I want to turn on / off vibrating motor with Arduino. I am able to send HIGH and LOW signal on Digital pin, but vibrating motor will not start as it requires 500 mAmp.
I can't use relay as relay will be slow and I need to turn on / off several times in second.
Can it be done by using transistor or anything else? I can give external power to vibrator, but I would like to know how I can send signal on / off so that it can only start when Arduino is giving it signal to turn on.
MOSFET is metal oxide semiconductor field effect transistor.
These are very efficient when completely OFF or completely ON but will make heat in between. When used to control a lot of current, halfway open will smoke the FET.
You can get 10 for $2.36 plus the same $2.50 shipping.
I have some of these from a few years ago, they work and so far I haven't zapped any but watch out as MOSFETs are vulnerable to static.
IRLZ44N should switch power between the circuit and ground, not power. Connect the power and use the FET to allow it to flow to ground for this N type FET. Think of how your sink has a tap that you open to let water already in the pipes drain into the sink (like ground).
IRLZ44N are logic-level FETs, they turn fully ON with 2 or 3 volts control signal, 5V works great. Put a 220 Ohm resistor between the Arduino pin and FET gate since a FET has capacitance (field effect) to fill that could pull more pin current than is good. The resistor is to keep the AVR pin safe.
These things are cheap. Get extra, you can always sell some, the shipping cost and time have a value so you don't want to order twice. I spent almost $10 in 2014 or 2015 to get 60 pieces, worked out to 14.5 cents each.
PS -- almost forgot, they are good to over 12A current according to the spec. I have only switched about 2A feeding 12V led strips. The suckers will last "forever" with that little load.
GoForSmoke gave you a great answer and the nice part you do not need a diode as the MOSFET is avalanche rated. Look at the data sheet, Controlling 500 mAmp Vibrating Motor with Arduino - Project Guidance - Arduino Forum the Maximum Avalanche Energy
Vs. Drain Current shows it all. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
500mA is the upper end of ULN28xx Darlington Array chip, what might have gotten used in the 90's.
Yes the IRLZ44N has a protection diode but note that gate to source voltage is +/- 16V. What I was looking for that I have seen elsewhere is that just 20V across those pins is FET-fini.
Which vibrating motor.
The small ones draw something like 100mA, which is well within the range of a darlington chip or 2N2222.
No need to throw a TO-220 mosfet at that.
Leo..
GoForSmoke:
And the Darlingtons are pretty wastey...
That might be a good thing if you run a 3.7volt vibrating motor on a 5volt supply.
As always, good advice can only be given if all the details are known.
Post#0: "vibrating motor with Arduino". Two unspecified things in that snippet.
Leo..
Wawa:
That might be a good thing if you run a 3.7volt vibrating motor on a 5volt supply.
MOSFET + analogWrite(pin, 189) has the same effect.
GoForSmoke:
These are very efficient when completely OFF or completely ON but will make heat in between. When used to control a lot of current, halfway open will smoke the FET.
That still handily beats a Darlington which when controlling a lot of current will smoke no matter how well you open it up!
GoForSmoke:
IRLZ44N are logic-level FETs, they turn fully ON with 2 or 3 volts control signal, 5V works great. Put a 220 Ohm resistor between the Arduino pin and FET gate since a FET has capacitance (field effect) to fill that could pull more pin current than is good. The resistor is to keep the AVR pin safe.
Should we have the "gate resistor" discussion again?
Misconception: You don’t need resistors on the gate
Back when I made the AddOhms episode, I added a resistor to the MOSFET’s gate pin. Of course any time a resistor is shown in a schematic, people get worried about what complicated formula is needed to determine its value. For slow switching applications, like below 10 kHz, the resistor value doesn’t matter. Something in the 100 to 1000 KOhm range is fine.
So if the value does not matter, why have one? The gate of a MOSFET is a small capacitor. And what happens when applying a voltage to a capacitor? It starts charging.
The initial current is very high. It slows down as the capacitor charges. That initial current rush, also known as in-rush current, can be a problem. Even though it is a short time, there is a significant current surge that can damage an I/O pin. Depending on the size of the MOSFET’s gate capacitance, it may not be necessary to include that resistor. I wish I could say to “just” add it any time you use a MOSFET. If there is a high switching frequency, say 100 kHz or higher, then you have to worry about the RC charging curve created by the resistor and the gate capacitance.
So when the FET will be switching 100+kHz, maybe don't use the resistor as it will slow the switching down.
Is that the discussion you mean or could you link to better please?
GoForSmoke:
MOSFET is metal oxide semiconductor field effect transistor.
These are very efficient when completely OFF or completely ON but will make heat in between. When used to control a lot of current, halfway open will smoke the FET.
You can get 10 for $2.36 plus the same $2.50 shipping.
I have some of these from a few years ago, they work and so far I haven't zapped any but watch out as MOSFETs are vulnerable to static.
