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

555 help

555 help

555 help

I Bought some zsct1555 timer chips from Digi-key and can't seem to get them to work properly. They are made by Zetex for single cell opperation(down to .9v I believe). They are basically the same as the 555 but lower voltages and have a slightly different timing formula. I can't get the output to ever go high. I supply 1.5 volts and have the following component values. Ra=220, Rb=3200, and Ct=100uf. I also tried values of Ra=2200, Rb=22000, and Ct=22uf.  I get the same results either way. The voltage on Ct stays around 1.1 to 1.2 volts. All my components are surface mount and are quite close together, however I have checked for shorted traces often and have changed the 1555 and rechecked for shorts. I've tried running it from a single cell and a power supply plus I've disconnected all output circuitry. Could a 22uf capacitor have too much leakage current to allow the 1555 to switch states? Are my resistor values too low? Any insight would be greatly appreciated, Thanks!

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


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