| ??? 02/22/10 23:12 Read: times Msg Score: +1 +1 Good Answer/Helpful +1 Informative -1 Overrated |
#173442 - Unbelievable!! Responding to: ???'s previous message |
Sandip said:
Can I use such diodes externally if I want to connect high voltage live line through some megaohm resistor directly to the port pin and detect zero-crossing in the firmware. The fact that you ask whether you can, demonstrates, that you are not skilled enough to do this! If you do what your links recommend, then your whole circuit is carrying dangerous high voltage, which can kill you, when you touch it anywhere! The high ohmic resistance must can withstand surge voltages of up to 6kV. So, special high voltage resistor must be used, like this here: http://www.vishay.com/docs/28732/vr25.pdf Usual resistors must not be used! The microchip link shows a varistor to suppress surges. But it doesn't show any series fuse, doesn't show any EMI-filter for the triac and doesn't show any temperature fuse mounted in direct contact to the varistor, disconnecting it, when becoming hot from too many hits. There's no line about leakage currents, isolation gaps and saftey distances. So, this link tells only half the truth, which makes it absolutely dangerous for a beginner, who cannot read between the lines and does not have the proper knowledge to design a circuit being permanently connected to mains. Sandip, this microchip link is a bad joke, a slap in the face. If you are clever, you will keep the hands off this crap! Kai Klaas |
| Topic | Author | Date |
| Zero crossing detector - technique adoption | 01/01/70 00:00 | |
| Sounds like a bad idea to me! | 01/01/70 00:00 | |
| relying on parasitic diodes | 01/01/70 00:00 | |
| Confusing | 01/01/70 00:00 | |
| I mean | 01/01/70 00:00 | |
| Designing to typical values | 01/01/70 00:00 | |
| what blather | 01/01/70 00:00 | |
| " IDEA ? " - RIDICULOUS | 01/01/70 00:00 | |
| at least for this one | 01/01/70 00:00 | |
| Oh dear: | 01/01/70 00:00 | |
| tough, but true | 01/01/70 00:00 | |
| just caught this one | 01/01/70 00:00 | |
| Idiom | 01/01/70 00:00 | |
| It really is a *very* bad idea! | 01/01/70 00:00 | |
| Don't blindly follow app note | 01/01/70 00:00 | |
| It's not so much the parasitic diodes... | 01/01/70 00:00 | |
| two reasons | 01/01/70 00:00 | |
| What should I do ... | 01/01/70 00:00 | |
| That won't help at all! | 01/01/70 00:00 | |
| two wrongs | 01/01/70 00:00 | |
| Most app-notes don't work ... because they're wrong! | 01/01/70 00:00 | |
| This is typical ... | 01/01/70 00:00 | |
| I hate to tell this,... | 01/01/70 00:00 | |
App engineers not always the sharpest tools in the shed | 01/01/70 00:00 | |
| Unbelievable!! | 01/01/70 00:00 |