Author Topic: Dump Control / LVD Circuit  (Read 65711 times)

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ghurd

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Dump Control / LVD Circuit
« on: August 24, 2007, 03:25:21 PM »
I guess it's ready.





The circuit design was intended for the smaller systems.  

It is expected to fill the obvious gap between NO controller and a complicated or expensive controller.

The major design parameters were proper function, versatility, simplicity, ease in understanding, trouble shooting, and obtaining parts. And low cost.





The schematic is a virtual map of the circuit board.  Those who prefer a more standard format probably don't need this circuit.  

Simple. The PCB was laid out to minimize risk of solder bridges. Nothing has more than 3 legs. Everything except the voltage divider output is On or Off.

Some mosfets will have a different pin configuration.  Be sure to get the G, S, and D in the proper holes.





Understanding the circuit, a crash course:


The rectifier diode protects the circuit against reverse polarity.

The Green LED shows the circuit is connected to the battery.

The Yellow LED shows the circuit is dumping excess power through the dump load, or the item connected to the LVD has power.

The first Zener diode and the pot is a voltage divider used to monitor the battery voltage.

The second Zener diode protects the ZM and 2N7000 mosfet from over voltage conditions.


When the voltage from the pot to the `ZM' is lower than 4.6V, the ZM grounds the 2N7000 gate and the remainder of the circuit is off.


When the voltage from the pot to the `ZM' is higher than 4.6V, the ZM is open and the 2N7000 gate has 5.1V. This turns on the rest of the circuit.

The P Channel mosfet sees low voltage at its gate and it turns on.  It supplies voltage to the power mosfet gate, turning it on.  The dump load is now on.


The capacitor provides enough delay in cycling to ensure the circuit does not go into excessive oscillation.


The extra steps (from N to P to N) provide a fast hard square switching, and allow for the use of numerous and various models of N channel power mosfets.

Meaning the expensive power mosfets need not be logic level or have an ultra low resistance (if the amps being dumped through it are low enough and the heat sink is large enough).  Even a lowly IRF530 can be added to supply 2A to another dump load.


Resistor RX determines the hysteresis.  The lower the ohms of RX, the tighter the hysteresis.

Some people or systems want a tighter hysteresis, like 0.06V.

Others desire a little more tolerance, like a hysteresis of 0.15V.

Using the circuit as a low voltage disconnect, a hysteresis of 0.6 or 0.8V is good for me.


A brief parts list.

D1 blocking diode=1N4001 to 1N4007, LED1 is green, LED2 is yellow, LED resistors R1 and R2 = 3.3K (between 2K and 10K), C1= 10uF 16V (between 2.2 and 47uF, 10V minimum), ZD1 and ZD2 = 5.1V,  R3=51K, R4= 0 to 500 ohms (lower with many power fets or higher for LVD use, centered on 50 to 100 ohms), R5= 3K to 10K (3K with less hysteresis, or 10K with higher hysteresis, even 100K for use with a low power load for an LVD circuit).

N-fet=2N7000 or similar.  About anything that can take +-20V at the gate.

P-fet=BSS92, BS250 or similar.  About anything that can take +
-20V at the gate.


Power N-fet=IRFZ44N or similar.  Any power N-fet can be used, provided the current it carries causes less than the watts of heat it can tolerate and dissipate.  The IRFZ44N is a personal favorite because it is cheap, has low resistance, causes less heat, and can take reasonable (6A) current without much heat generation.


I like using a separate dump load for each power N-fet.  I have never seen a failure using an IRFZ44N supplying a 6A load.  I have seen 5 or 6 parallel IRFZ44Ns consistently fail while conducting less than 20A peak.

A higher hysteresis (like 0.08 or 0.1V) will minimize the chances of a power fet failure.


The RX resistor/hysteresis values.  1.8K/1.0V, 3K/0.8V, 3.9K/0.62V, 51K/0.14V, 100K/0.1V, 150K/0.08V, 180K/0.06V, 220K/0.04V.

Values for RX below 1.8K are getting near the danger zone and are not recommended.

Values above 220K are simply not needed and could cause problems.


It is of the utmost importance the wires for the circuit are separate from the wires supplying the dump load.  Otherwise the circuit will see the voltage drop from the dump load as a reduction in battery voltage.  The wires MUST be separate.


