This isn't homework but it's something I'm trying to build. Basically I'm making a panel to power POE devices and get some information. Here's the plan.

I'm going to power approx 24 devices that range from 25' to 250' from the power source. I want to power all of these from a central location that can switch between 24v and 18v depending on the distance (my devices require between 12v and 18v to operate.

I want to be able to read the current consumed by each of my devices. I'm thinking a HALL Effect Sensor will do the trick here and I can read it with either a PIC + Ethernet chip or an Arduino.

I would LIKE to have a LED light that tells me the circuit is operating (not just the switch is on)

I would LOVE it if I could figure out how to have another warning light if the voltage drops below 13V

This is my circuit so far. http://anders.finn.ws/images/misc/panel.png

Any help is appreciated

 

ok, so here's what I THINK is happening. I'm ignoring the HAL effect sensor as it has little or nothing to do with the circuit current wise.

Resistors are used to symbolize the long wire runs and the load.

- Long wire runs are shown as var. resistors with resistances taken from http://www.securityideas.com/howtocalvold.html given a 2A load (which is what I think I'm going to use)
- Devices are 5.5 - 15 watts depending on the device I throw out there. They have voltage tolerance between 12-18V and have worked fine from 0.5-2A. (least they're easy to work with)
- I've included my calculated line voltages as min (assuming maximum wire run (resistance) at 24V) and max (minimum wire run (resistance) at 24V).
- 18V is only used for shorter runs where 24V is not necessary to achieve a minimum of 12V across device (aka about 150')