Mosfet wiring?

Mr Monkey Nuts

Mr Monkey Nuts

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I'm in the process of building a V2 gearbox and getting to the wiring. I have a GATE PicoSSR2 Mosfet to put in her, but the instructions list two different installation methods.

This is taken directly from the Rules



I understand the concept of both, what I don't understand is why figure 3 is the optimum setup? And why it doesn't require a "wire 5"?

It will be running a 11.1 25c, down 16awg and deans, rear-wired. if that helps?

 
Both setups require both sides of the contacts to be connected. Fig 2 is easiest but needs an extra wire adding to create voltage across the contacts (else there is no trigger signal), fig 3 is simpler to install but requires more wires to be removed in the first place

 
Ok, that makes sence. So what about wire 5 in figure 3 is it just not required? It says it should terminate as close to the battery as possible but inst drawn onto the diagram.

 
2nd one or fig 3 is the main one most use...

desolder one of trigger switch wires and pop onto the other side

the thin mosfet wire then goes onto the original point and runs back to fet

less messing about, 1 thin extra wire as has been mentioned

more important say on rear wired ver 2 - only 1 extra thin wire is passing

by the motor entry on ver 2 gearbox !!!!

where as using the other fig 2 - you would also have wire 5 & 4 as well as wire 1

passing just behind motor spindle = 3 wires......

OOOppppsssss - I did start to really waffle on about new rewire installs and even by my

standards I was going way way too much into detail about pro's con's and another diagram

then thought - ahh sod that war n peace novel

just say to OP - go with the "usual" or preferred method - 2nd pic or fig 3

Just one thing - dunno what speed or rof you are putting together.....

maybe don't test it all out straight away with 11.1v unless you are sure you done your homework

you may find with the increase response & rof you may get pre engagement if you go too mad

(says the duck with yet another "2 part piston")

 
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Take my advice and do not use the thin wire they supply as the signal wire. The reason is because it is so thin and the insulation is not very robust. If you allow even the poxiest short through compromised insulation it will cook the MOSFET (I have done that to a Pico SSR v1 and with an 11.1V LiPo connected up the short can be due to a spark jumping from an insulation compromised trigger wire to the gearbox shell). Instead, since you are replacing the stock wiring with 16AWG, use a piece of the original loom as your signal wire. Just make sure that you choose a piece without any squashes/grazes where it has been badly crushed between the GB shell and receiver.

 
You can also run the signal wire outside the gearbox if room inside box is getting tight

(out of front and carefully back to fet in stock if you use the thinner 22/24awg supplied)

I ran a wire on the opposite side of selector plate carefully on a ver 2 box (rear wired setup)

In fact this keeps the signal wire even shorter than inside box with its cramped " U " bend

(only a few inches but they say keep this wire as short as possible)

I was gonna go into more detail & options but trying to keep it brief

besides I presume by now you got it all sorted anyway

 
^^No doubt the reason they recommend keeping it short is because it is so poxy :lol: Resistance of the signal wire is not an issue, so the length need not be an issue either, just so long as however you build the new loom you provide for heatshrink to protect any high wear areas and, if you are daft enough to use that capellini that comes with it, to bundle it with the power cables to reinforce its strength in tension.

 
Haven't done a ver 3 fet just yet - hey I'm a poet & didn't even know it

but ver 2 can be a pain in butt with its " U " bendy motor wire crap, where as

ver 3 motor wires are kinda external - not saying for 1 sec v3 are easy - no sir

but when putting in thicker wire it can be a bit tight inside v2's - some box's are worse

This is even more true if using the usual method of (no wire 5)

So in effect you have to connect 2 x 16awg's to one side of switch & not so thick wire 4 to other

In hindsight think it might have been worth considering joining 2 x 16awg's together say an inch

just before switch plus a thinner old bit of 18awg original wire all shrink tubed up of course

then the thinner wire would of been more neater at switch, trigger, safety lever and not have 2

thicker awg's running near them. (it was nearly catching/rubbing on trigger/saftey lever but kept 'em out of way)

If using say slightly thicker 14awg then this could really intrude even more at switch area as well as " U " bend

and I was gonna go with the other method of using dedicated fet feed/return with wire 4+5

So a direct 16 or 14 awg link to motor - keeping all thicker wire easy n simple and just the old or thinner wire

connected to switch - but meant 2 thin or thinner wires going to fet - if running outside of gearbox would there

have been enough room on ver 2 box - deffo I think on ver 3 coz many wires run outside box to battery....

Hmmmmm - ok will go with "usual method" no wire 5 and see........

yup was ok with one wire running along outside - just below piston/spring of box and passed back into rear of

receiver where the 2 main wires appear - fet signal wire can be pulled either way so not too tight or snagging

damn wish I used a tiny bit of duct tape to secure this external wire but she is in there now and as long as I was

careful when remove/refitting upper receiver that single external wire 4 will be fine - will tape/secure it next time

the box comes out - it does not hit or restrict magwell or mag catch and if I went with 2 wires then suppose I could:

run wire 4 on selector side & wire 5 on other

or

probably just make a small nick/cut/groove if required where box & receiver meet

the wire(s) to fet don't need to be very thick but yup re-using the old loom is a good option

(what else ya gonna do with the old loom anyway)

But though they taking 9-12v say the load/amps is tiny so thinner wire can be used but with care though

Even the main 16awg wire used can make the whole process easier or more fiddly

if using slicone/rubber 16awg then the wire+insulation will be nearly 3mm thick plus though this

is very flexible even the thicker insulation can split/damage easily

ETFE or PTFE 16awg silver coated wire is at least 1mm thinner as insulation is thinner but still

offers same degree of flexibility

OOOOOOooooooopppppppssssssss

Soz rambling away a bit - gonna leave it there me thinks - I'm still not happy with the old skool switch

and still playing with ideas on a cheaper simple replacement - yeah simple that is laugh

(nothing I do or try to explain is simple or straight forward - soz a short simple answer from me is impossible)

 
jeez what a load of ol' bollox I type

even I'm having trouble getting my head round the above crap

AND I typed it ffs - well bored so thought I'd show a pic to show what I'm on about....

