I'm modifying a toy gun for a project.
The gun has a trigger and a cock on it. Both are connected to electronic switches.
I want to modify the gun so that when the trigger is pulled, an output is pulsed. Regardless of how long the trigger is held, I want the pulse to last the same amount of time (500mS)
I want the pulse circuit to reset when the gun is cocked.
This way, I can simulate a manual gun with an electronic output.
I was going to use a 555 circuit but I ran into a hang-up. In most circuits that I found, you can hold down the trigger and maintain a high output on the circuit. I was considering using a couple of 555's that are interlocked.
The first would fire the trigger, the second would shut it off on a time delay. Then the circuit could get reset when the gun is cocked. Has anybody done something similar?
The transistors implement a holding circuit. When you push the trigger, the circuit powers up and stays powered until you press the cock-switch. C1 and and R4 implements a crude timer. When the power goes up, C1 starts to build charge and voltage between C1 and R4 drops and eventually pulls the 555's reset pin below 0.7V. The actual C1/R4 values depend on the Vcc. Choose the RC values so that it takes a litle longer that 500ms before reset goes below 0.7V. For example, If Vcc is 5V, C1 needs to charge to 4.3V (=5V - 0.7V). 15K and 22uF gives you about 650 ms before reset goes down. Use RC time calculator bowdenshobbycircuits.info - bowdenshobbycircuits Resources and Information. to find suitable values.
When the reset pin is low, you cannot fire again until you cock the gun. When you press the cock-switch, the power goes down and C1 discharges through R5, and the gun is ready to fire again.
If the pulse time doesn't need to be very accurate (allow some tens of ms tolerance), you can probably modify the circuit so that you don't even need the 555 at all.
Please note that I haven't tested the circuit so I can't promise that it really works.
