Go Down

Topic: Bluetooth module HC-05 not working with 9V battery supply to Arduino Mega (Read 2672 times) previous topic - next topic

GoodDeeds

I am new to Arduino and have a project involving Arduino Mega 2560. I am using the bluetooth module HC-05 to send serial commands from an Android device to the Arduino. The working is as expected when the Arduino is powered via USB through a laptop. However, on connecting a 9V battery to the Arduino, the bluetooth module does not even light up. The battery model is Hi Watt 6F22. All other components connected to Arduino work with the battery, except the bluetooth.

The connections are:
Bluetooth - Arduino
1. VCC - 3.3V
2. GND - GND
3. TX - RX
4. RX - TX through a voltage divider. (To turn 5V to 3.3 V)

The other components are signal pins of 7 ultrasonic sensors, 5 servo motors and 4 12V DC motors. All the motors receive their power supply from outside the board. The sensors are powered through the 5 V pin.

Searching online, the current rating of the battery should be sufficient to power the module. Am I missing something?

Thank you for any help.

Nick_Pyner

The working is as expected when the Arduino is powered via USB
 the battery should be sufficient to power the module. Am I missing something?
Yes, it isn't.

You also need to be more forthcoming about the HC-05 you are using. VCC @ 3.3v is not usual practice, although this is probably not the cause of your problem.

deep4U

Did you ever get it solved?
Facing the same problem here with an HC-05 and DC power jack, works with USB

Nick_Pyner

Did you ever get it solved?
Two months of deafening silence suggests

1. No
2. Yes, but the problem was so stupid the OP didn't want to raise it again.


habanero

I have an Arduino Mega-based project that uses an HC-05 (as well as an ESP8266 ESP-01 and a bunch of other boards and circuitry including weather sensors), and it works fine either via USB or DC power. I don't think I've ever connected a 9V battery to it, but assuming it had enough charge on it, I don't see why it wouldn't work, for a short while at least, unless this particular project drew too much current even for a fresh alkaline 9V. Otherwise, might be a bad Mega board. Does it work properly otherwise?

Nick_Pyner

too much current even for a fresh alkaline 9V.
Which is quite likely
Quote
Does it work properly otherwise
Which has already been answered in the affirmative. Mr GoodDeeds has even identified that the bluetooth is the last step on the path to certain doom.
The working is as expected when the Arduino is powered via USB ...... All other components connected to Arduino work with the battery, except the bluetooth.

habanero

For the hell of it, I just tried powering my project, a weather station, using just a 9V battery. And not even a totally fresh one, as it registered 8.95v on my multimeter. Yet it worked, including the HC-05, whose output I was able to see on a PuTTY window. And this isn't just some simple device with a couple of sensors. There are quite a few things attached to it, all running off this one slightly underpowered 9V alkaline:

Arduino Mega
2x16 LCD w/backlight on, connected via I2C board
RTC module
MicroSD card module w/card inserted
ESP8266 ESP-01 WiFi module
HC-05 BT module
BMP180
In & Out DHT22s
In & Out DS1820Bs
In & Out LDRs

So, it's not the battery. At least, per se, although they may have been using an old one, or a zinc oxide one. Or, perhaps, their project has some bad wiring or circuitry or a design flaw, or the Mega board is faulty somehow. But, I doubt it's due to using a 9V battery. I've pretty much just proved that, unless it's powering a motor or something else that needs more juice.

habanero

Btw, unrelated to this topic, but you've been here a while, and I haven't, and I seem to be having a hard time getting my questions addressed in several threads I've posted in this and other forums here. I've participated in many other site forums over the years, some technical, some not, and have generally had no problem becoming part of the "community", whether ongoing or occasionally, getting responses, and engaging in discussions.

I don't spam or cross-post (unless I realized that my first post was in the wrong forum, and say so) or troll or harass or whine or do any of the other things that generally get your ignored or banned online. And, I try to contribute, when and where I can, with my own knowledge and insight, as I've tried to do here, in this thread and in others.

But here, it seems like I'm invisible, and almost none of my questions get responded to. Is this the sort of place where you have to REALLY know what you're talking about and not ask non-expert (i.e. stupid) questions, and participate on a very regular basis, to be taken seriously? There just seems to be a somewhat passive-aggressive you either belong her or you don't vibe that I've noticed. Just wondering. I mean, I don't even get so much as a "That's a stupid question, newbie!". Literally NOTHING.

When I first joined a year or so ago, I posted a bunch, and did get some responses. I don't recall how it went that well, but perhaps I ticked off a bunch of regulars and have since been put on a site "bozo bin"? And this is a site for tinkerers and makers, hobbyists for the most part having fun, not "serious" engineers working on multi-million dollar projects, so you'd think it would be more inclusive.

Sorry to whine, this one time, but I'm at my wit's end trying to get help here on various projects I'm working on, all of which are just for my own enjoyment and use, nothing commercial.

