Excuse my newbness here, but:
I would ideally love to use the Arduino Pro Mini 328 (Atmega328 @ 16mHz) which runs at 5V, on the same wireless PCB with an xbee.
I haven't made a project yet running on battery power.
If I get a battery that can provide 5V to Arduino, will I need to build a voltage regulator on board to provide 3.3v to the Xbee? Will this dissipate/waste power?
Or should I just have two batteries, or is there another solution?
Thanks!
One addition - I assume if I have a battery for power, I will need to have a 5V voltage regulator on board as is. Since this will be 'regulated,' I suppose I could just use a resistor to get a regulated 3.3V supply?
Is this correct? Is this even a good idea - again, will this work / dissipate a lot of battery power?
I would ideally love to use the Arduino Pro Mini 328 (Atmega328 @ 16mHz) which runs at 5V
Definitely the best option for doing this would be a 3.3v arduino to avoid losses through regulating or using a resistor. If it is battery powered then all of this can add up to quite a large difference.
Mowcius
I would ideally love to use the Arduino Pro Mini 328 (Atmega328 @ 16mHz) which runs at 5V, on the same wireless PCB with an xbee.
I make a board that combines an Atmega328 (with Arduino bootloader) and
an XBee. See http://wiblocks.luciani.org/ZB1/index.html
I run the Atmega and XBee off of 3.3V and use a 3.7V Li-ion battery. Converting
3.7V to 3.3V has an efficiency of almost 90%. This also simplifies the system
design since only one system voltage is required.
(* jcl *)
www: http://www.wiblocks.com
twitter: x.com
blog: http://luciani.org
Two questions:
If it turned out to not be big deal to me to have two batteries, would there be any problem with powering the xbee off a lith ion battery going to a 3.3V voltage regulator, and the Atmega328 off of one going to a 5V voltage regulator?
It's possible that I will need the 16MHz speed, and I also have some LEDs on board which take 3.2V per channel, so it wouldn't actually be so bad to have that 3.3V battery anyway, since I could use small resistors and dissipate less power to them, right?
On an unrelated note, jluciani, your board looks excellent!
Since I will eventually be building something similar, I am extremely curious how you were able to do the surface mount soldering. I have never tried it, but want to design my board similarly (especially having the FTDI chip so I don't have to keep using this Sparkfun breakout!)
Did you do it by hand, or could you describe how you did it?
Also, it looks like you have two 3.3V voltage regulators?
On an unrelated note, jluciani, your board looks excellent!
Thank you.
Since I will eventually be building something similar, I am extremely curious how you were able to do the surface mount soldering. I have never tried it, but want to design my board similarly (especially having the FTDI chip so I don't have to keep using this Sparkfun breakout!)
Did you do it by hand, or could you describe how you did it?
The FTDI chip is not difficult. I mostly do these by hand and I use a lot of flux, After the corners are tacked down I flux all the leads and then run the iron tip and wire solder along the leads. With the flux and proper footprint design the solder flows properly.
I use solder-wick to clean-up the occasional solder bridge. You need to give
the board a thorough cleaning.
If you stick to 0.5mm pitch (or greater) ICs, 0805's (or larger) and only use
packages with leads you should not have a difficult time. You do need
a good iron and a magnifier. My tools recommendations are in my FAQ at
http://wiblocks.luciani.org/FAQ/faq-index.html
Also, it looks like you have two 3.3V voltage regulators?
That is correct. The board was designed so that it could be cut into two functional
boards. If you plug an FTDI adapter into the right half you can use the second
regulator to power the XBee. Most people use it as a single board and don't
populate the second regulator.
I take feature requests for these boards. If there is a peripheral you would like
to see or a change made just send me an email.
(* jcl *)
Excellent, thank you for the advice jluciani. Do you have any thoughts on my previous post about using two batteries?
Also, I am hoping to use the TLC5940 from TI on my board:
Do any of the form factors listed for that part meet the pitch and lead specifications you mentioned?
I wouldn't use two batteries. I would do a single battery 3.3V system.
I built a little LI-ion battery charger + regulator that mounts under
any of my boards --
http://wiblocks.luciani.org/not-quite-ready/LI-ION-index.html
For the TLC5940 you would be best off with DIP. Both of the SMD parts
have thermal pads which could be difficult for you to solder.
If you do a hot-plate or a toaster oven soldering setup then I would
go with the PWP package. You need to use the land pattern recommendation
in the datasheet to get the proper cooling.
(* jcl *)
Yes - cooling could be an issue. I am running 3 watt LEDS with them: RGB LEDs which take 350mA per channel.
In order to sink this current with the TLC, I am actually setting the TLC to output 120mA per pin, and connecting 3 output pins to each channel of the LED. In software, I will scale the three outputs to add up to the appropriate current between 0 and 350mA.
Since I am using 9 RGB LEDs, I will have 9 TLCs. Do you think I will need any additional cooling for the TLCs if I use DIP packages? I already have a thorough solution for heat sinking the LEDs themselves.
Since I am using 9 RGB LEDs, I will have 9 TLCs. Do you think I will need any additional cooling for the TLCs if I use DIP packages? I already have a thorough solution for heat sinking the LEDs themselves.
Not sure. You need to go through the thermal resistance numbers.
There are per pin and per package limits. On the DIP the heat conduction is through
the leads and package so you need to design the copper pattern appropriately.
I use MOSFETs on my current sink design --
http://wiblocks.luciani.org/not-quite-ready/ZB1-ISINK-index.html
The LEDs in the picture are 3W whites.
For 3W LEDs the FETs in this design do not require a heatsink.
The FETs can do 30A per channel. The connectors are rated for 10A.
For an LED application the practical limit (due to cooling) is around
2A per channel.
(* jcl *)