Here is where we start to get into the nitty gritty..

For those of you who are new to electronics you better break out those peril sensitive sunglasses because this is going to blow your mind! I am about to describe the immensely complicated interplay between literally thousands of components with almost limitless possibilities.

OK, I may have slightly exaggerated with the thousands of components, its actually 9 and 5 of them are push buttons LOL but the limitless possibilities isn’t far off the mark because this basic setup could be the starting point of practically anything you could dream up.

Anyway, first thing you need to do is have a gander at the schematic. It will probably look scary as hell if you are not into electronics but its really quite simple to understand, here it is – just give it a click to see a larger version if your peril sensitive glasses are blacking out your vision..

Controller Prototype

Does it make any sense to you? OK, I will give you a run down of what’s what.

First of all we have the Arduino Duemilanove sat in the middle, you can tell its the Arduino Duemilanove because it says so in the middle of it. This is the heart of the project, well actually its the brain, this is the micro controller board which does all the work for you.

This baby is why you can knock together a project like this with just 9 components, it is a complete computer with processor, memory, inputs, outputs, and everything you need on one chip. The board has a few other bits and bobs on it to make using the chip easier, such as a USB interface to program it, a power regulator to give it a nice steady 5 volts, and a bunch of header connectors so you can just plug wires into it without soldering, but essentially the one big chip is what does the work.

If you look at the schematic you will see down the sides it has text like Reset, 3V3, +5V etc, this is the connections to the board, if you have a look at the photo of the arduino you will notice they are also printed on the actual board in pretty much the same positions. For this project we are only using a few of them, that’s the ones with lines coming out, and the rest are spare and nothing gets connected to them.

It has 5 analog in pins, the chip can ‘read’ these pins and determine what voltage is present (0-5 volts) and the program you upload can then determine what to do if the voltage changes.

Down the right hand side it has digital pins which can be set to either input or output, digital pins are either on (+5 Volts) or off (0 volts) We will be using two of these to trigger the camera and/ or fire the flash and one to turn on a waiting light (LED), when the pin is turned on it will make the camera take a picture when it is turned off it wont do nuthin

Below the Arduino you will see the LCD display, this is connected to the Arduino with just 4 wires. If you check the schematic again you will see that the 4 connections go to +5v and Ground (these two supply power to the LCD) and Analog in 4 & 5. Now the astute among you may be thinking why would the LCD be connected to Input pins on the Arduino, if you were then please accept a gold star for trying to work out the schematic, the reason is that Analog in 4 & 5 are also the I2C serial bus – Without giving a lecture on serial communication and god only knows what else what these two connections do is allow the Arduino to send information to the LCD display which then conveniently appears on the screen.

Below the LCD are the 5 buttons which allow you to set up all the timers, tell the controller to start taking photos, tell it to stop taking photos, in fact everything it can do is done via these buttons. As you can see there are 1,2,3,4 and Enter.

So why are these buttons connected to the LCD display and not the Arduino? The Arduino is, after all is said and done, the brains of the system so the buttons need to tell the arduino what do don’t they?

Well yes its the Arduino that needs to know what button is pressed, but the kind people who make the LCD display have also built in a keypad reader so you can stick a 3 x 4 keypad on it and get the keypresses from the same I2C serial bus as you use to print things to the display. I could have easily used the spare digital pins on the right hand side for these buttons, but as the LCD will read up to 12 of them without using any extra pins on the Arduino I figure I may as well let the LCD take care of it for me.

So that’s 7 of the 9 components dealt with, which leaves us 2 x 2N35 IC’s.

These clever little guys are ‘Opto- Isolators’ and are there to protect our nice shiny new Arduino from nasty flash guns that spit out horrible voltages. I have also included one on the camera output as well, not because your super duper digital SLR is going to spit nasty voltages out but because then there is no problem if you stick a flash gun in there instead. I am not entirely sure why you would want to do it, but if thats what floats your boat you can stick 2 flashes into the 2 output sockets and have the controller fire them both. Anyway, as the things are only 26p each I don’t think there is much point in skipping one

All these chips do is turn on a switch inside them with a light. There is no electrical connection between the item being switched on and the arduino, so if the item that is being switched on sends a high voltage down the wire it cant get any further than the 4N35 chip and the arduino is safe.

All that remains now is the sensor connections. The controller has 2 sensor inputs marked on the schematic as ‘To Sensor 1′  & ‘To Sensor 2′, in the finished article these connections will go to a couple of 3.5mm jack socket on the back of the unit so you can plug your sensor of choice into the thing. Each sensor has 3 connections, +5 Volts and Ground to supply some juice to the sensor and Sig which brings back the signal from the sensor. Basically what happens is the sensor gets powered up by the 5 volts, detects whatever it is designed to detect (light/ sound/ stupid people etc) and sends a signal back down the Sig wire.

The laser trip wire for example works like this:

The laser module is connected to +5v and ground, and then sends out a laser beam because that’s what laser modules tend to do. The laser beam hits a reflector, or retro reflector to be more precise, which bounces the light back in the opposite direction straight back at the laser module. Sat next to the laser module is a photo transistor which detects the reflected light and converts it into a voltage between 0 and 5 volts depending on how bright the reflected light is and sends that back down the Sig wire.

Our clever Arduino is sat there watching the voltage that comes back down the Sig wire and when it suddenly drops (when the stupid person walks into the laser beam) the Arduino says to its self  ‘Aye Aye, a stupid person just walked into my laser beam, I think I will tell that digi camera over there to take a picture of em’

The Arduino does this by making its digital pin 12 turn on, this sends 5 volts to one side of the opto isolator which in turn triggers the camera to take a photo.

So there you have it in a nutshell, if you are confused and feel the need for assistance understanding any of the above please feel free to ask me using the comments thingy you will find at the bottom of this post. Please note, I will be giving further details of how to connect all this up on a bread board and making a finished portable version with veroboard in future posts so you don’t have to work it out from this schematic

Next Part will detail a couple of sensors, laser trip wire and optical switch.

Tags: Arduino, DIY, Electronics, Photography

This entry was posted on Sunday, November 1st, 2009 at 1:26 am and is filed under Photography Tutorial. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.