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I did not take a look on the code above, however I can´t see much issues in generating dtmf tones, if there is available 2 timers to store the fundamental frequency of each tone. Just reload the timer register accordingly.
You cannot connect it directly, you should use an isolating transformer. Also note that for a telephone line to receive dtmf it normally has to be active ("off hook") so you also need the circuitry to seize the line or you have to use a conventional telephone to answer the line and connect the MT8870 to it. Please bear in mind that voltages as hi
Not popular much anymore but this is done in SLIC chip. e.g. look at MOT chips ( ON Semi) and Agere SLIC chips ( Now Avago )
Hello all, I am working on a project that has use of telephone. I have a problem that I want to detect the ring signal from the telephone so I have created the ring detector circuit. But before the telephone rings, I want to place security. the caller have to enter the password. So I have used the dtmf decoder. Is this a correct choice? I wi
The datasheet for the MT8870D shows you how to use it. A mic jack is not used.
I´m not sure if this could be a candidate for root of the problem, but I would not feel comfortable sharing the same crystal between 2 oscillators as done in the circuit at link above.
If i get your question right then you have tested two application sms alarm and dtmf controller with two different controller but with same single sim300 individually and when you combine the board means apply same logic to in single controller then you having problem? Correct me if am wrong.
Hi,My circuit diagram is a micrcontroller based one but my question and doubt is about analog circuit designing part,that is why I am posting this here I am trying to design a privacy protector for my home telephone,a simple device using Arduino and this device will connect just before my phone receiver,and when someone call me the device will a
Hello Friends, What I want to do is to transfer the data between my controller atmega8 and NOKIA 1100 by using its AUDIO port. I do not want to use the pop port(AT commands) to communicate with phone. I wanted to use audio port connection. I know that these phones can send dtmf tone to the audio port but i dont know how to feed the input data in
Hi all I am using the 9170 dtmf decoder chip. What i need to know? If I use 5.0V or 3.6V to power this chip. 1.What would the voltage and the output current be on pin 15 with a power supply of 5.0V. With or with a valid tone 2. What would the voltage and the output current be on pin 15 with a power supply 3.6V. With or with out a val
use BCD to S-seg and store data one by one
You are also running it below recommended supply voltage and without any supply decoupling capacitors. It may well simply 'crash' when the power is turned on. Brian.
You need to understand the overall function of the device to verify the schematic you have traced form the board. E.g. is the tone encoder a useless part because it's output is unconnected or did you simply miss a connection? If you know the purpose of the tone encoder, you can decide the point much better.
max 232 is mainly to convert voltage level from ttl to -9vdc / +9vdc and also curren amp to prevent damage for pic ic used hope it helps ziad
Perhaps we can agree on the point that the original question is too vague to suggest a specific solution. So a lot of processor based signal generation methods may be used. The said dtmf signal generation circuit feeds square waves for both tones to a passive RC filter. Of course the method can be extended to multiple phase shifted channels. No
Yes you can get informations about the input of the microcontroller on your phone. Read about sim300 or sim900, there are a lot of GSM modules which can be safely interfaced with the micro troller for calls and SMS.
A common method used for voice is spectrum inversion: the signal is shifted in frequency (DSB modulation with a carrier of frequency near the upper end of the voice band) and then filtered. Decription is performed in the same way. For dtmf, frequency translation can work as well: SSB with a low-frequency carrier. Do you need an all-analog solution,
Once i did this but i remember i use a control loop that was marginally stable, so then i had to just change some parameters so that the oscillation frequency where the dtmf ones. If you want to know how many point sdo you need, you should try matlab first, check this with a real telephone putting the mic on the computer speaker. Once you got a d
Hello I Have 2 Models Of Module Sim900A. First Module (S2-1040V-Z0958) is 64 MB Flash Version And Default Firmware Is :1137B12SIM900A64_ST Second Module (S2-1040V-Z095R) is 64 MB Flash Version And Default Firmware Is :1137B02SIM900A64_ST_ENHANCE since ENHANCE Firmware Support All Function (Decode dtmf , Jamming , ...) How I Can Read Firmware F
I wonder which RF module is prepared to transmit an analog baseband signal as the dtmf generator output? Likewise standard receiver modules have digital outputs not suitable to feed a dtmf decoder. In so far the sketched solution seems to be unusual and probably depends on specific module hardware. More often RC encoder/decoder chips are used wi
Output on pin 15 (StD) remains constant as soon as circuit is powered It should glow only momentarily when powered on and then each time new tone is fed to the circuit What this error means ? there may be a problem in your circuit, please check again pin StD: standby low(0) , if there dial so high(1) moment
Hi, we know that in a cell every key has high & low frequency tones(dtmf). can anybody tell, whether these low & high frequencies for each key are same all over the world or not.please explain.
Hi, can any body tell what is the need of 74LS04 IC in dtmf circuit. by using 74LS04, we are inverting the output of the dtmf & we will give it to micro controller. in the program again we are inverting the received input from the dtmf. so why we are using 74LS04 in cell phone operated land rover.
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Hello, I am trying to make a manual robotic car controlled by wireless remote and for the "wireless remote" I wanted to make a dual frequency remote not using dtmf but two RF modules with frequency 315 and 433 MHz and, HT 12D and HT 12E as decoder and encoder for the modules. Can anybody please help me with how can I mix these two frequencies a
Hi everyone, i am using proteus program to design circuit of mobile control robot but the problem, there is no chip of dtmf (CM8870 IC) decoder in the program.. what other choices i can use instead of that chip??!
