Wireless instrumentation and infrastructure on a very small budget?
One inventor uses obsolete cell phones as low cost wireless instrumentation transmitters. Cheap, yes, but is it for you?
In these days when extra cash is scarce, one inventor says he has found a way to use electronic “trash” as industrial hardware. Imagine using the cell phones that your teenage kids think are un-cool to send back data from remote instrumentation. It may sound far-fetched, but there’s even more.
Carl Landwiener has worked as an instrumentation engineer and is an industrial pack rat of indescribable proportions. Once he realized how many cell phones are replaced daily, he started collecting the older units and found how easily they could be re-purposed for more interesting applications. His new system is called CPIS (cell phone instrumentation system) and he believes it to be a technology ideally suited to tough economic times. With an inexpensive proprietary replacement chip and a simple base station, both created by Landwiener and available now, you can be receiving data via this wireless system from up to 24 remote 4-20 mA devices within hours. With chips at $49 each and a base station card (to go into an existing computer of your choice) at only $249, all the hardware to outfit 24 remote devices will cost less than $1,500. (Multiple networks operating in parallel are possible, but none can have more than 24 nodes.) This does not include the individual phones, but anyone who has a family should be able to find a few retired units around the house. Traded-in units can also be purchased for a few dollars from cooperative cell phone dealers. Most get broken-up and recycled, so this is a better use.
CPIS is already being field tested (see photo) and has performed remarkably well given the nature of the equipment. “The photo shows one of the first working installations, mounted on a differential pressure gage,” says Landwiener. “The company doesn’t want me to use its name, but they’ve been amazed at how reliable it’s been. The receiver gathers the data and sends it via Ethernet to your control system, just like any other wireless gateway.”
CPIS performance isn’t quite up to the standards of current SP-100 or WirelessHART devices. There is no redundancy since individual devices don’t talk to each other or to multiple gateways. Battery life also leaves something to be desired given the high power consumption of a cell phone compared to current wireless instrumentation. “That has been a problem, but we’re working on it,” Landwiener adds. “At the moment, if you have the original battery, the unit only operates for five or six days. That can be extended with external batteries, but I’m working on ways to improve the power consumption. However, as a practical solution, in situations where operators make rounds anyway, they can carry a few charged phones and switch units in the field by unplugging one and putting in another. The individual phones are programmed for the network, not the specific instrument, so all the phones in a given 24 node network are interchangeable. If you have a few extras already programmed, they can be recharging in the control room. It’s really very simple.”
The CPIS network is not connected to the public cell phone infrastructure at all, so there are no phone bills involved. While the functionality of the current system is very basic, there is room to expand. Currently Landwiener is testing an expansion of the system to use the phone’s text messaging capability to send HART data along with the main process variable. He’s even exploring the possibility of using built-in camera phones as a surveillance device. “I don’t think it will be practical to get real video, but we might be able to update the image six or eight times a minute,” says Landwiener. “Of course when I started out, I didn’t think we’d be able to get this much out of a regular phone, so I shouldn’t underestimate the possibilities. You won’t find a cheaper wireless video camera.”
This is just the beginning for the growing basement business. Looking down the road this curious inventor is looking for ways to use newly obsolete analog TVs as control room terminals and HMI displays. “I just can’t stand seeing all that good equipment going to waste,” Landwiener laments.
Download more information and a performance report of the first installed CPIS network.
—Edited by Peter Welander, process industries editor, PWelander@cfemedia.com ,
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