Can I power a 3.3 volt device and something that requires a higher voltage off the same power supply?

You can connect your 3.3 volt device to the output of the 3.3 volt regulator.

You can connect the 9 volt battery to both your 9 volt device and the input to your 3.3 volt regulator.

If the 2 devices have signals that need to be connected, ensure the 9 volt device does not output a voltage higher than 3.3 volts.

Hi Simon,

Do you have specific devices in mind for use with this common ground dual voltage supply? There may be a few more components that might be needed in some instances to make sure both devices work together smoothly.

John

I'm looking at an Xbee WiFi Module and a piezo buzzer (which may need to be driven by an external square wave generator but I haven't been able to determine that yet.)

It seems buzzers are going to typically require more than 3.3 volts to sound at adequate volume.

Hi Simon,

Piezo elements do require an oscillator/driver circuit, however if you get one billed as a buzzer chances are the circuitry is already built in. The ones that make the small beep like you hear from a microwave oven or other appliance are probably running on 5 volts. 9 would improve the volume level. Make sure that you use bypass capacitors on the input and output of the 3.3 volt regulator to improve operation. You can check the data sheet for the regulator you choose as they will likely have recommendations. Unlike a motor or relay the piezo buzzer will not require any diode protection.

John

The piezo buzzer is listed here MCKPT-G1410A1-3919 - MULTICOMP - PIEZO BUZZER | Newark element14

and the voltage regulator is listed here UCC383T-3 - TEXAS INSTRUMENTS - LDO VOLTAGE REGULATOR, 3.3V, 3A, TO-220 | Newark element14

I see a schematic in the ripple section that shows 10 microf capacitors on the input and output so that may be their recommendation.

Hi Simon,

This Buzzer is a buzzer and will require no additional circuitry. At 3mA max it can even be run off most logic chip outputs. If the output is Open Collector you will have to wire it in an appropriate manner. The only problem that you may have is that while it will operate at 3 to 30 volts the 3 mA Max tells me that the volume will not likely be very loud and may not vary that much with the higher voltage. If louder volume is needed you can search for buzzers that have a higher mA draw and you may have to add a transistor between your logic device and the buzzer if the mA gets above 10 mA.

John

I was thinking the same thing, connect a transistor base to the Xbee output.

Thank you for consistently giving me these tidbits I probably wouldn't have learned otherwise, John. I'm looking into other buzzers as well.

Hi Simon,

If you really need something that gets the attention check out a siren module. There are sirens that can produce 100 db or more with the power from a 9 volt battery.

John