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182        Making Things Move




               The side of the LED over the shorter ground leg is usually flat, so you can still tell
               which side is ground, even if you clip the legs shorter. Install the LED in the circuit so
               that current flows through it from the long leg to the short leg.

               LEDs don’t limit voltage on their own, so you need to put a resistor in series with your
               LED before hooking it up to most power sources, or else you’ll fry it. For example, if
               you’re using a 5V power supply, a 220KΩ resistor will work well with most LEDs. At
               higher voltages, you’ll need proportionally higher resistors to protect your LED.

               Decoupling Capacitors
               You can use capacitors to your advantage in circuits with motors to smooth out the
               energy spikes that happen when motors are turned on or change directions.
               Capacitors used for this purpose are called decoupling capacitors.

               A popular approach is to solder a capacitor across the two leads of a DC motor before
               ever using it, just to be safe. You may also see capacitors soldered from the motor leads
               to the motor housing (see Figure 6-40). Make sure to use ceramic (not electrolytic)
               capacitors for these applications, since they don’t care which way the current flows
               into them. This will allow you to run the motor clockwise or counterclockwise with
               no worries.



               FIGURE 6-40 Decoupling capacitors soldered to DC motor leads
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