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

Switching High current resistor load

Switching High current resistor load

Switching High current resistor load


I would like to make a PCB circuit that basically is a microchip controlled switch citcuit for a 5V 5.2A purely resistive load. The switch would be activated for 10Seconds maximum and would not have to be operated again for 60secs or more (could be days actually).

Can typical PCB traces handle these types of currents? What device would be best (Fet, relay, etc)?  

If the load was later changed to a 10A resistive load could the same be accomplished... or is this to much?


RE: Switching High current resistor load

A FET would do the job admirably. Current is well within the capability of a PCB if you make the tracks wide enough. You could easily get up to 20A - 30A on and off a PCB without any unusual tricks and with enough effort PCBs can carry much higher currents. Think about your average variable speed drive for example - mains voltages and tens of amps on a PCB.

If we learn from our mistakes I'm getting a great education!

RE: Switching High current resistor load

Just find a FET with a lower Rds  to avoid all temp issues.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Switching High current resistor load

You can always just run fatter traces.  We've purchased laser diode drivers that can dump 200 amps direct;y from a single DFET.  Current came off the board through a 1-in wide flex cable.


FAQ731-376: Eng-Tips.com Forum Policies

RE: Switching High current resistor load

Hi.  Agreed with that said before.  With a 1/2" track, you can route 10Amps with some 4ºC temp rise.

Use a FET rated well over your 5V/10A, and saturation Vgs near 5V.  You will likely use those TO220 cases, so you can lay it down horizontal over a huge copper island to use the same board as heat radiator, though most power FETs stay fairly cool with high currents.

Be careful with noise at the gate pin, you may want to add a pull down resistor of some 1Meg (N-Channel FET), to avoid false triggering while the micro is powering up, as the control pin of the MCU will be likely tristated.

Good luck with your board!


RE: Switching High current resistor load

For high currents like this it is usual to specify 2oz copper rather than the usual 1oz. This halves the track resistance.

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