texts: How to store a credit-card-sized FPGA+CPU board?

texts:
This might sound like a really dumb question, but I'm trying to figure out how I'm supposed to store a Parallella board board that is always running a Linux server and is physically connected to a router.

Right now I've put it on top of a glass plate (plate, like the food kind) which admittedly "works" but is physically unsecured and therefore prone to falling off. And also ugly.

Ideally I would want to both (a) prevent the FPGA from accidentally touching something like paper or the carpet (it gets a little hot), and (b) prevent the whole circuit from accidentally touching something (due to static electricity or accidental shorts, etc.).

How do hobbyists store basic circuit boards like this? Do they just leave them on their desks or in some corner of the house with no type of enclosure? Or are there containers for this purpose? I can't even figure out what to search for since searching for "electronics trays" and things like that doesn't really show anything useful...


texts: How to make whole top side of project box glow uniformly?

texts: I have a transparent project box encasing my breadboard with an LED on it. I want to use this LED to make the whole top of the box glow uniformly. Does anyone have any ideas? I tried using soft plastic, about 4 mm thick and drilled a whole halfway through it for the LED. Even after using sandpaper, you can still clearly see where the LED is, and the illumination is a quarter of the box, at most. The box is about 5x7 cm.


texts:
I got this component from someone clearing out their garage. At first I thought it was a solenoid but the ‘pin’ section doesn’t move and there is no spring on the outside of the component.

I haven’t had a chance to ask a professional or to hook it up to power, but I was hoping it could be identified. The component has no identifiable markings or writing, and after checking the print on the wiring it is specifically about the wire not the component. See pictures attached.

Any help would be appreciated.


texts: I have a Transformer Core - need help with winding/calculation

texts:
I have a microwave oven transformer which i had damaged in the process of removing the high voltage secondary. I will be using this for spot welding 18650 cells. I have all the required figures

I wish to know if change the wire gauge would affect the current output in the secondary. I need the max current output.

As far as I understand the heat loss and resistance depends on the primary winding gauge and the current draw in the secondary depends on the width of the cemetery core and the gauge of the secondary winding, correct ?

With that said 22AWG would be a little less thereby creating more heat in the primary but would help adding more turns on the secondary thereby increasing current draw

Link to MOT dimensions


texts: Detect 230 volt main supply in a cheap and easy way

texts:
I need to detect by if one o more pumps are really connected to the 230 Volt main supply. Each pumps is activated by means of a triac isolated by a MOC3021. Arduino commands the optoisolators and I need to detect if really the triac has switched on (e.g. the triac didn't switched due to a fault).

The solution has to be possibly cheap and reliable.
I found this simply circuit from a site, and I would like to know your opinion. The optocoupler is a 4n35 or pc817 or similar. What also I need to know is if the 390K resistor should be dimensioned more than 1/4 W and if has to be a special resistor for high voltage. Thanks a lot.


texts: Could I use my PV inverter at night, feeding it from battery power? What would be needed?

texts:
First off, this is pretty much just a thought-experiment! I don't plan on actually going through with this as I'm sure it would void any warranty I have on my installation. Also, I'm totally unqualified as an EE; some basic schooling on the subject but not much more. Doesn't change the fact that it can be fascinating at times =)

Anyway, that said, I was randomly clicking through product pages on Ali Express this afternoon and found quite a few of MPPT controllers capable of charging (banks of) Lead-Acid batteries.

Currently, my (SAJ) solar-inverter is connected to its full capacity with panels cells and on a clear and sunny day it will deliver almost 30kWh solar energy to 220V AC. Part of it is used up directly in the house, part of it is sent to the grid. When there is no sun, I can recuperate that excess back from the grid. As there is no such thing as a free lunch, I'm "taxed" for the privilege of using the grid as a battery by means of the (theoretical) capacity of the inverter. Thus, adding more panels would result in me having to add an extra (or bigger) inverter and thus pay extra too. That got me thinking: what if I installed another -- independent -- string of PV panels, had it store the resulting energy until the sun is down and then somehow push that energy through the inverter towards the grid. Barring any losses this would then result in me putting twice the amount of kWh on the grid without the need of a bigger inverter.

Apart from avoiding extra taxation, this might also be useful to charge an electric vehicle at night (usually at work by day, at home by night) without the need for a separate AC circuit. Initially drawing from the Lead-Acid batteries and seamlessly switching to grid power as the former go empty (1).

Naively it would come down to:

By day, business as usual, the inverter is connected to the PV panels
By day, the 2nd array stores energy into say 24 batteries using 6 strings of 4 batteries (48V) each)
By night, the PV panels are disconnected from the system
By night the batteries are 'rewired' in series (288V (2)) and connected to the inverter whom then empties the batteries into the grid.

Things I wonder about:

Would the inverter be able to handle the surge of incoming energy? The batteries can easily 'flood' the electronics with hundreds of Amperes but I would assume the latter are capable to limit the incoming flow (3)
What device would be able to pre-limit the current to say 15A without too many losses; if such a thing exists?

Thank you for any insights!

(1: even MORE electronics needed I guess to avoid the batteries being drained all the way to the bottom, which as far as I know is "a bad thing (tm)", even for deep-cycle batteries)

(2: the DC voltage required is 80V-600V, so 288V should work fine. To get 30kWh like this each battery should have 1.25kWh or shy over 100Ah which sounds feasable although not cheap =)

(3: in fact, I've already got 20% over-capacity PV wise but the panels are oriented partly South, partly East so I only get more than 100% in rather exceptional situations. In those cases you can see the inverter top off the curve to its max capacity. From what I read it does this by upping the required voltage on DC side thus limiting the panels output current as it goes out of the 'ideal' V/I curve; I guess the same would be true with the batteries?!?)


texts: How is a four terminal sensing compensating conductor resistances?

texts:
A four terminal sensing is used to compensate the resistances of the conductions. Why is that as I even use more conductions than in a two terminal sensing?

The current from the current source will flow through conductions which have a resistance and the voltage metering is also connected via connections.
So why are these conduction resistances negligible?


texts: Ideal circuit for opto-isolated push button input

texts:
I'm trying de design isolated and robust push button circuit. I have to
take precautions for glitching, debouncing and etc. I want to use opto isolator. I draw a simple schematic but I'm not sure if it is ideal. I have 10 push buttons and I will apply same circuit for all.

Will It cause any problem while getting interrput (I'm planning to
use external interrupts on mcu firmware)
Need I still use a capacitor to prevent debouncing ?
Need I still use 74HC14? Is it useful ?

I need advice about this button issue.


texts: LM239 Supply/Open Collector Output Voltage

texts:
I wish to power LM239 comparator from a +5V single supply and use the open-collector output to switch a 24V load (resistor plus LED). Is this permissible?

http://www.ti.com/lit/ds/symlink/lm239a.pdf


texts:
Does the output of a DAC have quantization noise when outputting a DC voltage value? It seems to me that it will not as long as the DC value does not fall between two output levels of the DAC.

All the information I have been able to find regarding quantization noise of a DAC discusses it in the context of outputting a sawtooth wave or sine wave, and then it ends up being proportional to 1 LSB spread uniformly over the bandwidth of the DAC.


texts: Reduce noise on 2m I2C bus using motorcycle power

texts:
We would like to use an I2C bus with a cable length of 2m (unshielded twisted pair) on a motorcycle. The I2C bus connects an arduino to a sensor and is set to 10kHz (we have tried the common 100kHz and 400kHz as well). The arduino is powered using motorcycle power with an M3-ATX 6-24V DC/DC regulator in between: https://www.cartft.com/catalog/il/834 this is supposed to smooth voltage spikes from the alternator when the engine is running.
Unfortunately we cannot power the arduino by separate battery or uncouple it from the motorcycle electronically (might be an absolute last resort but should be avoided).
When the engine of the motorcycle is not running and the arduino is only powered via the motorcycle battery we observe the following signal and our I2C bus works:

However if we start the engine of the motorcycle we see the following signal and the I2C bus does not work.

here is a zoomed in view of the noise we are observing. We believe this is due to the alternator of the engine.

How do we smooth the signal of the I2C bus appropriately? We thought that the DC/DC converter would be sufficient and have previously tried simple buck converters but no luck. The power coming out of the DC/DC converter is unfortunately not very smooth.
Any help or suggestions would be greatly appreciated!
Thanks
EDIT: noise is also present in the power lines (3.3V at the arduino) although it appears to have a much lower amplitude than the noise seen on the I2C bus.
Here power without engine running:

Here power with engine running:


texts: Schmitt Trigger not reaching full saturation

texts:
I'm trying to develop a sensor based on the optoelectronic device CNY70. I want to filter the signal in order to be read by a microprocessor, where the threshold to change between logic levels could be adjusted manually using a potentiometer. Then, thinking of an ideal operational amplifier, I came with something like this:

simulate this circuit – Schematic created using CircuitLab

With this single supply construction for the op amp, I would have to get a hysteresis band for the logic level switching of approximately 150mV, centered around the voltage given by the potentiometer on the inverting gate.

I built the real prototype using the op amp L2904N and made some measurements with a voltmeter and an Arduino. The hysteresis band for the Schmitt Trigger configuration works almost perfectly for switching the logic levels, however, those logic levels does not correspond with the supply of the op amp... Ideally, I should get 0V - 5V logic levels, but I'm getting 0V - 3V levels.

So what's the non-ideal thing that is causing this problem? I think it could be related with any maximum output current the op amp can drive, but the datasheet actually does not give any information about output current. What do you think?


texts:
Is there a standard protocol for motion sensors, PIR sensors, etc. to tell parking lot lights, etc. that motion has been detected, so the lights need to turn on?

I'm not asking for protocols that could be used. Hundreds of protocols could be used for these systems, such as "+12 V for motion, GND for no motion", "X10", "+5V for no motion, GND for motion", "Zigbee", or etc.

What signal levels and number of wires, etc. are actually used with off-the-shelf sensors?
(An ideal answer will link to one or more datasheets for such sensors).

(This question was split off from How do you dim a streetlight bulb? ).

EDIT:

While I appreciate the datasheet for the "actual sensor" PIR component, I'm not so much looking for the voltages/timing on the pins between the "actual sensor" and the PCB it is soldered to.
I'm looking more for: What is the the voltages/timing on the long wires/cables running between the off-the-shelf prepackaged "sensor assembly" (is there a better term?) and the lights?
How else can I design something to be compatible with many off-the-shelf devices, some of which haven't even been designed yet, rather than only working with one particular device?


texts:
I want to buy a 1mH inductor. I am just making a basic LC filter and I see that there are "common mode" inductors.

