Deciding on what control voltage to use. Is there a hierarchy?

Got a SMC pressure switch that can take 12-24VDC.

Got two small relays (DIP size) that have to control 2 larger relays. These are in 12 or 24VDC.

Got two larger relays to switch 120VAC to two ASCO drain valves. These are in 12 or 24VDC.

The issue with the drain valves as stated from one of their people: Only the 120VAC ASCO valve can withstand up to 150PSI.
This requires me to use 120VAC valves. Requires me to work backwards.

Background:
A control box I'm building will make it possible to open water drain ports at the best time. Rather than using a simple timer.
There is a 50' copper wound coil on the left side and at the bottom is a water collection filter that I made. Now no more water
coming out from the main tank. In the past it was like a water faucet. The pressure at the drain is only there while a charge is taking place,
and about 30 seconds for the air to bleed out of the 50 foot 5/8 copper tube coil (un-loader operation). So a smart timer is needed.



The control will mount in a box on that flat plate by the motor.

I replaced the mechanical pressure with a digital SMC pressure switch. I have it connected to a port on the top of the tank, with a 90 degree bend on the connecting tube. Can read the display easier.
Sometimes the motor would be switched on/off rapidly at the end of a cycle with the old switch.



Decision:
Is 24VDC the most common control voltage?
Or is 12VDC?
It doesn't probably have to be regulated that well. But as a habit I like to regulate and protect.

24vdc is probably the most common low voltage I've come across,

UK tends to have 110vac where there is a transformer or else 240vac as a convenient control voltage on older equipment, and 24vdc on newr gear

In the US, anything up to about 50 volts is considered "low voltage" in the National Electrical Code, with less strict requirements than above that. The ~50 volts was originally to accommodate the 48-Vdc used by landline telephone systems.

That is a lot of stuff to hang on the side of a reciprocating compressor. They're notorious for shaking even the best secured piping off eventually.

Stuart

Joe Gwinn said:

In the US, anything up to about 50 volts is considered "low voltage" in the National Electrical Code, with less strict requirements than above that. The ~50 volts was originally to accommodate the 48-Vdc used by landline telephone systems.

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It isn't FUNNY but.. (telegraphy even earlier and at higher Voltages.), we did have our share of fatalities.

Neg 48 is on float at closer to 60 VDC at a central office. Loop extenders and long-loop adapters put 60 to 70-plus V on the tip and ring right at your household RJ. Long open wire lines have serious inductance, punch well-above 300 V when the ringer dynamos smack them. Even Comcast coax runs 90 V -plus to power distributed goods.

Injuries, even fatalities?

Sad to say, it was seldom the electricity, "directly"

Broken leg, back, or neck when it knocked yer ass off a ladder at a tall CO distribution frame or from tellypole-altitude out in the boonies, rather!



Just use 24 V, Ron.

Even telcos have moved more and more to FM site-wide 24 V provisioning vs neg 48 as we've gone to digital and data.

It is about as common nowadays as such things ever get. So you have more choices at good price-points.

Other than automotive use.

Tapping into auto industry 12V goods (10 to 18V, actually)...has merit as cheap and cheerful off the massive volume of their market, but sometimes TOO DAMNED cheap, fewer choices.. and also wants larger conductors.

24VDC and 115VAC are what I typically see. Occasionally 24VAC or 12VDC but those aren't as common.

atomarc said:

That is a lot of stuff to hang on the side of a reciprocating compressor. They're notorious for shaking even the best secured piping off eventually.

Stuart

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This one is quiet. Sitting on wheels with screw down rubber feet. Each foot is 3in diameter by 2.5" tall rubber cylinder. Rig is on wheels and with only one foot on the ground to keep it from
rolling there is almost no vibration. Did it like this because I don't want to have a bunch of piping on the walls.

Strostkovy said:

24VDC and 115VAC are what I typically see. Occasionally 24VAC or 12VDC but those aren't as common.

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My original direction was to 24VDC. That's probably what I will do and forget about those 129VAC/12VDC SIP switching regulators. Those have a max output of .25A.

The 120VAC/24VDC SIP has a max output of .125A. Cutting it close.

rons said:

My original direction was to 24VDC. That's probably what I will do and forget about those 129VAC/12VDC SIP switching regulators. Those have a max output of .25A.
The 120VAC/24VDC SIP has a max output of .125A.

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Didn't look as if your project was so space nor booted-into-orbit mass constrained as all that.

Quit trying to compete with NASA, go for redneck-DIY overkill-durable and give it some room.

Prolly end up CHEAPER, too.

Not to mention "done last week, already" if you hadn't been over-engineering a problem out of a solution .. just because you CAN!

thermite said:

It isn't FUNNY but.. (telegraphy even earlier and at higher Voltages.), we did have our share of fatalities.

