RFM69W or RFM69HW?

[drsprite]

I'm having a hard time deciding which transceiver to go with. My plan is to have the Moteino setup in my concrete-poured walled basement. It doesn't have to go there, but down there is where I have a rack that contains the rest of my IT equipment.

I'm planning on having the Moteino control the 2 garage doors that are very close to the location in the basement. I'm also thinking about other items to have it run, such as a home brew weather station, some water sensors, SwitchMote in future, etc.

While the RFM69W has a 300m range, I'm concerned about the concrete walls becoming an issue. Will the RFM69HW help with the concrete issue? If not, then I think my answer is right there.

Or, is it "better" to purchase the RFM69HW and use setHighPower() on everything?

Just trying to future proof, and with the added cost, I just want to make sure I'm buying the right thing.

Thanks

[TomWS]

I'm having a hard time deciding which transceiver to go with. My plan is to have the Moteino setup in my concrete-poured walled basement. It doesn't have to go there, but down there is where I have a rack that contains the rest of my IT equipment.

I'm planning on having the Moteino control the 2 garage doors that are very close to the location in the basement. I'm also thinking about other items to have it run, such as a home brew weather station, some water sensors, SwitchMote in future, etc.

While the RFM69W has a 300m range, I'm concerned about the concrete walls becoming an issue. Will the RFM69HW help with the concrete issue? If not, then I think my answer is right there.

Or, is it "better" to purchase the RFM69HW and use setHighPower() on everything?

Just trying to future proof, and with the added cost, I just want to make sure I'm buying the right thing.

Thanks

IMO, if the Mote is AC powered, why wouldn't you use the HW???  The W is valuable in cases where you are critically concerned about battery consumption, but, even here, with proper design (and the right conditions - like you don't have to report every second) the radio power is almost incidental to the overall power budget.

Tom

[drsprite]

Thanks Tom. I had that same idea - but confirmation is always welcomed. So the HW and the W can talk to each other - even if HW is setHighPower()?

So I could setup my base station with an HW, then the field sensors can be W or HW depending on distance?

[TomWS]

Thanks Tom. I had that same idea - but confirmation is always welcomed. So the HW and the W can talk to each other - even if HW is setHighPower()?

So I could setup my base station with an HW, then the field sensors can be W or HW depending on distance?

Distance and battery budget would be my view. 

Just to give you some perspective, when your battery operated mote sends data to the gateway, the total time for the transaction, including the Ack back (unless your Gateway is busy), is over in less than 8mS.  That means you might be able to sleep after 11mS + time to sample whatever it is you're reporting.  Factor that against your time between sample/reports (I typically use 10 minutes if I'm measuring environmental conditions) so, using these numbers, your duty cycle (powered up/sleeping) can be as low as 0.0018%.  In which only 3.5 mS of that is the mote Transmitting (ie full power), the rest of the time could be powered down to single digit uA.

Here is a snap of the current drawn during a 10 byte transmission using an HW.  The vertical scale on the blue line is mV across a 1ohm resistor (1mA/-mV).  This was taken with a single PA turned on and powerLevel set to 15 (about 84mA peak transmit current).  There is some current spike as the radio comes out of sleep, then the current pulse for transmit, the step down to receive mode (about 35mA), the ACK occurred at the little spike at the end of that porch, then a bit of time for the processor to process the exchange, then back to sleep.


The bottom red trace was just the trigger signal and not relevant.

Tom

[drsprite]

This information is great and will one day be useful for me. But right now it's a little over my head as I learn more and more about this stuff

In laymans terms, it sounds like the W and HW can "talk" to each other. If I require low power, I want to use the W to save on battery power. If I have AC power, then I should go with the HW.

So for my GarageMotes, I could use HW because I have AC power. For a weather station running off batteries in the backyard, go with the W so that the battery isn't depleted too quickly for no good reason.

All of which can report back to a basestation with an HW.

I think that sums it up?

[Felix]

The W/HW is only referring to transmission power.

Think of W as a megaphone that can be heard up to 130m away.
Think of HW as a mehaphone that can be heard up to 200m away.

In terms of receiving they all have the same "ear", same sensitivity. It's up to you to decide if you need the extra power of the HW transmitter. Each environment and application is different.

[drsprite]

Thanks Felix and Tom! Both very helpful! I'm bookmarking this post for sure so I can reference the technical bits a little later on down the road!