gdeals tricked out Reo - mosfet switch/fusses/lowered atty/etc - PICS :D

[bapgood]

I have wanted to try a Reo for quite awhile and gdeal had been talking to me about vdrop issues and fuse options, so I had him send me his Reo so I could get a test drive and possibly trick it out while I had it.

Here is a list of the modifications I did while I had the Reo

- Mosfet switch with atty matching SS button for tact switch
- PTC Resettable fuses
- SS center pin and delrin insulator/seal
- Lowered the Reomizer 2.0 rba
- Spring from the top of a sigelei 19


Before we get into the fun stuff (pics)....I just want to say most of the mods weren't needed to reduce vdrop and were done just for fun.

I had talked to gdeal quite a bit about the vdrop issues he was having and after receiving the Reo and looking it over, the one thing that stood out to me was the spring battery contact. In stock form with a 0.8ohm coil and freshly charged and pretty new 1600mah AW 18650 I was getting ~3.72v under load measuring at the coil connection posts. Having seen spring battery contacts like the one used in the Reo have issues in other PV mod applications, it was where I wanted to start. I simply put a hot spring over the top of the stock spring and bent it so it was making good contact on the spring plate. Same coil/battery/etc and I got 3.95v under load....Thats a gain of almost a quarter of a volt. Which both myself and gdeal thought was a significant improvement.

Since I had the Reo I figured I would go ahead and trick it out a little more than just changing out a spring and adding some fuse protection, so I got gdeal to sign off on the additional mods and I went to town.

I have used both the PTC resettable fuses and low profile mini blade fuses in other applications. They both have there advantages and disadvantages, but the PTC resettable fuses provide solid protection and don't need to be replaced every time they are tripped. So I used three of the PTC resettable fuses in parallel, this reduces the resistance the fusses impact on the circuit and gives protection for a dead short situation.

Since I was getting rid of the stock lever and button firing parts I decided I would make a SS center pin that was a little more solid when installed. So I used a 3mm SS screw modified for use in the Reo and made a delrin insulator/seal. once installed and tight its very solid and leak free.

I thought the Reomizer atty looked a little bit off setting up like it did so you could see the step and brass. So after some trimming and some food safe silicone to seal the threaded holes that were now open in the base, the atty sets down a bit and looks better IMHO.

Ok enough blabbing....picture time

 

[bapgood]

Forgot to mention that I got 3.96v with the final mosfet and fuses version.

 

[Dturp]

It's very nicely done. I prefer my mechanical to stay just that but I have to say that is very very clean and nice looking. Impressive results as well.

 

[super_X_drifter]

That's like the bionic REO. Nice work bro

 

[gdeal]

Bap, very nicely done! What type of PTC fuses did you use and what is the amp trip?

BTW thanks... you got mad skilz.

 

[bapgood]

I will dig up the spec sheet on the fuses tomorrow

 

[pdib]

Wow! Fancy! Bapgood, how do the three fuses in parallel work? Is 1/3 the current running through each one equally? does the current favor one of the fuses sometimes? Why is the resistance less; because less amperage is running through any particular fuse and creating less "excitement"/resistance?

 

[pdib]

BTW: there is a ton of artful work in this mod, so don't take it the wrong way; but I'm thinking of this↑ as the Louis the 14th version.

Here's the Karl Marx version . . . . . .



0.13V drop on a 1Ω coil

http://www.e-cigarette-forum.com/forum/reos-mods/472662-spring-what-spring.html

http://www.e-cigarette-forum.com/forum/reos-mods/467679-dz-mod-ok-pdib-too-3.html#post10689140

 

[Matthee]

Know nothing about the technical stuff, but like the final result!

 

[bapgood]

pdib - gdeal turned me on to a dz mod and I briefly looked thru it and your spring? thread. Give me a little bit and I will delve further into the fuse specs and etc. I also have a used low profile mini blade fuse similar to what you guys are using and have some fuse holder info you guys might be interested in that I will dig up also.

Here is a pic of the fuse and holder

 

[bapgood]

Ok...Fusses ....Fuses

how do the three fuses in parallel work? Is 1/3 the current running through each one equally? does the current favor one of the fuses sometimes? Why is the resistance less; because less amperage is running through any particular fuse and creating less "excitement"/resistance?

Yes running the PTC fuses in parallel reduces the resistance by the number of fuses as well as increases the current trip capacity. So if you use two 5 amp fuses, you cut the resistance by half and double amps to 10 amps.