A fly-back or freewheel diode must be included for many dump or LVD loads, or the voltage spike will ruin the power fet.  It is not only for this circuit, it seems to be common for many switching circuits.


Calibrating the unit.  I suggest calibration without a dump load connected.  If the yellow LED is lighted, the dump load should be on.

A variable voltage supply is easiest. They can be easily made from a LM317 or LM780X (7805, 7806, etc).

A friend has no access to a variable voltage supply.  He used a running automobile to obtain 14.15V.  Simply 100% Genius.  The voltage on some cars (mine) can be slightly varied by turning the headlights or A/C on.


Everyone has their own ideas of what is best.  My personal preferences would be...

About 0.08V hysteresis for a dump load, for no particular reason except I think it is enough to accept the charge current, drain the surface charge, and not actually drain the battery (much).

About 0.62V for an LVD, because it is usually enough for what I do, without being too fast.  It allows for the loaded battery to reach 12.2V (about where hard sulfation can occur) before disconnecting, and 12.82V before reconnecting (to allow for a bit of voltage due to surface charge).


A switch between the circuit and battery will allow for manual equalization.


The unit can be used for a dump regulator, an LVD, a controller for charging a second or third battery, or about any combination of the above.


It will be available as a 150W kit.  Waiting for a few more parts to show up.

The kit will include the PCB and parts shown, an assortment of resistors, 2 power N-fets, some heat shrink tubing, LED retainer clips, etc.  

The kit will not include the actual dump load, enclosure, switch, wires, etc.

Looks like $12.50.  I'll get it up in Classifieds soon.


Anyone using this circuit feel free to jump in with information or pictures!


Open for questions.

G-

« Last Edit: August 24, 2007, 03:25:21 PM by (unknown) »
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dinges

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Re: Dump Control / LVD Circuit
« Reply #1 on: August 24, 2007, 09:53:08 AM »
What system voltages does it accomodate ?


Glad to see you have finally finished it and put it out here in the open. I know it has taken quite a few hours of your time. Thanks for that.

« Last Edit: August 24, 2007, 09:53:08 AM by dinges »
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ghurd

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Re: Dump Control / LVD Circuit
« Reply #2 on: August 24, 2007, 10:13:44 AM »
Thanks Peter,


It is for a 12V system as shown.  

The empty holes are for 24V modifications, that will come later.


I also see I did not identify the ZM as a ZM33064,


Or mention the trigger voltage is set by adjusting the blue pot.

Setting the pots center pin to ground at 2.7K gives close to 14V.


G-

« Last Edit: August 24, 2007, 10:13:44 AM by ghurd »
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Bruce S

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Re: Dump Control / LVD Circuit
« Reply #3 on: August 24, 2007, 11:11:32 AM »
G-

I agree with Peter, glad to see you've got this up here:-)

For wooferhound, this is the circuit this I use with the HF PDU. This unit lends itself perfectly to be attached to the 15V speaker area.

ALL; This I have adjusted as G-says for my output to be compatible with the battery packs that I rebuild from the packs that Nothin to Lose speaks about. Since I do use it as a dump load, I have the hysterysis set at the .08v level, Ghurd has on the instructions he sent me to build one, a sort of guide line of Rx equals hys*** chart, and since I stack 12 of these per pack to try and stay as close to a fully charged SLA as possible, or at least so the inverters don't see LVD, adjusted for 14V.


Oh and and for those who have the 5 watt VW panels and simialr units, the LM317 , since it can take a large voltage swing, works perfect to send a constant voltage output into this little gem, and TADA you have a backup solar charger :-)


Ghurd:>Let me know when your parts arrive , I'm still in need of those 3 other units.

I used the last of the units I have to make due for the HF controller thatis still showing only 3volts :-/ This helped out to keep the neighbors batts charged until he gets a real controller.


Cheers

Bruce S

PS> put the little video up here, it shows the LEDs flickering just like they should.

« Last Edit: August 24, 2007, 11:11:32 AM by Bruce S »
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fungus

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Re: Dump Control / LVD Circuit
« Reply #4 on: August 24, 2007, 11:35:27 AM »
Nice that its all out now :-)

I was wondering what the open holes were for... not sure how much use a 24v one would be but its nice to have options..

"Anyone using this circuit feel free to jump in with information or pictures!"

Used a 150w car heater on mine, picture of the controller in the case below..

