Basic interconnect IC

[Charlie123]

Hello everyone,

I'm working on a project and I'm wondering how to connect the DTMF receiver (MT8870D) without a DTMF generator(5089).

As per user Ericgibbs he ref another user (mdanh2002) to the below link,
https://www.boondog.com/tutorials/dtmf/dtmf.htm

Schematic 1; DTMF Generator, output should be connected to the input(tone in) of Shematic 2: DTMF receiver to setup an operational circuit.

I'm wondering if I absolutely need a DTMF generator as I want to use a remote phone to control an in/house device.

Where should I connect this DTMF receiver if I don't need a dtmf generator?

Is someone can provide me a clear picture on how I can setup such circuit.

Brgds

 

[ericgibbs]

hi charlie,

Are you wanting to use the remote phone keypad to generate the DTMF tones?
[you can/could purchase small handheld tone generators]

If so, you don't need the tone generator.

Your require the DTMF receiver/decoder ic.

How many home devices do you want to control?

EDIT: for one or two tone decode, using 'agu' cct, you could consider a NE567N
Look at this for ref, it has sound files of the 'standard' tones, you can download and use for testing.

https://en.wikipedia.org/wiki/DTMF

 

[audioguru]

You need to power the phone with a power supply in series with a load resistor (620 ohms). Try 12VDC. Then the DTMF will appear across the load resistor.

Use a shielded audio cable or convert the phone circuit and the DTMF receiver input to the to a balanced signalling method.

 

[Charlie123]

Hello Ericgibbs and Audioguru,

Ericgibbs;

--------------------------------------------------------------------------
Are you wanting to use the remote phone keypad to generate the DTMF tones?
[you can/could purchase small handheld tone generators]
--------------------------------------------------------------------------

Yes, I'm using remote keypad.

I will really need MT8870D IC, as per what I read, it seems that I can attached the MT8870D(tone receiver) to the tips and rings as I don't need a tone generator.

I looked MT8870D datasheet and it seems that I can connect the tips and rings of the input, I guess that this is pin: IN + and IN - of this MT8870D datasheet(page 7 figure 6 ), Am I correct ? , see below;

**broken link removed**

Should I use figure 6 (page 7, Differential input configuration) or figure 9 (page 9 single ended input configuration ) ? Can you tell me briefly what the difference are btwn these to setup ?

Do you remember, you provided me a shematic few days ago : (3 rings to 1 pulse output) is this builted according to 90AC volts? If this is the case, I guess I can take the left part of this cct and connect it to MT8870D for protection purpose ?

What do you suggest ?

Hello Audioguru,

I would like to avoid power supply, as per what I read, If I answer the call, the Voltage will drop to 5 to 15 DC, than if I take this power to supply my MT8870D, I won't need any other power source. I guess you are providing me this info for testing purposes ?


Brgds/Charlie123

 

[audioguru]

You need a 1:1 600 ohms transformer between tip and ring of the phone line then protection diodes across the secondary. Use the differential circuit or the single ended circuit to connect the MT8870 to the secondary of the transformer.

The MT8870 is supposed to have a regulated 5V supply between 4.75V and 5.25V. Anything more than 7V will fry it.

 

[ericgibbs]

>> Do you remember, you provided me a shematic few days ago : (3 rings to 1 pulse output) is this builted according to 90AC volts? If this is the case, I guess I can take the left part of this cct and connect it to MT8870D for protection purpose ?

I recommended that you construct the lefthalf of the circuit, upto and including the 10K0.
Have you done that and measured the Vdc across the 10K0, what is it?
The FWB rectifier in the original circuit is chosen for a phone line voltage of 40 to 50Volts,
if your local phone voltage is higher, you must chose a suitable voltage rating for the FWB.

>> I can take the left part of this cct and connect it to MT8870D for protection purpose ?
I dont follow what you are saying???

 

[Charlie123]

Hello Audioguru and Ericgibbs,

Ericgibbs, as per your last response;

I recommended that you construct the lefthalf of the circuit, upto and including the 10K0. Have you done that and measured the Vdc across the 10K0, what is it? The FWB rectifier in the original circuit is chosen for a phone line voltage of 40 to 50Volts, if your local phone voltage is higher, you must chose a suitable voltage rating for the FWB.

10K you mean R3 (the one in // of C2) ?

I did not take any measure as I'm still waiting some component to start to built my entire project. But I verified Bell standard by calling their techs, and the voltage is aprox. 90VAC (did even get a shock once ringing and that is pretty close to the regular 110 v from eletric stream : ), the Bell Canada voltage standard is 90 to 110 VAC on ringing I can ensure that to you. What should be the value at 10K position ? By wich values/type make and models you suggest me replace your 1 amp 100V FWB to fit w/ a 90 to 110 VAC ringing cct ?


>> I can take the left part of this cct and connect it to MT8870D for protection purpose ?
I dont follow what you are saying???

Sorry Eric I was not very clear, I need to protect an IC DTMF receiver(MT8870D) and to place it in // of my phone; I mean to connect GS pin of MT8870D to the Tips and IN- of MT8870D to the ring so this way, I would be able to grab a remote DTMF signal with MT8870D (DTMF receiver) once OFF HOOK position. But if I do so, I will need a protection for the ringing part, the 90VAC will blast my IC if no protection, so I decided to take the left part of your cicuit to protect my MT8870D do you suggest such setup? Or should I use Audioguru solution(w/ a transformer and a diode)? His solution complicate things I guess due it is taking one transformer and with your solution it seems that I don't need this device.

Thanks Audioguru, I will wait Ericgibbs reply before deciding what is the most appropriate for my project.

Brgds/Charlie

 

[Charlie123]

Hello Audioguru and Ericgibbs,

Ericgibbs, as per your last response;

I recommended that you construct the lefthalf of the circuit, upto and including the 10K0. Have you done that and measured the Vdc across the 10K0, what is it? The FWB rectifier in the original circuit is chosen for a phone line voltage of 40 to 50Volts, if your local phone voltage is higher, you must chose a suitable voltage rating for the FWB.

10K you mean R3 (the one in // of C2) ?

I did not take any measure as I'm still waiting some component to start to built my entire project. But I verified Bell standard by calling their techs, and the voltage is aprox. 90VAC (did even get a shock once ringing and that is pretty close to the regular 110 v from eletric stream : ), the Bell Canada voltage standard is 90 to 110 VAC on ringing I can ensure that to you. What should be the value at 10K position ? By wich values/type make and models you suggest me replace your 1 amp 100V FWB to fit w/ a 90 to 110 VAC ringing cct ?


>> I can take the left part of this cct and connect it to MT8870D for protection purpose ?
I dont follow what you are saying???

Sorry Eric I was not very clear, I need to protect an IC DTMF receiver(MT8870D) and to place it in // of my phone; I mean to connect GS pin of MT8870D to the Tips and IN- of MT8870D to the ring so this way, I would be able to grab a remote DTMF signal with MT8870D (DTMF receiver) once OFF HOOK position. But if I do so, I will need a protection for the ringing part, the 90VAC will blast my IC if no protection, so I decided to take the left part of your cicuit to protect my MT8870D do you suggest such setup? Or should I use Audioguru solution(w/ a transformer and a diode)? His solution complicate things I guess due it is taking one transformer and with your solution it seems that I don't need this device.

Thanks Audioguru, I will wait Ericgibbs reply before deciding what is the most appropriate for my project.

Brgds/Charlie