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Poor Man's Fire select circuit

 
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Poor Man's Fire select circuit
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Minky
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Joined: 16 Oct 2016
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Post Poor Man's Fire select circuit  Reply with quote
.. An adventure with Live and Dead centre RS pusher control!!

Please see the circuit I've been thinking about and throw me ideas, constructive criticism, and a bone.
The concept is to run normally on a mid range ROF with a pusher motor nerfed by switching diodes using the standard live centre pusher control but be able to to switch out the diodes and switch to dead centre pusher control for full throttle ROF.
Can anyone see any issues with it?





EDIT:
Boff sniffed the circuit from several directions, took some seemingly unrelated lint off the floor and dropped it,  watching it's swirly progress to the floor and pronounced, 'there's something wrong with the motor braking.. on Discord.  Looking carefully I think I've got the leads onto the CC switch the wrong way around,  assuming the pusher activates the switch on return/close to the pusher mech.  Anyone else think I'm on the right track?

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If there was any other way of doing this without being the biggest damn hero you have ever met..  I'd still do this.
Tue Jan 17, 2017 10:59 pm View user's profile Send private message
SSGT
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Joined: 12 Jan 2013
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Post Reply with quote
There are a couple of issues. First off is cycle control, however you can fix that by switching the connections at 2 and 3. As it is the DPDT relay is actually redundant and you can simplify the circuit down to just a SPDT relay or even a SPDT switch (since high current SPDT switches are easier to come by than DPDT switches).

There is a fundamental issue though that is that power to the normally closed contact of the cycle control switch is always the full 11.1V supply voltage. This means that when you release the main trigger, and the cycle control switch is in it's normally closed position (i.e. the pusher mechanism is extended or, at the least, isn't fully docked), the motor will receive full pack supply voltage and speed up. This means that when the pusher does fully retract, and the cycle control switch does eventually open, the motor will likely be spinning too fast to come to come to a complete stop in time before it moves the pusher off the switch resulting in runaway firing (unless of course the braking torque of the motor is enough to bring it to a stop from full speed anyway, at which point there's no need to switch to a dead-centre circuit at the higher RoF in the first place - this will depend on the pusher motor you use). Unless you put 3 diodes before the NC pin of the cycle control switch (or instead connect the feed from the cycle control switch above the bottom diode in the diode train and accept that the motor will spin slightly faster when retracting after releasing the trigger - you can't connect it below all of the diodes otherwise you'll always have a live-centre circuit) you'd need to use a DPDT switch or relay as per this diagram:


(Click to enlarge)

I'm not sure if there's a simpler way to do this but, if there is, my brain is too tired to see it.

Note: In these modified diagrams I've also swapped over the numbering for the cycle control switch so that, for consistency, pin 3 is "NC" for all switches (it was easier than redoing the connections to the cycle control switch) - the arrow signifies that it's being held in it's "NO" position by the docked pusher at rest.

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Wed Jan 18, 2017 2:18 am View user's profile Send private message
Minky
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Joined: 16 Oct 2016
Posts: 305
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Post Reply with quote
Thanks SSGT. Food for thought. Back to the circuit drawing board. I'm probably going to be tweaking it a lot as I go on so I'll use this thread for amendments.



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Wed Jan 18, 2017 7:08 am View user's profile Send private message
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