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Rapidstrike pusher-box switch: area of "dwell"?

 
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Rapidstrike pusher-box switch: area of "dwell"?
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NscrupulousModefiler
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Joined: 18 Jul 2016
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Post Rapidstrike pusher-box switch: area of "dwell"?  Reply with quote
Hi team, down to the sharp and pointy end of the Hushpuppy build. We've monstered a RS pusher-box into the back end but of course the switch-block has been left behind... so looking at alternatives to get a third microswitch lined up properly in there for a live or dead-centre wire-up.

The only other microswitch transplant I've seen up close was hardly surgical (sorry P13c30fch33s3...) and by the sounds of it wasn't easy to tweak. I'll be trying for something with a little more adjustment available:



Only rated to 10A, but it has a much lighter activation pressure than the 16A switches I'm using in the grip. This'll be fitted directly to the box using an L-shaped bracket cut from the RS's battery-tray housing, with both forwards/backwards and height adjustment available for fettling via lock-nuts. I'll fiddle more with the spring-arm angles once I get the thing closer to a working state.

What I really need to sus now is the switch-activation dwell-area in the pusher-arm's travel ie: assuming the switch is definitely activated when the arm is fully retracted, how far in advance of this point does the switch first get depressed when the arm is retracting? I've included a handy pic with mm scale if anyone can give me a bit of a pointer here. "Zero" is set at the leading edge of the flat part of the pusher-arm's switch-activation tab (the first part of the arm that will activate the switch). If anyone knows the specific switch activation pressure you can get away with in there too, that could be helpful later if I replace the switch.

I'm using FK180-3539's for all 3 motors - slightly slower but about as torque-y as Blade 180's and give about 8-9dps(?) on 2S.



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OldNoob
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Post Reply with quote
Your best bet is behind the pusher box if there is room, Alice has used that location successfully before. Seen here with scrub tier switch- Cherry DC2 is compact, reliable and high quality.


Switch lever is depressed by the cam shaped gear on the back of the pusher arm.

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Mon Apr 17, 2017 9:32 am View user's profile Send private message Send e-mail
NscrupulousModefiler
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Post Reply with quote
OldNoob wrote:
Your best bet is behind the pusher box


Thanks, that's a really cunning solution. I'll have to make do with the switches I have for the mo, but Cherrys and Omrons are definitely on the wish-list for later.

Either spot though the question's the same: for how long in the pusher arm's cycle does the switch need to be activated? Is it just at the absolute end (fully retracted), or does there need to be a bit of "dwell" time around this point so it stays activated longer?

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OldNoob
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Post Reply with quote
Switch needs to be closed when the pusher is retracted for the cycle control to work, the dwell is provided by the back of the cam in this instance and the length of the actuator in the stock set up, there isn't a fixed period the switch needs to be closed. As long as it's closed with the pusher back then it will retract if you wire centre live or dead centre 3 switch. Omrons are totally unnecessary IMO, they are large, ungainly switches which you don't need. You can run the rev off a stock switch with MOSFET on the flywheel circuit and the pusher will never melt a DC2. I have seen them take 60A burst with no damage.

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Mon Apr 17, 2017 10:55 am View user's profile Send private message Send e-mail
NscrupulousModefiler
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Joined: 18 Jul 2016
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Post Reply with quote
OldNoob wrote:
...dwell is provided by the back of the cam in this instance


Cheers, this looks promising!

As it was, it was relatively straight-forward fitting full-size microswitches into the Strongarm grip for the triggers so didn't have to resort to any of that new-fangled MOSFET witchcraft. Call me a Luddite but I'm trying to keep the electrics as simple to trouble-shoot as I can in this build. Gotta leave room for improvement in the next one Wink

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Meishel wrote: Because "spin = cock". Some people love cock, don't judge.
Mon Apr 17, 2017 11:36 am View user's profile Send private message Visit poster's website
OldNoob
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Post Reply with quote
Mosfet is actually simpler since you only need control voltage in the grip. You can use thinner wire for all the control wiring, handy in smaller spaces. Cool fact- luddites weren't anti machinery, they were anti the inhuman treatment imposed on the machine opperators.

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Mon Apr 17, 2017 12:34 pm View user's profile Send private message Send e-mail
NscrupulousModefiler
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Joined: 18 Jul 2016
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Location: New Zealand



Post Reply with quote
OldNoob wrote:
handy in smaller spaces.


Don't get me wrong, I entirely see the benefits of MOSFET. Ironically, there's more usable space in the SA grip than there is in the rest of the entire Demolisher so the advantages didn't quite stack up enough. That, plus the microswitches provide the kind of immediate tactile feedback I wanted for the triggers all in one package without having to sort a special hold-down system for a stock switch... so I'd say both systems have their place.



Just looking at the space available on the back of that pusher-box and in the rear of the Demo shell... I could juuust make a full-sized microswitch work but wiring would be tight because of where the terminals lead out. I've got a DC2-ish sized one in the parts bin though (5A rated but with lighter again activation-pressure and terminals in the right places) so will try that out first. The tricky bit is still going to be dialing in the interface between the pusher-arm and the switch itself... if it does end up working I might bust my FET cherry FETtling that switch rather than replacing it with a genuine DC2 - we may yet end up with an unholy hybrid!


**Update** Video study of RS Pusher-Box's cam-action on micro-switches at rear of box:

Cam's movement is a bit more complex than I thought once the arm gets to "fully-retracted - there's a subtle in-and-out pulse as the drive dog passes through the apex of the arc. Any switch will have to be able to cope with this while remaining constantly actuated through that part of its travel. Looks do-able though. Full-size switch is hard to depress and may slow dart ROF. Smaller switch is only 5A rated and may need to be run with a MOSFET. Will post results in the HushPuppy build log.

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Meishel wrote: Because "spin = cock". Some people love cock, don't judge.
Wed Apr 19, 2017 1:02 pm View user's profile Send private message Visit poster's website
OldNoob
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Post Reply with quote
That 5A switch, if it has a lever actuator, will easily cope with pusher demands. I have mk1 BSUK switch kits in service with 5A switches that have had 2-3 years use on a variety of motors. Pushers rarely hit full stall, the gearing reduces motor loads and the gears break before the motor melts the switch. If you are worried simply put a 10A surface mounted blade fuse or a PTC on the +bve feed to the pusher box, its way easier than trying to make mosfets work for cycle control without a microcontroller.
I have never used the larger switches and in 3 years of top tier builds I have never had a rev trigger switch failure.

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Big_Poppa_Nerf wrote:

Boff whats the damage? I have spent over 3 times my Nerf budget this month already. Part of me is trying to be a responsible parent/husband/house owner. The other half is just says 'Ahhhh, Screw it!'.
Wed Apr 19, 2017 2:21 pm View user's profile Send private message Send e-mail
NscrupulousModefiler
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Joined: 18 Jul 2016
Posts: 44
Fav. Blaster: Rapnadomolisher
Location: New Zealand



Post Reply with quote
OldNoob wrote:
That 5A switch... will easily cope with pusher demands.


Cool - great to know. I was just going to plug it in anyway and if it did the job run it till it dropped, but a fuse is a VERY sensible addition. Even if this doesn't work so well for the pusher, it'll be a nifty switch to add some LED's in to the mix...

Thanks for all the advice Very Happy



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Greetings, Nerflings - we come in peace. Shoot to Thrill!

Meishel wrote: Because "spin = cock". Some people love cock, don't judge.
Wed Apr 19, 2017 9:35 pm View user's profile Send private message Visit poster's website
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