Infrared ethernet to ethernet bridge  - Page 1
Forum section: electronics / general

author: ilikepez
author_rank: Regular Contributor
timestamp: February 03, 2012, 04:13:40 am
content: I need a ethernet to ethernet bridge that is Infrared. Doesn't have to be very fast or even long range (3-5 feet). I can't build it myself as I need to have 48 of them. I've done a ton of google searches but all I can find is networked infrared remote controls for stereo systems.Any help would be great.

author: nitro2k01
author_rank: Frequent Contributor
timestamp: February 03, 2012, 04:28:06 am
content: Could you give more details? What kind of traffic is it that you want to transmit, exactly? I don't know what you want to do, but I strongly suspect there are better solutions to what you want to achieve. The bandwidth you can squeeze out of open air IR isn't exactly all that great. And I'm certainly hoping you don't want to have 48 of these in the same room or transmit between two windows through an outdoor distance.I think first you should look at wifi solutions. Secondly you could look at a microcontroller that connects over ethernet and tunnels traffic through IR (yuck) or Zigbee, both of which will offer very low speeds compared to the 10 Mb+/s that ethernet offers. If you can make whatever you want to communicate, communicate over a serial port, that would simplify the design. But again, more details, please!

author: Psi
author_rank: Super Contributor
timestamp: February 03, 2012, 04:28:31 am
content: I'm not 100% sure i understand what you want but...What about an ethernet to fibre converter. They operate at ~infrared and, with a lens on the tx, you might get them to work at 3-5feet in open air without any fiber optical cable. (just pointing at each other).

author: ilikepez
author_rank: Regular Contributor
timestamp: February 03, 2012, 05:29:39 am
content: Its for a crane that has to be have a rotating cab and tool mounting, the cab is suspended under the bridge and we want to add remote I/O to the cab. We have a slip ring for power, and the company that supplies us the slip-ring has one for ethernet that would work. Unfortunately it would cost a lot and take several guys a day or two to install. The speed is not very important.The PLC is an AB SLC-500 and its a fairly simple task for us to set up the remote I/O using ethernet so I would like to stick to that if possible. The transmitter and receiver will both be inside the same metal hull for lack of a better term. We would use a wifi connection but the company has pretty strict rules for that and it would drive up costs considerably.Its for the company my dad works at, and we are brain storming solutions for fun and as a mental exercise. If we got something cheap and reliable he might get the go ahead to do it but they don't like change there at all.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 03, 2012, 09:21:22 am
content: RF would be a much better solution than IR, as the latter will be subject to dirt etc.Wifi of some sort would seem the obvious solution.

author: caroper
author_rank: Regular Contributor
timestamp: February 03, 2012, 11:10:47 am
content: I would think this must be an RF solution.If one end is rotating relative to the other how would you keep the Optics pointed at each other?

author: kaz911
author_rank: Super Contributor
timestamp: February 03, 2012, 11:11:39 am
content: Normally PLC type installations would use MODBUS for control - and there are plenty of MODBUS to wireless systems - some open - some closed (secure). And then you can have a MODBUS to IP converter at the endpoint.Check DIGI Systems MODBUS solutions. But modbus is not cheap.I do not think ETHERNET via IR would work even at small distances. But Serial -> IR would be a lot easier. But I would look at a custom RF solution - maybe based on TI CC3000 series.

author: G7PSK
author_rank: Super Contributor
timestamp: February 03, 2012, 12:33:59 pm
content: Is the power slip ring AC or DC and at what voltage. You might be able to use something along the lines of a homeplug which is basically RF over the power lines.

author: amspire
author_rank: Super Contributor
timestamp: February 03, 2012, 01:09:42 pm
content: You could use infrared comms for RS232 serial. Probably at a slow rate like 50kBits/sec.You could use the ppp protocol (serial Ethernet like modems use), transmit the serial ppp across the RS232.

author: sonicj
author_rank: Frequent Contributor
timestamp: February 03, 2012, 01:20:17 pm
content: its definitely possible... this box + it's mate facilitated a bridge consisting of four T1's at a distance of roughly 26 miles. not totally sure what's inside... yet!-sj

author: kaz911
author_rank: Super Contributor
timestamp: February 03, 2012, 01:35:16 pm
content: yes - but that is not on the cheap ...:-)

author: sonicj
author_rank: Frequent Contributor
timestamp: February 03, 2012, 11:56:52 pm
content: Quote from: kaz911 on February 03, 2012, 01:35:16 pmdepends on your definition of cheap... this system came from a now defunct major USA cellular provider. they were interested in the technology because it would save them from leasing dedicated lines from the phone company or using up costly microwave bandwidth. so while this hardware was likely astronomically expensive from a consumer standpoint, it was actually a cheaper long term alternative for the cell phone provider.ok, i just read most of the thread.... might want to give a look at Futaba's line of industrial RF controls.Linklikely expensive as well, but then again, OP isn't interfacing some crappy little arduino-bot in the kitchen.-sj

