Newbie in great need of help ! ! !

[bobwilmott]

Hi All,
Complete newbie here, so hope I'm not asking the impossible.
What I'd like to make is a transmitter/receiver, perhaps based on the 433MHz RF transmitter and receiver wireless kits widely advertised on eBay for £1 or £2.
The transmitter needs to be battery-powered (hopefully 1.5v or 3.0v) and sends a signal which the receiver picks up within say 200 metres. When the receiver picks up the signal, it buzzes or beeps or flashes. Simple, huh ?
Is this do-able ? What bits and pieces would I need apart from the wireless kit ?
Thanks,
Bob

 

[HellasTechn]

Good day and Merry Christmass.

Ever thought to use a wireless dorbell ? though i doubt it can reach 200m or you want to make it yourself ?

 

[bobwilmott]

Hi HellasTechn, and a merry Christmas to you too.
I could possibly adapt a wireless doorbell, but I do need a range of around 200 metres.
Any other ideas, anyone ?

 

[bobwilmott]

I should add that the transmitter, when switched on, has to emit a continuous signal until it's switched off.

 

[HellasTechn]

What do you mean emit a continuous signal ?
Like to always transmit the signal untill you turn it of ?
If so then how will the receiver be able to "know" when it should ring ? Will the transmittion be different when you need it to trigger the receiver ? or maybe the receiver will be triggered when the transmitted signal reaches a certain voltage? (Amplitude modulated).

 

[bobwilmott]

Yes, a continuous signal for perhaps two or three days. The receiver will buzz or beep or flash when the transmitter and receiver come within range of each other. Perhaps the transmitter will need to be powered by 12v from a mains transformer ?

 

[donkey]

I have to ask why you need it continually on?
you could change it a little to have it emit 2 codes. 1 to turn on 1 to turn off. simply put if this was to measure if a gate was open or closed for example then when it is open it transmits code "open" which sounds an alarm. the transmitter than conserves power by not transmitting continuously but instead reads to see if the gate is closed (changes state) then if it is closed it transmits code "closed" and the alarm stops.
as for broadcasting that range there are a few items that come to mind but it really depends on what is between point a and point b.

 

[KrisBlueNZ]

Bob, perhaps you're looking at this the wrong way. People here have a wide variety of experience and knowledge. If you describe what you want to do, rather than how you think it should be done, we may be able to save a lot of time and suggest something you hadn't thought of.

 

[bobwilmott]

Thank you Donkey and KrisBlueNZ.

Donkey... Yes I had thought about ways to conserve power, but I'm so ignorant about electronics that I'd rather keep it very simple until I master the basics, then refine it !

KrisBlueNZ... You're right, of course. Well, I guess what I have in mind is a type of proximity detector which tells when two things come within a certain range of each other. Something like the child protection things that tell you when your toddler wanders too far away, but the other way around.

Would a kit like this one be a good basis for what I want ?
http://www.ebay.co.uk/itm/400815039971?_trksid=p2060778.m2749.l2648&ssPageName=STRK:MEBIDX:IT

If so, how would I connect batteries to the transmitter and the receiver, and how would I connect a buzzer to the receiver ? Would I need any other bits and pieces to make it work ?

Yes, I am clueless

 

[KrisBlueNZ]

Well, I guess what I have in mind is a type of proximity detector which tells when two things come within a certain range of each other.

Two things?

I'm guessing that telling us what kind of "things" you're talking about wouldn't violate any non-disclosure contract or compromise national security?

Telling us this simple little piece of information will tell us a lot more - for example, the size of each "thing" so we know whether a battery can be installed on it, and some idea of the distance threshold, and the environment. You could tell us those three things, but that would still leave questions unanswered. So why not start from the beginning and tell us all about it?

 

[bobwilmott]

OK, so this is my 101st attempt to invent something that will make me rich and famous. Just because the first 100 failed dismally doesn't mean that this one will too, but I guess that prior disclosure on the internet would be the death knell for a patent application That's why I'm being rather vague.

Anyway, the two "things" could be just about anything, but let's say they are both motor vehicles (obviously sources of power if little batteries are not enough), at any distance from each other up to say 200 yards, perhaps with the odd tree or whatever between them.

When the two things come within range of each other, the beeper beeps quietly/slowly. The closer they come, the louder/quicker the beeps. Oh, and a digital compass would be great, to show one thing roughly which direction the other is.

Eezy-Peezy ?

 

[KrisBlueNZ]

I understand your concern about protecting your idea from copying, but based on prior experience, I think it's almost certainly misplaced. From what I've seen, when people with little or no experience in electronics come up with a great new idea, it's the kind of thought that many other people have already had (so there's little risk in revealing it), and it generally turns out that it's not feasible for one or more (usually more) reasons, or it has already been done by a commercially funded team of people experienced in the field.

Radio signal strength is not a good way to measure distance between objects because it is affected by many other factors such as antenna directionality (I don't think any antenna has equal transmit power or equal sensitivity in all directions in all three dimensions), and environmental factors such as atmospherics, presence of other conductive bodies such as cars, presence of buildings or hills, etc.

There are ways to measure distance using relatively accurately known speeds - the speed of sound or the speed of radio wave propagation, for example. Sound is not workable in this application but speed of radio waves might be. Unfortunately you need some fairly high-tech equipment to measure the timing shifts (on the picosecond or nanosecond scale) to get useful resolution; it's a lot simpler to leave those measurements and calculations to be done inside a GPS receiver, where they're already implemented.

If you're going to do that, you could just put a GPS receiver on each vehicle and get one to continuously transmit its coordinates to the other one, then write some code to compare the coordinates and produce the warning. Two smartphones (iPhones or Android phones) could do this, using data communication through the cell sites and via the Internet to transfer position information. Smartphones also have digital compasses and are a lot cheaper than designing and manufacturing your own hardware.

 

[bobwilmott]

Thank you, KrisBlueNZ, and I too doubt very much whether my little idea will bring fame and fortune... but it's nice to fantasize !
Bob

 

[BobK]

Yes, two cell phones and a app are what is needed, and would do this far better than anything you could build for less than the price of the cell phones.

Bob

 

[bobwilmott]

Thanks Bob, it's worth looking into. Would that be an existing off-the-shelf app or would I need to write one myself ?

 

[HellasTechn]

There are ways to measure distance using relatively accurately known speeds - the speed of sound or the speed of radio wave propagation, for example. Sound is not workable in this application but speed of radio waves might be. Unfortunately you need some fairly high-tech equipment to measure the timing shifts (on the picosecond or nanosecond scale) to get useful resolution; it's a lot simpler to leave those measurements and calculations to be done inside a GPS receiver, where they're already implemented.

.

Like a signal Direction Finder.

 

[KrisBlueNZ]

Like a signal Direction Finder.

He wants to measure distance, not direction.

 

[HellasTechn]

Direction finders also calculate distance

 

[KrisBlueNZ]

How do they work?

 

[bobwilmott]

For the moment I think I'll forget about refinements such as direction/distance finder and increasing-volume alarm. I'll concentrate on a very basic model. But I'll definitely bear in mind all your comments about the various possibilities and pitfalls. Many thanks for all your help.
Bob