Andrew Kohlsmith wrote: > > > I agree that we had three threads crossed in that discussion. Would > people wanting to > > do hardware projects please ID the one they (or more) they are going to > proceed on? > > Alright -- I'm Andrew Kohlsmith. I do research and development at Benshaw > Canada (www.benshaw.com) and I am the designer of the RediStart Digital soft > starter. I'd done up an old 8255 driver card YEARS ago (ISA interface) > because I got sick and tired of not having enough I/O on my computer. > > Now the 8255 driver that was desired by the list (as I understand it): > - optically isolated inputs (24V AC/DC) and optionally 240VAC > - high voltage drivers for outputs (ULN2003A-type, Open Collector), > optionally optically/relay isolated? I think 24V outs would be good for now. Photo darlington for isolated, 8311 for non-isolated (cheap) The optoisolator drawing I sent you has a darlington variant. > What I haven't worried about until now is the PC interface: how would you > like it? ISA, PCMCIA, PC-104? I haven't done any PCI design but there are > hordes of PCI glue chips I could do. > > If we're doing ISA or PC-104 what kind of port configuration do you want? > I've done some PnP but really it's not that difficult, I just need to know > what you guys want as a whole. I like ISA to keep costs down. The address decoding etc. is readily understandable and it's easy to troubleshoot. The duopoly is trying to eliminate it, but I think it's fine for control. Automation stuff can only dream of running at even 8 Mhz.so PCI is not needed IMHO. > How many I/O? Each 8255 can get you 24 I/O in your choice of three (basic) > flavours: straight I/O, interrupts and control lines. The 8255 has three > 8-bit ports but IIRC (gotta get the datasheet out) there are some > restrictions as to which can be input and which can be output in some > configurations. The board I designed long ago was used for straight I/O and > supported 3 8255s (just because I got sick and tired of soldering all the > wires. There's a topic for discussion. Lowest cost is to do fixed configs. Mixing is a compromise. Since we're polled, straight IO is appropriate but how much of each? Regards cww _______________________________________________ LinuxPLC mailing list [email protected] http://linuxplc.org/mailman/listinfo/linuxplc

 

> I think 24V outs would be good for now. Photo darlington for isolated, > 8311 for non-isolated (cheap) The optoisolator drawing I sent you > has a darlington variant. *nod* I've put up a very cursory intro page at http://www.mixdown.org/~andrew/ioboard/. I think a very basic system will be best off. Especially if it can be expanded as I've tried to explain there. Need 4kV control? No problem; just make your own medium voltage input board and snap it on. The board-board connectors I'm thinking of are like 90 degree IDE connectors. Maxim made a Motorola 68HC11 evaluation board with this concept... there was a bare microcontroller and then their various evaluation boards were simply mated beside the base microcontroller board. it works REALLY well and is very cheap. So the base I/O module would interface to a 24V I/O board and there's your basic system. If you want relay outputs you either find or build the appropriate I/O board and snap it beside the base I/O module. Similarly the "data" end of the system is a 5V 8-bit ISA-like bus. Interfacing to ISA is seamless. If you want an ECP/EPP parallel port end you snap it on to the 8-bit bus and go. ModBUS over RS485? Ethernet? CAN? USB? no problem. A single PIC16C54 or F84 would do most simple interfaces with a minimum of fuss. By doing it this way (base module which is a lowest-common-denominator approach) we can achieve maximum flexibility and not have a zillion different base modules. Comments are more than welcome. Regards, Andrew _______________________________________________ LinuxPLC mailing list [email protected] http://linuxplc.org/mailman/listinfo/linuxplc

 

Hi Andrew One thing we have to keep in mind is our target audience. The terminals should be din rail mountable and use screws. Having output groups with strappable commons is industry practice as are inputs that can be strapped for either sinking or sourcing operations. We would do well to be familiar. Where I started off with this was to make terminal boards for "standard" 8255 cards that did the TTL to 24V Industrial conversion. These already exist but are pretty expensive and don't take advantage of the silicon available that can give us industrial ports at low cost. Since then we have talked about an 8255 card that has the conversion built-in. Others want a printer port board that converts to 24V or other standards I believe these already exist and are reasonably priced. I will research where I saw this and report back. Willy is working on an intelligent Ethernet IO scheme. What you are proposing is an all in one with multiple network, parallel, and serial interfaces and options on the output. Is this correct? Let's try to avoid duplication and colloborate where we can. I think we have some duplication. Help me sort this out at an early stage. cww _______________________________________________ LinuxPLC mailing list [email protected] http://linuxplc.org/mailman/listinfo/linuxplc