I found one here with a data sheet:
http://www.mouser.com/ds/2/355/DS_EV-EHseries_20110616_web19-8801.pdf

The inductor is 1mH and "common mode". Can I use this inductor to give me 1mH?(it meets my current rating too)

There are four legs on it as well. Will only using two of them give me half the inductance?


texts: What is the range of an IR sensor in a prototype comparing to real life application?

texts: I'm currently having a prototype which involve using an IR sensor for obstacles detection. But the results required a comparison of the range result I obtained from the prototype to compare it to a real life application. I have been surfing the Internet but none of the information was useful. I hope someone could help me to sort this up. Thanks and have a great day.


texts: try to understand ground and power planes

texts:
I'm trying to understand how signals flows in the GND layer.

Let's assume that I have 4 layers PCB:

Signal
GND
POWER
Signal

The CPU connect to the GND layer with VIA and I want to know, how the CPU return current will flow to the "Negative Terminal"?

I read that the return current in the GND layer flow below it signal, so the current flow directly from the via to the negative terminal in the shortest way?

Or does it flow below the VCC trace (in RED) and from there to the negative terminal?

About the VCC layer: I once told that the VCC layer can act like a GND layer with every thing related to return current.

I don't understand how this is possible for current to return via VCC layer?


texts: What kind of equipment would I need to apply nonpermanent extension wires to test points of a PCB so I can access them via a microcontroller?

texts:
This is a DIY project. The title question is the first problem I'm considering, but the entire project is the goal I'm not an expert in hardware, but neither am I uninitiated. Put me at around an intermediate. I'd like to not break the electronics I'm working with so I'm trying to square away everything I need to do well before I get started, which is why I'm here. I'd like to not give a lot of unnecessary details so I might be withholding relevant details that would  help give an answer. Please comment to let me know.
These are the criteria I'll know i need for this portion of the project:

I'll need to apply a connection to about 20 different small PCB test points of varying sizes located at different parts of the board

The connections need to be stable

The connections need to be detachable (no solder)

The connections need to be insulated from the rest of the PCB

I need to be able to reattach the casing
The casing has two "layers" when disassembling it. The first layer in has access to the rechargeable battery and a "door" to the "innards".

I'd like to place my array of test point extensions so they stay inside the first casing so I can clip them to my microcontroller only when I want to make use of them and so I can use my device normally the rest of the time.


texts: How to write inductor ODE equation properly?

texts:
I've drawn a following scheme, and now want to write ODE system for describing inner processes, in order to explore it:

simulate this circuit – Schematic created using CircuitLab

I wrote the first part, and it is clear enough, as I have a leaky capacitor:

\$\frac{dV_m}{dt} = \frac{I_{in} - \frac{V_m}{R_m} - I_a*SW1}{C_m}\$

But second part is not clear at all, and is not working. I thought like it should work basically the same as capacitor:

\$\frac{dI_a}{dt} = \frac{V_m*SW1 - \frac{I_a}{R_a}}{L_a}\$

It kind of creates knee on current graph(when i close switch) - follow the red arrow on following screenshot:

Green knee is ok, its just due to Iin set to zero via heaviside function somewhere else in program, sorry for it, just distracts.

But for red I feel that desired behaviour should be like sinc stuff, so what was expected is like this, because it has some L:

So.. Could you correct me? Or, how to write correct formulas, describing processes in this circuit?

PS

For the curious, its real-world warm-lamp doomsday device. It connects directly to the mains through series lamp, its very dangerous, so you should not do this at home: It has +310VDC on a thyristor radiator..


texts: Program an ATTINY85 on the PCB is causing me some trouble

texts:
I'm having a hell of time getting AVR ISP header on my circuit board to actually allow me to flash the chip. Basically, with an ATTINY85 you pretty much have to share programming pins with pins used by your program. I think something about this sharing is causing issues.

In the below schematic, J3 and J4 go to a board with 7 addressable APA102 RGB LEDs. J3 provides clock and data SPI signals, and J4 provides power and ground.

I have LED clock on the pin PB2 or SCK of the ISP headers, and the LED data pin on PB4 which is not shared with the ISP headers at all. PB3 controls a high power switch on the LEDs to prevent them from drawing current in sleep mode.

When I tried to flash a program with this setup, it seemed to work at first, though I could see red pulses on the LEDs, which surprised me. But the last step of the upload, the verification step checks the program was written correctly, failed. And now the chip can no longer be programmed since avrdude just gives avrdude: initialization failed, rc=-1

I managed to remove the chip form the board and put it in a socket by itself in a breadboard. In that state, I was able to flash it no problem, and it worked great when I soldered it back on to the board. But when I tried to flash it again on that board, the exact same thing happened. Clearly something in my circuit is to blame. But I'm not sure what.

What is preventing my circuit from allowing it to flash the ATTINY85? And, if necessary, what can I do to insulate the components from programming signals that they shouldn't need to be aware of?

Chakra Pendant by Squeegy 46acb26f5f80a881 - Upverter http://upverter.com/Squeegy/46acb26f5f80a881/Chakra-Pendant/embed_img/14256226900000/

^ click that and you can browse both the schematic and the PCB because Upverter is neat.


texts:
I'm refurbishing an old Apple II Power Supply made by Astec. It's working now, but I damaged the connectors which connect the Live and Neutral wires to the Power Supply PCB. On the PCB are two posts, each about 1cm tall, and maybe 2mm in diameter, with a "bullet connector" like shape. The wires have what looks like simple cylinders which plug onto the PCB posts.

I can't find any reference to, or even images of such connectors using Google. Does anyone know what they are? I guess they might be proprietary to Astec, and possibly even obsolete, but before I do anything drastic, I'd like to try to replace them with the right ones.

Here you can see the connector in the foreground, beside the fuse:


texts:
In the magnetic ballast type fluorescent lamps (old ones),what is the need of a capacitor in the starter circuit and what determines it's ratings?
If my understanding is correct its a bi-mettalic strip opening and closing producing an inductive kick,so it should work fine without the capacitor too.


texts: NPN Transistor Current Limiting Changes From Collector Load To Emitter Load

texts:
as part of an audio project I've been working on, I've been measuring the current consumption of a class A amplifier driving a 4Ohm 5W speaker (square wave signal).

Strangely, I notice that this:

Draws more current than this:

Why is that?


texts: I'm looking for a circuit to extend my 24v linear actuator all the way out and then all the way back in when I push a button. I've tried mechanical switches but I want the cycle to be automatic.


texts: Doubt about circuits with cells having internal resistances

texts:
First take a look at the schematic diagram below

simulate this circuit – Schematic created using CircuitLab

And let's assume the the internal resistance of the cell is (r).

So here in this case E.M.F of the cell decreases, because it is given by the formula (E-ir_1) , and what I want to know is whether it is correct to use equivalent resistance between the internal resistance (r) and the other resistor(R) as (r_1), like what I have done just below

E.M.F of the cell ===> E-i(r+R)

If I assume the same thing here also, is it possible to write the E.M.F as what I have wrote above ?

simulate this circuit

I am confused about this, I come across this problem or let's say confusion  when I am doing questions on potentiometer , so I hope it is better  to know about this which  is already get messed in my mind .


texts: Why would a COB be utilized in this circuit?

texts:
For Christmas my company handed me a small LED "work light" that wasn't bright enough to light up any real work, so I figured I'd tear it down see what was inside hoping the the lesson would be worth more than the light.

I expected a tiny circuit with a button and resistor. I got two of those things, but how did the resistance work in this circuit? I didn't take a before photo, but the only thing different is a mound of dried, opaque white paste where there is only a paste circle now.

I tried Googling resistive paste, and there is such a thing, but I don't think this is it. Did I chip off a tiny resistor in there that I didn't see?

Edit: After some comments pointing out that this was likely COB, I've come to the conclusion that the momentary switch couldn't, on it's own, maintain the state of the light. Therefore there would need to be some logic in an IC. The original question wasn't so much focused on what COB is (although I learned that), but instead why a COB would be utilized instead of a much simpler circuit.


texts:
I'm fooling around with a PMOS, a Fairchild FDD6637, and pondering whether it would be possible to use Rdson as a sort of shunt-resistance for measuring the voltage drop, to get the amount of current flowing through drain and source.

The circuit will be using 2A at most. Here I'm thinking that if there's a short circuit somewhere, and the current rushes, I want to be notified when the current goes above 3A.

With Vgs = -4.5V, Rdson is 20mohm. At 2A, the Vds-drop will be 40mV. At 3A, the drop is 60mV.

So I had this idea: feed the drop into an opamp and pre-amp it to a more feasible level. Exactly how it's supposed to be coupled is unknown at the moment (I'm just playing with the idea), but let's say I couple the opamp to convert 60mV drop to, say, 4V (Vcc is 5V). Then let's say I deliver these 4V to another opamp (comparator) where one of the reference inputs is set to a fixed 3.9V, making it trip when the 4V arrives. That way I'll get a signal telling me there's a current rush.

Question: Am I thinking correct, or am I attacking this problem from the wrong direction?


texts: Modbus RTU Implementation to Automate Temperature through PIC Microcontroller

texts:
I would like some help about implementing the Modbus RTU communications protocol in an automated system that I am trying to develop. I am confused about how to generally set up my network because I have never used modbus and am generally new at programming PLCs.

I want to monitor the temperature of an oven that is held by a Watlow F4 temperature controller. It requires Modbus RTU communication through an RS-232C interface. I want to constantly read the temperature in the oven and process the data through my PIC microcontroller, which will then communicate back to the F4 controller to adjust the temperature accordingly.

-In this case, will the PIC controller be my master, while my F4 controller is the slave?
-Is the Modbus RTU protocol simply a way to structure the data transmission, or do I need to download software that uses the modbus implementation? In other words, is the Modbus RTU protocol simply the way you should structure your code to accept and transmit the data packets between the master and slave?
-Is it possible to simply program the PIC to automate the temperature indefinitely without having a terminal like a PC be the master?

