Hi,

I bought 10 buzzers 12V DC (https://nl.aliexpress.com/item/4000...t_main.37.268b79d2f39MSD&gatewayAdapt=glo2nld)

I want to use at least 8 of these buzzers (on different locations) at the same time. I installed them on location, but when I power them, they make a really bad sound. Each of the buzzers seperately sound ok, but with every buzzer extra in parallel the sound gets worse. It's not a lack of power, since the power supply has more than enough amps. I even tested with a 12V/8A power supply. I think it's the internal oscillating circuits that resonate with each other messing up the sound they make.

What is the easiest way to solve this. I hope not buying 8 different power supplies

Thank you for the help.

 

Someone may actually know the answer, but I would (1) try connecting each one in series with a diode (nearest the +12V) and (2) put a capacitor in parallel with each buzzer and (3) maybe largish capacitor across the supply. Not very scientific, but these successive actions might help....

 

The description says "electronic", but it looks like a mechanical buzzer, the kind with contacts that make and break. If so, it is putting a lot of trash on the power lines.

Put a large value electrolytic capacitor, at least 100 uF, across each buzzer *at the buzzer* and see it that improves things. The + side (anode) of the cap goes to the red wire.

ak

 

The appearance and low frequency of the buzzers indicate that they are probably old-fashioned mechanical, not electronic (oscillator). Then they simply turn on and off, over and over.

Maybe your power supply has poor or no voltage regulation. The buzzers have separate frequencies and on the occasion that one or a few turn on at the same time, the voltage is high so their frequencies are probably higher. On the occasion that many turn on at the same time, the unregulated voltage and frequencies drop.

Try adding a high capacitance (1000uF to 12000uF) parallel to the power supply output to smooth its voltage.

 

You could try adding the caps at the buzzer along with a ferrite core if the caps don't work alone.

 

If it is electromechanical, it might be the flyback voltage when turning off that is the problem. I would try a reverse biased diode across each buzzer. Anode to the minus and cathode to the plus.

I don’t suppose you have a scope?

 

If it is electromechanical, it might be the flyback voltage when turning off that is the problem. I would try a reverse biased diode across each buzzer. Anode to the minus and cathode to the plus.

Certainly a possibility but you did say you've put them in various locations. My concern is voltage drop due to long runs of wire. I remember working on a 32 volt emergency lighting system in a grocery store. The 32V lamps worked great near the battery backup supply but out by the front of the store they were as dim as a politician. We ended up putting 12V lamps where the light was too weak. 24V midway in the store and left the 32V lamps where they were getting sufficient voltage.

The CORRECT solution would have been to run a whole new set of cables, large enough to have very little voltage drop over the long distances. It was a very long time ago and I don't recall how deep the store was but it was definitely a couple hundred feet deep. If you're putting these things a long long way from the power source then I can imagine that the resistance of the wire is the biggest problem you're facing. @BobTPH also has a good point, could be flyback. But that would only be in the case of a mechanical buzzer. I've seen those types of buzzers before and they are definitely electronic with a tiny speaker. Though they are reportedly drawing only 25mA, 10 of them would only draw 250mA (0.25 amps). Your 8A supply is overkill, but it's not the problem. I'm still leaning on the wire diameter being the root cause of the troubles. But Bob may have a point. But that's IF they are mechanical. Since you have 10 and want to use 8 you can easily afford to break one open and see exactly what is in the box.

BTW: I noticed the ad states that 1 pack of 10 has been sold. I'm assuming you're the one who bought the pack of 10.

 

Thank you all for the info. a diode over the buzzer did not really help. That was something i already tried myself. The capacitor however did help. The 2 biggest i had around where however only 470 uf and 100 uf. They improved the 'sound' on some buzzers, but not on all. So i purchased some bigger onces and will try with these. Keep you informed.

 

a diode over the buzzer did not really help. That

If you are talking about the flyback (reverse biased) diode, you would need to put it on all of them to fix it.

Edit to add: I would do any testing of potential solutions in just two buzzers.

 

What size wire did you use and how long is the run?

 

I recall a friend having a similar problem MANY years ago. The problem in that case was a transformer with way to low a current capability. But if that is not the problem, then either the wire resistance or the connection resistance is the problem. Put a voltmeter across the buzzer at the location that sounds worst and you will see a voltage that is too low.

 

or the connection resistance

Hadn't thought of that. But it reminds me of my neighbor's sprinkler system. One zone quit working. I disconnected the wires from the solenoids and checked each circuit for 24VAC. They all had their voltage when turned on. So after reconnecting the sol's I tried each and every zone. Still, that one zone just wouldn't work. Thought it was a bad solenoid so I replaced it. That did not solve the problem. So I swapped two zones. Now the non-functional zone worked and the formerly functioning zone didn't. AH! It WASN'T a bad solenoid, it was a wiring issue. So at the controller I checked for 24VAC. Every zone seemed to be functioning properly. Yet even though there was voltage there was no current. So I started digging up the wiring. Fortunately I only had to dig about 8 to 10 feet before I found the issue. Someone had spliced the wires together with crimps and then wrapped them in electrical tape. Then reburied them. Moisture had caused corrosion. So after stripping, cleaning and twisting the wires back together all zones worked. That meant I had to replace the entire run of some 80 feet from the controller to the valve box. While ripping up the old wire I found yet another splice zone. Someone cheaped out and tried to just splice in scrap runs of sprinkler wire rather than run a proper length of wire. So even if I did fix that splice zone I found, there was one more that would have necessitated digging up the line. Good thing I replaced the whole run.

So yeah - a bad connection can cause problems. You can read full voltage but due to the weak connection you can have high resistance and low current.

Excellent point Bill.