Half-newbie needing advice... Looked through quite a lot of the backlog in the forum, but didn't find what I was looking for. Sorry if I've overlooked something, if so, just point me in the right direction and I'll be on my way..
So, here's my project:
I'm working on a sound-installation for a cable-stayed bridge. One of the things we're looking to do is use an accelerometer to sample and record the movement of the cables and play this back at a higher pitch. Due to their length (100 - 300 metres), the built-in high-pass filters in most audio-preamps would remove all the information we're looking for, since the oscillations in the cables are at as low frequencies as 0.2 - 1 Hz. We've been testing using an Arduino UNO and 3-axis +/- 3 g accelerometer, and it works fine. For the finished installation, however, size is of great importance, as we need the sensors to be visually unobtrusive. Hence, I want to use the Arduino Mini. Also, due to the sheer size of the bridge, connecting the Arduinos via USB is not possible. Because of this, I've been looking into creating a design that would let us power the Arduino and send all data using just a regular Cat5 ethernet-cable. (Getting to the actual question, now.. ) Could this be done with the PoE-module for the Arduino Ethernet, and if so; how? What components would I need for this to work?
from my understanding of PoE and trust me its a basic one most devices use the telcoms standard of 48 volts for there power supply, im fairly sure the arduino your looking to power would not be very happy with this voltage, but with a bit of hacking and poking around im fairly sure its do-able.
first off would be to establish if the ethernet shield uses the pins in the ethernet plug that PoE uses to provide power through, if there free and not connected to anything on the board (this is important if there being used its not really possible or if there connected to anything on the ethernet board you chance frying the board),
Then it would be a simple case of making an "add-on / soldered together" power regulator from the pins of the ethernet shield that provide PoE (might invalidate your warranty mind you) that takes the 48v PoE supply drops it down to 5 or 12v and just wire that into the power socket on the arduino. at that point you should be good to go.
if this is'nt the case and my last few sentences are total rubbish please feel free to let me know lol as this is all in the realm of guess work for me as i don't own an ethernet shield at the mo
Hi Kris, thanks for the reply.
What you're saying makes a lot of sense, at least within the boundaries of my limited knowledge. However, I don't think we're quite on the same page, which I guess is my fault for not being particularly clear in the first post..
I'm not thinking of using the Ethernet shield. I was thinking of the PoE breakout-board for the Arduino Ethernet (which is basically a Duemilanove with an integrated Ethernet shield). Dunno if that's at all clarifying for you, or maybe I'm just flaunting my own incompetence, and you were actually talking about the same thing, and I just didn't get it..
SohnSonic:
Hi Kris, thanks for the reply.
What you're saying makes a lot of sense, at least within the boundaries of my limited knowledge. However, I don't think we're quite on the same page, which I guess is my fault for not being particularly clear in the first post..
I'm not thinking of using the Ethernet shield. I was thinking of the PoE breakout-board for the Arduino Ethernet (which is basically a Duemilanove with an integrated Ethernet shield). Dunno if that's at all clarifying for you, or maybe I'm just flaunting my own incompetence, and you were actually talking about the same thing, and I just didn't get it..
Hi SohnSonic, its my fault as well to be honest as i wasnt aware of the arduino Ethernet from the looks of the device on here
it looks like you would have no problems running it via PoE using the additional PoE module, according to the data on the page
The optional PoE module is designed to extract power from a conventional twisted pair Category 5 Ethernet cable:
IEEE802.3af compliant
Low output ripple and noise (100mVpp)
Input voltage range 36V to 57V
Overload and short-circuit protection
9V Output
High efficiency DC/DC converter: typ 75% @ 50% load
1500V isolation (input to output)
heres a copy of the datasheet that was linked from that page as well, ive had a bit of a google and sadly cannot find anywhere that stock or sell this module.
however they do offer some very good diagrams on what the pins do and how it works so it might be an easy job to make one. hope this helps
) Could this be done with the PoE-module for the Arduino Ethernet, and if so; how? What components would I need for this to work?
most devices use the telcoms standard of 48 volts for there power supply, im fairly sure the arduino your looking to power would not be very happy with this voltage, but with a bit of hacking and poking around im fairly sure its do-able.