Usage of Varistor/Transient Voltage Suppressor ??

Posted on 2009-02-19
Medium Priority
Last Modified: 2013-11-10
I have a 220V to 12V 500mA transformer+rectifier plugged into my wall socket, that drives a pair of relays. I've put protection diodes on the relays. However I still have a 500v kickback into the mains when I turn off the power.

How am I supposed to fix this? Using a varistor/TVS or something? Do I connect it across the mains before the transformer? Can someone suggest a specific part that I should use?
Question by:kurian2z5
  • 2
  • 2
LVL 63

Accepted Solution

SysExpert earned 200 total points
ID: 23723403
any TVS rated for the volatage ( 220) and the amperage  should work.

I would check that the diodes have not burned out as well as have some indicator LED as to the status of the TVS since they also can burn out with too many transients.

Lastly look into a better relay, or perhaps 2 sets a small one that activates a larger one or an opto-coupler.

I hope this helps !

Author Comment

ID: 23723499
I put a 275v MKP capacitor before the transformer, as I assume the kickback will be DC. However it doesn't seem to do anything. It doesn't seem to absorb any current at all.
LVL 63

Expert Comment

ID: 23724621
You really need to use one of my suggestions.  simple capacitor is not sufficient.

Author Comment

ID: 23743227
I've put a bidirectional TVS and it works now.

Featured Post

Keep up with what's happening at Experts Exchange!

Sign up to receive Decoded, a new monthly digest with product updates, feature release info, continuing education opportunities, and more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Does your iMac really need a hardware upgrade? Will upgrading RAM speed-up your computer? If yes, then how can you proceed? Upgrading RAM in your iMac is not as simple as it may seem. This article will help you in getting and installing right RA…
A feature on Tesla vehicles and their impact on the automotive industry.
This video shows how to quickly and easily deploy an email signature for all users in Office 365 and prevent it from being added to replies and forwards. (the resulting signature is applied on the server level in Exchange Online) The email signat…
Integration Management Part 2
Suggested Courses

850 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question