12 volt regulation help needed

B

bobg

Guest
I have built a very simple PWM controller to control the temperature of the
grip heaters on a ATV. Uses a 4093 with a transistor, 2 diodes, 2 caps, 1
resistor and a pot.Circuit is powered by the battery and works ok but the
temperature increases or decreases slightly with the RPM of the motor and
the output of the alternator. My question is what is the easiest way to have
regulated 12.50 volt to power the circuit? The alternator will output 15
volt max. and the circuit handles 3 amps. max.. Thanks in advance, BobG.
 
John Fields wrote:
On Mon, 14 Mar 2005 21:03:49 -0500, "bobg" <robgagnon1@videotron.ca
wrote:


I have built a very simple PWM controller to control the temperature of the
grip heaters on a ATV. Uses a 4093 with a transistor, 2 diodes, 2 caps, 1
resistor and a pot.Circuit is powered by the battery and works ok but the
temperature increases or decreases slightly with the RPM of the motor and
the output of the alternator. My question is what is the easiest way to have
regulated 12.50 volt to power the circuit? The alternator will output 15
volt max. and the circuit handles 3 amps. max.. Thanks in advance, BobG.


---
You don't need regulated 12.5V. If you want to keep the grip heaters
at a constant temperature you need to make that temperature happen
with the lowest system voltage you've got and then use your PWM
circuit to keep them from getting hotter as your system voltage
increases.
Click to expand...
There's a technique used on older bikes.
Run the heaters off AC, directly off the alternator coils.. Put a
series inductor.
As the RPM increases and the frequency increases, the inductor
has greater impedance.
When you do the math, you might find that the inductor is physically
too big for your liking, but it's worth a calculation. YMMV.
mike

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"John Fields" <jfields@austininstruments.com> wrote in message
news:bugc31h50vnpafej00ka9cbeip95n4heeu@4ax.com...
On Mon, 14 Mar 2005 21:03:49 -0500, "bobg" <robgagnon1@videotron.ca
wrote:

I have built a very simple PWM controller to control the temperature of the
grip heaters on a ATV. Uses a 4093 with a transistor, 2 diodes, 2 caps, 1
resistor and a pot.Circuit is powered by the battery and works ok but the
temperature increases or decreases slightly with the RPM of the motor and
the output of the alternator. My question is what is the easiest way to have
regulated 12.50 volt to power the circuit? The alternator will output 15
volt max. and the circuit handles 3 amps. max.. Thanks in advance, BobG.
---
You don't need regulated 12.5V. If you want to keep the grip heaters
at a constant temperature you need to make that temperature happen
with the lowest system voltage you've got and then use your PWM
circuit to keep them from getting hotter as your system voltage
increases.
Click to expand...

Expanding upon John's comments (with which I concur), the PWM
generating circuit you have can probably be simply modified to alter
the duty cycle in the appropriate direction as the supply changes.
Showing your circuit, (perhaps with the help of the tool at
http://www.tech-chat.de/aacircuit.html
) would allow folks here to suggest those changes. For a narrow
range of supply variation, such as can be expected for a vehicle
battery most of the time, this correction can be close to enough
to ideal to yield all the improvement you can perceive. (I assume
the "grips" are something you hang onto and they are heated to
keep people's hands from getting too cold.)

What puzzles me is why, if your controller controls temperature,
is it sensitive to supply voltage at all? That may be due to a
simple design oversight which can be spotted readily once you
show the circuit. Alternatively, it will allow others to discern
which parts could be powered by a low power regulator to fix
the problem, rather than regulating the power circuit.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
On Mon, 14 Mar 2005 21:03:49 -0500, "bobg" <robgagnon1@videotron.ca>
wrote:

I have built a very simple PWM controller to control the temperature of the
grip heaters on a ATV. Uses a 4093 with a transistor, 2 diodes, 2 caps, 1
resistor and a pot.Circuit is powered by the battery and works ok but the
temperature increases or decreases slightly with the RPM of the motor and
the output of the alternator. My question is what is the easiest way to have
regulated 12.50 volt to power the circuit? The alternator will output 15
volt max. and the circuit handles 3 amps. max.. Thanks in advance, BobG.
Click to expand...
---
You don't need regulated 12.5V. If you want to keep the grip heaters
at a constant temperature you need to make that temperature happen
with the lowest system voltage you've got and then use your PWM
circuit to keep them from getting hotter as your system voltage
increases.

--
John Fields
 
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