# 12 volt dc voltage regulator

Discussion in 'The Projects Forum' started by jpark63, Feb 28, 2010.

1. ### jpark63 Thread Starter New Member

Feb 18, 2010
3
0
Hello everyone,

I would like to make a voltage regulator for my 12-volt dc water pump. I have some experience with electronics but no formal training so all help with this is very much appreciated.

I use the same 12-volt dc pump on a few different vehicles that the battery voltage output will varies (12.80 to as high as 14.5 dc volts) and because of this the speed or volume of the pump will also go up or down. The water pump only pumps 1.1 gallon per minute, which is perfect for my application. So I need to keep the pump running as constant as possible.

12 Volt Dc water pump specs.
Shurflo pump model 8005-292-139
The amp draw is 1.9 amps with a maximum draw of 3.8 amps.
Pressure setting for this pump, 45 PSI, I use this for circulating water so the pump has no more then 5  10 PSI

I would like to keep the input volts at 13.0 + .5 volts. Also, I would like to do it as easy as possible.

Thanks for everyones input and help with this.

2. ### MarkTBSc New Member

Feb 27, 2010
6
0
If you were willing to accept running the pump at 12v then Seme Lab do a nice series of Voltage Regulator semiconductors. The IP1R18A-12 will handle up to a 35v input and will put out a constant 12v at up to 5A.

• ###### Semelab.pdf
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Apr 5, 2008
15,799
2,386
Hello,

@MarkTBSC, with the given regulator the minimum input voltage must be 15 Volts to get the 12 Volts output.

@jpark63, for a regulator that can boost and drop voltage look for a buck-boost or sepic regulator.

Greetings,
Bertus

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
The IP1R18A-12 has a dropout voltage of 2.5 volts.

This means the minimum acceptable input voltage for 12 volts is 14.5 volts.

jpark
This will be a problem to you even if you went for a low dropout regulator becaue your minimum input is below your target of 13 volts.

You need to reassess your requirements first off.

5. ### jpark63 Thread Starter New Member

Feb 18, 2010
3
0
Studiot, My true target is 13.0 volts but if I can't control the volts going to the pump at 13.0 dcv exactly, then it could go + .5 volts. But I would prefer it to stay at 13.0 or even 13.5 but not more then that. When Ive hooked this pump to a truck with battery volts of 14.5 volts the pump volume is to high. As I said this pump only pumps at 1.1 GPM as it is and it's hard to find any other pumps that are 12 vdc that I can run like this one.

Bertus, I've looked at the sepic regulators a little before responding, Ill do more research on it. I think this might be the way to go. Do you know at sites that would be best to check out?

6. ### k7elp60 Senior Member

Nov 4, 2008
478
69
I allready have a box built that gives a regulated output of 13.7 volt up to 3.5 amps from a 12V source. The output is adjustable and the current limit can be changed if necessary. I built it to charge a sealed lead acid battery from a cigarette lighter socket in my car. If you are interested I would be happy to sell it to you for a reasonable amount. If you are interested send me a personal message.
Ned

7. ### jpark63 Thread Starter New Member

Feb 18, 2010
3
0

Ned, I appreciate your offer to sell me your charger but I am interested in building it myself. I thought this web site was for helping people build and/or design their projects. Plus since I have three trucks that I need this for, so I will need to make three of them.

8. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Yes, this place can be pretty helpful for various projects.

However, are you aware of the complexity of the task you wish to do?

Obtaining a constant 13A, 3.8A, 50 Watt output from a power source that may vary anywhere from 11.5v to 40v (reasonable automotive values) with good efficiency is not a particularly easy task. If you are not familiar with SMPS (switch-mode power supplies) then you will need to do some studying to get at least a layman's acquaintance with them.

You won't be able to accomplish what you want to do with just one IC and a heat sink. If you want it to be at least reasonably efficient, the design could become rather complex.

Here are a couple of links for you to start familiarizing yourself with a few types of SMPS:
http://www.smps.us/smpsdesign.html
http://schmidt-walter.eit.h-da.de/smps_e/smps_e.html

You said in the beginning that you wanted simple. I'm afraid that simple went right out the window when you wanted to maintain a voltage that high with basically 4A current.

9. ### k7elp60 Senior Member

Nov 4, 2008
478
69
I am still willing to help you. Since you need three of them I would be happy to supply you with a schematic and parts lists.
The attached file is a block diagram

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10. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Perhaps things could be made simpler if a 24V battery were used as the input power source rather than the 12V battery. That would then permit the use of a buck mode smps rather than the more complex buck-boost mode that would be needed for the 12V battery. Can we assume that the pump is not going to be running continuously but intermittently? 50 to 60 Watts is a lot to ask from a battery for very long.

hgmjr

11. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
I had the impression that the pump was going to be running constantly. Adding a 2nd battery and trying to keep it charged would be an additional complication and expense.

However, I'm wondering if there are similar pumps that can deliver about the same GPH rate, yet run from a lower voltage - perhaps 6v to 10v? An efficient buck converter would be much easier to design/build than a buck/boost.