs. cost.


texts:
I am trying to understand how assignments with 'after foo' work, so I read about the delay model and simulated the following code:

library IEEE;
use ieee.std_logic_1164.all;

entity test is
    port (
          goes_in, goes_out : out std_logic := 'U'
         );
end entity;

architecture a of test is
signal temp  : std_logic := 'U';
signal input : std_logic := 'Z';

begin
    goes_in <= input;
process (input)
    begin
    temp <= input;
    goes_out <= temp after 10ns; -- (*)
    end process;

--Removing the line with the (*) and uncommenting the following snippet solves the problem.
--process (temp)
--    begin
--    goes_out <= temp after 10ns;
--    end process;
process
    begin
    input <= '0';
    wait for 15 ns;
    input <= '1';
    wait;
    end process;
end a;

In Xilinx's Vivaldo, I get the following output:

time(ns) :            10      15      20      25
                              _________   ________________________  ...
goes_in  : _______'0'________/         '1'

goes_out : ----'U'-----|---------'Z'----------\_____'0'___________  ...

When what I expected was simply a 10ns delay. Can someone explain what is going on here?

EDIT: To be clear, my beef here is that, if the behaviour I'm describing is indeed default, it sounds like an awful leak of abstraction: when I write

goes_out <= temp after 10ns;

the behavior I expect would be one that simulates a latch being driven (temp is the input, goes_out is the output), and so temp would have to keep its new value for 10ns in order to properly drive the latch (hence the "inertial delay" model).

Now, if this were indeed the case, the proper behaviour for my circuit would be to do nothing, since I attempt to write a 'Z' to goes_out and immediately after that, that 'Z' is overwritten by a '1' - therefore, the value of temp driving the latch is not kept, and it fails to drive goes_out. (obviously you can't drive latches with 'Z', thought I could use '0' and '1' and my point would stand)

So my question is: is there a good reason for this odd behaviour? To me, it seems trivial to "make things right": the algorithm that simulates the inertial delay could check for changes in the value of temp in the delta cycle it is being assigned to goes_out, and cancel the assignment if something is happening - instead of only cancelling the assignment if the NEW value of temp does not change.


texts: Function not working probably like expected, using TM4C123 MCU

texts:
I am trying to generate a Clock synchronized with data, where the frequency of the clock should be twice the frequency of the data. I wrote a code for this purpose and it works fine for 32bits of data, anything more than 32 it will generate a bunch of 1's. Here is what I got for 64bit data=(0XAAAAAAAAAAAAAAAA):

Here is the code I wrote:

  void DATA(unsigned long  int number, int iteration){   //number: data to be send serially
                                                       // iteration: number of bits to send
  unsigned long  int x=0;         //An integer to hold each bit from the data
  char even = (char)0x1;
  TIMER1->ICR |= (1<<0);
  for(int y=0; y<=iteration;) {
     while((TIMER1->RIS & 0x00000001) != 1){}   //wait until Timer1 times out
      TIMER1->ICR |= (1<<0);     //Reset Timer1 flag
      odd ^= (char)0x1;
      GPIOC->DATA ^= (1<<7);     //Toggle the clock at PC7
      if (odd) continue;        // data change every even cycle
      x = number & (0x01UL << y);      //Get each bit individually
      if(x==(0x01UL<<y))           //If bit is 1
          GPIOC->DATA |= (1<<6); //Make C6 High
      else if(x==0X0)            //If bit is 0
          GPIOC->DATA &= ~(1<<6);//Make C6 Low
      y++;
  }
  }

  int main(){
     DATA(0XAAAAAAAAAAAAAAAA,64);//
   }

Note: I have tried to make the number in my function to be long long int, and that didn't solve the problem too.
Is there any explanation for getting those 1's after the first 32 bits ?


texts: Looking for suggestion on microcontroller

texts:
I took a course on using microcontroller of Intel 8051 long times ago. Recently, I am going to develop a module to control precise-timed TTL output and my instructor suggests to use microcontroller (MCU) instead of something like 555 timer. I am planning to get one for trial but I really don't have much experience on that.

My project is to create a time sequence with interval about 0.01 to 0.5 microsecond with function generator, which required the sampling frequency of the fun generator to be about 5 to 100MHz. But using function generator is not portable and I cannot program the function besides creating the timed sequence. I cannot generating that sequence with PC because the minimum time interval for interrupt is 1ms and it is too long for generating such short time interval pulses. Also, more importantly, even I generating 1ms-interval pulses with PC, since I don't have the real-time system, it doesn't generate time pulses at the expected interval precisely. Do you think MCU's interrupt is in real-time, i.e. how precise if I want to generate pulses like in 0.1ms for example?

