Batteries aren't enough to drive speakers...?

transistor drive speaker

I built a simple alarm circuit using IC555. The IC555 oscillations switch a BJT transistor, which has a speaker between the voltage source (4 batteries AA, to give 6V to the circuit) and the collector.

Even though the speaker is not turned on constantly, but just a few times in a day, after a couple of days the speaker started to have less volume. So I disconnected the batteries, and a little while after I connected them again, and the speaker started to sound loud again, but just a few times, and again the volume started to drop. So, the batteries are almost "dry", just after 2 days of using the alarm.

I talked about some problems caused (maybe) for this "battery fast voltage loose" in the last posts of a previous topic I made:



Can somebody tell me if the problem is how a connected the circuit (if batteries are supposed to handle a speakers load)?

Or if the problem is that batteries CAN'T HANDLE a speaker.

I built the circuit to give near 350 mA to the speaker, so it's sound is low but enough to hear at 2 or 3 meters.

Is that amount of current (350, maybe 400 mA) too much for 4 batteries to "keep alive" for many days ???

Thanks for any help.

See you later.

555 oscillator drive speaker

I hope you are not using a PNP transistor...

/Rambo

battery speaker driver circuit

No, is a NPN transistor.

Series: 2SC008 (suposed to act like the BC141-16).
Ic = 700 mA, Pd = 800 mW.

But I have the 4 batteries (6 V) feeding the whole circuit:
- four IC555
- five transistors (just two for the speakers, the other 3 are for AND and NOT behaviour, using 1 MOhm resistor for those to transistors).
- two speakers (but each turning ON one at a time, trying to not use a lot of the batteries).

Was useless trying to have the alarm working for a long time just using 4 batteries?

Will I have to build a Power Supply for the circuit ?

Thanks for any idea and suggestions.

using batteries with speakers

A schematic diagram of some sort would help us to help you.

/Rambo

can i use mah 1500 instead of mah350

Enrique15 said:

No, is a NPN transistor.

Series: 2SC008 (suposed to act like the BC141-16).
Ic = 700 mA, Pd = 800 mW.

But I have the 4 batteries (6 V) feeding the whole circuit:
- four IC555
- five transistors (just two for the speakers, the other 3 are for AND and NOT behaviour, using 1 MOhm resistor for those to transistors).
- two speakers (but each turning ON one at a time, trying to not use a lot of the batteries).

Was useless trying to have the alarm working for a long time just using 4 batteries?

Will I have to build a Power Supply for the circuit ?

Thanks for any idea and suggestions.

Click to expand...

make 'mAh'-budget to see how much quisent mode and alam mode
take from batteries per day or so.


even low mA drawing from batteries in quisent mode give couple
mAh every days and draw down batteries.


350 mA on AA-size batteies is pretty high load and long before
batteries is emty, is internal resistance incrase after capacity
goes out and voltage goes low on high load situations.

if battery voltage goes to half (3 Volt), is have same internal
resistance inside batteries as load resistance

in practical you have only around 1/4 capacity in batteries
for 350 mA load and usabla voltage, compare to low load
around 20 mA.

AA-size batteries have around 1000 -1500 mAh capacity,
but only around 350 mAh in beginning time usable
for high load.

(and NiMh have 650 -750 mAh - but can give
350 mA constantly to near emty batteries without voltage drop
- NiMh and NiCd have much lower internal resistance and last longer
on high current load compare to akaline batteries )

if you using D-batteries - is load situation are
much better

(and NiMh-type can goes from 4 Ah to 10 Ah)

---

important factor to low power comsumtion but still
high level of loud is using of effecient loudspeaker
and better modulation than squarewave.

(and check is not for much ineffecient DC-current
throught speaker - you is only intrested part of wave
i giving hearing sound, not intrested part of wave only
giving heating speaker coil and transistors... try using capacitans
in serial on speaker and decrase value to small affecting
on loud and measure current load)




'perfect' loadspeaker give 112 dB/m^2 sound on 1 watt/m^2
power. very good sensivity speaker (exponetial horn etc.)
can give around 100 -105 dB on 1 m^2 area for 1 Watt input
power.

350 mA and 6 Volt give a 2.1 Watt, even if drivers give
50% effecience you give around 100 dB (disco-sound level)
if using right loudspeaker on actual frequency span.


piezospeaker with horn load can give good
sensivity - check is on burglaralarm company,
this has different types on siren or buzzers etc.

voltage drive speaker

Thanks a lot Xxargs for the explanation.

Some comments:

important factor to low power comsumtion but still high level of loud is using of effecient loudspeaker and better modulation than squarewave.

Click to expand...

piezospeaker with horn load can give good sensivity

Click to expand...

Unfortunately, in the electronic shops in my city, they don't sell such specialized things as piezospeakers. The only sell CAR and TV speakers.
I bought two Television speakers, 5 Watts 8 Ohm, each (small ones, around 2.75 inches of diameter).

And to get enough sound to hear from around 4 to 5 meters far, using this 4 AA bateries, I had to drive the speakers with around 350 mA.


Here's my circuit schematic, so you can see how I have things connected:




And here how I implemented the NOT and AND gates:

even low mA drawing from batteries in quisent mode give couple
mAh every days and draw down batteries.

Click to expand...

So, having all this elements for just 4 batteries is too much for them (just in a "Stand-by" state) ???
I tried to have a simple circuit, and I used high value resistors, trying to use only a few micro Amperes from batteries in Stand-by state. Wasn't that enough??? Will always batteries be so inefficient ??


By the way, thanks a lot for telling me:

AA-size batteries have around 1000 -1500 mAh capacity

Click to expand...

