Personal Safety Alarm PCB (via Piezo Buzzer) Question - missing inductor part

[mmaswary]

I’m working on a personal project, and I could really use some help. I’m not an electrical engineer, so I apologize in advance if this is a basic question, but I’m a bit stuck.

I paid someone to design a personal alarm PCB board for me. It’s similar to those cheap $10 alarms you find on Amazon, but this one operates via a button instead of a pull pin. Everything seemed to be going well until I tried to order the PCB through PCBWay.

The issue I’m facing is that one of the items in the Bill of Materials (BOM) is missing a DigiKey Part Number, and PCBWay needs this to complete my order. The part that’s missing the Part Number is an inductor (L1), which is located close to the Piezo Buzzer on the board.

Unfortunately, the person I paid for the design has stopped responding, and I’m struggling to figure out what specific inductor I need. I’ve done my best to research and understand it on my own, but I’m feeling out of my depth here.

This project is important to me because I’m making this device for my grandma, and I want to get it right. I’ve attached images of the BOM, schematics, pick and place files, 3D render of the PCB board, and anything else that might be relevant. I also have the fabrication files (gerber/drill) that I can share if that is helpful too. I'm just not sure if it's possible to upload them here.

If anyone can help me identify the correct inductor or guide me on what to do next, I would greatly appreciate it!

Thank you so much in advance for your help!

 

[Nostradoomus]

Delete the buzzer and the inductor from your BoM and PnP files you place with PCBWay, those are thru hole components and probably won't be placed and soldered anyway. You can at least get the rest of the board done while you figure the rest out in the meantime.

 

[jwin615]

I'll put this here and let someone else run with it

Here's the datasheet on the transducer
At 1khz, it's capacitance is 8nf, +/-25%
Use the maths below to determine the L(inductance)
I assume it's a 1khz tone you are after, if not, please specify. I'm not certain how much capacitance changes with frequency or vise versa.

F= 1/2pi root LC

 

[Harry Klippton]

Absolutely wild thread. Iconic pedalpcb content. @Robert can we get a sticky?

 

[Guardians of the analog]

For vintage 80s wake the neighbors alarm tone I would use a red fasel

 

[jwin615]

For vintage 80s wake the neighbors alarm tone I would use a red fasel

Those were only used in the first 17 months of production of the LifeAlert(the green label). After that they moved production to Mexico. The first few production runs(serials starting with 0187-0287) used hand wound inductors. Generally, these are regarded as the Holy Grail ones. Rumor is most were purchased by Ozzy's family and band mates but have been lost to time(and him hollowing them out the carry cocaine. Though, it reportedly led to issues getting up. Eventually, a cocaine packed Life Alert was mistakenly given to a grandmother in SoCal who, whilst falling, smashed the device on her walker, covering her in a cloud of powder. Though her hip was not intact, she was capable enough to flee the scene half clothed. Legend has it, she was humming Marry Had a Little Lamb at 200bpm all the way to the sex commune. She took on the persona of Aunt Hoover, famous for her ability to pull seeds from a whole, uncut lemon with only her lips. Only one interview exists in which she said "And that's why we call ourselves, "The Aristocrats"!

 

[mmaswary]

I'll put this here and let someone else run with it

Here's the datasheet on the transducer
At 1khz, it's capacitance is 8nf, +/-25%
Use the maths below to determine the L(inductance)
I assume it's a 1khz tone you are after, if not, please specify. I'm not certain how much capacitance changes with frequency or vise versa.

F= 1/2pi root LC

I appreciate you trying to help! I'll work on the math now (if you can let me know what variables correlate with F and C it would be helpful so I can input the values!) Thanks a lot!

 

[jwin615]

I appreciate you trying to help! I'll work on the math now (if you can let me know what variables correlate with F and C it would be helpful so I can input the values!) Thanks a lot!

F is frequency to be produced
C is capacitance of the buzzer 8000pf/8nf

 

[mmaswary]

F is frequency to be produced
C is capacitance of the buzzer 8000pf/8nf

Thank You so much!