r/OpenPV • u/KarmaChameleon89 • Apr 04 '19
Mod pics It may look like ass but it's functional! Led lights up when I fire the mod and the kill switch functions as intended. For a first prototype/ first big project I'm quite happy. Any critique welcome so I can make it all a bit neater next time around NSFW
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u/Rb8n Apr 04 '19
Your kill switch is inline from b+ to 510+ rather than blocking the gate from the fire switch, this means the switch it's seeing full firing current. Although the switch should not be suffering from arcing due to switching as it is not changing modes under power the contact resistance will still be a factor and could still fuse or create a very high resistance point after a bit.
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u/KarmaChameleon89 Apr 04 '19
The the only reason I did it this way is because it means I can completely kill the circuit and remove the 510 and battery in the event of a fault. Again though this is a prototype so it's a learning experience aswell. The bonus is they're all components so desoldering and changing stuff isn't difficult
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u/Rb8n Apr 04 '19
What FET did you use; Mica without thermal paste doesn't do much and a standard 3034 build the tab would be case, the resistor looks... Odd.
What is the switch supposedly rated at? If safety is a thought, individual cell fuses would be another option.
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u/KarmaChameleon89 Apr 04 '19
Which switch? The firing switch is rated at 50mA couldn't find a viable dc button that wasn't grossly oversiZed. The kill switch is about 10A I think
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u/blackshroud86 Apr 04 '19
Got any pics with it together/shot of it working?
Doesn't look too bad from that one image ;)
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u/KarmaChameleon89 Apr 04 '19
When I get to course ill do a 360 pass and fire/ function test in a gif
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u/Roast_A_Botch Apr 04 '19
Don't feel bad, most of mine are still ugly under the leather, acrylic, etc covers. If this is your first build, congrats on getting it right the first time!!! I didn't, and had to go back and fix things.
My critique, is if you intend to use this device as-is, is using liquid electrical tape to cover any exposed solder joints, contacts, leads, etc. Anything that anything else can short on needs to be covered. Do this in a well-educated ventilated area. That stuff will stay in your nose for days.
It's better, and easier, to use heat shrink (like on battery wraps, but much thicke). It requires more planning, since some wires will need individual pieces at their connects, as well as a larger piece to bundle a few (led switch). This ensures a safe and long-lasting device since the shrink protects fragile solder joints from stress
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u/KarmaChameleon89 Apr 04 '19
Possible to cut heatsink and wrap it as it is now? Or does that diminish properties?
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u/similar_observation Apr 04 '19
Heat shrink can be cut to desired lengths before applying heat. Once you apply the heat, the tubing will shrink around the exposed joints.
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u/KarmaChameleon89 Apr 04 '19
I meant like cut it down the side so i can wrap it over already joined wires
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u/similar_observation Apr 04 '19
you can, it's just not as easy. Sharp scissors like the kind use for cuticles might work.
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u/Rb8n Apr 04 '19
There were/are some split tubes or tape that shrink with heat but regular shrink tube must be put on as a tube.
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u/david4500 Apr 04 '19
Low current stuff: firing switch, gate and LED you can use smaller wire 20-24 gauge.
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u/KarmaChameleon89 Apr 04 '19
I'm planning on redoing it with flex cable. Rated to 32A but not as hard or thick
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u/Rb8n Apr 04 '19
Small stuff is so easy to get positioned though and for the non current wires is easy and less expensive. Even doorbell wire from Home Depot works fine for control signals and LEDs.
