VV Weller BP645

[bstedh]

I found a thread last week that had the Weller battery powered soldering iron modded and realized I had one sitting in a junk box. So very little work later I had my first mod, a KR808 Weller BP645. I think someone named them the HungWell. It was supper easy so now I want to incorporate VV and better batteries because standard AA don't cut it. They drop off way to quick. It's heaven with fresh batteries but that doesn't last long.
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I am ordering the VV kit from MadVapes and I need recommendations for what batteries to use.

I will have room for 2 AA sized batteries stacked on one side of the unit. I don't think I will need more than 5V as long as the mah is high. Also I hope to be using Dual Coil cartos so high drain batteries may be better. The third battery slot will be used for the VV circuit. I am also thinking of using a slider pot instead of the dial type and having it just slightly recessed to avoid accidental changes.

I really like the feel of the Weller body in the hand even if it is a little on the large side. The Box mods and large tubes just didn't apeal to me for ergonomic reasons. If I can find the room I will be keeping the existing slider switch and just put a tactile switch inside under it so it still has the slide back safety.

That brings me to another question. With these VV kits, is a main switch necessary to keep the battery from discharging if the control switch has a safety? I'm guessing not but just want to make sure the regulator isn't still drawing power even if the control circuit isn't activated.

I will also be incorporating a heat sink for the regulator but I haven't decided how I am going to do it yet. I am considering cutting a fin or two off of an old CPU heat sink and incorporating it somehow on the outside of the body. Maybe even the heat tube off of one.

All input appreciated and needed...

 

[Gummy Bear]

14500s are the same size as AA.

 

[jmanning]

The MadVapes VV circuit is a nice. You might also look at this. It is a switching regulator, so no heatsink to worry about. I am using one right now and it works great.

 

[outofjuice]

The MadVapes VV circuit is a nice. You might also look at this. It is a switching regulator, so no heatsink to worry about. I am using one right now and it works great.

i would have to agree on the uses of switching regs... but... they are much bigger then linear regs....
if he has room i would say go for it... IMHO

edit- a good link on switch regs
http://www.e-cigarette-forum.com/forum/battery-mods/114901-evercool-variable-voltage-mod.html

 

[outofjuice]

I am considering cutting a fin or two off of an old CPU heat sink and incorporating it somehow on the outside of the body. Maybe even the heat tube off of one.

sounds sexy... post pics if you do...

 

[bstedh]

I was considering a switching regulator but my main consideration was space as the plan for a slider would take up a good portion of the AA slot that everything will have to squeeze into. I may not be able to use the board and have to use wire to connect everything just so it can be positioned in a way to fit. Unlike the AA boxes the battery slots are round and not square so I loose some space there.

Also I am hopping to have enough room left to add a usb charging circuit to make it a Battery PT and a digital voltmeter display. Not sure if I will be able to make that happen as the only charging circuit I have found so far is way to big and the MadVapes voltage display is fairly large also. The 4 battery version of the Weller may have enough room for all of this but it is a bit bigger than I want to go ergonomically.

I may have to forgo my plans on a slider pot just because of how much room it would take up.

 

[jmanning]

The Murata one I am talking about, the OKR-T/6, is smaller than the MadVapes circuit and requires no external caps, just the trimmer pot.

 

[bstedh]

I took a look at the spec sheet and it looks like it fits the bill perfectly. Also I have some coax center pins that would work perfect for making a simple socket type connection for the entire chip. Some serial adapter pins may work good also.

I really liked this portion of the spec sheet...

Output Short Circuit Condition
When a converter is in current-limit mode, the output voltage will drop as the
output current demand increases. If the output voltage drops too low (approximately
98% of nominal output voltage for most models), the magnetically
coupled voltage used to develop primary side voltages will also drop, thereby
shutting down the PWM controller. Following a time-out period, the PWM will
restart, causing the output voltage to begin ramping up to its appropriate value.
If the short-circuit condition persists, another shutdown cycle will initiate. This
rapid on/off cycling is called “hiccup mode”. The hiccup cycling reduces the
average output current, thereby preventing excessive internal temperatures
and/or component damage. A short circuit can be tolerated indefi nitely.
The “hiccup” system differs from older latching short circuit systems
because you do not have to power down the converter to make it restart. The
system will automatically restore operation as soon as the short circuit condition
is removed.

 

[bstedh]

I am thinking of using a trimmer like this as it looks like it can be adjusted by fingers... Hopefully I can figure out a way to have it stick out the casing enough to be able to grip it.

The smallest ratting I am seeing is 1K so I may need to add another resistor in parallel to get the resolution I will want for adjustment between about 3.5V and 5.5V.

 

[jmanning]

I used a 200/220ohm trimmer similar to that in series with a 200ohm resistor.

this or this

 

[rondodog]

The MadVapes VV circuit is a nice. You might also look at this. It is a switching regulator, so no heatsink to worry about. I am using one right now and it works great.

I've used this Okami regulator and it works great and it's as small if not smaller than the TI switching regulator.

 

[jmanning]

I've used this Okami regulator and it works great and it's as small if not smaller than the TI switching regulator.

I have used both this one and the TI, and this one is definitely smaller, and no external caps are required. Price is not bad at all either.

 

[bstedh]

This is what I have come up with to adjust the Regulator with a min of about 3v and a max of about 6v.

I hope everyone finds this helpful. I used the circuit diagram from the data sheet on the Regulator.

edit: picture is not big enough... I will re-post with Google.

 

[bstedh]

Edit: Had to fix my circuit... Been way to long from the last time I had to do this

One thing I noticed is that at the lower voltage you have more resolution and as you get closer to the higher voltage it will start to increase faster. This works for me as I think my preferred voltage will be around 4V.

I may make R2 a variable resistor also so that I can adjust the range of the min max...

 

[bstedh]

Ok.. enough planning. My DigiKey order is placed!!! Also placing an order for some batteries and a charger.

 

[bstedh]

Another adjustment to the trimmer circuit...
This allows you to vary the high end of the voltage

Too much delta on the voltage curve... going to skip this implementation...

 

[bstedh]

I really need to quit trying to design circuits in the middle of the night....

uuuugh... It will take a week for all the pieces and parts to come in. I might have to go up to my uncles machine shop this weekend and see what ideas he may have for the perfect mod body shape. ...oh oh new thread idea...

 

[rondodog]

I really need to quit trying to design circuits in the middle of the night....

uuuugh... It will take a week for all the pieces and parts to come in. I might have to go up to my uncles machine shop this weekend and see what ideas he may have for the perfect mod body shape. ...oh oh new thread idea...

Let us know if your Uncle has any input....always curious to see new mods.

 

[bstedh]

Another thing I am going to add is a couple of contacts on the outside of the body to take load measurements with a multimeter, as the little voltmeter from madvapes says it won't work with some switching regulators...

 

[jmanning]

If the MV complete voltmeter is made of the same voltmeter component they sell, it works fine with the Murata/Okami switching regulator. I have one and it works fine with it.