I want to make sure I am understanding the general structure of my project and whether there are any issues with the way I will set up my Modbus network. Please let me know what I can do. Thank you for your time.


texts: How to use a multimeter to test the resistance of my tongue?

texts:
I just purchased this cheap-o multimeter:
https://www.amazon.com/AstroAI-Digital-Multimeter-Voltage-Tester/dp/B01ISAMUA6/ref=sr_1_1?keywords=astroai+am33d&qid=1551837071&s=gateway&sr=8-1

I'm trying to test the resistance of my tongue by touching both probes to it (I have the red plugged into the middle port and the black into common). I start on the highest number as instructed (200M) and it gives an output of 1.1M Ohms. At 20M it fluctuates between 10M and 20M Ohms. Below that it blanks out and just says 1.

I read online that this exact procedure should give an output of 70K Ohms, the approximate resistance of the human tongue. What's up with my multimeter? Or is my tongue just insanely resistant to electricity?


texts: How to configure atmega 328 IO pins to reduce the power?

texts:
I am having a atmega328p for my home project. Consider the pins

Pin B2 - connected to LDO enable. Output
Pin D7 - MUX s0
Pin B0 - MUX s1
Pin B1 - MUX s2
Pin B4 - MUX s3
Pin c3 - MUX enable

Pin B3 and B4 - It is taken out of the board and not connected anything. But in the program, giving a pulse. I can test the pulse by connecting a LED. But actually nothing is connected. These are output pins

I need to know how to configure these pins to consume lower power while sleeping the atmega. From the datasheet, unconnected pins should be configured as input with internal pull up enabled.
Refer : 13.2.6   Unconnected Pins

Is this statement suited for the above pins?


texts: In a SR NOR latch, assume my present state for Q=0, Q'=1. Now my inputs are S=1, R=0. According to sr nor latch for that inputs I should get output/next state as Q=1,Q'=0 but I dont understand how, as Q'=1 of ps is my input along with R=0 which gives next state output as 0 but is is supposed to be 1. please help i have an exam soon. thanks!


texts: Can I use a 940nm laser diode for a remote control?

texts:
Most TV remotes use 940-950nm LEDs. The TV-B-Gone uses a combination of short ranged, wide output and long ranged, narrow output LEDs, to have a combination of easy mark hitting and longer range.

Say I'm willing to pay the cost for a 940nm laser diode. Could that be used to design a extremely long ranged "sniper" version of the TV-B-Gone? Or would I just be setting peoples curtains on fire?

I tried searching the web for applications and found uses in hair removal, fat reduction, and defense. The only application remotely (no pun intended) related to my use was as fiber lasers, which I imagine to be a signaling use.


texts: Drain to Source Current Waveform on Mosfet is Slow

texts:
I am currently trying to build conventional bi-directional DC converter and see the mosfet behavior when controlled with PWM signal. based on theory, the drain-source current (Ids) and drain to source voltage (Vds) will switch at the same times when the mosfet turned on or off as illustrated in figure 1. this known as hard switching. but when i tested in actual bi-converter that i made, the waveform of Ids is somehow different from what i expected (far from trapezoidal waveform). As you can see in Figure 2, the Ids is somehow take a long time to rise and fall even the gate already switched.

Figure 1. Switching Waveform on Mosfet

Figure 2. My Actual Switching Waveform on Mosfet, yellow (Vds), Blue (Ids), Magenta (Vgs)

I am quite new to electronic, and what I've been doing so far are

Made Conventional Bi-DC Converter. the mosfet behavior is in figure 2.
adding capacitor paralleled with drain pin and source pin on mosfet. this capacitor affect on Vds.
the voltage observed with passive oscilloscope probe; and current observed with clamp probe (not stable waveform) then switched to differential probe (more stable waveform).

what I want to ask are:

is there any possible explanation of this mosfet Ids waveform behavior?
what can I do to make the Ids waveform on mosfet more trapezoidal (close to ideal hard switching waveform)?

I knew that hard-switching is not good, but i need to generate hard switching waveform in actual converter i made for my project. anyone with more experience with this Please help me, thanks.

EDIT:
This is my converter schematic. figure 2 generated under buck mode.

Ids, Vds and Vgs tested on S1 switch.

simulate this circuit – Schematic created using CircuitLab

Input: 0-30 Volt DC regulated power supply.

Load : variable resistor 0-10 ohm.

Switch: Mosfet IRFP4332

www.infineon.com/dgdl/irfp4332pbf.pdf?fileId=5546d462533600a40153562c58682013

Mosfet Driver circuit based on this blog: TLP250 Mosfet Driver Circuit

tahmidmc.blogspot.co.id/2013/05/using-tlp250-for-isolated-mosfet-gate.html


texts: How to safely connect unused opamp stable for gain of +2

texts:
Please refer to AD828 or any other bipolar op-amp not unity gain stable.
Which of the two below cases is better? Any other suggestion?
Simulation suggests the second, but I need to understand if the first (which I built) is still safe.
Be aware that I have not easily access to ground in my PCB close to the opamp.
Please read also note 1 in the following article, which suggested me to include a high value of Rf in the second case:
"What shall we do with an unused op-amp?"

simulate this circuit – Schematic created using CircuitLab


texts: Does a BNC splitter introduce defects into the signal?

texts:
I'm currently doing some contract work that includes finding and recommending a signal generator model for frequency measurement device verification. The verification scheme requires generating a square signal of sound frequency (20-200 Hz) with small tolerances (10-6 relative frequency error) that goes to two devices - the one being verified and a reference one. The devices then count the impulses over a slice of time. Other properties of the signal specified are slope length and voltage (maximum and mean-square).

The official paper that I'm referring to for the technique uses a two-channel generator for an example setup (but doesn't specify that it's necessary). I'm thus wondering if I can use a single-channel generator with a BNC splitter for the same effect.

That is:

Does a BNC splitter introduce any noticeable defects into the signal - e.g. reflections, distortions etc? The only thing I can readily think of is due to the conservation of energy, the voltage may be two times (or rather, sqrt(2) times) smaller - but that is trivially fixable.


texts: Most efficient way to convert multiple voltages?

texts:
I'm driving a rgb led strip and an arduino from a variable power supply between 12-15 volts. So I'm looking at a buck converter for the 12v led's but I need 5v for the arduino as well. There must be a better way than using multiple buck converters.

Any idea's?


texts:
I have a prolifc USB to serial cable that I want to use to recieve infrared signals coming from a TSOP Sensor

I saw it is possible to connect a classic rs232 connector with TSOP here.

How can I connect it without damaging something ?


texts: SRAM and D-flip flop instead of transistor

texts:
I have read about the internal structure of SRAM and we need 6 transistors to store 1 bit.

But what bothers me is why can't it be made using D-flip flops instead of going deep to transistor-level. It will lead to the same result, so where is the riddle?


texts: VCVS in LTSpice Operating as a Comparator

texts:
I am using a VCVS in LTSPICE.

I am confused about the command in the Spiceline for using a Table.

I want to use the VCVS as a 1 bit Comparator instead of making a transistor based one.

What will adding the following spiceline for a VCVS in LTSpice do ?

table=(-0.5 0, 0 0, 1.0e-6 1, 0.5 1)

Will it set the output to 0 when the VCVS is input with -0.5, 0 output when it gets 0, 1 output when it gets 1u and one output when it gets 1?

Is this correct ?

Thanks.


texts:
I'm using the following setup to measure a voltage across a resistor.
I measure it both by a DAQ system and an oscilloscope.
Below is the illustration for the setup:

DAQ is the data acquisition hardware which is:
http://www.mccdaq.com/PDFs/manuals/USB-1616HS-BNC.pdf

I1 is a current regulator which is set to 4mA constant current.
OS is an oscilloscope.
Mains is the mains multiple outlet for power supplies.
A1 is the DC power supply for the DAQ.
A2 is the DC power supply for the I1.
R is the resistor through which current passes.

Voltage across the R is fed both to the DAQ and the OS.

Here is the problem:

When i observe the voltage across the resistor with the oscilloscope,
it is around constant 2 Volt with a very  very low ripples.
Voltmeter also measures 2 Volt. This is expected, since R = 500 ohm.

But when I make data acquisition I saw a very low mean value around 0.7 Volt.
Then I plotted the data from the data acquisition. Below plot is what I obtained:

It looks like a 100 Hz pulse with 2V max 0V min.
DAQ is obviously wrong. What might be the problem here?


texts: Set multiplexer inputs to a logic 1 state

texts: How can I set, in Orcad, all the entries of multiplexer(in the picture) (except: 1, 13), to logic state '1' (for example, I understand that if I place 'ground' to some entry, then it will be equivalent to '0' logic state. That's what I want to do for '1' logic state) ?


texts:
I was designing the footprint for this FPC connector: Datasheet

The recommended land pattern is shown here:

The issue I encountered is that the pins on one side protrude outside of the pad:

I triple checked the dimensions and the outer "toes" and the "heel" on one of the sides seem fine.

Would the absence of the "heel" fillet on one of the sides be an issue? It's not that I think that Molex has provided a bad footprint but more that I fear I might have misinterpreted something.

Source: IPC-A-610D

Update

These are the measurements on the land pattern depicted above:

I moved the pads to be 2.9mm center to center, and this is the result:

Which is weird, because the long pad is still on the short "pin". Flipping the part to match the long pin with the long pad, this is how it looks:


texts: How to track down all the registers connected to a specific downstream register? (for set_max_delay's --from)

texts:
The Xilinx Vivado's set_max_delay requires -from to be set.
Basically I'd like to set max delay TO a register.
Because there can be lots of registers source to my destination register, I don't know their name.

set_max_delay 3 -datapath_only -to [get_cells dest_reg*] isn't valid because it doesn't have -from option.

My plan

Get all the input pins (D, CE, R) of the destination register

set dest_pins [get_pins -of_objects $dest -filter {REF_PIN_NAME == "D" || REF_PIN_NAME == "CE" || REF_PIN_NAME == "R"}]
The danger is that there might be other input pins...

Get all the nets connected to these input pins

set nets [get_nets -segments -of_objects $dest_pins]

Track down all the output pins connected to these nets

set source_pins [get_pins -of_objects $nets -filter {IS_LEAF && DIRECTION == "OUT"}]

Get all the registers of these pins

set source [get_cells -of_objects $source_pins]

This looks too overkill just to add a CDC constraint on a single register.
Question

What's the best way of adding a constraint using only its name and nothing else?


texts:
Hey all - I have an AVR project in mind that will require a 13 by 13 LED matrix of bright white LEDs. I'll be wiring up my own matrix to do this (not using premade 8x8's). I plan on using some shift registers to control the anodes/cathodes (columns/rows).

