Wireless baby monitor using Arduinos?

Hi,

I wanted to ask you if it is possible to use two Arduinos as wireless baby monitor?

What I mean: - using microphone on one Arduino and receiver on the other - using transmitter on one Arduino and receiver on the other (one-way is good enough)

I have to make a choice now - either buy normal monitor for ~100$ or make one myself. I think I can do it cheaper and after baby got older I could scavenge it for another use.

Questions: Is Arduino (Duemilanove, Mega, which one?) capable of transmitting sound on-the-fly? There shouldn't be problem with making some kind of regulation of sensitivity when Arduino starts transmitting... Can this be done with cheap electronics (like 433MHz TX/RX modules for 2$ each) or do I have to use some kind of xxBee shield? I prefer less in/out pins used (everybody does, I suppose). What would you recommend to me? I will probably use Arduinos for wireless meteo station afterwards or some kind of RC control (lights, garage door, ...), bear this in mind when you answer this question, please.

Thank you for your time and for any answers on this subject.

Is Arduino (Duemilanove, Mega, which one?) capable of transmitting sound on-the-fly?

Depends on whether you want to recognize the sound, or not. If all you want is to send a "there is some noise being detected" signal, then, yes an Arduino will work.

If you want to send the sound data, in full stereo, then, no the Arduino will not work.

Consider this. By the time you've bought two Arduinos, two XBees, shields, a microphone, some speakers, and other odds and ends, you are well over the cost of a pre-made unit, and you still have a lot of work to do.

Can this be done with cheap electronics (like 433MHz TX/RX modules for 2$ each)

The adage "You get what you pay for" is true.

PaulS: Consider this. By the time you've bought two Arduinos, two XBees, shields, a microphone, some speakers, and other odds and ends, you are well over the cost of a pre-made unit, and you still have a lot of work to do.

Also consider that by the time you've got all this working, Junior could be at college.

And who will be blamed if you build it and it doesn't work and something awful happens?

A pair of RaspberryPIs might be a better option - but still a lot of work.

...R

Thank you for really fast answers.

I expect something like: mono, telephone quality (I'm speaing about standard wired telephone) -> that means what noise does the baby do (cries/babbles). I suppose it could run at some pretty low bitrate.

Two concers are: 1. Is Arduino powerful enough (it will do nothing more than detect sound and then transmit realtime). Which Arduino can do that? (I have Duemilanove, this can cut cost a little for me - if it can do it). 2. What kind of shield/hardware do I need? What kind of frequency should I go for? We are talking about ~50-100 meters in open, 20 in the building. This requirement varies depending on the final price.

I'm willing to pay the same amount as for pre-made unit. I will buy china-made Arduino-like boards. The wireless hardware... well, what you advise me. If we are speaking about 433MHz, then 2$ each, if we are speaking about XBee, there is higher price for that...

I will use some scavenged microphone and speaker (if this can be done with Arduino).

AWOL: And yes - junior can be at college by the time I'm done with this :-) Maybe junior will do it faster :-)

Robin2: It either works or I won't use it. If it stops working suddenly... this can happen with pre-made unit, too. Considerin taht I will buy premade unit of lowest price (I will not use it in the future), I would be afraid of it more than of my creation. I have considered RPis for a moment too, but I will like some general electronics solution more (I can scavenge it and use it for other projects).

  1. Is Arduino powerful enough (it will do nothing more than detect sound and then transmit realtime).

It can detect input on an analog pin at some (relatively slow) rate. It can send the value read to another device at some rate.

You will need to experiment to determine if the rates result in acceptable data transfer rates. Keep in mind that detecting a baby crying is not just a matter of reading some voltage on a pin. Also, keep in mind that converting that voltage back to audio is not a trivial process.

If we are speaking about 433MHz, then 2$ each, if we are speaking about XBee, there is higher price for that...

The question is how much data do you need to get across reliably? And, how much work are you willing to do to ensure that that happens? XBees do all the work for you. Cheap radios mean that you do all the work of determining that a packet got there, in the correct order, unmangled, or you send the packet again. Not terribly hard, if you have plenty of memory and time. Oh, wait, both of them are going to be in short supply.

PaulS:

  1. Is Arduino powerful enough (it will do nothing more than detect sound and then transmit realtime).

It can detect input on an analog pin at some (relatively slow) rate. It can send the value read to another device at some rate.

You will need to experiment to determine if the rates result in acceptable data transfer rates. Keep in mind that detecting a baby crying is not just a matter of reading some voltage on a pin. Also, keep in mind that converting that voltage back to audio is not a trivial process.

About the rates - XBee looks fast enough for relatively good sound quality (if Arduino can keep up with it; send the data fast enough).

About detecting baby crying, I thought about it in the easy way: Is there a noise loud enough (not considering what the noise is)? Start sending and do so until it goes back to (lower than) "threshold" value. I don't need to detect the type of noise, I thought about volume only.

PaulS:

If we are speaking about 433MHz, then 2$ each, if we are speaking about XBee, there is higher price for that...

The question is how much data do you need to get across reliably? And, how much work are you willing to do to ensure that that happens? XBees do all the work for you. Cheap radios mean that you do all the work of determining that a packet got there, in the correct order, unmangled, or you send the packet again. Not terribly hard, if you have plenty of memory and time. Oh, wait, both of them are going to be in short supply.

