AVR-Chat

Just a thought ... you can maybe use an implementation of X-10 technology 
and power your devices at the same time. But you'd have to use AC to power 
your devices.

There is a whole set of documents at the Microchip site about implementing 
X-10 with PIC's, including one on powering them directly off 110vac lines.  
I should think it can be done similarly with AVR's. There's no reason a 
lower voltage than 110 volts can't be used. (See below)

Zack


On Tue, 1 Feb 2005, Chuck Hackett wrote:

> I'm looking at developing a signaling application for 1.5" scale ride-on
> railroads (a hobby of mine).  It involves a long signal bus (up to a couple of
> thousand feet) based on RS-485.  I'll also need to run power to operate
> ultra-bright LEDs as well as intermittently drive a couple of low voltage, low
> power electric motors.  The cables will typically be buried along the track.
> 
> My design will involve and AVR-based module at locations along the track to
> detect trains present on a section of track, signal other modules about track
> occupancy, drive local signal (light) heads and possibly low voltage motors to
> move throw track switches.
> 
> As I see it, I'll have to bury two cables along the track, one for power, and
> one for the RS-485 signal bus (either 2-wire or 4-wire with signal ground to
> control common-mode voltage differences).
> 
> My question at the moment is what is the best way to power the devices along the
> network.  I don't expect a large current draw at each location (module power
> plus several ultra-bright LEDs on at once) and at locations that have small
> intermittent motors I could place a small rechargeable battery to take the surge
> and trickle charge it from the power bus.  Some thoughts:
> 
> 3) Something like 48 VAC.  Easier to step down to a reasonable level but I fear
> having a transformer, etc. at each module would increase costs too much.

You wouldn't need it.  See the Microchip Application Note AN236 and think 
about AVR's.

http://ww1.microchip.com/downloads/en/AppNotes/00236a.pdf

> 
> I'm looking to keeping module costs as low as possible and still have a reliable
> system.
> 
> Comments?  Other ideas?
> 
> Cheers,
> 
> Chuck Hackett