Beginner Parts Kit Identification Guide
jimblom, 
bboyho Diodes
The Diodes - 1N4148 and 1N4001
Diodes are used to ensure that current only flows in one direction, this comes at the cost of a small forward drop across them. There are two varieties of diodes in this kit: the 1N4148 small-signal diode, and the 1N4001 rectifying diode. The 1N4148 is the neat looking orange-and-black diode, where the black line marks the negative (cathode) side. The 1N4001 is the black and gray diode, and the gray line marks its cathode.
Both diodes share the usual diode characteristics, however they differ in their electrical ratings. The 1N4001 has a much higher forward current rating, 1000mA, compared to the 1N4148's 200mA rating, but it also has a slightly higher forward voltage rating. Because of its relatively high-current rating, the 1N4001 usually takes a role in power conversion circuits, like DC-DC converters, and AC-DC rectifiers. The small-signal 1N4148's are better used in low-current applications, like logic circuits.
For a much deeper read on diodes, check out our diode tutorial.
LEDs
Green, Yellow, Red 3mm LEDs
No project is complete without a blinking LED. That's a fact! The parts kit includes one of each green, yellow, and red 3mm LEDs.
LEDs have two terminals, an anode, the positive side, and a cathode, the negative side. The two terminals can be distinguished in two ways. If you look at the base of the diode, you'll notice it's not exactly round, there's a flat edge that signifies the cathode. I'm terrible at seeing the flat edge though, so I usually look for the shorter of the two legs, which also indicates the cathode.
There are two aspects to illuminating an LED: the LED requires a specific positive voltage, and it also needs just enough, but not too much, forward current. These ratings for all three LEDs are in the table below.
| LED Color | Suggested Forward Current | Max. Forward Current | Typical Forward Voltage |
|---|---|---|---|
| Green | 16-18mA | 20mA | 2.0V-2.4V |
| Yellow | 16-18mA | 20mA | 2.0V-2.4V |
| Red | 16-18mA | 20mA | 1.8V-2.2V |
For a great discussion on LEDs, check out our LED tutorial.
Light-Emitting Diodes (LEDs)
August 12, 2013
The 7-Segment LED - RED
Taking a starring role in the Parts Kit is this rectangular component, which houses eight LEDs total.
Seven LEDs comprise what we call a 7-Segment display, and can be turned on or off to create any number or near-representations of many other characters. An eighth LED controls a decimal point to the bottom right of the digit. You've no doubt seen 7-Segment LEDs in other big-time roles, like your alarm clock, radio, microwave, and tons of other devices that need to show a numerical value.
The 7-Seg LED has 10-pins, five on each the top and bottom of the display. All LEDs share a common anode, pins 3 and 8, while the rest of the pins are the individual cathodes of each LED.
