I have a small dilemma which due to lack of knowledge and experience I cannot quite solve myself.
I have an alarm little device ran by arduino (Atmega328p chip) and I will power it off three AA batteries converted down to 3.3v via power regulator. But the problem is that I also need to supply 12v to the loud piezo buzzer when I need to sound that piezo I turn it on via transistor, question is: where in the circuit do I need to install this second step-up power regulator.
Is it as simple as installing two power regulators, one step down and one step up directly to 4.5v battery pack? And basically while 3.3v regulator feeds Atmega Chip, other power regulator will be much in sleep mode and only once piezo buzzer kicks in only then it will draw power from batteries?
Yes, as long as the batteries supply enough current, you can add as many voltage regulators and DC-DC converters as you like.
A 8MHz Arduino with ATmega328P often runs at 3.3V, but it is okay to power it with a voltage up to 5.5V. I think you don't need to use a regulator for 3.3V. Or is it the power regulator on the Arduino board itself ?
Do you really need the 12V for the piezo ? A toneAC library will double the volume. And perhaps some mechanical construction or another piezo will make it louder.
https://bitbucket.org/teckel12/arduino-toneac/wiki/Home
Koepel:
Yes, as long as the batteries supply enough current, you can add as many voltage regulators and DC-DC converters as you like.A 8MHz Arduino with ATmega328P often runs at 3.3V, but it is okay to power it with a voltage up to 5.5V. I think you don't need to use a regulator for 3.3V. Or is it the power regulator on the Arduino board itself ?
Do you really need the 12V for the piezo ? A toneAC library will double the volume. And perhaps some mechanical construction or another piezo will make it louder.
teckel12 / Arduino toneAC / wiki / Home — Bitbucket
Well, I want to add regulator that can squeeze every drop of battery juice, there is one out there that can supply 3.3v even when AA battery drops to 0.8V, cannot remember regulator name, but that's why I want it, to stretch power supply as long as possible. I may drop this idea, but atleast right now on paper I want it.
The piezo I want to run off 12v because I just experimented with it and it seem to be the loudest at 12v, this project is a small battery powered device that monitors some stuff and can sound an alarm, but the key is that alarm I want to be ear-piercing loud, the ony way I figured that is to feed it with 12v, if you can suggest other way to make it super loud yet compact please tell me, I'm looking for most effective way to make it.
I will look into toneAC library now, have not heard of it, thanks for suggestion.
I would stay away from step up on batteries, 100%. I would use 9 v battery and then use that to drive alarm and then voltage regulator to step down to 5v or 3.3 or whatever.
I think the problem with not having enough sound with your whatever voltage is just the design of your alarm. A 9v battery powered smoke alarm can wake up whole street. Also lot of piezo buzzers are designed with tuned parallel inductors to drive the piezo not just directly. If I may suggest, there are already premade piezo buzzers that scream like no tomorrow with just having power to them, not needed to be driven with signal. But always use larger transistor 60v or more to switch it on, don't use arduino directly or the back spike from inductor will fry it.
Oscarko:
I would stay away from step up on batteries, 100%.
Why is that then? I see no reason to avoid them and have used them many times myself.
But always use larger transistor 60v or more to switch it on,
Most transistors have a 60V rating at least. I have not seen a lower rating on a transistor since the days of germanium transistors.
don't use arduino directly or the back spike from inductor will fry it.
No - the back spike from an inductor is suppressed by a reverse biased diode, which must always be used even if you are using a transistor. The reason to avoid using the output directly is that you will damage the output pin if you draw over 40mA of current from it.
I would use 9 v battery
Those small 9V batteries called PP3 used for powering smoke alarms should be avoided on all Arduino projects because the current you can draw from them is small and they don't last long.
I'm not a fan of 9v batteries for their price and capacity, so I solid on powering it either with 3AA batteries or 4AA batteries, it will however be a 3.3v atmega chip setup.
The best result I had so far is by using constant tone piezo and the way it works is the higher the voltage the louder is the tone that is how think step up converter will help me to get those 12V for piezo, I'm thinking to switch it on with mosfet.
I am very curious how inductor coil helps piezo to be louder, can you please show me few schematics how to make that happen, I really want to try it.
Grumpy_Mike:
Why is that then? I see no reason to avoid them and have used them many times myself.
Efficiency. You are losing up to 20-30%. When you go down you are typically losing only 5%.
Grumpy_Mike:
Most transistors have a 60V rating at least. I have not seen a lower rating on a transistor since the days of germanium transistors.
Really? Most of the general purpose transistors are 40V, you can easily fry it with piezo+trafo.
I use and recommend Pololu's step up (boost) regulators. You can power an entire project from one or two NiMH AA cells. They are very tolerant of abuse and total discharge (unlike LiPo batteries).
A properly chosen inductor forms a resonant circuit with a piezo disk and can have quite a large voltage swing. Search google images for "inductor piezo driver" for lots of example schematics. In this case you must use a driver transistor with Arduino, or you will destroy the port pin.
Most typical piezzo sirens are like this:
There are also commonly used small transformers with 2 secondary winds (they actually use real transformer but only use the secondary side) Those are the real big screamers. The transformers are really tiny, maybe 1/2inch^3.
You can open some water level alarm or other junk (look in thrift store) and you will get the piezzo with matching transfiormer. You may even get the whole siren circuit. But still the best is to simply buy a buzzer - that has all the components inside and you need only power. Switch it with transistor and you are done.
jremington:
I use and recommend Pololu's step up (boost) regulators. You can power an entire project from one or two NiMH AA cells. They are very tolerant of abuse and total discharge (unlike LiPo batteries).
Thanks for pointing at this, these indeed look smarter than the run of the mill ebay step ups.
But you also may see the flaw of this idea I was pointing at previously, right in the chart there. Some of them have efficiency as low as 70% . Hence I would still recommend start with higher voltage batteries and just go down. The pure step down efficiency is far higher typically in 95%+
Some of them have efficiency as low as 70%
And some significantly higher than 70%.
This chart, showing step down regulators with efficiency as low as 70%, suggests that you have an overly optimistic opinion of them.
In any case, the quoted efficiency is a range. The actual efficiency in a given circuit depends on the input/output voltage differential, the input/output currents and design factors.
Yeah, but I think this, as so often here, went the way of XY problem. The real problem of the OP is not step up or step down (problem Y) that he may like or not, the real problem he has is inefficient buzzer design (problem X) that he tries to solve by throwing up a step up board. Yes sure, it is a one of the way to avoid solving the real issue. There are many buzzer designs that will deafen you even with 3V. I think that is the best way to handle this.