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Topic: Which is better for a limited range of 10 inches (Read 1 time) previous topic - next topic

Sovrac

Aug 16, 2012, 08:35 pm Last Edit: Aug 16, 2012, 08:53 pm by Sovrac Reason: 1
I am looking for a wireless solution that comes with a limited range (for pairing) of 10 inches

From what I understand:

NFC: 4 inches
Bluetooth: 30 feet

Can I lower the BT's power consumption to meet my exact needs of 10 inches? Does another solution exist?

Sovrac

The Clever Monkey


I am looking for a wireless solution that comes with a limited range (for pairing) of 10 inches

From what I understand:

NFC: 4 inches
Bluetooth: 30 feet

Can I lower the BT's power consumption to meet my exact needs of 10 inches? Does another solution exist?

Sovrac


BT has low power modes, even for active paired connections. I suppose it depends on the hardware you intend to use and whether it supports those modes?
I yield() for co-routines.

Sovrac

#2
Aug 16, 2012, 09:07 pm Last Edit: Aug 16, 2012, 10:51 pm by Sovrac Reason: 1


BT has low power modes, even for active paired connections. I suppose it depends on the hardware you intend to use and whether it supports those modes?


So is it a predefined power mode that can only be lowered to X watts? Or can I lower the power consumption to meet my exact needs of no more than 10 inches?

Grumpy_Mike

The BT protocol negotiates based on signal level what the power is, you don't have to do anything.

Sovrac


The BT protocol negotiates based on signal level what the power is, you don't have to do anything.


I am planning to achieve the pairing with no user input, once the 2 BT's are within a range of 0-10 inches. If other discoverable BT's (let's say my phone) are within the BT's approximate range of 30 feet, how will I know who, or what I am pairing to until it's already been paired?

This is why I want to limit it's range to 10 inches, to eliminate accidental pairing (since no user input for pairing will be required).

Grumpy_Mike

Quote
how will I know who, or what I am pairing to until it's already been paired?

Normally the device asks the user for permission.

Sovrac

#6
Aug 17, 2012, 03:51 pm Last Edit: Aug 17, 2012, 04:00 pm by Sovrac Reason: 1

Quote
how will I know who, or what I am pairing to until it's already been paired?

Normally the device asks the user for permission.


As long as the device/s are set Secure Simple Pairing (SSP) to Just works, user permission will not be required. I want to achieve seamless pairing similar to NFC+WIFI on the Galaxy S3, but since NFC is limited to a few centimeters, I am hoping BT will help me solve this problem. Can the BT's range be limited to my exact needs?

*BT Paring Source http://en.wikipedia.org/wiki/Bluetooth

Grumpy_Mike

Quote
Can the BT's range be limited to my exact needs?

No I would not think so. Radio is not that precise.

Sovrac


Quote
Can the BT's range be limited to my exact needs?

No I would not think so. Radio is not that precise.


Got it. I went ahead and ordered 2 Uno kits. Next will be 2 NFC shields and 2 Wifi Modules to to get this off the ground. I'll keep researching on tech to meet my needs. Maybe NFC wil do the trick, supposedly it's range can be up to 20cm (theoretically)

jackrae

If you want such a short range, why use RF.  At only 10" you could use ultrasonics.  Operating at a base modulation frequency of 40KHz or so I'm sure you could get a decent data rate and no interference from RF gizmos.

Certainly discrimination from other users might be a problem, but how many people or devices do you know who might be within a few feet of your application.

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