Re: Help Getting Started - Simple DC Circuit

ehsjr wrote:
<snip> 

Here's an updated schematic to incorporate Jason's idea
of adding a 1K resistor in parallel with each of the first
30 LEDs. It will allow the circuit to work as the batteries
drain below 2.75 volts. It will also allow you to use a higher
supply voltage if you want, like 3.6, 4.5 or 6 volts, but you
would need to change the value of R1 through R31 using the
values below:
3.6 volts use 150 ohms; 4.5 (or 4.8) volts, use 270 ohms;
6 volts, use 330 ohms.

Ed


+3 ---+-------+----------} }----+-------+------------+
      |       |                 |       |            |
    [LED1]   [1K]             [LEDn]   [1K]        [LED31]
      |       |                 |       |            |
      +-------+                 +-------+            |
      |                         |                    |
     [R1]                      [Rn]                [R31]
      |     ->|-                |     ->|-           |
      +---[Diode1]---+          +---[DiodeN]---+     |
      |              |          |              |     |
   [Switch1]         |       [SwitchN]         |     |
      |              |          |              |     |
     Gnd             |         Gnd             |     |
                     |                         |     |
                     +---} }-------------------+     |
                                               |     |
                                             [4.7K]  |
                                               |     /c
                                               +----|   NPN
                                               |     \e
                                            [100K]   |
                                               |     |
                                               +-----+
                                               |
                                              Gnd
.

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