After some thinking, I cut off the idea of using cheap RF hardware. If I go for it, I will use XBee.

New question appears :-) How? How to send the sound through XBee and then send it to speaker?

I have to apologize now for my questions. I'm more into digital part of Arduino and more programmer than sound specialist (read: I have never connected speaker/microphone to Arduino and I have abolutely no clue how to do something with it). If you know about some tutorial for newbies on this subject, please throw it at me. Better to know what I'm heading into than buying 100$ HW and not being able to use it...

Let me thank you for your answers, I appreciate it.

I don't understand why you have ruled out RaspberryPIs. They are not expensive - ok you need to add a wifi dongle or something similar but they are probably cheaper than an XBee shield. And RPIs have lots of alternative uses.

More importantly, they have the processing power to deal with sound properly.

...R

Robin2: I don’t want to use RPis because I like raw electronics more. And I would like to run this from battery (independent on AC), which RPi could do too, but it needs far more power. Due to low ppower requirements Arduinos can be used afterwards for other (less valuable/more useless) projects. Having XBee is some kind of bonus (RC car, meteo, home automation, …).

RPi is not bad, I already thought about buying one (and I will, I want to have PC control over house automation done by Arduinos, thus I need RPi between Arduinos and home LAN). I agree with you abou the processing power and with other uses. XBee is ~25$ and shield ~10$. RPi is a little more expensive + you need some wifi.

Get an Ip wIfI camera, some of them have two way voice (or sounds!)

Get serious. :astonished:

Go buy the baby monitor. Be honest. Find some other excuse to play with Arduinox. Don't even bother trying to justify it to the wife in such an absurd manner. ;)

If the cost is genuinely a problem, get it from China on eBay. It will still be quicker in the end. :D

{Personally, I find the concept of "baby monitors" perverse - babies should always be in the same room as the mother - why would do do otherwise?}

babies should always be in the same room as the mother

Well that's sexist. Fathers are capable of taking care of babies, too.

I think maybe we are not talking about the same devices.

Baby monitor: I meant walkie talkie thing with one way (or two way, doesn't matter) communication triggered by higher noise level (compared to ambient noise). (Maybe) You meant the thing with pulse/respiration sensors + the voice transfer (that voice transfer that I meant).

I don't know what is (let's say) normal where you live, but I think that it is okay to let baby (~3 months old) sleep in stroller out in the garden and sit inside the house drinking coffee or reading book (or vice versa, baby in it's bed inside and me outside). The device I wanted to make should only tell me if the baby needs attention or not. It should do nothing more than this. Think of it as extended ear, nothing more.

This is why I wanted to make it instead of buying one-use-only-pre-made-thing. To be honest - If I don't make it from Arduinos, I will buy some standard walkie talkies with noise level trigger and use them for this kind of work. Yeah, they don't come in happy colors, but they can be used afterwards (in two cars driving on holiday, for older children as play things - almost every boy wants to have walkie talkie, etc.).

I tried to get my idea pretty straight this time, hope you got the feel of it. Sorry for previous misunderstandings.

There have been a good few billion children reared successfully without any baby monitors - including my brother and I.

If babies were not robust the human species would have died out long ago.

The negative environmental impact of building and operating baby monitors is probably a greater threat to the human species than the lack of baby monitors.

...R

If babies were not robust the human species would have died out long ago.

And parents become tuned to hearing a baby cry, when no one else in the room can.

PaulS: Well that's sexist. Fathers are capable of taking care of babies, too.

I've not seen many with boobs - though I have to be guarded saying that, given the present trend to obesity.

I've not seen many with boobs

There are bottles and formula. Breast-feeding is not the only way to feed a baby, and isn't the only thing that a crying baby needs.

PaulS: There are bottles and formula. Breast-feeding is not the only way to feed a baby, and isn't the only thing that a crying baby needs.

:astonished:

My wife (the one with the boobs) chips in to say that of course, there's always McDonalds if you can't cook, too. XD

I know, OT, but I just thought I'd mention it.

We can probably move to "Is it possible to make walkie talkies using arduinos?"

I will buy two nanos, two shields for them (XBee, NRF24L01, 3pin outputs, ...) and 2x NRF24L01. It either will work or it will not. I can use all the parts in any future project it this one is not working.

Pavouk106: We can probably move to "Is it possible to make walkie talkies using Arduinos?"

It is, but equally practical to use PCs.

The point is, the Arduino is superfluous for this. It is a digital device, where your requirement is to convey an analog signal. You could just as well connect an ADC directly to an XBee and a DAC at the other end. You are also going to require a microphone and amplifier, and an audio amplifier and speaker at the other end.

Pavouk106: I will buy two Nanos, two shields for them (XBee, NRF24L01, 3pin outputs, ...) and 2x NRF24L01. It either will work or it will not. I can use all the parts in any future project it this one is not working.

Do have fun. That's OK, but do remember - this is only ever for the academic exercise and going to be ridiculously cumbersome and inefficient. You will be outlaying many, many times the cost of a baby monitor.