serial comm problem

[dhouston]

> I haven't found a relay yet I could directly drive

There are many 5v Reed Relays, many of which need less current than an LED... at prices in volume of under $1 a lump, they're not exactly budget breaking either.

And they tend to be rated for billions of cycles.

[schu4647]

Those are girly relays. I use manly relays.

[dhouston]

Those are girly relays. I use manly relays.

Manly relays can be turned on by girly relays.

[Melanie]

Haven't girly things always turned-on manly things since time began?

I'd just want to add (before we digress too far), that as a matter of good practice, I'd never hang any power sucking switching component on the same supply line as that for your PIC (and that goes for your vibrator motor!). That +5v (3.3v) line is sacred. Your PIC and some other logic and that's it. All your Power devices get hung on the raw input supply, not on the nice regulated PIC supply. In following that rule, I've NEVER experienced any problems switching power devices.

Big Power Relays need a big magnetic field to slam shut their contacts in order to carry Amps and things... and a big magnetic field unfortunately can only be generated by a current which a PIC can't provide. And if you did, then the induced back-emf and spikes means you'll have to significantly filter your PICs supply to stop it tripping out.

Take my advice... NO power devices on the same supply line as your PIC.

[Ioannis]

And if I may add to Melanies post, use if possible optocouplers to drive external power devices. It is the most secure method of isolation.

I had to go twice on a town up in the mountains 250Km away, for an automation once I made with 16C55 and assembly lanquage, but with no isolation and finally understood that I was too inexperienced that time in industrial automation design (long time ago, I would say...).

Ioannis

[mister_e]

AND depending the design, having different ground is also a good practice. It's amazing sometime how a simple looking thing could ruin an entire design.

Probably even worst when you mix, analog, digital and power signal on the same design... oh my god! How many hours i, and many other i guess, already lost to know why... even a bad ground plane design may ruine your life... ARGGGHH!

Thanks to Bead & friends to exist