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I am unsure about voltage interoperability between an Ultra and some components I hope to use with it. I want to create a device which can use a PIR Motion sensor and transmit motion detection using an XBee Series 1 Wireless module. The XBee operates on 3.3V Supply Voltage and I believe the PIR can handle between 3-5V input. Would the VBUS pin from the Ultra be usable to supply voltage to PIR/XBee? Are the IO requirements compatible?
I really appreciate any help. I’m also open to other ideas on a better way to do what I’m doing. I want my device to run on a battery for months and simply check for motion and broadcast wirelessly to a paired device which listens for broadcast and simply turns on a LED when motioned is detected on the other device.
Here’s some documentation for the PIR:
https://cdn-learn.adafruit.com/downloads/pdf/pir-passive-infrared-proximity-motion-sensor.pdfHere’s some for the XBee:
https://www.digi.com/resources/documentation/digidocs/pdfs/90000982.pdfHi,
An XBee user here back in 2006! You can use the 3.3V to power the XBee itself. The Pro version of the XBee is 215 mA but could still work with the on-board 3.3V regulator as the transmission is quite fast. If current is inadequate, add an external 3.3V regulator by tapping from the VBUS power.The XBee is basically a 3.3V device so you could connect them directly with the Mini Ultra Pro. Use either Serial or Serial1 to connect the UART up.
The PIR sensor should trigger when there’s a motion only, so you could use an interrupt to wake the MCU up and then MCU will wake the XBee for transmission. There are many PIR sensor out there but some could go down to 6 uA. If the XBee is properly put down to sleep and coupled with a low power PIR sensor and suitable battery capacity, you could run for more than 1 year.
Thanks so much for your reply! What do you think about the power consumption of the other device that needs to wait and listen to turn on the LED when its partner device detects motion? It looks the XBee on that end would need to be in Idle/Receive mode which uses 50mA. I was looking at the sleep options on the XBee and it seems like I could sleep it on a schedule and check for signals during waking periods, but that seems a little more complicated since I might have to rebroadcast messages or something on the TX side to take that into account.
I’m also curious if you any suggestions to optimize my design. The range I need for this is very short such as 2 feet. Would another type of wireless comms be better or is their another low power microcontroller/wireless combo that might work better here? I am trying to keep things as simple as possible since this isn’t my expertise and my experience since college is pretty much limited to the arduino. Willing to learn new things though.
Thanks again very much your reply, it is really very helpful to have someone to talk to this about!
I doubt that you can run away from putting the receiver in receiving mode all the time to receive the packet.
As the event is non-deterministic, and even if the time synchronized (I believe the Series 1 has this firmware capability) is used, it is very hard for you to get the message across successfully let alone at single try.Why do you need wireless when there’s only 2 feet? It is because one is external of the building? And another is inside?
The PIR sensor can also work on it’s own without any external MCU and can show lit up an LED when there’s a motion. You probably just need to wire the LED for 2 feet if that is where you want it to be.
One sensor is on one side of a door and the other on the opposite side. Having a wire go over the door seems like it would not only look sloppy but get pinched and damaged.
If I need to leave the XBee in Idle/Receive it seems like that would eat up the battery pretty quick. I’d like the solution to last one a battery for months.
I was thinking the XBee might be overkill and maybe some kind of a wireless switch or relay would be good enough like a Reed Switch/Relay, but I think that be too hard to align the sensors and/or generate enough magnetic field through the door. I’m trying to search around for something else that might work. Let me know if you have any ideas.
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