Hi friends
I have 12Volt LEDs that i want to control them with arduino uno and i need to send data to board at same time with onboard usb to serial. can i use external 12V source for board and connect usb cable to my computer at same time? or it may hurt my usb port or board?
Regards
Sure, you can do that. I've built a project where some of the electronics runs off of 12V, and during development I left the USB plugged-in so I could upload new sketches, or to use the serial monitor.
But, you're not planning powering the 12V LEDs with the Arduino, right? You're just controlling them with the Arduino, right?
Thanks for your help
right, i want to get 5v from arduino to trigger base of TIP transistors. arduino gives R,G,B values from computer usb port ( virtual com ) and convert data to 3 pwm signals of transistors ( to control RGB led)
That's fine. We here do that kind of thing all the time.
In that case, it sounds like you're not even connecting the 12v to the arduino. We assumed you were powering it off a 12v power connector - which is also fine to do.
What you do need to do for that setup, if you didn't know, is connect the ground of the 12v supply to the arduino ground, so that there's a return path for the base current.
Thanks friend
I did it by tip41 and dc motor but my motor doesn't work on 12V, its only about 4v after pin13 trigger!!
That particular transistor needs a lot of base current and has Vbe of 2V when on.
Use a smaller base resistor.
Try putting up to 35mA into the base, arduino output will drop some, like down to 4.2V:
(4.2V - 2V)/.035 = ~68 ohm.
If hfe was 30, then you could expect maybe 1A to flow thru the motor, depending on its winding resistance and the power supply capability.
If Vin (equal to barrel - 0.7V)/2 is > 3.3V, Vin will power the board thru the 5V regulator and not USB power.
thanks for your answer
I have used 220,100 and 10 ohms too but still there are no enough current to drive motor, when it's 10 ohms base current is just 1ma !!! there are not current leakage anywhere because i use this circuit with mega8 and pic16 and it's ok!
i changed my arduino port too but still its current is low to drive my motor!!
i thought maybe my port has problem but when i connect it by 10 ohms resistor to single led it drives 50ma not like 1ma!! i use a diode on my motor poles too but no different!!
as i said program properly but my port current is so low!!
I have replaced 12V led strip by motor and it's ok!
when motor starts it seems current and 12v is ok on it but for very very short time!! maybe some spike from motor causes problem?
sorry for my bad english!
oww sorry problem was on motor!! I replaced another one and it's ok now.
Thanks again