Relay control circuit.

[6]

Hi all,
I am new to the group,


I just bought a ramsey TT7 DTMF tone decoder and would like to use all
16 outputs to drive 12V relays.
It has been years since I desigined a circuit so I have forgotten if I
need a NPN or PNP transistor.

The output from the TT7 goes low or to Gnd.

The coli resisitance is 120 ohms.

Thanks for any help.

 

[John Popelish]

Hi all,
I am new to the group,

I just bought a ramsey TT7 DTMF tone decoder and would like to use all
16 outputs to drive 12V relays.
It has been years since I desigined a circuit so I have forgotten if I
need a NPN or PNP transistor.

The output from the TT7 goes low or to Gnd.

I take it this is the decode=true state. What is the decode false
state?

 

[Si Ballenger]

Hi all,
I am new to the group,


I just bought a ramsey TT7 DTMF tone decoder and would like to use all
16 outputs to drive 12V relays.
It has been years since I desigined a circuit so I have forgotten if I
need a NPN or PNP transistor.

The output from the TT7 goes low or to Gnd.

The coli resisitance is 120 ohms.

Thanks for any help.

I've made the "sweet 16 DTMF" decoder, which should be sinilar to
yours. You should be able to use one of the below parallel port
relay boards if desire (save some time on setup), just
substituting the output of your decoder chip for the parallel
port pin intputs.

http://electronickits.com/kit/complete/elec/ck1601.htm
http://www.qkits.com/serv/qkits/diy/pages/QK74A.asp

 

[Tam/WB2TT]

Hi all,
I am new to the group,


I just bought a ramsey TT7 DTMF tone decoder and would like to use all
16 outputs to drive 12V relays.
It has been years since I desigined a circuit so I have forgotten if I
need a NPN or PNP transistor.

The output from the TT7 goes low or to Gnd.

The coli resisitance is 120 ohms.

How sure are you that these are 12V relays. Unless they are really big, this
seems like a very low resistance.

Tam/WB2TT

 

[CFoley1064]

Subject: Relay control circuit.

From: 6 [email protected]
Date: 5/30/2004 1:03 PM Central Standard Time
Message-id: <[email protected]>

Hi all,
I am new to the group,


I just bought a ramsey TT7 DTMF tone decoder and would like to use all
16 outputs to drive 12V relays.
It has been years since I desigined a circuit so I have forgotten if I
need a NPN or PNP transistor.

The output from the TT7 goes low or to Gnd.

The coli resisitance is 120 ohms.

Thanks for any help.

If you want to do it that way, you will need PNP transistors. Since the output
of the TT7 is current sinking when true, you will want a transistor that will
turn on when current is drawn from the base -- in other words, a PNP. Each of
your outputs should look like this (view in fixed font or M$ Notepad):

VCC VCC
+ +
| |
| |
.-. |
1K| | |
| | |
TT7 Output '-' |
___ | |<
o-|___|-o-| 2N3906
1K |\
|
.--o
| |
| C| RY1
1N4002- C| 120 Ohms
^ C|
| |
| |
======
GNDGND

created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Don't forget the diode -- it absorbs the inductive kick when the relay turns
off, protecting the transistor.

Good luck
Chris

 

[Tam/WB2TT]

If you want to do it that way, you will need PNP transistors. Since the output
of the TT7 is current sinking when true, you will want a transistor that will
turn on when current is drawn from the base -- in other words, a PNP. Each of
your outputs should look like this (view in fixed font or M$ Notepad):

VCC VCC
+ +
| |
| |
.-. |
1K| | |
| | |
TT7 Output '-' |
___ | |<
o-|___|-o-| 2N3906
1K |\
|
.--o
| |
| C| RY1
1N4002- C| 120 Ohms
^ C|
| |
| |
======
GNDGND

created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Don't forget the diode -- it absorbs the inductive kick when the relay turns
off, protecting the transistor.

Good luck
Chris

That won't work if he truly has 12V relays, unless the decoder is also
running off 12V. BTW 120 Ohm DIP relays are 5V.

Tam