LoRa Gateway overall Power Consumption

I note that with each generation the RPi’s are burning more power and will often be main ‘consumer’…new RPi 3B+ is perhaps ~2x over old Pi2 or PiZero/W. For some new builds I have bought 3/3B+ where power less of an issue but have also just bought a bunch of Pi2B’s for more sensitive apps and where tight packing means internal heat a potential issue longer term…just my 2penneth :wink:

BTW think I saw a recent post on the forum comparing pkt fwdr performance with quad core/multi thread RP3B with single thread on Pi Zero but quick search didn’t turn up to post here - may be worth you digging…

Also inline with last night’s posting wrt Laird RG191/186’s I’ve found that if I run the Laird off lower voltage then current consumption is generally lower c/w my RPi based platforms which may help your overall use…

I replaced the RPi 3B+ of my ‘lab’ setup by a Zero, and the processor is not used a lot.

I haven’t measured the power consumption, but another factor is heat dissipation. 3B (and 3B+) needs to dissipate all this power – no secrets – and it can be problematic in an enclosure…

Only downside of the Zero is that you either need to go wireless or add an USB network adapter…

Note that there are 2 versions of the RPi 2, the first batch has an ARM V7 processor while the last one has the same V8 chipset as the RPi 3 and is more power hungry…

Power Consumption Benchmarks RPI’s

I understand the later Pi 2’s using newer chip also then have potential SPI timing issue flagged (with work around) elsewhere on Forum.

Here is graph from Iss 68 (April) MagPi Mag showing relative power draw of the generations…think this reflects earlier RPi 2’s

image

PiZero WiFi only is also a pain when trying to use external IP rated box (typically metal such as the E-Zy housings and others), hence my choice of 2B’s

Yes, I would think about making a 3D printed “skeleton” to hold the Zero and the concentrator, that could be fixed in an IPxx box. But I am not in favor of Wireless for “production” use, so I do agree 2B first gen is a better choice.
Do you have a reliable source for 2Bs? I am currently swapping devices at home and trading with friends who are usually happy to get an upgrade :wink:

“Do you have a reliable source for 2Bs?” sadly not guaranteed to be old ones

“currently swapping devices at home and trading with friends”…good tactic! Pity I had a bunch of Gen 1’s before getting into this and sadly few Gen2’s so have to rely on what the postman brings… :slight_smile:

Thanks very much all for your input. We recently published an article based on the consumption of several lora vendors, if it might be of your interests! I am sharing the link below:

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They must be using a Linear regulator. I’ve just ordered a Laird RG191 and will have a bit of a play.

No, 5.5 watts (132 W/h consumed over a 24 hour period).

The Pi 3 B+ is what the stores here in NZ are now selling, and to be honest, I’ve never considered using the Pi zero for any of my various projects.

Most of my sites already have a RaspberryPi based ADSB receiver - This is a CPU intensive process while the LoRa gateway seems to need minimal resources. Maybe the best option for me is to upgrade the Raspberry Pi and do both ADSB and LoRa gateway from the same RPi.

Uhmm… I think you’re making a bit of a mess with the units of measurement

Alex

How? What’s wrong with watts and watt hours?

If your application consume 132W/h it means that it needed 3168W in a day :scream:.

I think you mean that it consume 5.5W/h that is 132W in a day.

Alex

Its 5.5W and 132Wh per day (thats Watts x hours, not Watts / hours)

My input on this is that the SX1301 concentrator is the main power hog. I say that because the MPU is a variable that can be scaled by processing load, clock speed and silicon process, but the SX1301 is on all the time in receiving mode.

Microchip LGx271 module datasheet (as used in TTN gateway) puts it at about 3W and this feels about right. It certainly runs hot.

So where you’ve seen 40W total, maybe that was a 64ch gateway, with 8x SX1301’s ???

A standard 8ch gateway should be around 5W constant.

Assuming solar power would need ~24hrs autonomy, that would need a pretty large lithium cell, like automotive sized, or a standard lead-acid battery

Right, I see the issue. As @JDP posted, I incorrectly used W/h (Watts per hour) instead of Wh. But your understanding of power units is also incorrect.

Watts are the used to measure a rate/speed of consumption (1 joule per second).
Watt hours, Kilowatt hours, etc are a volume/measurement of use over time.

White W/h could be used to measure a rate of change in wattage over time, it’s probably not a very common unit to use.

I’ve done some tests on the RG191 and found that this is not the case.

Voltage (v) Current (A) Power (W)
13 0.175 2.275
12 0.19 2.28
11 0.205 2.255
10 0.225 2.25
9 0.25 2.25
8 0.28 2.24
7 0.32 2.24
6 0.375 2.25

From my tests, it draws ~2.25 Watts regardless of input voltage

I took my RG191 apart. It uses a TI TPS54525 switching buck regulator which supports up to 18V input. The output is set to ~4.55 volts.

Based on this, the RG191 will run on an input voltage range of 5-18 volts. In other words, it will happily run directly off an AGM battery and the fully charged voltage of almost 15V.

Hi @jbkiwi your right in that the TI part may support up to 18V but there is on board limit also (I believe thermal fuse rated to 15V max) so do not exceed 15V - see here per our earlier exchange in LG191 AU thread

Note also I have found that operation at lower supply limit leaves system prone to issues where (most likely due to brown-out protection mechanisms per exchange with Laird team) when supply applied if voltage ramp isnt fast enough board may not kick in properly - I found feeding supply ‘quickly’ via e.g. a switched relay feed once stable gives fast enough Vin ramp to avoid problems. At slightly higher Vin it doesn’t seem to be a problem. I need to experiment with a couple of systems to find the ‘safe’ operating area/ramp.

Thanks for the heads up. You are correct, it’s a 3A 15V Polyfuse. It’s a large 2920 surface mount device (LittleFuse 2920L300/15) so if you really need that extra 3 volt range you could swap it out, or replace it with a glass fuse.