20
votes
Accepted
Is this a sensbile way to switch a 12V line with 3.3V logic
Lots of problems with your circuit:
T1 is used as a emitter follower. Its output will therefore be less than the 3.3 V input. Figure 700 mV for the B-E drop, and the maximum the gate of Q1 is ...
- 317k
15
votes
Accepted
ESP32: how to keep a pin high during deep sleep (RTC GPIO pull-ups are too weak)?
Well, sorry to revert my acceptance to the answer by Harry Svensson! And I shouldn't really be adding to a question that is 14 months old by now.
However I just found the perfect software solution, ...
- 5,587
15
votes
Accepted
How to drive 700mA LED cheaply?
XY problem.
Your best efficiency solution from a power and cost point of view to drive a 1A LED load is to use a LED driver IC. There are many to choose from; the Diodes Inc PAM2804 seems likely to ...
- 63.8k
14
votes
Accepted
Is it better to use a MOSFET with a gate driver IC or a MOSFET with a lower VGS,on?
which is best for fast switching do I need to use MOSFET driver IC such as ICL766 with IRFZ44n or is it better to use lower VGS MOSFET such as AO3400
You don't want fast switching to drive LED strips! ...
- 87.8k
12
votes
Accepted
Do I really need diodes to receive MIDI?
The diode is there to protect the opto-LED in the event of a reverse polarity connection.
The HF11L datasheet states that the absolute maximum reverse voltage for the emitter (meaning the IR emitter,...
- 188k
11
votes
Accepted
How is the esp8266 is able to generate 2.4 GHz wifi signals?
The radio contains a voltage controlled oscillator that is locked to an external reference oscillator using a phase locked loop (PLL). This results in a very precise high frequency signal for the ...
- 41.8k
11
votes
Low pass filter with two capacitors?
It's simply an AF (audio frequency) coupling capacitor, removing any DC that is on the signal.
- 39.4k
10
votes
Accepted
Low pass filter with two capacitors?
The first RC does indeed act as a low pass filter.
The second capacitor (the one on the right), combined with the load impedance presented by whatever is connected to the audio out, acts as a high ...
- 5,745
10
votes
How to drive 700mA LED cheaply?
I read about a method of limiting current using 2 transistors (schematic attached below).
All linear solutions, resistor or whatever, will have the same efficiency.
If you run the LED at 1A, it will ...
- 87.8k
10
votes
Controlling Relay using ESP8266 Module
Here's what your schematic is (left) and what I would use (right):
simulate this circuit – Schematic created using CircuitLab
The left schematic will act like a (sort of) current source, where ...
- 81.9k
9
votes
Accepted
ESP32 logic HIGH/LOW level voltage, not working?
The spec says that the input is guaranteed to be read as a Low below 0.25 Vdd, and as a High above 0.75 Vdd.
It does not specify where the actual switching threshold is - from the spec, we only ...
- 62k
9
votes
Trying to get (more) accurate readings from thermistor (electronics, math, and code inside)
The ESP8266 ADC is not really a very good one for instrumentation purposes. I believe it's not very linear (especially for voltages near 0V) and the internal reference voltage might be +/-10% or worse ...
8
votes
How to connect GPIO16 and RST of ESP8266?
The answer from A. Roy solved a similar problem for me. I'm prototyping a a circuit using a Nodemcu devkit board https://github.com/nodemcu/nodemcu-devkit-v1.0 with an ESP-12E. The board has an ...
- 81
8
votes
Accepted
FT232 stops being recognized after wiring ESP-01S on Ubuntu
The FT232RL chip data sheet says you can pull only up to 50mA from the internal 3.3V regulator for external purposes.
The ESP01-S module can take more than 50mA even when receiving a wireless packet.
...
- 196k
7
votes
Is there a way to trigger a 5V relay that is more robust than just feeding it with 5 V?
For critical systems, a failsafe circuit is used that has to be toggled continuously to activate the relay.
The GPIO pin is toggled in the main software loop (typically) after doing all the normal ...
- 3,801
7
votes
Is this a sensbile way to switch a 12V line with 3.3V logic
No this is probably not a sensible approach because the N channel MOSFET is wired as a source follower and cannot therefore produce a voltage output that is any greater than the gate drive voltage. In ...
- 501k
7
votes
Trying to get (more) accurate readings from thermistor (electronics, math, and code inside)
Unless you have a better than 1C temperature reference, I would not bother trying to get a higher absolute accuracy than what you get using nominal data sheet info. If you need a true high accuracy ...
- 3,616
7
votes
Accepted
Linear regulator doesn't keep the right voltage when connected to ESP8266
The datasheet states a the minimum Vin must meet 2 conditions, one of them being:
\$V_{in} >(V_r + 3\%) + V_{DROPOUT} \$
which for a 3.3V regulator becomes
\$V_{in} >(3.3V + 3\%) + V_{...
- 11.1k
7
votes
3.7v to 3.3v voltage regulator
A battery's voltage sags as it discharges and the LiPo type is no exception. A 3.7V LiPo battery falls to about 3.0V when fully discharged. You will want your project to continue operating over the ...
- 705
7
votes
ESP8266/ESP-12F gets damaged when powered by LDO (LD1117v33) every time
You NEED the capacitors, in particular the (recommended 10uF minimum) OUTPUT capacitor. A 10uF electrolytic- aluminum or tantalum (or a 22uF ceramic with a couple ohms in series) will do. The input ...
7
votes
How to measure voltage of a system with a different GND reference?
Measure the voltage of '?', and the voltage of GNDD, simultaneously, then subtract.
A way to do this with one channel rather than two is to measure the difference between ? and GNDD with a ...
- 184k
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
6
votes
ESP8266-12E MicroPython Unable to access REPL (Python prompt)
I was having a similar problem with a Wemos D1 mini board. Erasing and Flashing the firmware worked. However I was getting no REPL prompt, resetting was giving me garbage. I solved it by adding "-fm ...
- 61
6
votes
Saturation Points for Mosfets; driving gate with 3.3V output
The gate threshold voltage is pretty much irrelevant to most applications. Note that this is usually defined where the FET conducts only a little current. That's not useful when you want to use it ...
- 317k
6
votes
Accepted
ESP8266 - PULLUP resistor using Arduino code
No, GPIO12 and GPIO14 have internal pull-up resistors (see table below). If they are properly setup in software I would suggest looking at the output (relay control circuit). Since you provided no ...
- 366
6
votes
Scope says 59.9 Hz .. yet I can't measure turntable speed
Try 120Hz. The light varies with amplitude of the voltage and ignores polarity.
6
votes
Logic Level Shifter 24/12 V to 3.3 V
The simplest methods I can think of for getting your required signal levels are these:
simulate this circuit – Schematic created using CircuitLab
The safest way (for digital signals only) is ...
- 61k
6
votes
Accepted
ESP (ESP8266/ESP32) Mosfet switch problem
The IRF4905 is no-way suitable for such low voltage supplies. The \$V_{GS(THRESHOLD)}\$ value is typically about -3 volts and could be as high as -4 volts. At this sort of drive level, the MOSFET can ...
- 501k
5
votes
ESP8266 - is it used in real industry?
To answer your specific question, 'is there a better alternative for mass production', of course there is. That alternative is the same for any module, nothing I am about to say is specific to the ...
- 29.9k
5
votes
Accepted
How to connect GPIO16 and RST of ESP8266?
Most of the people face the problem while connecting them. The issue is that GPIO16 provides a strong HIGH during deepSleep and your external reset from Serial-TTL is fighting to make a reset, but ...
- 76
Only top scored, non community-wiki answers of a minimum length are eligible