Solved my Renard SS8 false triggers

[DIY Sparks]

First, let me say the Renard SS8 board and its design is rock solid, and I'm sure the false triggers that plagued me were due to my pitifully small application. Unlike some of the folks here, my display doesn't dim the street lights when I switch it on.

I had 8 channels of fifteen C7 incandescents (for 600mA) each, non-PWM. When dimming, adjacent channels would sometimes flicker. I took a shotgun approach to the problem, as follows:
5v regulator: added 0.33uF cap across IN, 0.1uF cap across OUT.
ST485's: 0.1uF across power (pins 5 & 8).
TRIACs: 39-ohm / 0.01uF (series) snubbers across MT1 and MT2.
(the added components soldered nicely on the bottom of the board, and an insulator sheet from a deceased PC power supply keeps all the electrons peaceful)
Optos: Changed MOC3023's to MOC3020's (to reduce trigger sensitivity).
But likely the real cure, changed the PIC to PWM firmware.

Absolutely NO problems for about three weeks now. Hope this helps someone else.

[dirknerkle]

I think Wayne recommends using PWM firmware in the SS boards, anyway. But nice work just the same. All the SS boards are rock-solid. What's nice is that after the SS8, you already know how to assemble the SS16 and SS24. They all use the same parts -- just more of them on the other boards.

Good job!

[IdunBenhad]

Hi:
It would have been interesting had you tried the board with only the bypass capacitors to see if that cured your problem.

Many designers seem to miss or ignore the importance of bypassing and some of the boards can end up with weird problems. It is not too expensive or space consuming to include bypasses.

Good job, and I think your results will help others.

[gocats7]

Could you elaborate on "bypasses"? How do I do that?

[wjohn]

You will notice many boards have 0.1 uF caps located near each IC.

[P. Short]

The PICs, which I think are the only important parts here, already have 0.1uF bypasses right next to them. The ST485 chips are not going to be sensitive to that, and there is plenty of capacitance in place for the regulators. The main reason for bypass caps, IMO, is to avoid wasting time on wild-goose chases when problems do crop up. They are important for high-speed boards and/or high-speed chips, for boards with lots of wide busses running between ICs, and for boards without ground planes. None of that applies here...