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How to build an ASK Modulator ?

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hay2night

New Member
Hi guys,

I have to make a project for school based on X10 protocol theory.
What i have to do is to build two circuits that can transmit and a receive bits over the electrical power lines.

I have found some useful materials about that but i have a problem that i cant resolve at this time.
I don't know how to build an ASK modulator (which i'm gonna use in the transmiter circuit)The modulator signal comes from a microcontroller (bits ) and the carrier is a sine wave at 100KHZ. :confused:

Can u help me please with a scheme for the ASK modulator ?? (A light one that i'll be able to undersand)

Thanks a lot
 

Sceadwian

Banned
Can you do on/off shift keying (it's a form of ASK) or do you need a true two level ASK?
 

hay2night

New Member
Yes...i can use on /off shift keying.That's ok
I have been told that i can use a transistor to do that but i don't know yet.

Can you tell me how or can you put here a circuit please ?
Thank you.
 

Mikebits

Well-Known Member
ASK modulation is prone to many problems, such as noise. Considering that your using X10 I assume your using power lines in which case there will be lots of noise, many errors. Perhaps a different modulation scheme should be used.
 

hay2night

New Member
Thanks for advice but I told you that I am a newbie in electronics although I study it at school.:D
I have to do a modulation of a sine wave(100KHz) with bits coming from a uC like i said.(where is "1" there will be a presence of the sine , where is "0" there will be an absence of the sine....isn't it good ?)
I am not constrained to use ASK , but i believe it's the easiest possible type.
I must tell you that i want the receiver to use bandpass filtering to extract the signal not a kind of complex demodulator.

Thanks.
 

Mikebits

Well-Known Member
Thanks for advice but I told you that I am a newbie in electronics although I study it at school.:D
I have to do a modulation of a sine wave(100KHz) with bits coming from a uC like i said.(where is "1" there will be a presence of the sine , where is "0" there will be an absence of the sine....isn't it good ?)
I am not constrained to use ASK , but i believe it's the easiest possible type.
I must tell you that i want the receiver to use bandpass filtering to extract the signal not a kind of complex demodulator.

Thanks.
The BPF does not extract the signal, it only limits out of band noise. You will have to use a demodulator in any case. I would suggest PSK modulation as this is less affected by noise. Consider AC power is a very noisy environment, and noise will affect the signal.
 

hay2night

New Member
Mikebits : You're right. There was an amplitude detector in my scheme at the receiver :D (which is a demodulator)
How to use PSK ? :D
Do you have a helpful link or book or scheme ?:)

Thank you
 
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