I am also thinking an extreme case with super short pulse (1ns), does any sort of MCU support that short of interval?

My last question is about the code writer. I remember it needs a flash burner and compiler to feed the code into the chip 8051 while I was taking my course. But they got a development board in lab so everything go in one step. I wonder how does it works in practical development. Do I have to buy something like flash writer to write the code to the chip? The layout of the chips are different from manufacturers to manufacturers, so does it mean I have to buy different flash writer for different model? My budget for chip (and writer if needed) is about 20 bucks to 40 bucks. Any model to suggest is highly welcomed.


texts: Measuring Power per Hertz of a RF signal

texts: I am testing my communication application to see it's performance over different frequencies. So I need to measure power at different frequencies of operation. I have been told that my limitation for power to be transmitted is -50dBm/Hz. So I need to see to it that I don't exceed this rating. So i sent a signal at 500Khz bandwidth and checked the output power from the transmitter. I got the value to be around -60dBm. I then changed the bandwidth to 1Mhz to see that maybe the power value will double. But then the only change in power was from -60dBm to -57dBm. I then changed bandwidth to different values to see a correlation. I didn't find any. So how do we go about measuring power per Hz. Seeing the spectrum analyser values if I try to divide power value on spectrum analyser by bandwidth present i think it will be Inaccurate. I would like to know what I am doing wrong and how I can meet the rate of -50dBm/Hz. Any other approach that would help?


texts: The GCC Ride7 STM32 startup script does not jump into SystemInit function

texts:
We are a robotics association from ENSEIRB-MATMECA (Bordeaux, France). We are developping some boards and a template project for STM32 devices.

One of our boards embed a STM32F103C4 microcontroller. We use the startup script from gcc ride7  startup_stm32f10x_ld.s.This startup script work until the line "bl SystemInit" is reached. Then, the system doesn't jump to SystemInit() function as he is expected to do and the bootloader is listening again (reset).

Here is the link instruction:

/home/kevin/ausbee-test/Software/Toolchain/arm-none-eabi/bin/arm-none-eabi-gcc -o /home/kevin/ausbee-test/Software/output/project.elf -mthumb -mcpu=cortex-m3 -Wall -Wextra -mcpu=cortex-m3 -mfix-cortex-m3-ldrd -mthumb-interwork -DSTM32F10X_LD -Wl,--gc-sections -Wl,--Map=test.map  -T/home/kevin/ausbee-test/Software/System-CM3/link.ld /home/kevin/ausbee-test/Software/System-CM3/CMSIS/CM3/DeviceSupport/ST/STM32F10x/startup/gcc_ride7/startup_stm32f10x_ld.o /home/kevin/ausbee-test/Software/System-CM3/CMSIS/CM3/CoreSupport/core_cm3.o /home/kevin/ausbee-test/Software/System-CM3/CMSIS/CM3/DeviceSupport/ST/STM32F10x/system_stm32f10x.o /home/kevin/ausbee-test/Software/Project/src/main.o

The test.map file contain the SystemInit symbol.

We use GCC ARM embedded toolchain (https://launchpad.net/gcc-arm-embedded). Our template project work with other devices such as STM32f105.

Do you have any idea where this bug come from?

Thanking you in advance.


texts: What is the tap on a center tap transformer

texts: How exactly is a tap made. I just got curious I've seen the circuit diagram and they often say things along the lines of "a wire is attached in the exact middle of the secondary winding". But how? Might be a dumb question but I can't really find any pictures of how it's done, is it just soldered halfway? Is it looped on there in such a way to only influence one spot?


texts: How to solder Christmas lights insulated wire?

texts:
I want to fix Christmas lights like these, whose wires got cut near the batteries. The LEDs near the batteries still work.

I tried touching the wires from the two parts and I was surprised that the they seem to have metallic insulation. I sliced one LED at the end and confirmed that touching the inner rods does turn this LED on. Here is a picture of the two pairs of wires I want to solder:

The outside of the wires has a silver color, the inner rod looks like copper.

What is the name of this type of insulated wire, and how to solder it back together?


texts:
How do I load code onto a ItsyBitsy 32u4 without using the graphcial Arduino IDE?

