JSB Rocketry

Click here to edit subtitle

RRT1 (Rocket Recovery Timer 1)

Here is the RRT1. It was our first flight computer that we at JSB Rocketry Developed.


The RRT 1 was designed to be as simple and as lightweight as possible for the user to deploy a parachute on a water rocket. The Timer is based around the Picaxe 08M2 Microcontroller and can use up to 6 Volts; we tend to uses a single cell, 3.7 volt Lipo batteries. It simply controls the timing and positioning of a Servo Motors movement. The timing and positioning of the Servo can be changed via the editing of the firmware. Please be aware that the user needs to have a good level of understanding of BASIC programming should they want to edit the settings, though any obvious changes are explained below, such as changing the Servo Positioning. The timer is sold with a pre-set delay of 3 seconds, and a pre-set arm delay of 10 seconds.

General Operation 

  • Firstly turn on the timer using the Switch; the servo will go to the pre-set position.
  • The Red is the poweR LED and the Green is the ARM LED meaning that the rocket is ready to Go. The Green LED will come on after 30 seconds indicating that the rocket is ready for launch.
  • The timer can be triggered in many ways, but comes with a break wire function that when broken, will begin the timer.
  • After the set delay (default of 3 seconds). The servo Motor will move 60 degrees.
  • Then simply turn of the Timer, to reset it.

How do I change the Firmware!!??

  • Open the ‘Picaxe Programming Editor’ from the CD provided.
  • Once in the Editor, open the file named: ‘RRT1.bas’. This can also be found on the disk.
  • Once you have made the desired changes to the program, plug in the RRT1 to the computer via the Programming socket, and the USB. Some of the changes you can make are explained further below.
  • Make sure the Servo and the Trigger are unplugged from the RRT1.
  • Power up the RRT1.
  • Click ‘Download’ in the editor, the Power LED will go off indicating that the Program is being downloaded to the Picaxe.
  • When it has downloaded, press enter, and power off the RRT1.
  • Unplug the programming socket from the RRT1, and you can now use the RRT1 with the new settings.

Changing the trigger method:

There is a number of ways the timer can be triggered, when choosing the trigger option, your plug it into the Trigger output located next to the battery input. Any trigger option can be used as long as it switches on or off. Edit the firmware according to this.

  • Break-wire
    • This is default for the product and is a simple if input off, then begin the countdown.
  • G-Switch
    • This requires you to edit the firmware, so that if input is on then start the countdown, you can attach the G-Switch to a set of RC wires that plug into the trigger contacts.
  • Mercury Switch (Burnout)
    • This requires you to edit the firmware, so that if input is on, however you will have to think that this will happen differently depending on the nozzle size of the rocket and the fuel (Foam rockets don’t have a burnout).

Changing the input status:


Here are the steps to changing the firmware:

  • Open the file named ‘RRT1.bas’ in the ‘Picaxe Programming Editor’ (please read the article at the top on how to edit the settings via the firmware, if you don’t have this program).
  • Scroll down to the part, of the code labelled below:

  • Change this value from ‘on’ to ‘off’ or vice versa.
  • Download the program to your RRT1.

Servo Positioning:


Here are the steps to controlling the Starting and Ending Servo positioning:

  • Open the file named ‘RRT1.bas’ in the ‘Picaxe Programming Editor’ (please read the article at the top on how to edit the settings via the firmware, if you don’t have this program).
  • Scroll down to the part, of the code labelled below:

  • There are 3 servo positions that can be changed, the starting position, the deployed position and the reset position (this is usually the same as the starting position). Make sure you change both values highlighted.
  • Change these  positions to where you like, use the diagram below to find out the number you put into the program depending on the position you want to move it to.

  • Download the program to your RRT1.

Changing the time Delay:


Here are the steps to controlling the ARM Delay time and or the Deployment Delay:

  • Open the file named ‘RRT1.bas’ in the ‘Picaxe Programming Editor’ (please read the article at the top on how to edit the settings via the firmware, if you don’t have this program).
  • Scroll down to the part, of the code labelled below:

  • Here are 3 time delays you can change, the ARM time, the delay time and the reset time.  The arm time is the time once turned on that the rocket can be launched. The delay time is the time until (once launch is detected) the servo moves. The reset time is the amount of time until the servo moves back to the starting position.
  • Once all changes have been made you can then download the new program to the RRT1 via the socket.

RRT1.2 (Rocket Recovery Timer 1.2)

Here is the RRT1.2. It was our second flight computer that we at JSB Rocketry Developed. It differs to the RRT1, because it doesn't' have a programming socket which means a it is more compact and light weight than the RRT1 but means that you have to take out the PIC when you want to change the firmware and put into a PIC programmer. The RRT1.2 is designed to be triggered primarily by a G-Switch. (not added in picture). This would be located next to the battery contacts. This is set up the night before the launch day with all the various settings for that particular rocket. Because the settings cannot be changed easily, we tend to use this as a backup system.


The RRT 1.2 was designed to be as simple and as lightweight as possible for the user to deploy a parachute on a water rocket. The Timer is based around the Picaxe 08M2 Microcontroller and can use up to 6 Volts; we tend to uses a single cell, 3.7 volt Lipo batteries. It simply controls the timing and positioning of a Servo Motors movement. The timing and positing of the Servo can be changed via the editing of the firmware. Please be aware that the user needs to have a good level of understanding of BASIC programming should they want to edit the settings, though any obvious changes are explained below, such as changing the Servo Positioning. The timer is sold with a pre-set delay of 3 seconds, and a pre-set arm delay of 10 seconds.


The settings for the RRT1.2 are almost exactly the same as RRT1.

Copyright © 2016 JSB Rocketry