# How to connect a bulb and buzzer to be operated by one switch?

I want to make a simple circuit. I want to connect a bulb, buzzer and switch to a battery. About the size we all used in science at school. When the switch is on, I want the buzzer and bulb to work together. Do I need to use resistors and transistors? I have no idea. Help!

• "Work together" meaning turn on at the same time? That would be a parallel bulb+buzzer, with a series switch. Certainly no need for anything else. Commented Jun 28, 2016 at 18:19

You eventually need a lot more information in order to get an answer to this, but with the optimistic assumption that both the bulb and buzzer operate from the same voltage as the battery...

simulate this circuit – Schematic created using CircuitLab

• Best that can be done given the input data. If using an LED instead of a bulb you need a suitably rated device or a current limiting series resistor. Commented Jun 28, 2016 at 19:02

If you are using a readymade buzzer, there is no need to buy transistors etc (an internal oscillator, containing a coil, a transistor and few resistors already given in that buzzer), and the circuit you're trying to make, is very simple.

## Important notes

keep in mind, it contains 2 wires, of different nature (polarity). Red wire is positive input to buzzer, black-one is negative-input to buzzer.

LED vs Bulb ?

LED is a kind of semiconductor-diode that gives light when in forward bias. it is not bulb in true-sense. however, LEDs are now being used widely, since they're durable and cheap. But LEDs have polarity.

picture of an LED

symbol of LED

Anode is the positive input pole, and cathode is the negative input pole.

You could also use small bulbs (torch bulbs), but they are nowadays rare in market.

Bulbs need no specific polarity

but usually, torch-bulbs have one end at bottom, and other end at side, shown in the image. http://www.ekshiksha.org.in/images%20of%20Electricity_and_Circuits_VI/3.png

bulb symbol

Batteries

You could take 1.5Volt or 3Volt batteries in different numbers, all in series combination, to adjust voltage. usually an LED cuts-open before 7.5V or 12V, however in a series or parallel combination , the LED gets lesser voltage from the same source, so needs quite higher voltage. A readymade piezo-buzzer is usually loud enough,. so I guess three or four 1.5V batteries maybe enough.

• @ Passerby Thanks so much for adjustment of image size. how to do that?
– user107801
Commented Jun 29, 2016 at 3:32
• I had done that, but there is not enough juice for the light. It slowly turns on, but not bright at all. The bell works as expected. Should I change the transformer (higher voltage)? The original circuit was just for the bell, my friend is deaf and cannot hear the bell. Thank you for any suggestion. Commented Jan 16, 2018 at 16:16
• @user2060451 You are using a "battery", then why you would need any transformer? "Slowly turns on" sounds like you are using some-other parts that you have not mentioned in original post.
– user107801
Commented Mar 25, 2018 at 13:24
• in my case, it is a house bell. I would like to add a light bulb for a hearing-impaired person. I put them in line and parallel. Does not work. I believe I need to get a higher transformer in order to have more power. I didn't want to deal with the transformer though.... @always confused Commented May 31, 2018 at 18:34
• @user2060451 Please specify all the changes to your question. As well as SE is not designed to be a discussion forum but a site for permanent preservation of question and answer. So a frequent change in the original meaning of a question can draw objection from moderators. Okay I'll be update my answer few weeks latter b'coz I'm extremely busy with a competitive exam. In the mean time you could discuss your queries in chat room (chat.stackexchange.com/rooms/15/electrical-engineering), a friendly place.
– user107801
Commented Jun 11, 2018 at 9:57