On/Off switch for 12v AirComp

Thread Starter

Euphi223

Joined May 1, 2019
14
Hi people!

I need more of your generous assistance….and understanding because I’m a total noob, literally. The only (sort of) electrical thing I can do is solder wires.
I’m a bicycle mechanic in my spare time. I’m always inflating tires and tubes. I was using a ½ HP compressor. I stopped because it was far too noisy, took too long to connect hoses and attachments, and then bleed it after use. I opted instead for a cheap 12v Air compressor (250psi).
It’s smaller, quieter, and simpler (sort of). I don’t have a car, so I had to modify a 12v battery charger so I can plug the 12v socket into it, thereby operating the compressor from 240v household outlet.
This works very well with one minor issue. There needs to be an on/off switch someplace closer to the AirComp. The only way to power it is to physically plug/unplug the 12v socket.
240v, to me, is scary! I wanted to ask people who know the simplest & safest way I can put a switch on the AirComp’s power cord, or the AirComp itself. To eliminate the unplugging back at the battery charger.
Any help would be very much appreciated.
BattCharger.jpg AirComp.jpg plugged-in.jpg
 

Thread Starter

Euphi223

Joined May 1, 2019
14
BTW. I looked through similar posts on this forum. This one seemed the most relavent - https://forum.allaboutcircuits.com/threads/dc-12v-20a-toggle-on-off-switch-for-dc-19v-3-42a-laptop-power-supply.116354/
However....this confused the heck out of me. I'm a total novice, green as green can get. Please be simple, if there are any replies.
Ideally id like to open up wire casing on AirComp cord. connect POS & NEG to corresponding points on a switch. Am i being to simple? Is this idea stupid? thats why im asking for guru help.

Thanks again
 

Tonyr1084

Joined Sep 24, 2015
3,680
Ideally id like to open up wire casing on AirComp cord. connect POS & NEG to corresponding points on a switch. Am i being to simple? Is this idea stupid? thats why im asking for guru help.
First - I'm not a guru. Second, there are no "stupid" questions. Maybe ideas, but I might be labeled a guru when it comes to dumb ideas. Still, no - this is not a stupid idea. Actually it's fairly smart and pretty straight forward.

Go to an automotive store and buy a simple switch. Don't get one with an illuminated face, you don't need that. You KNOW when the compressor is running and when it's not. Take the 12 volt cord (and yes, 240 IS scary, you don't want to mess with that if you don't need to). Take the 12 volt cord and split it. Cut only one of the two wires. Solder (or crimp connect) the switch in that line. Switch ON and the circuit is complete and the compressor runs; switch OFF and the compressor - well, nuff said. Yes, it's that simple. I'll bang out a drawing to further explain. Should only take a few minutes. I'll post it in another reply.
 

dl324

Joined Mar 30, 2015
9,155
Insert a switch inline with the cigarette plug with a current rating high enough for the pump. I'd put a diode across the switch to protect the contacts from any arching when current to the motor is interrupted.

I use a 10 gallon pressure tank for putting air in tires. Before I had an air compressor, I used to take it to a gas station to fill it.
 

crutschow

Joined Mar 14, 2008
23,543
Could you just use a power strip with a switch and plug the battery charger supply into that?
Since you didn't post where you are, I can't recommend a specific device.
 

Thread Starter

Euphi223

Joined May 1, 2019
14
Thanks for the great & super-quick reply's!
Tonyr1084 - Thanks! that sort of what im thinking. Usually my ideas dont work out. When playing with big power, i like to do what i am now, asking for help.
dl324 - Thats exactly what i did before the 1/2 HP compressor. Inflate the tyre by hand pump until it was hard enough to support my riding weight. Stop at the service station and fully inflate the tyre, generally about 60psi (mtb 26" tires).
crutschow - I don't know what a power strip is. Is it similar to a multi-outlet board with a pwr switch? The distance from the house power outlet to where i'm working is far enough to be very annoying to me. A switch next to the AirComp would be brilliant!

Cheers
 

Thread Starter

Euphi223

Joined May 1, 2019
14
Tonyr1084 - Really appreciate u taking the time to make that diagram for me.
MrChips - Thanks for simplifying things further! Great!! I found this one on ebay. Same thing?
ebay switch.jpg
 

MrChips

Joined Oct 2, 2009
19,426
Tonyr1084 - Really appreciate u taking the time to make that diagram for me.
MrChips - Thanks for simplifying things further! Great!! I found this one on ebay. Same thing?
View attachment 178834
Similar but it will work. That one looks like an inline switch for a three conductor cable. Two lines are cut and switched. The ground wire is fed through. On the 12V cable, you only need to cut one wire. Leave the other wire intact.
 

dl324

Joined Mar 30, 2015
9,155
Thats exactly what i did before the 1/2 HP compressor. Inflate the tyre by hand pump until it was hard enough to support my riding weight. Stop at the service station and fully inflate the tyre, generally about 60psi (mtb 26" tires).
With the tank, you don't need a hand pump.

I once bought tires from a place called 4 Day Tires (they only worked 4 days a week). They had a battery operated compressor that was set for a fixed pressure. They just attached to the tire stem and disconnected when it stopped pumping. I bought an attachment for my pressure tank that was supposed to let me set the pressure, but it never worked.
 

MaxHeadRoom

Joined Jul 18, 2013
19,198
With the tank, you don't need a hand pump.
You can also make one from a out of date Propane BBQ tank.
I made a small one for a tank reservoir out of a propane hand torch bottle, for an air brush compressor about the same size as the OP's.
Max.
 

Tonyr1084

Joined Sep 24, 2015
3,680
@dl324 Tanks have to be pressurized. Would need a significant compressor to charge the tank, or have the hassle of going to the gas station (one WITH an air pump) and charge up the tank. Here in the US I haven't seen anything better than the 25¢ coin operated pumps. If you go to a tire shop you can get higher pressures but I'd bet they wouldn't care for filling a tank they have no idea of its condition. There might be a possibility of a tank rupturing during pressurization. That alone - if I were the shop owner - I'd say "Sorry, take your tank to someone else."

The idea of having a ready to go electric pump is pretty nice. I happen to have a battery powered pump. They're not fast but they get the job done. SUPPOSEDLY they can pump up to 250 PSI but I've never waited past 40 PSI. My battery powered pump could pump up a car tire from flat to full. But it took a while. Bicycle tires don't take as long. Probably nearly as long as a pump connected to a 12 volt source. However, the one inconvenience with battery power is that you have to charge the battery. The more you use it the more often you have to recharge it.

@Euphi223 stated he wants to be able to switch on and off 12 volts. An in-line switch is the way to go. Whether a rotary in-line switch, which is what I have on one of my older 12V pumps or bodging together a toggle switch in-line, the solution sought by euphi is for a switch in line. Tanks are nice for that once in a while need; but a bike shop owner, or should I say a Bicycle Mechanic would go through a tank pretty quickly and have to run out to fill a tank. And if the tank sits over night, or for days unused, by the time someone wants to use it the air pressure may have leaked out. I think the switch is the way to go.
 

Tonyr1084

Joined Sep 24, 2015
3,680
Similar but it will work. That one looks like an inline switch for a three conductor cable. Two lines are cut and switched. The ground wire is fed through. On the 12V cable, you only need to cut one wire. Leave the other wire intact.
Actually, since he has (probably) only two lines, cutting and switching both lines wouldn't hurt. It's up to him. However, just thinking of this - an inline fuse would probably be a good idea too. Protect the supply against accidentally mis-wiring the switch or other potential failures such as a short circuit or if the pump motor should jam.
 

MrChips

Joined Oct 2, 2009
19,426
You can also make one from a out of date Propane BBQ tank.
I made a small one for a tank reservoir out of a propane hand torch bottle, for an air brush compressor about the same size as the OP's.
Max.
Hey Max, I have a couple of expired propane tanks. What I do with BBQ tanks that are just about to expire, I refill them and use them as backups. Now that they are empty, your suggestion sounds like a great idea.

Can you elaborate on how you fit a hose with tire nozzle on to the tank?
And how do you pressurize the tank? I have a 12V battery operated combo inflator/flashlight that I use for pumping bicycle and car tires.
 

dl324

Joined Mar 30, 2015
9,155
@dl324 Tanks have to be pressurized. Would need a significant compressor to charge the tank, or have the hassle of going to the gas station (one WITH an air pump) and charge up the tank. Here in the US I haven't seen anything better than the 25¢ coin operated pumps. If you go to a tire shop you can get higher pressures but I'd bet they wouldn't care for filling a tank they have no idea of its condition. There might be a possibility of a tank rupturing during pressurization. That alone - if I were the shop owner - I'd say "Sorry, take your tank to someone else."
I've had an air compressor for more than 20 years now, so it's been a long, long time since I had to fill the air tank up at a gas station. When I did, air and water were still free and the station I went to didn't object. Several mentioned that it was a good idea. It isn't a problem getting 125 PSI from any decent air compressor.

I use the air tank whenever I need to fill tires or put air in my well pressure tank. It's a lot more convenient than lugging the air compressor around or dragging 100-150 feet of compressor line to put air in a few tires. My Wife and I'll run the compressor when we need a lot of air to blow debris off the deck or out of an engine compartment. I use it to clean dust from the vacuum cleaner every few cleanings.
 

Tonyr1084

Joined Sep 24, 2015
3,680
Here's a YouTube video of how one guy did it. In my opinion he did all the right things. One thing to NEVER do is apply flame to an empty tank, there is residual propane gasses in the tank, just not under pressure. Ventilating the tank vigorously to dry out water will also remove the last vestiges of propane. One other important point he made was not to grind or weld on the tank as it can cause failure.

The smartest things he did were to coat the tank with a rust primer and also to pressure test it to 400 PSI with the tank filled with water. Otherwise, had it been pressurized with just air, should the tank fail you could have a 500 horsepower rocket flying around the room rather vigorously and uncontrolled.

 

Tonyr1084

Joined Sep 24, 2015
3,680
@dl324 Oh it's absolutely doable. And if you have use for it - as opposed to - as you say - lugging 150 feet of compressor line, the tank is the way to go. But the TS already has a system in place. He wants to add the convenience of a switch. As you may notice, the video takes some time to properly prepare a tank for use as a pressure bomb. And it needs to be done right, or else there could be a rather bothersome ruckus in the workshop chasing around a tank that is vigorously venting its internals. Or worse, being chased by that tank.
 
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