Can nRf51822 be activated by vibrations?

asked 2017-02-16 23:39:27 +0100

My question is can the beacon be activated by someone shaking it and receive a notification via Bluetooth? If so what is the range it would have? If not can an additional sensor be added to achieve this effect? Understanding that additional equipment maybe be needed. Student in classroom setting for project.

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RichieJH gravatar image

answered 2017-02-17 11:21:01 +0100

Yes, easily done, we've done something similar. Couple your nRF with an accelerometer such as an MPU6500 (about $5) through TWI. Use Port mode for low power interrupt and it consumes only micro amps. Range could be up to 100 meters depending on antenna layout/tuning. There is sample code put out by the Nordic guys that can get you up and running with the MPU6500 pretty quick.

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rogerclark gravatar image

answered 2017-02-17 01:31:27 +0100

The nRF51822 does not have any built in vibration sensing as far as I'm aware

You would need to attach an external vibration sensor of some kind.

You can buy simple vibration sensors, which are basically a push button switch which gets pressed when there is vibration, however my experience with these sorts of sensors, is that they are not good at detecting a shake and they seem to be designed to detect a sharp movement, e.g. you knock or tap the them. However you may be able to find a mechanical sensor which does trigger when you shake it.

Alternatively, you need to use an accelerometer chip of some kind e.g. LIS2DH

Or accelerometer + gyro (LIS3DH) etc

But its far harder to use these devices as they have to be configured via TWI or SPI and interfacing to their interrupt signals can be problematic because the GPIOTE system on the nRF51 takes a lot of power in fast mode, which may be required to detect the interrupt from such devices

So if you simply want to detect a shake, I suspect your best option is to find a suitable mechanical sensor which will trigger with the sort of shake you anticipated

(Someone may be able to suggest a suitable mechanical sensor)

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This is mechanical solution example but personally I prefer LIS2DH

Alex ( 2017-02-17 11:42:48 +0100 )editconvert to answer

+1 I'm using a LIS2DH in one of my designs

Roger Clark ( 2017-02-17 13:04:07 +0100 )editconvert to answer

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Asked: 2017-02-16 23:39:27 +0100

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Last updated: feb. 17 '17