I've looked for "ItsyBitsy 32u4 programmer" and ItsyBitsy 32u4 bootloader".


texts:
I am new to electronics and just tinkering with it first time. I have laptop charger with 19V/3.42A and connected to 12v regulator and 3.3v regulator to get two voltages - 12v and 3.3v. I am going to use 3.3v device(which needs upto 1A) to control 12v LED strip. But,regulator drives hot. I don't understand if it's okay or current is too high for it. Here is my circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Generate energy from waves that move my ship?

texts:
I'm currently building a small solar powered robot boat. I expect it to work fine (because why not.. :-) ), but I'm already looking for other ways than only solar panels to generate electrical power. Since the sea has waves that will move my boat a lot I was thinking of the possibility to harness this power to generate some more energy. So isn't it possible to create a bigger and heavier version of the things they have in certain watches:

What if I made one which weights a kilo or so. I understand it won't give an enormous amount of energy, but it will be moved 24/7 and every extra watt is welcome to power the motors.

Are there any reasons why this currently isn't used (as far as I know)?


texts: What are the things I need to know when operating an oscilloscope?

texts:
I keep hitting a wall on my projects where I can't really tell what's going on and decided I really need an oscilloscope to proceed intelligently.

I've got a Rigol DS1052E in the mail after a few recommendations.  I know the kinds of things I need to measure, but I want to make sure I don't blow it up the first day.

What kinds of tips do you guys have for effectively using a scope and avoiding damage to it while getting useful information out of things?


texts: Max Distance for 5V serial communications

texts: I have an application where two different microcontrollers need to communicate. I was thinking that for simplicity, just use 5V instead of converting to RS232 levels. What in good practice would the max distance be for single ended communications? (0-5V). At what distance / conditions should I consider a differential driver / receiver?


texts: Building a formula to pass n bits though the minimum number of circuts

texts:
I have a circuit X which has 4 inputs A0,B0,A1,B1 and 2 outputs A2,B2. For n of A,B bits, I need them to pass through X.  I'm trying to build an equation on how many circuits X I need for n bits. For example, for n=8 we need 7 circuits:

I found out that for 2<=n<=7 we need n-1 X cuirits, but I know that for n=32 we need to get 30. What is the right formula?


texts: What is the relevance of a !Q in the D Flip-Flop when using for a memory module?

texts: If the purpose of this circuit is to store the value of D in Q, why should I need a !Q? Why don't use a circuit like this instead?:


texts: 9-axis IMU for weighing on a boat with varying sea conditions

texts:
I am brainstorming on how to do relatively accurate weighing scale for fish on a boat under different seastate conditions.
I know other companies use a second load cell together with calibration data and some heavy math to do the same with sucess. The issue with this is that it takes some time to compute the sample data to estimate the G-force used to compute the weight.
To me the obvious choice would be to get a 9-axis IMU together with a loadcell to counter the G-forces to get accurate measurements. If the IMU delivers an accurate G-force I would not have to consider the above solution.

What accuracy can I expect from a high grade 9 axis IMU?
Is a good IMU the way to go about solving this problem?

My budget is around 2000USD per item.


texts:
I want to write a 32 bit reg to 22 bit reg while conserving the number and its sign.

reg [31:0] test_dat0; //test_dat0 <= -4 (binaire)
reg [22:0] test_dat1;
test_dat1 <= test_dat0 ; ??? //what is the value of test_dat1 here

is it right ?
thank you


texts:
We are designing a board (RF) which also has an RF amplifier that emmits a 5W signal.
Unfortunately,as its a space PCB we cannot have a ground or copper por that can dissipate heat. More over the absence of air in space will prevent dissipation of heat into the ambient area.

If there is kind of vaccum without any air around, how will heat be dissipated ? What are the implications ,impact of a design such as this ?
How can I reduce the heat generated in this way ?

Would the apt way be revising the BOM to select components of a better thermal resistance ?
Kindly advice please ?


texts:
I am using the TS391IYLT in a design, but need to swap it with an alternate that has rail-to-rail capabilities. The issue I'm running into is that the pinout is somewhat irregular; see below. Most comparators I've found have a similar pinout, but IN- and IN+ are reversed.

Is there any way to search for parts by pinout? Such that the results only show chips with the same pinout?


texts:
I'm trying to interface an mma7361L accelerometer (on breakout board with caps) to the analog inputs of an 18f46k20.  According to the PIC datasheet, the Vmax input voltage is Vdd + 0.3 which means I have to get the signal between 0V - 3.6V.

