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Mechanics and Construction => Mechanics and Construction => Topic started by: usmchayward on February 01, 2018, 09:59:39 PM

Title: Assisted firing device
Post by: usmchayward on February 01, 2018, 09:59:39 PM
It is I, Benjamin Hayward. I am deployed down range in Afghanistan as a gunsmith. My project is making a device that attaches to a fire arm trigger allowing wounded individuals missing fingers, but with palm of hand intact to competitively shoot.

I've been learning, teaching myself about motors, robotics and the like, but it isn't enough. I need assistance. Here are the assets, what I've done, and what I need.

My goal is to move 20 ft. lbs. 4 inches. The trigger pull of a M9 9mm double action is 16.5 ft lbs.

Current Assets:
1. Waiting for delivery: I have a 3d printer: FlashForge 3D Printers, New Model: Finder
2. Spektrum S6250 servo w/ battery compartment
3. Waiting for delivery: SR310 DSMR 3 Ch Sport Receiver

How it works:
The shooter wears a fingerless glove with a strap. the strap holds the fire arm securely in the palm of hand. The device attaches to the trigger guard, and when activated, moves the trigger allowing the firearm to fire. This is accomplished when the shooter moves the thumb metacarpal, activating the motor. This servo currently moves in 2 directions, with a range limit.

What I need:
I need a simple solution where the handicapped shooter can press one button to activate the servo, and press the same button again to reset the servo and trigger. This is the part I am having trouble with.

Alternatives: I may be approaching this from the wrong direction. I have an idea, but I am in amateur hour. I've got almost $2,000 sunk into this project so far. I need help.

I would prefer to keep the discussion here, so I can get many minds assisting. Yes, I am looking for someone to tell me the answer to achieve my end state. As you can see, I'm not afraid to get my hands dirty, hands on, do some research. I do not need anyone to do this for me, I need guidance.
Title: Re: Assisted firing device
Post by: artbyrobot1 on February 03, 2018, 06:25:00 AM
You need to program a microcontroller (which is basically like a TINY computer built into a little chip on a tiny board) to receive the button press as an input signal, and to then instruct the servo to turn forward or reverse for trigger deployment or release.  Microcontrollers direct servos on where to turn and how far using PWM (pulse width modulation) signals.  They are the "brains" of ANY project including yours.  You can program microcontrollers by using a IDE (software program you write your code on) on your PC and then uploading the compiled code (after you type the code, the IDE converts it to machine language your microcontroller will understand) to the microcontroller via usb.  Your microcontroller will then make the decisions you told it to make with your code you wrote based on the conditions you set for it to do the actions you want it to do when those conditions are met - in your case turn a servo one way or another to a set position when a button is pressed.  You can look up tutorials on getting started with arduino - a popular microcontroller board that comes in different sizes and has a large following and lots of tutorials on youtube.  You can use a different microcontroller than arduino since there are tons to choose from, but Arduino is a great one or beginners and will work just fine for your project.  You don't need an arduino UNO, the most popular board, because it has WAY more functionality than you need.  You just need a Arduino attiny - you just need a single input and a single output (one analog input for reading button presses and one digital output for sending a PWM (pulse width modulation) signals to the servo motor.  You will simply program the microcontroller to turn one way when it gets a signal from the button indicating it was pressed and the controller will remember it is firing.  When the button is released it will await the 2nd press of the button.  The next time the button is pressed, it will release the trigger. It will know if the button is in the state of being pressed or released based on whether or not the button is completing the electrical circuit and the microcontroller, when the circuit is completed, will read that it is receiving 5 volts or w/e from the button.  When the button is not being pressed the circuit is not being completed and the microcontroller will be recieving 0v from the button circuit.  It reads the voltage it is getting from the analogue input pins on the microcontroller board.
Title: Re: Assisted firing device
Post by: artbyrobot1 on February 03, 2018, 06:30:12 AM
Note: I know I just gave a TON of info but I thought that would answer more questions you will have faster.  Long story short - your project is VERY easy for a beginner and will take you under a day and under $5 to get the rest of the parts you need.  Take a day to research Arduino and microcontrollers and starter projects like blinking a led, getting arduino to control a motor, getting arduino to work with a button, etc.  Then you will see this project is super easy for you.
Title: Re: Assisted firing device
Post by: usmchayward on February 03, 2018, 07:42:30 AM
Thank you so very much. I am gung ho, and will follow your advice. Someone suggest a $149 remote controller for an airplane, then take it apart. The Arduino attiny is a chip, that needs to be mounted on something. What is that something I mount it on? I do not see the usb input on the chip to upload the code. I poked around the Arduino site, but I did not get any definite answer.

I can teach myself how to program this. I can teach myself how to assemble this, and trial and error get it to work. Would you be willing to recommend exactly what the parts are? Here is the chipset I found. I need to mount it on something, the microcontroller you called it.

You are correct, I only need the servo to rotate in 2 directions, with the press of the button.


Benjamin Hayward
Title: Re: Assisted firing device
Post by: usmchayward on February 09, 2018, 04:26:20 AM
May anyone suggest a board the AT chip would go on to meet my needs?
Title: Re: Assisted firing device
Post by: freelectron on February 10, 2019, 09:09:24 AM
having a cheap chinese microcontroller firing a lethal weapon for a handicapped individual....what could go wrong.