Hello, I have a circuit, in which I connect a fan to transistor and I can control it through arduino. The question is do I really need a diode between fan + and -? One forum member has told me that TIP120 transistor already has a diode inside of it, so do I need to attach one more?
The TIP120 does have a diode according to the specsheet, but:
The diode is there to counter the electromagnetic induction. So it's a safety thing and you can never have enough of those!
The diode on the TIP120 is there for a whole other reason than the other diode. Just keep it there...
Ok, thanks for quick reply:)
I just hope that the 9V square battery is a representation of something much better. Those batteries don't last long with motors.
Just wondering why the little arrow above "1N4004" is pointing to the black wire hanging off your transistor. Surely that should be described as "wire"
The diode in the TIP120 won't help you unless you are building a 1/2 H-bridge or
full H-bridge, since the diode must go across the load, not the switching device.
In bridges each device's diode protects the other device from over voltage.
Yeah, definitely leave the diode in across the motor terminals - you should have one of those whenever you drive an inductive load.
Some drivers (like the ULN2x03) do contain a resistor between the collector and the positive supply (which is what you need - as it goes from the negative side of motor to positive supply to motor), but obviously, a transistor that's connected to ground, load, and arduino can't include that diode, since it's got only 3 pins and none go to VCC. In any event, there are few things in the world that are cheaper than diodes, and it doesn't do any harm to use one - so when in doubt, use a diode.
Some drivers (like the ULN2x03) do contain a resistor between the collector and the positive supply
DrAzzy,
I think you mean diode not resistor there.
It's not a fan motor as such, it's an electronic fan what's being used.
Lots of guys around here break down in a fit of tears if you suggest they need a resistor or something.
The diode, given the specifics of the application here which I'm not unfamiliar (though undisclosed by the OP herein), is superfluous in my horrible opinion.