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Author Topic: Can I power the Bluetooth Smirf directly from a Digital Pin?  (Read 557 times)
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BTS (bluetooth smirf) datasheets says that the Average consumption is about 25mA when connected and can operate anywhere between 3.3V-6V.

DO pins give 40mA max so i should be fine but the word average scares me a little....what if there are much higher current draws for a short period? Can i use a <1k resistor to protect from overcurrent?

just wanna make sure i don't fry my boards smiley

regards - phil
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You could use two pins together....or a transistor. A transistor only costs a few cents and is 100% sure.
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unfortunately the project is already set up in such a way that its hard to even fit a small transistor in there nicely. simply re-plugging a jumper wire would be better for me...

but yes, if i can not somebody to confirm this works i will go that route smiley

thx for the input! smiley
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I'm surprised the datasheet doesn't have the maximum current draw.

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I'm surprised the datasheet doesn't have the maximum current draw.



 the manufacturer, "roving networks", does state: Low power (26 uA sleep, 3 mA connected, 30 mA transmit). However the bluesmirf board which carries the RT42 does have a power control circuit and 2 small LED's on there...who knows what they draw...hmm.

might have to go with the resistor after-all..guess ill wrap it up inline with electrical tape..lol there goes my pretty hardware design smiley-wink
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Treat it as a 30mA, 3.3V device:

1.7 V = 30 mA * 56 Ohms     (a standard resistor value, tada!)

If it uses less than 30mA the volts across it will go up a bit, but that's OK, it's good for up to 6V.

« Last Edit: March 07, 2013, 07:32:16 am by fungus » Logged

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OTOH, why do you want to power it from an Arduino pin? Most of those devices have a shutdown mode which uses very little power.


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well the reasoning is a little more complex. i am currently in the process of building a bluetooth proximity sensor to automatically lock/unlock my car doors with my android.

The bluesmirf is in master mode and tried to continuously connect to the, previously paired, android. The android runs a service that listens to that connection attempt...Tada they connect upon which the android sends a data stream which the arduino authorizes and unlocks the car door....

The reason behind wanting to turn of the Bluetooth the car is running is that the phone will not be able to sleep during this connection. So turning of the BT adapter while ignition is on terminates the connection and the phone can go to sleep ..saving battery. Once I get to my destination and turn the ignition off, the bluetooth module will reestablish the connection upon which the phone will wake up and once again send data packets letting the arduino know...HEY IM IN RANGE>...once that signal is lost..with ignition off.....Boom Doors close...

there is a possibility to kill and reestablish the connection in command mode of the bluetooth device but simply turning it on off works just as well and saves, all-tough negligible, power.

 
« Last Edit: March 07, 2013, 08:50:58 am by sgtpepperaut » Logged

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OK...I'll go back to my original suggestion then. Use two Arduino pins - double the current!
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the brain of the car control (does much more than open  doors) smiley-wink



starter module:


waterproof solid state low side switcher module:


high side switch module:



8 channel relay module:
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OK...I'll go back to my original suggestion then. Use two Arduino pins - double the current!


good idea! hopefully i have some left smiley-wink

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