Looking for guidance in making a micro buzzer that weighs less than 5g with 1 minute delay

Thread Starter

scotsscripts

Joined Nov 24, 2019
5
Basically the title says it all. I'd like to make a micro buzzer that uses a 3.5v coin battery as power that will start buzzing after a minute. I know I can use the 555 chip (I think that's the number) and a resistor as a controller for the timer, but I'm just not sure how to make it all fit together. If I have a circuit diagram I can make it go, but I've done a lot searching and haven't found anything that is small enough.

Any ideas or circuit diagrams that you know of that does what I am looking for?

I know enough about electronics to get in trouble but when it comes to component design I'm a bit lost. I've tried using online circuit testing/design platforms but haven't had success.
 

djsfantasi

Joined Apr 11, 2010
5,847
haven’t found anything that is small enough.
First, for anyone to be able to give you an answer, I think you’ll need to define “small enough”! Is that 50mm square? Or 20mm square? Or something else? How high can it be? 3mm? 5mm? 10mm?

Waiting for a hint...
 

Thread Starter

scotsscripts

Joined Nov 24, 2019
5
Thanks for your messages.

For the size I want it to fit on top of the 3.5v coin battery, and for height, hopefully not any thicker than the 3.5v coin battery. The thinner the better.

For start/stop/reset I'm thinking of some kind of tiny hardware super basic on/off switch. Even something as simple as putting a pin in a hole to disconnect the circuit and removing the pin to connect it.

The application for this is basically something is going to be hidden, and the buzz will start about a minute later so it can be found.
 

ci139

Joined Jul 11, 2016
1,017
if you prog your 555 to your buzzer's frequency then set a capacitor amplifier (delayed start) to it's reset(Outp.Lo) --or-- re-trigger(Outp.Lo) --or-- threshold(Outp.Hi) . . . or use 556
 

Thread Starter

scotsscripts

Joined Nov 24, 2019
5
I've been learning about 555 chips and was wondering if there is some kind of calculator where I can put in the time I want to delay and then it gives me options for capacitor/resistor pair? The calculators I see give you the time from resistor/capacitor pair, but I don't know what values are feasible. I guess I'm looking for guidance on the best approach in figuring out the hardware needed for a particular 555 chip delay timer.
 

djsfantasi

Joined Apr 11, 2010
5,847
I've been learning about 555 chips and was wondering if there is some kind of calculator where I can put in the time I want to delay and then it gives me options for capacitor/resistor pair? The calculators I see give you the time from resistor/capacitor pair, but I don't know what values are feasible. I guess I'm looking for guidance on the best approach in figuring out the hardware needed for a particular 555 chip delay timer.
You are in luck. There is. Search for “555 calculator” and you’ll find several sites.
 

Alec_t

Joined Sep 17, 2013
10,611
1 minute is quite a long time for a 555 timer. Given the size constraints you will probably need the CMOS SMD version (a) for satisfactory operation from a 3.5V coin cell and (b) to allow the use of physically small capacitors of several uF capacity. However, depending on the buzzer current draw, a transistor may also be needed to drive the buzzer from the 555 output.
 

Alec_t

Joined Sep 17, 2013
10,611
Yes, indeed. Ok, it's not a very long time and is well within the timer's range, but it nevertheless involves high value timing components (resistor and/or capacitor) so needs extra care in avoiding leakage currents if a predictable delay is to be obtained.
 

Thread Starter

scotsscripts

Joined Nov 24, 2019
5
I haven't figured out what I'm going to use for the buzzer. I'm learning as I go along here, just trying to make it as small and light weight as possible. The batter is a 3.5v coin battery, so it's about the size of a quarter and I want all the rest of the stuff to fit on top of it, small enough so the height is no more than double the coin battery.

I guess there's a reason there aren't any micro buzzers with built in timers out there already, this all seems extraordinarily complicated for such a simple application.
 

djsfantasi

Joined Apr 11, 2010
5,847
I haven't figured out what I'm going to use for the buzzer. I'm learning as I go along here, just trying to make it as small and light weight as possible. The batter is a 3.5v coin battery, so it's about the size of a quarter and I want all the rest of the stuff to fit on top of it, small enough so the height is no more than double the coin battery.

I guess there's a reason there aren't any micro buzzers with built in timers out there already, this all seems extraordinarily complicated for such a simple application.
Good luck. IMHO, your requirement for the height may be the toughest to beat. I think the buzzer itself may be taller than that.
 

AnalogKid

Joined Aug 1, 2013
8,229
this all seems extraordinarily complicated for such a simple application.
The only complications are the size and the fuzzy requirements. For example, typical coin cells (as opposed to button cells) come in four diameters and at least 6 thicknesses. That is a wide range of sizes, and has a direct impact on the level of circuit complexity that can be supported. Also, a 2450 coin cell weighs 6.8 g, which is outside your weight spec without the circuit or buzzer.

Also, the overall diameter and thickness require all surface-mount (SMT) components, and soldering an 0805 resistor by hand takes some skill.

Can the "buzzer" be a piezo beeper instead, or do you really want a buzz-type sound?

ak
 
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ronsimpson

Joined Oct 7, 2019
349
Here is a list of 200 low voltage buzzers.
DigiKey buzzers
Here is a list of 3V coin batteries. (some solder in so you do not need a holder)
coin batteries
I have used 6 or 8 pin micro computers like PIC 12F508 or 10F200 They can do all the timing and logic. These computers are so low power that we sometimes do not include a on/off switch.
1574999442176.png
Snap dome switches: There are many types, but here is one.
switch
I do not like pulling more than 10mA from the little batteries. So pick a low power buzzer.
 
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Thread Starter

scotsscripts

Joined Nov 24, 2019
5
The only complications are the size and the fuzzy requirements. For example, typical coin cells (as opposed to button cells) come in four diameters and at least 6 thicknesses. That is a wide range of sizes, and has a direct impact on the level of circuit complexity that can be supported. Also, a 2450 coin cell weighs 6.8 g, which is outside your weight spec without the circuit or buzzer.

Also, the overall diameter and thickness require all surface-mount (SMT) components, and soldering an 0805 resistor by hand takes some skill.

Can the "buzzer" be a piezo beeper instead, or do you really want a buzz-type sound?

ak
"Buzzer" was just me, it can be anything that makes a sound that can be heard from at least 20' away. I found a piezo with a built in timer on Alibaba but they want a minimum order of 1,000 units...
 
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