resistor
Components that restrict the flow of current. These can be combined with bipolar junction transistor to create logic circuits.
Symbols
There are two symbols that can be used to represent a resistor:
Color code
Through-hole resistors have their value indicated by a sequence of colored rings.
| Color | Figure | Multiplier | Tolerance |
|---|---|---|---|
| Silver | 10-2 | 10% | |
| Gold | 10-1 | 5% | |
| Black | 0 | 100 | |
| Brown | 1 | 101 | |
| Red | 2 | 102 | 1% |
| Orange | 3 | 103 | 2% |
| Yellow | 4 | 104 | |
| Green | 5 | 105 | 0.5% |
| Blue | 6 | 106 | 0.25% |
| Violet | 7 | 107 | 0.1% |
| Gray | 8 | 108 | 0.05% |
| White | 9 | 109 |
Example: Yellow - Blue - Brown - Gold = 460 +/-5% ohms
Pull-up/pull-down resistors
Here, closing the switch "pulls" the microcontroller's input to 5V, which is read as a high state. But opening the switch leaves the input pin floating. This should be avoided as the microcontroller can not resolve it as high or low. To solve this, we can use a pull-down resistor between the input and ground.
With this setup, the input pin is pulled to ground when the switch is open, allowing the microcontroller to read it as a low state.
Pull-up resistors use the same principle, but pulling the input to 5V instead of 0V.