×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Simple Switch
3

Simple Switch

Simple Switch

(OP)
I want to use a 2N2222 transistor to switch on and of Christmas light using a microcontroller. The collector and emitter of the transistor is in series with the Christmas lights wire. The base of the transistor is connected to a 5 Volt output of a microcontroller. My question is do I need a common ground? If so where would be the best place for it? I tried to hook up the circuit but nothing happens. Help!!!

RE: Simple Switch

You should tried to place a resistor on the emitter of your transistor and your output will be between the emitter and the resistor. I will tried to have a common ground between the micro controller and the christmas light circuits. I am still a students but give it a shot...hope it will help.

RE: Simple Switch

2
A good circuit would be a transistor that drives a relay. Then the relay contacts can be placed in series with the Christmas lights. Connect the output of the microcontroller with the base of the transistor through a 1-5k ohm resistor, ground the emmiter and place the relay coil between the colector of the transistor and the 5 volts power supply. Don't forget to place a diode (1N4001 or 1N4148) across the relay coil to protect the transistor from back EMF.
GOod luck !

RE: Simple Switch

The relay suggested is a good idea. Remember you are controlling AC with the output of your transistor. To get around the idea of a common ground, use an opto isolator or simply power the mechanical relay with the microcontroller output. Either of these methods will eliminate the need for a common ground and might save your microcontoller, too!

RE: Simple Switch

The simple method is to use a SSR. These can come in a 5V input to switch on/off an AC signal. Check in the DigiKey catalog or Newark's catalog for the part number and costing.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close