×
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

Lightbulb choosing circuit

Lightbulb choosing circuit

Lightbulb choosing circuit

(OP)
I apologize in advance if this is not the place for this question. I have zero experience with circuits and don't even know what terms to search for.

I have a bug zapper that takes two bulbs and when the switch is turned on, both of the bulbs turn on. It is not necessary to have both on at the same time though, as one bulb is bright enough to attract flies and other winged nuisances. Those bulbs can be expensive so since one is good enough, I only use one at a time. It would be nice to have that second bulb as a backup though. That way there is no downtime when a bulb burns out.

Is there a simple circuit that exists that can do this:
  • If both bulbs work, power bulb 1
  • If bulb 1 is burned out, power bulb 2
  • If bulb 2 is burned out, power bulb 1
It would be a bonus if there was an indicator that showed whether bulb 2 was burned out or not, but that might be outside the realm of "simple" and anything outside of simple might get too expensive to be worth it, I'm not sure. Or maybe there is an even better alternative that I haven't thought of.

RE: Lightbulb choosing circuit

Put a dusk-to-dawn controller on the second bulb with the detector aimed at the first bulb.

RE: Lightbulb choosing circuit

Add a single-pole double-throw switch ahead of the bulbs that directs the power to either one bulb or the other. Simple, not too expensive.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Lightbulb choosing circuit

Can you just disconnect the second bulb? Cost is nothing if it works.

RE: Lightbulb choosing circuit

Power the 2nd lamp through an normally-closed contact of a relay, power the relay coil from a current switch sensing the 1st lamp. When the 1st lamp is running the current switch is closed, powering the relay and opening the NC contact. When the 1st lamp burns out the current switch opens, closing the NC contact and thusly turning on the 2nd lamp.

EDIT: I just realized if you could get a normally-closed current switch you could eliminate the relay. Not sure how common those are though.

RE: Lightbulb choosing circuit

I like this last one better than mine . . . the OP would have to mark the outside of the unit, though, to denote the bulbs as one and two since the condition

Quote:

If bulb 2 is burned out, power bulb 1

would not be met.

Nevertheless, minor detail.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Lightbulb choosing circuit

(OP)
Thanks for everyone's replies. I appreciate your time. I'll try the relay option and see how it goes.

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