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DIY GSM/Cellular Preheater for <$125

j-red

Well Known Member



Winter is almost over, but it was still <30f outside last Thursday. In order to get a flight in before work, I had to drive out to the airport at 5 AM to plug in the preheater, drive back home (it's only 10 minutes, but still....), and then return at 8 to fly. Leaving it on all the time is out of the question since it's a borrowed hanger and I don't want to push my luck. The alternative of letting the heater run all night the night before would still require a trip out the night before a flight to turn the heater on. If this were 12 months ago, this wouldn't be a problem. You see, a couple of years ago i stumbled across one of these babys: https://tinyurl.com/h4anbkq

Wake up, shoot it a text message, and it turns on any one of three recepticles. Worked great and cost pennies a month! Why am I not still using it, you ask? Because it's a 2g device and as of this past December, the nations 2g networks were largely dismantled it no longer gets service out at the field. TMobile still has their 2g network up for another year or two, and the device works here at home, being closer to town and all, but even here it's spotty. Another downside was that it was only rated for a total of 15a for all three outlets. I never had any problems with my small diy space-heater-turned-engine-preheater, but it was pushing the limits for sure.

Now that N94CR is flying again, it's painfully obvious that I need something similar that works on the current cell networks. Several are available marketed to airplane owners, but the cheapest is almost $300!
And then I found this: https://www.amazon.com/gp/product/B01N5LGJLA/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
$115, and free prime shipping. Purchased it on Saturday and it showed up on Monday. I must have gotten the last one from Amazon because they're out now, but it's available from some import company as well...

Here's what you need to know:
1. You have to supply a sim card. It says ATT, but works perfectly fine with my old T-Mobile sim card. In fact, it works far better with the T Mobile around here... I actually purchased an ATT sim and tried it first, but it kept dropping the signal. Hasn't done that at all with the T Mobile.

2. The power requirements for the board are 12v dc, NOT 110v AC which is what you'll be switching with it. A google search for similar items reveals that there are units available with a built-in inverter (Search for something like "GSM-AUTO-AC"....) Instead of sending it back and ordering one of those, I just dug around in the closet for an old power cord for some appliance that used 12vdc and cut the pigtail off.

3. You have to read Chinese! Not really, but the instructions leave a lot to be desired. For instance, it tells you what the led's are assigned to, but not what their flashing patterns mean! There's also a button you have to push on the device before calling it to put your phone number on the "Whitelist" so that you can then control it. That isn't explained well.

4. The wiring diagram is pretty simple, but requires you to make a few pigtails for power input and output. I chopped up an old extension cord and picked up ends from the local big box store for $10 total. There are two 30amp relays inside, and they can be controlled individually to open and close, and even set to turn on for a certain time limit then off automatically.

5. The device is controlled by text messages which have to be formulated exactly perfectly and are quite obtuse. The good news is that there is a free App for iPhone and Android that makes this quite easy.

I got it built and tested tonight and it seems to be working great here at the house. The real test is how well it picks up a signal at the hanger. Verizon gets fine service out there, so it's promising. Included in the package was an external antenna with about 8' of cable to help locate it for best service. I'm hoping the short one that fits inside the box will be sufficient. With any luck, I'll be able to roll back over and snooze comfortably knowing my engine is warming peacefully as well.
 
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I wouldn't recommend anyone wire a unit like that. The grounds appear to be clipped - they should be properly bonded. You are also switching the neutral conductor instead of the hot. Either error could lead to a shock hazzard.
 
They sell a unit on amazon that requires no wiring and works perfectly for like $40.i use it and it works great.
 
Thanks for the input. Just so no-one gets led along in the wrong direction, I removed the wiring photo. After wiring an airplane, DC circuits are on the brain, I guess... The unit is switching the hot, not the neutral, but that's because I used the white wire for the hot and black for the neutral in the receptacles which must be opposite of standard protocol. I'll do what you suggest with the grounds.
 
There are also 120v versions available from the Chinese manufacturer. I don't have the link handy at the moment, but if somebody wants it, please send me an email. (No PMs)
 
Merlin3,
Are you using the white and blue unit I linked to first? If so, I have one but can't use it here because it only works on the 2g network which doesn't exist where I'm located anymore. If that's not the one you have, please share!
 
rleffler,
I referenced those, and would definitely recommend that anyone making one of these go that route. I would have if I had realized the possibility when I bought this.
 
Yep i am using a similar unit and it still works on 2g here. Have you looked to see if they have one that will work on newer network?
 
OK, the manufacturer of the GSM Auto AC 4G box is Waferstar in China:

http://www.waferstar.com/en/GSM-AUTO-4G.html

Scroll down till you see the item identified by GSM-AUTO-AC 4G version:

http://www.wafer-shopping.com/4g-ve...stralia-europe-canada-p-351.html#.WMnpZWe1tEY

They are $140 and they provide free shipping. You will need a Sim card for the phone carrier of your choice, usually ATT or T-mobile. You can contact me for the wiring instructions.

This is the same box sold by another individual for $350 or so plus shipping.

regards

~Marc
 
I still see the link in the original post. I bought mine (same as listed above) through amazon for $115 shipped, but I see it must have been the last one available...

Took it to the hanger today for a test and it works perfectly. Good strong 4g signal out there whereas the old 2G switch I used out there last year is now getting nothing sitting in the exact same spot.

Assuming this wind dies down, I should be able to send a text in the morning and show up a few hours later with a nice warm engine!
 
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