 

May I point out a few a flaws in the 8255 schemes. 1) The various pc buses keep changing in specs and number of free slots on the motherboard can also change. Also consider warranty issues, if the PC has already been bought. The PCI bus and the all the new buses will be wide(32 bit+)and fast(100MHz+) with hairline spacing, so pcb will be difficult to make. 2) The 8255 is practically obsolete. as alternative we could use the printer port especially since pass through is not difficult. In fact using a FPGA, a parallel port interfacer can be built so that printing can also be done. Else use the USB, slower than ethernet but 90% apps are not going to require fantastic speeds. The USB being serial with power out will be easier to optoisolate. USB controllers are available as complete chips so upgrading old serial hardware will be possible. kalpak dabir [email protected] or [email protected]

 

> One thing we have to keep in mind is our target audience. The terminals > should be din rail mountable and use screws. Having output groups with > strappable commons is industry practice as are inputs that can be strapped > for either sinking or sourcing operations. We would do well to be familiar. Indeed! I have a career in industrial controls and automation so I am pretty familliar with this camp. Always willing to be moreso but you are exactly right about having some form of DIN-rail mountable system. (an aside: I know of exactly two companies who make DIN-rail encolsures: JIT and Altech. There *has* to be more.) > Where I started off with this was to make terminal boards for "standard" > 8255 cards that did the TTL to 24V Industrial conversion. These already > exist but are pretty expensive and don't take advantage of the silicon > available that can give us industrial ports at low cost I didn't realize this. I thought it was to make an I/O board which contained x number of 8255s and the appropriate drivers. > Since then we have talked about an 8255 card that has the conversion > built-in. Yes. This is where I started paying attention. > Others want a printer port board that converts to 24V or other standards > I believe these already exist and are reasonably priced. I will research > where I saw this and report back. Okay. > Willy is working on an intelligent Ethernet IO scheme. > What you are proposing is an all in one with multiple network, parallel, and > serial interfaces and options on the output. Is this correct? Yes...ish. This is where I really need to make some quick drawings and scan them in. What I was thinking of was a base card which used a 5V TTL ISA-compatible bus (i.e. hooking it up to an ISA bus would require a decoder and hooking up the control, address and data lines) and gave you nonisolated, 5V I/O through a 50-pin (25x2) 90-degree connector. This connector is NOT for external use. It is meant to butt-up against a driver card which would either be isolated, relays, coffee-makers... whatever really so long as it fit inside that enclosure. The base unit would come with a 24V driver card *inside the DIN-rail enclosure* and have 24V (AC and DC) optoisolated inputs. Now... let's say you need 250VAC inputs. There would be a driver card which provided the higher spacing and isolation required and you could open up the enclosure, unplug the old (24V) driver section, snap in the 250VAC section in its place and put it back together... Obviously spacing and whatnot would have to be assumed good for 250VAC. If you needed 4160V isolation you'd use an external driver card and use the 24V or 250VAC one as a pilot... Now as far as the control (or data) side of it: the base card would have that 5V ISA-like bus. The DIN-rail unit would be manufactured with an additional card on that bus: whether that be a Centronix interface, RS232 or RS485 interface with ModBUS... whatever. Willy's card could connect to that either inside the enclosure (if it fit) or beside with a short run of cable. If that is unacceptable (I don't see much ribbon cable in industry... at least not running between DIN-rail modules) then Wily's module would spit out RS232 or RS485 (whatever) and hook up to the I/O card through that. I'm going to try and get those drawings done today and on the web site. It sounds like I'm being redundant and making a mountain out of a mole hill but (in my mind's eye anyway) I am reducing costs and making the module very flexible. By having a base card capable of communicating to the control end in so many formats through snap-on "data" cards and then be able to be "upgradable" through removable "driver" cards I think we could really get the quantities of the base card up and therefore make it really economical. Instead of 500 RS232 I/O boards and 500 RS485 I/O boards you now have 1000 base cards with 500 of each module. Same deal for the I/O end... the basic unit is 24V but if you need beefier outputs and more rugged inputs, there's nothing stopping you and it doesn't reduce the quantities of the base board. In a similar note: Altech makes a really nice "high density" enclosure that we use for our (Benshaw's) RTD module. I believe the terminals are all 250VAC 2A rated. Regards, Andrew _______________________________________________ LinuxPLC mailing list [email protected] http://linuxplc.org/mailman/listinfo/linuxplc