Specs are below....PTC fuse specs are based on ambient temp, but to keep it easy the fuses I used are ~5 amp trip....so gdeals Reo has ~15 amps before the fuses trip. Myself and gdeal weren't so much worried about battery protection (as gdeal is keen to how this all works and what his batteries specs are), and more about dead short protection. So we felt the ~15 amp trip would allow him to run pretty much any coil he would want to.

I was going to test it anyway, but fate stepped in before I intended and they do indeed work .

There is one downside to the PTC resettable fuses, and that is they will build up internal resistance every time they are tripped. How many times and etc????....I'm assuming that will all depend on the qty of times and the severity and length of time that they are in the tripped state. Also should be mentioned that unlike the automotive blade type fuse which completely disconnects the circuit when its tripped, that the PTC fuses don't (well until they fry internally, or get hot enough to unsolder themselves). But that would require the button to be pushed while in a dead short situation and go unnoticed, which is unlikely but possible.

Here is a bit from wiki on PTC fuses
"A polymeric PTC device comprises a non-conductive crystalline organic polymer matrix that is loaded with carbon black particles to make it conductive. While cool, the polymer is in a crystalline state, with the carbon forced into the regions between crystals, forming many conductive chains. Since it is conductive (the "initial resistance"), it will pass a given current, called the "hold current". If too much current is passed through the device, the "trip current", the device will begin to heat. As the device heats, the polymer will expand, changing from a crystalline into an amorphous state. The expansion separates the carbon particles and breaks the conductive pathways, causing the resistance of the device to increase. This will cause the device to heat faster and expand more, further raising the resistance. This increase in resistance substantially reduces the current in the circuit. A small current still flows through the device and is sufficient to maintain the temperature at a level which will keep it in the high resistance state. The device can be said to have latching functionality. The critical material, which is a carbon black and plastic mix, used in the automatically resetting devices described in this article, was serendipitously discovered and then described by author and scientist Fred Kohler, and patented as US patent #3,243,753 on March 29, 1966.[4]"

Here is the link to the fuse I used and the spec sheet is below

 

[bapgood]

Here are the links to the blade fuse holder parts (you purchase the clips and plastic housing separately)...I believe this will hold both the low profile mini blade fuse as well as the normal blade fuse.

Clips

Housing

Housing spec sheet

 

[bapgood]

Wow! Fancy! Bapgood, how do the three fuses in parallel work? Is 1/3 the current running through each one equally? does the current favor one of the fuses sometimes? Why is the resistance less; because less amperage is running through any particular fuse and creating less "excitement"/resistance?

I realized I didn't answer your questions very specifically, so I will try below. Mind you I'm not a EE or even close

Is 1/3 the current running through each one equally?

Yes, this is my understanding.

does the current favor one of the fuses sometimes?

My assumption is that is possible (following the theory of the path of least resistance), but that they should typically equal out. Unless one were to fail or something.

Why is the resistance less; because less amperage is running through any particular fuse and creating less "excitement"/resistance?

Yes, that is one way to put it. My understanding is that more amperage running thru the fuse the higher the temp is, as well as the resistance.

 

[pdib]

Thank you, Bapgood.

Purely imagination . . . but I suppose that, if the current were to favor one of the fuses, it would get a bit warmer and resist more, becoming "unfavored". So, it balances itself out in an imperceptibly fast, almost not even happening, kin'a way. (←science talk )

 

[pdib]

I think I see what you were saying. Looks like about a 5 second trip? No battery protection, but yes catastrophic protection. Of course, I didn't see numbers/categories like I did with the auto fuses we are using (trip time @ 360percent of amp rating . . . @ 600perc. amp rating . .. .etc.)

Ours is set up to trip in about 0.3 sec. (based on approx. 30 amp load for 10 amp fuse).

 

[bapgood]

I think I see what you were saying. Looks like about a 5 second trip? No battery protection, but yes catastrophic protection. Of course, I didn't see numbers/categories like I did with the auto fuses we are using (trip time @ 360percent of amp rating . . . @ 600perc. amp rating . .. .etc.)

Ours is set up to trip in about 0.3 sec. (based on approx. 30 amp load for 10 amp fuse).

I'm not sure what that 5 second trip is based on and etc, but it didn't seem like 5 seconds to me. Before I made the delrin insulator I had tightened the center pin thru the silicone piece that was in there, basically tightened the center pin to the 510 body. As soon as I hit the button I heard a faint pop or snap. I immediately took everything apart and none of the electronics or battery were hot, put it back together with the new insulator and everything work again????