author: ilikepez
author_rank: Regular Contributor
timestamp: February 04, 2012, 12:25:46 am
content: I'll look into the futuba stuff. In the center of the slip ring we have an open space, and the plan was to fix the IR transmitters at the top and bottom of that open space and point them at each other. The ethernet slip ring would cost roughly $10,000 per crane. So less then that would be great.@ampspire do you have a link to a RS-232 IR unit? 50 kbits would be plenty really. We are only using about 30 discrete controls and a few sensors. Maybe adding some indicator lights later. Nothing particularly high tech.Here is the best picture I could find of the crane we use:

author: amspire
author_rank: Super Contributor
timestamp: February 04, 2012, 01:47:33 am
content: If this is in a factory with lots of cranes, welding, molten metal perhaps, I think you better forget about bi-directional IR. It would be a very IR unfriendly environment.The thing to look for is probably serial to IrDA converters - IrDA is an IR link designed for PC's. However it was always a failure because it just never worked well at all. Most of the links will be designed for short distances in an office environment, and you have the extra problem in that the IR unit on the crane cannot point at the fixed IR unit.Now Ethernet is bi-directional. This is a really important question - do you need bi-directional communication or just one-way data from the crane to you? If you can use a one way communication, then you may be able to mount transmitting LEDs all around the cab, so that a receiver pointing at the crane is always pointing directly at a LED. In this kind of scenario, all the data is continually sent out in a loop, so it is not dependent on perfect communications. If it misses the data this time, it can get it again later. If you need every byte of data to get through without being lost, then I think forget IR.I suspect even if you base this on a commercial product, it will have to be modified. You may have to take a device with a single low power IR led, and replace that with multiple high power LEDs.It could be that at the end, you just have to decide that the job has to be done properly with something like the Ethernet slip rings. In industrial settings, half baked solutions usually just end unhappily.Richard

author: mobbarley
author_rank: Regular Contributor
timestamp: February 04, 2012, 01:54:53 am
content: sounds like an application for tcp/ip over bongohttp://eagle.auc.ca/~dreid/

author: Jimmy
author_rank: Regular Contributor
timestamp: February 04, 2012, 02:42:04 am
content: just us ab remote io and an wifi Ethernet orhttp://www.n-tron.com/products_detail.php?product=55&series=5orhttp://ab.rockwellautomation.com/Networks-and-Communications/Wireless-Solutions

author: caroper
author_rank: Regular Contributor
timestamp: February 05, 2012, 12:28:43 am
content: Quote from: ilikepez on February 04, 2012, 12:25:46 amEven with an open space you still have one end of the link moving with respect to the other so unless you have a ring of IR Tx/Rx modules on one side you will still have a problem.Thinking out side the box though, if you have a gap in the center of the slip ring the relative distance traveled may be small, how about a coiled cable, similar to those used on Telephone Handsets. As long as the crane is not doing 360 degree movements it may be a quick and easy solution.CheersChris

author: ilikepez
author_rank: Regular Contributor
timestamp: February 05, 2012, 04:02:38 am
content: The crane has to rotate infinitely. We can't use wi-fi because of company restrictions on wireless control devices. We need bi-directional control, the major advantage of using the remote I/O was that we could add a number bunch of indicator lights.Thanks for the suggestions guys. I was hoping to find a alternative to that slip ring but it looks like there really isn't much out there.

author: kaz911
author_rank: Super Contributor
timestamp: February 05, 2012, 07:05:21 am
content: Quote from: ilikepez on February 05, 2012, 04:02:38 amWhat are the restrictions? Cant use WiFi - or cant use any wireless device? And what types of "interface" do you have on the PLC control box apart from Ethernet?

author: Polossatik
author_rank: Frequent Contributor
timestamp: February 05, 2012, 08:06:13 pm
content: not sure if it's usefull, maybe using ppp over infrared and a mini linux install ?like using some kind of mini computer with IR and Eth ? something like a beagleboard or so?

author: ilikepez
author_rank: Regular Contributor
timestamp: February 06, 2012, 01:25:26 am
content: What are the restrictions? Cant use WiFi - or cant use any wireless device? And what types of "interface" do you have on the PLC control box apart from Ethernet?We can't use wifi. We do use radio control for some functions of the crane already. The PLC has ethernet and rs-232.