« Last Edit: August 24, 2007, 11:35:27 AM by fungus »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #5 on: August 24, 2007, 02:45:41 PM »
In the interest of bandwidth, and to avoid admitting I don't know how to post a video, I submit this photo.  

Maybe my wife will upload a video of a prototype blinking a light bulb to utube and post a link.  The resolution is poor, but it is just a light bulb...

Blinking very fast. :-)<p>
This photo shows the circuit in action, though a bit in reverse. (I said it was versatile)<p>
The 'dump load' is the coil of a DPDT relay.  The N.O. contacts are in series with the solar panels.  I guess it could be more properly thought of as an LVD.

The controller circuit has a 0.62V hysteresis.  When the battery reaches it's maximum voltage, the "dump load" relay coil energizes and disconnects the PVs from the battery until the lower set point (decided by the hysteresis) is reached.  It effectively does not dump excess generated power, it simply disconnects it from the battery.  (not good for wind power)  When the system reaches the lower hysteresis voltage, the LVD activates, disconnecting the relay coil and reconnecting the PVs to the battery.<p>

Because this controller is driving a Relay-
I should point out that <strong>this</strong> is <strong>NOT a Permanent Installation</strong>.  I do not trust relays for long term and fast cycles, especially $10 generic RatShak relays!  This is cycling about 20~50 times per minute under good sun, less in low sun, more or less if the freezer is running, and none at night.<p>
It is only a quick fix to do what needed done at the time, with the materials I had available at the time.  It will soon be replaced with a MPPT.

BTW, it is still up and running as shown, with no problems. Guessing 10 weeks now.  

Hey! I've honestly been busy!<p>
The circuit is show in the lower left.  The ice cube relay is in the lower center.  The AL security light housing is acting as a heatsink for the double ~ connected bridge rectifier.<p>
It primarily supplies 20A of 12V solar for a SunDanzer DCF165 chest freezer.

Secondary uses are currently FANS, cell phones, cordless tools, PDA, nimh/nicd chargers, etc.  

Regardless, most of the power available at this time is not being used.<p>
G-<p>

<img width="80%" src="http://www.otherpower.com/images/scimages/2050/FrigCntrlr.jpg">
« Last Edit: June 03, 2010, 07:02:41 AM by ghurd »
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ghurd

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Re: Dump Control / LVD Circuit
« Reply #6 on: August 24, 2007, 03:03:10 PM »
Hey Angus,


Options are nice.


Great photo!  Shows the open holes and parts without glare. It must have taken 100 tries.  Thanks!


It also shows the 10uF 16V tant cap included in the kit.  The earlier pics show a smaller cap for clarity.

G-


 

« Last Edit: August 24, 2007, 03:03:10 PM by ghurd »
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DamonHD

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Re: Dump Control / LVD Circuit
« Reply #7 on: August 25, 2007, 01:31:32 AM »
Thanks G for sending me the diagram before: really cleared up in my mind what was needed!  I'm still all solar so far, but with wind will come some variant on your dump controller!


Rgds


Damon

« Last Edit: August 25, 2007, 01:31:32 AM by DamonHD »

coldspot

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Re: Dump Control / LVD Circuit
« Reply #8 on: August 26, 2007, 11:24:28 AM »
ghurd-

Thanks for sharing, your great!!!

Mark me down for one, for now, maybe more later.

Are set up for Pay-Pal??

 
« Last Edit: August 26, 2007, 11:24:28 AM by coldspot »
$0.02

claude

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Re: Dump Control / LVD Circuit
« Reply #9 on: August 26, 2007, 02:39:34 PM »
Nice work G!


I witnessed the development of this baby and now here it is, a great circuit with a lot of potential. Everyone should know that all this was made with great care and countless hours of testing. G proves itself worthy once again.


"Commercials"

When my power-generating abilities will rise up to a noticeable amount I'll surely use G's controller for my charging needs! :-))


Best regards,

Claude

« Last Edit: August 26, 2007, 02:39:34 PM by claude »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #10 on: August 27, 2007, 08:45:01 AM »
Thanks for the nice words everyone.


PayPal, yes.


Coldspot, check your frankenfurder? email.

G-

« Last Edit: August 27, 2007, 08:45:01 AM by ghurd »
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South Easter

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Re: Dump Control / LVD Circuit
« Reply #11 on: August 27, 2007, 11:00:14 PM »
Fantastic - just what I was looking for!


