![]() You only ever use common-source circuit configuration for switching in practice. Have a look at the Basics/Fade example in the IDE, or Analog/Fading. You can just use PWM direct from an Arduino pin (through a resistor). It will work with a BJT or MOSFET although with a standard (max. If you provide a Vgs thats too low you may fall below the plateau voltage and the device will conduct only a small fraction of its rated current. Speed control of DC motors works the same way. gate voltage - have a look at it and see the plateau. Datasheets have a graph of typical gate charge v. There is another voltage, the plateau voltage, at which most of the current switching happens - this is somewhere between Vthr and Vgs(on). ![]() Typical values for Vthr are much less than Vgs(on), about 1/4 of it in fact. Sometimes values for Rds(on) are given for both 4.5V and 10V, this is a logic-level device basically. The third difference is that the microcontroller attached to the base (or gate) and the transistors emitter (or source) must have a common ground. Non-logic level MOSFETs only have Rds(on) quoted for Vgs=10V. This means the on-resistance is guaranteed for logic level drive. Most Arduinos have a Vin pin that can be connected to bigger voltages, with 9 volts recommended and 12 volts a safe maximum that, according to some, should be generally. LED strip is usually run off 12 volts, Arduino works on 5 volts. ![]() That is when GPIO1 goes high RTS pin gets 5V. What I want to do is to be able to control that triggering using GPIO1 of the NodeMCU. The data flow from Rj12 Serial port is being triggered when RTS pin is connected to 5V pin of RJ12 port. Logic-level MOSFETs will have something like "Rds(on) =. Before we start connecting the Arduino to a LED strip, let’s deal with the power source. Hi I am trying to modify existing schematic for my home electric meter project. The datasheet tells you the on-resistance for a given Vgs - any voltage less than that is not guaranteed to turn it as fully on (or at all). If Vgs > Vgs(on), then it is fully on, where Vgs(on) is the value quoted in the datasheet under the Rds(on) entry. Ignore Vthr completely for switching applications, the way it works is this: More specifically it is usually quoted at a few 100 _micro_amps. I’d really appreciate any advice and enlightenment I am just a student seeking understanding and I don’t want to burn **another** Arduino.The threshold voltage is the voltage at which the device turns off, not on. Is my logic above correct? Am I gonna draw that much current? Would that fry my I/O pins? If no, why? If yes, what can I do to prevent that? Would throwing in a resistor to the Gate help (kinda like an RC circuit logic)? Am I being overly paranoid? Looking at page 2 of the MOSFET’s data sheet, the rise time is 58ns, and since I need to charge the gate by ~10-20nC, the current = dC/dt ~ 10/58 ~ 0.2A, higher than 40mA, hence I am killing the I/O pin. Now, while the MOSFET would draw practically nothing while in a static state, the dynamic state bothers me. From their data sheets, Arduino can only handle 40mA through I/O pins. Drain of the MOSFET is connected to the LEDs, source is grounded, and I use an Arduino’s digital pin to give either 5V or 0V to the Gate. But, according to spec, the Arduino can deliver 40mA. Therefore, we may very well not need a base-resistor. Here's the basic formula for calculating the base resistor: R (Us - 0.6)Hfe / Load Current, Where R base resistor of the transistor, Us Source or the trigger voltage to the base resistor, Hfe Forward current gain of the transistor (can be found from the datasheet of the BJT). I suspect thus, that the resistance is too high of the base-resistor. I am using an N-channel MOSFET (IRFZ24) to turn on a set of LEDs+other stuff (powered from 12V). But putting it in between the Arduino and the transistor, the transistor doesnt switch.
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