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Topic: How to bypass the barrel jack Duemilanove? (Read 860 times) previous topic - next topic


My first topic, here goes:

We're prototyping a pump controller using the 2009 and have hooked up a 7809 regulator to take the 13.8 volts some supplies and batteries provide (and which also powers our pump) to send 9 volts to the Arduino input.  I've studied the schematic (http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf) and also the Arduino itself and see no good way to do this.  You could use Vin, but that bypasses the diode I assume is there for reverse voltage protection, something we don't want to do.  And tapping into the SMD points is way beyond me.  Using part of a barrel jack looks tacky.

Reports on the project at lrrd.blogspot.com; it's a cool one!

Any ideas?  Many thanks.


Maybe add our own protection diode?  Then could tap right into the Vin and be safe.


Thanks Richard.  No barrel jack because we're jamming the thing into a small splashproof box and it's awkward; there is a VERY real reverse polarity risk because users will connect a 12v deep cycle battery with alligators; and we all get our colors mixed now and then.

Will the 7809 protect against that?  I'm a geologist building electronics, sorry...  If so I'll connect to Vin and we're done.

Was afraid to solder to that barrel jack; with the lead free, didn't want to fry the pad and mess up the trace.

This thing will go into production; maybe 10 or so copies with regular Duemilanove, before we move to the pro or whatever.


I suggest you go to Radio Shack (or a cheaper place if available), get some project boards, wire and such, 15 watt soldering iron, and start getting some practice soldering small parts.
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.


Great advice Richard, thanks--we'll protect the 7809 with a diode, and done.

Thanks.  This forum is a wonderful place.


might I suggest the really bare bones arduino, if you dont mind looking at a chart to see which pins are which



Thanks guys.  We're looking at making maybe 50 of these a year (for zero/low profit educational tools) and would like built in USB jack and voltage regulator.  The 2009 with solder pads instead of pin jacks would be perfect.  Is there anything like that?


Sorry, I'm working too many hours (and running a biz).  We want educational users to be able to hack the flow controller, so probably we will stick with the 2009--we want the unit to be very accessible.

All will be in a box, but with easy access for students/users to get in a rewire things.


You might use something like below with the rbbb kit to have USB access when needed, then unplug when not needed.

Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.


Many thanks Zoomkat, that might be the ticket; some of our users won't want to hack or even connect with USB, so we can use non-USB Arduinos for that model, and your suggestion for USB people.

And it was a real problem to cut through the enclosure for a full size USB connector, the mini one would be much easier.  :)


Jul 31, 2010, 07:01 am Last Edit: Jul 31, 2010, 07:04 am by Osgeld Reason: 1
for a few bucks more you can get that same thing in the usb cable and it breaks out to a 5 pin socket (outside of the case), and still be cheaper complete than a 2k9 + have an option... ie  if your user does not require mods,  its even cheaper for them, if they do require mods,  charge them 25 bucks for a programming cable you got for ~20

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