Flutterby™! : Parallel port relays 2003-02-03 19:53:04+00

Parallel port relays

2003-02-03 19:53:04+00 by Dan Lyke 9 comments

While I'm rambling about embedded hardware occasionally, if you got one of those Via Eden Mini-ITX boards that I mentioned here earlier and looking for more I/O than the one serial port can manage (if you're using, for instance, the AR-16 that I'm using based on Meuon's suggestion), Phil found the Industrologic RIO-8 8 relay output board with instructions for wiring it to a parallel port. Yes, I know there's nothing you couldn't do with a handful of 2N2222s and a few diodes and resistors, but sometimes letting someone else do most of the soldering is a good thing.

The parallel interface is probably a lot faster.. but most control applications are plus/minus a second.

But then, I've actually hooked devices to the motherboard mounted relay on original IBM PC's (4.77mhz) that were intended for controlling a cassette tape recorder... when they were new $5k+ systems with mono monitors. Even used one to control a spirometer (lung capacity measuring device).

You folks need to quit piddling around with the rinky dinky stuff and really look into Automation Direct's hardware. Grab a T1K-01AC 120vac power supply for $82, a T1H-EBC Ethernet Slave I/F Module for $199, one T1K-08NA-1 8PT 110VAC Input module for $68 and a T1K-08TA 8PT 110-240VAC Output module for $97 and then go grab the SDK for the EBC from Host Engineering. Yeah, I know, you think the $446 for the hardware is outside of your budget but this is a very low price for this type of equipment when compared to Siemens, A-B or GE equivilents.

The problem I see with that, Larry, is that that's $446 before the stepper controller. Searches for "stepper" and "servo" on Automation Direct yield nothing, so I can assume that rather than the $100 we're currently paying we'll be in the $600+ range for servo control for this sort of hardware that I saw elsewhere. But even barring that, if we go with a stock PC case, we're talking $100 for the Via Eden

, a few bucks for RAM, $30 or so for case+PS, $60 for the relay board, a few more bucks for a solid-state boot, and we're still over $100 cheaper than Automation Direct

before the servo control.

(Although, to be fair we could shave a few bucks off of the controller prices with the relay boards, because we're switching 1.5v signals with 'em.)

Multiply those hundreds of dollars of price difference by one or two hundred units and add to that the costs of developing in an environment I'm unfamiliar with, and it just doesn't seem practical. And it might turn out that I can use the CPU to do other things, like image processing and more complex camera control, when it's not watching the servo functions. In fact I need to check if the cameras we're looking at have any Linux support, given the way this thing is shaping up, adding a FireWire card and running the whole thing with an HTTP interface seems very promising.

Dan, what I gave you was just I/O and an ethernet card to communicate with it. The SDK I pointed to is for some libraries for reading from and writing to that I/O over ethernet. Yes, it is most likely overkill for what you are doing and the environment you will be doing it in. Also as cheap as Automation Direct is, there products are industrial duty products and are going to run a good bit more than what you need for your project just because of the added ruggedness required. Still, I'd love to get you interested in the industrial duty controls for purely selfish reasons. :-)

Yep. I realize that there are some things about reliability and just software simplicity that we're bypassing by going with the PC architecture stuff, but it's something I'm familiar with. I look at the Automation Direct

website and I get lost in what's compatible with what and how things will talk together and all of that, and then I go to the hardware hackery websites and see words like "TTL" and "serial port" and realize that I can make it do what I want. h

Dan, you are such a hacker (old-school def). And the point you made about those 'industry grade' sites and products is a good one. they WANT you to interface with a salesperson to select the 'best' combination of parts/systems for your application. They abhor the do-it-yourself mentality.

Meuon, I'm going to disagree with that statement. I've run into nothing but support for my imagination and creativity in solving a specific problem from these vendors and given a design criteria for a project I have much better luck finding exactly what I need on an 'industry grade' site than I do on the hacker sites. The difference is that I've spent the last twenty years specifying this type of equipment for people who are looking for solutions for a one off custom job where it is cheaper to buy component parts that are known to work together than it is to develop your own component parts. The project Dan is working on will allow development costs to be spead out over more than a hundred units so the project can support a relativly high development costs but not high component costs.

In fairness, the guy from Access Consolidated Technologies on a day's notice came all the way up here from San Jose on a day's notice, offered us a 60 day tryout of a gear reducer, but said "you're really better off buying a couple of gear pulleys and just having the machine shop make the reducer for you". Zero hard sell there, and if we weren't so far into the process (and had so much bad luck with other vendors) I'd just push to let them take the whole job.