This will be my first project with an LED matrix and my first time working with shift registers.

I'm not sure if my shift registers can handle the current for this many LEDs (if I lit up an entire row for example). I don't know the proper way to wire this up, but I understand that I should control each row (maybe each column?) with a transistor of some kind between my microcontroller/shift register and the LEDs. I'm having trouble finding good explanations of how something like this should be wired up, or how to calculate the current requirements and how that translates to picking the right components.

Any advice would be appreciated. Thanks!


texts: Configure wiring for reversing a small geardrive 115v motor

texts:
My question is: Would this same configuration work with 115v system.
Motor; both switches and the relay are 115v 10a and are compatible. Would the diodes D2 & D3 have to be changed to accommodate 115v?
Also the schematic indicates a coil bypass under D3; any ideas as to what this should be? Be gentle guys...virgin prototype here..LOL

It's this motor:
https://www.mscdirect.com/product/details/36690741?rItem=36690741


texts: Non-Polarized Electrolytic Capacitor Replacement

texts:
To the best of my abilities, I'm trying to repair an Atari 800XL which was sold as "non working unit". I found a new graphics chip and it's working ok. I though that, since I had it opened up, it wouldn't be a bad idea to replace the caps, even though they didn't show any leakage. So I did, i changed all of them but 3 are still remaining. They do not have any polarity marking and I eventually learn that they are Non-Polarized Electrolytic Capacitor. The marking reads:

"Nicon 4.7 uF, 35v, NP, -40 to +85ºC"

I'm trying to find replacement for these but I can't seem to find exactly the same and, since my knowledge on the topic is very limited (no formal education in electronics whatsoever) I would need some help.

The closest thing I found are capacitors with the same range of values but marked as "Bi-Polar" instead of "NP". I don't really know if it means the same as info I found in internet is contradictory.

If anything else fail, could I replace these capacitors with non-electrolytic ones? Again, since my lack of knowledge of non of them have polarity... all seems the same through my eyes...

Any help will be appreciated.


texts: First time using a Raspberry 3B+ for 1.8v SPI BIOS flashing, I have some questions first

texts:
So this is the first time I'm attempting to flash a BIOS chip using a Raspberry Pi 3B+.

I have the following items with me, a SOIC-8 clip, a Bi-Directional Logic Level Converter, and a Raspberry Pi 3B+ (plus).

This is the logic level converter I brought: KNACRO 8-Channel 5V/3.3V IIC UART SPI TTL Bi-Directional Logic Level Converter  https://www.amazon.com/dp/B071RWFF7C

This is the BIOS chip I'm working with: Winbond 25Q64FW https://www.winbond.com/resource-files/da00-w25q64fwc1.pdf

Before I hook things up and fry the BIOS chip I want to get some questions answered and some things cleared up.

This level converter has a "A" side and a "B" side. What I think I understand at the moment is the "A" side gets the 3.3v pins and the "B" side gets the 1.8V.  Does this mean I also have to connect up a 3.3v power supply to VCCA and a 1.8v power supply to the VCCB on this logic level converter board?

Also I see the BIOS chip has a tolerance of "1.65 to 1.95V", couldn't I use a couple of AA or AAA batteries to power this chip?


texts:
This is regarding an integrator op amp design, the rate at which the input voltage charges the integrator's feedback capacitor is 150V/s. I am trying to justify the minimum feedback capacitor value before the bias current (or whatever else) affects the minimum current too much! This is my understanding so far, the op amp that I am using has a bias current of 30pA.

$$\frac{dV_{\text{out}}}{dt} = \frac{i_B}{-C_f} = \frac{30\text{pA}}{1\text{nF}} = 30\text{mV/s}$$

The maximum output voltage of the integrator is 5V, so using 150V/s and 30mV/s. How can I determine how much the bias current is influencing the the output?

The way that I think of it is 150/30=5V and 30mV/30=1mV, so the bias current causes a drift of 1mV. Is this correct? I imagined it to cause worse errors than this.

The resistor at the input is 230kohm. and the input current is about 120nA but I am not sure if these are factored into the error.

I found online another equation for the error, which is including the resistor.

$$\text{Error} = \text{bias current} \times R$$

Is this factored in as well?


texts:
My collegue here has two seperate boards linked by an SPI link. He just asked me: "So... you need to connect the grounds?" After I picked myself off the floor and answered very much in the affirmative, I wondered - ok, so how bad can this get? It's a much worse case than this question which had a common PSU.

In this case, the SPI bus slave had an open-drain MISO line (with a pull up to the PIC's Vcc). The other lines were SS, MOSI, CLK. No ground. The resulting communication state was odd to say the least. Mostly as MOSI alternatively connected and disconnected the grounds together, through the open-drain, at up to 500KHz! Not to mention different things happening when probes were connected. Or fingers for that matter.

I'd never seen the SPI transceiver on a PIC go gaga before, but this seemed to do it. The CLK is, well, odd now. It looks drunk. The PIC was on a demo board connected via USB to a PC.

If I asked myself though "What caused the damage" or "What was going on", I'd be stuck to give a proper answer. I guess the ground potentials can diverge wildly, even if the end device is sitting on a desk... Is it worse or better when a probe is connected? Who knows?

It begs the question, are other comms links better protected? RS-232 for instance. I've never seen a fried RS-232 transceiver and I've seen a few links where the ground got broken. Anyone shed more light?


texts: Why split the resistance on either side of an LED?

texts:
In the circuit below, is there any reason why we can't combine R1 and R2 into one 4 kΩ resistor in either location?

simulate this circuit – Schematic created using CircuitLab
I am reverse engineering a window controller board, which is no longer available.
The board has three input switches powered by an unregulated 24 V supply using this circuit to level-shift the inputs to the MCU's 3.3 V input pins. D2 and D3 represent an optoisolator (1/4 of LTV-846s). D1 is a visible LED that indicates when the input is pressed. R1 and R2 are 1/4 of a 8-resistor SOIC-16 SMD package (Bourns 4816P-1). Since there are three of these circuits, two of the resistors in the package are left unconnected.
Question 1: Is there any reason why this circuit would need two 2 kΩ resistors, instead of one 4 kΩ resistor? And why would they have used a SOIC-16 package for six resistors, instead of just three 0805's? The board has plenty of other discrete 0805 resistors.
I thought maybe it would be for power dissipation but unless I am making a stupid mistake, it's only dissipating 1 milliwatt which even small SMD resistors could handle.
I am going to use the same optoisolators (LTV-846s) in my new replacement board. Am I risking anything by replacing that resistor network chip with three 4 kΩ 0805 discrete resistors?
Question 2:
I would be tempted to get rid of the level-shifting circuit and just use the 3.3 V supply for the switches. If the 18 AWG wires to the switch are at most 100 ft, would it be a problem to use only 3.3 V? (I think that's about 1 ohm and 1 nF in 100 ft of wire). Would I be risking activating the input, from noise picked up from the wire?


texts: Batteries in parallel and series. Auto disconnect load while charging

texts:
New to designing circuits and PCBs. I'm working on a project and I can't seem to figure out how exactly how to do what I'm trying to do. I'm hoping one of you can give me a hand understanding the concept behind a few things I just can't seem to wrap my head around.

Basically, I'm designing a PCB for something that is battery powered but it's in a really tight space so it can't be removed for charging, it has to be charged in its spot. I have some 3.7v 18650 batteries that I am charging off of a TP4056. The batteries are constantly connected to their load and so I need to make a circuit that disconnects their load when the 5v is applied for charging. I'm told a MOSFET will do what I'm thinking but I can't seem to figure out exactly how.

The batteries are in groups of 3, 2 groups per each PCB. They're wired in series to get to 11.1v and in parallel with all the other groups to get me to the current I need. The plan is to charge each battery individually by being wired to the charger in parallel on a different PCB layer. I also threw in an LED as a charging indicator.

Ultimately this is a much larger design and this circuit has to be repeated 4 more times. (I need to fit this design in a pipe that is only 1.25" in diameter so it's about 7.5" total length after connecting (5) 18" PCBs.

Any advice is appreciated! Here's a picture of what I'm thinking will work:


texts:
I have designed LED Driver circuit using IRF540 and use PC817 Optocoupler for isolation.

However, the MOSFETs are heating too much after giving the PWM Signal.

One of my LED panels is 110W. What could be the reason for this?

The schematic is below, let me know if any modification in the circuit if required.


texts: How does this power inverter circuit work?

texts:
I'm looking for a power inverter for a DC voltage and I found this circuit on Wikipedia (I'm asking about the one on the bottom; ignore the one on top because it's the electromechanical equivalent of the one below.). I don't understand how it could possibly work, though. Isn't the negative terminal of the voltage source connected to the P-junctions, making reverse-biased connections to both transistors? And if that's the case, how do we get any current flow, much less a switch?

Here is the Wikipedia article that I found the circuit on.


texts: Getting weird resitance drops with an FSR and a raspi using a MCP30

texts:
I tried to create a weight detecting device, that detects when a heavy objects are placed on a table. Its supposed to work like this:

The raspi keeps checking the recistance on the force sensing resitor (fsr) using a mcp3008 ADC (not pictured)
Once the heavy object is placed on the table, the FSR detects the shift in resitance and adds an entry in the database along with the date, and the same thing happens if the object is removed again.

I managed to hook up the FSR and the MCP3008 using this graph :

simulate this circuit – Schematic created using CircuitLab

but after letting it run for a while  without putting any weight on it, this happened (10 minutes from left to right):

the voltage drops, resurfaces and then slowly swindles down again (notice the graph only goes to 1.48V)
when a heavy objects is placed on the FSR, it goes to about 1.58V, when its empty state is 1.68V, so this is a problem.

Does anybody have any idea, what could cause this? It seams to be stable for a few minutes but then it just drops.
Excel:

https://pastebin.com/raw/kjntnpin

Edit: i tried again but now the bahviour is even weirder (again, I didn't change the weight, I just let it sit for 20 minutes), it looks like a pattern and just seams to smooth out after a while, which is especially strange:

another stat, this time from 21:00PM to  8:30AM, with a heavy object on the FSR from 22:00 PM until 6:50


texts:
Please let me know if I make some type of technical mistake in terminology.  My topic revolves around USB connectors.

