Atmega328p LoRa Low power use!

By pbecchi at 2018-03-15 • 0 collector • 454 pageviews

Hi I received few of these boards one week ago . Boards are good but documentation and examples are a little pour!

I am testing now the board in LowPower mode using LowPower.h and I am getting an 1mA minimum average consumption during sleep without the power led(2.5 mA with power led). I was expecting much less ( from 1 to 10 uA for the Atmega32 + about 250uA for the Sx1728) ! Is this due to any particular board component? There is any way to reduce that (other then taking the led away)? Can you send me password to access board schematic? Thanks

10 Replies | Last update 2018-09-28
2018-03-21   #1

Hi, Sorry never try the low power for this before, so no idea now, will test this and reply you later. 

The wiki login info is sent together with your order tracking info email, please check there.

2018-03-23   #2

Thanks, let me know, the board is ok for my project! I want to make a bulk order if I can reduce the power.... I can I get a quotation for 100 or 200 ?

2018-03-27   #3

Hi, we will need time to check the low power, not really good at this. We have a replacement IC instead of Atmega328, which should work fully same. but 1.2 usd cheaper. Totally each board could be 1.5-2 usd cheaper for bulk I think. 


2018-03-28   #4

Just a couple of suggestions for reducing power drain:

Power led drain about 1 mA ,it will be nice to have a way to disconnect it. Battery voltage is measured with a voltage divider with 2 10k resistors. This generate a continuous drain of about 0.2 mA . I suggest to use two resistor of 100k.

The new MCU will have same low power performances as the atmega328 ?

Thanks

2018-04-19   #5

we have just done some test today, result is here. 


http://www.electrodragon.com/w/Low_Power


On transmitter mode, should be 9.5mA regular standby, remove all extras, can reduce about 4 mA maxium.


if use a blank board without lora module, is about 6.1mA, could be lower down to 2mA if remove extras. 


The lora module should cased about 3mA when standby.


So regular 9.5mA -> remove all extras -4 to 5mA -> remove lora module -3 -> 2mA. More or less like this.

2018-04-19   #6

Ah, just posted a "me too" to access the schematic, when I spotted this thread.


(btw, my search for Loraduino only came up with one other thread which was not relevant)


Like the original poster (and many others), I have got good low power results with pro minis, with the "remove the led hack", but mostly by the use of the LowPower.h library, which is pretty awesome and taught me a lot about accessing directly the registers on the mega328p.


I mean the table they posted on the wiki is fine, but without including the use of the LowPower libary then I think it is a bit of a wasted exercise.


I actually started this reply because it dawned on me that, given that I too could (eventually) be ordering 100's of these things, it might be in Electrodragons interest to produce something which was low power to start with, the twinkly leds could be something that users get to add themselves. 


Its just a thought, but users like us mangling your carefully thought out boards on arrival just to remove components would seem on the face of it like an opportunity to reduce costs.


caveat : I'm not an electrical engineer, and realise any EE with a well stocked mind could probably shoot me down.

2018-04-20   #7

We will keep doing this test, with lowpower library too.  

Any suggesttions. or test need please let us know we will do. Any updates will update this thread and also on wiki.


2018-04-22   #8

If I compare correct, pro mini use regualtor MIC2505, which quiescent current is 5uA, but only 150mA delivery, the upgrade version MIC2519 is better 8uA/500mA. Our current use is AP2112 but 55uA quiescent and output up to 500mA. Which also add this to test later.

2018-09-16   #9

Reply to #8 @chao :

Hi Chao After long time I came back on this thread!

Your results (the ones of your table) are very interesting. It will be better to list the power reduction per each element removed. Like this:

Remove power led. About 3mA Remove analog input resistors. About 300uA Remove external flash. About 600uA

Since my measurement show about 1 mA drain with Lora receiving in CAD mode , I can reduce that to few( ≤100uA)!

This is a very good result : the board will run for 1 year on a 2000mAh Lipo.

The remaining question is how to modify the hardware to get to that!

Are you going to modify the board in future productions? It will be good to have soldered bridges that can be easily cut to reduce drain. Regarding resistors it will be sufficient to increase the values by a factor 20 to 50.You could also replace the LDO with a AP 7354 with a quiscent current of less than 1 uA.

Other question : with LGT 8f328 can we expect same drain of the atmega328?

Thanks

2018-09-28   #10

Hi,


What is CAD mode? What we can do on hardware to help on this? Please let mek now, thanks.


  1. power LED no problem, this is a demo board, we can just do not place the led during production. but can also add bridge, will add this.

  2. the VBAT monitoring resisitor is changed to 100K, which is always available on our tray of the pick and place machine.

  3. Currently use MIC5219, Iq current is 3uA according to datasheet.

  4. No hope on low power LGT8F328, it is a cheap clone, not that good on everything except price. 

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