Need Warning before Compressor Starts to Prevent Cardiac Arrest

Thread Starter

KeefyW

Joined Feb 1, 2020
18
When my compressor starts and I'm working in my garage it make me jump out of my skin every time. I need something to warn me of its imminent start.
So could someone out there give me some clues as to how I might do the following:
Build something which beeps for 3 seconds before switching on a 1500W compressor motor. It is to be activated by the pressure stat on the unit closing and of course must turn off the motor when it opens. So, to summarise events:
- Stat. closes
- Beeper sounds 3 sec.
- Beeper stops. 240v supplied to pump
No heart attack
- Stat. opens when at pressure
- Pump disconnected

I am quite competent and could translate a circuit into a working unit without problems but I wouldn't know where to start designing it.

Many thanks.

Keith
 

dl324

Joined Mar 30, 2015
11,264
Welcome to AAC!

To give a 3 second warning before the compressor will turn on will be difficult because it depends on the rate at which air is being used.

Sounding a warning when the tank pressure drops to a certain level is more straightforward; assuming you can insert an appropriate transducer (which I haven't researched) into the air flow.
 

jpanhalt

Joined Jan 18, 2008
10,087
What about turning the power switch off until you are ready to start it. You can almost guarantee it will start if left off all night.
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
Welcome to AAC!

To give a 3 second warning before the compressor will turn on will be difficult because it depends on the rate at which air is being used.

Sounding a warning when the tank pressure drops to a certain level is more straightforward; assuming you can insert an appropriate transducer (which I haven't researched) into the air flow.
Hi Dennis. And thanks for the welcome. I was hoping to use the closing p/stat to signal the beeper then close a SSR or someting, so after the pressure has dropped to cut-in pressure. As you say, other lines of thought would lead to a variable delay depending on air usage.
 

dl324

Joined Mar 30, 2015
11,264
I was hoping to use the closing p/stat to signal the beeper then close a SSR or someting, so after the pressure has dropped to cut-in pressure.
That would cause the warning to sound only when the compressor has turned on.
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
What about turning the power switch off until you are ready to start it. You can almost guarantee it will start if left off all night.
The compressor lives in the garage. My man shed. The user of said compressor is my wife - with her air tools for furniture restoration. She can't stand the noise either so that's why it's in the garage. Actually, when not being used it doesn't leak at all. 125psi at bed time. 125psi the following breakfast time having been switched off all night.

Beginning to think ear defenders, louder stereo, divorce.....
 

dl324

Joined Mar 30, 2015
11,264
Actually, when not being used it doesn't leak at all. 125psi at bed time. 125psi the following breakfast time having been switched off all night.
I think I read somewhere that the tank shouldn't be left pressurized for long periods. Don't know why.

My tank leaks, but I still depressurize when I'm finished using it.
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
That would cause the warning to sound only when the compressor has turned on.
So the idea is the switch closes, activates the beeper/control circuit which then 3 seconds later (or so, not crucial) sends the swiching voltage to the SSR. The optical SSR would isolate the pump from the pressure stat switch completely, being controlled by the beeper/control unit which some one might help by designing for me ;)
 

ronsimpson

Joined Oct 7, 2019
824
Time delay relay.
There are two types. Delay to start or delay to off. You want to delay on start and no delay for off.
You want a relay with 220VAC input but if you can only find a relay with 12V input then get a 12V wall-wort and have the compressor contacts power the 12V supply---the supply power the relay---which powers the motor.
The contacts in the relay need to be rated 220VAC 10A (I don't know what rating).
1580572810962.png
This relay is adjustable. Some are fixed.

Do you have a 220VAC noise maker? My idea is to bolt a shot gun to the wall with a string to the delay relay. The sound of the gun going off will prepare you for the sound of the compressor starting. lol
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
I think I read somewhere that the tank shouldn't be left pressurized for long periods. Don't know why.

My tank leaks, but I still depressurize when I'm finished using it.
I do that too but mainly to get the water out, especially in this weather - 95% humidity, 95% of the time. But it does get used every day.
 

dl324

Joined Mar 30, 2015
11,264
So the idea is the switch closes, activates the beeper/control circuit which then 3 seconds later (or so, not crucial) sends the swiching voltage to the SSR.
That's doable if you're willing to do a bigger hack on the air compressor. Just do as you say. Disconnect the device that turns the compressor on and have it trigger your 3 second warning and have the warning circuit start the compressor.

But, now you need to handle the cut-off indication to turn the compressor off.

Seems like too much bother to me...
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
Time delay relay.
There are two types. Delay to start or delay to off. You want to delay on start and no delay for off.
You want a relay with 220VAC input but if you can only find a relay with 12V input then get a 12V wall-wort and have the compressor contacts power the 12V supply---the supply power the relay---which powers the motor.
The contacts in the relay need to be rated 220VAC 10A (I don't know what rating).
View attachment 198070
This relay is adjustable. Some are fixed.

Do you have a 220VAC noise maker? My idea is to bolt a shot gun to the wall with a string to the delay relay. The sound of the gun going off will prepare you for the sound of the compressor starting. lol
I think you've just cracked it. 12v option could supply the beeper too. Plus you cracked me up with the shotgun plan !!! I used to work in a place where the compressor was known as Zoe. (Zoe Wanamaker the noise maker - sad I know.) Many thanks Ron.
 

bignobody

Joined Jan 21, 2020
68
Just to offer a different perspective on the problem - if the sudden sound is startling you, would another sudden audible sound (the warning beep) not also be startling as well? Maybe a bright flashing LED instead, something just enough to catch your attention.
 

gramps

Joined Dec 8, 2014
83
Arduino detects pressure switch closure > sound buzzer > wait 3 seconds > energize HD relay (contactor) that powers compressor
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
Just to offer a different perspective on the problem - if the sudden sound is startling you, would another sudden audible sound (the warning beep) not also be startling as well? Maybe a bright flashing LED instead, something just enough to catch your attention.
A warning beep at 30dB or 2hp motor at 95dB ? Daddy or chips ? Flashing LED would have to be bright enough to catch my attention when my back is turned but defo worth considering. I have LEDs a-plenty but would need to buy a beeping device !
 

Thread Starter

KeefyW

Joined Feb 1, 2020
18
Arduino detects pressure switch closure > sound buzzer > wait 3 seconds > energize HD relay (contactor) that powers compressor
Since my renewed interest in electronics (recent and purely out of necessity) I keep coming across the name Arduino.

I bought my nephew something similar - an RPi - last Christmas but he never let me play with it. Do I need to learn Linux to play with this Arduino ?
 

dl324

Joined Mar 30, 2015
11,264
Do I need to learn Linux to play with this Arduino ?
No. It doesn't have an operating system and the IDE runs on Windows. Be warned, it's buggy and the Arduino (and RPi) forums aren't very friendly. I gave both a try, both to learn and contribute, but found the environment to be hostile (mostly from very high post count members who are too full of themselves).
 
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