0

I went and bought an LED strip which has the following labels

  • +V
  • R
  • G
  • B

How does this correspond to another naming scheme I have seen which looks like so:

  • GND
  • DI
  • CI
  • +5V

I could use this tutorial, but then I have to go out and purchase those transistors. Can I instead use this LED strip with this tutorial?

3

The strip with DI, CI uses the SPI interface, and is not usable with a RGB LED strip.

I would be wary of using the RGB tutorial you referenced. This does not even provide a circuit diagram, only an unlabeled "wiring diagram".

This appears to connect the bases of the power transistor direct to the Pi without either a pull-up (if LED is supposed to be on if Low) or current limiting (if LED is supposed to be on if High). Series resistors are a good idea in any event to protect the Pi.

There are no current limiters in series with the LED (these may be on the LED strip).

  • You are absolutely correct about the resistors between the Pi and the TIP120 power-transitor. The transistor will act like a diode between the GPIO pin and ground. That setup will eventually fry your Pi. – Gerben Feb 24 '14 at 14:25
  • All the strips I've seen have current limiting resistors on them. – Gerben Feb 24 '14 at 14:41
1

The second type of led strips are a lot more expensive, but with those you can give all the leds a different color.

The led strip you have now, you can only set the color of the entire strip. Also not that your strips probably require 12 volts, not 5.

I would use some mosfets to switch the red, green, and blue leds on the trip. Also add some resistors between the pi and the base of the FETs. Maybe some pull-down resistors to make sure the leds are off when the Pi is off/booting-up.

  • I have noticed that the standard ones are 12v not 5v, why is that? – puk Feb 24 '14 at 15:56
  • Not sure. Higher voltage, means the led strips can be longer. 12V is also quite common in lighting systems. Also in most strips the leds are grouped into sets of three, with one resistor limiting the current. Otherwise you'd need 3 resistors, costing slightly more. Why would 5V make more sense? – Gerben Feb 24 '14 at 19:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.