I only need to measure the Z-axis and from what I can tell it produces 850mV/g but I don't know if that's centered at an already offset voltage, or at zero. Does anyone here have experience with this chip? If so, what kind of signal conditioning do you recommend if any?

Many thanks.


texts: delete drill layer in eagle without redoing board

texts:
When I go to make my own circuit boards with eagle, after saving, I run the drill-aid.ulp script so eagle can convert all over-sized drill holes to small size. It helps me with drilling. I then saved my board again. I did this a few days ago.

Now this time, I load the same board and I want to undo that operation very quickly. I tried selecting the layers box and I scroll all the way down to:

116 CenterDrill

When I select Del, I get the message:

Layer '116 CenterDrill' is not empty.

Because I have at least a few hundred of these to remove, doing it manually will be a pain in the butt.

Is there some easy way for me to do this? even if it means me inventing some sort of script? I want the board to once again be at the state just before drill-aid.ulp was executed.


texts: What is the cost of converting 12V (lead acid battery) to 220V and back again to power 12V appliances?

texts:
I have a small house measuring ~ 8m x 4.5m. It is in Indonesia and power outages are expected daily. Probably the daily power outage is on average less than half-an-hour, but sometimes the outage can be the whole day (9am till 5pm say).

I have various appliances that run on 12V:

a wifi router/modem (1.5A)
a burglar alarm system (1A)

I also want to install a CCTV system. There are two options for this, either a 48V NVR with POE sending out 48V to cameras, or a 12V NVR (I believe 15W, plus the hard drive) and the cameras (around 6W each) being individually supplied with 12V.

Anyway, I want to have these things as 'always-on'.

So I am looking at:

deep cycle conventional 12V lead acid battery
12V charger
maybe 220V inverter

Note that I am not backing up the whole house, and I am remodelling the house including replacing all wiring, so whether I have an 'always-on' circuit on 12V or 220V is not particularly an issue.

Anyway what I can see is that if I power 12V directly from 12V than obviously that's more efficient than converting 12V to 220V then back to 12V, but I am not sure how much of an issue this is in practice as the battery obviously needs to be somewhat oversized in any case.

On the other hand presumably I will have transmission losses with such a low voltage, and I will need to fit special 12V sockets and provide a whole-house 220V -> 12V transformer for when the system is running on mains, so the infrastructure costs aren't obviously lower than keeping everything on 220V.

The main advantage seems to be a slightly smaller battery. How much smaller?


texts: (ADS5295) 12bit ADC with 14x serialization

texts:
I am using 12bit ADC, Texas Instruments ADS5295.

In manual of ADS5295, it says ADS5295 supports 14x and 16x serialization factor.

The resolution of ADS5295 is 12bit.

If I set 14x serialization factor, is output data  composed of 12 valid bit and 2 dummy bit ?

At page 79, it says 'When digital signal processing functions are used, the 14x and 16x serialization modes can also be used.'

What kind of digital filter do I need to using 14x serialization with ADS5295?
Which register do I have to set?


texts: When should I use SR, D, JK, or T Flip flops?

texts: In class I've learned about SR, D, JK, and T flip flops. From what I understand, you can construct any design by using any of them. So my question is when making a design, how does one choose which to use? Which one is used more in commercial circuits and why?


texts:
Another question along with this one.

The guide I've been following says that after you reset the 8u2 by connecting the two pins shown below, the board should be undetectable by the Arduino IDE. I have successfully done so, but the board is still using COM22 as an Arduino Mega in the device manager. This other guide I found shows the board becoming a LibUSB-Win32 device. Anyone know what's going on?


texts: Can Arduino power and hookup to logic chips?

texts: I am making a device that has two external interactions i.e. a button and a infrared sensor. My only problem is that I am using a logic chip for this because it would save me time coding on the Arduino, but now I don't know if the Arduino can cooperate or power the OR CMOS. I am a beginner in the logic and 555 timers field so every time I see them I try to ignore it. I have it now. Tried to draw a schematic and it just clicked. Thank you for trying to help.


texts: How can I lower the speed of a 220-240V (100mA, 16W) inline ventilator fan?

texts:
I have installed an inline fan (220-240V, 01.A, 16W) to draw air out of my kitchen to outside. It works well, but a little too well, and is noisy. So, I would like to reduce the speed somehow, say to half of its current speed.
I am trying to teach myself electronic engineering so fancied this as a project to learn about transistors/MOSFETs.
I have Arduinos but I don't think I have a MOSFET that can handle 220-240V; I mean the BVdss on it is 60V max. But am I climbing up the right tree here? Is there another approach I'm not yet aware of?
Any help greatly appreciated.


texts: What is this foreign material on my outsourced PCB?

texts:
I had this board populated by an EMS house. There is foreign material around some of the pins. They don't know what it might be. Our collective best guess is that it is somehow shavings from the casing of the resistor network. The material does not appear to be conductive. It does not appear on every instance of this type of component on the board, but does appear on many boards in the same location.