author: kaz911
author_rank: Super Contributor
timestamp: February 06, 2012, 03:43:13 am
content: you can find quite cheap RF -> RS232 bridges.http://www.alibaba.com/product-tp/12315482/RS232_to_RF_Converter_RDSRF_232.htmlThe above is 433 MHz so not WiFi. And you can get it at many frequencies.The one on the link is just an example - there are many more.

author: amspire
author_rank: Super Contributor
timestamp: February 06, 2012, 04:18:17 am
content: Quote from: kaz911 on February 06, 2012, 03:43:13 am433MHz modules are available extremely cheaply, but ilikepez has saidQuote.Also bidirectional communication is definitely needed and it sounds like a site can have a number of cranes. wi-fi or bluetooth would be perfect solutions if they were allowed because they don't have an interference problem from other cranes on the same channel.IR is technically possible, but it is hard to find an off-the-shelf solution that would work well. Most IR links are for short distance communication using directional transceivers.There are devices like the Netgear range of Ethernet over the mains power circuit.http://www.netgear.com/service-provider/products/powerline-and-coax/powerline/default.aspxThey have a range of speeds from 85Mbits/sec to 500Mbits/sec, and they start off pretty cheap.I have only seen these work as a 1:1 connection, so I am not sure how it would go with multiple cranes on the same switchboard circuit. Also they typically can only work on a circuit up to 240V and so they are probably no use on a 415V 3-phase circuit. (Any mains transformers kills the signal).Also it probably wouldn't work well if there is a lot of noise in the power slip-rings as they rotate. Could be worth a try though. To isolate different cranes interfering with each other, is may be as simple as adding an RF filter in the supply to the crane.Richard.

author: sonicj
author_rank: Frequent Contributor
timestamp: February 06, 2012, 06:35:38 am
content: Quote from: ilikepez on February 06, 2012, 01:25:26 amUbiquiti makes some 900MHz equipment that would suitable for a wireless ethernet bridge. its not "wifi" & its purdy cheap too!RS-232 over bluetooth is easy withRoving Network's RN-41. Error correction, pairing, no stack to maintain, very good range.... basically, its a like 'plug-n-play' serial cable replacement.-sj

author: kaz911
author_rank: Super Contributor
timestamp: February 06, 2012, 08:56:15 am
content: Quote from: amspire on February 06, 2012, 04:18:17 am433Mhz is not WiFi - and they already use some wireless control system. I think they cant use normal WiFi due to security issues. Custom RF bridges should not be an issue.

author: ilikepez
author_rank: Regular Contributor
timestamp: February 07, 2012, 02:44:24 am
content: I'll check out the netgear stuff and the run the other wireless options by the IT guy. All of the 120v power in the cab is provided by an isolation transformer so it shouldn't be much of a problem. Thanks again! It looks like we have some pretty decent options to move forward with.

author: amspire
author_rank: Super Contributor
timestamp: February 07, 2012, 02:56:36 am
content: Quote from: ilikepez on February 07, 2012, 02:44:24 amIf each cab is powered via a separate 120V isolation transformer on the ground, that is perfect for the Ethernet over mains units. The signal will stop at the transformer. I think is is worth a try. May be worth adding a surge arrestor across the 120V in the cab.The devices like as direct a connection to the main power cable at both ends as possible. Even connecting through a mains extension cord can cause enough of an impedance mismatch with the two different types of wiring that it cannot compensate.

author: Unknown
author_rank: Unknown
timestamp: February 07, 2012, 05:35:49 pm
content: Quote from: kaz911 on February 06, 2012, 08:56:15 amDo you really want to use consumer equipment for industrial control applications? I've worked with people doing industrial WiFi, and they all disliked home/office equipment for anything important. This may be partly due to NIH, however.Quote from: kaz911 on February 06, 2012, 08:56:15 amThat's just stupid. WiFi security, while not perfect, is at least under a lot of scrutiny. A lot of time has been spent by people trying to find flaws, and even if a flaw is found, at least it's published widely so you can apply a fix or workaround. A random custom RF protocol is almost guaranteed to be less secure against competent intruders unless it was primarily designed for security. If someone finds a flaw in a proprietary RF protocol, it may not get published outside of cracker circles. There are industrial WiFi and other RF bridges by companies like Elpro, this would be the place I'd start.

author: benemorius
author_rank: Regular Contributor
timestamp: February 07, 2012, 09:18:53 pm
content: I've extended an rs485 modbus connection to a plc over a 433mhz radio link with great results. One thing you really have to watch out for is that modbus uses idle slots to delineate messages. I first tried an off the shelf bluetooth link, but that completely failed because the radios would only transmit in bursts and the idle time between bursts split up the modbus messages inappropriately. Of course you can add some logic to buffer each end and send only whole messages if you really want to use something like that, but the problem can be avoided entirely with a basic rs232/rs485 radio link unless very aggressive power management gets in the way.