Certified FOCBOX Suppliers | Get Focbox Unity

DIY Anti-Spark Bullet Connectors


#1

The picture says it all! I took a little break today while I had some VESC’s in the oven and crafted this little gem. I used three 1K resistors to make it.

I should add that I didn’t just dream this up. I don’t remember the source but I did find it on google images a few months back.


How-To: Anti-Spark XT-90 Loop Key
#2

that’s pretty cool. I had thought about doing this myself, but I didn’t have any SMD resistors laying around.
did you use a dremel to cut the end off the socket?


#3

I used a jewelers saw but a dremel would have worked just as well.


#4

Cool idea !
How do you know the resistance is enough to prevent a spark ?


#5

Very clever, the idea here is to limit the current inrush cause by the bulk capacitor (the big cans) by placing a resistance directly in series with the rest of the circuit.

Chaka’s is placing 333 ohms in series with the rest of the circuit. If he is running a 40V system, that will allow a maximum of 120mA to charge the bulk capacitors and to reduce/eliminate the inrush current once the bullet gets to the end of the barrel.

How do you determine what resistance to put? Well, is 120mA enough to create a spark, I don’t think so. Is 120mA enough to charge the bulk caps in a few mili seconds, probably 90% charge yes. You want that windowed sweet spot.


#6

They were resistors I had from another project. There are calculations you can run to find the sweet spot but these should work fine. I tried it with a 6s pack but I will try a 12s pack later today when I am back in the shop to confirm.

Edit: 12s confirmed! Three 1k resistors is definitely the sweet spot.


#7

this is brilliant! a double layer of heat shrink and it would be tough enough to withstand regular disconnects for a while.


#8

I got another tip for you, drill a hole in a double sided PCB the same size as the internal diameter od the socket and solder the 2 pieces of socket each side trim off the excess and then solder your resistors on.
It will give the socket a bit of mechanical strength other than just that of the resistors.


#9

Genius idea! It would be “bullet” proof.