I have become aware of most of the issues surrounding the USB connector but there are some gray areas that I'd appreciate filling in by individuals that have more experience in the specifics.  If there is a source that will describe all the assumptions that I'm making below, please provide that link or title of the source.

Areas and what I'm not so sure of:
1.  I know that some types have 4 contacts and some types have 5 contacts. When there is only 4 is the missing one a power contact?  In the case of the other contacts, do they always follow a convention of use in the same order?
2.  Adapters must follow the corresponding corded connectors so that the flow-through will be compatible of course.  Are there any surprises to that rule?
3.  I believe that the contacts of USB connectors usually carry minimal voltage and amperage.  Is the voltage usually 12VDC or below, and what is the usual maximum for amperage that is conveyed before burn out?

My specific need is for a CORD that is approximately 2-3 feet and has a FEMALE USB MICRO- B connector on one end and MALE USB MICRO-B connector on the other end.  I have been searching the usual places that might be successful, but I'm not finding it.  I have even asked for help and coming up with answers that are not showing brilliance.  If not a single cord, then an ADAPTER that has a FEMALE USB TYPE-A connector to a MALE USB MICRO-B connector in the same adapter.  I have a cord that I can use with this adapter and then I'm all good.


texts: Lpc 43s50FET256 processor and its connections

texts: ı want to buy a nxp LPC43S50FET256 processor and ı made some research but I dont know whether lpc43s50 has already got bridge connections, ı also dont know for example whether ethernet is already connected or not I couldnt understand from the datasheet and there is not enough information about this processor so ı couldnt understand whether this is an  only  processor or are  there some other part which has already connected to processor for example ethernet and some other ports. Exactly what ı mean is whether this is a processor or microprocessor board


texts: Which way is better for powering a very remote sensor in this case?

texts:
I have to deliver power to a sensor which is 500 meters far away from the mains.  Sensor needs an 12V DC power supply, and the DC power supply needs to be powered from the mains. Battery is not an option and I have to use SMPS for the sensor. The power delivery(power cables to the sensor) will be indoors(inside a bridge). Sensor sinks less than 10mA current. No voltage regulation needed.

I have two choice:

Either I will power the DC supply in the vicinity of the mains, and send the power to the sensor which is 500 meters far away by using  twisted shielded cable. This is in Figure 2 below. Or I will power the  DC supply through 500 meters of AC cables and power the sensor at the vicinity of the DC supply. There will be no direct lightning strike ect. but EMI might occur.

simulate this circuit – Schematic created using CircuitLab

In terms of noise the closer the power supply to the sensor it is better because the sensor output quality is affected by the power supply noise.

As in Figure 2, I was planning to send the power to the sensor by 500m DC cable and was planning to install TVS diodes and caps at power supply rails before the sensor.

In terms of noise and EMI, is it better to use the wiring scheme in Figure 1 instead? If I use the 500 mains cable do I still need astra components for over voltage or noise? Which way requires less effort or caution?


texts:
I would like to make an electric heater. It will have a 20" Lasko Box fan at the back, pushing air passed the Kanthal A1 resistance wire.

I would like to use 120vac. It will dissipate 1000 watts, and draw 8.33 Amps, using a resistance of 14.4 Ω's

I will use Kanthal A1 resistance wire for the fact that Kanthal A1 resistance wire has a higher tempature threshold that NiChrome 60 resistance wire.

I'm aware of the length needed to hit a specific target resistance, to hit a specific target power output.

I would like to use a wood frame, and stainless steel eye bolts for the connections.

If I can't use wood, then what could I use for the box frame for the unit? Most space heaters use plastic casing, so I don't see why using a wood frame would be any different.

Is this possible?


texts: Running a CAN sample project on LPCXpresso LPC11C24

texts:
The LPC11C24 has a on-chip CAN transceiver and a section of ROM with CAN driver software. I am trying to run the can_onchip sample project on the LPCXpresso board. The CAN-High and CAN-Low lines are connected to an MCP2551 (because you need at least two nodes to test a CAN bus). I don't see any change on the CAN-High and CAN-Low lines and the CAN error callback function is called with error code 0x82, which is a BIT_0 error, meaning the bus is always in the HIGH state and it could not be pulled LOW/dominant. This makes me think there is a problem with the on-chip transceiver because any CAN node should be able to pull the bus LOW for a dominant bit.

The linker files used are the CAN version provided that reserve the ROM memory mapping for the CAN driver. The init and callback functions are being called, so I am relatively certain the drivers are working correctly.

Are there any other settings that need to be used to enable the on-chip transceiver?


texts: Why do automotive radar devices work only in 24 and 77-79 Ghz bands?

texts:
Commercial Automotive RADAR devices work on frequencies of 24 Ghz and 77 - 79 Ghz.

My question is only these frequency bands ? Why not say 40 Ghz ? What's so special about 24 Ghz and 77-79 GHz that commercial RADAR based Collision devices are available only in these bands ?


texts: Modifying El Wire driver for Brightness control

texts:
I have an El-Driver that has a potentiometer to control the brightness.

I would like to control the brightness with an Arduino, replacing the potentiometer.

Here is the schematic of the brightness control stage:

simulate this circuit – Schematic created using CircuitLab

I tried to replace the potentiometer with a low pass filter connected to a pwm pin on the Arduino but it didn't work.

Can someone direct me in the right direction?


texts: Usefulness of line EMI Filter on bench power supply

texts:
I have read this pdf file about EMI filters. I'm about to construct a variable bench power supply of 12V/5A.

Will there be any usefulness to add an EMI filter to the primary windings of the toroidal transformer? As I see it, as the transformer lowers voltage so does any EMI interference.


texts: Is there a practical limit to how fast a data transmission can be run over a DSUB9, SMD male to ribbon cable female? An engineer from a large connector manufacturer once told me that the insertion loss would be huge at higher speeds with a DSUB. Unfortunately I don't remember which speeds we were talking about.


texts:
I have built the instrumentation amp from the datasheet (http://www.ti.com/lit/ds/symlink/lm124-n.pdf, page 20) of the LM324. On the datasheet, they have built the amp with the 124, and I have simulated it and built it with the 324. However, on the datasheet, they state the gain of the amp should be 101. They calculate:

Vo = 1 + ( 2 * (feedback R of first amp stages) / adjustable gain resistor ) * (difference between inpunt voltage and ground)

However, I have found in my simulation and breadboard that the adjustable gain resistor has no effect. I always receive a gain of slightly larger than 2. I am not sure why the gain resistor does not work.

Attached is an image of the circuit I have simulated. I have tested the gain by inputting a DC bias into the "Vin" node; I have grounded the other input node. For instance, if I input 2VDC into the Vin, ground the other In Amp + terminal, Vout will be slightly larger than 4, for a gain of slightly greater than 2. If I adjust the gain resistor, this does not affect the gain. I am not sure why.

Can anyone explain why the gain resistor (R1 in the picture attached) does not work?


texts:
I'm working with the TMC2130 and I want to setup the stallGuard. The problem is that SG_Result in register DRV_Status is always 0. It doesn't matter with how much load the motor has to drive or how I set the sensitivity (SGT in register COOLCONF). I'm driving the motor in spreadCycle and the SPI is working properly.

The only register settings I make are:

toff = 3 (for spreadCylce)
tbl = 2 (for spreadCylce)
1/16 Microstep

I played with SGT but as already said, SG_Result is always 0. Am i doing something wrong or where could be the problem?


texts: On Samsung mobile phones, how does its USB host know when to charge the phone and when to power the connected device?

texts: How do mobile phones (Samsung, in particular) distinguish between being charged and having to power the connected USB device (i.e. flash memory stick)?


texts: What does a blue line indicate in Logisim?

texts: I know dark green indicates 0, bright green indicates 1, orange indicates incompatible bit width, but what does a blue line indicate?


texts: 12V lead acid battery instead of 11.1V LiPo?

texts:
I'm doing research on a remote control model ship. I have 11.1V LiPo batteries, but because of their weight and duration, larger batteries are considered better in this application (these batteries come were originally for RC airplanes, where lightness is key.)

My battery would go to an ESC, then to an electric motor. I have read that true, non-nominal voltages of LiPo batteries are higher, somewhere closer to 12.6V at peak. Because a 12V battery rating is also nominal, I understand it might be necessary to use a resistor or some other means of reducing voltage, but I do not really know much about how current flows, charge rating, cell count, etc.

The ESC being powered would be something like this, rated at 40A, and there would be a motor like this on the end, rated for 2s to 4s batteries. I'm assuming these ratings are just to guide people using standard material. Also, I actually have two ESCs and motors, but they are both plugged through the same receiver.

This would be the normal max power, from what I understand from this article:

power = voltage * current
480W = 11.1V battery * 40A ESC

Using this lawnmower battery for example, this would be the max power output (I think?):

420W = 12V battery * 35A battery rating

There could be something terribly wrong with this calculation, but it does look like it would work, while supplying a little less wattage, but likely allow a longer use period. Note that I used the amp rating of the battery for the second calculation, since it's lower than the ESC's max tolerance. Again, I could be mistaken. I've heard scary things about the power of 12V car batteries to solder metals together.

So I'm wondering, what arrangement would be needed to power such a system through something like a 12V lawn mower battery? Is that possible, or will this fry my ESCs, motors, and receiver?


texts:
I'm looking to a simple solution to keep the position of a robot. It has two DC motor and one wheel encoder for each. The encoder are incremental type.

I need to be able to get the current count of increment from an atmega.

I found some chip like the LM628/629 who will do great job, too great in fact, because it cost ~50$.

Do you know a dedicated IC that has only the count (in both direction) features for a wheel encoder, Or is it possible to make à simple one with an attiny ?


texts:
I am trying to control the current to a Raspberry Pi using a MOSFET and an ATtiny10. I am using a logic level MOSFET and it seems that the Pi needs about 250mA to turn on but it is only able to pull 120mA. My power source is 5V 3A. I have the circuit below. Any idea why I am unable to pull enough current to turn on?

NOTE: The answers below about breadboard causing Voltage and Current drops and the Pi rebooting due to over current draw are equally helpful. I accepted the answer that matched the Title question most.


texts: Most of the ultra low power micro-controllers need around 1 V to work. Are there micro-controllers which need much lower voltage, say < 0.5 V? Is it even theoretically possible?


texts: SMPS input impedance as function of frequency

texts:
I'm designing SMPSs with buck, boost and flyback topologies. I'm primarly using classical L-filter as the input filter.

