When selecting a fet, choose one that is "full on" in the 2V range.
Transistors will work with the typical AtMega328 based Uno, Nano and Mega. But, if you have anything other than an AVR based processor, you will typically not have enough pin output current to drive your specific load. Since your saying it’s 3.3 volts, it’s probably an ARM based part so there you’ll need to use a Mosfet.
I'm trying to operate relay 24v 3.0w using arduino at 3.3v, as my 3.3v circuit is going to drive a 24v relay i would say I'm going to amplify, am I correct?
I tried to learn by google around and draw two options that sounds like should work, using BD139 and BD140 transistor
In option A I'm driving transistor directly from Arduino data pin to turn ON/OFF relay using a NPN transistor Q1
In option B I'm driving a BD140 PNP Q3 transistor using a small BC series NPN transistor as in schematic Q2
If you think that should work i want to know what should be resistor values for both options and how are you calculating. If you think its not a good approach and i should use some MOSFET then please let me know I will get back with more options with MOSFET.
R4 isn't really needed. It can improve the turn-off time, if the circuit is driven from a signle ended input, but in this case the MCU output has a push-pull output, which will connect R2 to 0V, when it's low. If you want to include it, use 10k.
R4 isn't really needed. It can improve the turn-off time, if the circuit is driven from a signle ended input, but in this case the MCU output has a push-pull output, which will connect R2 to 0V, when it's low. If you want to include it, use 10k.
I would include R4, since the MCU output will probably default to high-impedance until your program configures it.
R4 is there to prevent any collector-base leakage current from turning on the transistor when the base drive is in this high-Z state. In practice this leakage is probably not high enough to cause problems, but R4 is a good precaution. Yes, 10K (or 100K) would be an appropriate value.
Transistors will work with the typical AtMega328 based Uno, Nano and Mega. But, if you have anything other than an AVR based processor, you will typically not have enough pin output current to drive your specific load. Since your saying it’s 3.3 volts, it’s probably an ARM based part so there you’ll need to use a Mosfet.A MOSFET is a transistor.
Used Crydom brand units that still have lots of life left in them can be found used on Ebay. Stay away from the Fotek brand on Ebay/Amazon/AliExpress. They are proven to be dangerous junk. See Big Clive, on YouTube.
Transistors will work with the typical AtMega328 based Uno, Nano and Mega. But, if you have anything other than an AVR based processor, you will typically not have enough pin output current to drive your specific load. Since your saying it’s 3.3 volts, it’s probably an ARM based part so there you’ll need to use a Mosfet.A MOSFET is a transistor.You know perfectly well that in English, when someone says “transistor” in the context of discrete components, they mean a BJT. Because originally, BJTs were the only kind, so “transistor” was synonymous. (And for a long time after that, BJTs were still the overwhelmingly dominant type.) And because of that, when we mean any other kind, like a MOSFET, we name it specifically.
The only context where the word “transistor” means a MOSFET by default is when listing the transistor count in CPUs and GPUs.
OP's relay is a piggy on power at 3W (125mA) coil. It's a lot of heat, you would use PWM to reduce holding current.
A single transistor you have to drive a bit hard, for an MCU output pin. I use BC817 for smaller relays. hFE is 40 at 500mA and VCE sat 1.0V
I haven't seen much for medium-high power 3.3V logic-level SMD mosfets, what parts are popular?
OP's relay is a piggy on power at 3W (125mA) coil. It's a lot of heat, you would use PWM to reduce holding current.
A single transistor you have to drive a bit hard, for an MCU output pin. I use BC817 for smaller relays. hFE is 40 at 500mA and VCE sat 1.0V
I haven't seen much for medium-high power 3.3V logic-level SMD mosfets, what parts are popular?
A word of caution for using potentiometers on breadboards:
Before you apply voltage, make sure that you can not create a short when the wiper is in any of the two extreme positions. If too much current flows through a potentiometer then the magic smoke is released and the resistance track gets damaged, and it won't work properly after that anymore.
The general rule of thumb is select RB so IB = IC/10.
The BC337 has a minimum gain of 100, at 100mA and 60 at 300mA, when the voltage drop across the collector and emitter is only 1V.
I'd aim for a base current of around 3mA