Short beep (from a hi latch)

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OK done. It functions but it is faint. nice sound but not loud.
With the previous setup it just crackled before i added the NPN
Now I dont buy the best parts. I just took two of these and gave them 5V and the were loud but each produced a different sound.
Adding the NPN back to the new config made the sound louder.
 
It looks as if the speakers are mis labeled.
i have 5V & 12V. i tested all of them at 5V. they all sound but the 5V are a bit louder. Duh.
I removed the NPN and gave it one of these TRUE 5V buzzers and it did sound. twice as loud. This setup will be outside so I may keep the NPN so it can be heard over any BG noise.
 

As you've probably figured out, all buzzers and transducers are not the same.
Some are designed to be driven with an oscillator. Others are self driven and can be connected directly to a voltage source to operate.
The NE555 is capable of 200mA output current at about 1v below the supply (so Vcc=5, Voutput =4). The transducer only requires 30mA.
Something odd going on there.

Try changing the connection from 555 to transducer as shown below:



So that the 555 switches the ground side of the transducer.
 
Last edited:
I made the change. the result was no difference in how loud it was but there was also a constant faint whine now. unlike the ones i posted before these 5V transducers have a part number. Here are the specs.
I had thought that these were 12V. The reason i did not use them. The ones i was using had no part number. I relied on the outlets datasheet for info. To be honest the ones i was using i have no way to determine what the real ratings are.

 

These are not 5V transducers, they are 3V (operating voltage) transducers. The acceptable range is 1.5-4vdc. The resonant frequency will change +/- 300hz and I'm assuming that is associated by a change of operating voltage. Usually, there would be a graph showing the operating voltage vs resonant frequency. So...if the operating voltage changes, the resonant frequency changes, so the 555 driver frequency needs to change or there will be a change in buzzer loudness.
 
BTW-

If you have an iPhone, you can load an SPL app and measure the loudness of the tone from the transducer.
 
ThomsCircuit said:
I made the change. the result was no difference in how loud it was but there was also a constant faint whine now. unlike the ones i posted before these 5V transducers
Click to expand...

Oops....yeah, the buzzer will be on when the timer is off....we don't want that. I forgot the 555 output is at ground when off. sorry.
 
eTech said:
So...which device did you end up using, and what is the drive circuit configuration and supply voltage sources?
Click to expand...
I used the buzzer with the part number TMB...
The circuit i like was with the 2 555 ic's. No transistor on the buzzer.
The supply voltage is a 12v 10amp power supply dropped down to 5.5v via a buck converter. The voltage reading at the input trigger is 5.0v.
I increased the cap @ C1 from 2.2uf to 10uf for a slightly longer beeeeeeep.
The sound it produces now is very pleasing. Sounds like an luxury appliance.
Since you have taken so much time with this I want to order all nessasary parts to make this as you outlined (with exception of C1.)
 
I would like to make this project with all SMD components. Ive located everything except the diode. You have any suggestions or recommendations on this route?
 
ThomsCircuit said:
I would like to make this project with all SMD components. Ive located everything except the diode. You have any suggestions or recommendations on this route?
Click to expand...

I get parts from Mouser, but 1N4148 is pretty common, you can get it from just about ant parts house.

Have you designed an SMD PCB before? Traces will be harder to route since via's aren't used. You can add via's but then the board cost goes up.
If you are going to assembly the board yourself, you may what to limit the size of SMD devices to something that is easy to handle when hand soldering. You won't be able to use a socket with the SMD 555's, and you could replace the two 555's with a single NE556 dual timer chip.

There are PCB fab houses that will assemble the board as well, but usually the parts have to be from their inventory. JLPCB is one such fab house.
 
Gap in net?
Its a glitch. I have no gaps but after i pour the copper to connect the ground net to the smd ic's then run the rule checker i get these two errors. Gap in net. It is a GND track. They are connected to a pad on component but then go nowhere. I can delete the error then there is nothing there. nothing to connect, nothing to correct. nothing to join. What should i do? if anything. in Gap02png i move the component and the Error remains where it is.

 

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3D render.
Speaking of diodes. I could not locate a ECAD model for design spark. I made the one here. I can see it needs some work.
 
eTech said:
Have you designed an SMD PCB before? Traces will be harder to route since via's aren't used.
Click to expand...
Ive made pcbs with just 2 components. the 555 and a resistor. based on a suggestion you made a while back Ive made it a point to never use vias.
 
Hi

I made a small but important modification to the circuit. See below.

The previous circuit would not reset for each pulse at the trigger of U2 resulting in missed state changes.
So to fix this, I've connected U2-RST to U2-Trigger. I also removed R6 (don't really need it since the output is already internally pulled down to ground), then reused it to replace R4. With this configuration, U2 will always reset when a trigger is detected. The resulting modified circuit is below.

 
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