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radio frequency circuit design

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Ron H said:
Spend some time learning to program it. As we have told you, it is the answer to your noise problem. You could spend months farting around with different kinds of comparators (a comparator is not an op amp) and filtering schemes.
Ron, A microcontroller can be a solution, BUT it must be programmed. If bananasiong is willing to spend time programming it correctly, then it may be no problem.

I am detecting remote signals myself, and all I am doing is making a simple PLL using a 555 timer, 2 XOR gates, and 2 NAND gates.


Also, if you get your transmit and receive frequencies to match, you will get better noise rejection.
I agree 100%. If the frequency is even slightly off, and the bandwidth of the transmitter is not high enough, the range will also drop, and the signal quality will be poorer.


If you want to learn from a project, one of the most important things you can do is understand why it doesn't work the way you think it should.
One way you can do that is to picture the project in your head, and pretend you are the electricity flowing through it.

if there's a spurious short '0' do as already advised and software filter it - basically don't respond unless the '0' lasts more than a certain time.
A software filter, very interesting :wink:
BUT, you must understand that if you intend to use the same microcontroller for another application at the same time, you must consider the rom space required for the filter, and subtract that from the total rom space.

i don't think it can be used perfectly if the receiver gives a short off when there is no signal. because my microcontroller keeps detecting the output of the receiver, if there is a '0', it will response to it and turn.
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if there's a spurious short '0' do as already advised and software filter it - basically don't respond unless the '0' lasts more than a certain time.
Nigel does have a point. What he is introducing is what is called a "timeout". Assuming that "no signal" or an invalid signal produces a binary 0, If the result is 0 long enough, then you can make the microcontroller go to an error routine.

BUT

this will only work if your transmitter transmits a continuous "1" bit.

If your transmitter transmits a certain tone as a logic high, a PLL should be used to detect the signal.

and continuously transmitting a "1" can waste power.
 
hi all,

i just tested these circuits today. the tx works as few days ago, now it give me nice 10KHz square wave.
but the rx, even there is signal or no signal, it gave a square wave :roll: :roll: it is not a nice square wave.. it seems combination of a few square waves, looks noisy. the rx is not affected by the tx anymore. what's the problem? may it be the LM393?
 
bananasiong said:
hi all,

i just tested these circuits today. the tx works as few days ago, now it give me nice 10KHz square wave.
but the rx, even there is signal or no signal, it gave a square wave :roll: :roll: it is not a nice square wave.. it seems combination of a few square waves, looks noisy. the rx is not affected by the tx anymore. what's the problem? may it be the LM393?
the freq of the 'noise' sq: wave may hold a clue , are u powering the rx with batt or main power supply ?. power ur rx with batt and move the ckt away from wall plugs and other a/c interferences.
 
mstechca said:
Ron, A microcontroller can be a solution, BUT it must be programmed. If bananasiong is willing to spend time programming it correctly, then it may be no problem.
Duh. :roll:
Go back a few posts. You'll find that I said that at least twice.
 
akg said:
the freq of the 'noise' sq: wave may hold a clue , are u powering the rx with batt or main power supply
currently i'm testing it using a power supply, but battery is suposed to be used.

akg said:
power ur rx with batt and move the ckt away from wall plugs and other a/c interferences.
oh.. u're right.. i didn't think about other sourse can affect also. can i still use power supply to test? i will tell u all the result after testing it tomorrow.. thanks for all ur helping :wink: :wink:
 
hi all,

these circuits work. but i found a problem, when the tx antenna goes near to the rx inductor, the rx output gives a 10KHz square wave, that is what i want. but it has to be very close in order to get the signal. i mean the tx antenna has to be very close to the rx coil (less than or around 1cm only). can i increase the range by increasing the supply to the 555 timer? i can't increase the rx supply because i have to fix it in my robot using battery. thanks for all your helping. :D
 
your coil could have more than just one conductor. transmitter coil for AGVs using this type of guidance uses frequency in audio range (some 4-5kHz) and cable instead of wire. ends of cable ware terminated so that it appeared as multi turn coil. This part was done before I had chance to take a closer look but I think it was only some 4-5 turns (or conductors in cable). if more power is required to drive the coil you could use transistor after 555 chip. 555 is not very strong, don't stress it too much.
 
panic mode said:
your coil could have more than just one conductor. transmitter coil for AGVs using this type of guidance uses frequency in audio range (some 4-5kHz) and cable instead of wire. ends of cable ware terminated so that it appeared as multi turn coil. This part was done before I had chance to take a closer look but I think it was only some 4-5 turns (or conductors in cable). if more power is required to drive the coil you could use transistor after 555 chip. 555 is not very strong, don't stress it too much.

sorry. i really don't get the point..
what is " ur coil could have more than just one conductor"??
what is AGV??

and.. the last sentence, u mean i shouldn't increase the supplied voltage to increase the range? then what should i do? and what is the maximum voltage?
thanks for helping. :D
 
panic mode said:
http://www.agvp.com/navigation_wire.htm

what do u think of this? should i make any changes in the circuit? :roll:
is there any problem with my receiving coil?
 
Can the circuit given by ruff be used as a buried wire fence for a robotic lawn mower? The mower has to move inside this wire fence only.

Thanks
 
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