RF bit bot

[FirefighterBlu3]

General approach is a tiny module that is powered by a solar cell to recharge a capacitor which drives ~6 high brightness LEDs for about 5 minutes when it receives an RF signal. The idea is that these LEDs will light up and start rapidly blinking when a RF trigger enters a given radius. I'd like to build the circuit in less than 2cm by 2cm square, and about 7-10cm tall.

What I need to find is an RF module/chip that controls a true/false logic indicating to a tiny microcontroller when to power up and run a simple program. I think I can handle the rest of the circuitry fine but I need to find a chip that I can set up to handle the RF listening. Ideally I'd like the range to be about 250-500ft and this should be considered an outdoor device.

The end result is a tiny box I can affix to a poly/fiberglass rod which will be located on/near a fire hydrant. It's purpose is to indicate where a fire hydrant is positioned during heavy snowfall.

Suggestions welcomed I have no RF signal constraints other than the FCC, no special design requirements except for very low sleep current. There may even be an analog method but I am _horrible_ at analog theory =]

 

[kchriste]

The end result is a tiny box I can affix to a poly/fiberglass rod which will be located on/near a fire hydrant. It's purpose is to indicate where a fire hydrant is positioned during heavy snowfall.

Your problem is going to be; trying to get a solar panel to work in the winter and under heavy snow. Not gonna happen!
The pole by itself will be more effective, as any solar panel will get covered in snow even if it's on top of a pole.

 

[blueroomelectronics]

A kinetic generator might work, hi tech farmers use them with Zigbee in the fields.

It's a good idea to be able to find hydrants hidden by snow etc, would it not be cheaper to simply map them with a GPS on something like google maps. After all hydrants don't tend to move around much.

https://www.engadget.com/2007/07/06/tiny-generator-turns-vibrations-into-electricity/
**broken link removed**

 

[Torben]

I agree with kchriste: just use a pole, maybe with a bright red flag or something on top. No power worries, no RF worries, no special enclosure requirements, etc. Oh yeah. No unscrupulous hobbyists stealing your nifty little devices for parts.

In Finland they have a good, cheap method of locating the sides of the road for the snowplows when the snow is too deep to see what's what: they just put sticks in the snowbanks so the plow operators see them poking up. Problem solved.


Torben

 

[Nigel Goodwin]

I agree with kchriste: just use a pole, maybe with a bright red flag or something on top. No power worries, no RF worries, no special enclosure requirements, etc. Oh yeah. No unscrupulous hobbyists stealing your nifty little devices for parts.

In Finland they have a good, cheap method of locating the sides of the road for the snowplows when the snow is too deep to see what's what: they just put sticks in the snowbanks so the plow operators see them poking up. Problem solved.

You've got to admire the level of technology in Finland!

But seriously, if something works perfectly, and has nothing possible that can go wrong, why try and 'improve' it?.

 

[Torben]

You've got to admire the level of technology in Finland!

But seriously, if something works perfectly, and has nothing possible that can go wrong, why try and 'improve' it?.

Hehe. Actually when I moved back to North America I felt like I'd gone back in time (tech-wise) about 10 years. Guess when you have a small land area and population it's easier to upgrade and keep everything working together. I wonder what folks who live in Japan must thing when they visit N.A.?

I do admire the Finnish pragmatism: if it ain't broke, don't fix it.


Torben

 

[FirefighterBlu3]

I'm not awfully worried about the solar cell getting covered up since it's highly unlikely the hydrant indicator would get activated very often. I'm sure 5 minutes of LED activity plus residual sleep drain will be more than assured by the days of non-snow. As for GPS, unless you pay ungodly amounts of $, it's not accurate down to a 15 inch radius. We already have them marked on maps which means we can eventually find them after poking shovel handles down in the snow. It just takes time, time I'm trying to reduce. I am trying to improve the near instant-find of a hydrant that is buried under snow in the middle of the night. Reflective tape on a fiberglass rod is sometimes effective but doesn't work great when it's even a little dusty, weather worn, etc. The kinetic block looks nifty as a power source too.

Why improve the gas mileage on your car? Why improve the function or speed of your circuit? Why use LEDs instead of bulbs, or integrated chips instead of discrete components? Just because it isn't broke doesn't mean it can't be better.

All that aside, I'm still looking for a tiny RF chip that does as described above.

 

[Brian Hoskins]

But seriously, if something works perfectly, and has nothing possible that can go wrong, why try and 'improve' it?.

Because you can?

Brian

 

[Nigel Goodwin]

Because you can?

As long as it's actually an improvement, but if something works perfectly, is highly reliable, is cheap, and requires no maintenance, 'improve' probably isn't a term that really applies.

The proposed solar powered system, is likely to be fairly unreliable, and require frequent maintenance - for which reasons I would discount it.

 

[FirefighterBlu3]

flags and reflectors are not highly reliable and require annual maintenance.. it is unlikely that a solar cell will be unable to maintain the minimal charge needed for an a 5 minute LED source every couple of months at most. what this design does offer as a benefit is a light emission which doesn't require headlights or flashlights to aimed directly at it and not have a dusty reflective surface.

 

[Torben]

Reflective tape on a fiberglass rod is sometimes effective but doesn't work great when it's even a little dusty, weather worn, etc.

Here in northern Canada, highway reflectors do much better than tape, with only minimal maintenance (perhaps a wipe every so often). At least around here, hydrants are kept clear by highways or city workers as part of their snow removal duties.

Why improve the gas mileage on your car? Why improve the function or speed of your circuit? Why use LEDs instead of bulbs, or integrated chips instead of discrete components? Just because it isn't broke doesn't mean it can't be better.

Those are disingenuous and not relevant examples, as they all feature obvious improvements--except for the LED one, which I would consider to be application-specific. I don't think adding multiple possible failure modes for little benefit is "fixing" something.

All that aside, I'm still looking for a tiny RF chip that does as described above.

I'd say to check out Sparkfun.com if you haven't already; they have a bunch of wireless modules which might work for you (ZigBee, wifi, Bluetooth, etc)--although I don't know whether the range would be sufficient for what you want.

Another thing to consider (if you haven't already) is the batteries and the expected temperature range. Not all batteries will charge or discharge well in extreme cold. Where is the target market for this? I'm guessing not southern Florida.


Torben

 

[audioguru]

I looked outside a minute ago and I saw three fire hydrants running down the road. With three pink elephants. Hee, hee.