# Voltage and heating circuits?

Discussion in 'Electronic Basics' started by Guntar Gunderson, Jan 13, 2011.

1. ### Guntar GundersonGuest

I have a simple heating circuit that takes 16V @ 3.5A. I want to run
it on a 12V-48A/hr deep-cycle battery.

Now, I can get a DC-DC boost converter for \$80, NBD.

What will happen (generally) if I hook it up to the 12 volt source?
It doesn't have any solid state circuits... it's simply a resistance
device; I don't expect it to burst into flames. Am I violating any
basic safety rules if I plug into a lower voltage?

Gunz

2. ### Rich GriseGuest

If the heater is indeed nothing but resistance, it won't do any
harm at all, but you'll get a drastically reduced heat output. I'm
way too lazy to do the math; if it's nichrome, the difference would
be exaggerated, because nichrome has some insane tempco of resistance.

But there's very little danger that you'll burn the house down.

Cheers!
Rich

3. ### Jasen BettsGuest

it will heat less powerfully by the ratio 12^2/16^2
which is 144/256, 9/16, or about 56%

ballpark 70-80%

4. ### Jasen BettsGuest

nichrome's tempco is very close to 0, stainless steel on the other
hand goes up quite a bit from room temp to red-hot.

5. ### F. BertolazziGuest

Guntar Gunderson:
If you need more heath than half of the rated, maybe it's less expensive to
buy another battery to be put in series with the one you have and build a
simple, very low frequency, PWM controller, that will cost you about \$5.

6. ### Rich GriseGuest

Hm. I must have been thinking tungsten, as in bulb filaments.

Thanks!
Rich

7. ### Phil AllisonGuest

"Rich Grise is off his Drugs":

** Ni-Chrome has a large tempco ??

News to everyone that has ever used any.

Wot a moron.

..... Phil

8. ### Phil AllisonGuest

"Rich Grise"

In practice, the heat difference would be diminished compared to a simple
resistance - cos as the applied voltage drops, so does the resistance of
tungsten.

...... Phil

9. ### Rich GriseGuest

Uh, yeah, that's what I just said.

Thanks,
Rich

10. ### Phil AllisonGuest

"Rich Grise"
** No dickwad - you said the direct opposite in fact:

" if it's nichrome, the difference would
be exaggerated, because nichrome has some insane tempco of resistance."

Piss off - IDIOT !!

...... Phil

11. ### Rich GriseGuest

Yeah, and I stood corrected: After I was duly informed of my error, (see
upthread, if you're a man) I said, and you can look above, "Hm. I must
have been thinking tungsten, as in bulb filaments."

Oh, well, guess you missed your Tourette's meds today.

But thanks for playing!
Rich

12. ### Phil AllisonGuest

"Rich Grise is a Fucking MORON "

** And that is where you made the second error - fuckhed.

Now you've made a third and forth time just to prove how thick you are.

...... Phil

13. ### Rich GriseGuest

You can't insult me if you can't even spell "fuckhead."

Thanks,
Rich

14. ### Michael RobinsonGuest

Guntar, are you still there?
Just ignore the silly little flame wars. Phil has been doing that for
years.
Others have pointed out that heat from a resistor varies with the square of
the voltage, so you might be able to get by with a single 12 volt battery,
or two of them in series if you need more heat. But you don't have much
control over the amount of heat you're getting that way.
You could have an adjustable heater if you go with two batteries and a
simple controller, whereupon you could simply turn a knob and get just
exactly the amount of heat you need.
I googled "adjustable duty cycle heater controller" and found some that run
on 12 volts, but you would probably want two batteries in series (nominally
24 volts).
If you're comforatable with a soldering iron, you could make your own
controller -- it's a simple project, because all you need is a circuit that
turns on and off at a low frequency, like once a second. You adjust the
duty cycle and therefore the amount of heat.
We haven't heard back from you, but there are people here that just love to
offer their know-how on stuff like this. But you've gotta talk to us!