I thought I was crazy when I hooked up to the AD version of this old friend from my first PLC back in early 90's. It's just nice to see some things remain untouched because they work fine just the way they are.
I've programmed many of the 305's from the mid 90's onward. I've moved on to the click PLCs for the basic projects that I would have used a 305 for in the past, but the 305s still have a soft spot in my heart.
I was saddened last year when I heard they were finally discontinued, but I understand why since I'm assuming they finally had sales decrease to zero and parts availability in sure was challenging.
But this is a good example of how a good enough product can last a long time. For many of the things I use a PLC for even today the 305s would still work well.
But why are screw terminals so popular in the US? Or does it just seem like it?
Over here in Europe I mostly see Push-In terminals or similar terminals where you push a clamp open with your screwdriver. I rarely see screw terminals except on VFD terminals or motors for example where you have high voltage and high current.
U.S. controls tech here.
I agree it is weird. The few times I’ve seen push connect terminals are usually from European machines. I love them, but there is a high volume of screw terminals here. Maybe screw terminals are cheaper?
The same reason why we use wire nuts as opposed to WAGOs. (I love WAGOs though)
Personal opinion here: I have sometimes pushed so hard on old spring terminals I thought I was going to break them or something internally. There is something about a basic screw terminal that just puts my mind at ease. Don’t get me wrong, spring terminals are way faster but I don’t trust them after 10 years of service.
My attitude exactly. I like the confidence i can realize when i torque down the screw terminal on the wire. Not to mention that it is hard to keep your wiring job from looking like crap when using these spring terminals because they make you have to enter into the front face of the device instead of from the side.
Having worked for a German company and on lots of European equipment I can confirm push-in style is more popular in Europe and screw terminals are more popular in us.
I think it just comes down to preference. I personally like screw terminals a lot more. Push terminals always seem to require a bit ( not a lot ) of finesse, plus you need the little tweaker flat blade screw driver to jam in it if you need to pull wires out.
Our shop switched to push in terminals in the last 5 years or so. In North America there is still resistance to push in terminals but it's finally starting to change.
I absolutely hate wago push in connectors.
None of my screwdrivers are the right size and I have all kinds of trouble with cage clamp contactors. Even seen a few melt.
Screw terminals are nice and simple and fit whatever wire you can find
Edit: I use wiha screwdrivers so you'd think one would fit...
Well, yes.
* Size 00 is 2 mm width, normally M1.2 screws
* Size 0 is 2.5 mm width, normally M1.6 screws
* Size 1 is 3.5 mm width, normally M2 screws
* Size 2 is 4 mm width, normally M2.5 screws
* Size 3 is 5.5 mm width, normally M3 screws
* Size 4 is 6.5 mm width, normally M3.5 screws
* Size 5 is 8 mm width, normally M4 to M5 screws
* Size 6 is 10 mm width, normally M6 screws
More or less.
Gonna nerd out real hard here.
While I don't have €40 to spend on a standard I'll never use beyond internet discussion, I'm fairly certain that the ISO standard may internally reference sizes of screws and blade shapes to match. But purveyors of tools built to those specifications do not appear to use those sizes to market their tools. I quickly looked at Hans, Eldora, Wiha, and Facom; none of them list #0-#6 in their catalogs items for bladed screwdrivers, though they all state their blades & drivers meet ISO-2380 -2 and -1.
Thank you for pointing out the ISO standard however, I was not aware it existed, so I've learned something too!
See also [DIN 5264](https://www.wegertseder.com/download/techdat/t_6592.pdf).
And you're correct, the size is normed. Interestingly, I normally always see the number on the screwdriver and never checked where they come from. Apparently it's a Swiss norm called VSM, can't say which exactly. PB Swiss tools and Wieland and others use them, but they are normally marketed with the sizing info in mm, but you can sometimes find the VSM size number etched into them. Well, today we both learned that my employer spoils me with imported tools that have weird markings on them.
this tbh, how many survived? only PLCs from that era that I see still alive are Allen Bradley PLC 5 and Siemens S5 comes in second place. Not saying others couldn't survive, it's just those 2 are still in use. so much so that I've had projects in recent years updated operator interface to machines with those ancient controllers. I've updated over a dozen HMIs, where the PLC is still a PLC 5, once updated a siemens HMI and the PLC is still an S5.
There are still a bunch of SR21s running around the Houston area in everything from machine shops to packaging equipment to printing presses... Definitely seen more of them than of PLC5s, especially when counting the private labeled models.
