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Subject: Re: Designing wireless controllers

Date: 06/09/00 at 3:47 AM
Posted by: Bill Lewis
E-mail: FS.consult@eudoramail.com
Message Posted:

In Reply to: Designing wireless controllers posted by Jeffrey Schwartz on 06/05/00 at 9:35 PM:

Hi Jeff,

You need the three seperate transmitters on seperate carrier frequencies.

One suggestion is to have them crystal or PLL controlled and spaced say 50Khz apart.

have a reciever that has a mixer that convertes the input carrier(s) down to baseband (say 50-200Khz) then use a PLL (NE567?) for each channel (50khz,100khz,150khz) to detect a key press.

you may need to tweak the PLL filter for each Ne567 so they all have the same response time.

This will give three logic outputs which you can put in to some voting logic (latches (74hc74), whichever latch sets first, its output clears the others.) you add a button to clear the latches down manually to reset it.

Another possible solution is to have the transmitters seperated by some Mhz. then amplify at the reciever and place through a simple tune circuit bandpass filters for each channel, then into a diode detector and onto an opamp to bring it up to logic levels.

then put it through the vote circuit as before.

this last one would be susceptible too false triggering and noise though.

The PLL version will only accept signals inside its bandwidth.

There hope that gives you some ideas.


Bill Lewis
Technical Director
First Strike Consultants Ltd

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