Has anyone seen this before? Any ideas what it is, or how I can find out?


texts: How can I run an STM32L with an unpowered ST-Link connected?

texts:
I have an STM32L476RG on a custom board that I have to leave connected to an external ST-Link/V2 so that I can reprogram it without accessing the hardware. I'm also forced to do this via a USB hub due to my limited number of available outputs.

Right now the MCU runs when the hub (and in turn the ST-Link) is powered via a connection to a computer. I'm searching for a way to make it run when the hub isn't powered, however.

I've found some information here regarding the NRST pin, however I only have one ST-Link at the moment and I'd like to avoid messing with it until I've exhausted other options. I should add that its in SWD mode and that I'm also using a 10-to-20 pos JTAG adapter.

Finally, my firmware is largely based on FreeRTOS. A software solution would be ideal if someone can suggest how to do that.


texts: How easy is it to develop hardware to run Microsoft Robotics?

texts:
What do I need to develop hardware that can run embedded software developed with the Microsoft Robotics studio? I thought only certain high-end off-the-shelf robots that support embedded Linux were capable of running such software.

Do you have any experience with MS Robotics? and is it possible for me to develop my own custom-built hardware in-house so I don't have to buy some expensive robot simply to play with the MS Robotics studio and the Visual Programming Language (VPL) that is included within the package?


texts: Is i2c the right protocol for this sensor?

texts:
I have a project I'm working on that involves an nrf51822 communicating with the optical sensor from a mouse.  The pinout of the opical sensor seems similar to the ADNS2620, but the exact datasheet is not available.  The datasheet for the ADNS2620 seems to basically say (but not explicitly say) that it uses I2C - unless I'm not understanding it correctly.

I've established an i2c scanner on my nrf51822, and it is (as far as I can tell) properly scanning each address (1-127) to find a device, but is receiving to response.  I'm left to question if the optical sensor even communicates over i2c - and if not, where do I go from here?

Pointers appreciated.  Thanks.


texts:
I am using the PIC18F13K22 and Microchip's C18 compiler in MPLABX. The PIC kept resetting, when it was about to jump into the interrupt service routine (ISR). I was able to trace the problem down to the declaration of an array:

UINT16 rom periods[] = {64000,59412,55438,51962, ...} // 1024 Values

If I shrink the size of the array down to a few items, the PIC is running without resetting continuously.

Now I am wondering why the large array causes a reset. And even more interesting for me: can I declare somehow a dataset containing these 1024 values?

The requested Section Info:

              Section       Type    Address   Location Size(Bytes)
            ---------  ---------  ---------  ---------  ---------
           _entry_scn       code   0x000000    program   0x000006
               .cinit    romdata   0x000006    program   0x000002
      .romdata_Main.o    romdata   0x000008    program   0x000800
         .code_Main.o       code   0x000808    program   0x000124
           _cinit_scn       code   0x00092c    program   0x00009e
        .code_Debug.o       code   0x0009ca    program   0x000080
       .code_Signal.o       code   0x000a4a    program   0x000040
                 PROG       code   0x000a8a    program   0x00003c
       .code_t0open.o       code   0x000ac6    program   0x000038
          .code_ADC.o       code   0x000afe    program   0x000032
         .stringtable    romdata   0x000b30    program   0x000026
                .code       code   0x000b56    program   0x000020
         _startup_scn       code   0x000b76    program   0x00001c
       .code___init.o       code   0x000b92    program   0x000002
    .romdata_t0open.o    romdata   0x000b94    program   0x000000
    .idata___init.o_i    romdata   0x000b94    program   0x000000
    .idata_t0open.o_i    romdata   0x000b94    program   0x000000
     .romdata_Debug.o    romdata   0x000b94    program   0x000000
     .idata_Debug.o_i    romdata   0x000b94    program   0x000000
    .romdata___init.o    romdata   0x000b94    program   0x000000
    .romdata_Signal.o    romdata   0x000b94    program   0x000000
    .idata_Signal.o_i    romdata   0x000b94    program   0x000000
      .idata_Main.o_i    romdata   0x000b94    program   0x000000
       .romdata_ADC.o    romdata   0x000b94    program   0x000000
       .idata_ADC.o_i    romdata   0x000b94    program   0x000000
        .code_c018i.o       code   0x000b94    program   0x000000
     .romdata_c018i.o    romdata   0x000b94    program   0x000000
     .idata_c018i.o_i    romdata   0x000b94    program   0x000000
.config_300001_Main.o    romdata   0x300001    program   0x000001
.config_300002_Main.o    romdata   0x300002    program   0x000001
.config_300003_Main.o    romdata   0x300003    program   0x000001
.config_300005_Main.o    romdata   0x300005    program   0x000001
.config_300006_Main.o    romdata   0x300006    program   0x000001
            MATH_DATA      udata   0x000000       data   0x000014
             .tmpdata      udata   0x000014       data   0x000000
               .stack      udata   0x000060       data   0x000050
       .udata_c018i.o      udata   0x0000b0       data   0x00000a
      .udata_Signal.o      udata   0x0000ba       data   0x000002
       .idata_c018i.o      idata   0x0000bc       data   0x000000
         .udata_ADC.o      udata   0x0000bc       data   0x000000
         .idata_ADC.o      idata   0x0000bc       data   0x000000
        .udata_Main.o      udata   0x0000bc       data   0x000000
        .idata_Main.o      idata   0x0000bc       data   0x000000
      .idata_Signal.o      idata   0x0000bc       data   0x000000
       .udata_Debug.o      udata   0x0000bc       data   0x000000
       .idata_Debug.o      idata   0x0000bc       data   0x000000
      .udata_t0open.o      udata   0x0000bc       data   0x000000
      .idata_t0open.o      idata   0x0000bc       data   0x000000
      .udata___init.o      udata   0x0000bc       data   0x000000
      .idata___init.o      idata   0x0000bc       data   0x000000
        SFR_UNBANKED0      udata   0x000f68       data   0x000098


texts: When is it appropriate to use a dedicated charging ic and when is it appropriate to use a microcontroller?

texts:
To give a little more context, I am designing a device that requires a battery to be charged. What I gather from most commercial designs and reference designs, is that they often use a dedicated charging chip. Since most of my design directions(philosophy) is copying or implementing what others have, I am constantly concerned that my designs are using far too many parts and/or making the design more complex than necessary.
Additionally, it seems that it would be smarter to design a circuit that uses microcontrollers instead of special ics. In the event that the microcontroller supply or supplier disappears, it would be pretty straightforward to spin up a new revision that uses a new micro. The same can not be said of using a dedicated chip unless it really has barebones functionality.
So in short, what is the logic when deciding to use a dedicated charging chip? Obviously the behavior is well defined and it saves many hours of engineering, but for mass produced devices, it seems as if that would not be an issue.


texts: Why is this 10pF capacitor reading 79pF?

texts:
This is my implementation of this circuit, for connecting a Teensy 3.0 to an MSGEQ7. It worked fine when I set it up on a breadboard, but now I've soldered it onto veroboard it doesn't.

Checking through with my multimeter, I find the capacitance between pin 8 (bottom left as pictured) and the Teensy's AGND pin (connected to the black wire in the middle) to be 79pF, rather that the 20pF* it was when I measured the component before soldering.

Is there anything wrong with soldering one leg of the 100nF from pin 6 to the leg of the 10pF? They're both meant to be connected to ground according to the schematic.

Looking closer at the capacitor itself, it's marked "10", which should mean it's 10pF in the first place? Might I have damaged the capacitor while soldering?


texts: Does Attiny13 pull a lot more current in sleep mode than Attiny85 or did I do something wrong?

texts:
First off here is the code I have tested on both Attiny13A and Attiny85V:

#include <avr/sleep.h>

void doSleep(){

    GIMSK |= (1<<PCIE);                     // Enable Pin Change Interrupts
    PCMSK |= (1<<PCINT3);                   // Use PB3 as interrupt pin
    ADCSRA &= ~(1<<ADEN);                   // ADC off