It is important to make the output impedance of the input filter considerably lower than the input impedance of the SMPS because the SMPS's input impedance acts like a negative resistance that could otherwise lead to instability.

I was reading an application note made by TI (snva538) when I came across this picture.

What puzzles me is the shape of the input impedance of the SMPS as function of frequency.

I have used to just calculate the worst case impedance as a function of input voltage (the lowest input voltage) and use that value to decide if the output impedance of the input filter is satisfactory. Now the picture above indicates that this would not be enough and I should also calculate the worst case point and its value as function of frequency too.

So my question is what are the parameters and phenomenons affecting the input impedance of a SMPS as a function of frequency and how to mathematically deal with them?


texts:
I want to build a little voltage switch that switches on a buzzer and a relay when a certain voltage is reached. Please have a look at the schematic.

I use a trim potentiometer to set up the switch voltage so that it equals the zener voltage, in this case 3.3 volts. Then the Op Amp (741) switched to Vcc and drives the transistor (PN2222A) which switches on the 12V Relay and the buzzer. The Basis resistor is set in a way that I will have a Ic of around 150 mA.

So far so good.

My problem is that the Op Amp is not "ideal" and does not switch to 0V when the Voltage on the positive input is lower than the Zener voltage. There is about +2V, which is obviously enough to drive the transistor, so the relay/buzzer is always on.

There is also not a "hard switch" from 0 to Vcc, the Op Amp slowly increases the output voltage and then suddenly goes to Vcc.

I am aware of the DC offset problem, but how can I compensate it if I only have Vcc and 0V?

One other solution I found on the web was to put a feedback loop in. How do I dimension the feedback resistor?

These might be very basic questions, but I would appreciate your help.

Thanks in advance.


texts:
As the question says, I've been looking for the best way to bond strain gauges to Acrylonitrile butadiene styrene (ABS). It will be a circular cross section ABS piece. I'm not sure if this is an electronics question per se, but the application is in this field. If not, I'd appreciate it if someone were to point out which forum to ask in.

[Further explanation: to be used for a torsion testing machine as the sensitive element which measures the torque applied on the specimen, which would be some sort of bone substitute. The torque is low, around 2 Nm, which is why I need a material which exibits more strain than aluminium or the like. ]


texts:
I'am developing a datalogger with an stm32L496 + FreeRtos + FatFs. The data logger save data to a buffer and when is full, the buffer is saved in a file on an SDcard with the help of fatfs and the SDMMC+DMA.
When the working file is too big (15Mo), this file is moved to another directory. But sometimes, I have overrun because of the very long time of f_rename (500ms). I can increase the buffer to hide the issue but I don't understand why this function takes so much time.
Anybody has this issue?
I'm using Fatfs R0.12c with FAT32 format.
I have found that the code takes a long time when the function call "follow_path", when checking if the new file exist and when it call "dir_find" with the variable "path" empty. (So when this is the last segment).
In f_rename :
/* At FAT12/FAT16/FAT32 */
mem_cpy(buf, djo.dir + DIR_Attr, 21);
mem_cpy(&djn, &djo, sizeof (DIR));
res = follow_path(&djn, path_new); // the problematic function
if (res == FR_OK) {
  res = (djn.obj.sclust == djo.obj.sclust && djn.dptr == djo.dptr) ?
     FR_NO_FILE : FR_EXIST;
}

And in follow_path:
for (;;) {
  res = create_name(dp, &path);  // if after this function, path == ""
  if (res != FR_OK) break;
  res = dir_find(dp); // this function can takes 500ms even @ 50Mhz
  ns = dp->fn[NSFLAG];

The code isn't faster if I increase the clock speed so I think this is a software issue.
Any idea ?
[EDIT]
Ok, I tried in exFat and I have the same issue but inconsistently. It happened maybe every 20 or 30 rename.
I found here https://github.com/greiman/SdFat/issues/250 that the SDMMC of STM32 could be the problem. The guy says :

The SDMMC controller causes the SD to need to copy data from partial
filled flash pages so there are occasional writes with many
milliseconds of latency

I someone can try the rename function with an stm32 or another microcontroler to measure the latency, it would be a big help.


texts:
I'm trying to set up a relayed cooling mechanism for a mass spectrometer (i.e. cooling fans turn on when the MS exceeds a certain temperature). I have a 24V DC/25A power supply which converts 100-120V AC/12 A to 24V at multiple output leads, and that will be connected to several different instruments.

I just purchased 2 cooling fans - 12V DC/85mA - and would like to connect these in series to the power supply. However, when I connected them, they simply shuddered and did not turn on. Not to displace blame (I accept full accountability for the fans not working/not fully checking the specs), but it appears as though the company from whom I bought the fans did not specify that the nominal voltage range was about 10-14V.

The reason I bought the 12V fans specifically was because I thought the voltage would drop over each device - but perhaps not? I also want to make sure that I leave enough power for other small devices to operate off of the same supply.

So, what I would like to know if there is anything I can do? Should I simply return the fans for a 24V alternative? Or to save the cost of shipping, is there anything to make these fans work? I've read about using a diode to drop the voltage, but would that be the best option? It also appears to me as though a resistor would not do the trick.

Thanks very much in advance.

R


texts: Transistors and Diodes maximum current per size

texts:
As you can understand my knowledge in electronics is limited.
I am trying to find throughout the internet a way to find the maximum current I can put through a transistor or diode versus their size. Specifically in the region of nanometers and micrometers in VLSI projects. I can find a lot of info for diodes and transistors for PCBs but no info at all for applications in ICs. Any info (even with a big amount of error plus/minus, just a ballpark is fine) or a table I can find on the internet is also nice.
Thank you.


texts: Constructing a dc circuit with different input and output currents and voltages?

texts:
I am trying to answer this question (at the moment I am looking at part a) only as I still have not figured it out):

But what I do not understand is how you can change the input and output of dc? I undertand the principle behind transformers, but here I just don't know. I am sure it has to do with the other two terminals kept at zero volts, but here is my second problem: I can't see how you could keep something at zero volts without the current flowing down there, from higher to lower potential, and how these terminals at zero volts would be important in the construction of this circuit?

Thank you in advance :)


texts: How does load resistance affect RC low pass filter?

texts:
I am building a low pass filter. This is the equation I'm using to calculate what frequencies I want to pass though, but I have a couple questions on details.
$$
f_c = \frac{1}{2\pi RC}
$$
What goes into R? Does the resistance of the load (R2) affect R? Say R2 is fixed, are there any rules for selectring R1, like load matching?

simulate this circuit – Schematic created using CircuitLab


texts:
I find a lot of online tools to calculate the capacitance between two traces (or a trace and a plane) on opposite pcb layers. One such tool can be found here: http://chemandy.com/calculators/rectangular-capacitor-calculator.htm

However, I would like to calculate the capacitance between adjacent traces on the pcb. Something like this:

Has anyone an idea how to do this?

EDIT :
Imagine the following example:

Two tracks run parallel for 10 mm.
Each track is 0.2 mm wide.
The distance between both tracks is also 0.2 mm.
Copper thickness is about 20 µm.
Board thickness is 1.6 mm.
PCB material is standard FR4.
One track is signal, the other Gnd.
There are no other tracks in the area, nor any (Gnd-) planes.


texts: How does logic gates know if electricity is flowing?

texts:
I'm studing software development and I'm reading about logic gates, but from all the material that I've read, it never explained how the logic gates know if there is eletricity flowing through a gate or not.

Here is were it gets me. Let's suppose you have a Not Gate and it had no eletricity flowing through the input, so now it goes from no electricity flowing to eletricity flowing through the output.


texts: Identify the connector type from a picture

texts:
I am trying to create a PCB board that connects to multiple solenoid values .
The connector looks familiar but I am having a hard time finding out what kind of PCB connector to use for mating with the ones from the picture. Any help is appreciated .


texts: How can a BLDC motor respond to a specific dynamic load demand without changing the supply voltage?

texts:
Coming at BLDC motors from the theory side, my understanding has always been that they have a linear curve based on Kv, no-load current, and resistance, for a given applied voltage. Now the thing is, say they have a given "system load", like a propeller, that varies during the operation. So the load demands a certain RPM/torque combination at time A, and then a different one at time B. My understanding was that in order to achieve both combination A and B, it has to vary the supply voltage so that it's linear torque-speed curve intersects this operating point (provided this point lies below it's highest torque-speed curve).
What I can't seem to find is how this works without changing the supply voltage? If I use a PWM controller at 50% (but the supply voltage is the same), is the torque-speed curve really going to have a characteristic curve that responds as if the supply voltage was half? If not, how are these BLDC motors controller for dynamic applications where a specific torque and speed are needed at different times?


texts:
I'm looking for the power adapter for a dehumidifier (Zibro Clima D4) described in the specs as a CE approved 220-240 V, AC/DC 13 V/5A power adapter, which is shown in the manual and partially shown in picture.

However, I don't know if the two-pin socket is standard. It looks a little like a polarized IEC C7 connector, but it's square on both pin sides, measuring 14mm x 8mm, without the top edge lip, like this:

Which search terms do I need to use to find this online?


texts: Got an electric shock from a USB type C cable plugged to a laptop, how can I find the faulty thing?

texts:
I was about to charge my phone with the USB type C cable that was plugged to my laptop.
When I grabbed the cable I got a light electric shock (I think I touched the plastic case that covers the metal but I'm not sure).
When that happened, I wasn't even sure it was an electric shock or just something weird that just happened to my elbow.

So I went ahead and touched the cable again, this time on the metal part. The shock was really painful this time and got me tingling :(

So I decided to unplug the cable and not use it again.

But I would like to find out if that is a problem with the cable, the USB port, or the laptop (in a way I don't get hurt again, of course)


texts: How to set extra source and drain pins in PMOS power chip

texts:
I am using the FDS4685 chip here: https://www.onsemi.com/pub/Collateral/FDS4685-D.PDF

It has 4 drain and 3 source pins which I haven't seen before. I only need 1 source and 1 drain, how do I determine whether to connect these pins to ground or high to my 5V supply? Is it wrong to just keep it floating?


texts: I have an FPGA and a powerful ARM processor both support DDR3. I am an experienced designer for smaller more embedded designs with less powerful CPUs but this is my first rodeo with a powerful ARM and FPGAs. I am trying to figure out if I could share the DDR3 between the processor and FPGA so that I can use the memory as a way to communicate between the two. I need to shift large amounts of data between the two. Also, this would simplify(?) my design and save cost. I don't know what is the feasibility of this.


texts:
Background:

I am trying to figure out how a MOSFET operates for a college project. From what I know, it operates similarly to a BJT except for the following:

MOSFETs are voltage-controlled.
MOSFETs have a large input impedance.
Ideal for high-speed switching circuits.

