<div dir="ltr"><div>A couple of thoughts:<br></div><div>* You can easily power the Teensy via the RPi pins if it is only the Teensy and nothing beyond that. I power both a sensor board with a couple I2C devices I power directly off of the RPi pins (3,3v) and an Arduino (5v), as well as a few LEDs, directly off of the RPi power pins on P1. I don't know what the maximum power rating through that connector, but it is enough for just the Teensy.</div>
<div><br></div><div>* While you can use the same battery for both your electronics and your motor, you may have problems with power spikes from the motor being fed back into your other electronics and causing issues. If you have the space and weight rating for a second battery, I would definitely recommend that.</div>
<div><br></div><div>* For powering the RPi, I have found that the external cell phone chargers make excellent battery packs. They are lightweight, and most have a power on/off button and power on light built in and they can power the RPi for hours. I have a 5000mah unit that I use for 5+ hours without an issue, and Ruth Suehle (of the RPI Hacks book) has reported she uses a 12000mah unit for 12+ hours. You have USB power out and you can use a short USB power cable to power the RPi, and then use the RPi to power the Teensy and a few other sensors - so all your electronics will be one rechargeable pack. You don't even need to remove the pack to charge it as it has it's own charge plug in the side. This is what I have used on my nearspace balloon project, plus a few other RPi test projects. Here is one as an example of the battery pack:</div>
<div><br></div><div><a href="http://www.amazon.com/Poweradd-trade-Pilot-Dual-Port-Blackberry/dp/B00B688RZA/ref=sr_1_5?s=wireless&ie=UTF8&qid=1390237990&sr=1-5&keywords=5000+mah+battery">http://www.amazon.com/Poweradd-trade-Pilot-Dual-Port-Blackberry/dp/B00B688RZA/ref=sr_1_5?s=wireless&ie=UTF8&qid=1390237990&sr=1-5&keywords=5000+mah+battery</a>)</div>
<div><br></div><div>* For the WiFI dongle, you *may* be able to get away with powering it directly from the RPi. Many have reported a problem, but others have reported it working. The number of permutations of WiFi dongles and the old/new RPi design make it hard to completely say yes or no. However, if you are already using the cell phone battery pack, you usually get 2 USB power ports on it. So use a Y connector where your WiFI dongle pulls power from the battery pack, but still gets it's control signals from the RPi. This was also used in my nearspace balloon project. Here is an example:</div>
<div><br></div><div><a href="http://www.amazon.com/Apricorn-Power-Adapter-Cable-AUSB-Y/dp/B000JIOHDE/ref=sr_1_1?s=pc&ie=UTF8&qid=1390238076&sr=1-1&keywords=short+usb+y+power+cable">http://www.amazon.com/Apricorn-Power-Adapter-Cable-AUSB-Y/dp/B000JIOHDE/ref=sr_1_1?s=pc&ie=UTF8&qid=1390238076&sr=1-1&keywords=short+usb+y+power+cable</a><br>
</div><div><br></div><div>* You mention using a webcam. If it is connected directly to the RPi, I would definitely swap out the webcam for the RPi camera - it is lighter weight, lower power, easier to control, and you get better resolution/quality photos than with a webcam.</div>
<div><br></div><div>* So if you use the cell phone charger for the RPi and other electronics, you could then power the motors from a standard 7.2v power pack and use the 7.2v -> 6v regulator that Scott mentioned. This will keep the two power supplies separate and will help with the motors. You could probably drive the motors directly from the battery pack, but the only issue is that by not using regulated power, you will notice that the robot wheels will move slower as the batteries start to discharge. Depending on your use, this may or may not be an issue to you.</div>
<div class="gmail_extra"><br>* I am not 100% sure the ultrasonics will work if powered by the RPi - I think it will work, but it could cause problems for the same reasons I would not share the power with the motors. The ultrasonic pulses are not bad and can be easily powered by most controllers, but it comes down to how much power can be pulled from the RPi. I would have no problem suggesting you try it, and if it does not work, you will need to pull that power from somewhere else.</div>
