creating NOISY mains..

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I have a circuit that needs to be able to withstand some bad mains power supplies and keep on working. I would like to test it without spending $$$ on EMC testing. Any ideas on creating the world's worst power supply?
I am talking lots of noise and nasty spikes here.

I can maybe use a series transformer and couple noise into the supply that way, or I can connect it together with an arc welder and arc away.
Any other (better) ideas?

regards
Carel

www.pteq.net
Home of:
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Connect it together with these :
- a motor -> for noise (vacuum cleaner, fan, etc)
- electric lighter -> spikes.

Real men don't use backups, they post their stuff on a public ftp server and let the rest of the world make copies.

Last Edited: Mon. Jun 27, 2005 - 11:19 AM
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Try also a piezoelectric igniter for gas. Replace metallic 'ground shield' by few wire windings, acting as a primary winding of a transformer. We use that system and is proved to cause enough electrical noise: if a system don't pass this test, shure that would not pas EMC for european norm 61010 about EMC's.

Aslo arc welder should be good also, specially the electronic ones, because of their SMPS.

You can try to connect few computers to a non filtered power line. They also made a big amout of noise.

Guillem.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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One of the ways is to use an SCR-based control, like one of those light dimmers. That noise is synchronous with the AC. SMPS makes noise at the switching rate of the supply. It is not synchronous and it is much higher frequency (typ 50KHz to 500KHz, tho some higher, some lower). Almost all computer power supplies are switchers BUT they also have to have good filtering to pass CE for Europe.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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I found a nice way.

I took an automotive ignition coil, and I am switching a relay to create a nice spark discharge every 5 seconds or so. One of the HT wires going to the Spark gap, first goes for a couple of turns through a Torroid Ferrite, forming the primary winding of a transformer.
One of my mains leads going to the EUT also takes a few turns around the same ferrite, forming the secondary winding.
The high current discharge through the spark gap induces one hell of a spike into the secondary winding of the ferrite transformer, the seconday being in series with the mains going to my EUT.

To test the spike strength, I wanted to see if my old cheapie multimeter would handle what I could throw at it. It let out a brief puff of smoke after a few seconds of operation. I therefore gather I have one nasty spike generator! The spark of course also provides us with some nice radiated noise, which is also handy for testing. You can easily adjust the strength of the spike by changing the number of turns you use on the seconday and primary of the ferrite transformer.
I have used maybe 8 turns on each side.

By the way, my EUT seems to be holding up well. It does reset with every second or third spark, but at least it is keeping all of the special smoke on the inside.

regards
Carel

www.pteq.net
Home of:
- Polygon Technologies CC