Low Power Wireless Transmitter For battery Operated Motion Sensing Applciation

[brightnight]

I'm looking for a low energy communication method for a wireless PIR motion sensing device. The system will be battery powered so RX current draw is particularly important and must be as low as possible. The Tx part of the system only be powered on during motion alert events, while the Rx part is always awake and listening. The Tx frequency doesn't matter, the range will be ~20ft outdoors, I would like to be below 5mA for Rx current if possible. I will ideally want a number of channel options or a method from distinguishing certain Rx modules so that I can take different actions depending on which Tx is communicating.

I won't be transmitting data so to speak, but more of an interrupt alert that motion was sensed so even an FM transmitter could work. I was looking at the NRF52810-QFAA-R  for it's 4.8mA receiving current and the less ideal for power consumption RF8001 (11mA Rx) but don't know what range I can expect or if there's something out there that might be a better option. The systems will also be enclosed in a waterproof box outdoors but subject to a large range of temperatures. Thanks for your time.

[haakonsh]

The system will be battery powered so RX current draw is particularly important and must be as low as possible. The Tx part of the system only be powered on during motion alert events, while the Rx part is always awake and listening.

What's the power budget for the TX device? 
A regular BLE connection can easily go down to 20µA on these kinds of use-cases.

I will ideally want a number of channel options or a method from distinguishing certain Rx modules so that I can take different actions depending on which Tx is communicating.

 How many devices do you need to support in your network?

 

I was looking at the NRF52810-QFAA-R  for it's 4.8mA receiving current and the less ideal for power consumption RF8001 (11mA Rx) but don't know what range I can expect or if there's something out there that might be a better option.

 There's not really any contest here you, should not consider the nRF8001 as the nRF52810 has so much better range. You can get 500m line-of-sight range at +4dbm with the nRF52 series for these kinds of control-applications. 
The best part is that you can trade-off that range for a reduced TX power, thereby reducing the power consumption of the transmitter. I'd say you can use -10 to -20dBm as the output power. That would reduce the current consumption from 3.6mA at 0dBm, to ~3.1mA at -10dBm, or ~2.5mA at -20dBm. 

[brightnight]

I appreciate the time you spent on your response; it was extremely informative and helpful for me.

haakonsh said:

What's the power budget for the TX device? 

Do I need to keep an active BLE connection between the Rx and Tx at all times or can I power the Tx off until I want to send a wireless signal for motion? I haven’t made a Tx power budget yet but it would be on so infrequently and it would be powered off 99% of the time that I’m guessing it would really matter. On an average day I might use the Tx for an instant 2-4 times to alert a micro controller that motion was sensed, so the only info I need from the Tx is to alert the micro controller that motion was sensed (no real data being transmitted, just an alert).

haakonsh said:

 How many devices do you need to support in your network?

I will be building a wireless motion alert system and will want many groups of sensors in the same area. Each Rx will probably have 2-4 Tx’s that will communicated with it. I would need ~10Rx units each on their own channel and each Rx would have 2-4 Tx modules associated with it. Ideally I’d like to use more channels in the future if needed and I assume there is no maximum number of Tx’s that I pair with an Rx.

Thanks, I’ll take a look at the nRF52810. I don’t need long range, just 50ft max range outdoors and line of sight. Given the additional info I provided about number of unique channels required, standby Rx current, and range, do you still suggest the nRF52810? Thanks for your time.

The system will look something like this but instead of three Rx modules each on their own unique channel there will be ~10:

[haakonsh]

brightnight said:

On an average day I might use the Tx for an instant 2-4 times to alert a micro controller that motion was sensed, so the only info I need from the Tx is to alert the micro controller that motion was sensed (no real data being transmitted, just an alert).

 Then a BLE connection does not really make any sense. I suggest you use either the ESB protocol, see; Enhanced ShockBurst User Guide, Enhanced ShockBurst API docs, and the ESB Low Power Transmitter/Receiver Example,

or the Radio Transmitter Example and Radio Receiver Example. 

The ESB protocol has some neat features like ACK'ing and automatic re-transmissions, channels selection, etc, but it only supports 8 transmitters per receiver, unless you do some hacks to it. 

Each radio has a unique on-air address that you can use to determine what transmitter sent the received packet.