 

[pdib]

Oh, cool! (I thought I saw it on the spec. sheet . . .. maybe it said .5?)

anyway, your mod (your combined moddage) is beautiful! Gdeal has got himself one sweet REO! (he pro'ly doesn't deserve it , gdeal)

Rob (REO) has been looking for a way to set up the REO for better v-drop that is less accessible to the end user. (i.e. somebody can't just shove a plug in a fuse slot and disengage the protection). ChrisEU has been researching/testing PTCs. Looks like some version of your fuse mod is the way forward for production!

edit: nope, it says 6amp 20degC 5sec. (still, that must be MAX)

 

[bapgood]

I didn't get into the nitty gritty of the mosfet switch, but I will give a brief description and some info a ECF member gave me.

Parts used
- N-Channel Mosfet
- Tact switch
- Tact switch button
- Gold plated contact probe
- 47k ohm resistor (just one I had...nothing fancy needed)
- Brass plate (Lowes)
- Spring (Top spring from Sigelei 19 mech tube mod)
- Custom made 3mm center pin and hex nut

I just routed out the Reo top delrin plate to fit the brass plate that I soldered and glued the components to and hold the brass nut I made. The spring was soldered to the brass plate after it was glued into the Reo top plate.

I wanted to use a n-channel mosfet to switch the ground, so that is why the battery and spring are reversed from the stock configuration.

I just used a dremel work station to router out the top plate




The plain tact switch button even fit pretty good and didn't look to bad






Below is some info on using a mosfet to make a switch. Most of the below information came from DrMA when he helped me on a different project.

I'm usually of the opinion that N-channel MOSFETs make better switches, because they tend to have lower resistance [RDS(on)]: i.e. low-side switching. Assuming you'll be using just one LiPo (nominal 3.7V) when picking a FET to work with, look for one a VGS(th) <1.5V, enough current to support your application +50% [ID(on)] so it doesn't overheat, and appropriate breakdown voltage (VDS > 4.2V)

Here's a very nice and easy to understand guide: Using the Power MOSFET as a Switch - MOSFET Switching

Here's the basics of FET switching:
- use N-channel FETs to switch the ground (low-side switching). Gate needs a pull-down resistor for OFF, and gets connected to the (+) side of the batt for ON
- use P-channel FETs to switch the (+) connection (high-side). Gate needs a pull-up resistor for OFF, and gets connected to ground for ON.

In general, P-FETs have higher resistance than N-FETs.

In a P-channel FET, current flows and gets switched in the direction Source->Drain. The body diode is reverse biased with respect to S->D

In contrast, for a N-channel FET, current flows and gets switched in the direction Drain->Source. The body diode is forward biased with respect to S->D

The resistor is used to bring the Gate potential to reference when the switch is off. It also functions as a current-limiting resistor when the switch is on, so you don't short the battery. You want the highest resistance value that accomplishes a full off state with the switch open. You'll need to play with the resistor value to get the desired results. I'm guessing it would be between 10K and 50K. This is where a variable resistor comes in really handy.

Here are some simple diagrams that DrMA provided and then I added some info.


Low-Side (negative) Switching using a N-Channel MOSFET. (This is what I did on gdeals Reo)



High-Side (positive) Switching using a P-Channel MOSFET.

 

[bapgood]

Oh, cool! (I thought I saw it on the spec. sheet . . .. maybe it said .5?)

anyway, your mod (your combined moddage) is beautiful! Gdeal has got himself one sweet REO! (he pro'ly doesn't deserve it , gdeal)

Rob (REO) has been looking for a way to set up the REO for better v-drop that is less accessible to the end user. (i.e. somebody can't just shove a plug in a fuse slot and disengage the protection). ChrisEU has been researching/testing PTCs. Looks like some version of your fuse mod is the way forward for production!

edit: nope, it says 6amp 20degC 5sec. (still, that must be MAX)

Now you have me curious....I will have to test this a little bit

 

[ChrisEU]

Heh, great work.

Funny how people come to similar conclusions from different angles. There must be something right I guess =)

I don't know the plan of the circuitry, but I can see a micro switch and a ground spring, so I can guess how it works and yes, that's a full mod and, as far as I can see, not reversible and that's a goal for what I do. If the electronics stuff fails I want to be able to just rebuild it to pure mechanical.

Did the ground spring make problems getting hot or anything, that's the one thing I would like to avoid?

BTW and OT - the teflon buttons work well, although they are a tad too small. My single 7A PTC trips faster than their melting point and it all looks well.

I have another, almost new REO Grand incoming to test the setup on the latest version of the Grand. If it works well I will ask for help on creating a holder that can be used instead of the spring.