I needed that kind of information (I couldn't get it from anywhere).

So, in my circuit (for Operational State), I should have:
1000 mAh / 350 mA = 2.85 h --> Near 3 hours of battery.

Even if I have the alarm turned ON 14 seconds each time you push the Trigger button: There's no chance that batteries will last me more that 2 or 3 days ???

Thank you very much, Xxargs, for the great information you gave me already.

I'll appreciate if someone can answer me this last questions.

See ya !

4 watts speakers is it enough sound

If it wouldn't be too much work for you it would be good to have a drawing with
the components for the timing of the 555:s also. And the pin numbers.

I'm thinking that maybe a 555 is oscillating freely and driving the speaker with
a frequency above 20 kHz, i.e. inaudible, and thus "secretly" draining the battery.

/Rambo

ic 555 speaker schematic

Hi there, Rambo.

Well, here's the schematic for the IC555 group:




As you can see, the first 555 is the one that triggers the other three.
I've tested them with a LED and a 300 Ohm resistor in each IC555 output.

In "Stand-by" (just the batteries connected to the circuit), no led light on (well, just a second, when the ICs are charging up with the battery connection).

Just after I push the button, the leds light on (and speakers start to sound, each at a time).

The first IC I have it to work for 14 seconds (the 100k Variable resistor at Maximum). The second IC sends a HIGH voltage 1 second (for the 555 at the right up corner), and falls to LOW voltage 1 second (turning ON the 555 at the right lower corner), and so the cycle continues around the 14 seconds of the first IC.

With the IC555 that drive the speakers, if I set the variable resistor to minimum, bearly gets to the "no sound level". So, thinking that they can reach a little more than 10 KHz, if they were working at Stand-by, I think I would notice.

But as I told you before, with leds I can see if there's an output or not.


So, should I give up, let aside the idea of using the alarm with batteries, and build a Power Supply Circuit ??? (Which I didn't want, thinking of a small and lite alarm)

See you later. 8)

555 drive speaker

Adding to the previows answer:

How come a mini portatil radio (using only 2 AA batteries), gives equal or even more "sound" than my alarm, and of course, lasts a lot longer than my alarm (more than a month with those 2 batteries, versus my 3-day-battery-alarm)

How can it be ??? A radio has tunner circuit, amplifiers and much more sections than my little circuit.


What am I doing wrong ???

Are the speakers the reason ?? Because they are small (as I said previously), as the size of a tweeter.
But how can the speakers be, if the mini radio has a little speaker too ?

I'm close to throw the alarm into the trash. :evil:

I'm not expert in sound dB level sourcing.
I don't know if having a 5W speaker for just using 1W is the reason. Or are speakers equal in performance, regardless the Watts they drive ??

Thanks for any help. I'll appreciate it a lot.

low voltage alarm using speaker

Well, I tested the circuit again with 4 new batteries.

And again, it last me 2 days. After that, it started to behave erronuous, randomly.
For example, this time one of the speakers started buzzing from nowhere (nobody touched the trigger button). Weird stuff like that.

So, I'll have to GET OVER the idea of not using batteries when feeding "speakers" in a circuit.


It's a pitty that SPEAKERS need too much current to produce sound.
Correct me if I'm wrong, but that's the only thing I can conclude from my experiment.


See you around!!!

voltage to drive speaker

If you have a meter, you should measure the standby current. Even if the speaker is not buzzing, the circuit may draw some current.

So, connect a multimeter in series with the battery, in 'Amp' mode, and verify the current when the speaker is turned off.

Also, there may be DC current leaking through the speaker when the switch is off. If the current is steady, the speaker won't sound, but it will draw power from the battery.

In this case, you should connect a capacitor in serie with the speaker. A polirized capacitor will do as long as you put the + toward the 555 and the - toward the speaker. Something like 100µF~330µF will do.

tv speakers arent loud enough

Thanks Big Boy for answering.

But here's a thing:

Also, there may be DC current leaking through the speaker when the switch is off. If the current is steady, the speaker won't sound, but it will draw power from the battery.

Click to expand...

How this could happen, if the transistor is turned off, as well as the IC555.

Look the way I have connected the speaker:



While IC555 doesn't have high voltage at its output, the transistor won't drive current, and so, the speaker can't "leak" current...
Or even though I believe this (as the theory says it), there can be little current passing through the transistor, even though there's no voltage at its base ???


Another thing I couldn't understand:

In this case, you should connect a capacitor in serie with the speaker. A polirized capacitor will do as long as you put the + toward the 555 and the - toward the speaker. Something like 100µF~330µF will do.

Click to expand...

Acording to the drawing above, where should I put that capacitor? Between the IC555 output and the 1.8k resistor ???

And what will it work for ??? Blocking some current that comes from the IC555 output at low voltage output ??? That's the current "leakage" you told me about?

Thanks for the help.
See you soon.

transistors to drive car speaker

Hello again.

Sorry if I'm boring you with the same topic day after day.

But, could please somebody tell me if this kind of circuit would do any difference about the batteries "dry up" ???




Or will this circuit be the same as the one I show you in the previous reply ? (the one with the speaker directly as the collector resistor).

Thanks in advance for any help or suggestions.

rambo battery

If you want to have longest service time, you should minimize the current drawn by the circuit. I think, 350ma is very high. Additionally, 555 chip required supply voltage min. 4.5V. So, it is more important for your design. I suggest you, don't use 555 in this design. You can use CMOS inverters for oscillator. And, at the output stage, use a buzzer, because it use less power and no require alternating signal, only dc. If you want to use speaker, your original circuit for output stage is ok, but you can remove R2(2.2) and increase R1(1.8k) to 10k. I hope it will help.