Hacked Gadgets Forum

January 30, 2010

DTMF Decoder Board Project using the MT8870

at 11:28 am. Filed under DIY Hacks, Electronic Hacks


Victor Youk from Razor Concepts has designed a nice DTMF Decoder Board Project. The project is based around the MT8870 DTMF Decoder chip. With this project you will be able to control something from around the block or around the world using a simple telephone. Nice feature of using the MT8870 is you don’t need to program anything, just purchase all the components, stuff them onto a breadboard and have a working circuit in a few hours. Victor has provided a full schematic so you can build your own.

MT8870_DTMF_Decoder_Datasheet (PDF)

“The heart of this device is the MT8870, which is a DTMF to BCD decoder chip. It takes an analog audio input, and converts that to a 4-bit binary output. Those 4 bits are put into a BCD decoder, and that converts that into the corresponding 0-9 output. Various other devices were needed to complete the board, and can be seen in the board layout below.”



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4 Responses to “DTMF Decoder Board Project using the MT8870”

  1. DTMF Hack – How to Make a DTMF Decoder! Says:

    […] via hackedgadgets […]

  2. Santiago Says:

    As usual in hacked gadgets :p, one semester late for my proyect. Yeh, well, we used the mt8870 to decode signals from a cellphone to a smallcar, it worked apparently awsome, the only problem was that we didn’t know that you needed 10N to press the answer button on the other side. Thanks anyway, I’ll see if I can remake the proyect with this and send it to you, although, a new semester has began, thus I have to work on another totally different proyect.

    Greetings from Colombia
    (Ah, remember the message from the Future: Come to Colombia”)

  3. olajide Says:

    oh, am doing something similar but am confused somewhere. you said something about needing a 10N to press the answer button on the other side…this is exactly my problem. how do i get the other phone pressed to activate the call? many thanks. olajide from nigerian defence academy, kaduna, nigeria.

  4. Santiago Says:

    Yeh, the buttons on a cellphone are harder to press than they appear, mechanically can get really messy, I would suggest using a single relay (tho’ is mechanical someway) to joint the contacts of a single button if the cellphone model is old, easily recognized by rubber. Uh, this hack… isn’t really extended over the internet, for security reasons I suppose.

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