BUT seems as if I have used up my allocated disk space on here so unless I link it

on ext site or go back & edit my piccy posts I can't seem to attach a file no matter

what size/format I use - damn it

Oh well looked in my profile/settings but can't seem to figure out easy way to show ya

3 or 4 pics and the external alternative fet wire on ver2 CM18 and other stuff

well guess you can figure it all out but does clear magwell & not interfere with mag rel button

and as long as you don't use very thick wire she will pass out the back to other wires exiting box

reckon you can work it out what I mean but a pic says 1,000 words and would reduce the crap I type

 
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NB: Silver wire demonstrates the path it takes and misses mag rel + clears magwell completely

just route it carefully with some common sense and finish with a bit of tape to finish.....

allow to cool before eating - soz wrong pic/forum

yup top receiver clears it too - I used a sprinkle of common checking sense in this recipe

final yup - stock spacer ring still fits on there too but everybody will have slight different guns

so some little groove may be required for some others but all the same.....

If space is running a little tight inside box then you might wanna consider running fet wire externally

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yBZkU4X.jpg


 
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You may have good points to make, SD, but I'll never know because reading your posts taxes my patience. The reason we have arrived at a commonly agreed structure for sentences and punctuation is because, once you know it, you can say anything to anyone who also understands the format, with the minimum of ambiguity, confusion, long windedness, etc.

I lost you just after you suggested using a thinner piece of wire to actually connect to the switch in a V2 gearbox and connecting that to 2 joined 16AWG further out. This may well be an easier way to accomplish the task, but it introduces a higher resistance section to the circuit. If you physically cannot fit 16AWG all the way to the switch, you may just as well use the thinner wire for the whole circuit - electrical resistance works just like water through a hose - if you constrict the hose for one foot out of 24 say, it is the same as 24 feet of thinner hose when it comes to how much water can get through.

If you cannot fit 16AWG all the way, you could consider using 2 lengths of thinner wire side by side to get past a constricted space - next time i open up my Scorpion I'm going to do this for the length of wire between the brass connectors from the grip to the motor, because there isn't enough space between the gearbox and receiver to fit anything thicker, although TBH the ROF since i fitted a Pico AB and 7.4V LiPo is such that the resistance of the thinner wire may be all that's preventing the motor from burning out! I am looking to upgrade the motor though...

 
Ian_Gere said:
You suggested using a thinner piece of wire to actually connect to the switch in a V2 gearbox and connecting that to 2 joined 16AWG further out. This may well be an easier way to accomplish the task, but it introduces a higher resistance section to the circuit. If you physically cannot fit 16AWG all the way to the switch, you may just as well use the thinner wire for the whole circuit - electrical resistance works just like water through a hose - if you constrict the hose for one foot out of 24 say, it is the same as 24 feet of thinner hose when it comes to how much water can get through.
Click to expand...
Click to shrink...

Nope - soz I can't see how that will matter

As long as the the 2 positive 16awg wires are joined/soldered together to ensure the final supply is in 16awg

then it wouldn't matter if a tiny thin "spur" wire is taken off this joint or if it was all joined at switch terminal

The switching of fet requires a tiny tiny amount of juice

there is virtually hardly any real drain on the fet being triggered

in fact the only real problem is when the motor switches on taking a large load - but this happens whatever way

you wire the switch circuit - just 1 wire#4 or with dedicated new wires #4+5

As long as the 2 positive wires are joined as best as they can be it matters not if you take a spur off to switch

in household terms - this "spur" is in effect just going to power a tiny nightlight so it would NOT HAVE TO be in 2.5mm twin/earth

Before anyone says my DIY sucks - for obvious reasons I would run any spur socket in 2.5mm twin earth in case somebody

tries to run a kettle on say a 1.0mm cable - I was just trying to give an example of how 16awg at switch is not a must have

or

if you run the other diagram with dedicated 4+5 then they can be in 24awg - maybe even 26awg at a push

the switching of the fet really needs next to nothing - however when it does trigger then the Negative output DOES NEED 16awg

that one negative line is the main drain and is in 16awg - also the Negative supply to fet's circuit must be in 16awg of course

but the fet's positive supply is not that critical to be in thicker wire

But agree it should be be sufficient enough and above all the insulation should be in perfect condition

The Motor needs 16awg and that is it - the trigger - either side of it does not like in wires 4+5 can be quite thin

and see no reason how a 24awg spur will cause more resistance as long as them 16awg's are joined correctly

(and insulated of course coz that is some mofo current there)

 
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soz for slight ranty ramblimgs - i know I talk bollox 99.999% of time.

I also may have not perfect grammar too and like I said either here or on my Silent AOE posting - even I find it hard to understand the $hit I type

hence pic of my external fet wire shows what I was rambling on about

soz again coz I'm starting to ramble once more :)

 
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