💬 MyMasterSensor

[openhardware.io]

https://www.openhardware.io/view/582/MyMasterSensor

[Soloam]

This post is deleted!

[Soloam]

This is my project to a all in one sensor, it contains interface to:

• LM393 Light Level
• Door Sensor
• HC-SR501 Motion Sensor
• DHT22 - Temperature and Humidity Sensor
• Switch
• Controlled by a Atmega328p-au and NRF24L01 SMD

Powered By 3 AA batteries, split in 3v and 4.5v, or if you prefere only 2 AA (3v). You can set the power jumper to safeguard the RF Radio. This interface is the best way to control a PIR sensor and ensure that the power feed to the PIR is inside acceptable range. (please see https://forum.mysensors.org/topic/6511/hc-sr501-3-3v-randomly-sends-tripped-when-radio-is-on/ ), see images to more information.

Work still in process... comments and recommendations are welcome.

[Soloam]

Gerber files uploaded, please note that this PCB is still to be tested, work in progress.

This PCB was inspired one a post made by @Yveaux and @mfalkvidd on https://forum.mysensors.org/topic/6511/hc-sr501-3-3v-randomly-sends-tripped-when-radio-is-on/

The idea is to remove the voltage regulator from the PIR sensor and power it from 3 AA batteries.

My main doubt on all this, some test is needed is the rest of the system. At the moment I have all the system powerd by 3 AA batteries (4.5v), it icludes all the sensors and the atmega. And only the radio is powered by the 3V. I don't know if it would be better to use other power configuration, like only the PIR with 4.5, and all the other sensors and atmega with 3v.

I did this because in the datasheet of all the other sensors it states that it works at 3.3v and with 2AA batteries I get 3V, and with power drain it would be way bellow that.

What do you guys think it would be better? To keep it this way, or change it for example radio and atmega 3V and all the rest 4.5?

Please note that this only applies if you supply 2 voltages to the system, if not you can just put the jumper into position number 2 and feed all the system with the same voltage, that should be Radio safe.

Thank You all

[Nca78]

@soloam said in MyMasterSensor:

What do you guys think it would be better? To keep it this way, or change it for example radio and atmega 3V and all the rest 4.5?

Power all that you can at a lower voltage. The lower the voltage, the lower the current.

[Soloam]

@nca78 thank you, but will sensors like LM393 Light Sensor and DHT22 Module work with no problems bellow 3V? They are both rated between 3.3V and 5V.

Thank you

[sundberg84]

@soloam said in MyMasterSensor:

LM393

No not the light Sensor/DHT22 Module without some changes in them.

[Soloam]

@sundberg84 thank you

So basically to keep this modules, the only thing that I would have powered by the 3V is the radio and the atmega. I planned building the PCB without using the modules, but I have a lot of them laying around and I think that it would make the PCB more useful/easy to others that plan to use it.

[sundberg84]

@soloam - The radio can go down to 1.9V (not clones) and the Atmega depends on if you want to change the fuse settings. Normal BOD is set a 2.8v but with internal oscillator you can go lower.

Its Easy to use modules only, but as you understand there are limitation. Its possble to power a 3.3v module from a Atmega328 pin if you power it @ 3.3v (D3 for example) if they do not need more than 40mA (MAX!). Then you can turn on and off the pin and save power. I have even made a testnode with a dc-dc step up which i sourced from D3 and could turn on/off to get 3.3v but its not pretty.

[Soloam]

@sundberg84 the idea is to sleep the node whenever possible, and when it wakes up (for example from triggering the PIR) it uses the wakeup to notify all the other nodes and go back to sleep again.

What you are telling is to use 2 Digital pins to one module? One to power it and other for the data? Is that it? I also thought about doing something like that, I would need to feed the atmega with 3AA (4.5v).

[sundberg84]

@soloam - whatever you feed into the Atmega will feed the modules then so you need a stable 3.3v or a regulator/step-up. for the modules.

Its not an easy task this. In my design I have "solved" this by using a DC-DC step up for everything except the Radio. Then I know everything uses 3.3v atleast. I then remove led and voltage regulator and during sleep Im around 50uA which is good enough for me.

The problem is the booster can introduce noice into the node and disturb the sensitive radio.

[Nca78]

@soloam said in MyMasterSensor:

@nca78 thank you, but will sensors like LM393 Light Sensor and DHT22 Module work with no problems bellow 3V? They are both rated between 3.3V and 5V.

Thank you

The question is why do you want to use those ?
A small breakout board with si7021 is better than DHT22 in every way.
And for light there are also a few i2c sensors that are way better.

[sundberg84]

@nca78 - he had alof the them laying around... and its easy to use.

[Soloam]

Thank you @Nca78 @sundberg84 I think that I will redo my board to use a Temperature Sensor SI7021 and for light a foto resistance like the GM5539 (any opinion or alternatives?).

Better do it right, and I can use the sensors that I have around in tests or something.

One question, I'll use this inside a case, ok I can do holes, but will not this change the temperature and humidity readings?

[Nca78]

@soloam no it should not affect the readings too much if you make holes near the sensor and you have a bit of space in front of it so that the air can flow.

For light sensor check BH1750 or MAX44009

[bladeback]

Please send me kicad files, the ones that can be downloaded, can't be opened in kicad 5, or upgrade here. Thank you