teleremote....help on relay...

[ajaleelp]

hi friends..
i am making a project on teleremote..remot control thru telehphone...i fineshed doing the circuit....prob is my relay clicks(get's energized) straight after connecting power supply..it is supposed to click only when an flip flop ic sends signal thru a transistor....plz help.....
tell me how to deduce the emitter and collector of a trans. also...
regards..
AJP

 

[k7elp60]

It would help if you can post the schematic, but from what you said I am guessing that the F/F does not have power up clear and is going to an relay on state when power is applied.

 

[ajaleelp]

thanks for ur concern....
the diagram was got from the following link
**broken link removed**
plz check it and guide me more...i am a newbie...
i couldn't actually understand what u meant by ur reply...could u simplify it..??
regards
AJP

 

[ajaleelp]

sorry..but i forgot to tell that i have used an 8870 ic instead of the given kt 3170 since i found it as a subs. from the net...
also...i strongly beleive the prob is with the transistors...plz check...

 

[k7elp60]

The schematic that you are referring to is not to clear, but I believe the F/F are CD4013's. If so they are D type F/F's and they are configured to the latching mode that is for each clock pulse the Q output changes state and alternates between 0 and 1 logic levels. The IC also has set and reset modes. These determine the logic state of Q and the Q not, outputs.
From what I can see the set and reset lines are grounded. If you ground pins 6, 8 (set) and connect pins 4,10(reset) together. Connect a 0.1uF capacitor from pins 4,10 to the + supply rail, also pin 14, and connect a 10K resistor from pins 4,10 to ground or pin 7. When power is applied the Q output will be 0 and the relays will be off. The next clock pulse to the F/F will turn the relay on, the next one after that will turn the relay off.

There may be a problem with the transistors that drive the relays, I am not sure as I cannot read the value of the resistor connected to the base or can I tell the transitor number. The circuit of the transistors and relays look fine thou. I would say that the resistor on the base should be a value such that the F/F does not have to provide more than a few milliamps of base current thou.

 

[Sebi]

I agree with k7elp60.
Anyway, this circuit cannot work on all countryes. In my country can't receive DTMF signals until ringing. In this case need additonal ringdetector circuit to activate RL1 (make off-hook state).

 

[ajaleelp]

k7elp60...
firstly thanks for ur sincere concern...well...the f/f's are cd4013's...u told the diagram ain't clear..i think u had not maximized it's size to c in ur explorer window..i get the schematic almost filled in my 17" monitor...plz try ....

i read ur instruction abt making the relays off when power is applied...here's vat i understood..plz correct me if i am wrong somewhere...

1) ground 6,8
2) connect 4,10,14 thru a 0.1uf capacitor to + line...
3) connect 4,10 to ground or pin 7 thru 10k resistor

am i correct...
one more thing...i had ordered the board to be drawn for me...in the PCB which i got 14 was connected to ground...is this a mistake?? it was not connected to + as shown in schematic..so i cut the connec and made and external link from 14 to +....was i wrong???

the transistors..the resistor connected to them are of 100 ohms...the transistor no is 2N2222A...i didnt get ur suggestion of maintaing the resistor value to help the f/f...

plz help me urgently as i am already out of my given time...
expecting ur continued support...
regards
AJP...
(((((((((((IF U WANT MORE INFO ON HOW THE PROJECT WORKS :........

Here is a teleremote circuit which enables switching 'on' and 'off' of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.
The circuit described here can be used to switch up to nine appliances (corresponding to the digits 1 through 9 of the telephone key-pad). The DTMF signals on telephone instrument are used as control signals. The digit '0' in DTMF mode is used to toggle between the appliance mode and normal telephone operation mode. Thus the telephone can be used to switch on or switch off the appliances also while being used for normal conversation.
The circuit uses IC KT3170 (DTMF-to-BCD converter), 74154 (4-to-16-line demult-iplexer), and five CD4013 (D flip-flop) ICs. The working of the circuit is as follows.
Once a call is established (after hearing ring-back tone), dial '0' in DTMF mode. IC1 decodes this as '1010,' which is further demultiplexed by IC2 as output O10 (at pin 11) of IC2 (74154). The active low output of IC2, after inversion by an inverter gate of IC3 (CD4049), becomes logic 1. This is used to toggle flip-flop-1 (F/F-1) and relay RL1 is energised. Relay RL1 has two changeover contacts, RL1(a) and RL1(b). The energised RL1(a) contacts provide a 220-ohm loop across the telephone line while RL1(b) contacts inject a 10kHz tone on the line, which indicates to the caller that appliance mode has been selected. The 220-ohm loop on telephone line disconnects the ringer from the telephone line in the exchange. The line is now connected for appliance mode of operation.
If digit '0' is not dialed (in DTMF) after establishing the call, the ring continues and the telephone can be used for normal conversation. After selection of the appliance mode of operation, if digit '1' is dialed, it is decoded by IC1 and its output is '0001'. This BCD code is then demultiplexed by 4-to-16-line demultiplexer IC2 whose corresponding output, after inversion by a CD4049 inverter gate, goes to logic 1 state. This pulse toggles the corresponding flip-flop to alternate state. The flip-flop output is used to drive a relay (RL2) which can switch on or switch off the appliance connected through its contacts. By dialing other digits in a similar way, other appliances can also be switched 'on' or 'off.'
Once the switching operation is over, the 220-ohm loop resistance and 10kHz tone needs to be removed from the telephone line. To achieve this, digit '0' (in DTMF mode) is dialed again to toggle flip-flop-1 to de-energise relay RL1, which terminates the loop on line and the 10kHz tone is also disconnected. The telephone line is thus again set free to receive normal calls.This circuit is to be connected in parallel to the telephone instrument
)))))))))))
regards

 

[ajaleelp]

SEBI...
thanks for the warning sebi..
i had come across the prob of dtmf support previously...i tried using a dtmf dialing software from my pc..it emitted dtmf signals to my phone microphone and it worked.i could make calls..does this prove my country's dtmf support available....or is there anyother way?? if i have to use the ring detector plzz send me the schematic...
regards...
AJP