PART 2. Assembling The ATRC
First off if soldering circuits together really isn’t your thing and you really want to rid yourself of the track recoil then I’d suggest buying a commercially available module. Alternatively, the ATRC can be purchased from RC Tanks Australia Online Shop . Please allow a 5 day build time between ordering and dispatch.
The preparation of the RX-18 as described above will need to be completed for these modules to work so there is no skipping Part 1.
The Circuit
Parts List
To assemble the basic ATRC you will need:
1 x 5 volt DPDT relay
1 x FET BS170 OR 2N 7000
1 x 1uF Electrolytic Capacitor
1 x 100 ohm Resistor
1 x 270K Resistor
2 x 1N4148 Diodes
2 x 2 Pin Screw Terminals
1 x Pre-Printed PCB (as used for prototypes/experiments…)
With the exception of the relay you can get all of these components locally from Jaycar. The relay is available from RS Components.
http://australia.rs-online.com/web/sear ... 3&x=23&y=9Step 1. Cut Down the PCB
To make a nice small circuit cut down your PCB to a size of at least 12 x 9 holes. If you think you could make a mistake start with a slightly larger board like I have done here. If all goes right it can be trimmed down at the end.
Step 2. Solder the Relay & Screw Terminals in Place.
Place and solder the relay and screw terminals at one end of the board as shown below.
The next few steps are a little tricky and depend on your particular PCB. Make sure that all of the screw terminals (white circles) & relay terminals (red circles) are isolated. This will involve using a sharp hobby knife to cut away and of the intervening copper traces. Also clear any traces from between the two contacts of the relay coil
Step 3 Connect the Screw and Relay Terminals
Using the pictures below as a guide connect the relay and screw terminals as shown. Make the connections with short pieces of insulated wire.
Note the top terminals of the relay are isolated (nothing connects to them). Next up solder a diode across the relay coil terminals (Those at the bottom). The ‘+’ supply will contact the left terminal so the band on the diode will be towards this terminal.
Step 3. Solder the Remaining Components in Place
You will need to refer to the circuit diagram to help you with this step. Since everyone’s boards will be different you will need you own judgment on how best to arrange the remaining components. Further the pinout arrangement of the BS170 and 2N 7000 FETs are opposite. The BS170 is D G S flat side up, left to right. The 2N7000 is S G D flat side up, left to right. The FET I have used below is a 2N 7000. Also shown below is the connection for the green signal wire.
All that is left is to connect the power supply leads and trim the board. The picture below show the basic routes of the circuit, all of the leads attached and the board trimmed.
Same again only in diagrammatic form.
Step 4. Insulate & Terminate
It would probably be best to insulate the ATRC by either wrapping in insulation tape (cheap) or covering with shrink wrap (expensive). The three outgoing wires need to be terminated in a corresponding 3 Pin plug to that on your RX-18 board. (Note: The extra pair of red & black wires shown on the circuit below are for one of the modifications of this circuit that I’ll talk about later.)
Connection of the ATRC to the tank motors involves cutting both red wires that go from the RX-18 to the motors. The cut ends of the red wires are connected to the ATRC as shown below.
Step 5. TEST
Now it's time to test that all your hard soldering work has paid off. Connect your ATRC to your modified RX-18 and then connect up all the wires inside your tank to the RX board. Snip the red wires going to the motors and connect them to the ATRC as shown above. Turn everything on, start up your tank and when it has fully started up press the 'K' button. If all goes according to plan the gun will fire, there will be the cannon sound and flash (if you've got one) but the tank will remain still.
NEXT UP ... Modifications to the ATRC.
The more I look at this circuit the more possibilities open up. Firstly, with the addition of a single resistor we can use this circuit to trigger the LED flash circuit described earlier. Secondly, we need not have the tank do nothing when the gun is fired. The circuit above is probably best for tanks with rotating turrets but for the Stugs, Jadgpanzers, Brummbars, Sturmtigers... where the gun is ALWAYS forwards we can possibly alter the recoil action to be more realistic. I am currently working on this idea so the next post could be a while off. I assume that when a tank stops there will be a small amount of slack in the tracks so that when the gun fires the tank is infact moved backwards to the extent of this 'slack'. Combined with the tank's suspension there would be a slight back and forwards movement of the tank chassis when the gun fires. This may not be true but certainly in any WWII footage of tanks firing that I have seen there is movement of the chassis when the gun is fired. The emphasis here is 'SLIGHT' the current H/L action is far too wild. My first idea is to only allow a very small amount of backwards movement to the motors only. This should simulate the tank rocking back only on what slack there is in the tracks. I am hoping that this will result in a down and back action on the suspension which will then every so slightly produce the appearance to the tank rocking forwards. We shall see......
