Multisensor PIR based on IKEA Molgan

[ricmail85]

Ok thanks for your reply. I'll check the board for some weak connection and try again...
bye!

[Yveaux]

@ricmail85 I also have one Molgan that I just can't get to work correctly. Put it aside, thinking it was an incident, but if more people have issues, this might be a structural thing...

[ricmail85]

@Yveaux said in Multisensor PIR based on IKEA Molgan:

@ricmail85 I also have one Molgan that I just can't get to work correctly. Put it aside, thinking it was an incident, but if more people have issues, this might be a structural thing...

I'll give it a try. I have to check that the wires I soldered on the back of the breadboard are just fine...
I'll let you know.

bye!

[dynamite]

@ricmail85 @Yveaux basically mine was shortcut by testing Some connection which I should not have Done....🙄

[ricmail85]

@dynamite @Yveaux Ok I've done some testing. Here my results.

I checked the wire connections between the Arduino and the PIR and they were ok. Actually when powering everything with batteries I always get HIGH from PIR.

Then I tried to leave only the PIR without the Arduino and its radio (disconnected the GND wire) and the PIR (alone) was working! I checked with multimeter it oscillates between 0V and 3V if a movement was detected.

So I concluded that the failure was due to the Arduino. If arduino+radio are powered (by the same battery source) i get always HIGH.

Looking at this post https://forum.mysensors.org/topic/5273/ikea-molgan-hack/36 I found similar problems due to ripples. I added a capacitor (100uF) in parallel to the PIR capacitor and a 10uF capacitor between the + and - of the battery pack.

By doing so I still cannot move from HIGH signal from PIR when everything was connected. So I've done more debugging and I found that everything works like a charm if I put a sleep (1000 ms) after sending a message (in my sketch I send 4 different message types when the Molgan wake up).

Maybe there is still some disturb arising from the radio (sending a message require some power at least)? Now my project is working, actually with the sleep(1000) trick after each send.

I don't know if the capacitors were effectively needed at this point...

Hope this can help!
bye!

[LastSamurai]

I am the one from your post and the capacitors only helped a little. One of my molgans simply doesn't seem to work.
But you are right sending takes a lot of energy (vs doing nothing) so a bigger capacitor and/or pauses in between definitely should help!

[ricmail85]

@LastSamurai
Some more debugging and I see the problems arise when I do analogread, so does not seem related to the radio itself.

If I send a message about a dht sensor (digitalread) it is ok. If I send a message of battery/light measure (analogread), the pir gets high...

[Yveaux]

@ricmail85 does the behavior change when you swap the order of the messages sent? Eg first send the battery value.

[ricmail85]

@Yveaux yes, it seems to work better by sending before the messages performing analogread and then the one using digitalread...

[Yveaux]

@ricmail85 could be power related then. Try adding some sleep or wait statements inbetween each message sent.

[ricmail85]

@Yveaux Yes I found a partial fix by adding sleep of 1000 ms after each send. And by doing analogread before digitalread. It seems related to power fluctuations. I ve already added some capacitors to the Pir. Shoul I add akso in parallel to the R2 resistance when reading the battery and light level?

Bye!

[Yveaux]

@ricmail85 I still think it's strange that you need the delays for a battery powered sensor. Normally the batteries can supply sufficient power to compensate for the bursts required when sending.
I don't want to read back the whole thread now, but what was your setup again?

[ricmail85]

@Yveaux This is my configuration

1. Arduino Pro Mini 3.3V
2. RFM69 radio 433MHz
3. Photo-resistor
4. DHT11 temp sensor
5. Battery voltage measurement through voltage partition.
6. The arduino and radio are powered by a 3.3V MCP1700-3302E voltage regulator

yesterday I've noticed the following. If I shutdown the gateway, the sensors fail to reach it and the PIR goes HIGH forever. By rebooting the gateway there is no chance to get it LOW. I have to remove the batteries and everything starts to work again.

[Yveaux]

@ricmail85 said in Multisensor PIR based on IKEA Molgan:

The arduino and radio are powered by a 3.3V MCP1700-3302E voltage regulator

I suspect the regulator injects noise in your supply and/or isn't able to supply enough power for a series of transmissions.
You could try powering directly from 2xAA battery, without using a regulator.
Both the ATmega and radio will work directly on 2xAA.
The DHT11 won't (IIRR) but there are many way better alternatives for it that work at less than 5V supply (e.g. Si7021, BME280, SHT11 etc.).
The PIR needs > 3.3V; refer to this post on how to power only the PIR from 3xAA.

If you don't need a lot of accuracy on the battery measurement (who does...) then you could consider using the Vcc library I wrote a while ago.

[ricmail85]

@Yveaux Thanks for your reply. I've done a lot of debugging today. And I guess I found the issue.
It's definitely related to the radio power consumption as you suggested.

I'm currently using the new RFM69 driver, with ATC enabled by default. As long as the power level stays below -4 dB, everything works fine. If the gateway is powered off, the radio power level automatically increases to 100% and the PIR behaves weird. It's always HIGH.

By rebooting the gateway, the node relink itself and gradually lowers its power. As before, when it goes below -4dB the PIR starts to work again.

Since it's a battery powered device I decided to set

#define MY_RFM69_MAX_POWER_LEVEL_DBM (-4)

at the beginning of the sketch file. Even if the gateway fails (shutdown) the PIR does not get HIGH anymore. All the measurements work fine now by limiting the max power to the radio.

By doing so all the sleeps of 1000ms after each send are not needed anymore.