| ??? 08/07/06 02:22 Modified: 08/07/06 02:26 Read: times |
#121765 - Of course, but... Responding to: ???'s previous message |
Steve said:
The isolation of a transistor, and some zener protection can be useful. Of course! I would also suggest to add a transistor to keep the load of micro minimal, as you and Leonardo mentioned. A positive secondary effect would be the reduce of ground bounce intenally of micro and the avoidance of unsane ground noise induced effects. But Eugene mentioned, that he uses a current limitng resistor in series to his buzzer, so that he seems to have no high currents running through the buzzer. In this case this current lmiting resistor could also act as protection circuit against the considerable piezo voltages you mentioned. The input protection diodes, which are internally of micro, in combination with the series resistor could form an effective protection circuit. Wether my lines above make sense or not can only be cleared, if we know what Eugene actually has put on his board, means what buzzer and what current limiting resistor he uses... Kai |