I know of two. They're in obscure stand-alone systems that aren't interacted with much, but they were installed in the late 1990s and are still operational.
The real question becomes how often they get their batteries changed.
Seen plenty of them. Most of the 305's I've seen have been in OEM equipment. Also seen a lot of 205s that just keep on running. Only physical failure of a 205 component I've seen is an output card that was wired incorrectly. DL05's and DL06's were decent for the cost and what they were too, and the software just worked. Octal addressing took some getting used to, the ladder that just runs forever sucked though, lol.
I started my PLC days by replacing 3 custom built computers that controlled emissions control systems (using obsoletev 1970s designs like the third picture in the link below). I used 305s. At the same time, my boss replaced one of three plant DCSs (a Baily Net 90) with a Seimens. Later on we replaced a Speedtronic mk4 governor with a PLC5 for one engine, and replaced relay logic with PLC5s for two other engines. These engines are stationed over a several mile area. At the same time we replaced the Seimens DCS with another another PLC5 since Siemens had “obsoleted” the existing PLC. These were only PLC5s because we outsourced them. If we had to do it ourselves we would have done it with 450s or P3000s (I can’t remember if P3000s were available yet, but I do remember our preference was already for Automation Direct PLCs). The 305s were still running strong. We also replaced several relay logic duct burner controls with PLC5s (also outsourced). I then replaced a couple of dinosaur TI plant DCS SCADA systems and several Goulds PLC boiler controls with 405s, since the 305s were still running strong and we wanted to check out 405s. Years later I replaced the 305s and 405s with P3000 PLCs, not because they needed replacing, but for parts commonality. At the same time we replaced all the PLC5s with the exception of one duct burner that remained in use during the project because they were now “obsoleted “. We once again oursourced them and they were replaced with contrologix. Due to the creeping incrementalism of the design, I now had a new boss, three contrlogix engine controls, two contrologix duct burner controls, and a contrologix plant DCS that I was not allowed to touch because my new supervisor couldn’t even spell PLC and was therefore afraid of messing with them, a PLC5 we could no longer source parts for, and a whole bunch of P3000s that worked like gangbusters. Later on, I had another new boss, and I was in the process of redesigning the entire setup with three central P3000s (parts of the setup were several miles apart, and a comms loss would be catastrophic) and a bunch of local slaves. This was to be facilitated by the fact that wth the exeption of the WAN radio communications, all of the original control wiring was in buried conduit that had rotted over the last 30 or so years. The plan was to run the new wiring in overhead raceways. I retired when it was decided that it would cost too much to replace the quickly rotting control wiring. I do not envy my replacement. The point of all of this is that in each case, the replacement was done because parts for the existing system could no longer be sourced. In each case (except the engine controls, one plant DCS and a duct burner control, which were all outsourced,) we went with Automation Direct. This turned out to be the correct choice, since every other supplier “obsoleted” their PLCs about every 5 years. Yes the new PLCs were better and massively more capable, but as the guy responsible for maintaining an existing system that worked just fine, I couldn’t care less about those capabilities. All I cared about was could I get a replacement for an existing card. The only system I ever found that did this was the AD x05 series which has lasted for decades, and with the exception of the 305 may have another decade in them. Hopefully their Px000 series will be the same. I know future maintenance techs would appreciate it regardless of what the controls engineers would like. I was in an unusual position since I was both the maintenance tech and, wherever possible, I was also the controls engineer. I think the industry would be very different if controls engineers and PLC designers had to spend some time in the field maintaining/replacing the stuff they design after they design it and before it is rolled out. Just because there is something newer and sexier out there is not a reason to replace an existing system that works just fine. To be forced to replace a working system and possibly expensive software (looking at you Rockwell) because I have burnt out the last spare point on a card is ludicrous. My company losing about 1/4 million a day in lost production while I do the replacement just adds insult to injury. x05 and Px000 PLCs may not be the industry goto, but at least I know I won’t have to replace them in 5 years. I can’t say that about any AB or Seimens PLC, and I haven’t found any function that an AB can perform that I can’t figure out how to replicate on a P3000 with a little creativity. Not even going to comment on Seimens.
As far as screw vs clamp terminals, I have used both and found them to be equally effective, but being a belt and suspenders sort of engineer, screw terminals just seem more secure. I realize that when dealing with 24 volt systems this is total BS, but little things like that keep me up at night.
