Author Topic: High Amp 12V Regulator  (Read 2338 times)

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Offline hendrachubbyTopic starter

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High Amp 12V Regulator
« on: September 04, 2009, 01:23:40 AM »
Hallo all,

I got 2 Electrical Brake rated 3.6W 12V on my robot, i need to convert my 24V power supply to 12V, i already try using 7812 voltage regulator but when i activate the brake the regulator getting very hot and then it can't deliver 12V voltage to the electronic brake constantly ( the brake rapidly turn on and off ), so i need help,  someone can suggest me a better regulator??

Offline SmAsH

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Re: High Amp 12V Regulator
« Reply #1 on: September 04, 2009, 01:34:32 AM »
have you tried putting 7812's in parallel to up their amperage rating?
im against this because of all the wasted power, but what ever.
you can also look into switching regulators, although expensive, waste way less energy!
Howdy

Offline hendrachubbyTopic starter

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Re: High Amp 12V Regulator
« Reply #2 on: September 04, 2009, 01:53:29 AM »
How about if i use LM317 ?

Offline madchimp

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Re: High Amp 12V Regulator
« Reply #3 on: September 04, 2009, 02:44:29 AM »
well if the two brakes are always active at the same time you might be able to wire them in series but I've never dealt with electric brakes so someone please correct me if I'm wrong.

Offline Soeren

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Re: High Amp 12V Regulator
« Reply #4 on: September 04, 2009, 03:08:24 AM »
Hi,

Yes, it was my first thought wiring them in series as well.

If that's not an option for some bizarre reason, just add a a large(ish) heatsink to the regulator to dissipate the up to ~9,5W.
Alternatively, a power PNP-transistor in a a TO-3 housing (and a heatsink) could be used to beef up the 7812.

Switching to LM317 won't change much, as it is still a TO-220 housing and the wattage it has to dissipate is the same.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline hendrachubbyTopic starter

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Re: High Amp 12V Regulator
« Reply #5 on: September 04, 2009, 03:26:25 AM »
Quote
a power PNP-transistor in a a TO-3 housing
can you give me example of that kind of regulator ?,

how about if i try to paralelled the 7812, i saw some people do that.??

Offline Soeren

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Re: High Amp 12V Regulator
« Reply #6 on: September 04, 2009, 03:50:07 AM »
Hi,

can you give me example of that kind of regulator ?,

Directly from a datasheet:

http://That.Homepage.dk/Img/Boosting.png


how about if i try to paralelled the 7812, i saw some people do that.??

You'd still need a heatsink, so why not try that first?
What you are experiencing is the thermal protection shutting the device down as it gets too hot - add a suitable heatsink and your problem goes away.

But... Why not just connect them in series?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline hendrachubbyTopic starter

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Re: High Amp 12V Regulator
« Reply #7 on: September 04, 2009, 04:06:29 AM »
okay i will try that schematic.. ;) hope it works fine..

Quote
But... Why not just connect them in series?
actually i activate the brake from a microcontroller with a relay, so sometimes only one of the brake is active so i can't connect them in series.

Offline Soeren

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Re: High Amp 12V Regulator
« Reply #8 on: September 04, 2009, 06:56:50 AM »
Hi,

actually i activate the brake from a microcontroller with a relay, so sometimes only one of the brake is active so i can't connect them in series.
Ahh, OK.

If you feel up to it, you could also use a 50% "PWM" to reduce losses to almost nothing.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Admin

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Re: High Amp 12V Regulator
« Reply #9 on: September 07, 2009, 06:34:07 AM »
First, look at the datasheet to see how much current the voltage regulator can handle.

Lets pretend its a 12V regulator that can handle 1 A.

Now measure the current on your electrical breaks . . . lets assume 3A continuous.

That means you'd need at least 3 regulators in parallel to handle all that current.

And if it isn't 12V, then you'd need to put even more in series (if 3 are already in parallel for 6V regulators, you'd need 6 total regulators, etc).

But it appears you are trying to use a 24V lead acid battery. The best solution would be to find a 12V battery, like a motorcycle battery, and not bother with regulators.

 


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