Child Proximity Band??

Hello Everyone,

I have a project coming up. I will be using an Arduino for it. I want to make a bracelet or some type of item that can be attached to a kid. The parent will also have a device in which will sound an alarm when the child(child's device) travels a certain distance away from the parent(parents device). What kind of equipment should I use for this? RFID, GPs, BlueTooth? I don't know what else is available that could work and would be cheap/easy. I would also like to try to make the distance programmable so that you can change the distance at which the two devices have to be apart for the alarm to go off. Any ideas, suggestions?

I would say anywhere from like 30-100ft and probably the ability to change code so the distance alarm will sound can be changed.

Define "certain distance"

I would say anywhere from like 30-100ft and probably the ability to change code so the distance alarm will sound can be changed.

As I am learning, distance is hard to calculate between 2 points. The simplest is 2 GPS devices and some form of wireless communication, like Bluetooth. However it will require satellite locks for both units to work properly, so won't work in some buildings. A simpler method would be to ping constantly, and if the remote device doesn't hear the ping, then set off the alarm. However distance would be an unknown variable, though up to a certain range.

Hmmm, so I could get maybe devices that have a predefined distance at which they can transmit. And when the one can't "hear" the other transmit then the alarm goes off? What would be best method for this? I'm thinking maybe blue tooth since it usually have like a 30ft range I think?

I could get maybe devices that have a predefined distance at which they can transmit.

Not at reasonable cost or in very constrained conditions, no.

hmmm dang

What would be a good method of going after this then? http://www.specialtyalarms.com/site/1313932/product/30-210

That unit only costs $20? How can it be so cheap

How can it be so cheap

Why don't you ask them how repeatable that six to thirty feet is?

Hi,
Maybe look at the low-cost nRF24L01 transceivers. http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo

You would need an Arduino Pro Mini or etc. to control it and make the beep / flash / vibrate (About $10)..

The small Nrf24L01 boards ($4 or so) are programmable for power output so they could probably go from 100 feet line-of-sight down to a few feet if power set lower.

It would take some software development, but could be flexible..

kpelkey151:
What would be a good method of going after this then? http://www.specialtyalarms.com/site/1313932/product/30-210

That unit only costs $20? How can it be so cheap

1.5 rating at Amazon and after read review, I will pass.
http://www.amazon.com/Self-Defense-Store-YS-088-Panda-Child/product-reviews/B00081736K/

Some time back I worked briefly on a device that would sound an alarm when a briefcase got a definable distance away from it's owner. It was a security device that triggered a Stun-gun type of power supply (which was the reason I finally refused it) it was based roughly on a child proximity detector that used a PIC 16F84 (2313...?) and the transmitter and receiver were of the cheap 433MHz OOK devices. After reverse engineering the protocol by monitoring the output of the child transmitter with a "cheap 433 MHz receiver of the type used in the device and an oscilloscope it was determined that the modulation was a PPM code and that the code was a precise preamble pulse of 100 to 350 mS and several different width pulses at different delay's from the 'preamble' all were a part of the device address or ID. The first 'data pulse was 50 mS wide and always 100 mS from the end of the preamble and a third and or fourth pulse of 1 mS duration.
The details are almost obvious... the short pulse was position dependent and a part of the ID and it was the distance 'flag'...
The receiver used in the 433 OOK comm devices is a super-regenerative type and a characteristic of that receiver is that it has a slow response to short weak pulses. In essence the receiver takes a finite time to 'lock' on the signal. If the energy received is weak enough the pulse will not be detected or not at the right time... Remember this is Pulse Position Modulation, timing is critical and the answer to the issue.
The company bought a modified version that I came up with that exploited that phenomena to 'range' the transmitter by using three different pulse widths when the shorter pulses disappeared it armed the Stun device and when 3 separate codes were missed it triggered the Stun-gun power supply wired to the handle of the briefcase.
All the details are to the best of my knowledge in the public domain. I see no issues with developing your own protocol.. PPM coding is a common RC control technique... among other things.
The parts are trivial and the code as well but I highly recommend an engineer with both data and RF experience because the answer really is in both domains. Highly Doable and interestingly trivial too.

Doc

Bluetooth low energy technology (4.0) - Security and proximity applications

Smart Key Finder tags are the most advanced object finder to locate objects directly from your smart phone. It uses the Bluetooth 4.0 technology (also called Bluetooth Low Energy - BLE) which can last over 12 months on a coin cell battery. The iOS Smart Finder app works with the Smart Key Finder tags to implement Find-Me and Electronic Leash services. The Find-Me service can be used to locate objects up to 50 meters (164 feet).
It built on the highly power efficient TI CC254x system-on-chip solution.

http://acesensor.com/product/smart-finder-ios-app/

Google adopts Bluetooth Smart (4.0), hints of a new Android version within two months (By Chris Welch on May 15, 2013 07:16 pm)

According to a just-issued press release from the Bluetooth Special Interest Group (SIG), Google has committed to updating Android with support for Bluetooth Smart (also known as Bluetooth Low Energy) "in the coming months." That means future smartphones and tablets running the OS will be able to take advantage of the low power consumption in devices like the Fitbit Flex and Pebble smart watch. Current hardware also stands to benefit: the Nexus 4 was recently re-certified as Bluetooth 4.0-compatible, so these benefits could be enabled in a future software update.

Wait one more month, we are going to have not only child proximity band but also spouse proximity band. :slight_smile:

@Doc

I see you are talking about Pulse Width Modulation? PPM? I am going to be doing a project for college and we need to send in proposals by the end of the month or so. I have not yet covered PWM in my classes but I believe it really isn't that hard to master. But as this being said I am looking to do this maybe as a project, we have a full two semesters to work on it and find info if approved. I don't want to go over my head into something, but would like a cool idea to do. Would you think this is doable for a student?

@Sonnyyu

Bluetooth 4.0 seems interesting but looks like new technology. I don't want a project getting to expensive. Given I still can probably afford up to around $500 for this. I am just trying to figure out what would be the best method/easiest to be able to code. I am doing Computer Engineering, so I am more keen on Coding than on the actual electrical side of things.

As this being said I am definitely open to any other project ideas that you guys might have that you think could be good to do. I am also looking into doing a GPS tracking type deal. Have a GPS in a car, send a text to it, and find out where it is. Maybe that would be easier than child proximity band.

kpelkey151:
Bluetooth 4.0 seems interesting but looks like new technology. I don’t want a project getting to expensive. Given I still can probably afford up to around $500 for this. I am just trying to figure out what would be the best method/easiest to be able to code. I am doing Computer Engineering, so I am more keen on Coding than on the actual electrical side of things.

Smart Key Finder tags’s Price

  • <500 units = $18
  • 500-2000 = $14
  • 2000 = $12.5

  • software for iOS is free.

http://acesensor.com/wp-content/uploads/2013/01/AceSensorSmartTagBrochure.pdf

kpelkey151:
As this being said I am definitely open to any other project ideas that you guys might have that you think could be good to do. I am also looking into doing a GPS tracking type deal. Have a GPS in a car, send a text to it, and find out where it is. Maybe that would be easier than child proximity band.

It is child’s parent proximity band

Magnetic Case for iTrail GPS Logger

http://www.cheatersspyshop.com/itrail-gps-magnetic-case.html

The highly power efficient TI CC254x system-on-chip Bluetooth Low Energy digital leash solution.

You could always try one of those spring-loaded dog leashes....

I'm trying to something similar with the nRF24L01 trancievers, but in the opposite direction (let a game player know when they are near something). I'll try to remember to post here if I make any progress.

if your project is battery based, you might want to know this device;-

sonnyyu:
Your sensor node last 156 hours = 6.5 Days. nRF24L01+ is not design as Low-Power RF Transceiver.

Semtech SX1212 Ultra Low Power (3mA RX) RF Transceiver 310-510MHz

  • Tx current: 34mA
  • Continuous Rx current: 3mA
  • Sleep current: 1.5uA

if it is in 1 SEC Polling mode, 1 pc 3.6V/3.6A ER18505 size A lithium battery will last 10 years.

http://www.semtech.com/wireless-rf/rf-transceivers/sx1212/