#606 Sherman Firefly
Practicing finishing techniques on the Airfix 1:72 Sherman Firefly, then animating the turret with some ATtiny85 magic.
Here’s a demo..
I started the kit as a quick build to practice some weathering techniques (it is great for that) but then .. scope creep: animate the turret!
The Sherman Firefly Vc Airfix | No. A02341 | 1:72 is a nice little weekender - can be built in a few hours (depending on options chosen) and then spend as long as one likes finishing it;-)
I’m going to base the finish around scheme A from the kit - but without the unconfirmed black camo pattern. I’ll be using this kit as a “finishing techniques” test subject, so everything after the initial base coat will start to go its own way!
I am using Uncle Night Shift build series on the Char B1 bis as a perfect tutorial for the techniques I’ll be trying/learning here.
I’m using the Vallejo Model Color equivalents:
|155||70.887 US Olive Drab|
|53||70.863 Gunmetal Grey|
|110||70.875 Beige Brown|
I kept the build as simple as possible and went with the pre-molded tracks instead of the link-and-length option also included in the kit. This saves alot of time in the build - interested to see if they hold up to final scrutiny.
Primed in black so I don’t need to worry too much about unpainted nooks and crannies.
Made some progress on the finishing - base coat, some color modulation by mixing degrees of 70.917 Beige, 70.953 Flat Yellow and/or 70.989 Sky Grey.
Panel line highlighting with Tamiya Black Panel Line Accent Color.
ready for next round of effects - some oils, dust and chipping
Time for some Animation!
The weathering is going well, but now I’m thinking: how about an animated turret?
To be packed inside the body, with only a 5V power supply (through the bottom of the hull):
- ATtiny85 microcontroller, programmed with the Firefly sketch
- an electret microphone and TL072 opamp to amplify the incoming sound
- a resistor/diode pair, used to set the sound threshold voltage to around 0.4V (an input sound above that level will trigger the animation)
- a “firing pin” GPIO out - am still thinking about finding/making a suitable cannonfire sound effect, however for now it just blinks an LED for diagnostic purposes
- a Micro Linear Servo GS-1502, used to rotate the turret
Testing the circuit on a breadboard:
About the Program
The ATtniy85 is configured to run at 8MHz, and programmed with the Firefly sketch. The sketch:
- sets up an interrupt handler on the analog comparator:
- when voltage in from the electret microphone goes above the diode-regulated reference voltage of about 0.4V, it triggers the ANA_COMP_vect
- ANA_COMP_vect sets a “triggered” flag
- the main look checks for the “triggered” flag, an initiates the animation if fired.
- the animate traverses the turret by driving a linear servo using the SoftwareServo library
- it provides some “realistic” behaviour by stepping through a series of animation sequences
- the animations sequences basically define a series of waypoints (degrees of arc) and how fast to traverse to the waypoint (in degrees per increment)
- it could randomise the animation but I haven’t done that yet
Animated Turret Construction
After confirming the circuit on a breadboard, I transfered to a small piece of protoboard:
And inserted into the hull. the power connection is provided by two pins that poke through the bottom of the hull. Since the circuit runs fine on 5V, I’m using a USB adapter for power over USB cable.
Here’s an initial demo, before building a base..
A Vignette Base
Laying down the basics on an old ceramic tile. Power connector pin built-in, with USB micro connector at the rear of the hillock:
Finished? I could do with some more foliage but coming up short on materials at the moment.
Here’s a demo of it on the base..
Credits and References
- this project on scalemates
[Sherman Firefly Vc Airfix No. A02341 1:72](https://www.scalemates.com/kits/airfix-a02341-sherman-firefly-vc–1260489) - scalemates
- A02341 Sherman Firefly - airfix page
- Sherman Firefly - wikipedia
- The Firefly VC - theshermantank.com
- Sherman Firefly (Osprey New Vanguard #141) by David Fletcher, Tony Bryan (Illustrations)
- Building and Finishing the Char B1 bis - Uncle Night Shift
- TL072 datasheet
- ATtiny85 datasheet
- Micro Linear Servo GS-1502