PDA

View Full Version : Splitting 595 boards



dirknerkle
06-11-2009, 02:49 PM
Has anybody tried splitting a 595 into smaller pieces, such as four 16-channel controllers or even eight, 8-channel units and building them and their related SSRs directly into displays? This way, you could essentially eliminate rewiring every year, it'd be inexpensive enough to make the displays into almost standalone, plug-in items. All you'd have to do is move the Vixen channel assignments so the right signals are sent to the right displays depending on where in the daisychain order the display is.

I know the divide-and-conquer concept is part of the idea behind the Renards which also have SSRs built in and daisychain via serial 485, but I was curious if anybody's ever tried this tactic.

My eyes are open and ears perked for a reply (my wife says that's what makes me look the way I do and that I should get that fixed...oh well...)

-dirknerkle

TERBObob
06-11-2009, 03:27 PM
Hummmmm .. kinda sounds like you got the SPOCK sydrome going on - LOL
oh wait ... thats ears pointed , not perked , and closed eyes , not opened ones . LOL
Any who ---- your idea sound like a good one to me . Sounds like it might make a little less hassle when doing the hokk-ups outside ( in the COLD blowing snow - BRRRRRRR )

pete
06-11-2009, 04:22 PM
you could do that but it depends on the distance, you could end up with performance issues the farther from the pc you get. You could do this with the renards (like the ren 8) due to the rs485 communications that it uses. but the 595 gets it's signal from the printer port which means you really dont want to be to far from the pc. Some people including myself have pushed the distance out to 100-150' but you chance signal lost.

pete

P. Short
06-11-2009, 04:33 PM
The concept is fine, but I think that you will find that it is not easy to implement a simple, reliable controller using the 595 boards.

There are several issues that come to mind right away...

First, the distribution of 5V to the controllers. Each controller will require about 70mA of current (worst case, when all 8 channels are on). This will add up quickly as you add more controllers to a given cable over 10's or 100's of feet, to the point where the voltage drop in the wire becomes significant. So you need to send a higher voltage and regulate it down on each controller.

Second, you can't reliably use TTL/CMOS signals between the controllers for the clock and maybe the latch signals (the data signals are less critical because they are re-generated on each controller, especially if you use 4094 or the Grinch chips instead of a 595). The reason for this is that standard TTL or CMOS signals are not designed for driving highly capacitive loads (e.g. long cables). After a hundred feet and passing through a number of controllers the clock signal will begin to look pretty bad, and you will have all sorts of flaky behavior.

Third, newer computers are not as likely to have parallel ports on them, and I don't know of any commonly available USB-parallel adaptors that will work with Vixen and the 595 boards.

That all said, the concept is fine. For my own display I'm implementing something that follows this philosophy. It is a small (2" x 1.5") 4-channel controller with built-in SSRs. It is intended to be used out in the yard, as close to the lights that it controls as possible. However, I don't intend to release the design for general consumption because it has a lot of circuitry (including the PIC) directly connected to the AC line, and I think that it is too dangerous for people unfamiliar with working with that type of thing.

dirknerkle
06-11-2009, 05:23 PM
The concept is fine, but I think that you will find that it is not easy to implement a simple, reliable controller using the 595 boards.

Thanks, Phil. You hit on some of the concerns I had as well.

I looked at the idea as more of an experiment than anything else... such as "can I get two to work? How about three? Four? How far would it go before it craps out?"

Voltage is certainly an issue, and I thought that because each display would obviously have its own A/C connection, I'd supplement the board with a clean but small 5v wall wart type power supply. Of course, that doesn't address the clock issue too well at all...

I pondered over the 595 and Grinch, and actually, it looked easier to me to split the Grinch -- only one chip vs four for 16 channels. May have to go that way -- it'd be a cheap experiment anyway!

The parallel port concern is most certainly germane. The only saving point is that the PCI bus will be around for a while and so parallel port expansion cards will probably still be produced for several years, too.

I like your mini-4 channel controller and I certainly agree about the safety issue. Just imagining for a moment what a person would have to do to make such a device "safe" according to U/L standards, and my guess is that you'd have to encase the whole thing in epoxy!

Thanks again for the learned guidance. I currently have plenty of things to do, but I always like to have one "on the back burner..." :wink:

-d

P. Short
06-11-2009, 05:30 PM
Apart from the fact that I just ordered a bunch of boards without any soldermask or silkscreen, this seems tempting:

http://makezine.com/18/lightbrick/

dirknerkle
06-11-2009, 11:09 PM
Apart from the fact that I just ordered a bunch of boards without any soldermask or silkscreen, this seems tempting:

http://makezine.com/18/lightbrick/

Investment casting with resin -- cool. I was a golf pro in a former life (for about 25 years) and that was one of the things we did with woods sometimes when the face insert broke. That was back when woods really were made out of wood and not metal, and periodically the face insert would crack or come loose. We'd chop it out, build a dam around the face with modeling clay, mix up resin in the customer's color choice, pour and cure it. None of them were anywhere near as thick as the brick example, and because of that, sometimes if you had an air bubble, you could hold a match just above the resin (just after pouring) and help draw it out. We had lots of tricks for fixing golf clubs... messy, messy tricks, but fun.

That would certainly seal the components, wouldn't it?!?!? Of course, the next problem is heat -- if the compoents got to hot inside, resin like that can crack from the inside out. It's not very good with expansion -- that's why we used it for golf clubs -- it was hard as a rock.

dirknerkle
07-01-2009, 01:07 AM
I gave it a try -- I built a couple Grinch-16 boards for the experiment. The net outcome is that the concept is barely workable. But it was fun to try, and I have a couple Grinch-16 boards that I can add to my arsenal, probably in conjunction with Ren-Cs.

Full information is in the Grinch section under the thread, "Grinch-16".

-d