Our DTMF decoder kit has 6 NPN open collector darlington outputs that can be switched on/off remotely with or without a 4 digit security code. The decoder also has a TX keying output to key a transmitter for transponding a morse confirmation. An audio output is included for the morse audio tones. The PCB has been designed to allow 3 input configurations - unbalanced audio, an electret microphone or balance audio to be connected.

An alternative option is to use the kit as a DTMF to PC interface allowing DTMF tones to be displayed in say Hyperterminal (see below).

To turn on/off an output send the decoder it's ID followed by the output number and * for ON or # for OFF e.g. 12341* turns on output 1 and 12342# turns off output 2 etc.

To toggle an output send e.g. 12341A and the state of the output will be changed to the opposite of it's previous state - the morse transpond will be confirmation of the new state. To pulse an output send e.g. 12341B and the output will turn on for 0.5 seconds - the morse transpond will be e.g. 1P.

* You can now use 9 for A and 8 for B on the latest firmware.

For confirmation of the desired switching of an output the decoder will key a Transmitter and respond in morse code, e.g turning on output 1 will respond as 1 ON in morse, and turning off output 2 will respond as 2 OFF.  As there are only 6 digits and 3 letters to learn, morse shouldn't put you off.  There is a 2 second transpond delay followed by a 400ms link establishment delay to allow for CTCSS (if used).

Sending the turn off code for the dummy output zero e.g. 12340# will transpond _._._ OFF but won't affect any outputs. This is useful for checking if in radio range.

The 4 digit security ID can be changed by simply fitting a jumper to CN7, powering up the decoder and sending it a new 4 digit ID, then remove power, remove jumper and power-up and the new ID is set.  If no ID is required then simply program the ID as 0000 and on next power-up no ID will be needed and e.g. 1* will turn on output 1.

There is an added feature on the current DTMF decoder kits, the ability to turn off the morse transpond has been added.  When setting the 4 digit identity add a fifth digit as 9 and the morse transpond will be turned off.  Any other character in the fifth position turns the morse transpond on. When supplied the identity is supplied as 1234 and the fifth digit is set as 0. You do not need to program the fifth digit if transpond is desired, the fifth digit is not used as part of the identity.

If using the kit for DTMF to serial - program the ID as 2320 and on next power-up decoded DTMF tones will be output as RS232 (4800 baud 8N1) compatible serial on the TX keying output, (fit the pull-up resistor R12 for this use).

The PCB is a high quality double sided PTH (plated through hole) 1.6mm FR4 (Fiberglass) board 64 x 38mm in size.

A 4 pin programming header is also provided to allow in-circuit re-programming of the PIC.

All parts shown in the assembled photo are included as well as some extras for alternative input configuration.

A pdf circuit diagram may be viewed here.

and a component list may be viewed here.

Click here for application notes.

Click here for HT9170 datasheet

As an example if using as a DTMF code lock, use a mobile phone's keypad tones and use the microphone option for pick up.

Our DTMF display can display up to 16 characters (8 per line). The display can be cleared by a button (not supplied) or can auto clear on a timed basis from receipt of the last character.

The input circuit is the same as the DTMF decoder kit above, therefore it can be configured for unbalanced, balanced or microphone input.  When an electret microphone is connected it can pick-up tones from a speaker phone a few inches away.

Connecting a momentary on button between the button input pin and 0V pin clears the display on pressing, however holding the button during power-up enables the timed reset mode. In timed reset mode the display is automatically cleared 10 seconds after the last character is received.

Complete kit of parts including pre-programmed PIC micro, gold plated PCB, LCD display, nuts bolts and spacers.

Runs from 7 to 16V DC at a few mA.

This kit is now shipped with a backlit display, the backlight requires 4.05V at 60mA (e.g. 5V via a 16 ohm resistor).  The backlight is not connected in any way to the decoder PCB.

Click here for circuit diagram

Click here for HT9170 datasheet

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