Can someone explain what to do with the 'mystery holes'?  I am running 24V, so would need to modify the circuit to handle that...

« Last Edit: August 27, 2007, 11:00:14 PM by South Easter »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #12 on: August 28, 2007, 06:44:21 AM »
The 24V modifications have not been tested.  So this is all theory.

I don't see why it wouldn't work.


The trace between the empty holes needs cut.

A 14 or 16V 1W Zener is soldered into the holes.

ZD1 is changed to 19V.

R1 is changed to 7.5K.

RX maybe 20K for a dump load controller, 1.8K for LVD.

Possibly a small cap paralleled with the 16V 1W Zener, in the same holes.


Remember. 24V has NOT been tested. All theory.

G-

« Last Edit: August 28, 2007, 06:44:21 AM by ghurd »
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ZooT

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Re: Dump Control / LVD Circuit
« Reply #13 on: September 04, 2007, 09:38:13 AM »
Er uh......if you shoot me an email with the paypal info I'll buy one :)
« Last Edit: September 04, 2007, 09:38:13 AM by ZooT »

bsafe

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Re: Dump Control / LVD Circuit
« Reply #14 on: September 25, 2007, 05:51:31 PM »
What gauge wire do you recommend for the connections?
« Last Edit: September 25, 2007, 05:51:31 PM by bsafe »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #15 on: September 26, 2007, 05:37:57 AM »
About #18 or #20, stranded.  Sometimes #18 can be snug.

I use #21.5 because I have 10,000' of gray and orange (I am a sucker for a great sale).


It doesn't carry many amps. Depends on the hysteresis and choice of resistors.

Not dumping takes about 3.5ma.  Dumping takes about 7ma to 12ma.

There is a larger surge current when the power fets first turn on, but it doesn't seem to cause any problem even with a 10' long pair of #21.5 wires to the battery.


The power carrying wires need to be heavier, at least #14. Depends on how many amps they will carry.

G-

« Last Edit: September 26, 2007, 05:37:57 AM by ghurd »
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indalohousse

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Re: Dump Control / LVD Circuit
« Reply #16 on: October 04, 2007, 03:58:25 AM »
please send me a link to where i can order this kit or board  indalohouse@tiscali.co.uk
« Last Edit: October 04, 2007, 03:58:25 AM by indalohousse »

RCpilot

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Re: Dump Control / LVD Circuit
« Reply #17 on: October 07, 2007, 08:25:24 AM »
Ghurd, Several users here have said that this will work for a Battery Vent Fan. I am needing a circuit that turns my fan on at a set voltage: somewhere between 13 and 14 volts, and turn it off when the voltage drops below the set point. Will this circuit work for that purpose? And, if it will, where do I send money to order one. I have PayPal.


Thanks, Kelly

« Last Edit: October 07, 2007, 08:25:24 AM by RCpilot »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #18 on: October 07, 2007, 09:40:49 AM »
It will work fine for that.


I can be contacted through ghurd1 (at) yahoo (dot) com.  

Put "Controller" in the subject.


My PayPal account is different.

G-

« Last Edit: October 07, 2007, 09:40:49 AM by ghurd »
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snowcrow

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Re: Dump Control / LVD Circuit
« Reply #19 on: October 09, 2007, 02:19:14 AM »
Hi Ghurd, I to am interested in a couple of these little gems too!! I also have a Pay Pal account and will email you.


Blessings, Snow Crow

« Last Edit: October 09, 2007, 02:19:14 AM by snowcrow »

indalohousse

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Re: Dump Control / LVD Circuit
« Reply #20 on: October 25, 2007, 04:46:36 AM »
thanks Ghurd  recived them fine    i have built one and i see the dump led comming on just under 5v on the middle of the zm    i have battery connected but no incomming power   what else do i need to to set it up please?  i have meters / adjustable psu and scope     my windmill is not on its tower yet so need to make the adjustments on the bench    ps   where exactly are you supposed to connect the windmill or generator?   regards rob
« Last Edit: October 25, 2007, 04:46:36 AM by indalohousse »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #21 on: October 25, 2007, 05:56:32 AM »
The windmill goes straight to the battery, and should be considered a completely separate circuit.

