Piezo Horns for swim race starter - flyback diode ?
i have piezo horn using sound start of swim events.
i can not locate datasheet, except info :
impedance 1000 ohm @ 1 khz
voltage nominal 15 v
voltage peak 35 v
frequence response 3 khz - 30 khz
sensitivity 1w,1m 92 db
i using pwm tone of around 7 khz.
the piezo horn connected constant 12vdc positive pin, , negative horn pin connected 2n2222 or 2n3904 npn transistor.
the piezo negative pin has pull-up found needed 'reset' horn between pulses transistor.
the transistor driven series resistor pin 12 of mega 2560.
the horn working , satisfied sound , volume.
but since have 400 parents shouting kids, want add 2 horns can positioned behind starting line - don't want parents complaining kids couldn't hear start horn.
so questions :
1. should able drive 3 horns same transistor ?
2. should add diodes ( 1n4004 ? ) across terminals of each horn ( need relay coils ) ?
the 12vdc feeds horns connected 9v linear voltage regulator used power arduino ( gnd , vcc pins ).
i can not locate datasheet, except info :
impedance 1000 ohm @ 1 khz
voltage nominal 15 v
voltage peak 35 v
frequence response 3 khz - 30 khz
sensitivity 1w,1m 92 db
i using pwm tone of around 7 khz.
the piezo horn connected constant 12vdc positive pin, , negative horn pin connected 2n2222 or 2n3904 npn transistor.
the piezo negative pin has pull-up found needed 'reset' horn between pulses transistor.
the transistor driven series resistor pin 12 of mega 2560.
the horn working , satisfied sound , volume.
but since have 400 parents shouting kids, want add 2 horns can positioned behind starting line - don't want parents complaining kids couldn't hear start horn.
so questions :
1. should able drive 3 horns same transistor ?
2. should add diodes ( 1n4004 ? ) across terminals of each horn ( need relay coils ) ?
the 12vdc feeds horns connected 9v linear voltage regulator used power arduino ( gnd , vcc pins ).
1. should able drive 3 horns same transistor ?
not sure. 1000 ohm impedance divided 3 330 ohms, not unreasonable @ 7 khz instead of 1 khz, one-seventh or 50 ohms looking @ current draw of quarter amp, depending on other details following:
2. should add diodes ( 1n4004 ? ) across terminals of each horn ( need relay coils ) ?
the piezo driver capacitor, of not generate emf unless resonates. have not specified pull-up resistor value. otoh, drive correctly should have inductor across it, will generate emf how drive piezo "screamers". whole situation becomes more complex.
the 12vdc feeds horns connected 9v linear voltage regulator used power arduino ( gnd , vcc pins ).
i hope not feeding 9v vcc.
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