22 votes
Accepted

Tie all unused GPIO to GND?

The PIC24FJ64GA004 Datasheet specifies the general practice for unused I/Os: 2.8 Unused I/Os Unused I/O pins should be configured as outputs and driven to a logic low state. Alternatively, connect a ...
Velvet's user avatar
  • 4,299
17 votes

Tie all unused GPIO to GND?

Apart from the valid reasons given in answers, if you are developing a circuit board, it's always useful to have spare IO brought out to a small but convenient test point just in case you suddenly ...
Andy aka's user avatar
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10 votes

Tie all unused GPIO to GND?

It might be relevant, but it depends. And you already talk about two scenarios, you mention tying unused IO pins to ground (without mentioning any resistors so reader may assume direct connection), ...
Justme's user avatar
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6 votes
Accepted

I obliterated a ceramic SMD, how to find out what piece it is?

It appears to be one of the load capacitances of the crystal which appears to be "removed": That and the one to its right have the same capacitance. Carefully remove the other capacitor to ...
Rohat Kılıç's user avatar
5 votes

Tie all unused GPIO to GND?

It is generally good practice to tie unused GPIO (CMOS) inputs to ground, and outputs to ground or vcc through some resistor value that would otherwise not cause excessive pin currents beyond rated ...
citizen's user avatar
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5 votes

Tie all unused GPIO to GND?

Look at Microchip's AN1416 app note: https://ww1.microchip.com/downloads/en/Appnotes/90001416a.pdf#page=15 under Hardware Design. Unused Port Pins By default, PIC microcontroller I/O pins power up as ...
fivejeez's user avatar
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5 votes

I obliterated a ceramic SMD, how to find out what piece it is?

I am 99% sure that if you slap down the least expensive/most popular HC49/U 16MHz crystal and an appropriate size NP0 22pF capacitor it will work fine. There is nothing that requires extreme precision ...
Spehro Pefhany's user avatar
5 votes
Accepted

LEDs forward voltage at minimum brightness

The problem with voltage-driving LEDs, which is what you are effectively doing, is that the LED forward voltage varies with temperature. This could explain your anomolous voltage readings, which ...
Neil_UK's user avatar
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5 votes

How to solve for \$i\$ using superposition?

First off, redraw the schematic. In fact, you should get into the practice of redrawing every schematic. Even those that already look good. Just do it. And do it every time. The practice is worth its ...
periblepsis's user avatar
  • 8,940
4 votes

I obliterated a ceramic SMD, how to find out what piece it is?

These are loading capacitors for the crystal. Apparently the crystal has been ripped away as well. So the more tricky part is probably finding the right crystal. What I would try to do: Find out what ...
feynman's user avatar
  • 3,365
4 votes

Using resistor network instead of regular resistors

It depends on the exact topology of your array, but it's generally possible. Supposing you have an IC configured as follows: simulate this circuit – Schematic created using CircuitLab Assuming ...
nanofarad's user avatar
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3 votes

Using resistor network instead of regular resistors

Yes it is possible, and commonly done in commercial equipment. There are different types of resistor arrays, some have one pin of each resistor available, and the other end of the resistors are all ...
GodJihyo's user avatar
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3 votes

Manufacturer of electronic components

As clearly printed on the part, it would appear this was made by TDK.
Hearth's user avatar
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3 votes

Tie all unused GPIO to GND?

Setting all the unused gpio as outputs and typing to ground (can use 0 ohm resistors if the design is mature and firmware is stable) also has the benefit of lowering the IC's ground impedance which is ...
CharlesG's user avatar
3 votes

How to determine equivalent resistance between terminals?

What kink of symmetry I can use to get the result? I think I have to redrew a circuit but how? The top array of 3 resistors is identical to the lower array of 3 resistors AND they connect to three ...
Andy aka's user avatar
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3 votes
Accepted

How to solve for \$i\$ using superposition?

The simplest but most laborious method is the Superposition principle,Below I examine the various cases (see photo):
Franc's user avatar
  • 1,241
2 votes
Accepted

What is the error in this circuit design?

If my first comment above is correct and the resistors are being shorted, the coin battery is being connected directly to each LED, (with no current limiting). The enabled LED will draw a high current ...
Nedd's user avatar
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2 votes

LEDs forward voltage at minimum brightness

You have an MCU -- use your microcontroller as a voltage doubler or tripler. Since you only want to ensure the dimmest illumination, not brightness, this is perfect. Dave Jones of EEVblog fame has an ...
MicroservicesOnDDD's user avatar
2 votes
Accepted

Braking resistor getting hot due to constant DC voltage on terminals PBe and PB on ATV320

Low power 3 phase drives normally rectify the AC supply and filter with capacitors to get DC voltage for the output bridge (IGBT) for the motor. Capacitors bank are usually in serial groups and have a ...
Bravale's user avatar
  • 1,577
2 votes

Using resistor network instead of regular resistors

You can do this if you use networks that are appropriately rated (watch the power rating and allow adequate safety margin for your environment extremes and reliability requirements). It's a very ...
Spehro Pefhany's user avatar
2 votes

Can lowering resistor temperature reduce thermal/Johnson's noise?

rms voltage noise of a resistor is: $$ E_t = \sqrt{4\; k\; T\; R\; \Delta f} $$ Where: \$ k = \$ Boltzmann's constant \$ = 1.38e-23 \; W\cdot sec/°K\$ \$ T = \$ temperature in °K \$ R = \$ resistance ...
qrk's user avatar
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2 votes

I obliterated a ceramic SMD, how to find out what piece it is?

Unfortunately the exact value of that capacitor cannot be known. Fortunately, that cap was a crystal loading capacitor for the Atmel CPU as shown. As mentioned in another answer, you can remove the ...
Justme's user avatar
  • 149k
2 votes

LEDs forward voltage at minimum brightness

As Neil_UK said in his comment, you can keep the two LEDs in series with no resistor (or a zero ohm jumper instead of a resistor) or 10 ohms, it won't make much difference. 5V is already less than the ...
Fredled's user avatar
  • 2,330
2 votes
Accepted

How would I decide on the best LED intensity for TCS3200 sensor

Basics Cool project! You should know about potentiometers So, if you should really go with resistors, you'd honestly just buy an adjustable resistor, a so-called potentiometer (the ones meant for &...
Marcus Müller's user avatar
1 vote

NPN transistor as a switch configuration

The rule of thumb for transistor switches is to make the base current 1/10th of the collector current to force it into saturation. This would put you at around $$ R1 = \frac{V_{in}-V_{BE}}{I_B} = \...
GodJihyo's user avatar
  • 23.4k
1 vote

Manufacturer of electronic components

It appears to be a hybrid circuit, made by TDK and probably custom for the application. That kind of construction was kind of a fad with Japanese designers many years ago, just before SMT was widely ...
Spehro Pefhany's user avatar
1 vote
Accepted

MOC3021M + JST16A-600B TRIAC Circuit problem: Resistor blowing up

R4 and R6 are connected directly to L, so when you switch on the gate through the opto coupler, that voltage will be applied and many current will flow until next zero voltage cross. See modification ...
Bravale's user avatar
  • 1,577
1 vote

How to determine equivalent resistance between terminals?

This is an alternative solution using two Wye-Delta conversions. Due to part of the circuit being symmetric (excluding those two horizontal \$5 \space \mathrm{\Omega}\$ and \$2 \space \mathrm{\Omega}\$...
Dirceu Rodrigues Jr's user avatar
1 vote

Tie all unused GPIO to GND?

I'm late to the party, but I want to provide some additional comments. It's helpful when considering ESD and EMI effects to go back to the basics of circuit analysis or maybe even electromagnetics. ...
Ryan's user avatar
  • 2,364
1 vote

Problem Using Resistors in LTSpice

First off, choose a device for the LED. I picked a model at random that was in LTSpice's model library (right-click on D1). You will need to supply a model for the LED you are actually using. Download ...
qrk's user avatar
  • 9,619

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