Transient suppressors sometimes work, but not always. Transients are often quite problematic. If you have a spectrum analyzer available you can characterize the transient so that you will have some empirical starting point. Saturable core isolation transformers sometimes work as a generalized solution but not always. The problem is usually resolved by determining the cause and the character of the transient. For example, if a large compressor is on the line a huge transient current of several hundred amps will spike. Varistors across the compressor motor will be the best approach. As far as the uP itself is concerned, you might want to steer clear of inductive circuits that could be affected by large current transient because of the reactive properties. Fast schotkey diodes on the Vcc supply, right at the processor chip like a free-wheeling diode can help. The problem with most diode solutions is that the diode selected is often slower than the transient and ineffective. There are fast schotky devices that will do the trick. Another important consideration that is sometimes overlooked is the impedance of the power source that supplies the processor. It should be as low as possible with low ESR capacitors. The higher the impedance the more susceptible to transient noise. If all of this has already been discussed, I apologize. I have only seen this for the first time. If you would like to discuss your particular circuitry off list, let me know. I hope I have shed at least some light on your problem. Regards ----- Original Message ----- From: "Spehro Pefhany" To: Sent: Tuesday, June 22, 2004 9:03 AM Subject: Re: [EE]: Supressing fast transients > At 12:43 PM 6/22/2004 +0200, you wrote: > >Hi all > > > >I'm currently putting an inverter design through compliance testing, and > >have a problem with fast transients on the incoming power lines. I've added > >common mode chokes and Y-cap to address conducted emissions, but electrical > >fast transients are getting through, and dirupting operation of the > >processor (16F870). I'm looking as some series inductors as a solution, and > >was wondering if anyone on the list has had similar experiences, and how > >they were resolved. Input currents are around 5A. > > > >Regards > > The CM choke should be taking care of the power supply issues, but maybe > there is other stuff getting through the inputs/outputs. You need to pay > special attention to the paths of those currents.. > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the reward" > speff@interlog.com Info for manufacturers: http://www.trexon.com > Embedded software/hardware/analog Info for designers: http://www.speff.com > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.