Mostly a lurker around here and not sure if this even interests anyone, but at my local field we have been talking about having something like this available for a reasonable price for a long time so I finally decided to have a go at it. Thought I would share in case anyone wants to copy!

Even though I only have a short drive to the airport, it's annoying to have to go out twice in order to plug in the pre-heater a few hours before I want to go flying. To solve my problem, I purchased a cellular switch from Amazon "Andoer Wireless Mobile Cell Phone PDA GSM Remote Control 3 Socket Power Outlet Smart Switch AC 110-220V". It cost right around $50, the t-mobile prepay SIM card was another $5 and it has a monthly minimum of $3 which includes 30 texts (.10 cents/text). The unit claims it's rated for 2200 watts, but I quickly found out that a 1500watt space heater blows the internal fuse in about a second, so it was time to get creative.

I purchased 3 16amp@220v relays which should handle just about anything I could throw at it and the accompanying sockets. I also picked up some junction boxes, outlets, AC plug ends and a 20 amp breaker.

I installed the components on a sheet of 3/4in plywood, and hard wired the power directly to my breaker box via the 20amp breaker, here is the finished result:



As you can see the Romex in the upper right is what gets wired into the breaker box, (you could put an AC plug onto the end of this if you wanted and just plug it into any 110 outlet if you desired) it feeds the first junction box/outlet which is always hot, and designed to power the actual cellular switch box. From there hot power is fed into each of the three relays. The cellular switch box now only controls the coils of the relays, which can handle much much more power than the wimpy cellular switch box itself can. Each of the relays then power the respective socket below.



It works like a dream and now I can turn my airplane heater on from anywhere, just by texting the switch box. What's really nice about this particular switch box is I get a text message response back telling me which switches are in what position. So I know for a fact whatever it's powering is actually on/off. I know these switch boxes aren't really a new thing but I have yet to find one that can handle enough current to actually run a 1500watt heater for a reasonable cost. This whole project cost me about $100 and a few hours time, it's extremely simple to build and wire up.

The relays are safer! Great idea(s). Thank you.

My strip is a 1/4 mile swath of grass in the middle of the desert. No power nearby, but a canal only1/8th mile away. Not a fan of flood irrigation for an airstrip, I elected to build a sprinkler system powered by a 300gpm trash pump. The trash pump is Honda motivated, and I utilized a very similar gsm switch to start it and turn it off. My switch is 12v, and I draw that power from the Honda's battery, but with relays, you can switch as much as you care to.

 Works like a charm...

 The system I utilized is a 7 relay set up, and the first relay opens on a caller id system. The box recognizes your number, hangs up on you, and fires the relay. Basically a free operation. 

 There were some growing pains making it all seamless, but for not much pocket change, I can now handle my irrigation chores from anywhere I can get a phone call out.... How great is that?


 Take care, Rob

Very nice, thanks for the write up. I've been thinking about the same type of set up. What relays did you use? Where purchased?

Newbizor
Great Idea, just really appreciate all you guys that have the knowledge some of us don't and that you share.
Rob,
any chance you can take a picture and or post your irrigation parts list? Have a similar situation that might be able to use part of your system on?
Thanks

callerID box needs to be wired to a landline, right? Otherwise you'd need a wireless sim card?
Great ideas on both. This gives me some ideas. Thanks for posting.

One of my hangar neighbors rigged up something like this.
He says just calling it turns on the preheat, it doesn't even have to answer so no call charged either to his cell or to the cellular gizmo wired to the preheater. The bad part is that a wrong number could activate it, but it's on a timer to shut off automatically after X amount of time so no big deal.

UW, these are cellular switches.
HR, the system I use has caller ID making it a secure system
You can select the number/s that are allowed to operate it
Hi GT,
Rather than derailing this thread, I'll put together a summary of what I did and shoot you a message. It's pretty much 'barnyard engineering' but it keeps the grass watered, as well as providing switching capability for the gate and some lighting.

One thing that is probably worth mentioning on this thread though.... If someone is considering using cellular switching, it is probably worth first investigating which network works best in your intended area. A GSM box needs an ATT, TMobile, etc sim, and a CDMA box will want Verizon. Where we are, CDMA is king, but the specific site is in a 'shadow' consequently GSM worked just a tad better. Neither would be 100% reliable if it wasn't for an external antenna. If service is of equal quality, then it might be worth investigating which service you can get cheaper.

Take care, Rob

I see most of the questions were already answered by Rob.

This particular cellular switch is GSM, no landline required, just cellular service for the particular network you are using it with. In my case I use a pre-pay SIM card from T-Mobile. It cost me $5, there was a $10 activation fee but the minimum monthly requirement is only $3 after that. It works through SMS text messaging, which thought t-mobile is $0.10 per text. With the $3/mo it covers 30 text messages, use it more just load up a few more bucks a month. I think it's pretty reasonable, $0.10 vs driving my ass to the airport just to plug it in and home again for a few hours while it warms up. The device recognizes your phone number which you have to initially set as a accepted number in order for it to listen to your commands, so an accidental random call/text will have no effect on it. You just text the device a message, basically with what you want it to do with each of the three outlets. N=on F=off and X=ignore. So if I want all three switches on I text it NNN, once the deed is done it responds with a text message telling me "Switch 1-ON, Switch 2-ON, Switch 3-ON" so you know it actually worked.

I picked up the relays and relay sockets at a local electronics shop, they are branded as "Finder" and are 16amps at 250volts, which is something like 4,000watts per outlet. A little overkill but a nice safety margin as well.

Thanks for the compliments, it really is simple though. The relays are just switches operated electronically, and are wired no different than a standard switch, so little knowledge or skill is required....trust me on that.

I've seen cellular switches for sale ranging anywhere from $50-$500, but even some of the more expensive units really aren't designed with a high power load in mind, with this setup I can run some high wattage stuff and don't have to worry the hangar/plane will be burnt to the ground when I eventually do show up.

Nice.

I've had a cell switch for awhile, but it has blown fuses, etc., and is currently sitting on the table to get new fuses installed. So where do you get the heavy relays? Parts numbers? Thanks.

Cary

Cary wrote:I've had a cell switch for awhile, but it has blown fuses, etc., and is currently sitting on the table to get new fuses installed. So where do you get the heavy relays? Parts numbers? Thanks.

Cary

https://www.nriparts.com/electrical/con ... -amp-relay

That is a link to the actual relays I used, I picked them up from a local electronics shop. I just walked in, explained what I was doing and the fellow at the shop handed me these things. Something to note when you are looking for a relay would be the type of power the coil is designed to be driven by (AC vs DC) and the amperage rating at the given voltage. These particular relays are rated for 16 amps at 250vac, which is over 30amps at 110/120vac, well over what I plan on putting through them. I'm actually only going to wire this whole board to a 20amp breaker since I used 12ga wire.

Newbizor wrote:

Cary wrote:I've had a cell switch for awhile, but it has blown fuses, etc., and is currently sitting on the table to get new fuses installed. So where do you get the heavy relays? Parts numbers? Thanks.

Cary

https://www.nriparts.com/electrical/con ... -amp-relay

That is a link to the actual relays I used, I picked them up from a local electronics shop. I just walked in, explained what I was doing and the fellow at the shop handed me these things. Something to note when you are looking for a relay would be the type of power the coil is designed to be driven by (AC vs DC) and the amperage rating at the given voltage. These particular relays are rated for 16 amps at 250vac, which is over 30amps at 110/120vac, well over what I plan on putting through them. I'm actually only going to wire this whole board to a 20amp breaker since I used 12ga wire.

Thanks!

Cary

So, I am understanding a guy could build one of these to use a landline type phone and its caler ID?

I have a phone line run into my hangar so that would be the way I would want to do it. What type of switching gizmo is needed.

Newbizor wrote:...These particular relays are rated for 16 amps at 250vac, which is over 30amps at 110/120vac, well over what I plan on putting through them. I'm actually only going to wire this whole board to a 20amp breaker since I used 12ga wire.

Very nice and thanks for sharing. For safety and educational sake, I feel compelled to correct a slight misunderstanding. The relay will still only be rated 16 amperes at 110/120vac. For what it's worth, you are pushing that relay pretty hard with a 1500w heater (12.5 amperes at 120vac), for longer life and less chance of fire, go with 25 to 30 ampere rated relays.

I have one of these, which I use without the relay successfully.

However, if I was relaying it, I would have picked up a DC output remote gate switch or similar.

You can get a cheap sim at alarmsim.com