Photography Project : Intervallometer + Wireless Remote Shutter

Hello,

As a total beginner in electronics, I would be interrested in having your enlightened opinion, with one main objective in my mind : not to fry my arduino the first time I flow current through it ! (I’d rather wait the second or third time XD). I know it is generally preferred to have practiced a bit before posting, but I am not yet equipped (it is a matter of days), so it is all done mentally for now !

You will find below my preliminary schematics for a personal project concerning photography, which consists in :

  • taking an indefinite number of photos at a regular frequency OR
  • taking one photo when a remote trigger is pressed

The components are :
a) Arduino Uno Rev3
b) Servo : Tower Pro SG90
c) Radio receiver : based on chip SC2272-M4 (some background here for instance : http://dzrmo.wordpress.com/2012/07/08/remote-control-pt2272-for-android/)
d) 24-step rotary encoder, which is also a button
e) Standard backlit LCD screen (some doc here : https://boutique.semageek.com/fr/index.php?controller=attachment&id_attachment=23)
f) Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5, which I will feed with 2 or 3 NiMH AA batteries

My only question is :
Is there any major problem with my design = will it run safely ?

Well, while I am at it I do not mind some counselling on the following : :wink:

  1. If it is OK, I will then play around and test the benefit of adding some extra “protection” : decoupling the source with capacitors, adding a flyback diode across the servo, handling the encoder rebounds with capacitors is mainly what I thought of.
  2. After I could measure the current draw (I anticipate between about 100 mA and 250 mA), I would like to reduce the energy needs of my circuit (by hardware I mean, software will be “optimized” from the start). I thought of driving the radio receiver, the LCD backlight and the servo with MOSFETs. It is a good idea, and are there some things to know before I make some tests ?

Thank you in advance for your advice

I would stay away from D0 and D1 as they are used by USB to upload your sketch. Also by the serial monitor.

I suggest that you start developing your project without the LCD and only add that in when everything else is working. If you need help with your code from the forum it is usually much easier to understand code that isn't cluttered with LCD stuff. Just use the Serial Monitor for output in the early stages of development.

Also start with separate small sketches that each focus on one item - servo, wireless, encoder etc - while you learn how to code it. When each of them is working you can then combine them into your project.

...R

steinie44: I would stay away from D0 and D1 as they are used by USB to upload your sketch. Also by the serial monitor.

Okay, I will ! (my only obligation is to use D2 and D3 for interrupts on the rotary encoder and the radio receiver)

Robin2: I suggest that you start developing your project without the LCD and only add that in when everything else is working. If you need help with your code from the forum it is usually much easier to understand code that isn't cluttered with LCD stuff. Just use the Serial Monitor for output in the early stages of development.

Also start with separate small sketches that each focus on one item - servo, wireless, encoder etc - while you learn how to code it. When each of them is working you can then combine them into your project.

...R

Thank you for the advice (this is indeed how I planned to proceed). Makes me think of a basic question by the way : how do you visualise electronic signals (tension/current) on an Arduino-based circuit ? I want to check for transient peaks (for instance when I turn the main switch on, or when I power off the servo). I have seen some "poor's oscilloscope" solutions on the net, are they recommended (I have a spare Trinket) ? Or would I rather buy a cheap scope ?

As for the rest, I am going to test all of it without extra components and see what happens. As far as I know, I can still fry my boost converter just by reversing my batteries polarity... No pain no gain !! :grin:

gromk: how do you visualise electronic signals (tension/current) on an Arduino-based circuit ? I want to check for transient peaks (for instance when I turn the main switch on, or when I power off the servo). I have seen some "poor's oscilloscope" solutions on the net, are they recommended (I have a spare Trinket) ? Or would I rather buy a cheap scope ?

If you use a suitable voltage divider to ensure the voltage stays between 0 and 5v you can measure voltage with the Arduino ADC. I think the maximum sample rate at full 10 bit resolution is about 15,000 samples per second and up to 76,900 at lower resolution according to the Atmega 328 datasheet.

I recently bought one of these DSO Quad oscilloscopes and have been quite happy with it. I don't use it very much and I could not justify spending more on a better one. There is a long discussion about it here - with at least as much heat as light :)

...R