Hello to the forum. I was wondering if someone could help me understand the problem described below.
I'm working through some experiments with electronic components and have hit a hurdle trying to power a piezo buzzer via an rc timer/transistor combination. I've attached a picture of the circuit to this email and was wondering if you could help me understand how to meet my goal.
Alone the RC timer (r1 and c1) will charge the capacitor to 5v as you would expect but once I connect the transistor the voltage drop across c1 never exceeds .7v. I figured that this is because the current leaks through the transistor's base/emitter as the transistor becomes a switch. I'd appreciate it if you could confirm this.
Okay, the RC timer works and once the base reaches .7v the collector/emitter connects and I can power an LED.
All good, but I then I replace the LED with a 12v peizo buzzer and it doesn't make a sound. Reading the current between the LED/buzzer and collector I've recorded 1.4mA passing through the buzzer and 6.8mA through the LED.
The buzzer when connected directly to the 5v power supply makes a noise and I've noticed it draws 7.9mA and when connected to 3.3v draws around 4mA and still makes a noise.
I've confirmed the polarity of the buzzer and can see that the collector/emitter can provide at least 6.8mA but cannot understand why the current drops to 1.4mA when I introduce the buzzer.
What is the solution to this problem?
I'm working through some experiments with electronic components and have hit a hurdle trying to power a piezo buzzer via an rc timer/transistor combination. I've attached a picture of the circuit to this email and was wondering if you could help me understand how to meet my goal.
Alone the RC timer (r1 and c1) will charge the capacitor to 5v as you would expect but once I connect the transistor the voltage drop across c1 never exceeds .7v. I figured that this is because the current leaks through the transistor's base/emitter as the transistor becomes a switch. I'd appreciate it if you could confirm this.
Okay, the RC timer works and once the base reaches .7v the collector/emitter connects and I can power an LED.
All good, but I then I replace the LED with a 12v peizo buzzer and it doesn't make a sound. Reading the current between the LED/buzzer and collector I've recorded 1.4mA passing through the buzzer and 6.8mA through the LED.
The buzzer when connected directly to the 5v power supply makes a noise and I've noticed it draws 7.9mA and when connected to 3.3v draws around 4mA and still makes a noise.
I've confirmed the polarity of the buzzer and can see that the collector/emitter can provide at least 6.8mA but cannot understand why the current drops to 1.4mA when I introduce the buzzer.
What is the solution to this problem?