Hello
i want to ask about the circuit attached .
1- what transistor to replace instead of SL100 ? because i couldn't find it in my country .
2- what is the program that i can do a simulation to the circuit ?
3-if am going to connected to arduino so i can send a sms using GSM shield , how i can do it ?

thank you

 

Just about any NPN transistor or N channel MOSFET will work. It needs to be rated to 10V and at least 200mA. I'd use a MOSFET such as IRF540, which I have on hand, but that is overkill.

Many here use LTspice for simulation. It's free and quite useful.

 

Bfy50/51/52, 2n2222

 

Can you help me with the simulation?
I tried to take pin 4 high and low as a gas sensor , when i put it high the LED is working but the speaker or the buzzer doesn't work .

 

I tried to simulate it using Proteus 8 Professional , the LED is working when pin 4 is high but the speaker doesn't .
I didn't find SL100 so i used BFY50 .
what is wrong with it?

 

the LED is working when pin 4 is high but the speaker doesn't

What do you mean by 'working'? Is the LED being pulsed at ~ 500Hz-1kHz, or is it on constantly? What is the speaker impedance?

 

Cant help you with software matey, only the real thing will do....

 

What do you mean by 'working'? Is the LED being pulsed at ~ 500Hz-1kHz, or is it on constantly? What is the speaker impedance?

the LED is being pulsed , and the speaker impedance is 8 ohms.

 

If the LED is pulsing and R1, Q1 and the speaker are connected correctly then the speaker should make some sound.

 

Double check you have the right pin out for the transistor.

You should also be able to hear something, I believe, by connecting the speaker to the signal currently going to the base of the transistor. It will be quiet but I would expect to hear something.