The windmill charges the battery.

The controller drains the battery, when necessary, just enough to keep it from over charging.

The only thing they have in common is the battery.


Set the adjustable PSU to exactly the voltage you want the battery maximum to be.

Adjust the pot until the dump LED lights up.

You can check it by turning the PSU voltage up and down, while watching the LED go on and off.


Example:  Say you decided you don't want the battery past 14.40V. Set the PSU at 14.39V.

Adjust the pot, slowly, until the yellow LED lights up.

Adjust the PSU voltage down until the yellow LED goes off.

Slowly adjust the PSU voltage up until the yellow LED lights up. Check the voltage is the same as intended.


Without an adjustable PSU, it can be set, or tested, with a tiny 12V battery, like 1.3 or 7AH.  Assemble a small dump load, such as a 12V 2.1A #1156 tail light bulb. Charge the battery with a cheap unregulated 12 to 18V DC, 100ma to 500ma wall-wart.

The dump load must take considerably more amps than the wall-wart can supply.

Watch as the battery voltage rises.  If the yellow LED is on too early, adjust it until it shuts off.

When the battery reaches the desired maximum voltage, adjust the pot until the LED light up.  The bulb will flicker or glow, maybe not enough to see.  But the battery voltage will be stable from then on.

Be careful the wall-wart does not become disconnected from the battery while it is still connected to the controller.


Also. Some people may find the battery voltage in their running car is what they want for the RE battery.  Turning on the head lights, A/C, or both, sometimes will 'adjust' the voltage a bit.

With NO dump load connected to the circuit, connect the circuit to the battery. Slowly adjust the pot until the yellow LED lights up.  Done.

(Sean- Thanks for that!)


G-

« Last Edit: October 25, 2007, 05:56:32 AM by ghurd »
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indalohousse

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Re: Dump Control / LVD Circuit
« Reply #22 on: October 25, 2007, 06:17:51 AM »
Fantastic   thats clarified it a whole heap    I will have a go tonight if i can, btw i found some 50 Ohm massive resistors   which i intend to use as my dump loads   you can see one in the photo on my Diary post  inside the bottom of the monitoring box    http://www.fieldlines.com/story/2007/10/12/91539/946     these were salvaged from those huge UPS's i mentioned in the emails i sent you    i take it these are more than man enough for one for each power mosfet    regards and as always  and thanks for your advice
« Last Edit: October 25, 2007, 06:17:51 AM by indalohousse »

ghurd

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Re: Dump Control / LVD Circuit
« Reply #23 on: October 25, 2007, 06:28:25 AM »
They are 50 ohms and certainly man enough for the power they will see at 12V.

But 14.4V / 50 ohms = 0.288A. They will only dump about 4W each.  :-(

Each fet could handle 20 of them in parallel, no problem.
« Last Edit: October 25, 2007, 06:28:25 AM by ghurd »
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indalohousse

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Re: Dump Control / LVD Circuit
« Reply #24 on: October 25, 2007, 06:47:08 AM »
ok so i should look be aiming for low resistance and high current handeling  bility    i saw an example of using small lengths of heating wire salvaged from a wall heater  and a fan to cool the whole shindig    this sort of thing.  I will search the forum for more ideas and get my best salvage head on    thanks Ghurd   and even more thanks for your kits   cant see how u can sell them at that price    i cant get the components  in the UK for less than your selling the whole kit         so a big CHEERS to you :)
« Last Edit: October 25, 2007, 06:47:08 AM by indalohousse »

South Easter

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Re: Dump Control / LVD Circuit
« Reply #25 on: November 04, 2007, 10:03:09 PM »
Hi ghurd.  Firstly, thanks for all you have done on this!

Secondly, could you post a close up relatively hires photo of the assembled PCB? (similar to view of CtrlInHand.jpg.


It would be helpful to double check things during assembly.  Thanks!

--

« Last Edit: November 04, 2007, 10:03:09 PM by South Easter »

wooferhound

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Re: Dump Control / LVD Circuit
« Reply #26 on: November 04, 2007, 11:56:18 PM »
Yes, I agree

I got 2 kits from you

The first one I assembled incorrectly

And fixed it by resoldering a coupla componets

anytime you resolder something

it's not as good the second time

not to mention the heat
« Last Edit: November 04, 2007, 11:56:18 PM by wooferhound »