<div class="gmail_extra"><br></div><div class="gmail_extra">* I have also used some of the smaller switching power supplies on robotic systems as well, and they do work well - just be careful of keeping motors and other electronics separate.</div>
<div class="gmail_extra"><br></div><div class="gmail_extra">* If you have to connect the grounds of the motors and other electronics together, consider using a small inductor as the ground connect between the two supplies to help decouple the spikes.</div>
<div class="gmail_extra"><br></div><div class="gmail_extra">* Place caps across the motor leads to help keep the transients closer to the motor and keep your motor wires short and away from other signals. </div><div class="gmail_extra">
<br></div><div class="gmail_extra"><a href="http://www.pololu.com/docs/0J15/9">http://www.pololu.com/docs/0J15/9</a></div><div class="gmail_extra"><br></div><div class="gmail_extra">Probably more ideas later - but that is a start...</div>
<div class="gmail_extra"><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 20, 2014 at 11:47 AM, Scott Hall <span dir="ltr"><<a href="mailto:scottghall1@gmail.com" target="_blank">scottghall1@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFCC" text="#3333FF">
<div>This is where we could benefit from the
experience of the robotics club guys (TAR - Triangle Area
Robotics).<br>
<br>
You will want to power the teensy on its own, not through the
power pins on a R-Pi.<br>
<br>
Circuit Cellar Magazine last August & September published a
Raspberry-Pi I/O board that is far superior to the Gert Board and
its like, but its shares one basic element:<br>
<br>
They have their own power connector, and regulate that with a
switching 5V regulator and a separate 3.3V regulator. That latter
they connect to pin-1 of the GPIO connector to power the R-Pi -
the USB power is never involved.<br>
<br>
If you are not using the 5V supply for anything beyond the motors,
consider this 6V regulator instead
(<a href="https://www.commonsenserc.com/product_info.php?products_id=51" target="_blank">https://www.commonsenserc.com/product_info.php?products_id=51</a>)
-- that'll get you more torque out of your motors, and constant
voltage regardless of the battery level.<div class="im"><span style="color:rgb(34,34,34)"> </span><br></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFCC" text="#3333FF"><div><div class="im">
<br>
On 01/20/2014 12:14 AM, Charles West wrote:<br>
</div></div>
<blockquote type="cite"><div><div class="h5">
<div dir="ltr">
<div>
<div>
<div>
<div>Hello,<br>
<br>
</div>
I'm building a mobile robot from an RC tank. I'm hoping
to have a Raspberry Pi with a Webcam, Wifi dongle and
speakers for the top layer, connected via USB to a Teensy
3.0 board (3.3 volts), which will be doing PWM with 2
H-bridges to control the motors and feeding back data from
3 HC-SR04 ultrasonic sensors (5 volts).<br>
<br>
</div>
<div>The motors/batteries are suppose to be at 6 volts. I
think I could boost that to as high as 9 volts without
problems (though it will oscillate as the motors are
used).<br>
</div>
<div><br>
</div>
The Teensy can be powered from USB from the Raspberry Pi and
will just be switching transistors (so the current draw
shouldn't be much). It looks like most everything else
besides the motors will be running at 5 volts. I could just
use a linear regulator, but with the Raspberry Pi and
accessories I think the wasted power could be substantial.<br>
<br>
</div>
<div>I could use a switching regulator, but the ones I've seen
so far seem to need a lot of external components (this is
mostly on breadboard at this point). Do you guys tend to
use complete PCBs (like this one: <a href="http://www.ebay.com/itm/171193232080" target="_blank">http://www.ebay.com/itm/171193232080</a>)?<br>
</div>
<div><br>
</div>
This is my first battery operated project, so I don't really
know the common solution here. If I may ask, what would you
advise?<br>
<br>
</div>
Thanks,<br>
Charlie West<br>
</div>
<br>
<fieldset></fieldset>
<br>
</div></div><div class="im"><pre>_______________________________________________
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</pre>
</div></blockquote><span class=""><font color="#888888">
<br>
<br>
<pre cols="80">--
Scott G. Hall
Raleigh, NC, USA
<a href="mailto:ScottGHall1@GMail.Com" target="_blank">ScottGHall1@GMail.Com</a>
</pre>
</font></span></div>
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