Cytron Technical Forum

Hi, I have a Xbee pro S2 and a XtreamBee Board. Whenever i insert the Xbee onto the XtreamBee board, the input voltage 3.3V will start to drop from 2.3V to 2.8V and the voltage will keep changing. Anyone knows? Can I connect 5V input voltage to the Xbee??

Information on XtreamBee Board:
https://store.diydrones.com/product_p/br-0015-01.htm
https://docs.google.com/Doc?docid=0ASI4 ... bmM1&hl=en

Thank you.

May it be the 3.3V supply current too low? What's your circuit connection? You can attach here...

hellokitty9999 WROTE:Hi, I have a Xbee pro S2 and a XtreamBee Board. Whenever i insert the Xbee onto the XtreamBee board, the input voltage 3.3V will start to drop from 2.3V to 2.8V and the voltage will keep changing. Anyone knows? Can I connect 5V input voltage to the Xbee??

From the above photo, the input power selector was in the 5V position and there's a 3.3V voltage regulator. If you didnt disturb the setting, I'll bet you can use 5V directly on the Xtreme and it would step down to 3.3V to feed the XBee Pro. Without a schematic, I can only do a logical guess.

To be 100% sure, you can trace the copper and see where the Vcc of the Xbee goes to...3.3V regulator OR voltage selector. Or get a voltmeter, dont put in the XBee, connect Xtreme to +5V / GND and measure the XBee Vcc point and see if 3V3 is there. You should be able to get the datasheet of XBee from cytron main site.

Allen

Hi! thanks for the replies. The attach file is my schematic diagram. Take a look at my connection.

It surprise me to see there is still people using voltage divider concept to supply a load.

The connection shown cannot work! Why? You need to ask yourself, how to get the 3.3V from 5V using resistor ladder? Because of R1 and R2. Now, that is concept, why you measure voltage at that point, the resistance remains, so you get the correct voltage, let's assume is 3.3V. But when you connect XBee, Xbee is a load, it has resistance too, therefore it will change the effective R, thus change the voltage it get!

Think this, if voltage divider using resistor or zener diode is good, why is there voltage regulator? Why is there 7805 in your circuit in the first place??? Why don use resistor ladder to divide 12V to 5V?? Ever think of that?

Hi robosang, thanks for your reply. hmm.. instead of using voltage divider, how about use a voltage regulator that supply 3.3v??
At the first place i will use 7805 because i want the voltage from 12v drop to 5v. then from 5v to 3.3v i use voltage divider because i was thinking from 5v to 3.3v not much voltage different, that's why i use it.

Thank you.

hellokitty9999 WROTE:instead of using voltage divider, how about use a voltage regulator that supply 3.3v??

Yes, that should solve your problem. If you want to directly replace the 7805 with a 3V3 regulator, make sure it can withstand +12V DC.

Allen

Hi Allen, hmm... can i use two voltage regulator? One 7805 and 3940 voltage regulator? or any other voltage regulator can i use from 5vto 3.3v??

Thank you.

hellokitty9999 WROTE:Hi Allen, hmm... can i use two voltage regulator? One 7805 and 3940 voltage regulator? or any other voltage regulator can i use from 5vto 3.3v??

Thank you.

Of course. LM3940 is a low drop-out 3v3 voltage regulator. It only requires an input of 4.5V. I said "If you want to use one volt reg"., I would do the same as you as the +5V would be useful if I want to add some other logic chips.

Allen

Hi allen, if i use one voltage regulator, what logic chips should i use??

Thank you.