DrLuke wrote:The pull-down resistor isn't necessary, as the pins of the arduino are of a push-pull-type, meaning they can both source and sink a current.
ameyer wrote:Ok, you are right. BUT.... if the pin ends up floating the transistor will trigger. So as a safety precaution I think we should leave it incase the wire came lose you dont want it to activate.
You basically have an In called the Source, an Out called the Drain, and a Control called the Gate. When you send a HIGH signal to the gate (control pin), the transistor switches and allows current to flow from the source (in) to the drain (out).
Xnient wrote:DrLuke wrote:No, it "drains" the technical current and then "sources" it again.
Ah, yes, that makes more sense. But I think my correction is still valid.
Your statement is actually correct if you use the electron flow current model (ie, current flows from the negative of a battery, though your circuit and back into the positive terminal). Most people (at least that I know of) use the conventional current model (where current flows from the positive of a battery, through the circuit and into the negative). In this case the statement that I mentioned above is backwards.
If your brain uses the electron flow model, you can just reject (and delete if you like) my complaints. It was shortsighted of me to think that the conventional current model is the only one in practice.
wezside wrote:Is there a reason why the pull-down resistor is not present in your previous post http://bildr.org/2011/03/high-power-control-with-arduino-and-tip120/?
profmuggs wrote:I am trying to understand the difference between FET and BJT transistors. You say in this tutorial that you can use either to accomplish the same thing, but that they require a different setup. Why would you use one over the other?
This video is showing the capabilities of PWM with the RFP30N06LE. The light, though it looks like a standard house light, is actually a 15W 12V DC light.
whitnasty1 wrote:Could you link me to where you picked up that light bulb that you are switching in the video? Could you also give me a quick run down of the specs on it? I want one to play with! I thought most bulbs like that ran off of AC voltage? Anyways great write up as always, and if you could just show me where you got that bulb I would be most appreciative.
whitnasty1 wrote:Oh okay thank you very much, must have missed the link to the actual bulb in the article. What kind of receptacle for the bulb are you using? Just a standard one from any home improvement store or are you using something specifically? If you are could you give me an example of what I need to purchase? Thanks very much and keep up the great work on this awesome site!
jayusa123 wrote:There seems to be an error in the third diagram. The flyback diode isn't necessary across the lamp leads. The article text is correct and indicates that only 2 of the 3 diagrams should show a diode, but it appears in all three.
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