Power and Data combined, Standards, (ie, USB, PoE) for an open source kit - Page 1
Forum section: electronics / beginners

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 03:42:42 am
content: Hi Guys,I wanted to create (or, I should say, "i would like created") a modular electronics system similar to the Inno-bits or Little-bits systems but for more "serious" purposes generally.I initially intended to have 3 main electrical systems, each using their own method of connection:Low Power system: Originally 12v ish DC (Connection undetermined) (I am currently leaning towards the 50v ish low amps Power Over Ethernet for this)- Toys, Lego like kits for younger kids, Cameras, LED lighting, LittleBits style stuff.Moderate Power System: 60v DC (Connection undetermined)- A range of open source power tools like mowers, drills, circular saws, impact drivers etc (yes I know, open source power tools, dreamland.. you never know though)High Power System: 240v AC (Using standard Australian 240v connections)- Standard mains power stuff, TV's, Kettles, etc etcConsiderations for me, for the systems are as follows:1: Would definitely like to be able to carry both electricity and data over the same cable2: Would like to be able to carry data without (much) electricity in the cable3: Would like waterproof and weather resistant connections to be available4: Would like to be able to carry reasonable amounts of electricity over the systems5: Do not want to be range limited prior to 30 meters (ie, USB is pretty well ruled out with 2 meters range)6: Would definitely prefer standards that already exist, pretty sure I don't have the ability currently to create a new standard7: Would like as much inter-operability between the 3 power leveled systems as possible.My thoughts so far are as follows:Low PowerFor the low power system I have considered:1 - Spade bit connectors. I dont really like them because they are exposed. Do not carry data.2 - Power over ethernet. My current favorite solution. Carries data and power. Carries enough power for the low power systems. Higher voltage (40-60v) than I initially intended, but any modules on the system should be able to convert this? not 100% sure about this or how affordable this would be. I also believe electronics modules can be wired in such a way to allow data to transfer through them even if the power has been cut off.3 - USB - pretty much ruled this one out due to range limitations, though it would have been really nice because of how popular it already is. Maybe it could be used with adapters that allow for the range (ie, USB to Ethernet adapters) and then converts back to USB at the other end.Moderate PowerI have no idea what to do about the moderate power system at the moment.High Power- Not going to try and change from the standard Australian plugs, however data is an issue. There is power-line communication available for 240v however I believe shutting off the power will also shut off the data. I could use this in conjunction with the low power system to transfer data, however, that means running 2 cables to get power and data to a module which is something I really want to avoid. Ideally I would create a brand new system that is the same as 240v but has a fibre optic cable built in to transfer data as well.Later I would like to have an even higher power system for a decent sized electrical mulcher/chipper and firewood processing stuff but I cant worry about that at the moment (400v ish 3 phase probably)So does anyone have any thoughts or recommendations? Are there any existing standards I dont already know about that may be suitable?Thanks very much guys.Btw, my current electronics level is very much beginner hence I posted this here not in the open source section, however obviously i'm going to have to learn some things between now and when this system is operational, so you may see a lot of me around here asking very "basic" questions soon so please be kind

author: Ammar
author_rank: Regular Contributor
timestamp: October 16, 2016, 04:02:31 am
content: Yes, you can indeed transmit data over mains lines. This use to be a done a lot and is still used in some applications. It is typically modulated at a higher frequency than the 50/60Hz mains sinusoid and filtered using a high pass filter to remove the 50/60Hz and leave the data.

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2016, 04:20:23 am
content: The relatively high voltages permitted by POE + the exposed pins on the plug would be hazardous for toys.USB Full speed (12Mbit/s) has a max length limit of 5m. You have to allow a bit for wiring inside cases etc. but 4m links are practical. In many cases a 5m extension cable will also be 100% reliable. There are also USB extender systems available that can run up to 100m over Cat5 cabling and supply 500mA remote power.For high power stuff you'd want something like IEC 60320 C13 and C14 connectors as found on PC PSUs or C15, C16 as found on most electric kettles, as that's an international standard. Using Australian connectors kills any chance of an international market.You aren't going to be able to legally combine power and data at any voltage over 50V except by off-the-shelf powerline Ethernet without going through a *VERY* expensive certification process due to Australia's draconian electrical safety regulations.

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 04:39:22 am
content: Quote from: Ian.M on October 16, 2016, 04:20:23 amThanks Ian1 Question: the 500ma remote power for USB at 100m, Is that at the 5v USB voltage or the 50ish V PoE voltage?Very good point about the Australian Standard plug vs the "Kettle Cord" type plugs. I think I will adjust my plans accordingly.Also very good point regarding the PoE's exposed pins and voltage, however, I believe that PoE can/is set up on a "on demand" system, so power isn't sent until requested, but, that fact also means that I assume I would need some kind of chip in there to request power for every module I create, and i'm not sure how expensive and/or complicated that would make everything. I will have to do some research, or if anyone on here knows and would kindly like to tell me that would be great

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 04:57:07 am
content: Quote from: Ammar on October 16, 2016, 04:02:31 amThanks,Looks like Netgear makes something that does this up to 1000mbs, however it would still be a 2 plug affair if you needed both power and data into a device, but it is good to know anyway, and it means it must be possible to create a device that can accept the power and extract the data out in the one device as well.

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2016, 05:03:32 am
content: That's 5V 500mA at the far end USB port. All standards compliant USB extenders >5M have to be active devices so identify as hubs and its not uncommon to have more than one port at the far end. Good quality Cat5 cable is 24 AWG so a 100m run has a resistance of a bit under 8.5R per wire. Assuming two ports, and two pairs used for power, more than 14V has to be supplied to allow regulation to 5V, 2x500mA at the far end. I suspect that most commercial products will resemble POE and use >18V over the cable with a PSU at the host end and a switching regulator at the far end. Single port USB extenders or ones only rated for shorter distances may use lower voltages, but even at 10m you'd have to boost the voltage to reduce losses. If you want something odd-ball like a remote powered remote host, you are probably FUBARed without a lot of hackery, or going POE with a USB over Ethernet hub at the near end.

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 05:53:31 am
content: Quote from: Ian.M on October 16, 2016, 05:03:32 amOK thankyou.I think USB overall is a bit under powered for what I want to do and am going to continue at the moment with PoE as my low power system but that exposed connector thing you pointed out has thrown me a little, and there's still the issue of most PoE not sending power until it has been told to do so, and then having to convert back to 5v or 3.x volt to power circuits and stuff for every circuit.... but I don't think anything there is totally insurmountable. Also given the low amps I dont think PoE would seriously injure anyone just give them a bit of a zap, maybe?

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2016, 06:44:15 am
content: Quote from: Anyone Can Build on October 16, 2016, 05:53:31 amThat depends - I'd be a lot less worried about a toddler sucking the end of a USB lead than a POE Ethernet cable - neither is ideal, but the max. POE voltage is sufficient to drive a lethal current through their chest if they are on a damp grounded conductive surface, + the grounded USB shell would divert most of the much lower current 5V could drive.Very few children's toys have more than 15V at a couple of amps on exposed terminals (think train set), so unless you want to drop the idea of toys or do a LOT of safety research, if I were you I'd scale back my 'low power' ideas a bit.

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 07:54:29 am
content: Quote from: Ian.M on October 16, 2016, 06:44:15 amI guess using PoE I dont have to always use full power, for childrens toys I could drop it down to 12v or so (there is a PoE injector by.. D-link? someone anyway, that allows you to switch injection voltages 12, something (24?) and 48). Cables etc would all still be interchangeable.

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2016, 08:36:59 am
content: Ethernet adds a lot of complexity to each device, and POE adds even more. It also adds major security concerns if you use any routeable protocol, and if you use raw packets, rather than TCP/IP, consumers wont understand why they cant run it over a WiFi link.Possibly the best option for the toys would be 12V 1A power + a RS485 serial network over 4P4C modular connectors and 4 core UTP wiring (or 'silver satin' for short flyleads).You cant go much over 12V without risking blowing the RS485 transceivers if there is a short. Each device except the master would have a pair of ports for daisy-chaining, electrically in parallel, and the last device in the chain would need a terminator plugged into its spare port.

author: Anyone Can Build
author_rank: Newbie
timestamp: October 16, 2016, 09:23:39 am
content: Quote from: Ian.M on October 16, 2016, 08:36:59 amI haven't given security any thought as yet to be honest.I believe (though im not yet positive) both InnoBits and LittleBits modules are compatible with each other and they are using the RS485 protocol, and I did want my bits to be compatible (after applying relevant voltage/power considerations, ie, they would be able to communicate but would require power transforming adapters between them) , thus, I would end up using RS485 too.

author: grifftech
author_rank: Frequent Contributor
timestamp: October 17, 2016, 02:38:28 pm
content: american 4 pin dryer plug