Ren-T Design Question

[holtm]

What is the purpose of R1 on the schematic?
http://christmasinshirley.com/wiki/index.php?title=Image:Ren-T_schematic.gif

I'm going to build a simple ZC board and can't figure out if a resistor from ground to the rectified 12V is needed. Then the DIY in me wants to know why.

Thanks.

[P. Short]

R1 is used to put a nominal load on the zero-crossing to ensure that it actually gets low enough to turn off the transistor on the Renard boards. This was something that Ernie Horning found necessary on his setup last year. It's possible that a nominal amount of capacitance on the zc signal may hold it up, and that the load on Renard boards would be too low to pull it down.

There hasn't been any science involved in selecting the value of R1, so you might want to play with it a little bit if you are having problems related to not detecting the zc signal when using the diagnostic firmware.

--

Phil

[holtm]

Thanks for the explain. I have some intermittent trouble with the ZC. I think the problem happens when the pic just starts up and the pic is selecting a Hz and the ZC is a little off. But I can't be sure. It also happens to correlate to when there is 3" of snow. I have been blaming water. I'm going to build a second ZC board today to separate a few controllers, that should help me troubleshoot.

[holtm]

Just to follow up so others will know. The resister turned out to fix the old ZC. Odd how it worked sometimes and not others. I made another and seperated 1/2 of my display. It is definatly easier to troubleshoot with duplicate parts.

[kmc123]

What value did you end up using Holt?

[holtm]

10K worked and still works. I haven't had a ZC issue since.