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26 votes

How to convert a digital signal from 5V to 24V?

Converting to a "24 V signal" is missing the point. The real problem is driving a 24 V relay from a 5 V digital signal. Fortunately, that is easy. Here is one way: You didn't say how much coil ...
20 votes
Accepted

Is it a good idea to connect a line buffer to ground?

You should always tie unused inputs to a valid logic level. That could be tied to GND or to the VDD voltage rail. Never leave unused inputs floating in that it can cause excessive power dissipation in ...
14 votes

How to drive 1080p with only 540 pins?

Typically there are long skinny driver chips for row and column. They may be on the outside COF (Chip-On-Flex) or inside COG (Chip-On-Glass construction) the panel itself. Here's an HD TV panel from ...
13 votes

Why are USB devices slower than 480 MBit/s

This is a very old topic, but it has no answer yet. This is my attempt: Why are today's implementations not capable of streaming at 53 MB/s? The calculations are nearly fine, but you are ...
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13 votes

Resistors getting hot in this MOSFET driver circuit

Here is your circuit being discussed: R3 and R5 should not be getting "hot". Do the math. Even if Q1 were a perfect switch, there would only be 5 V across R3. (5 V)2(1 kΩ) = 25 mW. Unless ...
13 votes
Accepted

Does a MAX485 need decoupling capacitors?

Yes. All almost ICs need decoupling capacitors. Devices such as these '485 drivers especially need them due to the current surges the device experiences when switching the signal states due to the low ...
13 votes
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Is it OK to use internal pull-down as part of voltage divider?

Schematics like the one that you show should be regarded as simplified schematics - the actual implementation is likely more complex. Anything that is not specified in the tables, graphs or text --- ...
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12 votes

Resistors getting hot in this MOSFET driver circuit

Figure 1. When Q1 is off both Q2 and Q3 are forward biased (green) and will turn on. The result will be shoot-through the two transistors (red). If the supply voltage doesn't collapse (1) will be at ...
  • 163k
10 votes
Accepted

Why is a resistor put before the gate of a transistor?

The reasons are different depending on if it is a BJT or a MOSFET. The effect, though, is the same - it's there to reduce current and protect the IO pins on the controller that are driving the ...
  • 55.6k
10 votes
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How does a Line Driver actually works?

A line driver is simply a buffer. What you put in one end comes out the other. However, it is typically able to sink and source much more current than, say, a normal GPIO pin on an MCU. The increased ...
  • 55.6k
10 votes
Accepted

How to interpret the stepper motor voltage requirement?

There are 2 approaches to driving a stepper motor. The simplest is just to connect DC to each winding in turn, via switches (FETs, driver ICs). And in that case, use 4.8V (5V - switch losses) as you ...
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10 votes
Accepted

I²C bus buffer vs extender P82B715 vs. P82B96

82B715 is a rather older device, with a limited specific function: It increases the bus current 10x. It does not however improve the threshold noise immunity (threshold levels remain the same). We ...
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10 votes
Accepted

Is this circuit linear or not?

\$R_{\theta JA}\$ is one small part of the story. The main part of the story is \$R_{\theta JC}\$ (at 1.5 °C/W), because this is the junction-to-case thermal resistance and it adds to the heatsink ...
  • 396k
10 votes

Is it a good idea to connect a line buffer to ground?

With any CMOS logic IC, you MUST connect unused logic inputs to a known logic level. You may connect unused inputs to either High or Low, whicever is convenient (or whichever is necessary to make the ...
10 votes
Accepted

When do you need buffers/drivers on buses in a microprocessor design?

Large is when the processor cannot drive the various signals properly and that comes down to a number of things but primarily it is the number of devices on the bus. They all present a load to the ...
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10 votes
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How Does an Adjustable Transistor Size CMOS Driver Work?

The approach to do this is alluded to in the datasheet snippet you linked, which mentions "fingers", or separate parallel gates in a wide MOSFET that forms the output driver. These fingers ...
  • 14.8k
9 votes

Make an opamp go rail-to-rail on a voltage higher than opamp supply

If the only problem is that the amplifier stage you made inverts the signal, just flip the inputs of the opamp around to compensate. For another approach, use a different opamp, or do the whole thing ...
9 votes
Accepted

MOSFET not turning off

Even though this a a 'simple' circuit there are still lots of things that can go wrong. Finding a fault is quite an art. Let's start by breaking the circuit into two parts. The BJT switch and the ...
  • 18.6k
9 votes
Accepted

Russian к2лн641 VFD (Vacuum Fluorescent Display) driver pin out help

I'm Russian, so I'll help you out with this one. First of all, the first link google gives when I search for that is the museum of soviet electronics. Interesting choice of parts haha. Secondly, this ...
  • 3,348
8 votes

What does 'L' mean in the name of motor driver IC "L293D"?

Not much. It's just a part number, originally from the European company SGS-Ates. Perhaps at one time it indicated "Linear" (most of the chips SGS made were bipolar linear and started with an L or ...
8 votes

Resistors getting hot in this MOSFET driver circuit

There's a continuous base current path for both Q2 and Q3 when Q1 does not conduct. You can easily expect continuous 200mA current through them from your +5V. That's about 1W dissipation which well ...
  • 21.8k
8 votes
Accepted

Trying to increase amperage of Arduino Uno digital pin (20mA) to control a cabinet lock that is rated at 12v / 2A

simulate this circuit – Schematic created using CircuitLab All you need is a Logic Level MOSFET. I use N-channel AOD5xx to sink current thru a load. 508, 510, 514, any would work well and can ...
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8 votes
Accepted

Relay coil fast demagnetisation

The higher voltage you allow the coil to spike at, the faster the current will turn off. Something, usually a transistor, is driving the inductive load. You have to keep the maximum spike voltage ...
  • 145k
7 votes

How does a Line Driver actually works?

I'm not sure what you mean by "how it works". The datasheet tells you pretty much everything you need to actually use the part, though NXP does tend to be a bit sparse on internal details. Anyways, ...
  • 31.6k
7 votes
Accepted

LED glowing when the driver's ground is cut off

What's Happening: Internal to the module, there are some diodes to protect the inputs. Typically these are ESD diodes, but they will conduct DC current if you reverse bias them. It's not a strong ...
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7 votes

How to drive a linear actuator in both directions

Use an H-bridge. It is cheap and straightforward to build. http://www.bristolwatch.com/k150/port4.htm I use this for high current switching: http://www.bristolwatch.com/k150/pics1/mosfet_hb2.png ...
7 votes

Resonant Solenoid Drivers

In no case would a coil driven at resonance be better than one driven with DC. This is presuming that the job of the coil is to make a magnetic field, and that this requirement exists regardless of ...
7 votes
Accepted

Driving a 6V relay from an 3.3v GIO pin of Raspberry PI3

The item you linked in your question is a logic level converter and so this would probably be unsuitable as it wouldn't be designed to work with currents around 100 mA. The simplest implementation I ...
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