IRLZ44N should switch power between the circuit and ground, not power. Connect the power and use the FET to allow it to flow to ground for this N type FET. Think of how your sink has a tap that you open to let water already in the pipes drain into the sink (like ground).
IRLZ44N are logic-level FETs, they turn fully ON with 2 or 3 volts control signal, 5V works great. Put a 220 Ohm resistor between the Arduino pin and FET gate since a FET has capacitance (field effect) to fill that could pull more pin current than is good. The resistor is to keep the AVR pin safe.
These things are cheap. Get extra, you can always sell some, the shipping cost and time have a value so you don't want to order twice. I spent almost $10 in 2014 or 2015 to get 60 pieces, worked out to 14.5 cents each.
PS -- almost forgot, they are good to over 12A current according to the spec. I have only switched about 2A feeding 12V led strips. The suckers will last "forever" with that little load.
GoForSmoke:
I try to keep it down to PWM speed but even there 8 bit 2k PWM values 1 and 254 switch at over 100k.
The switching frequency of PWM does not change no matter what duty cycle is being output.
With values such as 1 or 254, I understand that the output will go high, then very quickly low (or vice-versa), but this only happens once per PWM cycle.
Any "heating" in the AVR pin output driver due to the microseconds or less time the pin is "overloaded" due to gate capacitance and Miller is less than negligible and probably cannot even be measured.
An ON mosfet acts like a resistor and it is heat that will kill the mosfet. Since the heat is virtually zero, there is no damage.
In fact, a gate resistor slows down the mosfet switching time, keeping it in the power dissipating linear region longer, which can only be detrimental to the mosfet and indeed negates the benefit of USING a mosfet in the first place.
I always use a gate resistor - simple gate protection mechanism. That repeated charge/discharge of the gate can't be good for the pin in the long run. A small resistor is not going to affect the rise/fall times much.
If you're afraid the rise/fall times are too long, use a gate driver.
Wawa:
That might be a good thing if you run a 3.7volt vibrating motor on a 5volt supply.
As always, good advice can only be given if all the details are known.
Post#0: "vibrating motor with Arduino". Two unspecified things in that snippet.
Leo..
sorry about not giving entire information. It is a tiny motor, which is used in mobile phone. But it needs 1Amp to start vibrating.
krupski:
The switching frequency of PWM does not change no matter what duty cycle is being output.
With values such as 1 or 254, I understand that the output will go high, then very quickly low (or vice-versa), but this only happens once per PWM cycle.
Any "heating" in the AVR pin output driver due to the microseconds or less time the pin is "overloaded" due to gate capacitance and Miller is less than negligible and probably cannot even be measured.
An ON mosfet acts like a resistor and it is heat that will kill the mosfet. Since the heat is virtually zero, there is no damage.
In fact, a gate resistor slows down the mosfet switching time, keeping it in the power dissipating linear region longer, which can only be detrimental to the mosfet and indeed negates the benefit of USING a mosfet in the first place.
Silly me, I was thinking about how fast the Arduino pin can change the FET state as some kind of circuit limit and what that could do to the output of the FET when fed PWM. The gate driver circuit/chip should make cleaner output.
No resistor between pin and many FETs is how for brief time to exceed pin max current, a brief time times whatever frequency you switch. Burn that candle; it may take a long time even.
With resistor, if it's fast enough to get near 100KHz and your average is <5000KHz the heat producing time will be a tiny fraction of the total time. PWM only switches twice per interval.
GoForSmoke:
Silly me, I was thinking about how fast the Arduino pin can change the FET state as some kind of circuit limit and what that could do to the output of the FET when fed PWM. The gate driver circuit/chip should make cleaner output.
No resistor between pin and many FETs is how for brief time to exceed pin max current, a brief time times whatever frequency you switch. Burn that candle; it may take a long time even.
With resistor, if it's fast enough to get near 100KHz and your average is <5000KHz the heat producing time will be a tiny fraction of the total time. PWM only switches twice per interval.
Think of it this way: Flick your finger past a candle flame. You may feel a slight warmth, but you won't get burned. Do it a million times. You still won't get burned.
The TEMPERATURE may be high, but the total HEAT is very low. There is, as I'm sure you know, a difference between HEAT and TEMPERATURE.
The VERY momentary "overload" of the AVR output pin of course generates some heat (the laws of physics require it). But the amount of heat, as I said before, is so small that it cannot be measured. It doesn't "accumulate".
If the momentary pin current is such a concern, then why aren't there resistors on ALL the hundreds of thousands of gates inside the AVR? A lot of them are switching at the full 16 MHz, yet the chip doesn't even get warm.
I think I might setup a little 328P with 8 TO-220 package logic level mosfets and connect them without resistors and then switch them as fast as I can (probably 8 MHz?). I'll even wrap it all up in a piece of Kaowool so it gets "good and hot"
As soon as something fails, I'll report it. Hopefully, you won't be holding your breath.......
