hello !
i have a problem with a school project . i have to send dtmf tones from my PC to MT8870 and display the dialed number.
As BCD-7 seg dcd i used HCF 4511BE and an CC digit and a LM7805 for a 5V supply.
Now, the thing is .. i was a litle confused on how to conect my decoder to the computer so i used an audio jack and inserted into the audio output of my comp.
I tried to send "2" but nothing...the display showed 8 as it was when i just tested the circuit by conecting it only to the supply
After a few hour i decided to try again and when i pluged in the circuit at 5V, the display showed 2 ..o_0.. only this time it was not conected to my computer .. just to the supply.
So i thought ..ok.. the circit memorised the last signal that was sent .. but now i tried "3" and nothing it just displays "2"...
i attached a pic. with the circuit . i apologise for the bad drawing. cand someone PLEASE just check it out and tell me if i did something wrong or if .. a pin is bad-coneccted.
Thank u
i have a problem with a school project . i have to send dtmf tones from my PC to MT8870 and display the dialed number.
As BCD-7 seg dcd i used HCF 4511BE and an CC digit and a LM7805 for a 5V supply.
Now, the thing is .. i was a litle confused on how to conect my decoder to the computer so i used an audio jack and inserted into the audio output of my comp.
I tried to send "2" but nothing...the display showed 8 as it was when i just tested the circuit by conecting it only to the supply
After a few hour i decided to try again and when i pluged in the circuit at 5V, the display showed 2 ..o_0.. only this time it was not conected to my computer .. just to the supply.
So i thought ..ok.. the circit memorised the last signal that was sent .. but now i tried "3" and nothing it just displays "2"...
i attached a pic. with the circuit . i apologise for the bad drawing. cand someone PLEASE just check it out and tell me if i did something wrong or if .. a pin is bad-coneccted.
Thank u
