DS1307 and ADXL335 using 3.3v

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daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

Ok, I've just looked at the parts list for the DS1307 and a pair of 2.2K resistors come with it. I'm just a little confused as the tutorial for the TSL2561 Lux/Light sensor says to remove the DS1307 pull up resistors if using the sensors concurrently, which lead me to believe that you needed different values for different voltages. I take it when running multiple I2c devices you just have one pair of resistors?

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

The reason for removing them is because the DS1307 pullups are to 5v and the TSL2561 is a 3.3v device. You can use a 5v device with 3.3v pullups, but 5v pullups will damage a 3.3v device.

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

I understand, that makes perfect sense now. Still need to investigate the I2c protocol as you probably guessed I'm quite new to it.

Thanks again for the support :)

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

Here's a good review of how it works electrically. http://www.i2c-bus.org/i2c-primer/

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

Cheers :D

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

I've just set my Arduino 3.3v Pro Mini up and powered it with a 3.3v FTDI basic and followed my fritzing diagram in a preceding post. I've a few questions, firstly, which I guess is obvious that when I test for voltage on the raw pin I get zero. Also, I take it I don't power the raw pin as well as the power from the 3.3v FTDI basic in order to get 5v for my DS1307?

I've provided a picture to illustrate:

Image

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

Looks like VCC on the FTDI header bypasses both the Raw pin & the regulator on that processor. I'm not familiar with the FTDI adapter you are using. Does it have a breakout for the 5v it is getting from the USB port?

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

I did try and purchase the your FTDI adapter but it wasn't in stock from my UK supllier, so had to go with this Sparkfun one.

It has this on the back:

Image

I do actually have the official 5v Arduino FTDI adapter also if that helps

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

Looks like you could solder a jumper to that pad labeled 5v and power the DS1307 from that.

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

Ok, what about my 5v Arduino FTDI, will that act the same as the Sparkfun adapter?

http://arduino.cc/en/Main/USBSerial

I'm just a bit reluctant atm about connecting that one to my 3.3v board.

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

The 5v FTDI adapter is going to have 5v on VCC. That would not be healthy for your 3.3v micro.

daz1761
 
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Re: DS1307 and ADXL335 using 3.3v

Post by daz1761 »

Sorry for all the questions!

Btw, I'm just in the process of testing my ADXL335 by plugging the 3.3v output into the 3Vo and it seems to be operating okay :D

jreit313
 
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Re: DS1307 and ADXL335 using 3.3v

Post by jreit313 »

Hi I tried connecting my ds1307 to an arduino pro mini 3.3v and could not set the time. I had removed those resistors as instructed but it didn't help. I didn't understand why adafruit said it worked for a raspberry pi that's also 3.3v supply.

Do we know for certain that when plugged into USB, the raw is 5v for the rtc? I would like to avoid soldering and unsoldering.

Any other suggestions/input is greatly appreciated!!

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newbie3
 
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Re: DS1307 and ADXL335 using 3.3v

Post by newbie3 »

Hello,

Working on a project using, neopixel/gyro/ ADXL 335 accelerometer/vibration motor inside. Can a Lipo battery be used to power an arduino mini, while it was being charged? Making an object runs on lithium battery but I want to make it rechargeable.

Many Thanks,
Newbie

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adafruit_support_bill
 
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Re: DS1307 and ADXL335 using 3.3v

Post by adafruit_support_bill »

@Newbie - better to start a new thread for your topic: http://forums.adafruit.com/posting.php?mode=post&f=25

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