Introduction: Relay Controlled Work Light
I just finished making a really nice work bench that gives me plenty of work area, a place for my equipment and even a shelf underneath for my xbox one as well as a shelf for my tv up top that I use for recordings and play.
I designed the bench to accommodate an led tube lamp in a metal housing but when I tried to set up the light I noticed that the metal housing weighed too much and made me fear a break in the wood. That and it was almost impossible to level the dang thing. I decided to then build a simple over hang light using 4 led light bulbs and some sockets. A few days after using it I noticed that its too bright for use when not filming a video, taking pictures or general non work related things. I wanted to control the amount of light by having 1 of the 4 bulbs or all 4 lit at a time. This would give me perfect lighting for whatever I needed it for.
I threw together a 4017 binary counter circuit with a manual clock input that would drive relays to control the lights. This would allow me to press a button to turn on 1 of the 4 lights or all 4. I will explain the circuit in depth in the schematic step! Before making this circuit I would just unscrew the bulbs I wanted off.
Before I continue I feel its needed to say that this project involves working with alternating current. Which is very dangerous and lethal. Do not attempt this project if you are unfamiliar with it.
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Step 1: Watch the Video
I recorded the entire build and uploaded it to my youtube channel. Please watch it for a more in depth coverage :)
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Step 2: The Schematic and Further Explanation
A 4017 decade binary counter turns on its outputs one after the other in a sequential way based on a clock input. Once the clock input goes high it shifts 1 of the 10 outputs high, then once it goes low and high again it turns off that output and turns on the next. A clock input is usually generated by an ic of sorts but for this application I wanted a manual clock input which requires a capacitor in parallel with a switch and a pull down resistor. These added components avoid an annoying thing called switch bounce. Without them, when the button is pressed the 4017 will read the small oscillations from the switch after being pressed as an input and cause it to clock accordingly. I used 5 outputs of the 4017 to drive tip31 transistors which when turned on close relays to ground. These relays turn on and off the 4 lights. There are 5 relays and transistors but only 4 lights. The first 4 relays are driven with outputs 1 through 4. These control the lights directly when activated. When the transistor and relay turn off the relay returns to the normally closed position, and as you can see from the schematic all the normally closed pins of the first 4 tie together and feed into the common pin of the 5th relay. This relay is responsible for turning on all the lights by using the 5th output from the 4017 and controlling all 4 lights with their relays normally closed pin. That way 1 of the 4 or all 4 turn on at one time.
Lets say 1 = on and 0 = off here is a representation of the lights when triggered
Using that example you can better understand the functions
Its safe to add a diode in parallel with the relays coil to help with the magnetic field breaking down but unfortunately I didn't add those to my cart when buying the components. They have since been added.
Step 3: Wiring Up the Light Controls
I used a piece of wood to assemble the 4 lights and added the circuitry on top. Its important to note that I didn't insulate the relays which is very dangerous since they are carrying AC. A small touch to the wrong pin could lead to a shock . I plan on adding a box to incase all the components. I advise you do the same with any electrical potential that poses a risk.
The wiring was a bit tedious but worth it. I also added leds to show the status of the output. All the circuitry is powered by a 5 volt supply and everything is turned on and off with a main pull chain switch.
Step 4: Look at the Lights Being Clocked!
These are images showing the lights being activated after the button is pressed.
I look forward to many projects under these lights. Thanks so much for viewing and feel free to subscribe to me on youtube and instructables!
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