Wednesday, December 10, 2008
Following on from my successful 240V project, I designed a board to attach to the NGW100 and drive up to 8 relays.
The form factor for the board was dictated by the placement of the J5 and J6 jumpers on the NGW100, so there was a lot of spare board area.
So the logical thing to do was stuff in just about everything thing else I could think of that I ever interfaced to the NGW100. Which is why there's also 8-channel 1-wire interfaces, an SPI interface, and an RS-485 half-duplex driver.
The silk screen lists the RS-485 driver as the MAX-487, but it's really the equivilant 3.3V part. (I got lazy and skipped making a custom part in the library for it).
This board will plug straight into the NGW100, picking up all the signals from J5 and J6, and picking up supply power for the relays from J15, being the pre-DC/DC voltage.
This means that I can supply the NGW100 with 12VDC, which the onboard dc-dc convertor will drop down to 3.3V for the ARM32, and the daughterboard will take directly as 12VDC for the relay driving, but 3.3V for the SPI, 1-wire, and RS485.