Friday, October 15, 2010

Mato Toys Tank Gun Modification

I purchased a few 'Tank Guns' from Mato Toys that some of the other Mech Warfare guys have used in the past. These are designed to be used in remote control model tanks which is apparently a popular hobby in some parts of the world.

This gun is much smaller and lighter then the airsoft gun I used on Second Amendment but its firing rate is extremely slow and disappointing. Another competitor at the Mech Warfare 2010 event had modified this same gun for a faster firing rate so I set out to discover the modification myself.

Here is the Tank Gun in all its cheapness glory. It is a slightly different form factor from Mato Toys product image but everything important seems to be the same.

Here I have removed the motor and one side of the gun's casing. We can see the inner workings of the gun. It works almost identical to the spring airsoft gun I used on Second Amendment. This gun uses a much smaller motor with many gear reductions to pull back the gun's spring/plunger.

Here is a picture of the modification I made. Normally the pinion is press fit onto the end of the motors shaft. I simply tapped the pinion down the base of the shaft. By repositioning the pinion like this it is simply bypassing two of the gear train's gear reductions increasing the guns firing rate.

The modification couldn't be simpler and was immediately obvious once I opened up the gun. Any negative long term affects on the motor or gear train is still unknown and requires some testing. Use at your own risk.

Tuesday, October 5, 2010

Prototyping an ATMEGA168 And Xbee Based Robot Controller

I have recently started work prototyping some ideas for a simple wireless remote controller for my robots.

Originally I was going to purchase some thumb joysticks available from Sparkfun to use for prototyping. Luckily I had the idea to use an old Playstation One Dual Shock controller that has been collecting dust for ages in my closet. It was kind enough to donate its innards for my purposes. Surprisingly the thumb sticks found inside the Playstaion controller are identical to the Sparkfun ones.

I went ahead and etched two breakout boards for the liberated thumb joysticks and have begun to interface them with one of my ATMEGA168 breakout boards. The software is really quite simplistic. It is just a matter of doing two analog to digital conversions for each axis of the joystick, forming a packet with the joystick readings and transmitting the packet out the micro's USART to the Xbee module.