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I have below configuration:

                |---------|------- LED1
                |         |
24V, 350mA------|Switcher |------- LED2
                |         |
                |---------|------- LED3
                      |
                      | 
                      |
                MCU to select the line

I need to route the input (24V, 350mA) to one of LED string at the output (1,2,3) by a MCU to turn on/off the LEDs. It is required that all LEDs may be turned on at the same time. ( I can dedicated a GPIO per led string on/off)

What is best to use as a switcher considering 1) small size 2) low cost? It should have long product life (>10 years). I couldn't decide if I should prepare something with 3 transistors and each transistor is controlled by a MCU or a signal relay or a multiplexer.. What would you be your suggestion?

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  • \$\begingroup\$ There's a schematic button on the editor toolbar. Much better than ASCII-art! \$\endgroup\$
    – Transistor
    Jan 22, 2016 at 17:50

2 Answers 2

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For small size and low cost, MOSFETs are the way to go. 3 MOSFETs, 3 GPIO lines, simple.

Relays are bulky and may not have the lifetime you want, and a multiplexer doesn't work very well because of the power requirements and because you want them all on at the same time.

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  • \$\begingroup\$ why mosfet? is it because of power consumption? \$\endgroup\$
    – sven
    Jan 22, 2016 at 17:16
  • \$\begingroup\$ @sven MOSFETs dissipate a little less power and require 1 resistor less than a bipolar transistors. \$\endgroup\$
    – ilkhd
    Jan 22, 2016 at 20:28
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I would use 3 transistors. A relay is not good from size or life time consideration. A multiplexer is a set of switches, usually transistors. A SI2308BDS in SOT23 case size would be suitable.

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