Actions
Forum Thread Details
  • State Suggested Answer
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 287 subscribers
  • Views 596 views
  • Users 0 members are here
Related

Beginner question: 12V wall wart to power both a msp430 microcontroller and an LED strip

Former Member

Hi all

 

I wish to make a circuit, where I control an LED strip  from a msp430 microcontroller (a MSP430G2231 that came with the MSP430 Launchpad). It needs 1.8-3.6V. The LED strip needs 12V. And yes, this IS for gaudy christmas lights :-)

 

I think I have figured out to control the LED strip through a MOSFET.

 

So the question is all about the power supply.

I figure that the easiest option would be to run the LED strip of a separate 3V coin cell battery as the msp430 doesn't use much power.

 

But if I wanted to avoid batteries, what would easiest and cheapest way to convert the 12V from a salvaged small wall wart to ~3V?

This is what I have been looking into:

 

  • 7805 (5V) ICs seem to be readily available, but I have not seen a 7803. Could you drop the final 2v, maybe by using a diode of some sort?
  • Other option is equally available LM317 and hardwired adjustment resistors.

 

These are linear options, right? I guess that during to the low current draw of the msp430, heat is not a huge worry?

 

Am I way off?

Parents
  • 0

    Hi Niels,

     

    There are some 7805-like devices for 3.3V, perhaps that would meet your need. This one is in a large SMD package (D-PAK) so it can still be soldered by hand very easily, and would be fine to run from 12V directly, for a low power board. If the current is of the order of a few tens of mA, then there is no heatsinking concern for your application. I think it would be the best option all-round. There are some small switched-mode modules too which are more expensive but are not necessary here.

Reply
  • 0

    Hi Niels,

     

    There are some 7805-like devices for 3.3V, perhaps that would meet your need. This one is in a large SMD package (D-PAK) so it can still be soldered by hand very easily, and would be fine to run from 12V directly, for a low power board. If the current is of the order of a few tens of mA, then there is no heatsinking concern for your application. I think it would be the best option all-round. There are some small switched-mode modules too which are more expensive but are not necessary here.

Children