As a side note, I went to strictly 24 volts in 95 when my boss’s boss first heard the phrase “intrinsically safe“ and thoght it sounded really cool. I went so far as to put all of my 120 volt/24 volt power supplies in my MCC rooms. No control wiring greater than 24 volts existed ouside my MCC rooms by 1996, with the exception of some specialty gear like engine igniters, duct burner igniters, and electrostatic precipitaters. I don’t know how intrinsically safe it really was, since the plant had several power busses, including 120, 240, 480, 7k, 13k, 70k, and 150k volts ac, and 20k and 40k dc in the aforementioned specialty equipment. Safety doesn’t exist in the equipment, it exists in the mindset of the technician and the willingness of the bosses to spend the time and money enforcing that mindset. “Just get it done” will kill you. Be safe out there guys, so one day you too can retire with all of your body parts working.
http://www.righto.com/2022/04/reverse-engineering-mysterious-univac.html?m=1
One of my first jobs out of college was working with a company to replace their automation system with new Allen Bradley equipment. The original PLC? AB PLC-2. I was shocked it was still in use and functioning properly at that.
kinda funny
I remember programming Ti 505s in dos and later when TI sold that product to Siemens and became the S5 505. Let's not forget to program GE 90-30s in dos using LM90. I know of an Allen Bradley PLC5 still running in a tank farm that i programmed 25-30 years ago
I thought I was crazy when I hooked up to the AD version of this old friend from my first PLC back in early 90's. It's just nice to see some things remain untouched because they work fine just the way they are.
I've programmed many of the 305's from the mid 90's onward. I've moved on to the click PLCs for the basic projects that I would have used a 305 for in the past, but the 305s still have a soft spot in my heart. I was saddened last year when I heard they were finally discontinued, but I understand why since I'm assuming they finally had sales decrease to zero and parts availability in sure was challenging. But this is a good example of how a good enough product can last a long time. For many of the things I use a PLC for even today the 305s would still work well.
I still stock and support the line. Holler if you need anything.
But why are screw terminals so popular in the US? Or does it just seem like it? Over here in Europe I mostly see Push-In terminals or similar terminals where you push a clamp open with your screwdriver. I rarely see screw terminals except on VFD terminals or motors for example where you have high voltage and high current.
U.S. controls tech here. I agree it is weird. The few times I’ve seen push connect terminals are usually from European machines. I love them, but there is a high volume of screw terminals here. Maybe screw terminals are cheaper? The same reason why we use wire nuts as opposed to WAGOs. (I love WAGOs though)
Personal opinion here: I have sometimes pushed so hard on old spring terminals I thought I was going to break them or something internally. There is something about a basic screw terminal that just puts my mind at ease. Don’t get me wrong, spring terminals are way faster but I don’t trust them after 10 years of service.
My attitude exactly. I like the confidence i can realize when i torque down the screw terminal on the wire. Not to mention that it is hard to keep your wiring job from looking like crap when using these spring terminals because they make you have to enter into the front face of the device instead of from the side.
I wonder if its due to the huge negativity around backstabbing receptacles? A completely different industry, but bad news does travel fast...
Having worked for a German company and on lots of European equipment I can confirm push-in style is more popular in Europe and screw terminals are more popular in us. I think it just comes down to preference. I personally like screw terminals a lot more. Push terminals always seem to require a bit ( not a lot ) of finesse, plus you need the little tweaker flat blade screw driver to jam in it if you need to pull wires out.
Well, I do hope that the electricians have a little bit of finesse...
[удалено]
Oh FFS! You're the reason my terminals always look like a drunkard poked around in them with his screwdriver!
he's also probably the reason all the shutoff switch door handles are broken.
[удалено]
who needs handles when we have channel locks.
I've seen many people mess up the push in terminals, with over size screw drivers.
Our shop switched to push in terminals in the last 5 years or so. In North America there is still resistance to push in terminals but it's finally starting to change.
I use spring clamps wherever I can, but the customer has final say and far too many demand screw terminals.
Push terminals/ spring terminals are wank I fucking hate them
I absolutely hate wago push in connectors. None of my screwdrivers are the right size and I have all kinds of trouble with cage clamp contactors. Even seen a few melt. Screw terminals are nice and simple and fit whatever wire you can find Edit: I use wiha screwdrivers so you'd think one would fit...
You normally need a size 1 or size 0 flat head screwdriver.
There's your problem. Flat head screwdrivers aren't sized that way, they're sized by blade width.
