Voltage Regulator

SailerMan

I am building my own dual motor controller for 12volt motors ...yeah I know why not just buy parallax's... simple I like to see if I can do it myself. Anyhow during my design I though... why put 12v and 5v to the board when I can just build in a 5v regulator on the main board and let the 12v motor power also power all the logic.. I chose the 7805 in the 8 pin soic package.. I thought that 100ma would be plenty but it's getting really hot. So I need a small design revision.

Can someone recommend a 5v regulator in a small package that can give me more current capacity. I've looked around and quite frankly the are tons of voltage regulators.

Thanks in advance,
Eric

Bean

Eric,
It is usually not a good idea to run motors and electronics from the same supply. The motors will generate alot of noise on the power lines.

As for the heat, try putting a resistor before the regulator so the regulator doesn't have to disapate all the heat. A 39 ohm 1/2 watt resistor should do it.
That way instead of the regulator disapating 0.7W ((12-5)=7 volts * 0.1 Amp) the resistor is disapating 0.39Watts and the regulator is disapating (0.70-0.39) or 0.31 Watts.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
There is a fine line between arrogance and confidence. Make sure you don't cross it...

·

SailerMan

Thanks bean... I would have never thought to do that..This motor controller thingy that I'm playing with uses an SX48 to control two vnh2sp30 motor chips.. and there are 4 smt led. each with 270 ohm resistor. I'm going to have to look at the data sheets but I think I'm under budget on current draw. but I'm thinking that maybe a better regulator might be a good choice.

The motor controller seems to be working well right now during preliminary tests.. No glitches yet. Except for the hot regulator. Many tests to go.

Thanks again for you help.
Eric

kwinn

At minimum you should put a diode and capacitor between the 12V and the resistor/regulator so that the high start current of a motor does not cause the input voltage to the regulator to sag.

Brad_H

Hello Eric,

Would bringing down the voltage in steps using a 7809 prior to the 7805 or using a Switching regulator be viable options?

SailerMan

All good Ideas.. I was hoping for a suggestion on one regulator.. I'll keep up the search.. Maybe just a D2Pak 7805. Oh here is a Picture of the controller. I'm kinda proud of it mainly because it works. [noparse]:)[/noparse] Goals to have motor speed feedback and current monitoring.

SRLM

mouser has some linear regulators that are rated for up to 3 amps.

Philldapill

For nearly all my designs, I use TI's uA78mXX regulators. The XX could be 05(5V), 33(3V), 12(12V). They come in a D2PAK and can handle 500mA. The part is in their sample program, so order a few(up to 10 I think), and try them out in your design.

sam_sam_sam

Take a look at this I just bought 6 of them they are very nice board I have not use they yet
I can tell you what I think about how well they work if you would like me to Please let me know




http://www.futurlec.com/Mini_Power.shtml

This·is what the board look like



▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

Post Edited (sam_sam_sam) : 5/23/2009 12:34:24 AM GMT

sam_sam_sam

UpDate

I did some testing on this board

Voltage was set @ 12 Volts

5.00 volts @ no load

·4.97 volts·@·600 mill-amps

This load was left on for about 2 minutes and the regulator did not even get warm the rectifier did get a little warm This was DC voltage

The board is rated @ 1 amp with the input voltage no more than 12 volts Range is 7· to· 12 volt

So from this test it·tell me that if you· use a Basic Stamp or SX chip and a LCD Display it should work very good for that

Here is a another Regulator Board

http://store.nutsvolts.com/product.php?productid=16725&cat=379&page=1



The voltage can be as high as 30 volts if·I remember right Please look at the Data Sheet

This board is rated at 3 amp

This board· has a ADJ regulator you can use a 5 volt version and leave out the pot

The test·I did on this board was a little better 4.99 volts @ 600 mill amps

I have use· this board before and work very well·I used in the Elapsed·Equipment Timer Project had post a while back on the Forum

I power the Basic Stamp and DS1302 a LCD Display with the back light on most of the time ·and the regulator dose not get warm at all I did put a heat sink on it just in case
·

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

Post Edited (sam_sam_sam) : 5/26/2009 12:52:02 AM GMT

SailerMan

Sam_Sam_sam,

Thanks for that... IT's appreciated... Ya know I played around with Switching Regulators.. and made myself a 3.3v and 5v dual power supply.. That was fun.. Here is the link

http://forums.parallax.com/showthread.php?p=691979

Actually... I noticed some comments from you on there. [noparse]:)[/noparse]

sam_sam_sam

SailerMan

How did those boards work out for you

I would to have 5 and a 12 volts on one board

I could use this in some of the projects have made before

Did you make any more of them

If you do Please Let Me Know

I forgot about that Post until I look at it again




▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

SailerMan

I never did make anymore.. but I still use the original one every day. I was actually going to pick that project up again. I know that I can buy things but it fun to make them myself if I can. I just have to finish my motor board.

I forgot about that post also until you posted the photo of that switching regulator.

sam_sam_sam

Please let me know if you make any more boards

Thank You··

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

SailerMan

Do you just want the board or do you want it populated?

sam_sam_sam

Sailer Man

Just looking for the board only

I will pay you for the boards when you order more for your self· I am looking for three of them

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam