some notes from where i left off with this project 6 months ago. basic design (hardware and software) strategy for all of the sensors for this project:
- sensor size should not be bigger than a small match box ("posporo").
- battery powered either using a 3v coin battery or 2 AA batteries.
- mcu and wireless chips to be on a separate board from the main sensor board. this will provide more flexibility during development and ensure a modular design of the hardware.
- sensor must work as a stand alone unit when not connected to a valid home automation system (HAS). additional hardware (light, sound, etc.) setup required to inform user of the change in the environment in stand alone mode.
- when connected to an HAS, the sensor initiate the communication with the host to send the data. host response to include parameter updates to the sensor in case there are changes.
- the sensor when active should only perform basic housekeeping activities (e.g. battery check, host check, sensor check, sleep setup) + send data to host if connected to a valid HAS.
- the only role of a sensor node is to detect a change in the environment and do the required actions with minimal processing to conserve power (target is 6 months before changing batteries) ... cheers
Boo!
while designing the photo sensor circuit, i missed out one functionality in my old notes, critical to any online system based on my experience ... the override function which is quite important to a user (me included 🙂 he he he) ... manual override to be precise for an HAS :-). it's human nature, at some point in time, users would always like a way to bypass the automation and be able to manually operate the unit for one reason or another ...
example: an outdoor light bulb controlled by an LDR sensor to switch ON at night and switch OFF during day time. what if ... during day time, gusto ng user to switch ON the light, just to check baka pundido na yun bulb 🙂 he he he. without a manual override function, it would be difficult for the user to do it and ma aasar lang siya na palpak yun design 🙂 he he he
a good design should, as much as possible, incorporate the manual override function into the normal process of a user using the unit. in the light bulb example, a household switch is normally use to manually turn ON/OFF the light. one good way to have a manual override in an HAS is to use the actual household switch as the trigger for the unit's automation - if it's in OFF position, then automation (HAS) is in control of the unit, if it's in ON position, then manual override is in effect (light bulb will turn ON no matter what is the situation) and automation is suspended. when the user turns OFF the switch (if it's day time, the light will be off, if it's night time, the light will still be on), automation will be in control again ... a very simple process, the tricky part is how to design the circuit to incorporate the said process 🙂 ...
last note, the above solution for a manual override function may not work for other sensors monitoring other units in the house, you just need to analyze the setup of the unit and then design the circuit to include a manual override that would be simple for a user to use ... cheers
Boo!
