BB Unit on on antweight

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Wigs
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BB Unit on on antweight

Post by Wigs »

Hi everyone,

Bit of a shot in the dark but I hope you don't mind me looking for help here.

I have a working tracked vehicle and I wish to add this BB firing Unit (A spare for a Heng Long RC Tank) and get it to fire via the Hold 0 switch on the Devo 7E. It's using an Orange RX receiver, don't know exactly which.

If it's possible, my challenge is to work out how to wire it. The BB motor has a + and -ve although I don't know which is which as it's unmarked. I think the BB unit is ok to run from a 2S Lipo.

The other part of this puzzle are the 2 wires coming from what I think is called the return switch. I think one wire will have to connect to the motor positive or negative and the other wire, from the return switch, would become the signal wire.

So would end up with +, -nve and signal all going into the Orange and then fired via the Hold 0 switch on the Devo 7E

I am very much a novice at this, I have built a few antweights but never tried anything like this (I know I can't use shooting things in an arena, it's just a home experiment)

If anyone can please offer any advice or help it would be fantastic thanks. I have looked around a fair bit on the internet, lots of RC Tank forums etc. and can't seem to find a diagram that shows me what the BB Gun unit wires are.

Thanks again and all the best

Adam
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Re: BB Unit on on antweight

Post by Wigs »

Great tip on the Image @EddieJ thanks

I have numbered the connections if that helps with any discussion :)

https://ibb.co/rZ9Hc7V
Last edited by Wigs on Sat Feb 20, 2021 3:17 pm, edited 2 times in total.
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Re: BB Unit on on antweight

Post by EddieJ »

Try this for uploading images to show us all :)
https://imgbb.com/
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Re: BB Unit on on antweight

Post by Wigs »

lol, got the image up and now it looks like imggbb.com is offline
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Re: BB Unit on on antweight

Post by EddieJ »

That works :) Ok so i am pretty green with electronics too, so this might be like the blind leading the blind, but here goes :lol:

You have a brushed DC motor there, so if you wire it up backwards it will just spin the wrong way. I'd say just see which way works to operate the mechanism. Shouldn't hurt it.
From what tinkering I have done, the darker wire is usually the -negative and the lighter is the +positive, but that would just be my educated guess.


Im not sure what the term "return switch" is though. Is it an electronic component like a ESC? Or a mechanical switch?
If you just need to spin the motor to fire this BBs, i would just wire up a brushed ESC to it and hook that up to your receiver and power.

First thing, power that motor up, maybe start slow with 3-4V and see if it will fire BBs from just that :D
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Re: BB Unit on on antweight

Post by Wigs »

Thanks EddieJ,

Great point about using a brushed ESC, will dig through the spares and give one a try. I picked up the term Return Switch from a YouTube video of someone replacing a BB unit in his tank. So I have no idea if it's correct or not.

On looking closer at the Return Switch, https://i.ibb.co/q9BjBd4/firing.jpg it looks to me like the gun spring winds backwards and eventually mechanically closes the 2 contacts of said Return Switch, which I guess is then supposed to stop the motor winding back, allowing the spring to fire the BB.

Thanks again for your help, very much appreciated
Adam

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Re: BB Unit on on antweight

Post by EddieJ »

I get it, so when the pads connect, the motor wants to switch off and the gun fires. That's going to be hard to do. Or at least, it's beyond my skill :P maybe someone better at electronics will drop by with a solution soon.

But if it were me, I would just ignore the switch completely, time how long it takes for the motor to draw back the "bolt" and prime a BB. Then set a switch on your TX to switch the motor on for that amount of time per switch toggle. If your TX has this kind of feature.

It's not perfect, but will have the thing working at least :D
It would also be better to under-wind (reduce the time by 0.25seconds than what you timed in reality) the spring a little, than overwind it and damage the mechanism after lots of shots. You also want to make sure you have the same voltage so the motor is spinning the same speed as your test.
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Re: BB Unit on on antweight

Post by Wigs »

Thanks EddieJ,

Very sensible suggestions indeed, I will tinker around with them and see what I can come up with.

Will try not to shoot myself whilst doing so!!

Really have appreciated all your help though.

Thanks again
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Re: BB Unit on on antweight

Post by Wigs »

It's alive!
Turns out the 'Return Switch' isn't relevant to firing at all.
The motor pulls back and just releases after a certain distance. All mechanical.
Just added the ESC as advised and off it goes :)

One again many thanks EddieJ, if I ever get good at this stuff then I can hopefully return the favor someday.

All the best and good luck on all your builds
Adam

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Re: BB Unit on on antweight

Post by EddieJ »

Nice going! Now you make me want to install these in my car, to deter tail-gaiters!
Wigs wrote: Wed Feb 24, 2021 8:22 am One again many thanks EddieJ, if I ever get good at this stuff then I can hopefully return the favor someday.
No probs, if you avoid shooting me with BBs at a future bot event - we can call it even ;)
Good luck with the rest of the build
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