Light bulb experiment radioshark
One photo shows a black wire from the cathode of the LED to the long negative row, and a red jumper from one of the resistors to the red positive row. An orange jumper is between the anode of the LED and the 5-hole row of the resistors.
Two photos show the connections for the green LED for one of the tests. The cathode may also be identified by a small flat part on the brim of its hat-shaped package. LEDs have a long lead (the anode) which connects to the resistor and then the positive side of the battery, and the short lead (the cathode) goes to the negative side.
LIGHT BULB EXPERIMENT RADIOSHARK SERIES
My first step was to measure the voltage drop across different colors of LEDs, with a variety of series resistors to limit the current. This arrangement allows an LED or light sensor to be connected to any resistor and to power as needed. One side of all the resistors is plugged into one 5-row, and the other ends are in different 5-rows. The 5 holes in each row are connected underneath. The various LEDs and light sensors are plugged into different 5-hole rows. The holes in each long row are connected together by metal strips under the board. In the photo above, positive 4.5 volts from the battery holder can be supplied to the red row of holes along the length of the breadboard, and the negative side of the batteries to the blue row. The breadboard is optional, but it makes the job easier and faster. Digital camera if you want to see whether an IR emitter is working.Breadboard (optional) with jumper wires.LEGO Mindstorms EV3 IR beacon remote control.Infrared (IR) emitter #2: 5mm, Radio Shack catalog #2760142.Infrared (IR) emitter #1: 5mm, Radio Shack catalog #2760143.100 watt frosted, incandescent, 120 volt, light bulb.A quick calculation shows the sun was only about 23 degrees above the horizon at noon. Sunlight: not very strong in late December at our latitude of almost 44 degrees North.Comments on the Internet suggest that the detector in some of these packs is a transistor but in other packs it’s a photodiode, even though the description on both packs states “phototransistor” and the catalog number is the same. Infrared (IR) detector #2: 5mm (phototransistor), Radio Shack catalog #2760142 contains both a detector and an emitter.Infrared (IR) detector #1: Knight Lites KID-7404 5mm (phototransistor).Light dependent resistor (LDR): 7mm diameter, 300 ohms light resistance and 10M dark.Solar cell: from a very cheap solar garden lamp.Photodiode: BPW34, suitable for visible and near infrared light.
LEDs: a pack of 3mm and 5mm LEDs of various colors.The IR light can be seen in the screen of a digital camera. Infrared light is invisible to the human eye, but the emitter had a barely visible red glow when lit. The purpose of the tests was to compare different sensors, and not to determine how bright an emitter could shine. The light would be brighter if the resistor had a lower value, but I wanted to be cautious after burning an emitter out. The IR emitter was connected to 3 AA batteries (4.5 volts) thru a 220 ohm resistor. I measured the voltage generated by each sensor from different light sources: sunlight, 100 watt incandescent light bulb, IR emitter, and two types of IR remote controls. My curiosity got the better of me and I decided to test them all. On researching the subject, I was surprised that LEDs could be used as light sensors and that there are so many types of sensors for detecting light: photodiodes, solar cells, light dependent resistors (LDRs), and infrared (IR) phototransistors. Two circuits I was making, a proximity sensor and a sun tracker, weren’t working as expected, and so I decided to test the sensitivity of the light sensors these circuits used.