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Tutorial - Nerf Maverick Aimtrak Mod with Solenoid Recoil
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trevski:

Fantastic work  :cheers:

I've had a couple of Happ recoil guns gathering dust while I tried to figure out how to do this very thing to them!



--- Quote from: captaincatalyst on January 02, 2011, 09:55:06 am ---
That's a good question.  The issue is that I'm dealing with 2 parallel circuits.  If I wired the Aimtrak and the Solenoid Control board circuit into the same pole on a switch, there would likely be unwanted side-effects.  I don't want the current from one circuit touching the other.  I'm powering the solenoid circuit with a separate power supply from the PC running the Aimtrak, so they don't share a common ground either.  I'm not an EE so I can't say exactly what would happen, but I'm not going to risk damage to the Aimtrak.  There are probably better solutions like a 2-pole microswitch, but a quick Google search doesn't bring up any results for anything like that.  :-\

Edit: This 2-pole switch might work... http://www.allelectronics.com/make-a-store/item/SMS-224/2-POLE-SNAP-ACTION-SWITCH//1.html

--- End quote ---

Would something like this solid state relay work for this application? ebay link

--- Code: ---DC/DC solid state relay,2A 4-60Vdc, with relay ON indicator light. Offer is for 2 off Solid State Relay.

Specifications

Contact Configuration    SPNO
Control Voltage    4 - 32Vdc
Isolation Voltage    4000Vrms
Load Voltage    4 → 60Vdc
Max On-state Voltage Drop At Rated A    1.6V
Maximum Input Current    8 mA
Maximum Load Current    2A
Maximum Load Voltage    60Vdc
Maximum Turn Off Time    1ms
Maximum Turn On Time    1ms
Minimum Load Current    0.01A
Off State Leakage Current    1.0mA
Package    Module
Surge Current Peak    8A

--- End code ---

My thought was that you could connect this after the microswitch in series to use the 5v(?) off the aimtrack to trigger the control circuit and hook the recoil board into the other side. That way no hacking of the microswitch required.

Alternatively perhaps something on the recoil board using an Led and an opto isolator?

I'd have a stab at it but my electronics skills are limited in the extreme!  :dizzy:


captaincatalyst:

--- Quote from: trevski on January 05, 2011, 04:41:40 am ---
Fantastic work  :cheers:

I've had a couple of Happ recoil guns gathering dust while I tried to figure out how to do this very thing to them!
...
Would something like this solid state relay work for this application? ebay link

--- Code: ---DC/DC solid state relay,2A 4-60Vdc, with relay ON indicator light. Offer is for 2 off Solid State Relay.

Specifications

Contact Configuration    SPNO
Control Voltage    4 - 32Vdc
Isolation Voltage    4000Vrms
Load Voltage    4 → 60Vdc
Max On-state Voltage Drop At Rated A    1.6V
Maximum Input Current    8 mA
Maximum Load Current    2A
Maximum Load Voltage    60Vdc
Maximum Turn Off Time    1ms
Maximum Turn On Time    1ms
Minimum Load Current    0.01A
Off State Leakage Current    1.0mA
Package    Module
Surge Current Peak    8A

--- End code ---

My thought was that you could connect this after the microswitch in series to use the 5v(?) off the aimtrack to trigger the control circuit and hook the recoil board into the other side. That way no hacking of the microswitch required.

Alternatively perhaps something on the recoil board using an Led and an opto isolator?

I'd have a stab at it but my electronics skills are limited in the extreme!  :dizzy:

--- End quote ---
A solid state relay could probably do the job.  I have never worked with one so I can't say how fast they are (probably depends on the specs).  I'm not familiar with opto isolators at all.  I've ordered some 2-pole switches which I think will be the easiest, most effective solution.  These guns are still a work in progress, so there will probably be some changes from the original design. 

I also decided the 1/2" braided nylon casing is too wide.  Since USB uses 4 wires and I need 4 wires for the solenoid and recoil board, I'm experimenting with using only a CATV cable (which has 8 wires) which will bundle everything into the same cord and I can use a 1/8" or 1/4" braided nylon casing.  I've ordered different sized casings for testing.  I might very well end up with issues related to the USB wires not being shielded from the solenoid wires, but I don't think they're shielded presently and everything works fine.  I'll report with updates once I have something to report.
drventure:
I've worked with both now, opto isolators and SSRs (to control ELWire segments).

They both seem to work equally well, though the SSRs are a little easier to wire up.

With the ELWire, I'm using them to switch AC voltage on and off very quickly to the ELWire segments, in the same way as Pulse width modulation is used to control the brightness of LED's when controlled by an LED Wiz.

That way, the LEDWiz can control ELWire segments exactly as if they were regular LEDs, complete with dimming, and pulsing special effects.
AndyWarne:

Excellent tutorial!

I can supply Aimtrak firmware with a pulse output enabled if needed.

I would not envisage any issues with common ground especially if the 25 volts was sourced from a power adaptor as this would have a non-grounded output.

I have been researching recoil for our own guns and I am finding it really needs custom solenoids as the resistance has to be low. Running a solenoid designed for 6 volts at 24 volts is fine as long as the duty cycle is low, which in this application it would be as it is only handling short pulses.
bkenobi:
This is an awesome project.  Nice work and excellent write up!

I would make one suggestion for people planning on following this document to make their own.  The OP's version has a very long trigger pull before the button is pressed.  I suspect that would get annoying after time since it will delay your shot due to the time it takes you to move your finger.  I would suggest doing something to make the button actuate sooner if it were my gun.  Should be fun either way though!
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