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12v relay connected to cell phone


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wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 11:38 AM / IP Logged  
Hello Gents:
We have wireless(for Internet) transmitter that every now and then the radios get stuck and it needs to be reset. All we need to do is unplug it and plug it back in. The main feed is 110 ac, but the actual system runs on 12vdc which we have set on deep cycle batts for UPS. So, here is my idea to make a remote reset device, any help you can provide will be greatly appreciated.
1) Get a cheap cell phone.
2) Gut it, and connect a relay to the ringer/vibrator, this way everytime the phone rings it will cut the power to the radios momentarily and reset them.
3) Connect the cell phone to the 12v system with a car adapter, this way it will always be charged.
The tipical method is to reset the radios via the network, the problem is that if the radios are not working, the network will not be working. There is no pager/beeper coverage in that neck of the woods and only some cell phone companies serve the area. Also, there is no landline phone service.
The biggest drawback to this is that everytime there is a "wrong number" call it will reset the system. We are willing to live with this. Ideally, to avoid false alarms the cut-off device would have some sort of delay so that it would cut the power off if it received two calls within 1, 2, or 3, etc minutes(whatever is easier).
Thanks
Chele
wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 11:43 AM / IP Logged  
PS
I did read the 3.3->12v relay and that is what gave me this idea, I am just expanding the concept a bit.
chele
defective 
Silver - Posts: 642
Silver spacespace
Joined: August 20, 2003
Location: Canada
Posted: August 19, 2004 at 12:09 PM / IP Logged  
whoa.... wheres dyohn when you need him..... i dont understand what your building.....
wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 1:43 PM / IP Logged  
The idea is that when the cell phone rings, it will open the circuit(activate the relay), this will cause the radios(which at this point are stuck) and get going again. I do not need to log on to a computer on to a computer or anything fancy, just disrupt the power supply to the radios. This will just be a remote control to open the relay(s).
xetmes 
Silver - Posts: 586
Silver spacespace
Joined: May 18, 2003
Posted: August 19, 2004 at 1:56 PM / IP Logged  

did you try it? some phones can be linked via rs232 and such and might be a little less invasive... but pulling it apart and going for the vibrating motor would probably work, just use a transistor BJT or MOSFET, infact depending on the system current draw you could possible just use the transistor without a relay...

Im kinda confused reading that though...

markcars 
Silver - Posts: 662
Silver spacespace
Joined: December 11, 2002
Location: New York, United States
Posted: August 19, 2004 at 2:56 PM / IP Logged  
How far away can you be at most, when you want to trip the reset on your radios? If you aren't going to be more than 5 miles away, I would suggest using two GPRS radios at each end with different frequencies on each one. Only when both frequencies are "ringing" at the same time, you could trip your relay the way you already have. Chances of two strangers within 5 miles rining at the same time on two different frequencies is going to be near impossible. However if your tripping distance is more than 5 miles, you could use 2 cheap cellphones and have both connected to 2 separate relays with a timer on each one for lets say 30 seconds. That way you could dial the first number, that would set the first relay to be engaged for 30 seconds, while you make your second call to the second relay (within 30 seconds) and then both relays being in series would set the trip switch (which could be a third relay) to your system. That would even eliminate the wrong number issue.
wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 2:59 PM / IP Logged  
Sorry fellows
It makes perfect sense to me:) I didn't mean to make it confusing. What can I do to clear it up? I have not tried it yet, I was curious as to whether this could be done or not. I am willing to scrap a cell phone so I'm not too concerned about the invasive part, besides, I would need some sort interface to the rs232 if I went that route. I'm strugling enough with just the relay thing. Also, I don't know enough to attempt it without some guidance!!
wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 3:40 PM / IP Logged  
It will be a regular cell phone with its own number just like the one that you might have. The only difference is tha it will have a relay(?) connected to it so that it will interrupt momentarily the power to the radios and force them to reset. The transmiter is about 1 hour away. The beauty of a cell phone is that I could trigger it from anywhere by dialing the cell phone #. It would be great if I could avoid false alarms.
To avoid(or reduce) false alarms the cut-off device would wait for a second call within a certain time frame, 1,2,3 etc minutes. This would be nice, but not necessary.
So, here is my thought:
a) phone rings and hang up, no need to complete call.
b) starts timer.
c) gets second call(step "a") within 2(?) minutes
d) relay opens, cuts power to radios for 5(?) seconds
   this will force the radios to reset.
if the phone does not ring(step "c") again within 2(?) minutes, the timer stops and nothing happens.
Steps "b & c" would be great as it would cut down on false alarms.
I hope this clears it somewhat and I'm not making it more confusing than it already is.
Thanks
Chele
xetmes 
Silver - Posts: 586
Silver spacespace
Joined: May 18, 2003
Posted: August 19, 2004 at 3:56 PM / IP Logged  

actually I was thinking about this a little more, even though I am still confused as to the exact implication and if it could be done another way....

You could use a modem on the phone and that way can use a better system to activate and elimnate false triggers,

something like this: http://www.wirelessemporium.com/store/catalog/product/details.asp?itemid=2756

but I dont know how cheap you want it to be...? there are wireless modules that you just shove a sim card in and can control things by calling, but I think that would be overkill...

maybe just the ringing time interval thing would be the cheapest....

wifi 
Member - Posts: 11
Member spacespace
Joined: August 19, 2004
Location: United States
Posted: August 19, 2004 at 4:18 PM / IP Logged  
Thanks xetmes. To tell you the truth, even the srs32 is overkill. I don't need the radios to execute any commands, just their power disconected for 5 seconds or so. From what I have researched my best option would be to get one of those prepaid cell phones for about $40-80,(no contracts) low monthly fee(don't care about the minutes). So long as I get signal at the transmiter site I'm OK.
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