    WDTCR |= (1<<WDP3 )|(0<<WDP2 )|(0<<WDP1)|(1<<WDP0); // 8s
    WDTCR |= (1<<WDTIE);
    sei();
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);    // replaces above statement
    sleep_mode();

}
ISR(WDT_vect) { }

void setup(){

    pinMode(PB0, OUTPUT);
    pinMode(PB1, OUTPUT);
    pinMode(PB2, OUTPUT);
    pinMode(PB3, OUTPUT);
    pinMode(PB4, OUTPUT);
    // Flash twice on boot
    digitalWrite(PB4, HIGH);
    delay(100);
    digitalWrite(PB4, LOW);
    delay(100);
    digitalWrite(PB4, HIGH);
    delay(100);
    digitalWrite(PB4, LOW);
    delay(100);
}//main

void loop(){
    // one long flash after waking up
    digitalWrite(PB4, HIGH);
    delay(2000);
    digitalWrite(PB4, LOW);
    doSleep();   // go to sleep and wait for interrupt...
}

For wiring:

3v VCC from battery.
Ground
LED connected on PB4 through a resistor to ground. But I'm turning it off before sleep mode, so that shouldn't affect it.

This code on an Attiny85V consumes 0.1uA according to my multimeter. The same code on Attiny13A is pulling 100uA.

Am I missing something in the code? Is the t13A really 1/1000th as power efficient in sleep mode as the 85 alternative? Or am I the victim of counterfeit T13As?

Edit: Shortened code a bit


texts: Reason of using a resistor parallel with NTC at mains input

texts: I have a SMPS circuit. There is a serie connected NTC at Neutral input. I know NTC is used for inrush current limiting purposes. But there is a 20ohm 2W resistor which is parallel this NTC and I don't know what is the aim for it?


texts: Equivalent circuit of a circuit with diode and voltage sources

texts:
The goal is to find the Q point of the circuit but the author simplifies the circuit first by finding its equivalent. I need help in understanding how the author went from the original to the equivalent circuit.

https://imgur.com/a/UI9b48w
https://imgur.com/gallery/vJeE3P8

I can see R3 and R4 being in parallel with equivalent resistance  = 1.33 kilo ohms.  If D1 is forward biased, then R1 and R2 share the same node on one side, but they are not in parallel because of voltage sources on the other side. So how did the author combine these two? Is he using superposition to short out the voltage sources? But then where does 1.33V and 2.66V come from?


texts: Help with Flash memory to GPIO pins on FPGA dev board

texts:
Been trying to access the FLASH memory on this DE1 dev board, but having no luck. I'm using this to interface with a Super Nintendo system, and I'm trying to read a small test ROM file stored on the FLASH. I've verified that the contents are good by dumping them back to a file and tested it.

I've written some basic VHDL to do this, but I think I'm missing something with the data bus end of it. I've done basic address line controls with CPLD chips before using VHDL, but never tried with a data bus.

Here is the code:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity mapper_test is
port(
FL_ADDR     : out   std_logic_vector(21 downto 0);
FL_DQ       : in    std_logic_vector(7 downto 0);
FL_CE_N     : out   std_logic;
FL_OE_N     : out   std_logic;
FL_RST_N    : out   std_logic;
FL_WE_N     : out   std_logic;

SNES_ADDR   : in    std_logic_vector(21 downto 0);       -- SNES ADDRESS BUS
SNES_DATA   : out   std_logic_vector(7 downto 0);        -- SNES DATA BUS
SNES_ROMSEL : in    std_logic;                           -- /ROMSEL (CART PIN 49)
--SNES_RST  : in    std_logic;                           -- CART RESET
--SNES_VCC    : in    std_logic;                         -- CART VCC
SNES_RD     : in    std_logic                            -- SNES /RD

);

end mapper_test;

architecture arch of mapper_test is

begin

--FLASH CONTROL PINS
FL_CE_N  <= SNES_ROMSEL;                                -- INPUT SNES /ROMSEL TO OUTPUT FLASH /CE
FL_OE_N  <= SNES_RD;                                    -- INPUT SNES /RD TO OUTPUT FLASH /OE
FL_RST_N <= '1';                                        -- KEEP FLASH /RST HIGH
FL_WE_N  <= '1';                                        -- KEEP FLASH /WE HIGH

--FLASH DATA PINS

SNES_DATA(7 downto 0) <= FL_DQ(7 downto 0);             -- INPUT FLASH DATA BUS (7:0) TO OUTPUT SNES DATA BUS (7:0) FOR READ MODE