Neg 48 is on float at closer to 60 VDC at a central office. Loop extenders and long-loop adapters put 60 to 70-plus V on the tip and ring right at your household RJ. Long open wire lines have serious inductance, punch well-above 300 V when the ringer dynamos smack them. Even Comcast coax runs 90 V -plus to power distributed goods.

Injuries, even fatalities?

Sad to say, it was seldom the electricity, "directly"

Broken leg, back, or neck when it knocked yer ass off a ladder at a tall CO distribution frame or from tellypole-altitude out in the boonies, rather!

Click to expand...

Yeah. The Telco worried more about customers than linemen.

My grandpa had many stories from the 1920s, where 600 Vdc was quite common in industry. Hearing those stories convinces one that the NEC is written in blood.

By the way, Power over Ethernet uses 48 Vdc (regulated).

Joe Gwinn said:

Yeah. The Telco worried more about customers than linemen.

My grandpa had many stories from the 1920s, where 600 Vdc was quite common in industry. Hearing those stories convinces one that the NEC is written in blood.

By the way, Power over Ethernet uses 48 Vdc (regulated).

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It may do.

John Fluke said Comcast had 90 VDC on their coax. More to that than just Ethernet, though.

C&W? Time was, we worked submarine cables on time-of-day-schedule-reversed simplex-phantom @ over 8,000 VDC. Australia to Hawaii was the longest "unrepeatered" span of the age.

The remnants, long after out of telegraph service, served a Univeristy as sensor to measure magnetic field changes of the Planet.

Control logic in switches, sensors and buttons are somewhat different than solenoids or this ilk that provide real world power to move something.
DC of course switches faster than AC. Why not 5 volts the now mainstay? Good enough for old TTL so why not in machine tools? Or 3.3 VDC?
But will 5 or 12 volts at 500-1000 amps poke you as 440 at 5 on the fuse? Think DC welder.
I like 24VDC for noise, shielding, isolated ground and current limited but I am that dinosaur.
Some of my stuff has been 110 AC and 200+ hard relays. In a coolant rich environment ground leaks would would cause complaints from the floor.
Not big just just the tiny bite when loading a part now and then. At first I was what?? Then go out and do it for a bit myself and ..... Yes, one tickle every few hours is very bad.

My air system runs on 440AC and the hard wired logic the same. Drains on 120 and self conditioned. Maybe you are way overthinking this system and adding logic or controls not needed.
When is seems confusing KISS is my go too base.
Bob

CarbideBob said:

Control logic in switches, sensors and buttons are somewhat different than solenoids or this ilk that provide real world power to move something.
DC of course switches faster than AC. Why not 5 volts the now mainstay? Good enough for old TTL so why not in machine tools? Or 3.3 VDC?
But will 5 or 12 volts at 500-1000 amps poke you as 440 at 5 on the fuse? Think DC welder.
I like 24VDC for noise, shielding, isolated ground and current limited but I am that dinosaur.
Bob

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Oh, surely! Must be a YOUNG dinosaur? "BAD enough" for "old TTL", you mean!

Vcc's of 5 VDC and 3.3 VDC adapted for single-ended "attempted signalling" proved to be EVER so marvelous as "job security" whilst several generations of technoids tried to keep signals clean and unf**ked with!

Lest you have forgotten in the fuzzy halls of time 3.3 goes clear back to DCL and RTL daze, "DCL" option as well.. even prior to TTL.

BTDTGTS, No Fine Way, thanks!

As to the 24 V & cousins? Inherently better noise immunity in our general environment w/r power goods and the trash all around us.

Sibling Company IS/IT alleged-guru comes hat in hand, said his Director sent him, he can't get his Metcalfe's Folly 10-Base T to work between the top floors of two adjacent office towers. 'bout a 900 foot run.

Expected. Already had a circuit in-place for his use.

"How far does that Arcnet and TCNS you guys run span, anyway?"

"We run it optioned for 4.8 miles. Don't need the full 88 mile option."

For the Halibut, once demoed running Arcnet down the hall over barbed wire instead of coax!

It JF worked. Roughly 25 V P-P signal level when Metcalfe's Folly was around 2 V, was it?

Use the 24 V goods, Ron... easier on the knees?

I understand that "low voltage" controls means under 120volts.
Bill D

24 VDC seems quiet popular in 95% of the machines I have worked on in the states, gets my vote. Unless it going to lead to a recount and complete mess. Just saying.

thermite said:

"....Broken leg, back, or neck when it knocked yer ass off a ladder at a tall CO distribution frame or from tellypole-altitude out in the boonies, rather!

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This....

...was replaced by this...

...which led to this.


