Arduino Electronic countdown timer for rocket launcher

Hi guys,

I am new to electronics and I have been wanting to design a countdown timer to automatically fire my rocket igniters.

Here is the youtube link

Here is the schematics for it

the equipment required would be:

Arduino UNO R3 (recommended for beginners with Arduino)
7 segment Serial Display
10k potentiometer
yellow arcade button
piezo buzzer
protoboard / protoshield
missile switch cover
LED lights
10k ohm resistors
N-channel Fets
9V batteries
resistors
5V relay
tupperware box or 3D printed case for the electronics

my questions which come to mind are

The capacitor acts like a small battery correct?
the n-channel transistor what does this actually do?
the 1N4001 what does this do?
the 5V relay what does that do? switch currents?

do all the negative wires connect to just 1 GND slot or do I use a separate GND slot for each jumper wire? do I use a breadboard for this whole thing or a protoboard?
I wish this schematic included a diagram of how to setup the jumper wires.

These resistors with varying Ohms… why not use a standard 460ohms resistors for the entire circuit board? I know this sounds like a stupid question but I don’t know electronics well enough to answer this question. Appreciate all the help.

lucifer911: The capacitor acts like a small battery correct?

Sort of yes. But if you are referring to the capacitor connected to the speaker, this is to block the DC offset coming from the Arduino. Speakers only care about AC signals so adding a capacitor blocks DC and allows AC to the speaker (which causes it to vibrate). If the resistor and capacitor were not there, the speaker wouldn't work very well and may overload your Arduino or burn out the speaker as it has little resistance.

the n-channel transistor what does this actually do?

If following the schematic, it is being used as a switch. When the transistor is turned on, current is allowed to pass from VCC to ground, through the relay coil. Doing this helps protect the Arduino from voltage spikes (back EMF) from the relay coils when current is removed from the relay coil.

the 1N4001 what does this do?

This is being used as a flyback diode. It dissipates the back EMF coming from the relay coil when it is de-energised.

the 5V relay what does that do? switch currents?

Essentially, yes. In the schematic it is switching a 6V ignitor on a separate circuit. The Arduino is only rated for 5V. Depending on the specs of the relay, you could switch much higher voltage loads without fear of damaging your Arduino and low voltage circuitry.

Plus they make cool clicky noises when turning on and off. :D

do all the negative wires connect to just 1 GND slot or do I use a separate GND slot for each jumper wire?

All the Ground connections on the Arduino are connected together. You can choose to connect your jumper wires to any, or you can connect the Grounds to your breadboards ground rail and connect your ground jumpers to that. You should not connect the 6V circuit to the ground on your Arduino. This should stay separate.

do I use a breadboard for this whole thing or a protoboard?

That's your choice. Breadboards allow you to quickly throw a circuit together and is much easier to chop and change. Using protoboard usually means soldering. It makes it a bit of a pain to quickly chop and change!

These resistors with varying Ohms.. why not use a standard 460ohms resistors for the entire circuit board?

Resistors reduce current and how much you need to do that depends on the devices they are connected to. It would make life much less interesting for electrical engineers and hobbyists if only one type of resistor is required! :p