Problem:

However, running a simulation in Multisim I get the following results:

According to the datasheet, when VGS is 5V, then RDS should be 50Ω. RDS is clearly above 50Ω in the simulation. Is there some misunderstanding from my side?


texts:
I am trying to simulate the circuit below. I am new to this software. How can I represent the toroidal coil named F and P in OrCad Pspice software?

Thanks


texts: Figuring out convenient footprint for given actual lead spacings

texts:
This a beginner question, but I couldn't find an answer in net. I want to place the following components call it from left to right Cap1, Cap2 and Res on a PCB:

As you see above I also mentioned the lead to lead spaces in mm.

So to associate footprints in PCB designer such as Altium I convert these spacing lengths to inch which becomes for 5, 6 and 12mm as: 0.19685, 0.23622 and 0.472441 inch in order.

But in the designer software the options for the caps are RAD-0.1, RAD-0.2, RAD-0.3, RAD-0.4 and the options for the resistors are AXIAL-0.1, AXIAL-0.2, AXIAL-0.3 and AXIAL-0.4.

Which footprints are convenient to use in my case for the Cap1, Cap2 and Res?


texts: Induction charging - What kind of calculations are involved?

texts:
I am designing a simple locking mechanism. The idea is that the locking mechanism cannot be locally powered. In other words, the key (size does not matter) and the lock must interact wirelessly. More importantly, the key must be able to provide the power to turn on the locking mechanism, and open it.

This isn't supposed to be a highly secure and strong system right now, it just needs to be a proof of concept. So, I have decided to hook up a servo to a micrcontroller to actuate the mechanism (probably an ATmega or ATTiny, probably something even lower powered). That's not important, anyway.

I would like to apply the same concept used in those commercially available induction charging stations to this project. I don't need to physically build it yet, but need to know how I can compute the specifics of the induction power transfer system required to power this device. You can consider the power consumption of the lock to be variable, so I'm essentially looking for the equations/concepts involved in this whole science of induction charging in generality.

I have tried searching for technical information, but Google is crowded with commercial fluff on why induction charging is cool and whatnot. I need to know how it works, and what I would need to apply it to any situation. Of course, if you have any suggestions for low power locking mechanisms, please add them to your answer.


texts: Using to diodes for OR'ing in OVP comparator

texts:
We have the following scenario: over-voltage protection IC (MAX18590/86) is placed in front of a buck regulator in order to protect (obviously) against excess-voltage at the input. Normally the over-voltage threshold (say 15V) is set by a resistor divider. When an over-voltage is detected the output is disconnected from the buck regulator. When the over-voltage condition is removed, normal operation is resumed after a 15ms blanking period.

A second fault condition is a failure of the buck regulator, most notably a short of the pass transistor. This would expose the remainder of the circuit to the unregulated input voltage (here 15V max).

I am wondering whether I could use a second voltage divider and two diodes to let the MAX18590 also disconnect the supply when the regulator output exceeds a certain level (say 3.6V) as shown in the schematic.

simulate this circuit – Schematic created using CircuitLab

Of course, when the regulator shorts and the supply is disconnected the fault condition vanishes and the supply is reconnected after the blanking period (15ms). Since a short of the pass-transistor is likely to persist, the protective device will toggle on and off forever with a period of 15ms.

The maximum leakage current into the OVLO pin is given as 100nA which should not load the resistive dividers significantly.

The resistor values given in the schematic are calculated without taking the diode forward drop into account. Is there actually much of a forward drop when only 100nA of forward current are present?

How much of an effect does the reverse-current of the diodes have?

Please comment on the idea in general and on the issue of diode drop in particular.


texts: How can we do AC analysis when CE amplifier input is zero?

texts: Hi everyone I would like to make AC analysis of an CE amplifier circuit. The circuit is some kind of LC oscillator. I would like to obtain small signal parameters but in oscillators AC input voltage is considered zero. How can I find those values. Thanks.


texts: Figuring out neutral and earth in a three phase connector?

texts:
I’m trying to check whether the earth and neutral is connected correctly in a 5 pin connector which has 3 pins for lines, one for neutral and one for the PE earth. 3L-N-PE type connector.

For some reason it is hard to reach and open the connector and verify the color codes. I want to verify which pin is neutral and which pin is earth to be sure if it was installed correctly. I can use a multimeter and have access to other single phase system plugs’ neutral and earth in the same room facility.

To make the question clear I draw the following:

As illustrated above I have access to pins of both three phase and single phase pins. Im sure about that the single phase’s pins neutral and earth are correct. But not sure whether for three phase the PE and neutral pins are mixed up.

Is there a method to verify whether the neutral and PE is wired correctly?


texts: Is a computer mouse considered an embedded system?

texts:
Can a computer mouse (optical) be considered an embedded device? Does it adhere to the definition of an embedded system?

Is there any good reference for how a computer mouse is made?


texts: How to convert 9 bit binary to BCD for 3 Seven Segment Displays

texts: I have been learning logic gates and binary so I made an 8-bit addition and subtraction calculator. When I add or subtract, the output is 9 LED's in regular binary. I have researched ways to convert Binary into BCD to be displayed to a seven segment display using a 7447 IC. I have checked other posts on Stack exchange which I found one but it didn't really answer my question. So the question is: Is there a simple way or Ic chip that I can use to convert 9 bits into BCD without worrying about the negative numbers? I do not want to use a microcontroller so I can do everything without programming. I have also heard something about using ROM which I don't know how to use or code with Assembly but I am still interested in that. I am not experienced at all with those sort of things. Any suggestions would be very most welcome.


texts: No output voltage on wiper when using pot as voltage divider

texts:
I've been trying to teach myself about potentiometers and how they can be used as voltage dividers. I bought some Alpha 10k linear pots to use in a really basic test circuit. I intended to connect the pot to my breadboard but unfortunately it doesn't fit so I've soldered some spare jumper wires to the pins of the pot.

In my circuit I have power from my Arduino Uno board (3.3v) connected to the leftmost pin on the pot and the other outer pin on the right is connected to ground. The middle pin (which I've assumed is the wiper) is connected to ground as well. When I measure the voltage between the two outer pins it's consistently about (3.2v) as I would expect but when I measure the output voltage between the wiper and ground it's either 0 or moves randomly between different values regardless of where I've turned the knob to.
 I'm wondering if I've misunderstood how the pot should be wired in this configuration or if it's just a case of bad soldering?


texts:
I am trying to measure capacitances using an Arduino UNO.

The C pin charges the capactitor through a 10K resistor (I have also tried 100K and 220), and the G pin discharges it.

V_A and V_B are measurement points across the 10K resistor.

The program does the following:

discharge_capacitor()
while v_b < 4.0V:
    t1 = get_time()
    pin C = HIGH
    dv_1 = v_b - v_a
    wait_a_bit()
    dv_2 = v_b - v_a
    pin C = LOW
    t2 = get_time()
    t = t2 - t1
    calc. q (q = I*t; I = V/R; V is the avg. of dv1 and dv2)
    total_charge += q
capacitance = total_charge / last_measured__v_b
print(capacitance)

I.e. it calculates the charge that goes into the capacitor.

It can measure capacitances of 1 and 3 uF with pretty high accuracy (for my purposes), but it outputs 0 nF when I'm trying to measure 470 uF caps. What could be the problem? Am I doing everything completely wrong?


texts:
/* Wait for the alarm flag */
while (!RTC_GetFlagStatus(RTC_FLAG_Alarm)); /* do polling or RTC alarm flag*/
RTC_GetTime(BINARY,&time);                 /*time structure must be equal to alarm time*/

lcd_clear();
lcd_print ("Alarm occured at");
set_cursor (0, 1);
sprintf(text, "time: %2dh%2dm%2ds ",time.hours,time.minutes,time.seconds);
lcd_print (text);

Hello all,
The above code section is from RTC example (STR9). This part gives a display of the time ( Hrs, minutes, seconds)

How is it possible to assign the minutes ( time.minutes) to a variable ( say 'y')

When i give

y = time.minutes;
sprintf(text, "Minutes :%04d",y);
lcd_print (text);

I dont get any values at y. It is always 0.

Do anyone know how to get that?


texts: Combine positive and negative power supply

texts: I have a DC Motor requiring 24V to run. Does connecting it to +12 and -12 work, as the voltage difference is 24V?


texts:
I've got a schematic that calls for an unspecified "NPN Negistor". From my understanding of the circuit, the NPN is an oscillator that generates two audio tones for testing. Here's the schematic:

I've got a drawer full of about a dozen flavors of NPNs, how on earth do I choose which one to use with such sketchy information?


texts:
If there is a Board that has 100 LED diodes however using different Diodes that have Different specs (Maximum Reverse Voltage, Max Wattage, Maximum drive current etc.) similar to a Quantum Board LED panel.

theoretically, how would you calculate the driver specs when determining what driver to use for the LED PCB board? and would the LED board even work?

FOR EXAMPLE lets say you are using this PCB board http://www.topledlight.com/red-copper-plate-pcb-circuit-board-100-spots-88mmx88mmx15mm-for-cree-xpe-xpe2-xpg-xpg2-xte-led_p1643.html

with 50 of these LEDs soldered onto them
https://www.cree.com/led-components/products/xlamp-leds-discrete/xlamp-xhp35-2

23 of these in PHOTO RED and 23 in PHOTO BLUE (these have different "Typical Forward Voltage"
https://www.cree.com/led-components/products/xlamp-leds-discrete/xlamp-xp-g3

and lastly 4 of these https://www.ledsupply.com/content/pdf/leds-semiled-uv_documentation.pdf

What Driver would you use, or how do you calculate the desired Driver output specs?

