Ultimate Passthrough

[o4srt]

Was bored at work the other day, and am getting tired of charging batteries (even though I only go through 1 set a day) so I decided to make a passthrough.

Tech specs:

LM317HVT regulator, Vout set at 5.5 volts

Vin either 16v from a modified laptop power supply, OR 12 volts from a modified cell phone car charger

TO-220 heat sink on regulator (reaches 60 celsius in a hurry without it)

40mm fan on side of box to further cool regulator

BNC cable plug for easy connections

The regulator is rated at 1.5 amps when Vin-Vout is greater than 15 volts, and 2 amps when less than 15 volts. Including the fan, the rig draws 1.9 amps. Still creates a fair amount of heat, but the regulator averages around 30 celsius.

I could have made something more efficient, but I used parts that were available at work. AND because someone on another forum said that the regulator couldn't successfully be used, so I HAD to prove them wrong.

This setup puts out TONS more vapor than my 5.5 volt box mod, most likely because the 14500 batteries in the mod cannot discharge at a high enough rate. The only thing I dislike about it is the noise of the fan, sounds similar to a muted hair dryer. Functionally though, it performs great!

[mcquinn]

I did basicly the same thing,but I put a variable power regulator/supply in line with a wall wart up to 30 volts.If you keep the volts in close to what you want for volts out you won't need to dissapate so much heat.I use a 5 volt wall wart as I prefer 3.7 to 4 volts and I just use any straight through passthrough.I tried a 12 volt power supply but like you I had a lot heat to get rid of,reducing 5 volts to 4 doesn't produce much heat at all. http://www.adafruit.com/index.php?main_page=product_info&cPath=38&products_id=184 is a kit with everything but case and whatever kind of plugs you prefer for $15.00 plus S&H. . All of the protected batteries I have looked at so far will reduce the current .

[o4srt]

I did basicly the same thing,but I put a variable power regulator/supply in line with a wall wart up to 30 volts.If you keep the volts in close to what you want for volts out you won't need to dissapate so much heat.I use a 5 volt wall wart as I prefer 3.7 to 4 volts and I just use any straight through passthrough.I tried a 12 volt power supply but like you I had a lot heat to get rid of,reducing 5 volts to 4 doesn't produce much heat at all. http://www.adafruit....products_id=184 is a kit with everything but case and whatever kind of plugs you prefer for $15.00 plus S&H. . All of the protected batteries I have looked at so far will reduce the current .

if I were to actually do this right, i'd use a switching regulator with a supply of 7 volts or so. but the only thing I actually paid for was the 4xAA box, everything else, I was able to find at work.

[mcquinn]

Sweet.I wonder why no one is selling modded power supplies?I would think there are a lot of people who would grab one up where you could dial in your favorite voltage on your favorite PT.Probably less than $20.00 for everything a person would need for a basic one.Adjustable lab supplies are pretty pricey.

Edited October 18, 2010 by mcquinn

[o4srt]

Sweet.I wonder why no one is selling modded power supplies?I would think there are a lot of people who would grab one up where you could dial in your favorite voltage on your favorite PT.Probably less than $20.00 for everything a person would need for a basic one.Adjustable lab supplies are pretty pricey.

sure are, a good agilent adjustable power supply that can provide the current we need can be around $1000 new. Fortunately, as an electronics technician at a DoD contractor, I have access to all sorts of mod-friendly toys.

if you do a search, you can turn an ATX power supply into a decent lab-style supply with a little work.

TI makes a good regulator chip (http://focus.ti.com/...k/ptr08100w.pdf) that I used in my box mod, available for free if you request an engineering sample. I'd probably use this in my next passthrough as well, as it will handle Vin of up to 14 volts, making it a snap to power from a cigarette lighter.

Edited October 18, 2010 by o4srt