Just fiddling with an RGB Strip that I want to put on my Bike, as a nice neon, with a switch to change the lights.
Power supply to Arduino - From Bike battery, 12V,9Ah (Probably higher when the bike runs, as the battery charger does its work.), So I have a LM317T reducing the voltage to 8.5 volts, so that I amnt overloading the voltage regulator in the Arduino.
Power supply to the RGB strip - Another LM317T, reducing the voltage to 12V. (So the strip is dim when the bike isnt running. And gets full 12, as the bike runs.)
I have the power supply circuits ready, and I am currently doing the arduino, strip connections.
This is a picture from Adafruit.
I have few doubts about the transistors and the use of transistors.
Why is a transistor needed here?
The Adafruit shows, that they are running the strip from the arduino Vin. Do they provide that much current to light up those leds? They dont have a limit for the current flow?
And What transistor do I need here? They say T0 220 package, but can you name one exactly that I can purchase?
xkishorx:
Power supply to the RGB strip - Another LM317T, reducing the voltage to 12V. (So the strip is dim when the bike isnt running. And gets full 12, as the bike runs.)
Your understanding is incorrect. An LM317 can only reduce something that's "greater than" in the first place.
Just take the "strip +12" directly from the 12V/9A battery.
To me, "Bike" == bicycle.
For an LM317 to work right, if that's an important consideration, then the input must be 2.5V > the expected output.
There are adjustable LDO's requiring input 0.5V > output, even if they're usage isn't as "carefree".
Don't motorcycles have regulators (like cars do)?
The 12v led strip can be driven directly from t_he bike's 12v electrical system. nplus or minus 2 volts won't hurt it. no v. reg . necessary. We do need to know the current draw on the led strips in order to recommend a transistor ( or MOSFET).
I am to use a voltage regulator for the LED strip supply because, I have friends telling me there can be voltage spikes ranging upto 18 volts, from the charger.
Bike here is motor cycle
The current draw will be 1-2Amps.
I am still unclear why do we need a transister. Whats the actual use of transitor here?
I am still unclear why do we need a transister. Whats the actual use of transitor here?
It makes the small current from the arduino into a large current to drive the LEDs.
The arduino has a very limited current output and can only drive two LEDs max.
I am still unclear why do we need a transister. Whats the actual use of transitor here?
It makes the small current from the arduino into a large current to drive the LEDs.
The arduino has a very limited current output and can only drive two LEDs max.
Do I still need it if I am to use seperate supply for the Strip?
Q : So the Transistor Amplifies the current? Smaller current into a Larger one? Doesnt voltage undergo any change then?
Do I still need it if I am to use seperate supply for the Strip?
Yes.
So the Transistor Amplifies the current?
Yes.
Smaller current into a Larger one?
Yes
Doesnt voltage undergo any change then?
No.
The voltage is already there at the power supply what the transistor does is act as a current controlled current switch. It does nothing to the voltage.
I understand that I need the transistor to amplify the current when the power supply is from Arduino. Are we talking about the Vin, or it needs the transitor even if I am working with Digital pins? How does the current limit of 40mA works with this? And, if I am having separate power supply,the source has enough Amperes to drive the strip, so why is any amplification needed.
My strip will consume about 1-2amps. Can I know the transistor I need? The site says T0 220 package is fine. But Not sure which is the one I should get. I mean, the exact one, so that I can simply buy it.
Are we talking about the Vin, or it needs the transitor even if I am working with Digital pins?
Yes it needs the transistor if you want to control your LEDs from the arduino. The current from the arduino is under the control of your program, it is that you can turn on and off. It is that that is limited to 40mA and in fact better if you keep it to 30mA or lower. It matters not where the LED current is coming from you are controlling it from the output pin and you can only get a small current from that.
if I am having separate power supply,the source has enough Amperes to drive the strip, so why is any amplification needed.
Because you want to switch it with the arduino, if you don't then just connect it up to the 12V supply and throw away the arduino.
The site says T0 220 package is fine
That is just a package it is nothing to do with what is inside it. What you need is a logic level FET, there aer lot of different ones of these. One example of one that will work is a IRL520n but it depends on what you can get hold of. Make sure it is described as "logic level" or it won't work. Just for good measure I would put a 10K resistor between the output pin and ground for each strip. This will stop the FET from powing the strips in the time between applying power and when the arduino kicks in.
