Archive for BRIT NERF Home of the British NERF Community

       BRIT NERF Forum Index -> Q&A and New members

Soldering questions

Hey all,  I've soldered together my Hellcats with flyback diode into it's own loom with Xt60 connector and tested.  It works!  Whoop! I ran them on a 6v test pack (Stryfe)  for about 20secs.  The solder points got very hot.  Is this normal?

Also,  the heat shrink I applied to the xt 60 shrunk before I could get them over the terminal on the clip and there are a couple of other places I want to put more insulation.  Can I use electrical tape to complete the insulation? Or is there a trick to applying heat shrink after the join has been made?

Check your MOSFET and flyback diode is wired the correct way around. It sounds like you've got the diode around the wrong way. Check you've not got a short somewhere.

E-tape will work just fine for insulation, it's not ideal but it'll do for the situation at hand. Smile

Thanks boff

The Mosfet isn't in the loom yet,  it's just the motors with the diode backwards against the typical current (or at least I think it is..  Do the BSUK ones come with the red tag on the positive and the white on the negative?) positive on the negative side back to the positive side..  That's right,  right? Could possibly be shorting against the motor housing though the motors were running fine and I saw no sparks (some flux evaporated as I did it though)

The silver side of the diode should go to the positive side of the motor terminal. Ignore the paper tapes on the diode leads, they're only there so I don't have to bend the leads separate.

And yes, check shorting against motor housings. Have you got a multimeter with a continuity testing?

Arrgh.  So the silver side of the diode is the negative side and therefore has to be joined to the positive side?
EDIT : multimeter = not yet but I'm starting to see it needs to be on my Xmas list
EDIT2: pics:
Loom with diode in between motors

Particular joint that got very hot


If you look at the diagram the silver bit is represented by the line there. What you're getting is a short because your diode is allowing normal current flow rather than blocking it. Remember, its role is to block back EMF and protect the MOSFET from going pop.

Okay, thanks for helping me identify the problem boff. Cheers.

When applying the heat shrink  (especially if it's a tightish fit to begin with) allow the join to cool down first, if you don't the heat from the join can cause it to start shrinking as you slide it over.

I would change both the position of the diode and the wires to the main loom, as well as swap that XT60 for Deans.
You should use a bridge wire between the terminals to which the loom attaches, not a loop through like yours. If you use your method the second motor can receive less current than the first and the motor tags are sometimes placed under more stress, depending on the angle of the main wiring.
Deans are better for motor block plugs because they are much more compact and the Britnerf standard, so if you were to order an FWC from another builder here the default connector would be deans. I can send you a spare pair of Deans if you need one.

Slightly OT but, does anyone use/recommend liquid insulation tape? Heatshrink can be awkward on small parts and joins, I've heard of but never used the commercial products and diy bodge alternatives... It doesn't feel like good practice tbh...

If you get a good quality one its a better alternative to insulation tape but I would only use it personally if there's no way of using heatshrink or sleeving.

TBH what first made me curious was finishing a lovely soldering job then noticing the lovely pre-cut heatshrink sections lying on the desk  Laughing

Haha Northwind. I've been soldering 5 mins and must have done that 5 times though I think I'm getting in the rhythm now. ..still going to look for that product though.

Sparky yeah, it was a good fit heatshrink though unfortunately despite me having it a good way away I managed to take so long it shrunk slightly on the wire before I moved it down.. May start putting one snug and one loose on each wire.

OldNoob when I was sourcing all the bits for this I mixed up deans and xt60 in my head so I've got a load of them. TBH I got stuck for so long on this waiting for parts that now I have them all together I want to crack on, though I will change on future builds and potentially retrofit once i've changefd my packs over, as all I've heard about is how much easier they are to use 😊 fortunately the Modulus isn't short for space and I don't intend on buying any pre-mades.. Not that i suspect the products only i want to learn all the skills and make things that are all mine.  
Interesting what you're saying in regards the wire positions over the motors, is the chance of lower current due to the additional resistance of the wire?
which case couldn't you solve by reversing the approach of one of them to the opposite direction? (Not saying I would just interested).
In regards the additional tag stress, would that be because any tug would just affect the first tag, whereas a bridge wire would mean any tug should be spread across both tags?

       BRIT NERF Forum Index -> Q&A and New members
Page 1 of 1
Create your own free forum | Buy a domain to use with your forum