Pir AS 312 with 2 rechargeable AAA battery. Boost needed?

[franz-unix]

And... the 3d printed case for the board V.1.0
Some adjustment in the tolerances and print settings are required, but the final results may not change so much.

The case for the board V.2.0 will be similar, only the position of the LED will change.

[SENIORA]

@nagelc

@rozpruwacz said in Pir AS 312 with 2 rechargeable AAA battery. Boost needed?:

@franz-unix said in Pir AS 312 with 2 rechargeable AAA battery. Boost needed?:

About the Li-ion battery, it seems to be a general agreement (see this topic for example) about the fact that the best option to power a node is with AA or AAA batteries. In fact one of the advantages is that you don't need to step up or down the voltage to power the radio and the MCU.

There is no one "best option". The power supply heavily depends on the project requirements. The PIR sensor requires noiseless voltage between 2.7 and 3.3v. This makes use of 2xAA problematic. In my opinion for such a project higher voltage supply with low quiescent current ldo is the best option. And it happens that li-ion battery with its voltage range and 3v ldo makes them perfect match. At least this is how I did it in my homE I went even further in my project and there is two ldos, one for pir and one for mcu + rf module as those two components creates large spikes in current flow as they work making supply voltage noisy.

PS. The other benefit of rechargable batteries is that they are rechargable :) so you don't need to remember to buy batteries when you go out of them.

you will handle the pir in your software but generally the pir needs to be powered all the time so no need for shutdown mode in your boost converter. The other thing is that pir doesn't linke noisy power supply, and dc converters are rather noisy especially in low current area. I would recommend t

[franz-unix]

@seniora the board supports multiple batteries and multiple radio modules.
When Vcc goes below 2.7V (BoostThreshold in the sketch) the booster is turned on and stay always on, while when Vcc is > 2.7 the booster is turned off and stay off. This is the case of a fully charged CR2032 battery or 2xAAA disposable (Alkaline) batteries.
With 2xAAA rechargeable batteries (NiMH) Vcc is max 2.4V so the booster is turned on by the MCU.

The ME2188 works well with RFM69 and 2xAAA rechargeable batteries (Vcc < 2.7V): no false positive in the PIR and good range for the radio transmission. See below that in the night with no motion the pir stay off (clear) even if the booster is active.

With the NRF24 radio module and a CR2032 battery I have some (not so frequent) false positive in the PIR, but the booster here is always off (VCC > 2.7V), so this may be caused by something else. Searching around, found this.
Probably is the 2.4 Ghz RF signal of the radio module that triggers some false positive in the PIR!
In fact I observe this false positive when the node wakes up by a timer interrupt and start sending data.

[rvendrame]

When you sleep the node with a PIR connected, a small 'nap' before the main sleep helps to settle the Vbat, and it usually avoid false triggering. Maybe this will help:

sleep(500);
sleep(INTERRUPT,RISING, SLEEP_TIME);

[franz-unix]

@rvendrame Thanks, I have tried your small "nap" trick and in fact something is happened... but in the opposite direction! The number of false positive is increased :joy:

But probably this is the way to solve the issue. Please note that, in order to stabilize the battery voltage, in the sketch I already have a cr2032_wait() function that sleep the MCU after each radio transmission, if the battery type is set to CR2032.

[franz-unix]

Hi guys, project finished! Now the led are under the Fresnel lens, so the design of the case is more clean (WAF +10 :sunglasses: ).

The final result:

With 2 x AAA batteries and the RFM69 radio module the node works very well and the total cost of the parts is about 10€.

If someone is interested, here a detailed build guide, with the links to all the parts of the project (3d model of the case, Kicad project, gerber files, BOM, firmware).

[huex]

few month ago ,i use tlv61220 step-up boost only for as312 is only 4ua， atmega328p ,battery cr2477 , then get 21ua ,
but now ,i give up boost , i test use ER14335 3.6v CR16340LIPO 【4.2V with diode 0.7V Step-down then 3.5V+- 】 ，same as312 get 18ua,:relaxed: ,ER14335 cost much but 1600mah ！ cr16340 750mah rechargeable best choose for me,,,,

[DenisJ]

@franz-unix
This is wonderful work... thanks for inspiring me :-)
I know that this is an old thread,
but can you give me a link of the AAA battery holder please ?

I just make a node sensor and I want to use it.
Thanks a lot
Denis

[franz-unix]

@DenisJ : Glad to know that this work has been useful for you in some way. :+1:

Regarding the AAA battery holder, the footprints on the PCB are for a Keystone 5204 (negative) and Keystone 5226 (positive) contacts.

I have purchased them on ebay; unfortunately the item that I have purchased is not more available, but this one appears to me like the same thing.

[DenisJ]

Thanks a lot Franz... I have buy this one... maybe is more little

Thanks again
Denis

[franz-unix]

@DenisJ the link is broken, so I have not seen the contacts that you have bought, but if they are just a little bit smaller and they can fit the hole on the pcb, they should be OK.

[DenisJ]

I don't know... the link it's work on my side.
Anyway here is the pic:

Yes, I think will be ok... I hope :-)

Thanks a lot
Denis

[Diego Serrano]

@franz-unix Hi, this post is very old I hope I can get an answer :)
I have ME2188 here but the behaviour of CE pin in extrange.
If I apply high to CE pin I get my correct 5v but if I change CE pin to low I get 4v on the output and I hope to get 0v.

Anyone can share your experience?

[Nca78]

@Diego-Serrano said in Pir AS 312 with 2 rechargeable AAA battery. Boost needed?:

@franz-unix Hi, this post is very old I hope I can get an answer :)
I have ME2188 here but the behaviour of CE pin in extrange.
If I apply high to CE pin I get my correct 5v but if I change CE pin to low I get 4v on the output and I hope to get 0v.

Hello, this is the normal behavior for this chip. CE will enable the step up, but with CE low it acts as a bridge so you get input voltage at output.
Pretty annoying :)

Anyone can share your experience?

My experience was to add an MT9700 power switch before the voltage input of the ME2188. The EN pin of the power switch is connected to the same signal than the CE pin of the MT2188, driven by the microcontroller.
It works fine like this driving a Plantower PM sensor not a PIR (don't pay too much attention at the caps at output I just wanted to have different footprints available).

[Diego Serrano]

@Nca78 said in Pir AS 312 with 2 rechargeable AAA battery. Boost needed?:

Pretty annoying

Thanks you very much.

[ali kaka]

One Last (boring 😂 ) question... Have you placed a flyback diode across the inductor? I'm not sure if this component is strictly necessary.