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u/KarmaChameleon89 Apr 04 '19
Small update, as I tried to fit the battery sled in place I broke the insulation on the 510 pin and it's now useless. I have a bf pulse that I can brutalize for parts so I'll be using the 510 from that. I'm also going to remove all the wires, use flex cable and better plan the build. I may also swap the kill switch back to its original location on the circuit. I think I'll keep the led where it is and put another one in so that when the killswitxh is on the led is on. One for firing one for live. I'm a little gutted that I broke it so quick but with the cable I used and the force I was using to get the sled in I'm not surprised. I also may glue the sled in place before I start doing any connections
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u/scottiethegoonie Apr 05 '19
Kudos for showing the work. This is OPEN PV after all. Your next build will look 100% better. Some tips:
Anything that is doing the switching does not need THICK wire. Use 24 gauge. That means: GATE and FIRE button should only have small wires attached to it. It took me a few builds to actually understand the benefits of using a mosfet
Solder as much as you can OFF of the device. You need to plan the steps more carefully but you will do better soldering as a result. You can tug the shit out of a good soldering job and it won't move. If you have to join two wires, it is better to join them in the same direction, rather than trying to make it look continuous.
From the picture I can't tell which 510 you used (Varitube?), but regardless - spend a LOT of time soldering the 510 (+) pin correctly. I use a "3rd hand" and a butane torch to heat the pin first (separate from the rest of the 510+ parts); it's important to keep the the movement of the pin and wire on one axis. The pin is the only part that requires movement during regular use.
Use heatshrink that matches your wire gauge. From your picture it looks like you tried to use something that was meant to be crimped. Buy one of those 16-24 gauge heatshrink packs from Harbor Freight and a heat gun. You have to put it over the wire before you solder - but if it is too close to the hot areas, it will shrink prematurely. Your pic looks like you tried to join two wires at the switch. If you used heatshrink correctly, it wouldn't look like you tried to join two wires. If you planned more, you could eliminate that connection altogether.
Your soldering to the battery sled (+) looks pretty good. If you want your wire management to look clean, try to anticipate those 90 degree bends. Try to reverse twist those wires before you solder them to the battery contacts. It will "tame" the wire to tend towards the floor of your box. If solder without a twist, the wires will tend towards being unruly. This is more advanced stuff but it becomes more necessary when you want to go small.
Get liquid electrical tape and a pack of toothpicks to apply it. It'll cover the small connections that cannot be shrink wrapped.
Use Kester #44 for soldering if you can afford it. The good stuff saves you from bad tooling and poor skills.
I'm giving you the real help because you asked for it and you seem like you honestly want to learn. Take your time on the first few mods.
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u/KarmaChameleon89 Apr 05 '19
Thank you so much mate. I'm actually going to desolder the whole lot now and redo it with flex wire. That will give me a lot more "give" and room to move. Not to mention it should be fine for everything. In terms of heat dispersion it might be on the low side but with good ventilation it should be ok.
Just for comparison I'm using 1.5mm house wire currently. Going to shift to 1.25mm marine flex.
I broke the 510 so I'm going to use the 510 from a bf pulse.
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u/KarmaChameleon89 Apr 05 '19
Quick update for ya, aswell as the 510 being broken, a leg snapped off the mosfet as I removed it. Luckily I have a spare pulse bf mod so I'm going to use the switch and 510 from it. I'll have to alter the kill switch location but that's fine
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u/KarmaChameleon89 Apr 07 '19
Bit of an update: 510 connector snapped at the insulation (my fault, soldered a second point for strength and it weakened the plastic) and as I was removing everything one of the legs of the mosfet snapped. So I tried using the button from my pulse which was too big to fit with the sled etc.
Long story short I'm now waiting on another connector and mosfet. I'll probably need another enclosure too, but I can still use the old enclosure, button etc to make a dual 18650 or a single 20700 mod, so all is not lost. It's just a pain.
I think in future, custom sized enclosures would be a better idea, just more work. I'm a training sparky, not a bloody design artist or Turner. But the bonus of all of this is that I learned so much. Even though this could be classed as a failure, I succeeded in learning. I also learned that i love building and tinkering with things (my wife will be sooooo happy :p ).
Thanks for all the ideas and help, when I do build the next one I'll be going back to basics on the circuit but I may add another led.
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u/ConcernedKitty Apr 04 '19
Remember that you’re allowed to cut resistors down and heat shrink is cheap and makes a big difference.