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7812 Voltage Regulator Help

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duffman

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Well, I have gotten my 7812 voltage regulator and i want to take a 9 volt and make it twelve volts in order to run a really cool smartmug with only a 12 volt car hookup.

I have tried to find details on how to wire the LM7812 12 volt Voltage Regulator, its a pretty common IC, but have come up dry. Alot of people have told me to put the 9 volt to the imput, then ground the output and I magically get 12 volts. Doing this yields me .6 volts actually. Can anyone help me wire this?

Thanks ahead of time.
 
To do what you want you need an boost swicthimg regulator.An linear regulator like you have can only make the vlotage lower not higher.

Swicthmode powersuplys PWM drive aninductor to bost the voltage.They are smaller and much more eficent.How much curent do you need?
 
You can't get more than you start with using a linear regulator, you would need a switch-mode design to do so - so your 7812 is no use (assuming you haven't fried it?).

What are your current requirements at 12V?.
 
By "Smartmug" I'm guessing you have a heated mug with a thermostat. And by 9V I'm guessing you want to use a 9v battery.

Heating coffee or even keeping it warm requires more power than such a battery can supply. If it was a 9v transformer it would have to be fairly large one too, bigger than you might find on an answering machine for example. Like probably at least a couple of amps. Of course in getting a transformer it would be wise to get a 12v one to start with too.
 
I seen such an thing that if powerd off the USB bus.But 5V at 500mA is not gona heat it much(2,5W may just help the the mug cool off slower)

And its kinda sily to voltage regulate an heater.Becose if the large powers it needs and becose the heater just cares about the RMS power going in.

Do you know how much power it uses in Wats or Amps?

And for heating somting you will shurly need an big transformer.Since its an heater you dont need to make DC and stuff like that.Unles it uses electronics to control it,An simple mechanical termostart and an resistive heater can run on anything DC or AC as long as the input power is right.
 
Well, the smartmug simply displays the temperature, how full it is, and thats about it on an lcd. Its really low amp. It was cheap chinese manufacturing, and all they did to keep the fluctuating power source you get from a car from blowing the circuitry is adding a fuse in.

I guess I could settle for the completely inelegant way and just use 4 aaa batteries.

It just seems like I would have to apply so much voltage for such a small drain circuit.
 
I bet you that the internal circuitry only needs 5v.

It probably allready steps down the voltage from 12 to 5.

Just a guess, but 4 aaa batts, = 6v, and that is more than likely regulated via IC or resistor to 5v for the electronics.
You should take that thing apart and look.

Good Luck.
 
duffman said:
Well, the smartmug simply displays the temperature, how full it is, and thats about it on an lcd.

Woo, it is so useful. Now I can watch the LCD carefully while I'm filling up the mug to the correct level.

My own design is even better(don't bother stealing it, I've already patented it ). The LCD is situated near the bottom of the mug so I can also tell the remaining level while I'm drinking from it.
 
Is a SmartMug for people who are blind and numb?
If they can't see how much coffee is in the mug, then how can they see the LCD?
If they can't feel the temp of the coffee on their lips or in their mouth, then won't cold coffee feel the same? Maybe they want steam.

If its electronics runs off four AAA cells or a little 9V battery, why bother with 12V?
Its electronics and LCD draw next to nothing and it doesn't have a heater in it.
Does it have a high-power backlight for its LCD?
Does it have a high power gyroscope or something?

The "genius" who told you to short the output of the regulator was being sarcastic. Then you measured 0.6V, across the 9V battery? Was there much smoke?

Re-reading your post, I think you need an LM317 regulator to drop the car's 12V-14V down to 9V. An LM317Z is in a small transistor package and should do the trick.
 
audioguru said:
Re-reading your post, I think you need an LM317 regulator to drop the car's 12V-14V down to 9V. An LM317Z is in a small transistor package and should do the trick.

Not at all, its the other way round. He wants to get 12V from 9V. See following quote.

Alot of people have told me to put the 9 volt to the imput, then ground the output and I magically get 12 volts.
 
We are talking about a mug with a heater in it that runs off 12V from a car. Its heater probably uses a current too high for a small battery.
 

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no we're not. :D

I got this mug from target and its definitely kind of cheap. It doesn't heat anything. It only has one button on it. On and Off. and all it does is tell you the temperature and how full it is. but it has a car hookup just like that one.
 
Where did you get the idea to use a 9V battery? Does it have a 9V connector?
 
9 volts are just a really convenient battery, and the largest size that can be conveniently found. It is also somewhat compact.
 
Haven't you tried a 9V battery to power it? It will probably work.
Its current will be next to nothing without a heater, lights, gyroscope or GPS system. Does it play DVD's?
 
Here's what I think.

Your smart mug has a heating element in it, as almost all other smartmugs from Target do.
Check their website.

What is the point of knowing the temperature of the liquid in your mug, if you have no way of altering it?
Is that fancy Display to let you know when to drink up or when its to cold.
No.

Also, why would you want the adapter, when 4AAA bats, will last a long time, monitoring level and temp.Unless you wanted to heat something, then they are no longer suitable.
Those batteries are there just like your clock radio needs them to keep time during power failure.

These are my thoughts, so they may be irrelevant to you.

Have fun.
 
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