# Using cheap mobile phone to send an alarm

#### Western

##### Member
Hi,

A dairy farmer friend asked if I have any ideas about remote monitoring for when he is flood irrigating.

He wants a sensor at the end of the paddock, that triggers when the water reaches it.

He’d like it to cause an el cheapo mobile phone to send a message to his own phone … so he can head off and close the sluice gate.

#### Pommie

##### Well-Known Member
Arduino with shield should be less than AU\$50.
How will you detect the presence of water? Float switch?
Has he considered a system to automatically shut off the sluice? Maybe a simple timer.
Are you located near Brisbane?

Mike.

#### Western

##### Member
Well, the price is right.

Not sure for detection ... possibly just a moisture sensor of some type ... though could be a float switch.

I'm not sure on shutting off the sluice gates ... from what I recall ... his are manually operated ... think vertical screw with a 12" wheel that you screw up or down.

Some flooding may be done by turning on a pump ... but most are manual I believe.

We're 100 km out of Adelaide on the River Murray

#### dr pepper

##### Well-Known Member
There are plenty of projects on the net where you hack a cheap 'phone, and use one of its hotkeys as a means of sending a text, a simple circuit interfaces to the hotkey via a pair of wires soldered to its contacts.
For that matter I dare say you could rig something completely mechanical, a ball float in a sump with the 'phone attached to a bracket could be arranged to press said hotkey sending the message.

#### Western

##### Member
Haha ... a mechanical system did cross my mind ... but I have enough trouble making my phone work while I'm watching ... I don't like my chances of a getting a remote system working reliably.

I like the idea of wiring up a hotkey so that it has more chance of triggering properly. Didn't realise that was an option. Thank you for that.

#### Western

##### Member
There are plenty of projects on the net where you hack a cheap 'phone, and use one of its hotkeys as a means of sending a text, a simple circuit interfaces to the hotkey via a pair of wires soldered to its contacts.
Ok ... I've spent ages looking ... but can't find any so far.

#### dr pepper

##### Well-Known Member
You have a point, the problem putting 'phone' into google brings back all kinds of stuff.
I did find this, obviously instead of a cloths peg contact you'd use a float switch, you might have to dig a little further.

#### Pommie

##### Well-Known Member
To future proof your design for when they go to 4G, 5G 6.... etc. You could use any phone and turn on tethering and use a WiFi enabled Arduino such as the Wemos to talk to it. You would need to use one of the online SMS services to send the SMS but they're really cheap.

Edit, alternatively, use the Wemos to send an email instead of SMS - lots of examples on web.

Mike.

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#### JonSea

##### Well-Known Member
How about a phone with some kind of a bluetooth device? Some phones used to take AT command codes via the headphone Jack but I'm pretty sure those no longer exist.

Hmmm. Most phones will take a contact closure via the headphone jack and software can use it as a trigger (and there are bluetooth devices that work the same way). Could B4A (Basic for Android) use this input to trigger an SMS?