Some questions about some ideas for projects I want to build

Wireless & IoT
1

I have recently been addicted to wanting to build some projects and I have a few different ideas that have been floating around in my head. I have some questions about how I would go about accomplishing some of these things.

  1. I have been thinking about making some kind of small transmitter that I can have on my person, so as I near certain spots in my house, I can have a receiver that senses when I get within a set range, and then do something (turn lights on/off, unlock/lock doors, lock my pc, ect…) I am guessing some kind of RF circuit would do.

  2. I want to make some wireless computer speakers using Blue tooth. Most of the audio amp IC’s that put out any kind of decent power take at least 12V, but I would like the option for charging the speakers through the USB port on my computer (even if it takes 3 or 4x as long to charge.). How could I make a charging circuit that would implement some kind of switching to switch charging multiple liPo batteries (each one putting out 3.7v). I am guessing that that charger would switch multiple times a second, taking turns charging each cell individually, however that batteries would be wired in series so I could get 11.1 or 14.8 volts to power the amp with. Or should I wire a few in parallel to get more amps, and then step up the voltage to operate the amp with?

Thanks for the help guys. I love this website, lots of cool circuits.

Oh yeah, one other thought. I don’t have any internet access at work so I have been toying with the idea of making some kind of very tiny, very low powered wireless bridge so that I could place them in a chain in some spots (telephone poles?) that aren’t very noticable, so I can use my own network connection at my home. My work is about 3 miles away, and is while some parts of the drive have LOS, the first and last leg aren’t (hills). I was thinking some cheap blue tooth or zigbee modules (or?). Any thoughts on that? Ideally they would be very inexpensive to make so if one of them is removed for some reason, I can replace it cheaply.

2

jdraughn:

  1. I have been thinking about making some kind of small transmitter that I can have on my person, so as I near certain spots in my house, I can have a receiver that senses when I get within a set range, and then do something (turn lights on/off, unlock/lock doors, lock my pc, ect…) I am guessing some kind of RF circuit would do.

RFID might be your friend, if you can deal with having to get within 10cm of the RF receiver… Perhaps you could take the other approach - use a PIR sensor to detect your person and trigger devices accordingly. Of course this will work for everyone and not just you, so you’ll have to be careful. Perhaps look at OpenBeacon?

http://www.openbeacon.org/start.0.html

jdraughn:
2. I want to make some wireless computer speakers using Blue tooth. Most of the audio amp IC’s that put out any kind of decent power take at least 12V, but I would like the option for charging the speakers through the USB port on my computer (even if it takes 3 or 4x as long to charge.). How could I make a charging circuit that would implement some kind of switching to switch charging multiple liPo batteries (each one putting out 3.7v). I am guessing that that charger would switch multiple times a second, taking turns charging each cell individually, however that batteries would be wired in series so I could get 11.1 or 14.8 volts to power the amp with. Or should I wire a few in parallel to get more amps, and then step up the voltage to operate the amp with?

You would be better off either using a dedicated LiPo charging circuit (they often come as battery ‘back-pack’ PCBs, you can find some at www.batteryspace.com) and using a switch-mode regulator to either turn USB’s 5V into 10-15V to charge the battery, or 3.7V from parallel LiPo’s up to 12V for the speakers. Depends on what the speakers require, what your bluetooth device requires, etc. A note of caution: LiPos can spontaneously combust if you mistreat them - even just letting them overcharge or overdischarge or short circuit. You would really want to know what you were doing before you go playing with them, or at least wear safety goggles and work over a metal container.

jdraughn:
I don’t have any internet access at work so I have been toying with the idea of making some kind of very tiny, very low powered wireless bridge so that I could place them in a chain in some spots (telephone poles?) that aren’t very noticable, so I can use my own network connection at my home. My work is about 3 miles away, and is while some parts of the drive have LOS, the first and last leg aren’t (hills). I was thinking some cheap blue tooth or zigbee modules (or?). Any thoughts on that? Ideally they would be very inexpensive to make so if one of them is removed for some reason, I can replace it cheaply.

Only slightly illegal I would think (installing wireless communication devices on private/government property). How would you power them? Don’t go poking around power line cables to see if you could ‘borrow’ some power… The best solution here is to use some high-gain antennae placed on the very edge of either property, and hope the signals will be strong enough to reach each other (bounce off a nearby hill perhaps? Or a building?). Make sure you don’t exceed the maximum EIRP for your wireless - you shouldn’t have much trouble with 3 miles though.

Will.

3

Krogoth:
RFID might be your friend, if you can deal with having to get within 10cm of the RF receiver… Perhaps you could take the other approach - use a PIR sensor to detect your person and trigger devices accordingly. Of course this will work for everyone and not just you, so you’ll have to be careful. Perhaps look at OpenBeacon?

http://www.openbeacon.org/start.0.html

Thanks for the link.

Yep, that is the whole point, I only want it to work with me. I am thinking of automatically unlocking my car when I get like 2’ from the door, or automatically unlocking my front door when I get like 2’ from the door, ect… Or locking my PC when it senses that I have moved away from it, and then unlocking it when it senses im near it.

Krogoth:
You would be better off either using a dedicated LiPo charging circuit (they often come as battery ‘back-pack’ PCBs, you can find some at www.batteryspace.com) and using a switch-mode regulator to either turn USB’s 5V into 10-15V to charge the battery, or 3.7V from parallel LiPo’s up to 12V for the speakers. Depends on what the speakers require, what your bluetooth device requires, etc. A note of caution: LiPos can spontaneously combust if you mistreat them - even just letting them overcharge or overdischarge or short circuit. You would really want to know what you were doing before you go playing with them, or at least wear safety goggles and work over a metal container.

Ahh yeah, I am well aware of the safety issues with lipos, which is why I am doing the research now. I want them to be very safe, but they look to be what the doctor ordered as far as light weight, good current , small size and fast charging.

Krogoth:
Only slightly illegal I would think (installing wireless communication devices on private/government property). How would you power them? Don’t go poking around power line cables to see if you could ‘borrow’ some power… The best solution here is to use some high-gain antennae placed on the very edge of either property, and hope the signals will be strong enough to reach each other (bounce off a nearby hill perhaps? Or a building?). Make sure you don’t exceed the maximum EIRP for your wireless - you shouldn’t have much trouble with 3 miles though.

Will.

My intention was never to borrow any power. On my way home from work today I was really looking around to see what my options were. I am sure I could convince some people to let me put something on top of their house, but what I was actually thinking of was a very small disk that was about 2 or 3" round with a solar cell on top to keep a battery charged. I was wondering if I could place them on the very top of some telephone poles. The only people who would ever see them would be power line workers. Only problem is figuring out how to put them up there. No way im climbing any lines. I was thinking of maybe some sprinkler pvc pipe to make like a 30’ long stick to somehow get them to the top of the poles. Ahh well, all speculation anyway. I don’t think I could ever get up the nerve to actually do something like that anyway.

4

Try this Yamaha NX-B02RE Bluetooth Wireless Stereo Speaker.

It can receive audio from devices that support the Bluetooth 2.0+EDR A2DP protocol. These include many PCs, PDAs, and mobile phones. It features a standard stereo mini jack for device connectivity. It is convenient music enjoyment from Bluetooth-compatible PCs, PDAs and mobile phones. It is affordable and convenient to use.