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Topic: 5 volt power supply design (Read 5808 times) previous topic - next topic

polishdude20

Mar 11, 2011, 05:44 am Last Edit: Mar 11, 2011, 06:20 am by polishdude20 Reason: 1
So for my light following robot I need a constant 5v that i can deliver to the motors and the arduino can't provide that without overheating the regulator :\

My solution is a seperate little PCB with a voltage regulator and a heatsink that can take a 9volt battery and make 5v out the other end for the motors, anyone have any good schematics of doing this? I'll design the PCB myself no problem I just need some advice on what value to use especially when I'll be powering 2 motors at once.

*edit*

Since I will be using a 9 volt battery will i still need the capacitors? What values should they be and I will be using 3 capacitors unless that's too much.

CrossRoads

Yes.
You can try without, may not get the best performance.

For better battery life, I suggest a switching regulator, such as:
http://www.pololu.com/catalog/product/2110
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

leolfs

Check out  78B05  switcher from RECOM readily available from  various sources. Use just like a 7805. Same pin outs. 1 amp max out. No heatsink needed.
Been using these for some time. Really make your power supply problems go away!
Other voltages are available.

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

MarkT

Can the motors not take 6V?  Then you can use 4 cells directly and not waste 4V nor need any regulator...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

leolfs

CrossRoads,
Here's the RECOM site. I have been buying from RS Components.
http://www.recom-international.com/products-menu/r-78.html

CrossRoads

I don't see how one actually goes about buying anything from RECOM. There are no prices, the link to the US distributor is no help.

How about a link to RS Components then?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

trembo

http://cgi.ebay.com/RC-3A-U-BEC-UBEC-Input-5-23V-Output-5V-3A-continuous-/180536793817?pt=Radio_Control_Parts_Accessories&hash=item2a08d4dad9

http://cgi.ebay.com/4A-UBEC-RC-Helicopter-Car-2-6S-Lipo-Battery-Input-5V-2S-/280586490381?pt=Radio_Control_Parts_Accessories&hash=item415442120d

http://cgi.ebay.com/RC-5A-U-BEC-UBEC-Input-5-5-23V-Output-5V-5A-Continuous-/150527884850?pt=Radio_Control_Parts_Accessories&hash=item230c293e32

keeper63

I wouldn't expect that using a 7805 with a standard 9V battery (maybe a lithium would be ok?) would last very long; the 7805 being such a inefficient regulator, coupled with the low mAH rating of a 9V battery - you'll really chew through a lot of batteries in that manner...
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

CrossRoads

9V not lasting long going thru 7805 - That's why I suggested a stepdown regulator like this
http://www.pololu.com/catalog/product/2110

Available from Canadian distributors
http://www.pololu.com/distributors#canada

or this also
http://www.robotshop.com/ca/Dimension-Engineering-Switching-Regulato-1.html

vs e-bay Hong Kong and 2-week to 1-month (!) delivery times.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

keeper63


9V not lasting long going thru 7805 - That's why I suggested a stepdown regulator like this
http://www.pololu.com/catalog/product/2110

Available from Canadian distributors
http://www.pololu.com/distributors#canada

or this also
http://www.robotshop.com/ca/Dimension-Engineering-Switching-Regulato-1.html

vs e-bay Hong Kong and 2-week to 1-month (!) delivery times.


Ah - missed that, my apologies!

The 7805 is really only for when you have a current source big enough for it that the inefficiency doesn't matter as much (ie, mains transformer or large battery); a switching regulator is a better option if it will fit in your budget otherwise. Still, using a standard 9V battery for anything other than light loads, regardless of regulation, doesn't seem like the best idea to me.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

CrossRoads

I found another 5v regulator in 7805 format, $8.99

http://www.gravitech.us/35v1aswvore.html
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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