Will these LED Diodes work when soldered to the same board? will there be any type of bottle necking?(since the first diode listed is 13w and the others 6w)

I have a 20 Diode XP-G3 5000k and the driver that is compatible is a 100w PCB

The specs read

Power: 50W/100W
Model Name: CREE Xlamp XP-G3
Emitted Color:Cold White
Color Temperature:6000-6500K
DC Forward Voltage (VF): 30V-36Vdc
DC Forward Current (IF): 1500mA/3000mA
Maximum Pulse Voltage: 38Vdc
Maximum Pulse Current: 1700mA/3200mA
LED Viewing Angle: 115 degree
Size: (L)55*(W)40*(H)1.6mm
Usage:For flood light/high bay light/ House/Party/Architecture Decoration
The size is same as normal 100W LED,more birght and can instead of it.

and i chose this driver

https://www.ledsupply.com/power-supplies/mean-well-lpv-led-power-supply?gclid=CjwKCAjw2qHsBRAGEiwAMbPoDCfRLPvCJRTU6k42X-JfvpGUlxyPLmgIvWD7KKm0SthuQ_MGAroXFhoCD1UQAvD_BwE

Let me clarify. I am soldering a 100 diode quantum board using CREE LEDs and i want to know if the varying CREE Diodes will work properly when soldered to the same board (they are all 3.45 mm and fit on the board but that doesn't necessarily mean it will work efficiently.) I need to learn how to calculate and determine what driver to use and i was hoping someone here could help me.


texts:
I want to build a self driving handcart.
The car should be able move round about 80kg with a speed of 6km/h.
My idea is to use a 12 volt dc motor on the back axis for the drive and a servo motor on the front for the steering.

My question for the drive motor is can I use just anyone who has enough power and use pwm to slow them down, because there are motors with gears build in.

Or are this not enough information to provide a satisfying answer and should I construct the chassi first so that I know the wheel diameter.

Thx for your advice.


texts: USB interface while running micro at 2.5V

texts:
I'm doing a layout for someone who has asked for a USB interface on a micro that is running at 2.5V. As far as I can tell after researching this, you can't run USB down to 2.5V. So, I did a bit of  digging aorund for a level shifter and found this:

http://www.ti.com/lit/ds/symlink/txs0202.pdf

On first glance it looks like just what I need. I can run the high voltage side from a 3V3 reg off the USB 5V and the processor side can run off 2V5.

However, the data sheet says:

  The TXS0202 is a 2-bit voltage level translator optimised for use in
  Interchip USB (IC-USB) applications.

It has a diagram of it interfacing between a micro and an HD SIM card.

So, my questions are:

Is it right the USB will not work correcty running the micro at 2.5V?
Will the TXS0202 work if it's connected to a cabled interface on the high voltage side?
If point 2 is no, can I actually do what I need to? Are there simple devices that will level shift for cabled interfaces?

I would have throught there must be devices to do this, there must be scores of examples of micros running at less then 3V3 that have a USB interface. I cannot find anything other than three devices that all say they are for "inter chip" interfaces.  I appreciate inter chip doesn't specifically say on the same board, but the typcial application diagrams seem to imply that - or at least that's what I'm inferring.


texts:
I design a simple H bridge. The bridge is controlled by a PWM signal with a frequency of 125kHz.
The load is the LC resonance circuit. The maximum current is about 3A.
Everything is powered by a Li-poly 14.4V battery.
Dead-time is implemented by the control processor.
Are pull-up (R18, R28) and pull-down (R16, R26) resistors on the gate necessary?
Can I remove the resistors between the driver and the gate (R15, R17)?
Please verify the correctness, potential threats and suggestions.

TC4428 Datasheet
AOD603A Datasheet
regards


texts: 3.7v > 3.3v voltage stepdown with logic-driven on/off control [paused]

texts:
(PAUSED): This topic is currently on hold as I source necessary hardware.

I need to connect a Wi-Fi/RS232 module to a low-powered monitoring device, and for maximum portability, I'd like to power the Wi-Fi module - which runs off 3.3v at a peak of 250mA - from the 3.7v/1200mAh Li-Po battery built into the device itself.

To do so, I first need to drop the voltage from 3.7v to 3.3v in a way that can tolerate 250mA. I figure a series resistor should be sufficient, since I'm just running off a battery and not an unregulated power source - but what value resistance should I use?

In addition, the Wi-Fi module's own low power/standby state draws 8mA, which is relatively low but still noticeable, and would drain the battery over time. I've managed to unearth some undocumented info on how to tweak a couple of unused sense inputs that wire straight into the device's CPU (one via a 100Ω series resistor, the other via a 330Ω one) so they work as output lines, and I'd like to use one of these to switch power to the module on/off (possibly via a transistor or something...?). [I need to verify this, but I'm 99% sure the output before the resistors is standard 3.3v TTL.]

Everything needs to fit inside a compartment 50x54mm in size, approximately 4-5mm thick.

My non-SMD soldering skills are passable, but I've never worked with SMD components, so I need non-SMD solutions.

I also need an solution that radiates virtually zero RFI/EMI due to the electromagnetically sensitive medical environment the device will be used in, which won't tolerate even low levels of continuous EMI/RFI radiation particularly well (although short Wi-Fi bursts will be fine).


texts:
I'm trying to understand why open hardware is so much harder to come by than software.  I've tried looking around online and I couldn't find as satisfactory explanation.

I understand that hardware is so much easier to keep proprietary and so much harder (impossible) to reverse engineer (in the case of ICs, not PCBs), but why would that hold back open hardware initiatives?

Is it the cost of manufacturing?  Is it the lack of shared knowledge about hardware design?  Is it the complexity involved?

With the advent of FPGAs making it so easy to design hardware (although they themselves are proprietary as well), I would expect that open hardware would be taking off at a much faster rate than it has been.

I'm sorry if this is the wrong place to ask, but this has been perplexing me for about a year now and has made me wish I had taken Computer Science instead of Computer Engineering.


texts: Class AB amplifier becomes hotter, using more current and then becoming even hotter

texts:
In the circuit above a Class AB amplifier (this is one also called Class A+AB) can be seen with Q1 and Q3 used to get the current biasing voltage for Q2 and Q4. transistors Q2 and Q4 become hotter and hotter and requiring more and more current in the actual built circuit and in the end it reduces the output signal to 0. Are there easy changes that can be made to prevent this from happing?
The power supply gives 10Volt.

EDIT: As some of you noticed, there's was no resistor shown at the output in the figure above,  but it is added now.


texts: How to switch between two input lines based on a digital pulse

texts: How can I switch between two inputs based on a digital signal. I would like to have the Input 1 connected to the Output for the duration of the pulse and Input 2 connected to Output when the signal goes low.


texts: Are there any drawbacks to using Lead Free Solder Paste

texts: I understand from first hand experience that Lead Free solder is more difficult to use than leaded solder. But for a PCB, if I were to use Lead Free solder paste, are there any serious drawbacks using that instead of Lead solder paste? For my application, this is for hobby PCB application. I don't have a curing oven, so I planned on using my hot air station to melt the solder paste. Thanks.


texts:
I'm using the circuit schematic shown to control an LED driver while measuring its input power. Input voltages range between 120-300VAC, and the optotriac is controlled with a digital IO pin on an Arduino Uno. Triac and optotriac datasheets can be found in their hyperlinks. The input voltages are coming from a programmable AC Source (Adaptive Power FC205), so any anomalies on the waveforms seen are probably not due to issues with the source voltage.
When turning on the triac to power the LED driver we're noticing ripple waveforms at the point noted AO (see attached scope photo). I'm curious what could potentially fix this issue (figure adding a capacitor), but do not want to add a larger RC Snubber as this will go on a space-constrained PCB. This is my first time using Triacs, so I'm curious to see if anyone on this forum knows how to address the issue in a simple fashion.
Thanks for your help!


texts:
i'm thinking of making a project similar to the one you'll see in the picture lower: i want to control a remote control of a Velux with a Raspberry PI based on some data of temperature, rain, wind and so on.

The thing that i don't understand is what is the red board to the right (by sparkfun) that (i think) is giving power supply to the relays and the remote control (it needs 4.5V). Can you tell me what it is and what it does exactly?

Thank you in advance


texts:
Im currently trying to repair a board and I found this SOT23 component marked as A1⌐ (last symbol is a 7 but rotated 90 degrees to the left, I think).

In the board is marked as D15 so I assumed should be a diode, besides the "A1" mark, according what I have found on the net, is a BAW56 component that is a double diode.

But the problem is that the readings I get from de component out of the board, don't match with the expected for the device. (I have more than one of these on the board and all give me the same readings)

Obviously we may think that is a burned out component. but all of them burned out?, I don't think so.

So I believe is a different component. The rotated 7 is the thing that give me doubts. could it be a manufacturer code? if it is does anyone knows it?

I'll appreciate very much any thoughts on this.

As asked, here is a pic of section of the board where the component is located.

Is a series of active filters based on OP AMP. This is the last stage and takes as input the TANK2 signal (coming from a previous OP AMP circuit)


texts:
I looked at a friend's guitar amplifier which wasn't working, the problem was clearly (because it fell off) a broken IC (TDA2030AC).

After replacing it, the amplifier started working again but when I was taking some measurements I made a short-circuit and burned it.

When I replaced the TDA2030AC again, the sound was very soft and distorted. I checked the datasheet and the circuit is a bit different than the recommended implementation. Some resistor and capacitor values are different, but it's a dual-supply non-inverting configuration.

The strange thing is that while making contact between pins 2 and 3 with my fingers it sounds fine. And the same occurs with a resistor between about 100 to 500 kohms (see red line in my diagram). Even if that solution works, I would like to understand what's going on and if there is likely another part of the circuit damaged.

Here is the circuit (excluding the rectifier and pre-amplifier):

And this is the reference circuit: http://www.hestore.hu/files/TDA2030.pdf (Figure 13: typical amplifier with split power supply)

I would appreciate any clarifications, thanks.

EDIT: updated circuit diagram.


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also S11 is measured as amplifed S21 is measured as phase.We measure in a single frequency.
I can't see the logic in all of this.
if to someone it rings a bell to the method i'll be glad to have a description of this method so i could see the logic of it.
Thanks.


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Also stable 3v3 should be provided for MCU.
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If USB OTG cable connected - PMIC supply 3v3 for MCU and 5v to USB.

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I have a first current-generating circuit that produces an adjustable source/sink current (between + 10 mA and - 10 mA) with an output voltage range of ± 10 V.
I want to amplify this current by a fixed value to reach ± 100 mA as well as increase the maximum voltage output to ± 100 V so that it can deliver this current in typical impedance conditions.
Designing a custom circuit for this is an option but I'm surprised that I can't find any off-the-shelf component that can perform this.
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