# Strange Bluetooth Pro mini 3v3 Behavior, Insight needed

**URL:** <https://community.sparkfun.com/t/strange-bluetooth-pro-mini-3v3-behavior-insight-needed/20106>\
**Category:** Wireless & IoT\
**Created:** [March 28, 2011, 8:36pm UTC](https://community.sparkfun.com/t/strange-bluetooth-pro-mini-3v3-behavior-insight-needed/20106 "2011-03-28T20:36:46Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![erikg](https://avatars.discourse-cdn.com/v4/letter/e/91b2a8/32.png) [@erikg](https://community.sparkfun.com/u/erikg)\
**Post date:** [March 28, 2011, 8:36pm UTC](https://community.sparkfun.com/t/strange-bluetooth-pro-mini-3v3-behavior-insight-needed/20106/1 "2011-03-28T20:36:46Z")

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Hello All.

I am having some issues with my Pro Mini 328 3v3 and a BTM-182 blue tooth module.

The main issue i am having is that i cant connect to the BT adapter with my computer when its powered by batteries.

I have 3, 3v CR2032 button style batteries connected to the raw input on the arduino.

When i try to connect powered by batteries, i cant.

however when i plug the 3v3 FTDI break out board, i can connect effortlessly. If i switch over to batteries and disconnect the FTDI,

I am able to get an output for about a minute and then things go haywire.

It drops the connection and i cant reconnect unless i plug in the FTDI.

I was looking at the VCC and ground connections with an OSCOPE and found that just before it breaks connection, there is significant noise on the Oscope.

I have a good feeling that is why i am loosing the connection but i dont know how to go about correcting it.

A brief overview of the project.

I am sending accelerometer values over BT and viewing on hyperterminal.

The BTM is still set to factory specs, 19200 baud, 8n1.

I also cant seem to make any changes to the BT module.

I am unsure how to do it.

Do i write a program to send the AT commands over, or should i use Hyperterm?

Thanks all.

-Erik

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**Author:** ![pcrom](https://avatars.discourse-cdn.com/v4/letter/p/47e85d/32.png) [@pcrom](https://community.sparkfun.com/u/pcrom)\
**Post date:** [March 30, 2011, 11:10am UTC](https://community.sparkfun.com/t/strange-bluetooth-pro-mini-3v3-behavior-insight-needed/20106/2 "2011-03-30T11:10:25Z")

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Bluetooth modules can draw much current (~80 mA), probably your battery is not able to supply this current and drops the output voltage. You could try to put a (super)capacitor in parallel to the battery or use a larger battery that can provide this current.

For software, that all depends on what you want. If you use Bray’s terminal (google) you are able to send a command every x seconds which may be a good start

Greets

pcrom