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 ...
- 317k
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 ...
- 58.3k
16
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 forgetting ...
- 43.1k
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 ...
- 317k
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 ...
- 58.3k
13
votes
Accepted
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 --- ...
- 3,321
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 ...
- 188k
12
votes
Accepted
Why put capacitors to ground on a driver's outputs?
The chip is intended to drive automotive loads in automotive environments, mainly lamps but also other resistive, inductive and capacitive loads.
In such applications there are simple wires going ...
- 195k
11
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 ...
- 22.9k
11
votes
Accepted
What vendors make anti-counterfeit drivers for USB-UART ICs?
Prolific did, we ended up holding some "PL2302" USB-RS232 cables that were "Linux only" around 2010 some time, the windows driver didn't try to break the chip.
I recall Silicon ...
- 40.4k
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 ...
- 500k
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 ...
- 62k
10
votes
Accepted
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 ...
- 21.4k
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 ...
- 3,783
9
votes
Transistor Driver - what is the purpose of Q2 on the included schematic?
Q2 is not simply a B-E diode, it is an emitter follower.
Without Q2, R1 pulls up with about 10mA, driving the load rather modestly. This is okay for small loads, like logic-level inputs, or even ...
- 53.1k
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 ...
- 3,741
8
votes
Accepted
Output drive vs. absolute max output current
On page one, the datasheet is telling you that the output can supply 4mA and still respect VOH(min). In other words, it can supply 4mA and still provide an output voltage that will be recognized as a ...
- 29.9k
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 ...
- 184k
8
votes
What vendors make anti-counterfeit drivers for USB-UART ICs?
The question is certainly of historical interest but of little current relevance. It’s troublesome to design for anything but standard USB class - CDC. Even if say FTDI may not be offering a chip for ...
8
votes
RS485 Internal circuit
The internal circuits are not relevant and each chip or manufacturer may implement them in any way they see fit, as long as the chip meets RS-485 specifications or works better that required.
...
- 195k
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 ...
- 317k
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 ...
- 500k
7
votes
How to convert a digital signal from 5V to 24V?
The circuit in your schematic will work fine except that the relay coil should be connected to the output and to +24, not the output and GND. Pin 9 is not shown on your schematic and must, of course, ...
7
votes
Ohms law and LED driver efficiency? How can this possible be true?
He's trying to sell you something that consumes > 30 W as a "30 W driver", whereas it actually can only supply less than 30 W. The ratio between power that goes in and goes out is called the ...
- 110k
7
votes
Accepted
Driving MOSFET from MCU with BJT
D1 isolates the base drive of Q2 from the emitter output, so when Q1 turns on it pulls the base of Q2 to -0.7V relative to the emitter and turns it off before pulling the output down.
Yes, you could ...
7
votes
Simple LED driver, transistor and GPIO
BJT's as switches aren't complicated.
One input is the value of your power supply voltage -- call it \$V_\text{CC}\$. Another input is the desired operating current of the LED -- call it \$I_\text{...
- 79.7k
7
votes
Transistor Driver - what is the purpose of Q2 on the included schematic?
Compare the performance with and without Q2 (100kHz with 0.6Ω resistive load):
Without Q2 (specifically with Q2 connected as a diode) there is only the 1k resistor to charge the gate capacitance. So ...
7
votes
Accepted
MOSFET driver: Totem Pole or NPN Self-Biasing Turn-Off Circuit
A couple of minutes on Mouser yielded these through-hole drivers which should work in your application:
UC3705 from Texas Instruments
MIC4426 from Microchip
In the spirit of the question, I think ...
- 61k
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