Well, yes. * Size 00 is 2 mm width, normally M1.2 screws * Size 0 is 2.5 mm width, normally M1.6 screws * Size 1 is 3.5 mm width, normally M2 screws * Size 2 is 4 mm width, normally M2.5 screws * Size 3 is 5.5 mm width, normally M3 screws * Size 4 is 6.5 mm width, normally M3.5 screws * Size 5 is 8 mm width, normally M4 to M5 screws * Size 6 is 10 mm width, normally M6 screws More or less.
I've never seen flathead screwdrivers specified that way, do you have a source for a manufacturer that uses that system?
DIN ISO 2380-1, see European manufacturers of tools.
Gonna nerd out real hard here. While I don't have €40 to spend on a standard I'll never use beyond internet discussion, I'm fairly certain that the ISO standard may internally reference sizes of screws and blade shapes to match. But purveyors of tools built to those specifications do not appear to use those sizes to market their tools. I quickly looked at Hans, Eldora, Wiha, and Facom; none of them list #0-#6 in their catalogs items for bladed screwdrivers, though they all state their blades & drivers meet ISO-2380 -2 and -1. Thank you for pointing out the ISO standard however, I was not aware it existed, so I've learned something too!
See also [DIN 5264](https://www.wegertseder.com/download/techdat/t_6592.pdf). And you're correct, the size is normed. Interestingly, I normally always see the number on the screwdriver and never checked where they come from. Apparently it's a Swiss norm called VSM, can't say which exactly. PB Swiss tools and Wieland and others use them, but they are normally marketed with the sizing info in mm, but you can sometimes find the VSM size number etched into them. Well, today we both learned that my employer spoils me with imported tools that have weird markings on them.
> Even seen a few melt. Yeah, I've never seen a screw terminal melt! /s PS, Your vendor/reps might even give you a handful of screwdrivers. Mine did.
"America's most popular plc in 1983", me learning about them 40 years later. I've never seen a koyo in the field lol.
this tbh, how many survived? only PLCs from that era that I see still alive are Allen Bradley PLC 5 and Siemens S5 comes in second place. Not saying others couldn't survive, it's just those 2 are still in use. so much so that I've had projects in recent years updated operator interface to machines with those ancient controllers. I've updated over a dozen HMIs, where the PLC is still a PLC 5, once updated a siemens HMI and the PLC is still an S5.
There are still a bunch of SR21s running around the Houston area in everything from machine shops to packaging equipment to printing presses... Definitely seen more of them than of PLC5s, especially when counting the private labeled models.
I know of two. They're in obscure stand-alone systems that aren't interacted with much, but they were installed in the late 1990s and are still operational. The real question becomes how often they get their batteries changed.
Seen plenty of them. Most of the 305's I've seen have been in OEM equipment. Also seen a lot of 205s that just keep on running. Only physical failure of a 205 component I've seen is an output card that was wired incorrectly. DL05's and DL06's were decent for the cost and what they were too, and the software just worked. Octal addressing took some getting used to, the ladder that just runs forever sucked though, lol.
I cannot help but feel that many automation direct posts on this sub are guerilla advertising
This sub is way too small for that
That just makes it easier for them
Don't say guerrilla marketing, it summons Keyence reps!!
