Take a little example from the UPS industry they use hybrid static switches in some of the smaller models of ups consisting of either two triacs and a pair of relays all the way up to very large static switches with parellel pairs of thyristors and moterised circuit breakers as noted below the triac is only used to get the zco operation uasally without a heatsink and a slave mechanical contact to reinforce it after it has opperated this gives a no bounce switch and limited power disapation due to the relay reinforcment. The simplest form I have seen is a relay driven at twice its normal coil voltage (capacitor storage)and a single triac across its n/c contact the operation is then drive the relay on fast with a high coil voltage and use the triac to bypass the n/c until it has released properly. It may be worth investigating Regards Steve... -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Peter L. Peres Sent: 01 November 2002 09:51 To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Speeding up a relay - zero crossing detection On Thu, 31 Oct 2002, llile@SALTONUSA.COM wrote: *>The reason these relays bounce so much on release, is they are released by *>a spring only. At the end of it's travel it's spring force is lightest, It bounces so much because it is actuated by a LINEAR spring. Faster devices use a mechanical or magnetic hysteresis element to speed up 'decision'. In other words, find a better relay ... Peter *>So far I've rejected triacs because of too much heat. I'll be taking a *>closer look at them tomorrow. You said you will be actating it now and then. A triac used in this role would not get hot. You could put it in parallel with the relay. The relay would switch for continous operation and the triac for pulses. Also one could use the scheme that uses the triac as breaker to avoid arcing on the relay. Peter -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu