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How to control relay using DTMF and AT89S52?

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bianchi77

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Friends,

Anyone knows on how to control relay using DTMF (MT8870) and AT89S52 ?
How can I make the circuit answer the call automatically and accept command from DTMF ?

The idea is, if there's a call, the circuit will auto pickup after 3 beep and ready for a command from a remote phone, for example, numeric "1" for turning on "relay 1"

Thanks for the info
 

I am also doing the same project... but without using any microcontrollers..... am in the starting stage of this project...
this link may help you: **broken link removed**

i think each output Q1 to Q4 will go to Relay switch.... :)
 

bianchi77 said:
Friends,

Anyone knows on how to control relay using DTMF (MT8870) and AT89S52 ?
How can I make the circuit answer the call automatically and accept command from DTMF ?

The idea is, if there's a call, the circuit will auto pickup after 3 beep and ready for a command from a remote phone, for example, numeric "1" for turning on "relay 1"

Thanks for the info
Click to expand...

What do you need? source code or hardwares schematic?
perhaps you need:
* ring detector
* Automatically pick up the phone
* DTMF Detector
* reverse polarity

actually on this forum that discusses many of your project ...
stay you search in this forum..
 

Li_ereunpisan said:
What do you need? source code or hardwares schematic?
perhaps you need:
* ring detector
* Automatically pick up the phone
* DTMF Detector
* reverse polarity

actually on this forum that discusses many of your project ...
stay you search in this forum..
Click to expand...

I need ring detector and automatic answer circuit, do you have one ?
 

bianchi77 said:
With this circuit,
I think, we will short the circuit to R 600 ohm, I modify abit...see above
or we need this 600 ohm for telling the central, "off hook" ?

may be I need a big wattage resistor ?
Click to expand...

above circuit .. it will not work ....
I use resitor 2 watts is more than enough
 

Li_ereunpisan said:
above circuit .. it will not work ....
I use resitor 2 watts is more than enough
Click to expand...
Ok I will use this circuit with 2 watts 600 ohm resistor, right ?
detring_auto pickup-5.JPG
 

For DTMF detector DTMF decoder, can I use 20V Zener diode ? anyone has the schematic ?
thanks
 

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