Nick_Pyner

For the hell of it, I just tried powering my project, a weather station, using just a 9V battery. And not even a totally fresh one, as it registered 8.95v on my multimeter. Yet it worked, including the HC-05,........I've pretty much just proved that
I believe the HiWatt OP used is a cheap brand, but I submit the only thing you have proven is that you got lucky, and I can pretty well guarantee you that your luck won't last long. It's old school, but I understand a 9v PP3 is designed to deliver at about 20mA max, which is barely enough to drive a LED.  The nett result is that, if you insist on using one, you deserve all the grief you get, and hence as a matter of principle they are best avoided. There is clearly nothing wrong with OP's intent and how he goes about it, except for the change of power supply. If he was doing something else that was stupid, the laptop probably wouldn't deliver either.

You will notice that this forum is full of people having grief with battery power when everything works fine with USB or a wall wart, and the 9v PP3 is the usual villain. This is because nobody understands the correlations between amps, volts, and volume, and I guess it is no surprise that Tandy Corporation built their business model around selling 9v batteries to suckers.

The above is not helped by the fact that Arduinos are not famous for their electrical efficiency, you only have to feed one from a 9v wall wart and put your finger on the voltage regulators to get a good view of that, and wonder what it's all about. Much the same can be said for the HC-05 as well.

I can't comment much on the other. People do do stupid things and start threads with the title "Help!!!" with no code included, but I don't think there is a "bozo bin", even though I have been called one a few times. We all learn, that is what the forum is for, and at least you can put a sentence together, which must be an advantage.

 


habanero

I've actually powered a number of Arduino projects with 9V alkalines, and they've lasted for hours to days, including a shield to drive an 8x8 RGB LED array, using 4 595 shift registers and 24 resistors, and it ran on a 9v alk for several hours.

Some used the Uno, others a Nano or Pro Mini. Today's experiment was with a Mega (albeit for just a minute). But although not designed for it, they can certainly put out more than 20mA, albeit not for long.

Most alks are rated at 500-600mAh, so you could theoretically pull 100mA for 5-6 hours, or 500mA for an hour or so. Of course that's assuming a perfect depletion curve and not a real-world one.

But, again, they can clearly put out well over 20mA, or else they wouldn't be able to power a Pro Mini let alone a Mega, and they can do both. This is not to say that they're a smart way to power an Arduino project, but for ones used only occasionally and briefly, and without too much draw. they'll certainly work.

So, again, unless this project has a ton of stuff that draws power, and the BT put it over the edge, I doubt it's the 9v battery. Perhaps it's the 3.3v connection for the BT's power?

Nick_Pyner

This is not to say that they're a smart way to power an Arduino project,
Indeed, and in the event of a sudden failure to proceed, they are the first place to look, while their relegation to the smoke detectors where they belong is a regular fix. I have already commented on the 3.3v to HC-05, but OP may be using a bare board. I note the deafening silence from OP.

habanero

Yeah, I know, nothing beyond the first post, so we're basically trying to solve a problem that may no longer exist or be relevant. The nice thing about 9V is that for simple projects that need to be moveable and don't have much power draw, they cut down on clutter and make things easier to test.

Like, I used one to test some remote weather station nodes I built that connect to the base station via RF. The finished nodes will probably be powered by either an adapter or solar w/rechargeable battery, but for testing it was simpler to use a 9V so I could move it around to fine-tune transmission code.

In fact, the lower power actually made for a good worst-case test scenario. If I can design a node robust enough to work off a not so fresh 9V, it should be more than reliable with a more robust power supply.

Nick_Pyner

In fact, the lower power actually made for a good worst-case test scenario. If I can design a node robust enough to work off a not so fresh 9V, it should be more than reliable with a more robust power supply.
Indeed, but if you are smart enough to take that approach, and know what the problem is most likely to be when it arises, you won't be posting here about it, wondering what the hell happened. There is a whole school out there, skilled in the arts of battery hocus-pocus, off-board regulators, sleep modes, no LEDs, minimal peripherals, etc. etc., who may actually find the PP3 quite satisfactory, to the point even where its convenience makes it worthwhile. I don't suppose Mega users are much in  attendance there.   

habanero

I haven't been doing this or posting here long enough, nor am I enough of an Arduino or electronics expert, to be part of this de facto community of "power power users" that you speak of. Plus, even if I were, I'd likely still have the occasional thorny problem I might want to throw out here to see if anyone has a clue. Some things you solve on your own, because you can and it's fun, some you pass by your expert friends, and some you throw out here, because it's a nice community sort of thing to do, and you never know what it might lead to. I'm betting that even experimental nuclear physicists come here sometimes, to hang out (pseudonymously).

As for the Mega, I had to use it because the Uno just didn't have the memory or hardware (especially serial ports) to handle all the components I was throwing into this project. I'm sure that there's an analogous group of user to power misers who are expert memory misers, who could have made my project work on an Uno, and I may someday try to do that. But at $10 at the local Microcenter for a Mega clone, it wasn't worth the bother. Although, redesigning it to work around a NodeMCU board might be an interesting next project...

Nick_Pyner

I use Mega for the same reasons. There is a bit of a school of memory misers but, in the datalogging arena, it doesn't take that much to put the Uno out of the game, and the best advice you will ever get from a memory miser who knows what he is doing, would be to get a Mega. Ironically, I was originally spooked into getting a Mega because I was concerned about the extra software incurred by using bluetooth, which was nonsense. I have just been thinking about getting a NodeMCU for a remote installation. This has just been prompted by a post about a nice cheap LCD on SPI . 

Go Up