I am making a circuit in which I need your help. can you help me please...?

[shaheen]

Hi,
Friends I am making a circuit in which I need such a functionality, when i press a push button(to give 5V high pulse), it continuously turn ON the LED (even i release the push button). and to turn OFF that LED, i push another push button.
Someone told me to use an IC (BT137). This IC has 3 pins T1, T2 and G. when i give the high pulse(with the help of push button) at 'G', it short circuit T1 and T2. i use T2 as input(5V) and T1 as output. i connected the LED between T1 and ground. To turn OFF LED i short circuit T1 and T2. But this circuit is not working.
I need this circuit urgently. can anyone help me please... i will be thankful to u.

LED glows as long as i press the push button, as i release the push button it (LED) turn off. but i need, when i pres the push button it continuously glows.

the IC which I used is BT137 600E.
can anyone send me circuit diagram (with component values ) for this task?
I will be very thankful to you...

 

[(*steve*)]

What you want is a bistable with the switches changing the state.

Here is the simplest circuit I can come up with to do what you want. Be aware that this is a CMOS chip which requires careful handling and the other inputs for the unused gates should be tied to ground.

There are several options you can use in place of the 40106.

they include: 74C14, 74HC14, 40106, 14584.

Some (typically those starting with 74) require an exactly 5V supply. The 40106 and 14584 allow supplies between 3 and 15 (or more) volts. They are ideal for battery powered circuits due to the flexibility in supply voltage.

The BT137 600E is not an IC, it is a MOSFET.

It is theoretically possible to make it work kinda like a bistable as the gate has capacitance that can be charged but I wouldn't design a circuit like that as it leaves the gate in a very unprotected and easily damaged position.

edit: sorry, the BT137 is a Triac (what was I thinking). Whilst you could use 2 pushbuttons to do what you describe with a triac, you have to be sure that the load you're driving draws sufficient current to keep the triac conducting. To use a triac, one button is connected from the anode to the gate (via a resistor) and the other a normally closed switch is in series with the load. If this is what you're doing and the LED won't stay turned on, then the series resistor is too low. You need enough current to keep the triac turned on, so reduce the resistor, but not so much to allow more current than the LED is capable of handling.

 

[Resqueline]

The triac should work if you provide it with enough current like steve says. If you need to make it work with less current then you should try using a sensitive-gate thyristor.

 

[shaheen]

Thanks steve, Actually the circuit which i want to make is that, I need 2 push buttons(P1 and P2) and 2 LED's(green and red). when I press the push button P1, Green LED turn ON continuously(until I press P2) and when I press the push button P2, Red LED turn ON continuously and Green LED turn OFF. Only one LED glows at a time.

 

[(*steve*)]

OK, here are some possible solutions:

This one uses 2 triacs in 2 totally separate circuits. You require buttons which are DPDT to allow each button to be used as a NO on one circuit and NC on the other. Neither LED is lit on power on.

This is slightly trickier in that a capacitor is used to turn off the turned on triac when the other one is triggered. The issue is if both buttons are pressed, both LEDs will iluminate and you have to remove power to turn them off. In addition the starting condition is neither LED lit.

This is a modification of what I suggested first. One LED is always lit. The one lit on power on is random (or at least indeterminate). If both buttons are pressed the LED corresponding to the first button is lit. On release, the LED corresponding to the last released remains lit.

 

[shaheen]

Thanks Steve, its working.
GOD Bless You...

 

[(*steve*)]

Glad to help. Which circuit did you go for?

 

[shaheen]

The last one. In which 40106 is used.

 

[(*steve*)]

Excellent, by the way, your next question has been movet to a new thread.

 

[shaheen]

Thanks for your help