--ADDRESS PINS
FL_ADDR(14 downto 0)  <= SNES_ADDR(14 downto 0);        -- INPUT SNES ADDRESS (14:0) TO OUTPUT FLASH ADDRESS (14:0)
FL_ADDR(20 downto 15) <= SNES_ADDR(21 downto 16);       -- LOROM CONFIG ---> INPUT SNES ADDRESS (21:16) TO OUTPUT FLASH ADDRESS (20:15)
FL_ADDR(21) <= '0';                                     -- KEEP FLASH(21) LOW FOR 2MBYTE ONLY

end arch;

When I jumper the GPIO wires (all SNES ins and outs in code) over to my test cartridge, I get nothing but a black screen. I've even tried tying my LEDs to the FL_DQ pins to see if there is any activity, and there is none. So it seems to me like the data bus isn't going through properly. I just want to connect the FLASH to the SNES pins, nothing fancy at this point.

Can anyone tell me what I'm doing wrong?


texts: Difference Between RMS noise and PSRR in an LDO

texts:
I am trying to choose a low dropout linear regulator to partially smooth the output of a dual rail SMPS I'm using to power analog circuits. I'm confused about the difference between the specified RMS noise and the PSRR of LDOs. Here is an example from a datasheet I have been looking at.

If my SMPS were to have 10 mV @ 1MHz of ripple on the positive output, and I used the device detailed above, should I expect .8uVrms of noise on the output, or would the SMPS ripple be attenuated by 76 dB and appear on the output. The device I'm taking these numbers from is the LT3045, datasheet here.

Also, I understand that the specifications listed in the features section of the datasheet are best-case device parameters, and that a much closer inspection of this LDOs documentation would be required to effectively utilize it. I don't plan on using this particular chip, as I'm just looking for information on how to use these figures found in all LDO datasheets.


texts: How to use characters in strings outside of the printable ASCII range?

texts:
I am trying to create a string with characters outside the ASCII printable range.  I am using an STM32 microcontroller using the µVision IDE with the Keil compiler.  The documentation allows various escape sequences, including one for "ASCII code in hexadecimal."  When I just want one character there is no problem, but if I want to put other numbers in the same string after the character, I start getting issues.

This works.

char myString[10] = "\x06";//(It gives me 0x06,0x00,...,0x00)

This doesn't.  (It gives me 0x60

char myString[10] = "\x060";//(It gives me 0x60,0x00,...,0x00)

The more characters (0-F) in the same continuity that keep getting appended as hexadecimal digits of the same number (it will even throw a warning that it is out of range if the number gets too big).  Is there some way around this?  Might this be a compiler issue?


texts:
I've designed a circuit that relies on the action of momentary pushbuttons as described here:

http://tymkrs.tumblr.com/post/19734219441/the-four-pin-switch-hooking-it-up

Namely, that a 4 pin pushbutton can have two pairs of pins (1,2) and (3,4) such that:

Switch Open:
(1 and 2) are a connected pair, (3 and 4) are a connected pair and the pairs are not connected to each other

Switch Closed:
(1 and 3) are a connected pair, (2 and 4) are a connected pair and the pairs are not connected to each other

However, after ordering some buttons that then have the alternate (and seemingly more common) operation of

Switch Closed:
All pins connected.

I realised the error of my ways.

How would I differentiate these two types of buttons when searching?
Does anyone have an example of a component explicitly implementing the button behaviour described above?

[Unfortunately I rushed ahead and already ordered a PCB with a 6mm push button footprint after testing with similar components, excluding the specific button. I'm aware I could implement other solutions, but if someone has an answer to this specific question, it would save me a lot of rework.]


texts: How to make a PLL output the phase modulo 360°?

texts:
I have made a PLL to obtain the mechanical angle encoded in quadrature sine signals (the envelope of a resolver output) ; it implements: error=in-out is approximatively equal to sin(in-out)=sin(in)cos(out)-cos(in)sin(out)).

I tuned the controller with Simulink's control toolbox and the PLL works, however I can only seem to get unbounded angles out of it, i.e. the angle output increases with time without bounds beyond 360°. I tried putting a modulo 2*pi operation inside the PLL at this location, but it throws off everything and the loop fails (certainly because of non-linearity):

How to make this PLL output a bounded angle (between -180° and 180°)? Meaning, obtain a sawtooth between -180° and 180° on the considered block diagram.