Mat wrote:
> Budget isn't so much of an issue, sure it's a factor, but at $25-50 a unit,
> this is a fraction of the overall cost, and probably easily justified. The
> power and boot up times however is a bigger problem. The best solution could
> possibly be a hybrid of both, using the gps on fixed nodes and relaying this
> via the radio to the battery node. Still pondering this as a concept...
>
> Mat 
>
>   
I have been busy- I think I missed most of this thread. If the task is 
having a unit "check in", I have done
it with a pseudo-random generator, and have each one check in at 
deliberately different times. There
will be an occasional collision, but if the number of units are few, it 
works quite well. Just have the unit
check in twice as often, but have the interval quite random, and it 
works well; you can't get a collision
every time..

If that wasn't the subject, then pay no attention to the man behind the 
curtain.

--Bob
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
> Art
> Sent: 14 October 2006 17:29
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] Radio Synchronisation
>
> I'm looking for a timing GPS now.
>
> You didn't mention your budget.
>
> But, all of the GPS solutions require lots of power, although it's 
> easily accurate to within 1 us. OEM modules can be had for 25 to 70 
> dollars each though, so perhaps this is viable.
>
> GL
>
> Art
>
>
>
>
>
> At 10:54 AM 10/14/2006, you wrote:
>
>   
>> Stupid me. Although particularly obvious, this had totally passed me by,
>> I'm so use to saving power where I can, it comes automatically to me now!!
>>
>> I think this combined with a GPS reciever could be the solution to all my
>> problems!
>>
>> As to why they need to be that synced, (thats a secret :P). I've
>> questioned the spec a few times, but I'm told it's necessary by the powers
>> that be.
>>
>> Mat
>>
>>
>>     
>>> Maybe I missed something - this sounds too easy.
>>>
>>> Power at the transmitter is effectively unlimited, right? (o.k. 11
>>>       
> watts,
>   
>>> but that's still lots) Why not just send a time signal out continuously,
>>> and let the receiver read it whenever it wakes up? The transmitted data
>>> stream could be a time packet followed by some form of sync pulse -
>>> something like $5A5A, then the reciever snychronizes with the next
>>>       
> rising
>   
>>> edge.
>>>
>>> I'm more interested in why the units need that level of sync.
>>>
>>> -Denny
>>>
>>>
>>>
>>>
>>>       
>>>> I'm currently working on a design with a specific problem, which I'm
>>>> hoping someone will have come across before.
>>>>
>>>> Essentially I have several remote circuits, which must remain
>>>> unconnected.
>>>> They all need to be synchronised within 100 Micro Seconds.
>>>>
>>>> Essentially we are looking at deploying a beacon transmittor which will
>>>> send out a pulse at known intervals and have low power recievers on
>>>>         
> each
>   
>>>> circuit which come out of hibernation at the required interval, to
>>>>         
> reset
>   
>>>> the onboard clocks appropiatly.
>>>>
>>>> We are looking at achieving 100m range (indoors), however power at the
>>>> beacons is not a significant problem (we have 11Watts available, and
>>>> these
>>>> are not battery powered). Power at the recievers is crucial, each
>>>> circuit
>>>> is powered by battery and must be capable of running for a minimum
>>>> period
>>>> of a year. Physical battery size is not crucial but small is better :)
>>>>
>>>> Does anyone have any other suggestions how to achieve the required
>>>> synchronisation, or can anyone suggest any suitable radio IC's/circuits
>>>> which could be used as I am stuggling to find anything useful via
>>>>         
> google
>   
>>>> (must be using the wrong keywords)
>>>>
>>>> Any suggestions or comments would be greatly appreciated.
>>>>
>>>> Mat
>>>>
>>>>
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>   

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