You should be able to use RF as long as everybody is on a different frequency.
Before elaborating on how to do it, do you realize that using standard dtmf equipment you can only send at about 50 Bauds. It is VERY slow and can only send four bits per tone pair. Brian.
try or google
My total ckt is that i interface dtmf to micro-controller and then this controller to 3 phase motor, The application is that i want to operate motor by mobile so that it is usable in irrigation system for ON-OFF motor.
Hi Guys I am facing a very serious problem in case of GSM. Actually I have dtmf receiver of HOLTEK named HT9170 which I have interfaced with the GSM module named AT139D from the ATWIN company. The interfacing is as follows : The SPK+ pin of the AT139 has been interfaced with the pin 2 junction point as shown in the schematic via a cap
As I pointed out, the extra tones will not meet dtmf specification but this is inevitable when 'add on' tones are used. The original dtmf frequency pairs were chosen because they were statistically unlikely to occur together in a human voice although I personally know someone who's voice regularly operates a dtmf decoder! The frequency I (...)
Hi all. I need to detect dtmf Tone from a Voice call using SIMCOM SIM900D Module. I found document "SIM900_DDET_Application Note_V1.01". As per the document I executed command AT+DDET=1, but SIM900D reply is ERROR. Any advise please, why Module reply is ERROR or how to achieve this dtmf detection (without using external chip)? Regards.
hi, i looked a lot but i couldnt find anything.i want build a circuit for 4 channel phone line caller id. i have to use SM8223A decoder and atmel microcontroller. i build a circuit but micro cant receive all data,when all line is ringing micro just catch 3 line's caller id. im thinking make it with shift register for each line.4 shift registe
Some problems: 1. you do not need C1 and C2. 2. Check the crystal is 3.579MHz 3. R4 & R5 are shorted out 4. any reason why R4 and R5 are in parallel? Please tell us the component values you are using. Brian.
Hello sir what is the basic use of CM 8870 i.c. , what we call it ? Seems it is related to sound work , please explain in very short
Hi All! I want to design a Caller ID Telephone with a micro-controller. The uC should built-in FSK decoder, RTC, and 40x16 segment LCD driver. Please inform me which uC to use. The uC IC should be latest; it should be in manufacturing state, not phased out. It will be better that it is SMD IC with 128 pins or smaller for better soldering. Please
hello, i connect led between tip & ring 2 led's cathode at ring & led's anode at tip, when i pressed any key of cell phone keypad led glows, i think i successfully pass dtmf tone to MT8870, but not getting output, please suggest me some solution to solve these problem.
Did you check datasheet? StD Delayed Steering (Output). Presents a logic high when a received tone-pair has been registered and the output latch updated, returns to logic low when the voltage on St/GT falls below Vtst. EsT Early Steering (Output). Presents a logic high once the digital algorithm has detected a valid tone pair
I am using dtmf 8870 decoder for my project of cell phone based voting machine.The decoder is giving correct output whenever any input is being given by the phone(say, M1) connected to the circuit..but whenever i am giving any input from another mobile (say M2) through M1 it is not responding to the inputs other than 3,6,9,#.. what is the reaso
Hi, I need a complete project that will make use of a gsm to control 6 loads through dtmf. I will appreciate if the microcontroller is either AT89S52 or any PIC. Please include both the circuit diagram and the code thanks.
Hi, i need your help for my final year project and i'm running with very short time and even this project has to be submitted by this month so ... here are my few questions and doubts. 1) Can we use normal gamepad dual joystick interfaced with arduino and sending the direction movement through dtmf tones without using any keypads or dailpad? 2
hi i am trying to control devices using dtmf and 89s52, the code i wrote is #include /*MOTOR*/ sbit rm1 = P0^0; sbit rm2 = P0^1; sbit lm1 = P0^2; sbit lm2 = P0^3; /**/ sbit led1 = P1^0; sbit led2 = P1^1; sbit led3 = P1^2; sbit led4 = P1^3; unsigned char z=0,y=0,value=0,tem=0,hum=0,i=0,hum1,j=50,l=0; bit flag=0; un
Circuit is bad, what you plan with thise diodes on output ? See circuit examples : www.radiolocma
I have build the circuit for a dtmf bot using Atmega 16 and MT8870 dtmf decoder. I have checked the circuit and it is working perfectly when I connect the earphone jack from the circuit to the laptop and generate dtmf tones using a software for generating dtmf tones. But the problem occurred when instead of laptop, i (...)
Change the resitor back to 100K or the input gain will be very low. How are you measuring the crystal frequency? Where is the 33pF capacitor connected? Brian.
Its possible. Almost every GSM phone can generate dtmf codes. But why to use dtmf codes, you need to establish connection, you can use SMS control.
HI, I would like to add a delay to my pic project, This is a dtmf controller with a pre written assembly file, I'm not good with pic programming but can make changes to suit my needs, this however I cant get to work. I need help with a "I think delay code" but first let me tell you how this work. This code decode a dtmf signal from *11# t
Hello "anilzkf"; You don't need isis model for dtmf decoder. You can use some logicstate instead of dtmf decoder In other words, one logicstate for Q1, one logicstate for Q2, one logicstate for Q3, one logicstate for Q4 and one logicstate for StD you should make manual simulation for dtmf decoder in isis... it's very porterage work, but (...)