×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Frequency Limit Relay

Frequency Limit Relay

Frequency Limit Relay

(OP)
Hi,

I'm trying to find a relay that will open (or close) after a certain frequency is achieved.  Ideally the relay would be adjustable to allow for fine tuning but this is not necessary.  I'm looking to find a relay like this or I will build my own if need be!!

I have a signal from a VSS that is 0-4.5V (DC).  The frequency from this switch comes in a squarewave and varies with speed.  When the frequency gets above 30Hz I want the relay to open.

Any ideas where to find a relay like this??  Thanks!!

RE: Frequency Limit Relay

your concept can be done without to much trouble, but what you need to look into is a control for the relay, to the best of my knowledge no relay will do this on its own.
I would suggest off of the top of my head a frequency to voltage converter, hooked to a simple comparater circuit who's output drives the relay.
this would require in total
2ic's (1 op amp, 1 freq to vltge conv)
1 normaly closed relay
and a few resistors to set the voltages.

make sure that the op amp is capable of sourcing the current required to operate the relay you select.

hope this helps.
p.s. there is most likely a device that would make a simpler circuit than this, but I know this one will work.

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!


Resources