Essmart Hackathon Peter Burkimsher and Sreechand Tavva

What to expect A basic introduction to electricity How to read a circuit diagram Common electrical components Series and parallel circuits What not to do Advice for best practice Build your own multi-brightness LED!

Electricity - 1 V+ GND

Electricity - 2 V+ GND

Electricity - 3 V+ GND

Voltage V V+ GND

Voltage V V+ GND

Voltage V V+ GND

Current A V+ GND

Current mA V+ GND

Current mA V+ GND

Shorting out 500 mA 5 V V+ GND

Circuits 500 mA 5 V V+ GND

Resistor 20 mA 5 V V+ GND 4.7 kΩ100 Ω

Diode 5 V V+ GND V+ GND

Diode warning 500 mA 5 V V+ GND

LED 5 V V+ GND V+ GND

Practical 1 – Series LED

Practical 2 - Switch

Switches 0 mA 5 V V+ GND

Practical 3 – Series Resistors

Practical 4 – Parallel Resistors

Variable Resistor 5 V V+ GND

Practical 5 – Variable Resistor

Practical 6 – Parallel switch

Thank you for your participation!

Circuit Diagrams - LED Here is a simple circuit diagram. It shows an LED connected with a resistor in series. We will build this soon! Colours are optional, I added them for clarity.

Circuit Diagrams - Switch Now let’s add a switch in series. What happens when you turn the switch on – The LED lights up The black dot joins two or more wires

Series – 1 So far, all the components we connect are in series, one after another. In a series circuit, there is only one path for current to flow. Let’s add 2 more resistors in series.

Series – 2 The total resistance is the sum of each component’s individual resistance. R total = R1 + R2 + R3 R total = 4.7kΩ + 4.7kΩ + 0.1kΩ R total = 9.4kΩ kΩ

Series - 3 When the resistance increases, the current through the LED is smaller. What happens to the brightness of the LED when there are 3 resistors in series, compared to only 1 resistor? – The LED becomes dimmer.

Easy Maths Voltage V is the current I multiplied by the resistance R. V = I × R Therefore R = V ÷ I, and I = V ÷ R V I R

Parallel - 1 What if you connect the 2 resistors next to each other? There are 2 paths for the current to flow. How much flows through each?

Parallel - 2 The ratio of current flow depends on the resistor values. If the resistors are the same – The total resistance is half. – For us, that means 4.7 ÷ 2 = 2.35 kΩ

Parallel - 3 The resistance is smaller than it was when a 4.7kΩ resistor was attached in series. What happens to the brightness of the LED? – The LED becomes brighter

Voltage Divider - 1 If you connect two resistors in series from V+ to GND, you can build a voltage divider. The point between the resistors sees half the voltage (V+/2) relative to GND.

Voltage divider - 2 If you connect an LED in parallel with the second resistor, the voltage across that part of the circuit is V+/2. For our 5V supply, this means only 2.5V.

Voltage Divider - 3 Voltage dividers can be tuned to achieve any voltage less than or equal to the V+ voltage. The voltage across the LED depends on the ratio of the resistances. A variable resistor lets us change this quickly.

What not to do – 1 Please don’t short out your power supply! All of these circuits are shorted out. Always connect a resistor in series to the LED!

What not to do – 2 Don’t plug components in randomly. You should understand the circuit, and know how to get it right first time. All of these circuits are the same:

Best practice Check that your connections are strong. Screw a wire in tight, so you can’t pull it out. Wires shouldn’t touch outside the block. If a wire becomes frayed, twist it together and “tin” it (cover it with solder). Label your components with red and black pens if direction matters.

We’re ready to build! Finally, we’ve been through enough theory. Let’s build some circuits! This should be quite quick, now you know what you’re doing. I’m going to show a circuit diagram, and you have to build it. When it’s ready, you can test it by plugging it into your power supply!

Practical 8 – Everything Let’s use everything we learned to build a full circuit with all the features we want! The switch activates maximum brightness The variable resistor controls brightness

Practical 5 – Voltage Divider A voltage divider places the LED in parallel with the second resistor. This should be half as bright as when the LED was in series with only the 100Ω resistor.

Changeover Switch Changeover switches let you choose 2 inputs. If one pipe is empty, a changeover switch is the same as a normal on/off switch. Our switches have 3 connectors for this. – We will leave one disconnected. Electronic symbol: 0 mA 5 V V+ GND

What not to expect Lots of maths – I did the calculations first. A finished product – You have to build it! Everything you need to know to build a robot/radio/phone charger/solar-powered lantern. – This is to get you started. You can look up instructions for new projects on the web!