Basically, the 'gist' of the project: You send the Imp a value (0-255 decimal or FF Hex) and it sends that stream of bits out of the UART serial port (pins 1 and 2). The TI chip can only receive bits, so Imp pin 2 (RX) is not used. The TI chip converts that serial input into 8 digital outputs. Electronically, it can turn ON or OFF any of the Solid State Relays.
The TI chip is addressable, 0-7 using 3 bits. That means you could technically have up to 8 of them in a line to drive 64 digital outputs. The scope of this Instructable does not include extending outputs beyond one chip. Also, the TI chip only receives serial bits and does not send any data back. For bi-directional UART, you would need to use a different method.
I selected this TI chip because it doesn't need a clock. It synchronizes automatically based on the timing of the first start bit. This makes the circuit super simple and easy for anyone to construct. No oscilloscope or logic analyzers needed.
This Instructable does not describe how to commission an Imp. You'll need to view the Electric Imp website (www.electricimp.com) to learn how to register, login, commission, and create an account for your imp.
If this is your first encounter with the Imp ... please see this Instructable first:
The main parts:
Everything except the solid state relays can be built for under $100USD.
- Plastic box that can withstand outdoor weather.
Use plastic because of the imp inside ... WiFi reception.
I used an old cheap plastic toolbox. Waterproof, w/carry handle.
- Electric Imp
Sparkfun Cat No. WRL-11395 (approx $30USD)
- April Electric Imp breakout board
Sparkfun Cat No. BOB-11400 (approx $13USD)
- TI (Texas Instruments) Serial to Parallel chip:
Mouser Electronics Cat No. 595-SN74LV8153N (approx $2USD)
- Blank project board for soldering parts onto
Mouser Electronics Cat No. 782-T030081 (approx $5.50USD)
- 7805 5VDC Voltage Regulator
Mouser Electronics Cat No. 595-UA7805CKCT (less than $1USD)
- Solid State Relays (SSR)
3-32VDC input ... 120-240VAC output
These are expensive, but you can find used ones on Ebay
- Misc LED, resistors and capacitors, solder, hookup wire