These newspaper pictures were all local to me, in 1959/60

thermite said:

Sibling Company IS/IT alleged-guru comes hat in hand, said his Director sent him, he can't get his Metcalfe's Folly 10-Base T to work between the top floors of two adjacent office towers. 'bout a 900 foot run.

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Hmm. The IEEE 802.3 standard for BASE10-T calls out a maximum reach of 100 meters (300 feet), so what did he expect to happen.

Expected. Already had a circuit in-place for his use.

"How far does that Arcnet and TCNS you guys run span, anyway?"

"We run it optioned for 4.8 miles. Don't need the full 88 mile option."

For the Halibut, once demoed running Arcnet down the hall over barbed wire instead of coax!

It JF worked. Roughly 25 V P-P signal level when Metcalfe's Folly was around 2 V, was it?

Click to expand...

Yes, ArcNet was designed to do just that,


Circling back, for the 900-foot (300 meter reach, fiber optics are far more suitable, especialy in factories, as fiber is totally immune to EMI from such as shipyard welders and humongous motors and their VFDs.

Classic Ethernet - Wikipedia

Joe Gwinn said:

Hmm. The IEEE 802.3 standard for BASE10-T calls out a maximum reach of 100 meters (300 feet), so what did he expect to happen.

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He was a Win-Weenie. Thought he had outsmarted that by putting a Synoptics FO rig in the middle - but that only connected amongst his alleged "servers" and CICS/VTAM links to Big Iron.

C&W's "core" and one of the 3080, later 3090 mainframes , the Vax, and half the Perkin-Elmers were in the carpark levels UNDER the office towers.

He still had over 450 feet, each leg and was actually able to move data. Just couldn't get it to a level of usability to serve for the Executive suite, CEO, COO, & their support staff on the top floor, to same-again our unit (the "holding Company") head & staff, top of the OTHER tower.

We were Vax, Netware, OS/2, fully TCNS already. The Arcnet gear I gave him were our pull-outs!

"Big Iron" CIO - who had sent him - were LU6.2, Token Ring.

Stuff was still changing now and then before contagious stoopidity pretty well standardized Metcalfe's Folly.

The 100-VG-AnyLAN I did for a Hong Kong client a few years later was right rare.
But his office suite shared the top floor, half a flight up, of a 26-story tower with four shafts worth of very active lift motors & their switchgear, was faced on three sides with other rooftops loaded with GSM and AMPS antenna farms, more than one provider, each, so...

Got comical years later when his new in-house "guru" tried to replace the 100-VG with 100-base-"MF" ....and had the usable data rate go into the toilet! "100" doesn't always mean "100".

Yes, ArcNet was designed to do just that,

Circling back, for the 900-foot (300 meter reach, fiber optics are far more suitable, especialy in factories, as fiber is totally immune to EMI from such as shipyard welders and humongous motors and their VFDs.

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I could have given him TCNS on glass. We used it amongst our clustered server, coax to the destops.

But WTF? He was only running Windows, pre "NT"! Why encourage faster waste of greater amounts of time? The more it was wonky, the more actual work and less mental-masturbation got done.

Summer air-mass thunderstorms, common in NOVA? The WinSerfs frantically sendiing "runners" up and down the hallways "Save your work and power-down! Storm coming!"

We just grinned and carried-on! TCNS didn't give any more of a damn about thunderstorms than Elliot Roosevelt gave a damn one way or the other about war!

Another HKG client had "pioneered" that "minimalism" locally. Hong Kong International School. Their CIO ran fiber to every desktop.

The benefit to the students was the cost meant they could only afford 25% as many computers, had to prioritize use, plan ahead, schedule, check with others, and team-up to work TOGETHER so as to share effectively. Macs, as well, not WinWOES.

So the kids got to actually learn and grow to be genuine and functional human beings who could fire up ad-hoc cooperation most anywhere in life.. instead of glued-to-the-tube eye-candy-addicted "loner" WinSerfs going progressively more isolated!

Dumb like a fox.

One of the best LAN investment paybacks I've ever seen, actually! It produced healthy leaders rather than dull "bomb, burn, and shoot up the school" bentnerds!

Bill D said:

I understand that "low voltage" controls means under 120volts.
Bill D

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When I was in school there was a guy I got to know who was in the navy. He told me that the manuals for repairing equipment where like this:

1. Check the wires for zero potential.
2. Conduct repairs on equipment.
3. Check that the wires still have zero potential.

His expression was one of

Bill D said:

I understand that "low voltage" controls means under 120volts.

https://www.practicalmachinist.com/...tage-use-there-hierarchy-dont-touch-wires.jpg

Bill D

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Chinese have a saying that anything that does not kill you makes you stronger.

California seems to figure that anything that DOES kill you increases the State's revenue?

Can't very well protest the fine, when some other party is even deciding how to cast both of your votes, can you?