Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

transistor circuit with less batteries

Status
Not open for further replies.
Can you draw a circuit to teach us?

I am not a teacher for kids who know nothing about the basics of electronics.
You made your own SCR from two transistors but I don't know if it will work properly.
It can drive the buzzer by itself (if it matches the buzzer's current) without the transistor.
 
An SCR is made to latch when it has a small trigger current in its gate pin. Look at it in Google.

Wildebeest,
Your first transistor is missing a base current-limiting resistor so its base-emitter diode is probably burnt out.
There is no positive feedback in your circuit to make anything latch.

Would the current from a small electronic kitchen timer burn it out?
I've already managed to make it latch by using the other transistor, but I don't want to have to add another battery because of the transistor. Is there a way to rig a transistor so that the same battery that puts power through the base-emitter can sound the buzzer through the collector-emitter?
 
Would the current from a small electronic kitchen timer burn it out?
Without seeing the circuit of the timer i don't know how much current its output switch can pass.
You showed +1.5V and somebody else said the output from its speaker (beeper?). Does anybody know what is its output?

I've already managed to make it latch by using the other transistor, but I don't want to have to add another battery because of the transistor. Is there a way to rig a transistor so that the same battery that puts power through the base-emitter can sound the buzzer through the collector-emitter?
You do not need the extra output transistor if the transistors in the SCR can pass the current of the buzzer.

Before you showed two or three transistors connected wrong with extra batteries all over the place.
 
If the scr could handle the current this thread wouldnt be needed.
It couldnt handle the current so the transistor was added in.
 
The SCR latched when we used an LED instead of a buzzer, but then when we used a buzzer it wouldn't latch until we added the other transistor. Now it latches but the entire thing requires another battery bringing the total to: a kitchen timer, a battery for the other transistor, and a battery for the buzzer. It seems like I should be able to use the same battery to function the transistor and run through it to sound the buzzer.

I'll try to figure out the output from the timer, it shouldn't be much. I'm just running a couple wires from the speaker to the SCR to function it
 
An old fashioned mechanical buzzer draws 40mA which any little SCR can drive by itself.
A piezo beeper draws only 10mA or less so again any little SCR can drive it.
How much current does your buzzer need?

I do not know why you are using extra batteries when only a single battery is needed.

Since you showed a schematic that is completely different from whatever you connected then we are still just guessing about how you connected the parts.
 
How do we set it up with just one battery, that's what I've been asking about

It is a pretty big buzzer, not a smaller piezo buzzer
 
this is a drawing of exactly how we had it set up. We've done it with both a buzzer and an LED, it does what we want it to. We just want to lose one of the batteries. That's just a random resistor so we wouldn't burn out the LED. Once we get it set up for good we will replace the AA battery with the kitchen timer. We're using 9Vs because we have a lot of them and they're easy to get, again, our selection is EXTREMELY limited.
 

Attachments

  • transistor5.jpg
    transistor5.jpg
    37.1 KB · Views: 182
Your simple circuit does not need two 9V batteries.
The 9V battery that powers the load can also power the SCR and the transistor base resistor.
 
Last edited:
well the AA and/or kitchen timer will be powering the SCR, the other battery will be going through it, but we couldn't get it to power the transistor and the load. How do we set that up??
 
Last edited:
The problem is that your transistor is an emitter-follower that needs a base voltage swing of 9V to turn on the buzzer.
If the transistor is a common-emitter type then its base voltage is only 0.8V for it to turn on the buzzer that is from the positive supply to its collector.

But the SCR has a saturation voltage loss of about 0.8V so its gate signal must be at least 1.6V that you do not have.

The SCR can turn on a PNP common-emitter transistor from your low input voltage.
 
So we need a different type of transistor?
No.
You simply make your transistor circuit a common-emitter type (the LED and its resistor at the collector) instead of the emitter-follower type you have now.

(I dont know what the emitter-follower/ common-emitter terms mean)
Then you need to learn about simple transistor circuits.
 
Can you send us a drawing of how that should look? The only way we've been able to get that transistor to work is the way we have it set up now.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top