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Micro power transmitter for remote sensor help
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beananimal

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PostPosted: Wed Apr 20, 2011 2:40 pm    Post subject: Reply with quote

jenalcom wrote:
Why do people always want to overcomplicate things with electronics? Everything has got have a micro in it these days!!!

Keep it simple - a float switch, a length of two wire cable (perhaps with plugs and sockets in line) and a relay to switch the power on/off. End of problem - especially for two metres distance.

If you wanted to go a couple of hundred kilometres then thats a different scenario.


In one of the posts above I pointed out why the simple solution will not work (or at least is not attractive).

The container is in a saltwater environment where thare is a lot of humidity and splashing. The container needs to be removed and washed 3-4 times per week. It is washed in a tub with a pressure hose. So any connector is going to get wet and corrode. It is also a pain to plug and unplug the connector so often. It would be NICE to be able to have an sealed solution with no wires and a battery that only needs to be replaced a few times a year.

I had assumed (maybe incorrectly) that such a low power transmitter could be setup to send a simple hearbeat signal every second or so, and do so for a very long period of time on a small battery.

If what I am asking is not possible, then I will have to use a hard wired solution and live with it.
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glena

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PostPosted: Wed Apr 20, 2011 3:31 pm    Post subject: Reply with quote

You may want to look at this technology. Its battery can last up to 4 years and transmits when it gets low. There is also tamper detection.

http://www.alarmcontacts.com/product.php?productid=1035

-Glen

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laborratte

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PostPosted: Wed Apr 20, 2011 3:43 pm    Post subject: Reply with quote

1. I would NOT just heartbeat a carrier signal, your receiver could easily disturbed by any mobile phone. Send a short message (like every remote control).

2. A radio module comsumes typically 10mA@5V. Assuming you send a message for 20ms per second, you can calculate:

20ms * 10mA = 0,2mAs per Second = 0,2mAh per hour

This is 4,8mAh per day or 1752mAh per year. 3 AA cells shoud do that.

If you have other radio modules or time schedules, just recalulate.

3. I personal wouldn't mount any sensors on a saltwater-splashing-and-pressure-hose-cleaned-cup at all. There are plenty of industrial sensors (optical/capacitive) which can "remotly" detect liquids. (for industrial amount of bucks, of course).
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beananimal

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PostPosted: Wed Apr 20, 2011 4:16 pm    Post subject: Reply with quote

laborratte wrote:
1. I would NOT just heartbeat a carrier signal, your receiver could easily disturbed by any mobile phone. Send a short message (like every remote control).
Does it need to be a literal message, or can the "hearbeat" carrier be coded in some type of pattern that the reciever looks for. I ask in hopes of keeping the sending side topology very simple and power friendly.

Quote:
2. A radio module comsumes typically 10mA@5V. Assuming you send a message for 20ms per second, you can calculate:

20ms * 10mA = 0,2mAs per Second = 0,2mAh per hour

This is 4,8mAh per day or 1752mAh per year. 3 AA cells shoud do that.

If you have other radio modules or time schedules, just recalulate.
Is there a specific product that you would steer me toward?

Quote:
3. I personal wouldn't mount any sensors on a saltwater-splashing-and-pressure-hose-cleaned-cup at all. There are plenty of industrial sensors (optical/capacitive) which can "remotly" detect liquids. (for industrial amount of bucks, of course).
I had considered several options, but thought that if I could build the simple transmitter, it would be inexpensive and could be sealed well in a tiny gasketed container.

Thank you for the input, it would appear that at least in concept, this project is possible.
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beananimal

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PostPosted: Wed Apr 20, 2011 4:20 pm    Post subject: Reply with quote

glena wrote:
You may want to look at this technology. Its battery can last up to 4 years and transmits when it gets low. There is also tamper detection.

http://www.alarmcontacts.com/product.php?productid=1035

-Glen


I am curious as to how often this unit sends a signal to the panel?
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kimmi

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PostPosted: Wed Apr 20, 2011 6:26 pm    Post subject: Reply with quote

This is a friendly forum

The Global Announcement Say :
Please behave polite.
Do not offend anybody.
There are BASCOM users from all over the world.
Do not discuss politic, religion or other matters that have nothing to do with BASCOM.

Happy Easter to All users

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albertsm

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PostPosted: Wed Apr 20, 2011 8:45 pm    Post subject: Reply with quote

I have removed a number of posts from this topic.
Please continue this thread with relevant info and respect.
I do not really like to remove posts.

I also moved this topic to Various since it has not much to do with BASCOM-AVR.

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laborratte

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PostPosted: Thu Apr 21, 2011 11:59 am    Post subject: Reply with quote

beananimal wrote:
...or can the "hearbeat" carrier be coded in some type of pattern that the reciever looks for...

yes

Quote:
Is there a specific product that you would steer me toward?

You have to look for products that are allowed in your country. In Europe a good starting point would be http://www.aurelwireless.com/rf-wireless-modules/rf-wireless-modules.asp. But there are a lot of modules on the market.

These burglar alarm type transmitters proposed by glena are also a very good technology for your problem. Maybe the best one.
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beananimal

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PostPosted: Thu Apr 21, 2011 1:52 pm    Post subject: Reply with quote

Thank you for the response. I think I have a starting point and will post back once I find a few modules that appear suitable.
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beananimal

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PostPosted: Fri Apr 22, 2011 5:08 pm    Post subject: Reply with quote

So it looks like I have 2 basic choices:

1) use one of the very cheap 433mHz type transmitters that sparkfun and others sell. These thing appear to be not much more than a simple transistor and inductor type transmitter. From what I read, they work but can be rather hard to get talking due to noise. The nice part is the low powr consumption of as little as 4mA during transmit. Power could be cut easily during the sleep mode, but noise is likely at each wakup. I thought maybe a fixed front end (555 timers or other oscillator) could be used to set the hearbeat. Maybe hard to deal with on the reciever end.

2) use a Zigbee (Xbee ZB) type of transmitter. Has a sleep mode that consumes alost nothing, but transmit current is above 40mA. This makes power magement much harder. However, communication is much less prone to drop-out due ot noise, etc. This could be setup with a picoPower AVR that wakes up every 2 seconds and sends an "OK" or similar serail message and then goes back to sleep.



I have no experience with either type of transmitter but am leaning towads the Xbee ZB module connected to a picopower AVR. What I don't know is how quickly I can enable this guy, send the ACK and put it back to sleep. Do any of you have any experience in this area?
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kimmi

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PostPosted: Fri Apr 22, 2011 11:31 pm    Post subject: Reply with quote

Hi ,
Just a Idea ,
You say it only have to work a few meters ,
do you think a IR or IRDA led can do the job for you ?

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beananimal

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PostPosted: Sat Apr 23, 2011 6:14 pm    Post subject: Reply with quote

I guess I should consider IR. The area does have several metal halide and fluorescent fixtures that output UV and are in very close proximity 1 or 2 feet from the devices (sensor and controller) so a little bit of testing would need to be done to ensure that there is no significant interferene.
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