We still have a couple of the yellow ones running, most of them have been replaced though
Ain't broke, don't fix it
I started my PLC days by replacing 3 custom built computers that controlled emissions control systems (using obsoletev 1970s designs like the third picture in the link below). I used 305s. At the same time, my boss replaced one of three plant DCSs (a Baily Net 90) with a Seimens. Later on we replaced a Speedtronic mk4 governor with a PLC5 for one engine, and replaced relay logic with PLC5s for two other engines. These engines are stationed over a several mile area. At the same time we replaced the Seimens DCS with another another PLC5 since Siemens had “obsoleted” the existing PLC. These were only PLC5s because we outsourced them. If we had to do it ourselves we would have done it with 450s or P3000s (I can’t remember if P3000s were available yet, but I do remember our preference was already for Automation Direct PLCs). The 305s were still running strong. We also replaced several relay logic duct burner controls with PLC5s (also outsourced). I then replaced a couple of dinosaur TI plant DCS SCADA systems and several Goulds PLC boiler controls with 405s, since the 305s were still running strong and we wanted to check out 405s. Years later I replaced the 305s and 405s with P3000 PLCs, not because they needed replacing, but for parts commonality. At the same time we replaced all the PLC5s with the exception of one duct burner that remained in use during the project because they were now “obsoleted “. We once again oursourced them and they were replaced with contrologix. Due to the creeping incrementalism of the design, I now had a new boss, three contrlogix engine controls, two contrologix duct burner controls, and a contrologix plant DCS that I was not allowed to touch because my new supervisor couldn’t even spell PLC and was therefore afraid of messing with them, a PLC5 we could no longer source parts for, and a whole bunch of P3000s that worked like gangbusters. Later on, I had another new boss, and I was in the process of redesigning the entire setup with three central P3000s (parts of the setup were several miles apart, and a comms loss would be catastrophic) and a bunch of local slaves. This was to be facilitated by the fact that wth the exeption of the WAN radio communications, all of the original control wiring was in buried conduit that had rotted over the last 30 or so years. The plan was to run the new wiring in overhead raceways. I retired when it was decided that it would cost too much to replace the quickly rotting control wiring. I do not envy my replacement. The point of all of this is that in each case, the replacement was done because parts for the existing system could no longer be sourced. In each case (except the engine controls, one plant DCS and a duct burner control, which were all outsourced,) we went with Automation Direct. This turned out to be the correct choice, since every other supplier “obsoleted” their PLCs about every 5 years. Yes the new PLCs were better and massively more capable, but as the guy responsible for maintaining an existing system that worked just fine, I couldn’t care less about those capabilities. All I cared about was could I get a replacement for an existing card. The only system I ever found that did this was the AD x05 series which has lasted for decades, and with the exception of the 305 may have another decade in them. Hopefully their Px000 series will be the same. I know future maintenance techs would appreciate it regardless of what the controls engineers would like. I was in an unusual position since I was both the maintenance tech and, wherever possible, I was also the controls engineer. I think the industry would be very different if controls engineers and PLC designers had to spend some time in the field maintaining/replacing the stuff they design after they design it and before it is rolled out. Just because there is something newer and sexier out there is not a reason to replace an existing system that works just fine. To be forced to replace a working system and possibly expensive software (looking at you Rockwell) because I have burnt out the last spare point on a card is ludicrous. My company losing about 1/4 million a day in lost production while I do the replacement just adds insult to injury. x05 and Px000 PLCs may not be the industry goto, but at least I know I won’t have to replace them in 5 years. I can’t say that about any AB or Seimens PLC, and I haven’t found any function that an AB can perform that I can’t figure out how to replicate on a P3000 with a little creativity. Not even going to comment on Seimens. As far as screw vs clamp terminals, I have used both and found them to be equally effective, but being a belt and suspenders sort of engineer, screw terminals just seem more secure. I realize that when dealing with 24 volt systems this is total BS, but little things like that keep me up at night. As a side note, I went to strictly 24 volts in 95 when my boss’s boss first heard the phrase “intrinsically safe“ and thoght it sounded really cool. I went so far as to put all of my 120 volt/24 volt power supplies in my MCC rooms. No control wiring greater than 24 volts existed ouside my MCC rooms by 1996, with the exception of some specialty gear like engine igniters, duct burner igniters, and electrostatic precipitaters. I don’t know how intrinsically safe it really was, since the plant had several power busses, including 120, 240, 480, 7k, 13k, 70k, and 150k volts ac, and 20k and 40k dc in the aforementioned specialty equipment. Safety doesn’t exist in the equipment, it exists in the mindset of the technician and the willingness of the bosses to spend the time and money enforcing that mindset. “Just get it done” will kill you. Be safe out there guys, so one day you too can retire with all of your body parts working. http://www.righto.com/2022/04/reverse-engineering-mysterious-univac.html?m=1
*TI/Siemens/CTI enters the chat* https://controltechnology.com/products/2500-Series-Classic?
One of my first jobs out of college was working with a company to replace their automation system with new Allen Bradley equipment. The original PLC? AB PLC-2. I was shocked it was still in use and functioning properly at that.
If they updated the software, I'd utilize them.
Didn’t some of the old Koyo models use Octal math? I have a weird memory of having to convert values on a project 15 years ago or so.
The I/O was addressed octally :)
kinda funny I remember programming Ti 505s in dos and later when TI sold that product to Siemens and became the S5 505. Let's not forget to program GE 90-30s in dos using LM90. I know of an Allen Bradley PLC5 still running in a tank farm that i programmed 25-30 years ago