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1  Using Arduino / Networking, Protocols, and Devices / I2C - Distance Limitations / Slave to Slave on: December 02, 2013, 01:14:52 pm
what is the longest distance you can run an I2C BUS wire before you ran into trouble? will using twisted cables help?

in my case i am looking to wire about 4-6 Arduinos over about 12m (36ft). There are some beefy  10A DC motors in the proximity but i can route the signal wires as far away as possible.

Another quick question since I am very new to I2C: can slaves talk to slaves? or just master-slave1, master-slave2...etc. ..since its a bus i hope that slaves can communicate but I never tried nor found a source.

thanks - phil
2  Using Arduino / General Electronics / Re: How to sink low voltages? on: March 09, 2013, 04:22:21 pm
Having that connected all the time  would send constant signal to the cars computer to lock the doors.... Which it will gladly repeat over and over again..
The cable needs to be not connected to anything for no action.... There are three discrete states here. Not two smiley-sad
3  Using Arduino / General Electronics / Re: How to sink low voltages? on: March 09, 2013, 03:52:29 pm
Well the other end is coming from the car controller. Maybe I didn't express my problem well enough but your solution seems to always leave the cable to ground with the 470ohm resistor in between which is not what I want.
Lets try again.
I have a wire in my hand coming from that car controller at 0.7V to ground. When u ground that wire doors open. When I put a 470ohm r in inline then ground the doors lock.
When I have the wire in my hand nothing happens (duh)
4  Using Arduino / General Electronics / How to sink low voltages? on: March 09, 2013, 02:26:24 pm
Ok i am a little stuck on this one some help would be appreciated:

i have a 0.7V source that is coming out of another circuit (car controller) that needs to be sinked. If wire is simply connected to ground the doors will lock. If the wire is connected to a 470 Ohm resistor the doors will unlock.

I have tried an optocoupler but it appears that even under saturation conditions the doors will only UNLOCK. I am assuming that the cars controller is simply reading the voltage on that wire and locking unlocking depending voltage on that wire.

How can safely (protecting both circuits) have a digital pin control this sinking current (which is less than 10ma)...

Can i sink them directly into the DPs? is there a way i can only use one DP (pwm?!)? transistors didnt work either ...2n222  transistors but the doors would only UNLOCK...meaning the voltage is not dropped enough?

any help is appreciated.
5  Using Arduino / General Electronics / Re: Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 09:04:12 am
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

6  Using Arduino / General Electronics / Re: Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 09:02:17 am
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:
7  Using Arduino / General Electronics / Re: Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 08:49:20 am
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.

 
8  Using Arduino / General Electronics / Re: Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 07:16:50 am
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
9  Using Arduino / General Electronics / Re: Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 07:08:02 am
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
10  Using Arduino / General Electronics / Can I power the Bluetooth Smirf directly from a Digital Pin? on: March 07, 2013, 06:16:59 am
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
11  Using Arduino / Networking, Protocols, and Devices / Continuously Get Connection status of BT smirf. on: March 02, 2013, 02:13:34 pm
hi guys,

i recently got my RN42 (bluesmirf silver) bluetooth module. I was wondering what the best option would be to get the connection status in a set interval.

Goal here would be:
If bluetooth smirf connects to my phone (and only to this device!)...have arduino do action1.....once i leave the proximity and bluetooth disconnects do action 2 and run that proximity check every couple of seconds or so.

i am looking into the $$$ command sets from this http://www.sparkfun.com/datasheets/Wireless/Bluetooth/rn-bluetooth-um.pdf manual but i am not sure going into command mode very couple of second is a great idea...perhaps its not even possible.
12  Using Arduino / General Electronics / Re: Listening to 12V Signals with Optocouplers? on: February 14, 2013, 10:31:12 pm
and the updated schematic for people to reference:
13  Using Arduino / General Electronics / Re: Listening to 12V Signals with Optocouplers? on: February 14, 2013, 10:25:51 pm

well i certainly didn't mind the cents that the resistor cost more the soldering of the board. anyways i agree with whats being said here i just wanted to understand the fundamentals behind it.

thx for all the input.

anyways circuit is done and its right on the sweetspot:
10mA a Pop for a total of 60mA draw at 12V...woho smiley


still have to get some experience soldering but it worked out okay..


14  Using Arduino / General Electronics / Re: Listening to 12V Signals with Optocouplers? on: February 14, 2013, 05:12:27 pm
Quote
this is the alternative and would save a couple of resistors... (need to listen to more than 3 inputs...)

No, that way would suck.

Lefty

figured as much....could you give me some input as to why "it would suck" ..just trying to get my EE straight smiley


It's simply an invalid circuit.

Lefty


this kinda felt like:



this is one lively forum! Thank you. Ill get on soldering that up and report back with some pictures smiley
15  Using Arduino / General Electronics / Re: Listening to 12V Signals with Optocouplers? on: February 14, 2013, 04:56:35 pm
Quote
this is the alternative and would save a couple of resistors... (need to listen to more than 3 inputs...)

No, that way would suck.

Lefty

figured as much....could you give me some input as to why "it would suck" ..just trying to get my EE straight smiley
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