Thursday, June 7, 2012

G8P Relay Controller Part 2

Well I sent my boards off to the Fab shop, so hopefully they'll be in sometime next week.

In the meantime, Ive started coding for the board to control the relays remotely. I've also begun work on the Relay control library to make coding a lot easier. The goal is to get a VB GUI program to interface with the relay controller to flip relays on and off. If that works, then the I'll try to make a Web server PHP script to control the relays remotely. As much as it is nice to have control over lighting at each station, the end goal is to interlink all these relay boards so that the Smart Home system maintains each system rather than the user. I've already begun making plans to make the next revision of these boards XBee Wireless.

For the moment, I see a great need for single and dual relay controllers, but not so much for triple, quadruple or more relays per board. However, if the need arises, I can design larger sized relay controllers. Most people have one lamp here and another there; some just want control of their ceiling fans and lights. While the initial revision is dual relays, I see a future for making single relay boards. 

I've decided to say a little bit (benefits) about why I've selected the Omron G8P Automotive relays:

First, theyre capable of handling high currents at high voltages. An SPST relay can handle 30A at 220VAC, while an SPDT can handle 20A at 220VAC. That goes a long way for controlling devices in a home.

Second, there are quick connect pins on the top of the relays, which allow an electrician to use quick connect crimp connectors to wire each relay into a lighting circuit. This is beneficial, since they most electricians are already aware of this connector, and probably stock up on them. 

Third, the PCB board doesnt have to account for high currents running through it, so price of fabrication is lower, and thus price to sell a controller is lower. This is more a technical aspect, but its important for the user in that theres less of a chance of a fire in case of failure of the PCB. Fourth, these relays are already being used on production lines in manufacturing facilities and in automotive applications. They've proven their worth and their reliability. I can say from experience using these relays before in a couple of projects, that they never let me down. 

So benefits all the way around. Finally, there's only one company I'm aware of that sells relay controllers with G8P relays. As their pricing stands today, the boards are way over priced, and totally unaffordable by electronic hobbyists. The plan is to make my boards affordable, and still try to give the same range of features. 

Monday, June 4, 2012

G8P Relay Controller

Well I've been developing a dual relay controller board for use with my Smart Home system (its meant to be controlled via the Beagle Bone or Raspberry Pi). Its somewhat based on the NCD USB Relay board, but I've changed a few things and made it smaller. Trust me, my board looks nothing like theirs.

I wont go into too many details until I've gotten the board fabricated, assembled and tested. For now, I'd like to highlight some specs and code. The benefit of this board is that I've decided to embed a Teensy microcontroller into it, which means that this is a USB-to-Serial Relay board. So the Teensy is powered via USB. The relays however, will be powered via a 12VDC adapter. The relay power supply is separate from the Teensy power supply.

There are two Quick-Connect Contact G8P Relays on board. If I decide SPST, its rated at 30A at 250VAC, and if SPDT, its rated at 20A at 250VAC.

For reference, here is the ASCII byte command chart:

//The first is the command mode byte (not implemented); The second is the command byte. 

          (254),0-1 Turn ON Individual Relays
          (254),2-3 Turn OFF Individual Relays
          (254),4-5 Get the Status of an Individual Relay
          (254),6 turn all on.
          (254),7 turn all off.