DTMF receiver problem

Status
Not open for further replies.
A

amitpatel711

New Member
I am making a circuit of Tele Remote Control but unable to generate DTMF codes at the remote end from telephone or may be some other problem.. Can anyone suggest me how to test DTMF receiver IC KT3170.. I am having problem to generate the BCD codes from this IC.. If anyone knows please help me out..... Thanks..
 
Last edited:
You mean, unable to decode DTMF tones, yes? supply a schematic of what you have and perhaps we can help...
 
I have made connections as seen in this document and used KT3170 instead of CM8870 but still when I switch on the remote circuit the Relay gets On directy and even if i call the remote end there is no response of the relay(neither gets on nor gets off)
 

Attachments

  • Cell Phone Controlled Door Latch.doc
    98.5 KB · Views: 542
Last edited:
Your telco interface does not look right. That 1 Meg seems awful large for feeback.
Compare your drawing to this data sheet.
http://www.datasheetcatalog.org/datasheet/SamsungElectronic/mXuusvq.pdf

One more thing to add. I can't tell from your input config if you intended for single ended input or differential as your drawing matches neither. I think you want differential unless you are using a diff to single conversion not shown on your schema.
 
Last edited:
You can use your PC to generate test tones. Google for "DTMF Tones sound card" to find some free software to generate DTMF.
 
Mikebits said:
The part he is using is a DTMF decoder not a generator.
Click to expand...


Yes, of course, but our OP asked for ideas on how to test his decoder. One would need a source of DTMF tones to do this, hence my suggestion.

However, after reading his attachment, it seems he already has such a source.


The only other comment I can offer after reviewing the schematic is that it might be wise to include a 10 uF bypass cap from pin 18 to gnd, but this would not explain the symptom that all outputs are high when power is applied. In situations like this, it is best to do a detailed check of every wire connection to see if all is connected as the schematic shows.


Edit: oops, looks like you figured it out while I was typing, Mike.
 
Last edited:
Friends u're right but u know what wherever I searched for this circuit the connections are same everywhere whether it is CM8870, MT8870 or KT3170.. And one more thing u can go through this link in which a video shows how the circuit works.. https://www.radiolocman.com/shem/schematics.html?id=35267 I think in my circuit current gets bypassed and thats why the relay gets on automatically.. And Radioron I think its not practical to gnd cap from pin 18 because IC gets +5V operating voltage from the same pin only.. isnt it???
 
Last edited:
The bypass capacitor for an IC is always wired in parallel with the ic power supply, which means it connects from +5V to ground immediately beside the ic.
 
Hi amipatel711,

I am finding the same results with the outputs being high (relay on) upon power up, and can't seem to make it work any differently even when changing the input resistor values as shown on the 8870 data sheet.

If you have solved the problem you are having, please pass it along as to what you did.

I tried to send a message to the writer of that project, but haven't heard back as of yet.
 
Last edited:
Status
Not open for further replies.

Similar threads

Positive / Negative voltage circuit problem
2
Replies
20
Views
5K
ZipZapOuch
G
  • Question
Impedence mismatch problem in audio project
Replies
12
Views
3K
audioguru
T
  • Question
Power problems
Replies
11
Views
2K
texas dave
T
Circuit Problem
2
Replies
21
Views
5K
Lone_Star_Astro(!)
S
  • Question
stereo to mono problem
4 5 6
Replies
100
Views
26K
audioguru
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…