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Power considerations for a Remote Sensor

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Total Posts: 4

Joined 2009-11-03

PM

Hi,

Having an idle remote ANT sensor and an idle hand terminal, what would be the most power efficient design way if I were to achieve that only the hand terminal needed a physical button activation in order to bring it out of idle mode and automatically establish a connection with the remote sensor?

Normally I would let the hand terminal act as a MASTER and the remote sensor as SLAVE, but this would require the remote sensor to constantly search for a valid ANT connection â?? I guess this would consume quite a lot of power since the SLAVE would have to be in search mode most of its lifetime.

Since I only require one dedicated PEER TO PEER channel (paired) I can think of an â??oppositeâ? solution where the remote sensor is programmed as MASTER â?? constantly broadcasting at a low rate. I guess this is not as power consuming as the search mode.

Then when the hand terminal (SLAVE) is powered on by the operator it would start searching for the remote sensor and eventually establish a connection. From there the channel rate could easily be manipulated if required.

I would like some sort of confirmation on this â??oppositeâ? design scheme â?? or if better solution exists â?? please let me know.

The main goal is that the remote sensor should not be physically activated and that the channel should only be open when the hand terminal is powered on.

Maybe this question is a bit trivial but I really hope to get some feedback on my thoughts â?? thanks in advance.

Best regards
BioLife      
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Total Posts: 524

Joined 2012-11-15

PM

If the remote sensor needs to change the message rate according to the commands from the hand terminal, the â??oppositeâ? solution does not make the difference from controlling the remote sensor search the â??PEER to PEERâ? channel periodically. Since to receive the message from hand terminal side, the remote sensor still need to open a receive channel and implement the search process.      
Rank

Total Posts: 4

Joined 2009-11-03

PM

OK I can see that I have to rephrase my question:

I have a Hand Terminal ANT AP2 - normally powered off â?? no active channel.
I have a Remote Sensor controlled by a low power uP + ANT AP2 - normally idle.
I need a standard bidirectional pre-configured PEER-TO-PEER communication channel.
I can manually power on the Hand Terminal â?? since it is in my hand grin
I cannot manually bring the remote sensor out of idle mode â?? I have to do this over the air

In order not to let the Remote Sensor use too much power being a constantly searching SLAVE I suggested (in my former post) that the Remote Sensor should act as MASTER and the Hand Terminal as a SLAVE.

This way the Remote Sensor (MASTER) can open a bidirectional channel and constantly broadcast packets that the Hand Terminal can detect after being powered on.

So â?? My question goes:
â??Does it make sense â?? power wise â?? to program a micro processor controlled ANT AP2 based unreachable Remote Sensor as MASTER instead of SLAVE?

Regards
BioLife      
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Total Posts: 524

Joined 2012-11-15

PM

There is no question to configure the remote sensor as a master.
The problem is the lantency in hand terminal side.

To sync with the remote sensor, the hand terminal have to spend time to search the sensor, the worse case acquisition time for common transmission message periods is shown below:

Transmission Worst case search time
10 Hz 2 seconds
4 Hz 3 seconds
2 Hz 7 seconds
1 Hz 15 seconds
0.5 Hz 45 seconds

these number also assume zero packet loss and a favorable RF environment.

To reduce the power consumption, the optimized message period have to be considered. This depends on the application.